液氧输送管路中阀控瞬变的数值计算

Numerical computation of hydraulic transients in valve operating processes of LO2 delivery pipes

摘要:

为了预测航天器液氧输送系统中阀控动作产生的水力瞬变,考虑非稳态摩阻和波纹管弹性形变的影响,建立输送硬管、波纹软管、液氧贮罐及控制阀的数学模型,并利用求解一阶偏微分方程的特征线法和求解一元二次非线性方程的线性理论法对管路阀控瞬变进行数值计算. 通过变化计算条件,讨论不同阀特性、阀动作指数和动作时间对瞬变过程的影响. 计算结果表明：采用调节阀进行阀控动作产生的压力波动明显比截止阀小,调节阀比截止阀更容易控制液氧输送总量精度；延长调节阀关阀时间能够有效降低水击压力,延长截止阀关阀时间更多地表现为延长第一个水击波到达的时间,而不是水击压力的降低；阀动作指数m=1.0的调节阀采用快开慢关方案对瞬变过程控制最有利. 

Abstract:

To predict hydraulic transients of operating processes of control valve of LO₂ delivery pipes for space vehicle, mathematical models of rigid pipe, corrugated pipe, LO₂ tank and control valve were established on consideration of the influences of unsteady friction and corrugated pipe elastic deformation, numerical computation was carried out by method of characteristics to solve first order partial differential equation and method of linear theory to solve second order non-linear equation with single variable. Different influence to transient flow is discussed by changing flow characteristic, motion index and motion time of control valve. Calculations show that pressure surge in transient flow caused by operation of valve with equal percentage flow characteristic (VWEPFC) is significantly weaker than that of valve with quick opening flow characteristic(VWQOFC). The total accuracy of LO₂ delivery is more easily controlled on operation of VWEPFC opposite to VWQOFC. Extending the closing time of VWEPFC could reduce the pressure surge efficiently, but the effect of extending the closing time of VWQOFC is mainly delayed arrival time rather than reduction of water hammer wave. Valve motion index of VWEPFC equal 1.0 and fast-opening along with slow-closing program is optimum to transient control of LO₂ delivery pipes. 