Entropy generation minimization of a regenerative cooling system for a scramjet inlet

Abstract

© 2024 Elsevier LtdThis study explored the challenge of managing overheating in scramjet engines through regenerative cooling techniques using hydrogen as a coolant. The aim was to reduce the high temperatures between the airflow and compression ramps at the scramjet inlet by affixing small-scale channels to the engine wall. The modeling process involved a two-dimensional CFD) simulation for the scramjet inlet and discretization of each cooling jacket channel into duct elements. After obtaining the CFD flow solution, the wall heat flux distribution was incorporated into the cooling channel model, initiating a forward marching procedure to compute the temperature and pressure distributions. The converged distributions are then used to calculate the entropy generation rates along the cooling jacket. The simulations demonstrate that higher Reynolds numbers lead to increased thermodynamic losses despite the improved heat transfer efficiency. Conversely, lower altitudes contribute to higher entropy generation rates owing to increased heat generation from flow compressibility and amplified flow acceleration. Additionally, higher Mach numbers intensify the entropy generation, resulting in elevated heat fluxes at the scramjet wall. Considering the entropy generation rate as an objective function that must be minimized, an optimum coolant mass flow rate can be achieved for different freestream airflow conditions. It is evident that implementing channel-specific geometry with second-law analysis is an appropriate strategy for mitigating extreme wall temperatures, thereby enhancing the performance and prolonging the service life of scramjet engines.

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