实际中冷时多级压缩最佳压比的计算

目前，多级压缩最佳压比分配是在中间冷却效果完善及不考虑中冷时存在的压力损失条件下，按压缩机理论耗功为最小来确定的。结论是各级压比分配相等时为最佳，但实际中冷情况并非如此。本以理论耗功最小为目标，分别在换热率恒定或吸气温度恒定等实际中冷的条件下，导出2级和3级压缩最佳压比分配的计算公式，并以2级为例，分析偏离最佳压比值对耗功能的影响。得出多级压缩最佳压比分配与中冷条件有关，即使在相同的冷却条件下，2级和3级压缩最佳压比分配趋向也不相同，对于2级压缩而言，实际压比在最佳值的（0.96-1.06)范围内变化对耗功影响不大于理论耗功值的0.5%，这可视为调整压缩机压比的许可范围。

OPTIMUM OF PRESSURE RATIOS OF MULTI-STAGE RECIPROCATING COMPRESSOR WITH PRACTICAL INTER-COOLING

The optimum pressure ratio distribution of a multistage reciprocating compressor is presented based on the assumption, i.e. the inter-stage cooling is perfect and there are no pressure losses. The optimization of the two or three-stage pressure ratio is analyzed in two cases of constant heat transfer rate for the inter-cooler or constant inter-stage inlet temperature, based on the minimum of the sum of theoretical compression power at each stage about a multi-stage reciprocating compressor. Furthermore, with an example of two-stage compressor the influence on the sum of the power of each stage is analyzed when practical pressure ratio deviates from the optimum value. It is obtained that under different cooling conditions the optimum pressure ratio distribution of the multi-stage compression is various, and the change of the optimum pressure ratio within a small range has little influence on the sum of the power each stage. For the two-stage compression, this range can be represented as ε1=(0.96～1.06)ε1j.