Numerical study of shear-induced heating in high-speed nozzle flow of liquid monopropellant

A numerical study is performed which focuses on peak temperatures experienced by a liquid monopropellant during high-speed injection in a small-diameter nozzle. Attention is focused on short-duration injection during which the nozzle wall boundary layer is predominantly laminar. An unsteady ID analysis of the temperature distribution associated with sudden fluid acceleration over a flat insulated boundary is first conducted. Expressions are provided which relate the normalized peak wall temperature to the prevailing Eckert and Prandtl numbers. Results reveal a quadratic dependence of the normalized wall temperature on impulse velocity, and a nonlinear variation with Prandtl number. Next, simulation of high-speed flow in an axisymmetric nozzle is performed. The numerical schemes are based on finite-difference discretization of a vorticity-based formulation of the mass, momentum, and energy conservation equations. Implementation of the numerical schemes to flow of LP 1846 in a 4 mm diameter nozzle indicates that preignition is likely to occur for velocities higher than 200 m/s. The effects of wall heat transfer and temperature-dependent properties are also discussed.