为分析抽汽背压式汽轮机(Backpressure Extraction Steam Turbine,BEST)回热系统的变工况工作特性及保证小汽轮机与给水泵之间的功率匹配，提出采用小发电机、节流阀、补汽阀的3种控制策略，根据汽轮机、回热加热器等主要设备的变工况过程建立BEST系统的变工况数学模型，分析各负荷下BEST和给水泵系统的功率匹配特性和回热系统抽汽参数的变化规律。研究表明：小汽轮机与给水泵的功率差值随着负荷降低先增加后降低，最大值出现在约50%负荷左右；采用小发电机调节，BEST末级排汽流量与压力近似不变；采用节流阀调节，BEST末级排汽流量与压力随负荷降低而降低；采用补汽阀调节，BEST末级排汽压力与流量随负荷降低而升高；小发电机调节方式的热经济性最佳，相对于其他两种调节方式的热耗率明显偏低，节流调节方式存在节流损失，补汽阀调节在BEST末级排汽供汽中引入了大量经过再热的抽汽，提高了抽汽过热度，降低了系统效率。

In order to analyze the off-design characteristics of the heat regeneration system in the BEST system and how to control the power matching between the BEST steam turbine and the feed water pump,three different control strategies are proposed.According to the work process of the main equipment such as steam turbine,regenerative heater,the off design mathematical model of the BEST system is established.According to the calculation results,the power difference between the BEST steam turbine and the feed water pump first increases and then decreases as the load decreases.The maximum value appears at about 50% load.With generator adjustment,BEST exhaust steam flow and pressure are approximately the same when the load changes.With throttle adjustment,BEST exhaust flow and pressure at the end of the stage decrease with decreasing load.With overflow steam adjustment,BEST exhaust pressure and the flow rate increase as the load decreases.The thermal efficiency is the best for the generator adjustment method,and its heat rate is significantly lower than the other two adjustment methods.Throttling loss exists in the throttle adjustment method.The adjustment of the overflow steam valve introduces reheated extraction steam into the BEST exhaust steam,which increases the extraction superheat and reduces system efficiency.

TM621

中国华能集团公司总部科技项目（HNKJ16-H11）