Numerical and experimental investigation of leakage behavior at null position of high-pressure electro-pneumatic servo valve

The high-pressure electro-pneumatic servo valve(HESV)is a core element of the high-pressure pneumatic servo system.The annular clearance and the rounded corner of the spool-sleeve can cause the leakage at null position,thereby affecting high-precision control and stability of the servo system.This paper investigates the effects of the clearance structure on leakage behavior at null position of the HESV.A numerical approach was employed to evaluate the effects,and then a mathematical model was established to obtain the variation law of leakage flow rate at null position.The results indicate that the leakage flow rate at null position varies linearly with supply pressure and rounded corner radius,and is nonlinear as a quadratic concave function with annular clearance.The leakage flow rate of the annular clearance and the rounded corner varies with the valve opening in an invariable−nonlinear−linear trend.A test rig system of leakage behavior at null position of the HESV was built to confirm the validity of the numerical model,which agrees well with the conducted experimental study.

Numerical Simulation on a Throttle Governing System with Hydraulic Butterfly Valves in a Marine Environment

Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.

Development of a Novel Parallel-spool Pilot Operated High-pressure Solenoid Valve with High Flow Rate and High Speed

High-pressure solenoid valve with high flow rate and high speed is a key component in an underwater driving system.However,traditional single spool pilot operated valve cannot meet the demands of both high flow rate and high speed simultaneously.A new structure for a high pressure solenoid valve is needed to meet the demand of the underwater driving system.A novel parallel-spool pilot operated high-pressure solenoid valve is proposed to overcome the drawback of the current single spool design.Mathematical models of the opening process and flow rate of the valve are established.Opening response time of the valve is subdivided into 4 parts to analyze the properties of the opening response.Corresponding formulas to solve 4 parts of the response time are derived.Key factors that influence the opening response time are analyzed.According to the mathematical model of the valve,a simulation of the opening process is carried out by MATLAB.Parameters are chosen based on theoretical analysis to design the test prototype of the new type of valve.Opening response time of the designed valve is tested by verifying response of the current in the coil and displacement of the main valve spool.The experimental results are in agreement with the simulated results,therefore the validity of the theoretical analysis is verified.Experimental opening response time of the valve is 48.3 ms at working pressure of 10 MPa.The flow capacity test shows that the largest effective area is 126 mm2 and the largest air flow rate is 2320 L/s.According to the result of the load driving test,the valve can meet the demands of the driving system.The proposed valve with parallel spools provides a new method for the design of a high-pressure valve with fast response and large flow rate.

Simulation research on dynamic performance of the new type high-pressure solenoid valve

To improve energy density,the transportation,storage,and operations of hydrogen,methane,and compressed air vehicles currently require high-pressure compression.High-pressure solenoid valve becomes the vital element to above system.In order to reduce leakage and aerodynamic force influence,a new type high-pressure solenoid valve was proposed.The simulation model which included electromagnetic model,aerodynamic force model was established by means of the nonlinear mathematic models.Using the software MATLAB/Simulink for simulation,the dynamic response characteristics of high-pressure pneumatic solenoid valve were obtained under different pulse width modulation(PWM)input control signals.Results show that,first of all,the new type of high-pressure solenoid valve can meet the switch requirement.Secondly,the opening movement and closing movement of the spool lags the PWM rising signal,and the coil current fluctuates significantly during the movement of the spool.Lastly,on/off status of high-pressure valve cannot be represented by the duty cycle.This research can be referred in the design of the high-pressure solenoid valve..

Experimental investigation on control and reduction of vibration induced by fluid flow in turbine governing valve

Governing valve is the necessary passage through which steam enters into the steam turbine. The instability of the gas flow inside valve is the main reason that can induce the valve vibration, especially the valve rod vibration. In order to reduce the vibration and improve the performance of the governing valve such as the security and economy of the steam turbine, we try to find the method by experimental investigation. As to commonly used governing valve such as ball governing valve in this paper, a number of micro pressure sensors that have high frequencies and nice dynamic capability are employed successfully. The micro sensors are inserted directly in key positions of the valve, such as positions of valve seat throat, valve disc top and so on. The collection and measurement of many different working conditions are carried out and the conclusion of the valve instability is obtained. Therefore, vibration induced by fluid flow is controlled and reduced by means of regulating operation conditions and valve structure. Meanwhile, by numerical simulation of ball governing valve, valve disc adhered flow and asymmetric collision force are considered as main factor to cause oscillation under the condition of small lift as well as small and middle pressure ratio.

