关于二级液压节流锥阀的低汽蚀研究论文外文翻译中英文文献对照翻译.docx

1、关于二级液压节流锥阀的低汽蚀研究论文外文翻译中英文文献对照翻译中文共4400字第一部位外文原文标题：关于二级液压节流锥阀的低汽蚀研究Research on low cavitation in water hydraulic two-stage throttle poppet valveAbstract: Cavitation has important effects on the performances and lifespan of water hydraulic control valve, such as degrading efficiency, intense noise, an

2、d severe vibration. Two-stage throttle valve is a practicable configuration to mitigate cavitation, which is extensively used in water hydraulic pressure relief valves and throttle valves. The pressure distribution inside a medium chamber located between two throttles of a two-stage throttle valve i

3、s investigated through numerical simulations. The effects of the passage area ratio of the two throttles and the inlet and outlet pressures on the pressure inside the medium chamber are examined. The simulation results indicate that (a) the pressure inside the medium chamber is not constant, (b) the

4、 locations of maximum and minimum pressures inside the medium chamber are both fixed, which will not vary with the passage area ratio or the inlet and outlet pressures, and (c) the ratio of the pressure drop across the front throttle to the total pressure drop across the two-stage throttle valve is

5、nearly constant. The critical cavitation index of the two-stage throttle valve is then established. A semiempirical design criterion is obtained for the water hydraulic two-stage throttle valve. The correlation between the critical cavitation index and the passage area ratio of the two throttles is

6、investigated. Relevant validation experiments are conducted at a custom-manufactured testing apparatus. The experimental results are consistent with the simulated ones. Further analyses indicate that (a) the large backpressure can improve not only the anti-cavitation capability but also the total lo

7、ad rigidity of the water hydraulic two-stage throttle valve, (b) an appropriate passage area ratio will be beneficial for improving the anti-cavitation capability of the water hydraulic two-stage throttle valve, and (c) the water hydraulic two-stage throttle valve with a passage area ratio of 0.6 wo

8、uld have the best anti-cavitation performance with the lowest risk of cavitation. Keywords: computational fluid dynamics simulation cavitation load rigidity passage area ratio two-stage throttle valve water hydraulics1 INTRODUCTIONWater hydraulic systems are operated with raw water (pure tap water)

9、substituting for mineral oil. They have advantages in terms of durability, reliability, safety, and cleanness. Such systems are becoming more and more popular, especially in fields of steel and glass production, coal and gold mining, food and medicine processing, nuclear power generation, ocean expl

10、oration, and underwater robotics 15.Because the opening of a water hydraulic control valve is very small compared with that of oil valve, the water flow velocity through the water hydraulic control valve is larger under the same pressure condition; thus cavitation erosion may occur due to the high v

11、apour pressure of water. Cavitation has an important effect on the performance and lifespan of water hydraulic control valve, such as degrading efficiency, intense noise, and severe vibration. Previously, a number of studies on the relationships between cavitation and discharge coefficient, thrust f

12、orce and pressure distributions in the valves, and mitigation of cavitation damage were carried out through increasing outlet pressure of valves, modifying shapes of throttles, adding stages of valves, selecting anti-corrosion materials for parts, and controlling maximum fluid temperature and flow v

13、elocity. Tsukiji et al. 6 investigated cavitation by flow visualization in hydraulic poppet-type holding valves to reduce cavitation. Some measures were employed to diminish noise and cavitation through controlling flowrate, upstream pressure, downstream pressure, and valve lift in case of convergin

14、g flow.Aoyama et al. 7 studied experimentally the unsteady cavitation performance in an oil hydraulic poppet valve. It was found that, as absolute values of the variation rates of inlet and outlet pressure increased, the incipient cavitation index exhibited a tendency to decrease, whereas the final

15、cavitation index a tendency to increase under all geometrical parameters. As the absolute values of the variation rates of inlet and outlet pressure further increased, the hysteresis between the incipient and final cavitation indices would become larger than ever for each combination of the valve an

16、d valve seat.Ishihara et al. 8 studied oil flow unsteadiness effect on cavitation phenomena at sharp-edged orifices. The rate of pressure drop across the orifice was kept constant, and cavitation incipience and finale were recorded by using scattered laser beams showing that (a) there existed two ty

