偏导射流伺服阀前置级流场特性研究

建立偏导射流伺服阀前置级流场精确且完整的数学模型，对伺服阀先导级设计和研究有着重要作用。将射流过程分为初次射流、偏导板压力恢复、二次射流、接收口压力恢复4个阶段，在前置级二次射流过程中分别采用不同理论模型来构建前置级流场完整的数学模型，对射流形态的演变过程进行了描述。分析发现，油液射流进入前置级流场与偏导板侧壁发生撞击，流动形态发生改变，一部分油液沿侧壁反向流出偏导板，另一部分油液流速降低在下游形成高压区。油液流出偏导板时受到分流器的作用，分别流入不同通道。根据节流模型流量和压力特性公式求得了压力增益，并建立起负载压力与偏导板偏移量之间的数学关系。数值模拟过程中，采用不同湍流模型对前置级流场压力分布进行了分析。通过数值模拟仿真结果、外特性实验结果与射流模型计算结果的比较和分析，验证了该模型描述射流特性的有效性和合理性。

Research on Flow Field in Pre-stage of Jet Deflector Servo Valve

A precise and complete mathematical model for the flow field in the pre-stage of jet deflector servo valve is established for the design and research of pilot-stage servo valve.The jet process is divided into four stages:initial jet,deflector pressure recovery,secondary jet,and pressure recovery at receiver opening.In the process of two jets in the pre-stage,the different theoretical models are adopted to build the complete mathematical model of flow field in the pre-stage,and the evolution of jet pattern is described in detail.It is found through analysis that the oil enters the flow field in pre-stage and impacts on the side wall of deflector,and then the flow pattern changes,one part of oil flows out of the deflector along its side wall,the flow velocity of the other part of oil decreases,and a high pressure zone is formed downstream.The oil is affected by the flow divider when it flows out of the deflector,and flows into different channels.The flow and pressure characteristic equations are used to derive the pressure gain,and a mathematic relation between load pressure and deflector offset is established.In the process of numerical simulation,the different turbulence models are adopted to analyze the pressure distribution of flow field in the pre-stage.The effectiveness and rationality of the proposed model describing the jet characteristics is verified by comparing and analyzing the numerically simulated results,the external characteristic experimental results and the calculated results of jet model.