The Influence of Overlap Degree Research on Nozzle Governing Characteristic

To solve the problems existing in the flow characteristics of steam turbine unit, the influence of valve overlap degree on nozzle governing steam turbine had been studied. The combined flow characteristics of given valve overlap degree were obtained for a 600MW steam turbine unit by the method of theoretical calculation combined with simulation test, and the influence of valve overlap degree on governing stage efficiency and steam chest pressure had been also analyzed. This paper discussed the selection of rational overlap degree and introduced a new method of building model for governing stage efficiency of steam turbine in constant pressure operation condition, which provided theoretical guidance for optimization research on nozzle governing steam turbine operation.

数据驱动下汽轮机流量特性动态测量技术研究

随着新型电力系统快速发展,发电机组深度参与电网调峰调频,高调门作为机组调峰调频重要执行机构,其流量特性也越来越重要。常规试验方法测取的流量特性区间较小,且无法实时在线监测。通过数据驱动建模,采集机组实时运行数据,深度测量汽轮机流量特性。应用结果表明:该方法测量的高调门流量特性和汽轮机流量特性与试验数据基本吻合,极大提升了流量特性测取区间,实现了汽轮机流量特性在线监测。

海上采油平台自力式调节阀在线校验研究

自力式调节阀是一种无需外来能源,依靠被测介质自身压力或温度或流量变化来进行自动调节的阀门,是根据力学原理将被控介质引入执行机构产生力作用推动控制阀芯原件上下位移达到自动调节,阀前或阀后恒压或减压的节能型产品。该阀集测量、执行和控制等功能于一身,自成一个独立的仪表控制系统,具有结构简单、价格便宜和动作可靠等特点,适用于调节精度要求不高或仪表气源供给困难的场合,广泛应用于化工、石油、电力、轻工、冶金等工业部门的自控系统。自力式调节阀有自力式压力(微压)调节阀、自力式(压差)流量调节阀、自力式温度调节阀等几类。针对渤海某海上采油平台自力式调节阀在线校验问题进行研究。

多基地汽轮机调节系统保护油卸载阀卡涩原因分析

高压调节阀是核电汽轮机的关键设备之一,其动作的可靠性直接影响汽轮机的运行安全。已有10台ALSTOM半速汽轮机投入运行,其中8台机组存在保护油卸载阀(CVS)卡涩导致高压汽阀定期带负荷活动试验失败的问题,且该问题重复发生将对于机组安全运行造成严重影响。基于CVS结构特点,从阀门加工装配质量工艺、表面沉积产物、运行环境等方面,查明CVS频繁卡涩的关键影响因素以及故障机理;针对性地提出CVS装配间隙标准优化、驱动机构维修周期优化、油品漆膜关键指标管控等改进措施。新改进措施在多基地实施,结果表明:高压汽阀定期带负荷活动试验成功率大幅度提高,同时创造了巨大的经济效益。

古田溪水力发电厂轴流转桨式调速系统改造

针对古田溪水力发电厂轴流转桨式调速系统更新改造问题,介绍了WZT-100型轴流转桨式调速系统组成及其控制,根据接力器行程与导叶开度和桨叶角度的关系,精确计算导叶开度和桨叶角度,应用水轮机的特性曲线,提高调节性能和安全性。目前该系统已稳定运行2年多。实践表明:改造后机组功率调节性能、机组效率及运行稳定性均有提升。

Seal contact performance analysis of soft seals on high-pressure hydrogen charge valves

The charge valve is an important element in the charging port of a high-pressure hydrogen storage cylinder(HP-HSC).It is normally closed after the HP-HSC is filled with hydrogen.If the seal of the charge valve is damaged,it will seriously affect the stable operation of the hydrogen supply system and may even cause safety problems.Therefore,the seal performance of the charge valve is important.In this paper,finite element analysis(FEA)is carried out to analyze the seal contact performance of hydrogenated nitrile rubber(HNBR)gaskets in the seal pair of a charge valve.The effects of different pre-compressions,seal widths,and hydrogen pressures on the seal contact performance of the charge valve are analyzed.The contact pressure on the seal surface increases with the increase of pre-compression.With a pre-compression of 2.5 mm,the maximum contact pressure without and with hydrogen pressure are 68.51 and 107.38 MPa,respectively.A contact gap appears in the inner ring of the seal surface with pre-compression below 0.15 mm.The contact gap occurs between the entire seal surface with a seal width of1 mm.The contact pressure on the seal surface and the width of the separation area between the seal surfaces increase with the increase of the seal width.The contact gap between the seal surfaces is zero with a width of 2.5 mm.The width of the separation area between the seal surfaces decreases with the decrease of the hydrogen pressure.The width of the separation area is reduced from 0.5 mm at 35 MPa to 0.17 mm at 15 MPa.This work can be useful for improvement of the seal performance and of the design of the charge valve used in the HP-HSC.

