【正文】 2]通過研究芯閥的汽蝕現(xiàn)象問題用來識別和損傷機制相關(guān)的組件。 Ueno [11]用實驗和數(shù)值模擬的方法研究了用最基本的有限差分在假設(shè)沒有汽蝕在條件下對不同構(gòu)造壓力控制閥的油液流動 ,。仿真被用于比較實驗測量和可視化流動模式。 Johnston[9]進行了一項關(guān)于在提升和圓盤液壓閥中流動和力學(xué)特性的實驗研究 ,并采用水作為工作介質(zhì)。 Aoyama[7]實驗研究了在油壓提升閥中出現(xiàn)的不穩(wěn)定汽蝕現(xiàn)象，結(jié)果發(fā)現(xiàn) ,隨著入口和出口壓力變化速率絕對值的增加，初期的汽蝕指數(shù)表現(xiàn)出一種減小的傾向 ,而最后的汽蝕指數(shù)有增加到所有的幾何參數(shù)之下的趨勢 ,。汽蝕對水液壓控制閥的性能和壽命有重要影響 ,如降低效率、強烈的噪聲以及嚴重的振動。 1 介紹 水壓操作系統(tǒng)用原水 (純自來水 )替代礦物油。相關(guān)驗證實驗在一個定制的測試儀器中進行。仿真結(jié)果表明 ,(1)介質(zhì)腔內(nèi)的壓力不是固定的 ,(b)介質(zhì)腔最大和最小壓力的位置都是固定的 ,不會隨著通道面積比率或進出口壓力而變化 ,(c)流過前面節(jié)流閥和流過二級節(jié)流閥的總壓降的壓降比值幾乎不變。 the pressure levels on the virtual line were denoted as pl. The effects of the passage area ratio (r) on the pressure (pl) under condition of pin . 10 MPa and pout . 4 MPa are illustrated in Fig. 4. The pressure level would vary with the passage area ratio. The larger the passage area ratio r, the higher the pressure level on the virtual line. However, when r is less than , the pressures inside the medium chamber would bee low. This was attributed to the small front throttle, which could be considered as a jet nozzle. The fluid would have less direction variations and jet contraction when passing through the front throttle. A high flow velocity through the front throttle would be generated, and thus the pressure would decrease rapidly. In such a case, the flow pattern would be like that of a singlestage throttle. From Fig. 4, the pressure levels on the virtual line (l) would vary at different space positions, confirming that the pressure levels inside the medium chamber were not constants. It was also very interesting that the locations of the maximum and minimum pressures were fixed on the virtual line, being indifferent of the variations of the passage area ratio. 關(guān)于二 級 液壓 節(jié)流錐閥 的低汽蝕研究 摘要 ：汽蝕 對 于 液壓控制閥的性能和壽命有重要影響 ,如 引起 效率的降低 ,產(chǎn)生 強烈的噪音 和振動。 the effects of pressure and temperature on the density and viscidity of water are neglectable。 tests were performed on a range of different poppet and disc valves operating under steady and noncavitating conditions, for 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 putational fluid dynamics (CFD) analysis on flow through poppet valves. Simulations were pared with experimental 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 differencing 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 noncavitating conditions for 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 chamber were also performed on the basis of twodimensional models. Through parisons of the measured and calculated results, several design criteria were set up for lownoise valves. Martin et al. [12] investigated cavitation in spool valves in order to identify damage mechanisms of the related ponents. Tests were conducted in a representative metal spool valve as well as a model being three times larger. Data taken under noncavitating conditions with both of these valves showed that the orientation of highvelocity angular jets would be shifted due to variations in valve opening and Reynolds number. By means of highfrequency 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 paring energy spectra for a fixed valve opening with 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, which was derived from the nstantaneous Navier–Stokes 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 highspeed visualization system. The binary cavitating flowfield distributions obtained through digital processing of the original cavitation image showed satisfactory agreement with numerical results。 thus cavitation erosion may occur due to the high vapour press