为解决双螺杆膨胀机应用于蒸汽压差发电领域，因为缺乏关于部分工况的理论研究，从而导致工程设计容易产生偏差的问题，本文建立了变负荷工况下双螺杆膨胀机工作过程的数学模型。完成了转子型线设计、型线间隙计算、几何过程量计算，引入了泄漏及换热模型，提出了部分负荷下吸气过程的吸气压力修正模型，同时整理了可用于简化计算的修正参数。实验表明，双螺杆膨胀机可以在工况波动较大的情况下稳定运行，并具有优良的变负荷工作性能。当负荷降低时，吸气压损有利于膨胀机压差降低，泄漏量降低，效率升高。从100%到65%负荷工况下，容积效率从78.87%升高到84.76%，绝热效率从66.81%升高到74.25%。与实验数据对比表明，本文提出的吸气压力修正模型中流量计算的误差可控制到3%以内。模型解决了部分负荷下的性能计算问题，使得理论模型能够更好地贴合实际应用，保证了双螺杆膨胀机主机选型计算的准确性。

In order to solve the problem of lack of theoretical research and error-prone engineering design of twin screw expander under partial load for power generation from steam pressure differential, a working process simulation of the twin screw expander was established. The rotor profiles were designed, the rotor meshing clearance and other geometric variables were calculated, the leakage and heat transfer models were established, the suction pressure correction model of the suction process under partial load was proposed, and the correction parameters that could be used to simplify the simulation were collated. Experiments show that the twin screw expander can operate stably under the working conditions with large fluctuations, and has excellent working performance of variable load. When the load was reducing, the pressure difference of the expander was reducing because of the suction pressure loss, the leakage was reducing, and the efficiency was increasing. Under the load condition from 100% to 65%, the volumetric efficiency increased from 78.87% to 84.76%, and the adiabatic efficiency increased from 66.81% to 74.25%. Compared with the experimental data, the error of flow calculation in the suction pressure correction model proposed in this paper can be controlled within 3%. The model could solve the performance calculation problem under partial load, so that the theoretical model can better fit the practical application under partial load condition, and ensure the accuracy of the selection of the twin screw expander.

压缩机技术国家重点实验室开放基金项目（SKL-YSJ201908）