Studies in Optimizing the Film Flow Rate for Liquid Film Cooling

摘要

Liquid film cooling is an important method for cooling the walls of a liquid rocket engine. Mass transfer via entrainment decreases the effectiveness of the film coolant and it is therefore important to estimate the amount of film coolant that establishes itself along the wall of a combustion chamber if the coolant flow rate is to be optimized. However, film entrainment research is limited in regards to film cooling applications in rockets. The correlations and theories that have been published are often contradictory and have only been tested at momentum fluxes that are an order of magnitude less than those typically experienced in rockets. Experimental research has been conducted in a cold-flow test article at AFRL in order to investigate the effects of gas stream momentum flux on the optimal liquid flow rate. This paper summarizes the results of those tests. In addition, the thickness of the liquid film appears to be an important variable governing the establishment of the liquid film. This paper also investigates the ability of laser focus displacement meter (LFD) to measure the thickness of shear-driven liquid films driven by gas-phase momentum fluxes ranging from 2,270 Pa to 110,000 Pa.