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6 pages, 189 KiB

Open AccessEditorial

Special Issue: Smart Flow Control in Micro Scale

by Jin-yuan Qian, Junhui Zhang, Zan Wu and Bengt Sunden

Processes 2020, 8(5), 550; https://doi.org/10.3390/pr8050550 - 8 May 2020

Cited by 2 | Viewed by 1974

Abstract

Smart control processes have been proposed for many years, while for smart flow control—especially when “smart flow control” comes at the microscale—it turns out that many new innovations and enabling technologies are possible [...] Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

Research

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10 pages, 2494 KiB

Open AccessFeature PaperArticle

Theoretical and Experimental Studies of a Digital Flow Booster Operating at High Pressures and Flow Rates

by Chenggang Yuan, Vinrea Lim Mao Lung, Andrew Plummer and Min Pan

Processes 2020, 8(2), 211; https://doi.org/10.3390/pr8020211 - 10 Feb 2020

Cited by 6 | Viewed by 3203

Abstract

The switched inertance hydraulic converter (SIHC) is a new technology providing an alternative to conventional proportional or servo-valve-controlled systems in the area of fluid power. SIHCs can adjust or control flow and pressure by means of using digital control signals that do not [...] Read more.

The switched inertance hydraulic converter (SIHC) is a new technology providing an alternative to conventional proportional or servo-valve-controlled systems in the area of fluid power. SIHCs can adjust or control flow and pressure by means of using digital control signals that do not rely on throttling the flow and dissipation of power, and provide hydraulic systems with high-energy efficiency, flexible control, and insensitivity to contamination. In this article, the analytical models of an SIHC in a three-port flow-booster configuration were used and validated at high operating pressure, with the low- and high-pressure supplies of 30 and 90 bar and a high delivery flow rate of 21 L/min. The system dynamics, flow responses, and power consumption were investigated and theoretically and experimentally validated. Results were compared to previous results achieved using low operating pressures, where low- and high-pressure supplies were 20 and 30 bar, and the delivery flow rate was 7 L/min. We concluded that the analytical models could effectively predict SIHC performance, and higher operating pressures and flow rates could result in system uncertainties that need to be understood well. As high operating pressure or flow rate is a common requirement in hydraulic systems, this constitutes an important contribution to the development of newly switched inertance hydraulic converters and the improvement of fluid-power energy efficiency. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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18 pages, 4599 KiB

Open AccessArticle

Static Deformation-Compensation Method Based on Inclination-Sensor Feedback for Large-Scale Manipulators with Hydraulic Actuation

by Jianyong Qian, Qi Su, Fu Zhang, Yun Ma, Zifan Fang and Bing Xu

Processes 2020, 8(1), 81; https://doi.org/10.3390/pr8010081 - 8 Jan 2020

Cited by 4 | Viewed by 3054

Abstract

Modern large-scale manipulators with hydraulic actuation like mobile concrete pump manipulators are increasingly used in industrial, construction, and other fields. Due to the large span of these manipulators, the static deformation accumulation to the endpoint has seriously affected the precise control of the [...] Read more.

Modern large-scale manipulators with hydraulic actuation like mobile concrete pump manipulators are increasingly used in industrial, construction, and other fields. Due to the large span of these manipulators, the static deformation accumulation to the endpoint has seriously affected the precise control of the endpoint. In this paper, we propose a static deformation-compensation method based on inclination sensor feedback for large-scale manipulators to reduce the deviation of the endpoint. Compared with the finite element method, this method does not need to consider many boundary conditions that are uncertain for flexible manipulators in most situations. It has appropriate accuracy and is universal for large-scale manipulators of different sizes and working under different loads. Based on a 24m-3R mobile concrete pump manipulator, the parametric simulation is carried out. The reliability of the static deformation-compensation method is verified, and the error is analyzed. The validity of the static deformation-compensation method is verified by comparing the theoretical endpoint position with the actual endpoint position after static deformation compensation. The compensation error under different loads is obtained, and the universality of the compensation method for different loads is verified. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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16 pages, 9877 KiB

Open AccessArticle

Study on Oil Film Characteristics of Piston-Cylinder Pair of Ultra-High Pressure Axial Piston Pump

by Jin Zhang, Baolei Liu, Ruiqi LÜ, Qifan Yang and Qimei Dai

Processes 2020, 8(1), 68; https://doi.org/10.3390/pr8010068 - 3 Jan 2020

Cited by 25 | Viewed by 4335

Abstract

The piston-cylinder pair is the key friction pairs in the piston pump. Its performance determines the volume efficiency of piston pump. With the increase of load pressure, the leakage at the clearance of piston-cylinder pair will also increase. In order to reduce leakage, [...] Read more.

The piston-cylinder pair is the key friction pairs in the piston pump. Its performance determines the volume efficiency of piston pump. With the increase of load pressure, the leakage at the clearance of piston-cylinder pair will also increase. In order to reduce leakage, the clearance of the piston-cylinder pair of the ultra-high pressure piston pump is smaller than that of the medium-high pressure piston pump. In order to explore whether the piston will stuck in the narrow gap, it is necessary to study the oil film characteristics of the piston-cylinder pair under the condition of ultra-high pressure, so as to provide a theoretical basis for the optimal design of the piston-cylinder pair of ultra-high pressure axial piston pump. In this paper, an ultra-high pressure axial piston pump is taken as the research object, and its structural characteristics are analyzed. The mathematical model of the oil film thickness of the piston-cylinder pair is established by using the cosine theorem in the cross section of the piston. The finite volume method is used to discretize the Reynolds equation of the oil film of the piston-cylinder pair, and the over relaxation iteration method is used to solve the discrete equations, and the mathematical model of the oil film pressure of the piston-cylinder pair is obtained. The mathematical model of oil film thickness and pressure field of piston-cylinder pair is solved by programming. The dynamic change process of oil film thickness and pressure field of the plunger pair of the ultra-high pressure axial piston pump under the load of 20 MPa and 70 MPa is obtained. Under the two conditions, the thinnest area of the oil film reaches 3 μm and 2 μm dangerous area respectively; the oil film pressure reaches 20 MPa and 70 MPa respectively when the swashplate rotates 10° and continues to increase with the increase of swashplate rotation angle. When the rotation angle reaches 90°, the oil film pressure also reaches the maximum value, but there is no pressure spike phenomenon. The oil film pressure characteristics of ultra-high pressure axial piston pump under conventional and ultra-high pressure conditions were obtained by modification and experimentation. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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14 pages, 3387 KiB

Open AccessArticle

Numerical and Experimental Study on the Internal Flow of the Venturi Injector

by Hao Li, Hong Li, Xiuqiao Huang, Qibiao Han, Ye Yuan and Bin Qi

Processes 2020, 8(1), 64; https://doi.org/10.3390/pr8010064 - 2 Jan 2020

Cited by 19 | Viewed by 8081

Abstract

To study the appropriate numerical simulation methods for venturi injectors, including the investigation of the hydraulic performance, mixing process, and the flowing law of the two internal fluids, simulations and experiments were conducted in this study. In the simulations part, the cavitation model [...] Read more.

