Experimental study on the off-design performances of a micro humid air turbine cycle: Thermodynamics, emissions and heat exchange

Micro humid air turbine (mHAT) is a promising distributed generation technology. However, the experiments, especially on the off-design characteristics, are still insufficient to support the theoretical model. In this paper, a detail experimental study is presented on a mHAT converted from a recuperated microturbine by introducing a humidifier, an aftercooler and an economizer. The steady-state thermodynamic performances, and the combustion and emission characteristics are evaluated at rated and part load condition. The off-design performances of the heat exchangers are also evaluated. It is shown that the specific output power and the electrical efficiency are relatively increased by 45% and 18.6% respectively comparing with the recuperated cycle at the rated load, and show a greater relative increment at part load, such as 58.1% and 21% respectively at 62.5% load. Introducing water into the air reduces the risk of NOx formation, but increases dramatically the risk of CO formation and incomplete combustion in the combustion chamber, thus the combustion efficiency deteriorates up to 92.5% at 50% of full load. The introduced heat exchange units display the characteristic of high effectiveness and low pressure loss, which is important for gas turbine system. The recuperator developed for the dry air also displays superior thermodynamic performance for the wet air with humidity ratio up to 0.108 kg·kgda−1.