Research Combustor ‘N’: Combustion Chamber With Large Optical Access for Injection and Combustion Characterization at Sub- and Supercritical Pressure Conditions

Abstract

Future space missions demand the development of advanced rocket engines featuring improved injection elements or novel injection technologies. Insufficient characterization of the injectors in the development of cryogenic rocket engines may not only lead to poor combustion efficiency but also the threat of destructive dynamic behavior like hard ignition transients or thermoacoustic instabilities. The DLR Institute of Space Propulsion works on understanding the causes of such phenomena with the help of specialized experiments. The optically accessible sub-scale research combustor ’N’ (BKN) was developed for detailed characterization of the transient and steady-state behavior of cryogenic injection technologies. Combining optical imaging with unsteady pressure measurements allows injection and combustion dynamics to be characterized using such metrics as 2D-Rayleigh-Indices, RayleighIndex-Spectra and Flame-Transfer-unctions. Another aspect focuses on providing well-defined boundary conditions, offering valuable opportunities to validate the complex modeling of combustion in liquid rocket engines. Validated simulations, in turn, provide insights into processes that cannot be directly measured in experiments.