Wall Heat Flux Evaluation In Regeneratively Cooled Rocket Thrust Chambers

In the present Paper, different wall heat flux evaluation methods for rocket engines are analyzed and compared. The test case for the comparison is a supercritical load point of an H2/O2 upper-stage engine. The evaluation of the heat flux using existing gradient methods shows unacceptable deviations, whereas significant improvements are found with an inverse heat transfer method. Using a Nusselt number correlation for the modeling of the cooling channel heat transfer coefficient, good agreement with the experimental profiles is achieved, while the number of installed thermocouples is held at a minimum. However, the choice of the Nusselt number correlation directly influences the obtained results and strongly depends on the fuel and geometry of the system. Using a simultaneous optimization of the heat flux and heat transfer coefficient, on the other hand, seems to eliminate the need for additional modeling and leads to great agreement with the experiment. A new optimization method proposed in this Paper based on a preprocessed Jacobi matrix significantly speeds up the estimation of the free parameters. With the obtained results, the placement of the thermocouples before the design of the hardware can be optimized, leading to reduction of manufacturing costs.