Preliminary experimental study of single screw expander prototype

Efficient heat conversion of low temperature heat source is a key problem for energy saving, especially in the fields of waste heat recovery and renewable energy utilization. At present, technical bottleneck for low temperature thermal power is lack of suitable prime mover. As the core component of general machinery, single screw has many good features, including balanced loading of the main screw, low leakage, low noise, low vibration and long working life, etc. If single screw technology is applied to the field of expander, more efficient prime mover would be possibly obtained, compared with pistol expander, scroll expander and twin screw expander, and so on. In order to verify the performance of the prototype, the function experiment was made. In this paper, compressed air was used as working fluid and performance test for the prototype was finished at conditions including different intake flow, different humidity, constant torque, and constant rotational speed. From the experimental data, it is shown that the power output is 5 kW, exhaust temperature is −45 °C, difference between the import and export is about 62 °C, in the conditions of inlet pressure at 0.6 MPa and rotational speed 2850 rpm. The test results also show that the single screw expander has good part load characteristics. From the analysis of experimental data, we found that adiabatic efficiency of the prototype is not so high probably because of poor lubrication. The lubrication problem will be considered in the next work.

► We carried out the test for single screw expander prototype at different conditions.
► Maximum power output is 5 kW in the 2850 rpm rotational speed.
► Maximum temperature difference between the import and export is 62 °C.
► Total efficiency is 32.5% at the condition of the maximum power output.
► Phase change in expansion process has significant effects on efficiency.