On the basis of the operating feature of screw compressors, the critical angles of the working chamber in different processes were determined under part-load conditions. A model was established to calculate the effective by-pass area and radial discharge area at a certain rotation angle of the male rotor under various part-load conditions. The influences of key design parameters on the geometrical characteristics of a screw refrigeration compressor under part-load conditions were investigated, such as the slide stop length and slide valve installation position relative to the cylinder. The results show that, in order to improve the performance of screw refrigeration compressors under part-load conditions, the fixed type slide stop with 20％-25％ of the rotor length should be adopted for a fixed external pressure ratio while the moveable type should be applied for variable external pressure ratios. Moreover, the slide valve installation angles relative to the cylinder should be as large as possible in the installation space.%基于螺杆压缩机的工作特点,确定部分负荷下各工作过程的特征角度,建立了有效旁通面积和有效径向排气面积的计算模型,从而可以准确得到不同负荷下任一转角所对应的流通面积,为部分负荷下螺杆制冷压缩机工作特性研究奠定了基础.考察了固定块长度以及滑阀相对气缸端面的安装位置等关键设计参数对压缩机部分负荷下内容积比、有效旁通面积和有效径向排气面积的影响.研究表明,若运行工况压力比单一,固定块应选择固定式,其长度取转子长度的20%～25%为宜,若运行工况压力比多变,应选择可调式固定块,而滑阀相对气缸端面的安装角度应在安装空间允许范围内尽可能大,以提高螺杆制冷压缩机在部分负荷时的性能.
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