中压调节阀参调供汽方式下高压缸气动性能分析研究

Analysis and Research on the Aerodynamic Performance of HP Cylinder under the Modeof Regulating Steam Supply with Intermediate Control Valve

针对某300MW机组的高压缸,在3个不同的背压3.4MPa、2.7MPa、1.9MPa下对末5级整体建模进行三维计算,对末3级气动流动特性进行分析,研究极限流线情况、沿叶高的等熵效率变化、相对做功量的变化情况。在背压控制在3.4MPa时,进汽流量减少到一定程度,末3级流动状态均开始恶化。当背压降低,低流量下状态有所改善。当背压持续降低时,动叶吸力面叶根及叶顶位置均有流动不稳定现象,动叶压力面和静叶表面则流动稳定,当流量减少时,动叶吸力面流动分离区域减小,流动状况改善。随着负荷降低,末3级总-总等熵效率呈逐渐下降趋势,且根、顶效率低于叶身,这与末3级动叶在叶根顶部存在分离现象有很大关系。在300MW机组上进行了试验,验证了数值计算结果的可靠性。给出各个工况下中压调节阀参调方式下高压缸排汽压力的上下限值,可得到中压调节阀的控制策略,为供热设计和运行调整提供依据。

For the high-pressure cylinder of a 300MW unit,three-dimensional calculations were conducted on the modeling of the last five stages under three different back pressures of 3.4MPa,2.7MPa,and 1.9MPa.The aerodynamic flow characteristics of the last three stages were analyzed,and the ultimate streamline situation,changes in isentropic efficiency along blade height,and changes in relative work were studied.When the back pressure is controlled at 3.4MPa,when the inlet steam flow rate decreases to a certain extent,the flow state of the last three stages begins to deteriorate.When the back pressure decreases,the state at low flow rates improves.When the back pressure continues to decrease,there is flow instability at the root and top positions of the suction surface of the moving blade,while the flow is stable on the pressure surface of the moving blade and the surface of the stationary blade.When the flow rate decreases,the flow separation area on the suction surface of the moving blade decreases,and the flow condition improves.As the load decreases,the total isentropic efficiency of the last three stages gradually decreases,and the root and top efficiencies are lower than those of the blade,which is closely related to the separation phenomenon of the last three stage moving blades at the top of the blade root.Under the regulation condition of middle note valve,the blade frequency and strength can ensure safety due to the small temperature variation range.The upper and lower limits and corresponding constraints of exhaust pressure control of HP cylinder under the middle note valve participation mode under various working conditions are given,which can provide relevant guidance for the design and safe operation of middle note valve steam supply.And a lie test was conducted on the calculation object of 300MW to verify the reliability of the numerical calculation results.The control strategy of the medium pressure regulating valve can be obtained by providing the upper and lower limits of the exhaust pressure of the high-pressure cylinder under the parameter adjustment method of the medium pressure regulating valve under various working conditions.Provide a basis for heating design and guidance on operational adjustments.