To study the appropriate numerical simulation methods for venturi injectors, including the investigation of the hydraulic performance, mixing process, and the flowing law of the two internal fluids, simulations and experiments were conducted in this study. In the simulations part, the cavitation model based on the standard k–ε turbulence and mixture models was added, after convergence of the calculations. The results revealed that the cavitation model has good agreement with the experiment. However, huge deviations occurred between the experimental results and the ones from the calculation when not considering the cavitation model after cavitation. Thus, it is inferred that the cavitation model can exactly predict the hydraulic performance of a venturi injector. In addition, the cavitation is a crucial factor affecting the hydraulic performance of a venturi injector. The cavitation can ensure the stability of the fertilizer absorption of the venturi injector and can realize the precise control of fertilization by the venturi injector, although it affects the flow stability and causes energy loss. Moreover, this study found that the mixing chamber and throat are the main areas of energy loss. Furthermore, we observed that the internal flow of the venturi injector results in the majority of mixing taking place at the diffusion and outlet sections. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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18 pages, 5856 KiB

Open AccessArticle

Research on the Dynamic Behaviors of the Jet System of Adaptive Fire-Fighting Monitors

by Xiaoming Yuan, Xuan Zhu, Chu Wang, Lijie Zhang and Yong Zhu

Processes 2019, 7(12), 952; https://doi.org/10.3390/pr7120952 - 12 Dec 2019

Cited by 6 | Viewed by 2926

Abstract

Based on the principles of nonlinear dynamics, a dynamic model of the jet system for adaptive fire-fighting monitors was established. The influence of nonlinear fluid spring force on the dynamic model was described by the Duffing equation. Results of numerical calculation indicate that [...] Read more.

Based on the principles of nonlinear dynamics, a dynamic model of the jet system for adaptive fire-fighting monitors was established. The influence of nonlinear fluid spring force on the dynamic model was described by the Duffing equation. Results of numerical calculation indicate that the nonlinear action of the fluid spring force leads to the nonlinear dynamic behavior of the jet system and fluid gas content, fluid pressure, excitation frequency, and excitation amplitude are the key factors affecting the dynamics of the jet system. When the excitation frequency is close to the natural frequency of the corresponding linear dynamic system, a sudden change in vibration amplitude occurs. The designed adaptive fire-fighting monitor had no multi-cycle, bifurcation, or chaos in the range of design parameters, which was consistent with the stroboscopic sampling results in the dynamic experiment of jet system. This research can provide a basis for the dynamic design and optimization of the adaptive fire-fighting monitor, and similar equipment. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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11 pages, 2425 KiB

Open AccessArticle

Numerical and Experimental Investigation of External Characteristics and Pressure Fluctuation of a Submersible Tubular Pumping System

by Yan Jin, Xiaoke He, Ye Zhang, Shanshan Zhou, Hongcheng Chen and Chao Liu

Processes 2019, 7(12), 949; https://doi.org/10.3390/pr7120949 - 12 Dec 2019

Cited by 12 | Viewed by 2522

Abstract

This paper presents an investigation of external flow characteristics and pressure fluctuation of a submersible tubular pumping system by using a combination of numerical simulation and experimental methods. The steady numerical simulation is used to predicted the hydraulic performance of the pumping system, [...] Read more.

This paper presents an investigation of external flow characteristics and pressure fluctuation of a submersible tubular pumping system by using a combination of numerical simulation and experimental methods. The steady numerical simulation is used to predicted the hydraulic performance of the pumping system, and the unsteady calculation is adopted to simulate the pressure fluctuation in different components of a submersible tubular pumping system. A test bench for a model test and pressure pulsation measurement is built to validate the numerical simulation. The results show that the performance curves of the calculation and experiment are in agreement with each other, especially in the high efficiency area, and the deviation is minor under small discharge and large discharge conditions. The pressure pulsation distributions of different flow components, such as the impeller outlet, middle of the guide vane, and guide vane outlet and bulb unit, are basically the same as the measurement data. For the monitoring points on the impeller and the wall of the guide vane especially, the main frequency and its amplitude matching degree are higher, while the pressure pulsation values on the wall of the bulb unit are quite different. The blade passing frequency and its multiples are important parameters for analysis of pressure pulsation; the strongest pressure fluctuation intensity appears in the impeller outlet, which is mainly caused by the rotor–stator interaction. The farther the measuring point from the impeller, the less the pressure pulsation is affected by the blade frequency. The frequency amplitudes decrease from the impeller exit to the bulb unit. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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19 pages, 6601 KiB

Open AccessArticle

Experimental and Numerical Study on Gas-Liquid Two-Phase Flow Behavior and Flow Induced Noise Characteristics of Radial Blade Pumps

by Qiaorui Si, Chunhao Shen, Asad Ali, Rui Cao, Jianping Yuan and Chuan Wang

Processes 2019, 7(12), 920; https://doi.org/10.3390/pr7120920 - 4 Dec 2019

Cited by 17 | Viewed by 3542

Abstract

Miniature drainage pumps with a radial blade are widely used in situations with critical constant head and low noise requests, but the stable operation state is often broken up by the entraining gas. In order to explore the internal flow characteristics under gas–liquid [...] Read more.

Miniature drainage pumps with a radial blade are widely used in situations with critical constant head and low noise requests, but the stable operation state is often broken up by the entraining gas. In order to explore the internal flow characteristics under gas–liquid two phase flow, pump performance and emitted noise measurements were processed under different working conditions. Three-dimensional numerical calculations based on the Euler inhomogeneous model and obtained experimental boundaries were carried out under different inlet air void fractions (IAVFs). A hybrid numerical method was proposed to obtain the flow-induced emitted noise characteristics. The results show there is little influence on pump characteristics when the IAVF is less than 1%. The pump head slope degradation was found to increase with air content. The bubbles adhere to the impeller hub on the blade’s suction side and spread to the periphery with a big IAVF, leading to unstable operation. It is obvious that vortices appear inside the impeller flow passage as IAVF reaches 6.5%. The two-phase flow pattern has a small effect on the characteristic frequency distribution of pressure fluctuation and emitted noise, but the corresponding pulsation intensity and noise level will increase. The study could provide some reference for low noise design of the drainage pump. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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21 pages, 19815 KiB

Open AccessArticle

Unsteady Flow Process in Mixed Waterjet Propulsion Pumps with Nozzle Based on Computational Fluid Dynamics

by Can Luo, Hao Liu, Li Cheng, Chuan Wang, Weixuan Jiao and Di Zhang

Processes 2019, 7(12), 910; https://doi.org/10.3390/pr7120910 - 3 Dec 2019

Cited by 6 | Viewed by 3252

Abstract

The unsteady flow process of waterjet pumps is related to the comprehensive performance and phenomenon of rotating stall and cavitation. To analyze the unsteady flow process on the unsteady condition, a computational domain containing nozzle, impeller, outlet guide vane (OGV), and shaft is [...] Read more.

