Confirmation on the effectiveness of rectangle-shaped flapper in reducing cavitation in flapper–nozzle pilot valve

Yang, Qingjun; Aung, Nay; Li, Songjing

doi:10.1016/j.enconman.2015.03.096

Cited by 37 publications

(24 citation statements)

References 19 publications

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“…A fixed-typed size function is used for the generation of the tetrahedral grids. The cells with the skewness value under 0.6 account for 98% in total 3D elements, and the maximum skewness value of the cells is about 0.75, suggesting the mesh quality is acceptable [13]. The grid independence analysis has been conducted.…”

Section: B Grid Mesh and Boundary Conditionsmentioning

confidence: 99%

“…Note that the cavitation in the flapper-nozzle servo valve could be intensified by reducing the outlet pressure. Thus, the outlet pressure for CFD modelling in this work is set as the gauge pressure to study the severe cavitation characteristics, as did in [12] and [13]. The symmetry-type condition is given for the symmetry planes, and the wall-type condition is applied for other surfaces.…”

Section: B Grid Mesh and Boundary Conditionsmentioning

confidence: 99%

“…In the study of the nozzle-flapper pilot valve, Aung and Li [12] found that the curved surface of the traditional flapper may contribute to the formation of the flow cavitation and consequently a rectangular flapper is proposed to suppress flow cavitation. Yang et al [13] further investigated the cavitation characteristics in the nozzle-flapper pilot valve using traditional flapper, rectangular flapper and square flapper, respectively. A detail comparison has been made among them.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Simulations on Flow Characteristics of a Nozzle-Flapper Servo Valve With Diamond Nozzles

Yang

Wen

2019

IEEE Access

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Nozzle-flapper servo valves are widely used in modern electro-hydraulic control systems of many engineering applications. Flow cavitation in the nozzle-flapper pilot stage could produce noise and cavitation erosion, reducing the performance stability and reliability of the servo valves. In this paper, diamond nozzles are proposed to replace the traditional circular nozzles to reduce the flow cavitation in the nozzle-flapper stage. Numerical simulations using CFD software ANSYS/FLUENT were conducted to explore the flow characteristics of the nozzle-flapper pilot stage. Mass flow rate and image measurements were performed to verify the simulation results. Vapor fraction, lateral velocity, pressure distribution, and flow force are compared in detail between the pilot stage with the traditional nozzles and with the diamond nozzles. It is found that the vapor fraction is greatly reduced under the effect of the diamond nozzles. Finally, to explore the effect of the diamond nozzles on the performance of the nozzle-flapper servo valve, the pressure-flow characteristics and time step response of the load flow rate are examined using the software AMESim. The simulation results show that the pressure-flow characteristics and time step response of the load flow rate almost remain the same. This suggests that the diamond nozzles could suppress the cavitation in the nozzle-flapper servo valve without varying its performance.

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Section: B Grid Mesh and Boundary Conditionsmentioning

confidence: 99%

Section: B Grid Mesh and Boundary Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical Simulations on Flow Characteristics of a Nozzle-Flapper Servo Valve With Diamond Nozzles

Yang

Wen

2019

IEEE Access

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“…Finally, the effectiveness of the innovative flapper shape was proved by showing the same flow control characteristics as the traditionally used flapper shape. Furthermore, three different flapper shapes were experimentally analyzed by Yang et al [17] to observe cavitation phenomena regarding two different flapper-nozzle null clearance (0.2 mm and 0.1 mm) under four different flow conditions with the variation of inlet pressures. To provide verification on experimental results and a comprehensive understanding, numerical simulations of the cavitation phenomenon in each flapper shape were also performed.…”

Section: Introductionmentioning

confidence: 99%

Numerical and Experimental Investigations of Cavitation Phenomena Inside the Pilot Stage of the Deflector Jet Servo-Valve