17、pes of cavitation, namely, gaseous cavitation and vapourous cavitation, and (b) cavitation incipience and finale varied with the initial condition, the temperature of hydraulic oil, and the rate of pressure drop.Johnston et al. 9 carried out an experimental investigation of flow and force characteri

18、stics of hydraulic poppet and disc valves using water as the working fluid. The axisymmetric valve housing was constructed from clear perspex to facilitate flow visualization; tests were performed on a range of different poppet and disc valves operating under steady and non-cavitating conditions, fo

19、r Reynolds numbers greater than 2500. Measured flow coefficients and force characteristics showed obvious differences depending on valve geometry and opening.Vaughan et al. 10 conducted computational fluid dynamics (CFD) analysis on flow through poppet valves. Simulations were compared with experime

20、ntal measurements and visualized flow patterns. A qualitative agreement between simulated and visualized flow patterns was identified. However, errors in the prediction of jet separation and reattachment resulted in quantitative inaccuracies. These errors were due to the limitations of the upwind di

21、fferencing scheme employed and the representation of turbulence by the k 1 model, which was known to be inaccurate when applied to recirculating flow.Ueno et al. 11 investigated experimentally and numerically the oil flow in a pressure control valve under an assumption of non-cavitating conditions f

22、or various configurations of the valves on the basics of a finite difference method. They concluded that the main noise of the testing valves was generated from cavitation, and the noise was affected by the valve configuration. Pressure measurements and flow visualization at two locations in a valve

23、 chamber were also performed on the basis of two-dimensional models. Through comparisons of the measured and calculated results, several design criteria were set up for low-noise valves.Martin et al. 12 investigated cavitation in spool valves in order to identify damage mechanisms of the related com

24、ponents. Tests were conducted in a representative metal spool valve as well as a model being three times larger. Data taken under non-cavitating conditions with both of these valves showed that the orientation of high-velocity angular jets would be shifted due to variations in valve opening and Reyn

25、olds number. By means of high-frequency response pressure transducers strategically placed in the valve chamber, the cavitation could be sensed through the correlation of noise with a cavitation index. The onset of cavitation could be detected by comparing energy spectra for a fixed valve opening wi

26、th a constant discharge. The incipient cavitation index, as defined in this investigation, was correlated with the Reynolds number for both valves.Gao et al. 13 performed a simulation of cavitating flows in hydraulic poppet valves by means of an renormalization group (RNG) k 1 turbulence model, whic

27、h was derived from the nstantaneous NavierStokes equations based on the RNG theory. Experiments were conducted to catch cavitation images around the seat of a poppet valve from perpendicular directions, using a pair of industrial fibre scopes and a high-speed visualization system. The binary cavitat

28、ing flowfield distributions obtained through digital processing of the original cavitation image showed satisfactory agreement with numerical results; the vibrations of valve body and poppet induced by the cavitating flow were detected using a vortex displacement transducer, a laser displacement met

29、re and a digital strain device. It was concluded that the opening and cone of a conical valve had significant effects on the intensity of cavitation. However, in this study, only downstream cavitation inception volume was analysed in estimating the anti-cavitation capability, whereas the effects of

30、outlet pressure were not considered.Oshima et al. 14 experimentally investigated the influences of (a) chamfer length in the valve seat, (b) the poppet angle, and (c) the oil temperature on the flow characteristics and the cavitation phenomena, using water instead of oil as the working medium in wat

31、er poppet throttles. The cavitation phenomena were directly observed and the pressure distribution between the valve seat and poppet surface was measured in water poppet throttles. Comparison analyses on the condition of critical cavitation were conducted between oil and water. It was found that the

32、 discharge coefficient and the critical cavitation number for water poppet throttles were considerably different from those of oil ones, due to the high density and low viscosity of water. Recently, Liu et al. 15, 16 investigated experimentally the flow and cavitation characteristics of a two-stage

33、throttle in water hydraulic system; they concluded that the two-stage throttle had stronger anti-cavitation capability than the single-stage one, and that the shape of seats also affected the anti-cavitation capability of the throttles. The cavitation choking appeared only when cavitation index was less than 0.4. They also conducted severa