The unsteady flow process of waterjet pumps is related to the comprehensive performance and phenomenon of rotating stall and cavitation. To analyze the unsteady flow process on the unsteady condition, a computational domain containing nozzle, impeller, outlet guide vane (OGV), and shaft is established. The surface vortex of the blade is unstable at the valley point of the hydraulic unstable zone. The vortex core and morphological characteristics of the vortex will change in a small range with time. The flow of the best efficiency point and the start point of the hydraulic unstable zone on each turbo surface is relatively stable. At the valley point of the hydraulic unstable zone, the flow and pressure fields are unstable, which causes the flow on each turbo surface to change with time. The hydraulic performance parameters are measured by establishing the double cycle test loop of a waterjet propulsion device compared with numerical simulated data. The verification results show that the numerical simulation method is credible. In this paper, the outcome is helpful to comprehend the unsteady flow mechanism in the pump of waterjet propulsion devices, and improve and benefit their design and comprehensive performance. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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16 pages, 3116 KiB

Open AccessFeature PaperArticle

Lattice Boltzmann Simulation on Droplet Flow through 3D Metal Foam

by Jian Zhang, Xinhai Yu and Shan-Tung Tu

Processes 2019, 7(12), 877; https://doi.org/10.3390/pr7120877 - 22 Nov 2019

Cited by 10 | Viewed by 4338

Abstract

The hydrodynamics of droplets passing through metal foam is investigated using the lattice Boltzmann method (LBM). The accurate 3D porous structure for the simulation is generated by X-ray micro-computed tomography. The simulated results are in good agreement with the experimental ones using high-speed [...] Read more.

The hydrodynamics of droplets passing through metal foam is investigated using the lattice Boltzmann method (LBM). The accurate 3D porous structure for the simulation is generated by X-ray micro-computed tomography. The simulated results are in good agreement with the experimental ones using high-speed video. The simulated results show that for droplets passing metal foam, there is a critical capillary number, Ca_c (around 0.061), above which the droplet continues to deform until it breaks up. The simulated results show that the capillary number, droplet size, pores diameter, and thickness of metal foam have the significant effect of droplets deforming and breaking up when the droplets pass through the metal foam. To avoid the calescence of two droplets at the inlet zone of the metal foam, the distance between droplets should be larger than three times the diameter of the droplet. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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11 pages, 5592 KiB

Open AccessArticle

Design, Simulation, and Experiment of an LTCC-Based Xenon Micro Flow Control Device for an Electric Propulsion System

by Chang-Bin Guan, Yan Shen, Zhao-Pu Yao, Zhao-Li Wang, Mei-Jie Zhang, Ke Nan and Huan-Huan Hui

Processes 2019, 7(11), 862; https://doi.org/10.3390/pr7110862 - 19 Nov 2019

Cited by 5 | Viewed by 4012

Abstract

A xenon micro flow control device (XMFCD) is the key component of a xenon feeding system, which controls the required micro flow xenon (µg/s–mg/s) to electric thrusters. Traditional XMFCDs usually have large volume and weight in order to achieve ultra-high fluid resistance and [...] Read more.

A xenon micro flow control device (XMFCD) is the key component of a xenon feeding system, which controls the required micro flow xenon (µg/s–mg/s) to electric thrusters. Traditional XMFCDs usually have large volume and weight in order to achieve ultra-high fluid resistance and have a long producing cycle and high processing cost. This paper proposes a miniaturized, easy-processing, and inexpensive XMFCD, which is fabricated by low-temperature co-fired ceramic (LTCC) technology. The design of the proposed XMFCD based on complex three-dimensional (3D) microfluidic channels is described, and its fabrication process based on LTCC is illustrated. The microfluidic channels of the fabricated single (9 mm diameter and 1.4 mm thickness) and dual (9 mm diameter and 2.4 mm thickness) XMFCDs were both checked by X-ray, which proved the LTCC method’s feasibility. A mathematical model of flow characteristics is established with the help of finite element analysis, and the model is validated by the experimental results of the single and dual XMFCDs. Based on the mathematical model, the influence of the structure parameters (diameter of orifice and width of the groove) on flow characteristics is investigated, which can guide the optimized design of the proposed XMFCD. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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11 pages, 5236 KiB

Open AccessArticle

Non-Structural Damage Verification of the High Pressure Pump Assembly Ball Valve in the Gasoline Direct Injection Vehicle System

by Liang Lu, Qilong Xue, Manyi Zhang, Liangliang Liu and Zhongyu Wu

Processes 2019, 7(11), 857; https://doi.org/10.3390/pr7110857 - 16 Nov 2019

Cited by 2 | Viewed by 3410

Abstract

The injection pressure of the gasoline direct injection vehicle is currently developing from the low pressure to the high pressure, and the increase of the injection pressure has brought various damage problems to the high pressure pump structure. These problems should be solved [...] Read more.

The injection pressure of the gasoline direct injection vehicle is currently developing from the low pressure to the high pressure, and the increase of the injection pressure has brought various damage problems to the high pressure pump structure. These problems should be solved urgently. In this paper, the damage problem of the high pressure pump unloading valve ball in a gasoline direct injection vehicle under high pressure conditions is studied. The theoretical calculation of the force of the pressure relief valve is carried out. Firstly, the equivalent friction coefficient is obtained by decoupling analysis of the statically indeterminate model. Based on this, a finite element model is established. The equivalent stress is obtained by numerical simulation. The equivalent stress is compared with the yield strength of the valve ball material to determine that the valve ball damage is a non-static damage. At the same time, the s-N curve of the probability of destruction of one-millionth of the material of the valve ball is given. Then, the fatigue numerical simulation is performed. A safety factor of 3.66 is obtained. In summary, the high pressure relief valve ball in the direct injection high pressure pump should not be a traditional structural damage under high pressure conditions. In the theoretical calculation, the tangential displacement and radial displacement of the ball are all on the micrometer level. It can be presumed that the surface damage of the valve ball is microscopic damage, such as fretting wear. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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16 pages, 6699 KiB

Open AccessArticle

Pressure Drop and Cavitation Analysis on Sleeve Regulating Valve

by Chang Qiu, Cheng-Hang Jiang, Han Zhang, Jia-Yi Wu and Zhi-Jiang Jin

Processes 2019, 7(11), 829; https://doi.org/10.3390/pr7110829 - 7 Nov 2019

Cited by 31 | Viewed by 4638

Abstract

The sleeve regulating valve is widely used in the pipeline systems of process industries to control fluid flow. When flowing through the sleeve regulating valve, the water is easy to reach cavitation because of the pressure drop in the partial region, which may [...] Read more.

The sleeve regulating valve is widely used in the pipeline systems of process industries to control fluid flow. When flowing through the sleeve regulating valve, the water is easy to reach cavitation because of the pressure drop in the partial region, which may cause serious damage to pipeline system. In this paper, the pressure drop and cavitation characteristics in the sleeve regulating valve for different pressure differences and valve core displacements are investigated using a multiphase cavitation model. The pressure drop, velocity and vapor volume distribution in the regulating valves are obtained and analyzed. The total vapor volumes are also predicted and compared. The results show that the decrease of the valve core displacement induces the enlargement of the vapor distribution region and the increase of the vapor density. The increase of the pressure difference induces a more serious cavitation. The pressure difference has a slight influence on the cavitation intensity and density in the regulating valve when the valve core displacement is 60 mm. With the decrease of the valve core displacement, the effects of the pressure difference on the cavitation intensity are enhanced. This work is of significance for the cavitation control of the sleeve regulating valves. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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21 pages, 5915 KiB

Open AccessArticle

Feature Extraction Method for Hydraulic Pump Fault Signal Based on Improved Empirical Wavelet Transform

by Zhi Zheng, Zhijun Wang, Yong Zhu, Shengnan Tang and Baozhong Wang

Processes 2019, 7(11), 824; https://doi.org/10.3390/pr7110824 - 6 Nov 2019

Cited by 16 | Viewed by 2350

Abstract

There are many interference components in Fourier amplitude spectrum of a contaminated fault signal, and thus the segment obtained based on the spectrum can lead to serious over-decomposition of empirical wavelet transform (EWT). Aiming to resolve the above problems, a novel method named [...] Read more.

