Experimental investigation of saturated fogging and overspray influence on part-load micro gas turbine performance

Micro gas turbines (MGTs) are promising power sources for modern industries, especially in the distributed energy generation market, due to their relatively high projected energy densities. Nevertheless, they suffer from lower thermal efficiency due to the inherent constraint of high- exhaust temperature and the relatively high compression work, especially during hot days and partial load operation. Water injection into gas turbine inlet air is a possible route to improve the MGT performance. As a result of the lack of previous experimental studies related to the study of fog and overspray on turbines at partial load operations, the current study aims to evaluate the influence of saturated fogging (inlet fogging) and overspray on the MGT part-load performance experimentally. Two test benches were installed to implement inlet fogging and overspray on a 10 kW MGT. Droplet size and injected water mass flow were measured at varied spraying pressures and nozzle diameters to determine optimum spray conditions. The output power and specific fuel consumption were measured at different overspray ratios for various MGT loads. The results showed that the enhancement in power output due to inlet fogging and overspray varied according to the applied load. After applying saturated fogging, the output power augmentation corresponding to a 14 °C-temperature drop was 9.32 % at a load of 30 %, while this value decreased to 6.86 and 4.91 % for loads 50 and 70 %, respectively. It was also observed that a continuous boost in net power output with an increased overspray ratio. Increasing the load from 30 to 70 % reduced the power enhancement by about 42 and 39 % for overspray ratios of 1 and 2 %, respectively. The maximum output power and specific fuel consumption improvement were achieved at a 2 % overspray ratio. Inlet fogging and overspray reduced NO concentrations for all loads, and vice versa for CO concentrations, and emission slop decreased with the load.