The effect of the arrangements for compression process and expansion process on the performance of the two-stage condensation Rankine cycle

Aiming at the problem that the irreversible loss of the condensation process for the traditional LNG power generation system is too large, this paper presents four different two-stage condensation Rankine cycles based on different arrangements of pumps and turbines. The effects of the operating conditions (the first-stage and second-stage condensation temperatures) and various working fluids on the performance of the four cycles with different structures are investigated. The results show that when the arrangement of the turbines is the same, the arrangement of the pumps (series or parallel) has little effect on the net output power. However, when the arrangement for the pumps is the same, the arrangement for the turbines has a significant effect on the net output power. When the working fluid is n-pentane and the turbines are of series arrangement, the maximum net output power is increased by about 17% compared with the condition that the turbines are of parallel arrangement. In addition, for the same cycle, whether the isentropic efficiency of turbine is a constant value or not has a significant effect on the maximum net output power, the optimal operating conditions, and the optimal working fluid.