There are many interference components in Fourier amplitude spectrum of a contaminated fault signal, and thus the segment obtained based on the spectrum can lead to serious over-decomposition of empirical wavelet transform (EWT). Aiming to resolve the above problems, a novel method named improved empirical wavelet transform (IEWT) is proposed. Because the power spectrum is less sensitive to the contaminated interference and manifests the presence of fault feature information, IEWT replaces the Fourier amplitude spectrum of EWT with power spectrum in segment acquirement, and threshold processing is also introduced to eliminate the bad influence on the acquirement, and thus the best decomposition result of IEWT can be obtained based on feature energy ratio (FER). The loose slipper fault signal of hydraulic pump is tested and verified. The result demonstrates that the proposed method is superior and can extract the fault feature information accurately. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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23 pages, 3816 KiB

Open AccessArticle

Natural Frequency Sensitivity Analysis of Fire-Fighting Jet System with Adaptive Gun Head

by Xiaoming Yuan, Xuan Zhu, Chu Wang, Lijie Zhang and Yong Zhu

Processes 2019, 7(11), 808; https://doi.org/10.3390/pr7110808 - 4 Nov 2019

Cited by 5 | Viewed by 2535

Abstract

The gun head is the end effector of the fire-fighting jet system. Compared with a traditional fixed gun head, an adaptive gun head has the advantages of having an adjustable nozzle opening, a wide applicable flow range, and a high fire-extinguishing efficiency. Thus, [...] Read more.

The gun head is the end effector of the fire-fighting jet system. Compared with a traditional fixed gun head, an adaptive gun head has the advantages of having an adjustable nozzle opening, a wide applicable flow range, and a high fire-extinguishing efficiency. Thus, the adaptive gun head can extinguish large fires quickly and efficiently. The fire-fighting jet system with an adaptive gun head has fluid-structure interaction and discrete-continuous coupling characteristics, and the influence of key design parameters on its natural frequencies needs to be determined by a sensitivity analysis. In this paper, the dynamic model and equations of the jet system were established based on the lumped parameter method, and the sensitivity calculation formulas of the natural frequency of the jet system to typical design parameters were derived. Natural frequencies and mode shapes of the jet system were determined based on a mode analysis. The variation law of the sensitivity of the natural frequency of the jet system to typical design parameters was revealed by the sensitivity analysis. The results show that the fluid mass inside the spray core within a certain initial gas content is the most important factor affecting the natural frequency of the jet system. There was only a 0.51% error between the value of the first-order natural frequency of the jet system determined by the modal experiment and the theoretical one, showing that good agreement with the first-order natural frequency of the jet system was found. This paper provides a theoretical basis for the dynamic optimization design of the adaptive gun head of the fire water monitor. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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13 pages, 6249 KiB

Open AccessArticle

Flow Characteristics and Stress Analysis of a Parallel Gate Valve

by Hui Wu, Jun-ye Li and Zhi-xin Gao

Processes 2019, 7(11), 803; https://doi.org/10.3390/pr7110803 - 3 Nov 2019

Cited by 9 | Viewed by 6990

Abstract

Gate valves have been widely used in the piping system and have attracted a lot of attention from researchers. In this paper, a wedge-type double disk parallel gate valve is chosen to be analyzed. The Reynolds number varying from 200 to 500,000, and [...] Read more.

Gate valves have been widely used in the piping system and have attracted a lot of attention from researchers. In this paper, a wedge-type double disk parallel gate valve is chosen to be analyzed. The Reynolds number varying from 200 to 500,000, and the valve opening degree varying from 20% to 100%, and the groove depth varying from 2.3 mm to 9 mm are chosen to investigate their effects on the flow and loss coefficients of the gate valve. The results show that the loss coefficient decreases and the flow coefficient increases with the increase of the Reynolds number and the valve opening degree, while with the increase of the groove depth, the loss coefficient barely changes, but the flow coefficient increases if the Reynolds number is larger than 10,000. In addition, the effects of the gaps between the disk and the limit stop on the stress distribution of the bolt are also investigated, and the results show that if the gaps are negative, high stress will act on the bolt at the contact position between the bolt and the limit stop. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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23 pages, 12223 KiB

Open AccessArticle

Numerical and Experimental Investigation on Radiated Noise Characteristics of the Multistage Centrifugal Pump

by Qiaorui Si, Biaobiao Wang, Jianping Yuan, Kaile Huang, Gang Lin and Chuan Wang

Processes 2019, 7(11), 793; https://doi.org/10.3390/pr7110793 - 2 Nov 2019

Cited by 22 | Viewed by 3946

Abstract

The radiated noise of the centrifugal pump acts as a disturbance in many applications. The radiated noise is closely related to the hydraulic design. The hydraulic parameters in the multistage pump are complex and the flow interaction among different stages is very strong, [...] Read more.

The radiated noise of the centrifugal pump acts as a disturbance in many applications. The radiated noise is closely related to the hydraulic design. The hydraulic parameters in the multistage pump are complex and the flow interaction among different stages is very strong, which in turn causes vibration and noise problems because of the strong hydraulic excitation. Hence, the mechanism of radiated noise and its relationship with hydraulics must be studied clearly. In order to find the regular pattern of the radiated noise at different operational conditions, a hybrid numerical method was proposed to obtain the flow-induced noise source based on Lighthill acoustic analogy theory, which divided the computational process into two parts: computational fluid dynamics (CFD) and computational acoustics (CA). The unsteady flow field was solved by detached eddy simulation using the commercial CFD code. The detailed flow information near the surface of the vane diffusers and the calculated flow-induced noise source was extracted as the hydraulic exciting force, both of which were used as acoustic sources for radiated noise simulation. The acoustic simulation employed the finite element method code to get the sound pressure level (SPL), frequency response, directivity, et al. results. The experiment was performed inside a semi-anechoic room with a closed type pump test rig. The pump performance and acoustic parameters of the multistage pump at different flow rates were gathered to verify the numerical methods. The computational and experimental results both reveal that the radiated noise exhibits a typical dipole characteristic behavior and its directivity varies with the flowrate. In addition, the sound pressure level (SPL) of the radiated noise fluctuates with the increment of the flow rate and the lowest SPL is generated at 0.8Q_d, which corresponds to the maximum efficiency working conditions. Furthermore, the experiment detects that the sound pressure level of the radiated noise in the multistage pump rises linearly with the increase of the rotational speed. Finally, an example of a low noise pump design is processed based on the obtained noise characteristics. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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13 pages, 3011 KiB

Open AccessArticle

Research on the Vertical Vibration Characteristics of Hydraulic Screw Down System of Rolling Mill under Nonlinear Friction

by Yongshun Zhang, Wanlu Jiang, Yong Zhu and Zhenbao Li

Processes 2019, 7(11), 792; https://doi.org/10.3390/pr7110792 - 2 Nov 2019

Cited by 8 | Viewed by 4150

Abstract

The rolling mill with hydraulic system is widely used in the production of strip steel. For the problem of vertical vibration of the rolling mill, the effects of different equivalent damping coefficient, leakage coefficient, and proportional coefficient of the controller on the hydraulic [...] Read more.

