【摘要】：社會需求是推動技術(shù)發(fā)展的強大動力。液壓技術(shù)飛速發(fā)展，要求液壓系統(tǒng)滿足高壓力、大流量，但體積小、重量輕，且高精度、高效率，液壓插裝閥技術(shù)在此形勢下應運而生，二通插裝閥的出現(xiàn)使液壓技術(shù)的發(fā)展提高到了一個嶄新的階段。在某些應用場合，插裝閥是提高生產(chǎn)力和競爭力的唯一選擇。 液壓閥相關(guān)的科學問題，各類型液壓閥的流量特性、作用在閥芯上液動力的大小和方向、液動力對閥工作可靠性、操作靈活性和動靜態(tài)特性的影響、內(nèi)部流場的可視化計算等，一直是流體傳動與控制技術(shù)領(lǐng)域中的基礎(chǔ)研究問題，也是發(fā)展高性能液壓控制閥必須解決的關(guān)鍵問題。錐閥作為插裝閥的主要結(jié)構(gòu)形式，通過研究發(fā)現(xiàn)，現(xiàn)有理論有待進一步研究解決完善。 閥口過流斷面面積直接影響閥過流特性的計算，但關(guān)于錐閥過流斷面計算公式的現(xiàn)有理論尚存在問題。閥芯帶錐但錐面不完整的錐臺形錐閥和閥座帶錐的錐閥在計算流量時采用按完整錐面錐閥導出的過流面積計算公式，會造成非常大的計算誤差。從過流斷面的定義出發(fā)，利用CFD流場可視化技術(shù)對錐閥的流場進行深入細致地研究分析，找出了其在整個大行程范圍內(nèi)不同開口度時的過流斷面位置。在研究中發(fā)現(xiàn)在小的閥芯行程范圍內(nèi)傳統(tǒng)過流斷面面積計算公式仍適用，若閥芯行程較大，傳統(tǒng)公式不再適用，且內(nèi)外流不同流動工況時流動特征出現(xiàn)很大的差異。首先確立傳統(tǒng)公式適用的臨界開口度，推導了不同行程時的過流斷面面積計算公式。并指出閥口錐部導流作用不同，局部損失不同是造成內(nèi)外流流動特征差異的根源。閥口的抗氣蝕特性也是閥口節(jié)流性能好壞的一個重要指標，但判斷空化初生的標準目前尚未統(tǒng)一。通過分析液壓閥內(nèi)液流流動過程，追溯空化產(chǎn)生根源，提出了壓力恢復系數(shù)表征不同閥的抗氣蝕能力。 液動力對閥的動靜態(tài)特性關(guān)系甚大，是設(shè)計液壓閥需考慮的重要因素。液動力計算公式是液壓系統(tǒng)特性建模重要的基本方程之一，對液壓系統(tǒng)的特性有很大影響。閥芯開口度大時，錐臺形錐閥和閥座帶錐錐閥過流斷面的位置和計算發(fā)生變化，傳統(tǒng)的理論公式對其液動力的計算也不再適用。液動力本質(zhì)上是流體運動所造成的閥芯壁面壓力分布發(fā)生變化而產(chǎn)生的，故從流場分析入手，獲得閥芯底部壓力分布值，將壓力相對作用面積積分，得到其液動力值，這是最直接的計算方法，且可細化流場信息得知液動力產(chǎn)生的機理。為了便于工程實際使用，根據(jù)流場分析得出的液動力產(chǎn)生的主要因素，結(jié)合控制體積的選取原則，對于不同閥口形式錐閥，內(nèi)外流工況不同時，選取不同的控制體積。根據(jù)動量定理推導出的相應的計算公式，最終給出了不同流動方向下閥口全行程時的液動力特性，精確度更高。 傳統(tǒng)的液動力計算公式中，液動力與進出口壓力差值成正比，與進出口壓力值的大小無關(guān)。但錐閥進出口壓差相同，進出口壓力值低時，閥內(nèi)流動狀態(tài)變?yōu)閮上嗔鳎c單相流的流動特征不同，故需對傳統(tǒng)公式進行修正。提出用臨界進口壓力值和臨界出口壓力值來區(qū)分閥內(nèi)液流不同流動特征。利用全空穴模型對閥內(nèi)流場進行了兩相流模擬仿真，分析閥內(nèi)流場壓力分布，明確相同進出口壓差，不同進出口壓力值時液動力區(qū)別的真正原因，對傳統(tǒng)公式進行修正，推導出了適用于兩相流狀態(tài)下液動力的計算公式，并利用已有的試驗數(shù)據(jù)進行了驗證。 液壓技術(shù)遍布整個工業(yè)控制領(lǐng)域，包括一些高科技領(lǐng)域，，為了達到更加精準的控制，對控制元件的特性要求將更加苛刻。因此在研究插裝閥流量特性時，考慮閥套和閥芯變形對于節(jié)流口過流面積及閥套閥芯間配合間隙的影響，將是液壓元件設(shè)計理論不斷完善化所必須的。建立實際使用的插裝閥整體三維模型，包括閥芯閥體閥套，進行了插裝閥液固熱耦合分析。首先根據(jù)液壓閥流體流動過程的傳熱特點，對液流流動過程流場、溫度場進行數(shù)值模擬，得到整個錐閥固體、液體區(qū)域內(nèi)詳細的溫度場分布規(guī)律，最后給出熱應力和液壓力共同作用下的閥套閥芯變形量。分析表明閥芯閥套的變形對于閥芯閥套的配合間隙有一定的影響，但兩者的作用根據(jù)錐閥工況的不同，會有很大的變化，在實際過程中應該針對典型工況進行具體分析；閥芯閥套的變形對錐閥節(jié)流特性的影響一般可以忽略不計。對閥整體的流固熱耦合分析在一定程度上可科學估算變形量對閥套閥芯配合間隙及閥口特性的影響，從而為閥套閥芯設(shè)計提供可供參考的依據(jù)。 最后搭建了插裝閥流量特性和動態(tài)特性測試試驗臺進行試驗研究。測試閥在不同壓差，不同開口度的穩(wěn)定流動時的流量特性，驗證過流斷面面積計算公式的正確性。建立閥的AMEsim仿真模型，結(jié)合推導出的液動力公式和過流斷面面積計算公式進行模型參數(shù)設(shè)置，模擬閥的階躍響應；給定閥不同階躍信號，測試閥的階躍響應。將階躍響應的仿真值和試驗值進行比較，結(jié)果表明采用提供的液動力公式得到的計算結(jié)果是可信的。 以上研究成果進一步完善了有關(guān)液壓閥流體力學的基本理論，給出了能準確描述錐形插裝型主閥在大行程范圍內(nèi)閥芯所受液動力的計算公式、錐閥過流斷面面積的計算公式，為從機理上建立液壓閥準確的數(shù)學模型進行非線性數(shù)字仿真研究提供了一定理論基礎(chǔ)并具有一定的工程實用價值。