Saha

Peng

2020

IEEE Access

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Two-stage electrohydraulic servo-valves play an important role in the most modern hydraulic servo control systems for fight wing controls, manufacturing robots, and many engineering applications. The existence of cavitation inside the pilot stage is one of the root causes of self-excited noise, cavitation erosion, system jam, and frequent failures of electrohydraulic servo-valves. Thus, experimental and numerical investigations of the flow field and cavitation phenomena inside the pilot stage of deflector jet servo-valve under different supply pressures conditions are conducted in this paper. An assembly for experimental verification of the flow visualization process that represents the deflector jet pilot stage is produced and discussed. To test and verify the numerical simulations for cavitation phenomena, the flow field characteristics in the deflector jet pilot stage are investigated by using experimental flow visualization. The cavitation inception inside the pilot stage of the deflector jet servo-valve is experimentally confirmed through flow visualization. More importantly, the attached cloud-like cavitation or bubble shedding is observed along with the jet flow and the significant locations of cavitation inception are also identified for varying supply pressures. The profile of turbulent intensity confirms to conclude that turbulent pressure fluctuations contribute to cavitation. The result also shows that the increment of supply pressure intensifies cavitation and output pressure plays a significant role in reducing the intensity of cavitation inside the pilot stage of deflector jet servo-valve. Finally, the numerical results show good agreement with experimental results. INDEX TERMS Servo-valve, deflector jet servo-valve, turbulent flow, cavitation, numerical simulations.

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“…It is quite a similar case in the area of oil-hydraulics. Several scholars Aung, Yang, Chen, & Li, 2014;Li, Aung, Zhang, Cao, & Xue, 2013;Yang, Aung, & Li, 2015;Zhang & Li, 2015) have performed a series of investigation on cavitation phenomenon in a flapper-nozzle valve with a combined experimental and numerical method. This revealed the potential cavitation region as well as the evolution of cavitation structure with advance in cavitation intensity.…”

Section: Introductionmentioning

confidence: 99%

Comparison of compressible and incompressible numerical methods in simulation of a cavitating jet through a poppet valve

Yuan

Jun

Liu

2018

Engineering Applications of Computational Fluid Mechanics

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The regime of compressible flow generally refers to the super/subsonic case. However, several remarkable cases with low Mach number could not be appropriately described with the incompressible method. It is a similar case for a cavitating jet inside a poppet valve. In order to comprehensively address the discrepancy between incompressible and compressible methods, both non-cavitating and cavitating cases are performed in experiment and calculation based on OpenFOAM. Experiment reveals a transition in flow pattern in both non-cavitating and cavitating flow. For example, for 0.7 mm openness and 30-degree poppet angle, transition happens at approximately 29 and 27 bar pressure drop for the two cases, respectively. In general, results from the compressible method exhibit better agreement with experiment regarding both flow performance and flow structure. By contrast, the incompressible method could not provide an accurate description for the transition process under the applied flow condition. A series of studies are carried out with emphasis on such discrepancy. Firstly, the deviation in flow performance is addressed based on velocity profile and turbulence level. Secondly, the disparity in flow structure is illustrated and the mechanism for cavitation inception is discussed, which combined provide an interpretation of the deficiency of the incompressible method. Thirdly, different inlet boundary conditions are applied, and the results confirm the independence of deficiency of the incompressible method for inlet fluctuation. Finally, a re-examination is proposed concerning traditional notion of compressible flow as well as the applicability of incompressible numerical method.

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Confirmation on the effectiveness of rectangle-shaped flapper in reducing cavitation in flapper–nozzle pilot valve

Cited by 37 publications

References 19 publications

Numerical Simulations on Flow Characteristics of a Nozzle-Flapper Servo Valve With Diamond Nozzles

Numerical Simulations on Flow Characteristics of a Nozzle-Flapper Servo Valve With Diamond Nozzles

Numerical and Experimental Investigations of Cavitation Phenomena Inside the Pilot Stage of the Deflector Jet Servo-Valve

Comparison of compressible and incompressible numerical methods in simulation of a cavitating jet through a poppet valve

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