The rolling mill with hydraulic system is widely used in the production of strip steel. For the problem of vertical vibration of the rolling mill, the effects of different equivalent damping coefficient, leakage coefficient, and proportional coefficient of the controller on the hydraulic screw down system of the rolling mill are studied, respectively. First, a vertical vibration model of a hydraulic screw down system was established, considering the nonlinear friction and parameter uncertainty of the press cylinder. Second, the correlation between different equivalent damping coefficient, internal leakage coefficient, proportional coefficient, vertical vibration was analyzed. The simulation results show that, in the closed-loop state, when Proportional-Integral-Derivative (PID) controller parameters are fixed, due to the change of the equivalent damping coefficient and internal leakage coefficient, the system will have parameter uncertainty, which may lead to the failure of the PID controller and the vertical vibration of the system. This study has theoretical and practical significance for analyzing the mechanism of vertical vibration of the rolling mill. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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15 pages, 1408 KiB

Open AccessArticle

Absolute Stability Condition Derivation for Position Closed-Loop System in Hydraulic Automatic Gauge Control

by Yong Zhu, Shengnan Tang, Chuan Wang, Wanlu Jiang, Jianhua Zhao and Guangpeng Li

Processes 2019, 7(10), 766; https://doi.org/10.3390/pr7100766 - 18 Oct 2019

Cited by 27 | Viewed by 5377

Abstract

In the metallurgical industry, hydraulic automatic gauge control (HAGC) is a core mechanism for thickness control of plates used in the rolling process. The stability of the HAGC system’s kernel position closed-loop is key to ensuring a process with high precision, speed and [...] Read more.

In the metallurgical industry, hydraulic automatic gauge control (HAGC) is a core mechanism for thickness control of plates used in the rolling process. The stability of the HAGC system’s kernel position closed-loop is key to ensuring a process with high precision, speed and reliability. However, the closed-loop position control system is typically nonlinear, and its stability is affected by several factors, making it difficult to analyze instability in the system. This paper describes in detail the functioning of the position closed-loop system. A mathematical model of each component was established using theoretical analysis. An incremental transfer model of the position closed-loop system was also derived by studying the connections between each component. In addition, based on the derived information transfer relationship, a transfer block diagram of disturbance quantity of the system was established. Furthermore, the Popov frequency criterion method was introduced to ascertain its absolute stability. The results indicate that the absolute stability conditions of the position closed-loop system are derived in two situations: when spool displacement is positive or negative. This study lays a theoretical foundation for research on the instability mechanism of an HAGC system. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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16 pages, 5565 KiB

Open AccessFeature PaperArticle

Effects of a Dynamic Injection Flow Rate on Slug Generation in a Cross-Junction Square Microchannel

by Jin-yuan Qian, Min-rui Chen, Zan Wu, Zhi-jiang Jin and Bengt Sunden

Processes 2019, 7(10), 765; https://doi.org/10.3390/pr7100765 - 18 Oct 2019

Cited by 10 | Viewed by 3644

Abstract

The injection flow rates of two liquid phases play a decisive role in the slug generation of the liquid-liquid slug flow. However, most injection flow rates so far have been constant. In order to investigate the effects of dynamic injection flow rates on [...] Read more.

The injection flow rates of two liquid phases play a decisive role in the slug generation of the liquid-liquid slug flow. However, most injection flow rates so far have been constant. In order to investigate the effects of dynamic injection flow rates on the slug generation, including the slug size, separation distance and slug generation cycle time, a transient numerical model of a cross-junction square microchannel is established. The Volume of Fluid method is adopted to simulate the interface between two phases, i.e., butanol and water. The model is validated by experiments at a constant injection flow rate. Three different types of dynamic injection flow rates are applied for butanol, which are triangle, rectangular and sine wave flow rates. The dynamic injection flow rate cycles, which are related to the constant slug generation cycle time t₀, are investigated. Results show that when the cycle of the disperse phase flow rate is larger than t₀, the slug generation changes periodically, and the period is influenced by the cycle of the disperse phase flow rate. Among the three kinds of dynamic disperse flow rate, the rectangular wave influences the slug size most significantly, while the triangle wave influences the separation distance and the slug generation time more prominently. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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21 pages, 11405 KiB

Open AccessArticle

A Numerical Research on Vortex Street Flow Oscillation in the Double Flapper Nozzle Servo Valve

by Liang Lu, Shirang Long and Kangwu Zhu

Processes 2019, 7(10), 721; https://doi.org/10.3390/pr7100721 - 11 Oct 2019

Cited by 10 | Viewed by 3125

Abstract

The oscillating flow field of the double nozzle flapper servo valve pre-stage is numerically analyzed through Large Eddy Simulation (LES) turbulent modeling with the previous grid independence verification. The vortex street flow phenomenon can be observed when the flow passes through the nozzle [...] Read more.

The oscillating flow field of the double nozzle flapper servo valve pre-stage is numerically analyzed through Large Eddy Simulation (LES) turbulent modeling with the previous grid independence verification. The vortex street flow phenomenon can be observed when the flow passes through the nozzle flapper channel, the vortex alternating in each side produces the periodical flow oscillation. The structural and flow parameter effects on the oscillating flow are emphasized, and it could be determined that the pressure on the flapper is nearly proportional to the flow velocity and inversely proportional to the actual distance between the flapper and the nozzle. On the other hand, the main frequency of oscillation decreases with the velocity and increases with the distance between the nozzle flapper. The main stage movement is further considered with a User Defined Function (UDF), and it could be determined that the influences of the structural and flow parameters on the flow oscillation are rarely changed, but the main frequencies drop, generally. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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14 pages, 2421 KiB

Open AccessArticle

Bifurcation Characteristic Research on the Load Vertical Vibration of a Hydraulic Automatic Gauge Control System

by Yong Zhu, Shengnan Tang, Chuan Wang, Wanlu Jiang, Xiaoming Yuan and Yafei Lei

Processes 2019, 7(10), 718; https://doi.org/10.3390/pr7100718 - 10 Oct 2019

Cited by 31 | Viewed by 3379

Abstract

As the core control system of a rolling mill, the hydraulic automatic gauge control (HAGC) system is key to ensuring a rolling process with high speed, high precision and high reliability. However, a HAGC system is typically a mechanical-electric-hydraulic coupling system with nonlinear [...] Read more.