[Abstract]:With the rapid development of hydraulic technology, the hydraulic system is required to meet the requirements of high pressure, large flow, but small size, light weight, high precision and high efficiency. The technology of hydraulic cartridge valve came into being under this situation. The emergence of two-way cartridge valve has raised the development of hydraulic technology to a new stage. In some applications, cartridge valves are the only option to increase productivity and competitiveness.
The scientific problems related to hydraulic valves, the flow characteristics of various types of hydraulic valves, the magnitude and direction of hydrodynamic forces acting on the spool, the effects of hydrodynamic forces on the operational reliability, operational flexibility, dynamic and static characteristics of the valve, and the visualization calculation of internal flow field have been the basic research issues and development in the field of fluid transmission and control technology. The key problem of high performance hydraulic control valve must be solved. As the main structure form of cartridge valve, cone valve has been found that the existing theory needs to be further studied and solved.
The cross-section area of valve orifice has a direct influence on the calculation of valve flow characteristics, but there are still some problems in the existing theory about the calculation formula of cone valve cross-section. Based on the definition of cross section, the flow field of cone valve is studied and analyzed by CFD visualization technology, and the position of cross section with different openings in the whole large stroke range is found. If the spool stroke is large, the traditional formula is no longer applicable, and the flow characteristics are very different under different flow conditions. Firstly, the critical opening of the traditional formula is established, and the formula for calculating the cross-section area of the flow passage under different flow conditions is deduced. Cavitation resistance is also an important indicator of throttling performance, but the criteria for judging cavitation initiation are not yet unified.
