Combustion performance of an adjustable fuel feeding combustor under off design conditions for a micro-gas turbine

To respond to off-design operation of the micro-gas turbines, this research proposed an adjustable fuel feeding combustor (AFFC). The AFFC employed a main fuel distribution device and an active control method called the adjustable fuel feeding method (AFFM). Through the main fuel distribution device, the AFFC can switch various groups of working main fuel tubes (MFTs), ultimately achieving the AFFM. Each group has a different symmetrical distribution feature of working MFTs. Based on these features, the AFFM characteristic number (U) has a unique calculation value for the AFFM at each group, and particularly, it was entirely different from the values of U for the AFFM at the other groups. In this research, four different working MFT groups were presented, and the values of U were calculated to be 0.143, 0.333, 0.429 and 1 for the AFFM at each group, respectively. As U changes, the AFFC combustion performance was investigated numerically at various combustor inlet air temperatures (T-3) of 600, 700, 800, 900 and 1000 K. Moreover, the CFD method applicability was verified by the experimental data. The results indicate that at different T-3, NO emission has various trends with the rising U due to the coupling influences of the fuel flow and fuel jet velocity of each working MFT, while CO emission and combustion efficiency are only affected by the AFFM at the low T-3 of 600 K. The outlet temperature distribution factor keeps growing, and the total pressure recover factor remains almost the same as U rises.