As the core control system of a rolling mill, the hydraulic automatic gauge control (HAGC) system is key to ensuring a rolling process with high speed, high precision and high reliability. However, a HAGC system is typically a mechanical-electric-hydraulic coupling system with nonlinear characteristics. The vertical vibration of the load easily occurs during the working process, which seriously affects the stability of the system and the causes are difficult to determine. In this work, the theory and method of nonlinear dynamics were employed. The load vertical vibration model of the HAGC system was established. Then, the multi-scale method was utilized to solve the obtained model, and the singularity theory was further applied to derive the transition set. Moreover, the research object of this article focused on some nonlinear factors such as excitation force, elastic force and damping force. The effects of the above feature parameters on bifurcation behavior were emphatically explored. The bifurcation characteristic of the load vertical vibration of the HAGC system was revealed. The research results indicate that the bifurcation curves in each sub-region, divided by the transition set, possess their own topological structure. The changes of the feature parameters, such as the nonlinear stiffness coefficient, liquid column height, nonlinear damping coefficient, and external excitation have an influence on the vibration amplitude of the HAGC system. By reasonably adjusting the nonlinear stiffness coefficient to effectively avoid the resonance region, the stability of the system will be facilitated. Furthermore, this is conducive to the system’s stability as it properly controls the size of the liquid column height of the hydraulic cylinder. The appropriate nonlinear damping coefficient can decrease the unstable area, which is beneficial to the stability of the system. However, large external excitation is not conducive to the stability of the system. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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18 pages, 7680 KiB

Open AccessArticle

A Fault Feature Extraction Method for the Fluid Pressure Signal of Hydraulic Pumps Based on Autogram

by Zhi Zheng, Xianze Li and Yong Zhu

Processes 2019, 7(10), 695; https://doi.org/10.3390/pr7100695 - 3 Oct 2019

Cited by 8 | Viewed by 2770

Abstract

Center spring wear faults in hydraulic pumps can cause fluid pressure fluctuations at the outlet, and the fault feature information on fluctuations is often contaminated by different types of fluid flow interferences. Aiming to resolve the above problems, a fluid pressure signal method [...] Read more.

Center spring wear faults in hydraulic pumps can cause fluid pressure fluctuations at the outlet, and the fault feature information on fluctuations is often contaminated by different types of fluid flow interferences. Aiming to resolve the above problems, a fluid pressure signal method for hydraulic pumps based on Autogram was applied to extract the fault feature information. Firstly, maximal overlap discrete wavelet packet transform (MODWPT) was adopted to decompose the contaminated fault pressure signal of center spring wear. Secondly, based on the squared envelope of each node, three kinds of kurtosis of unbiased autocorrelation (AC) were computed in order to describe the fault feature information comprehensively. These are known as standard Autogram, upper Autogram and lower Autogram. Then a node corresponding to the biggest kurtosis value was selected as a data source for further spectrum analysis. Lastly, the data source was processed by threshold values, and then the fault could be diagnosed based on the fluid pressure signal. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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23 pages, 11495 KiB

Open AccessArticle

Numerical Analysis of Two-Phase Flow in the Cavitation Process of a Waterjet Propulsion Pump System

by Weixuan Jiao, Li Cheng, Jing Xu and Chuan Wang

Processes 2019, 7(10), 690; https://doi.org/10.3390/pr7100690 - 2 Oct 2019

Cited by 21 | Viewed by 5078

Abstract

The waterjet propulsion system has been widely used in the military and civil fields because of its advantages of in terms of high efficiency and energy savings. In order to study the three-dimensional cavitation flow in the waterjet propulsion pump, the cavitation process [...] Read more.

The waterjet propulsion system has been widely used in the military and civil fields because of its advantages of in terms of high efficiency and energy savings. In order to study the three-dimensional cavitation flow in the waterjet propulsion pump, the cavitation process of the waterjet propulsion pump was simulated numerically using the Zwart–Gerber–Belamri cavitation model and the RNG (Renormalization Group) k-ε model. The simulation results of cavitation on the waterjet propulsion pump and pump system show that, in the initial stage of cavitation, vapors first collect on the leading edge of the suction surface of the blade near the rim of the impeller. As the total pressure at the impeller inlet decreases, the cavitation region expands toward the trailing edge and the vapor fraction volume gradually increases. In order to simulate the cavitation state of the waterjet propulsion pump under the actual working conditions, a numerical simulation of the entire waterjet propulsion pump system with inlet passage was carried out. After assembling the inlet passage, the flow pattern at the impeller inlet becomes uneven, leading to irregular changes in the cavitation region of the impeller. The potential danger regions of cavitation are the lip of inlet passage and the upper and lower connecting curved section of the inlet passage. The performance of waterjet propulsion pump system changes greatly when the net positive suction head available (NPSHa) value of the pump reaches the critical value. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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22 pages, 15194 KiB

Open AccessArticle

Numerical Analysis of the Diaphragm Valve Throttling Characteristics

by Yingnan Liu, Liang Lu and Kangwu Zhu

Processes 2019, 7(10), 671; https://doi.org/10.3390/pr7100671 - 28 Sep 2019

Cited by 7 | Viewed by 6391

Abstract

The throttling characteristics of the diaphragm valve are numerically studied in this paper. Firstly, the diaphragm deformation performance is analyzed by a finite element method, while the upper boundary morphology of the internal flow field under different valve openings was obtained. Then the [...] Read more.

The throttling characteristics of the diaphragm valve are numerically studied in this paper. Firstly, the diaphragm deformation performance is analyzed by a finite element method, while the upper boundary morphology of the internal flow field under different valve openings was obtained. Then the two-dimensional simulation of the weir diaphragm valve flow field is carried out in order to explore the optimal design of flow path profile. The study shows that the throttling characteristics can be improved by flatting the ridge side wall, widening the top of the ridge and gently flatting the internal protruding of the flow path. In addition, using the local grid encryption techniques based on velocity gradient adaptive and y⁺ adaptive can improve the accuracy of simulation results. Finally, a cavitation two-phase flow simulation is carried out. The results show that cavitation may occur below 50% opening of diaphragm valve in ultra-pure water system, which becomes more intense with the increase of inlet pressure and even leading to flow saturation on the micro-orifice state. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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16 pages, 6343 KiB

Open AccessArticle

Analysis of Air–Oil Flow and Heat Transfer inside a Grooved Rotating-Disk System

by Chunming Li, Wei Wu, Yin Liu, Chenhui Hu and Junjie Zhou

Processes 2019, 7(9), 632; https://doi.org/10.3390/pr7090632 - 18 Sep 2019

Cited by 5 | Viewed by 3849

Abstract

An investigation on the two-phase flow field inside a grooved rotating-disk system is presented by experiment and computational fluid dynamics numerical simulation. The grooved rotating-disk system consists of one stationary flat disk and one rotating grooved disk. A three-dimensional computational fluid dynamics model [...] Read more.

