摘要：To fully use high-pressure air, the two-stage piston expander (TSPE) has been widely studied. The following factors obstruct the use of the TSPE: A high expansion ratio will inevitably result in a lower air temperature in the cylinder, causing adverse effects such as ice blockage and lubricating oil freezing; the residual air from the I-stage cylinder will all flow into the II-stage cylinder, causing a large reverse force to the I-stage piston during the working process. To address the above problems, a modified two-stage piston expander (M-TSPE) based on spray heat transfer is proposed. Firstly, the working principle of the M-TSPE is introduced, followed by the construction of a mathematical model of the M-TSPE. Secondly, the valve-timing of the M-TSPE is determined and compared with the output power and efficiency of the TSPE. The output power and efficiency of the M-TSPE are increased by 57.58% and 13.28%, respectively. Then, the performance parameters of the M-TSPE with and without spray are compared and analyzed. Finally, parameter analysis is carried out on the air/water mass ratio and water mist particle size. Results show that when the intake pressure and load torque are set to 3 MPa and 150 N·m, respectively, the output power of the M-TSPE without spray is 14.22 kW and the output power of the M-TSPE with spray is 16.08 kW, which is a 13.08% increase in output power. The average air temperatures in the I-stage cylinder of the M-TSPE with and without spray are 321 K and 263 K, respectively, and the average air temperature in the I-stage cylinder is enhanced by 58 K. The output performance of the M-TSPE can be improved by increasing the mass ratio of the water mist in the cylinder and decreasing the particle size of the water mist.
关键词：two-stage piston expander; spray heat transfer; high expansion ratio; output power; air temperature
