Efficiency optimization of power systems such as diesel and liquid propelled rocket engines leads to mixture behavior to enter transcritical and supercritical regimes, where distinct coupling mechanisms from those at subcritical conditions govern the thermophysical processes.
In the present manuscript, we numerically evaluate the effect of pseudo-boiling at supercritical liquid- and gas-like conditions (reminiscent to liquid and gas phases) and compare the results against experimental nitrogen injection data, which serves as a surrogate for the oxygen-hydrogen propellant combination encountered in most liquid rocket engines. Thus, we can evaluate supercritical fluid behavior using nitrogen without including combustion and finite-rate kinetics into the computational model.
We can show the occurrence of density stratification at both liquid- and gas-like conditions, directly connected to the event of the pseudo-phase change inside the injector, meaning that in certain situations, we can have the same fluid behavior for both pseudo-phases. However, density stratification at liquid-like conditions has not been demonstrated in the literature. Therefore, it is an argument in favor of the importance of injector heat transfer in the computational modeling of such flows.