某新型液压电磁阀的可靠性分析策略

针对某新型液压电磁阀可靠性试验缺乏指导原则的问题,对传统故障模式影响及危害性分析(Failure Mode Effects and Criticality Analysis,FMECA)方法进行了改进,并基于改进后的FMECA分析方法对该阀进行可靠性理论分析。将模糊综合评判方法引入传统FMECA分析方法中,通过建立因素集、评价集和权重集确定评估框架,再引入“梯形模糊数”提高FMECA分析方法的准确性,应用改进后的分析方法计算得到该电磁阀薄弱环节的影响因素。将影响因素进一步划分并通过二次分析确定了影响因素中的最极限工况。最后,通过仿真验证了可靠性理论分析方法的正确性,为该阀提供可靠性研究及试验的参考标准。

组合阀在调速系统的应用与改进

目前水电厂调速系统压油泵应用的阀组多为分体式结构,存在调试不便、调整值易变等问题。介绍了一种新型组合阀,通过在三峡电站现场的实际运用,并对其结构的某些部位进一步改进,使其结构与性能更加完善。该组合阀结构简单,调试方便,现场运行稳定可靠,并可满足水电厂自动化运行的要求。

汽轮机调节汽阀抖动原因分析及处理

A核电厂机组大修后升功率期间因为汽轮机进汽阀门开度抖动导致功率异常波动,影响机组安全运行。经过系统的检查确定阀门开度抖动原因为定位器响应过于灵敏,频繁调节导致异常抖动。通过理论分析和试验验证在保持定位器整体性能的前提下通过减少伺服阀阀芯坡口打磨等工艺改进可以有效降低定位器抖动。

1000MW超临界汽轮机主调阀内流动和噪声计算分析

针对某1000 MW超临界汽轮机主调阀系统(主汽阀和调节阀)内的蒸汽流动和噪声辐射,进行了全三维计算分析。通过求解全三维N-S方程和k-ε湍流模型,并考虑水蒸汽热力性质参数,得到了阀门流道中的蒸汽流场参数;然后采用基于FW-H方程的剪切流噪声模型,求解了蒸汽流场内的噪声源幅度分布。计算结果表明:主调阀流道内的压力损失为1.38%,其中调节阀部件的压损占主调阀总压损的66%;主汽阀和调节阀的喉口位置和阀腔流动死区等位置处的涡量很强,从而成为主要的气动噪声辐射源。

基于特征通流面积的汽轮机流量特性辨识方法

对于长期运行后的机组,经常出现汽轮机某些阀位区间负荷响应良好而某些阀位区间负荷响应不理想,究其原因为汽轮机调节阀组的流量特性发生偏离。为使汽轮机流量特性的设定与实际相匹配,本文通过对某660 MW机组汽轮机运行历史数据的挖掘和分析,结合其特征通流面积的特点,提出了一种新的流量特性曲线辨识方法。应用结果表明:该方法可有效辨识出汽轮机额定主蒸汽压力下的流量特性曲线;分段线性优化了流量管理函数;提高了顺序阀模式下汽轮机整体流量特性线性度;重新确定了阀间重叠度,为同类机组汽轮机的流量特性曲线辨识优化提供了参考。

大容量汽轮机不同阀序工况下调节级叶片的动应力数值分析

以某600MW汽轮机调节级叶片为研究对象,分析了复合阀和顺序阀两种配汽方式3种工况下调节级叶片的气动载荷。考虑部分进汽引起的阶跃激励和Kick效应的影响,采用三维有限元法数值分析了3种工况下调节级叶片的瞬态动力响应和动应力,进而对阀序改造后调节级叶片的安全可靠性进行了分析。

降低阀门节流损失的阀门管理新策略

论述了DEH控制系统在阀门管理方面的先进功能 ,分析总结了工程实际中降低调节阀门节流损失的技术途径 ,并在此基础上提出了DEH控制系统中降低调节阀门节流损失的阀门管理新策略 ,使调节级的效率在机组运行的整个负荷区段达到最高 ,特别适用于调峰机组的经济运行 ,且易于实施 。

燃气-蒸汽联合循环机组自动起停控制系统(APS)的应用

结合深圳东部电厂一期3×350MW燃气-蒸汽联合循环机组的自身特点,介绍了该机组APS的设计结构。通过对原APS的中压并汽调节阀控制和锅炉暖管疏水控制的优化,实现了机组一键自动起、停功能。

基于带死区投影分段线性化方法建模的汽轮机调门流量特性优化

针对火电机组运行过程中因高调门实际流量特性与DEH设定的理论流量特性函数差异过大,而导致的机组负荷跳变、调门抖动、AGC负荷控制精度和一次调频能力不佳的问题,依据调门实际流量特性,基于带死区投影算法分段建立汽机调门开度-流量指令的线性化模型,结合汽机调门进汽量和阀切换的离散化机理公式,计算单阀和顺序阀方式下的调门流量特性函数。最后,通过在某200 MW机组实际应用,验证了该方法的可行性。