Hydraulic power has a great influence on the dynamic and static characteristics of the valve and is an important factor to be considered in the design of hydraulic valves.The hydraulic power calculation formula is one of the important basic equations for modeling the characteristics of hydraulic systems and has a great influence on the characteristics of hydraulic systems. The traditional theoretical formula is no longer applicable to the calculation of its hydrodynamic force. The hydrodynamic force is essentially caused by the change of the pressure distribution on the wall of the valve spool caused by the fluid movement. Therefore, starting from the analysis of the flow field, the value of pressure distribution at the bottom of the valve spool can be obtained, and the value of hydrodynamic force can be obtained by integrating the pressure relative action area. In order to facilitate the practical use of engineering, according to the main factors of hydrodynamic force produced by the analysis of flow field and the selection principle of control volume, different control volumes are selected for cone valves with different valve ports under different internal and external flow conditions. The corresponding formulas are used to calculate the hydrodynamic characteristics of the valve orifice in different flow directions with higher accuracy.
In the traditional hydrodynamic calculation formula, the hydrodynamic force is directly proportional to the difference of inlet and outlet pressure, and has nothing to do with the value of inlet and outlet pressure.But when the inlet and outlet pressure is the same, the flow state in the valve becomes two-phase flow when the inlet and outlet pressure is low, which is different from the flow characteristics of single-phase flow, so the traditional formula needs to be revised. Value and critical outlet pressure are used to distinguish the different flow characteristics in the valve.The two-phase flow field in the valve is simulated by using the full-cavity model.The pressure distribution in the valve is analyzed.The real reason for the difference of hydrodynamic force under the same inlet and outlet pressure difference and different inlet and outlet pressure value is clarified.The traditional formula is revised and its application is deduced. The calculation formula of hydrodynamic force in two-phase flow is verified by the existing experimental data.
Hydraulic technology spreads all over the industrial control field, including some high-tech fields. In order to achieve more precise control, the characteristics of control components will be more demanding. Therefore, in the study of cartridge valve flow characteristics, considering the influence of valve sleeve and spool deformation on throttle flow area and valve sleeve spool clearance, it will be hydraulic. It is necessary to perfect the theory of component design. A three-dimensional model of cartridge valve is established, including the valve body sleeve. The liquid-solid-heat coupling analysis of the cartridge valve is carried out. Firstly, according to the heat transfer characteristics of the fluid flow process of the hydraulic valve, the flow field and temperature field of the fluid flow process are numerically simulated, and the solid and liquid of the whole cone valve are obtained. The analysis shows that the deformation of the spool sleeve has a certain influence on the fit clearance of the spool sleeve, but the two effects will vary greatly according to the different working conditions of the cone valve and should be aimed at in the actual process. The influence of the deformation of the spool sleeve on the throttling characteristics of the cone valve can be neglected. To a certain extent, the influence of the deformation on the fit clearance and the valve port characteristics of the spool sleeve can be scientifically estimated by the Fluid-Solid-Heat coupling analysis of the whole valve, thus providing a reference basis for the spool design of the valve sleeve.
Finally, a test bench for measuring the flow characteristics and dynamic characteristics of cartridge valves is built to test the flow characteristics of the valves under steady flow with different pressure differences and different openings. The model parameters are set up to simulate the step response of the valve, and the step response of the valve is tested with different step signals given. The results of the simulation and test of the step response are compared. The results show that the calculation results obtained by the hydrodynamic formula are reliable.
The above research results have further improved the basic theory of hydraulic valve hydrodynamics, given the calculation formula which can accurately describe the hydrodynamic force acting on the valve core of conical cartridge type main valve in the large stroke range, the calculation formula of the cross-section area of conical valve flow, and carried on the nonlinear digital imitation for establishing the accurate mathematical model of hydraulic valve from the mechanism. Real research provides a theoretical basis and has certain engineering practical value.
【學位授予單位】：太原理工大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TH137.52

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