Experimental and numerical investigation of blade height effects on micro-scale axial turbines performance using compressed air open cycle

摘要

This study experimentally and numerically investigates the effects of three blade heights (4 mm, 6 mm and 8 mm) on the performance of micro-scale axial turbines using compressed air open cycle. The numerical development for the micro-scale axial turbines was developed by using ANSYS CFX software which simulates the three dimensional viscous compressible flow through turbine passages. The blade height in the micro-scale axial turbine has major impact on its performance since it controls the annular area for axial turbine passages, and in turn that will control the turbine flow rate and power output. Increasing turbine blade height will increase power output, while decreasing turbine blade height will reduce the power output at the same expansion ratio. The experimental results showed that at an expansion ratio of 1.75 and a rotational speed of 16000RPM, the maximum power produced was 630.75 W, 694.1 W, and 796.89 W for the blade heights of 4 mm, 6 mm, and 8 mm, respectively. The maximum respective efficiencies at a pressure ratio of 1.3 were: 47.1%, 39.8%, and 38.83%. Comparison with experimental results showed the validity of the developed CFD models for the turbines with deviation percentage in terms of efficiency were +16%, +15%,+13% respectively, and in terms of power output were +14.5%, +14%,+12%.