Schlieren visualization of the interaction of jet in crossflow and deflagrated flame in hydrogen-air mixture

Abstract

The objective of this study is to investigate the interaction of a jet-in-crossflow (JICF) and a deflagrated flame in a stoichiometric hydrogen-air mixture. The JICF is introduced prior the arrival of a deflagrated flame, therefore the JICF has a certain time to disturb the flow. By adjusting the time delay before the flame contacting the jet (td) and the pressure ratio (pJ/p0), the interaction between JICF and deflagrated flame and the subsequent flame evolution are recorded by a high-speed Schlieren visualization apparatus. The results show that the deflagrated flame without the perturbation of JICF has a quasi-parabolic shape, which is due to the flame suffering strong shear stress from wall boundaries. At higher initial pressure, the propagation velocity is faster. By introducing JICF, the flame speed is promoted, this is because JICF establishes pressure differential regions in the two sides of the jet, forming pressure gradients and flow instabilities, and increasing the turbulent transport between reactant and product, which accelerates the flame propagation. At relative low and medium pressure ratio (i.e., pJ/p0 = 10 and 20), shorter td has a better performance on enhancing the flame speed, nevertheless, at higher pressure ratio (pJ/p0 = 30), longer td conversely better promotes the deflagrated flame speed. This is because, at the condition of weak pressure ratio and long td, the abruptly burst of N2 JICF results in a prominent effect because of its dilution attribute, which prohibits the chemical reaction and the further development of a deflagrated flame. However, as the jet pressure tends to stronger, the corresponding turbulence is greater; the recirculation effect induced by robust JICF overcomes its dilution effect and gradually plays a more dominant role in the flame acceleration.