Temperature increase-isentropic efficiency integration map: A novel compressor performance map for gas turbine engines start-up

The compressor sub-idle map is crucial for the start-up simulation performance of component-level models (CLMs) for gas turbine engines (GTEs). Therefore, the compressor sub-idle map generation is currently a research focus in CLM start-up simulation. However, the compressor sub-idle map generated using traditional methods fails to maintain accuracy while resolving isentropic efficiency discontinuities, and some methods additionally depend on compressor geometry parameters. To address these challenges, a novel temperature increase − isentropic efficiency integration map (TIEIM) method is proposed in this paper. By integrating temperature increase and isentropic efficiency parameters, the TIEIM method generates the compressor sub-idle map that simultaneously maintains accuracy and resolves isentropic efficiency discontinuities, only requiring regression models optimization based operating data. The TIEIM method consists of three modules: 1) A temperature increase map (TIM) is designed based on computational fluid dynamics, enhancing the map accuracy for the compressor in turbine and stirrer modes. 2) An isentropic efficiency map (IEM) is designed based on empirical derivation, enhancing the map accuracy in compressor mode while resolving isentropic efficiency discontinuities. 3) An integration process is designed based on cubic spline, enabling a smooth switch between the TIM and IEM. Optimization with actual start-up data indicates that the TIM and IEM designed in this paper outperform traditional regression models. The mean absolute percentage errors (MAPEs) of the exit total temperature for the TIM reduce from 0.756 %, 1.456 %, 0.936 %, and 1.125 % to 0.191 %, while the corresponding MAPEs for the IEM reduce from 0.087 %, 0.097 %, 0.092 %, and 0.140 % to 0.064 %. Comparative tests with three traditional methods indicate that TIEIM not only reduces the MAPEs of the exit total temperature from 1.477 %, 1.722 %, and 1.280 % to 0.116 % but also enables simulation in both turbine and stirrer modes. Furthermore, CLM simulation tests indicate that the maximum iteration residual never exceeds 10^-6, while the MAPEs for low and high-pressure shaft speeds, total pressure after the high-pressure compressor, and total temperature after the low-pressure turbine all show more than 50 % improvement in accuracy compared to the torque method. These results demonstrate that the TIEIM method successfully enhances map accuracy while resolving isentropic efficiency discontinuities. Moreover, CLM simulation results demonstrate that this method significantly improves overall engine accuracy while maintaining iterative convergence, highlighting its strong potential for engineering applications.