An investigation on the two-phase flow field inside a grooved rotating-disk system is presented by experiment and computational fluid dynamics numerical simulation. The grooved rotating-disk system consists of one stationary flat disk and one rotating grooved disk. A three-dimensional computational fluid dynamics model considering two-phase flow and heat transfer was utilized to simulate phase distributions and heat dissipation capability. Visualization tests were conducted to validate the flow patterns and the parametric effects on the flow field. The results indicate that the flow field of the grooved rotating-disk system was identified to be an air–oil flow. A stable interface between the continuous oil phase and the two-phase area could be formed and observed. The parametric analysis demonstrated that the inter moved outwards in the radial direction, and the average oil volume fraction over the whole flow field increased with smaller angular speed, more inlet mass flow of oil, or decreasing disk spacing. The local Nusselt number was remarkably affected by the oil volume fraction and the fluid flow speed distributions in this two-phase flow at different radial positions. Lastly, due to the change of phase volume fraction and fluid flow speed, the variation of the average Nusselt number over the whole flow field could be divided into three stages. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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18 pages, 4022 KiB

Open AccessArticle

Fault Diagnosis Method for Hydraulic Directional Valves Integrating PCA and XGBoost

by Yafei Lei, Wanlu Jiang, Anqi Jiang, Yong Zhu, Hongjie Niu and Sheng Zhang

Processes 2019, 7(9), 589; https://doi.org/10.3390/pr7090589 - 3 Sep 2019

Cited by 50 | Viewed by 4906

Abstract

A novel fault diagnosis method is proposed, depending on a cloud service, for the typical faults in the hydraulic directional valve. The method, based on the Machine Learning Service (MLS) HUAWEI CLOUD, achieves accurate diagnosis of hydraulic valve faults by combining both the [...] Read more.

A novel fault diagnosis method is proposed, depending on a cloud service, for the typical faults in the hydraulic directional valve. The method, based on the Machine Learning Service (MLS) HUAWEI CLOUD, achieves accurate diagnosis of hydraulic valve faults by combining both the advantages of Principal Component Analysis (PCA) in dimensionality reduction and the eXtreme Gradient Boosting (XGBoost) algorithm. First, to obtain the principal component feature set of the pressure signal, PCA was utilized to reduce the dimension of the measured inlet and outlet pressure signals of the hydraulic directional valve. Second, a machine learning sample was constructed by replacing the original fault set with the principal component feature set. Third, the MLS was employed to create an XGBoost model to diagnose valve faults. Lastly, based on model evaluation indicators such as precision, the recall rate, and the F1 score, a test set was used to compare the XGBoost model with the Classification And Regression Trees (CART) model and the Random Forests (RFs) model, respectively. The research results indicate that the proposed method can effectively identify valve faults in the hydraulic directional valve and have higher fault diagnosis accuracy. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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13 pages, 2223 KiB

Open AccessArticle

The Simulation of Vortex Structures Induced by Different Local Vibrations at the Wall in a Flat-Plate Laminar Boundary Layer

by Weidong Cao, Zhixiang Jia and Qiqi Zhang

Processes 2019, 7(9), 563; https://doi.org/10.3390/pr7090563 - 23 Aug 2019

Cited by 2 | Viewed by 2339

Abstract

The compact finite difference scheme on non-uniform meshes and the Fourier spectral hybrid method are used to directly simulate the evolution of vortex structures in a laminar boundary layer over a flat plate. To this end, two initial local vibration disturbances, namely, the [...] Read more.

The compact finite difference scheme on non-uniform meshes and the Fourier spectral hybrid method are used to directly simulate the evolution of vortex structures in a laminar boundary layer over a flat plate. To this end, two initial local vibration disturbances, namely, the positive–negative and the negative–positive models, at the wall were adopted. The numerical results show that the maximum amplitudes of vortex structures experience a process of linear growth and nonlinear rapid growth. The vertical disturbance velocity and mean flow shear and the derivative term of the stream-wise disturbance velocity and the span-wise disturbance velocity, are important factors for vortex structure development; the high- and low-speed stripe and the stream-wise vortex are consistent with structures seen in full turbulence. The maximum amplitude of the negative–positive model grows more quickly than that of the negative–positive model, and the detailed vortex structures are different for the two models. The mean flow profiles both become plump, which leads to the instability of the laminar boundary layer. The way in which the disturbance is generated with different local vibrations influences the dynamics of vortex structures in a laminar boundary layer. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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13 pages, 2750 KiB

Open AccessArticle

Near-Wall Flow Characteristics of a Centrifugal Impeller with Low Specific Speed

by Weidong Cao, Zhixiang Jia and Qiqi Zhang

Processes 2019, 7(8), 514; https://doi.org/10.3390/pr7080514 - 5 Aug 2019

Cited by 5 | Viewed by 3368

Abstract

In order to study the near-wall region flow characteristics in a low-specific-speed centrifugal impeller, based on ANSYS-CFX 15.0 software, Reynolds averaged Navier-Stokes (RANS) methods and renormalization group (RNG) k-ɛ turbulence model were used to simulate the whole flow field of a low specific [...] Read more.

In order to study the near-wall region flow characteristics in a low-specific-speed centrifugal impeller, based on ANSYS-CFX 15.0 software, Reynolds averaged Navier-Stokes (RANS) methods and renormalization group (RNG) k-ɛ turbulence model were used to simulate the whole flow field of a low specific speed centrifugal pump with five blades under different flow rates. Simulation results of external characteristics of the pump were in good agreement with experimental results. Profiles were set on the pressure side and suction side of impeller blades at the distances of 0.5 mm and 2 mm, respectively, to study the distributions of flow characteristics near the wall region of five groups of blades. The results show that the near-wall region flow characteristics of five groups of blades were similar, but the static pressure, relative velocity, cross flow velocity, and turbulent kinetic energy of profiles on the pressure side were quite different to those on the suction sides, and these characteristics also changed with the alternation of flow rate. As the flow rate was 13 m³/h or 20 m³/h, within the radius range of 40 to 50 mm, there was an extent of negative relative velocity of the profiles on the pressure side, and a counter-current happened not on the suction side, but on the pressure side in the low specific speed centrifugal impeller. The flow characteristics of profiles at the distances of 0.5 mm and 2 mm also showed a small difference. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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10 pages, 2212 KiB

Open AccessArticle

The Impact of Erythrocytes Injury on Blood Flow in Bionic Arteriole with Stenosis Segment

by Donghai Li, Guiling Li, Yuanyuan Chen, Jia Man, Qingyu Wu, Mingkui Zhang, Haosheng Chen and Yu Zhang

Processes 2019, 7(6), 372; https://doi.org/10.3390/pr7060372 - 14 Jun 2019

Cited by 2 | Viewed by 3438

Abstract

Ventricular assist device (VAD) implantation is an effective treatment for patients with end-stage heart failure. However, patients who undergo long-term application of VADs experience a series of VAD-related adverse effects including pump thrombosis, which is induced by rotate impeller-caused blood cell injury and [...] Read more.

