Research and development of steam twin screw expander

The expansion working process of a steam twin screw expander was theoretically studied. The influences of internal volume ratio, thermal parameters of inlet steam, under-and over-expansion on the recovery work of the steam screw expander were investigated. The effects of the deviation between the optimum internal volume ratio and the actual internal volume ratio on the recovery work and volume flow of the steam screw expander were analyzed. The results show that under-expansion and over-expansion can lead to the decrease in recovery work of the steam twin screw expander compared with full expansion. The decrement of recovered power by under-expansion is less than that by over-expansion when the pressure difference between the internal pressure of end expansion and discharge pressure is the same. There is an optimum internal volume ratio matching the maximum recovery work at certain thermal parameters of inlet steam. It is suggested that large scale twin screw expanders should be designed according to the under-expansion condition because under-expansion will cause small drop in the recovery work and significant decrease in the volume flow ratio.