A joint experimental and numerical study of multiple hydrogen flames in a jet in crossflow configuration

Abstract

This work investigates multiple jets in crossflow (JICF) injection of hydrogen in a laboratory-scale canonical configuration in anticipation of the presence of this geometrical feature in future hydrogen gas turbine combustors. The experimental setup comprises a square cross-section plenum delivering a crossflow of air and a hydrogen injection plate delivering three hydrogen jets. To achieve a wide range of momentum flux ratios, three different injection plates with different hole diameters are employed for the hydrogen jets. In the first step, the schlieren technique is used to visualise the non-reacting flow with helium as a surrogate, followed by the study of pure hydrogen flames using OH ∗ chemiluminescence. The flames exhibit different dynamical behaviour, including a partial flame lift-off on the windward side at the higher momentum flux ratio. To further understand the flame and flow behaviour, in the second step, large eddy simulations (LES) of the experimental configuration are performed, which effectively capture the experimental observations in terms of jet and flame shape. It is seen from experiments and LES that at the highest momentum flux ratio, the jet penetrates further into the chamber, with most of the mixing taking place within a short region downstream of the jet. This leads to a compact flame that is stabilised farther from the inner wall. However, the higher momentum carried by the jets results in less intense mixing near the exit, leading to partial flame lift-off. As the momentum flux ratio decreases, the penetration of the jet diminishes, leading to reduced mixing. The delayed mixing leads to a longer flame anchored at the injection location, close to the inner wall. The combined insights from experiments and LES at various momentum flux ratios have shed light on flame stabilisation mechanisms in JICF configurations, offering guidance for the development of hydrogen-based combustion systems.