Ventricular assist device (VAD) implantation is an effective treatment for patients with end-stage heart failure. However, patients who undergo long-term application of VADs experience a series of VAD-related adverse effects including pump thrombosis, which is induced by rotate impeller-caused blood cell injury and hemolysis. Blood cell trauma-related flow patterns are the key mechanism for understanding thrombus formation. In this study, we established a new method to evaluate the blood cell damage and investigate the real-time characteristics of blood flow patterns in vitro using rheometer and bionic microfluidic devices. The variation of plasma free hemoglobin (PFH) and lactic dehydrogenase (LDH) in the rheometer test showed that high shear stress was the main factor causing erythrocyte membrane injury, while the long-term exposure of high shear stress further aggravated this trauma. Following this rheometer test, the damaged erythrocytes were collected and injected into a bionic microfluidic device. The captured images of bionic microfluidic device tests showed that with the increase of shear stress suffered by the erythrocyte, the migration rate of damaged erythrocyte in bionic microchannel significantly decreased and, meanwhile, aggregation of erythrocyte was clearly observed. Our results indicate that mechanical shear stress caused by erythrocyte injury leads to thrombus formulation and adhesion in arterioles. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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14 pages, 7785 KiB

Open AccessArticle

Numerical Study of Pressure Fluctuation and Unsteady Flow in a Centrifugal Pump

by Ling Bai, Ling Zhou, Chen Han, Yong Zhu and Weidong Shi

Processes 2019, 7(6), 354; https://doi.org/10.3390/pr7060354 - 9 Jun 2019

Cited by 56 | Viewed by 4913

Abstract

A pump is one of the most important machines in the processes and flow systems. The operation of multistage centrifugal pumps could generate pressure fluctuations and instabilities that may be detrimental to the performance and integrity of the pump. In this paper, a [...] Read more.

A pump is one of the most important machines in the processes and flow systems. The operation of multistage centrifugal pumps could generate pressure fluctuations and instabilities that may be detrimental to the performance and integrity of the pump. In this paper, a numerical study of the influence of pressure fluctuations and unsteady flow patterns was undertaken in the pump flow channel of three configurations with different diffuser vane numbers. It was found that the amplitude of pressure fluctuation in the diffuser was increased gradually with the increase in number of diffuser vanes. The lower number of diffuser vanes was beneficial to obtain a weaker pressure fluctuation intensity. With the static pressure gradually increasing, the effects of impeller blade passing frequency attenuated gradually, and the effect of diffuser vanes was increased gradually. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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22 pages, 10742 KiB

Open AccessArticle

Numerical Study on the Gas-Water Two-Phase Flow in the Self-Priming Process of Self-Priming Centrifugal Pump

by Chuan Wang, Bo Hu, Yong Zhu, Xiuli Wang, Can Luo and Li Cheng

Processes 2019, 7(6), 330; https://doi.org/10.3390/pr7060330 - 1 Jun 2019

Cited by 48 | Viewed by 6835

Abstract

A self-priming centrifugal pump can be used in various areas such as agricultural irrigation, urban greening, and building water-supply. In order to simulate the gas-water two-phase flow in the self-priming process of a self-priming centrifugal pump, the unsteady numerical calculation of a typical [...] Read more.

A self-priming centrifugal pump can be used in various areas such as agricultural irrigation, urban greening, and building water-supply. In order to simulate the gas-water two-phase flow in the self-priming process of a self-priming centrifugal pump, the unsteady numerical calculation of a typical self-priming centrifugal pump was performed using the ANSYS Computational Fluid X (ANSYS CFX) software. It was found that the whole self-priming process of a self-priming pump can be divided into three stages: the initial self-priming stage, the middle self-priming stage, and the final self-priming stage. Moreover, the self-priming time of the initial and final self-priming stages accounts for a small percentage of the whole self-priming process, while the middle self-priming stage is the main stage in the self-priming process and further determines the length of the self-priming time. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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13 pages, 661 KiB

Open AccessArticle

A Simulation-Based Multi-Objective Optimization Design Method for Pump-Driven Electro-Hydrostatic Actuators

by Longxian Xue, Shuai Wu, Yuanzhi Xu and Dongli Ma

Processes 2019, 7(5), 274; https://doi.org/10.3390/pr7050274 - 9 May 2019

Cited by 16 | Viewed by 4997

Abstract

A pump-driven actuator, which usually called an electro-hydrostatic actuator (EHA), is widely used in aerospace and industrial applications. It is interesting to optimize both its static and dynamic performances, such as weight, energy consumption, rise time, and dynamic stiffness, in the design phase. [...] Read more.

A pump-driven actuator, which usually called an electro-hydrostatic actuator (EHA), is widely used in aerospace and industrial applications. It is interesting to optimize both its static and dynamic performances, such as weight, energy consumption, rise time, and dynamic stiffness, in the design phase. It is difficult to decide the parameters, due to the high number of objectives to be taken into consideration simultaneously. This paper proposes a simulation-based multi-objective optimization (MOO) design method for EHA with AMESim and a python script The model of an EHA driving a flight control surface is carried out by AMESim. The python script generates design parameters by using an intelligent search method and transfers them to the AMESim model. Then, the script can run a simulation of the AMESim model with a pre-set motion and load scenario of the control surface. The python script can also obtain the results when the simulation is finished, which can then be used to evaluate performance as the objective of optimization. There are four objectives considered in the present study, which are weight, energy consumption, rise time, and dynamic stiffness. The weight is predicted by the scaling law, based on the design parameters. The performances of dynamic response energy efficiency and dynamic stiffness are obtained by the simulation model. A multi-objective particle swarm optimization (MOPSO) algorithm is applied to search for the parameter solutions at the Pareto-front of the desired objectives. The optimization results of an EHA, based on the proposed methodology, are demonstrated. The results are very useful for engineers, to help determine the design parameters of the actuator in the design phase. The proposed method and platform are valuable in system design and optimization. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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12 pages, 3291 KiB

Open AccessArticle

A Numerical Analysis of Pressure Pulsation Characteristics Induced by Unsteady Blood Flow in a Bileaflet Mechanical Heart Valve

by Xiao-gang Xu, Tai-yu Liu, Cheng Li, Lu Zhu and Shu-xun Li

Processes 2019, 7(4), 232; https://doi.org/10.3390/pr7040232 - 24 Apr 2019

Cited by 12 | Viewed by 4447

Abstract

The leaflet vibration phenomenon in bileaflet mechanical heart valves (BMHVs) can cause complications such as hemolysis, leaflet damage, and valve fracture. One of the main reasons for leaflet vibration is the unsteady blood flow pressure pulsation induced by turbulent flow instabilities. In this [...] Read more.

The leaflet vibration phenomenon in bileaflet mechanical heart valves (BMHVs) can cause complications such as hemolysis, leaflet damage, and valve fracture. One of the main reasons for leaflet vibration is the unsteady blood flow pressure pulsation induced by turbulent flow instabilities. In this study, we performed numerical simulations of unsteady flow through a BMHV and observed pressure pulsation characteristics under different flow rates and leaflet fully opening angle conditions. The pressure pulsation coefficient and the low-Reynolds k-ω model in CFD (Computational Fluid Dynamics) software were employed to solve these problems. Results showed that the level of pressure pulsation was highly influenced by velocity distribution, and that the higher coefficient of pressure pulsation was associated with the lower flow velocity along the main flow direction. The influence of pressure pulsation near the trailing edges was much larger than the data obtained near the leading edges of the leaflets. In addition, considering the level of pressure pulsation and the flow uniformity, the recommended setting of leaflet fully opening angle was about 80°. Full article

(This article belongs to the Special Issue Smart Flow Control Processes in Micro Scale)

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