Investigating the non-flash-boiled hydraulic characteristics of superheated liquid hydrocarbon supply using multiple injectors

Abstract

An experimental study was conducted using a simple and novel experimental setup to investigate the non-flash-boiled supply of superheated hydrocarbons injected into a cavity-based combustor at varying fuel flow rates. The liquid hydrocarbon was steadily supplied via an isometric pump, heated to approximately 550 K using an induction heater, and sprayed upstream of the cavity through five identical plain injectors connected to a multi-branch manifold. The experimental results showed that inserting an orifice plate upstream near the manifold minimized fuel vaporization induced by flash boiling downstream of the heater. Consequently, the orifice plate effectively prevented any delay in the non-flash-boiled supply of the superheated fuel into the combustor during the variation of the fuel flow rate. In contrast, when the orifice was not inserted, the fuel supply was incipiently delayed owing to vaporization. Moreover, the results revealed that the discharge coefficient (Cd) of the superheated fuel depends on the square root of the difference between the injector and saturation vapor pressures (√ΔPs) rather than on the fuel temperature. Specifically, as √ΔPs increases, Cd first increases and then asymptotically converges to the discharge coefficient of the cold fuel. Similarly, the fuel flow rate was found to quadratically increase with √ΔPs, indicating that √ΔPs is a key factor in estimating the flow rate of the superheated fuel injection.