Measurement of the Effectiveness of Concave Spherical Dimples for the Enhancement of Hot-gas Side Heat Transfer

摘要

In an expander cycle rocket engine, the turbo-pump is driven by a gaseous propellant that has been heated in channels incorporated into the thrust chamber wall. The power output of the turbine islimited by the hot gas wall heat transfer coefficient and surface area. To increase the chamber pressure, additional pump power and heat are required. Part of the increase can come from an increased heat transfer coefficient at elevated chamber pressure, but this is not sufficient; and engine designs have also required an increase in surface area, typically by elongating the chamber, or a supplemental increase in heat transfer coefficient by one of the methods of heat transfer enhancement. In the Orbital Transfer Vehicle program, several styles of longitudinal ribs were examined, and enhancements of 40-50% were measured; however, there are other approaches which should also be considered because the tips of ribs are vulnerable to hot spots and may become points of incipient failure.