Experimental characterization of a T100 micro gas turbine converted to full humid air operation

Micro Gas Turbines (mGTs) were considered very promising for small-scale Combined Heat and Power (CHP) production. They however never fully penetrated the CHP market, resulting in a limited market share. Due to their low electric efficiency (30% versus 80% CHP efficiency), the operation of the mGT is strongly heat-driven. In applications with a non-continuous yearly heat demand, like domestic heating systems, the mGT would be shut down for long periods, resulting in a reduced amount of yearly running hours. These limited running hours make the mGT as smallscale CHP less profitable compared to other technologies, like reciprocating engines. Converting the mGT into a micro Humid Air Turbine (mHAT) offers a solution. The waste heat in the exhausted gases is recovered in the mHAT by evaporating auto-raised hot water behind the mGT compressor, resulting in a higher electric efficiency and a more flexible mGT operation. In this paper, we present the results of experiments on a modified Turbec T100 mGT. As a proof of concept, the mGT has been equipped with a spray saturation tower to humidify the compressed air. The goal of these experiments was to evaluate the beneficial effect of compressed air humidification on the mGT performance. Two stable runs at constant pressure ratio and rotation speed were recorded during water injection. Final electric efficiency results show a relative electric efficiency increase of 1.2% and 2.4%. These changes are however in the range of the accuracy of the measurements. Further experiments are therefore necessary to fully characterise the behaviour of the mHAT at part and nominal load. Fine-T uning of the water injection control strategy is also identified as a key parameter to reduce the auxiliary power losses. © 2014 Published by Elsevier Ltd