The Effect of Compressor Stage Impeller Gap Tolerances on the Performance of a Solarised Micro Gas Turbine

Abstract The environmental benefits of concentrating solar power (CSP) combined with the high continuous output power of a micro gas turbine (MGT) offer a unique method for producing electricity as a solar-hybrid system. The two primary methods to improve the performance and efficiency of an MGT are to raise the temperature of the combustor inlet and to increase the pressure ratio of the compressor stage. The effect of improving the performance of a MGT by reducing the geometric tolerances of the compressor stage is applied to an MGT testbench intended for use in a solar-hybrid application. The MGT features a centrifugal compressor which is favoured over axial compressors because of its higher per stage pressure ratios being achieved. The existing compressor is initially simulated using a Computational Fluid Dynamics (CFD) analysis to generate pressure ratio and efficiency performance charts. A second CFD simulation is performed on the compressor, whose geometric tolerances are reduced to a realistically achievable manufacturing tolerance with standard machinery of 0.3 mm. With this modification, the compressor's pressure ratio increases from 1.482 to 1.524 and its efficiency improves from 78.3–81.4%. The simulated output power on the MGT testbench increases from this modification by 18.2%, from 18.1 kW to 21.4 kW. This study not only illustrates an improvement in the performance of the MGT testbench, but it also enables further development in subsequent stages and, ultimately, promotes the use of solar-hybrid electricity generation.