Water injection in a microgasturbine - Assessment of the performance using a black box method

Microturbines offer new perspectives in small-scale heat and power production however their profitability depends strongly on the yearly amount of running hours. The non-continuous heat demand often leads to a reduction in running hours. This paper proposes an alternative by recuperating the lost thermal power through the injection of heated water in the microgasturbine. Water injection is considered a successful way to increase power and efficiency in industrial gas turbines and similar effects are expected for microturbines. This paper reports on a series of simulations of water injection performed on a Turbec T100 microgasturbine. The goal of this study was to investigate the potential of water injection in the microgasturbine cycle using an adiabatic black box method in the Aspen® process simulation tool. Past experiments with steam injection on the T100 demonstrated the potential of introducing steam/water in the microturbine cycle.
Calculations revealed that the key parameters for maximum heat recuperation are stack and pinch temperature. Simulations showed that most of the exhaust heat can be recovered through injection of heated water after the compressor, resulting in 18% decrease in fuel consumption and an absolute increase in electrical efficiency of 7%.