Development and application of a pre-design tool for aero-engine combustors

Kurzfassung

A software tool was developed to design aero engine combustors on a preliminary level with a small number of input parameters. This tool is capable to design conventional as well as lean combustors and to choose between four different cooling concepts. During the design calculation the combustor 2D-contour, the geometry of the desired cooling concept and the air distribution within the combustor are optimized at the take-off condition. Optimization targets are to reach minimal cooling air consumption with respect to the material temperature limits and to reach a homogeneous wall temperature as well as a stable combustion. Furthermore in the case of a staged burner the air and fuel fractions are optimized regarding minimal NOx emissions (qualitative) during take-off. Off-design calculations can be conducted for engine conditions apart from take-off to calculate the altered conditions within the combustor and to check the boundary conditions during part load. The first part of this paper shows the design and off-design process in detail and in the second part application examples are presented. In the application part three different lean combustors are designed and compared to each other. The demonstrated results show the trade-off between the reduction of NOx emissions on one hand and the reduction of fuel consumption on the other hand. Furthermore off-design calculations are performed on a conventional combustor to identify potential cooling issues during part load. The results show the capabilities of the tool to pre-design conventional as well as lean combustors.