Low-order modeling of high-altitude relight of jet engine combustors

Abstract

A physics-based, low-order ignition model is used to assess the ignition performance of a kerosene-fueled gas-turbine combustor under high-altitude relight conditions. The ignition model used in this study is based on the motion of virtual flame particles and their extinction according to a Karlovitz number criterion, and a stochastic procedure is used to account for the effects of spray polydispersity on the flame’s extinction behavior. The effects of large droplets arising from poor fuel atomization at sub-idle conditions are then investigated in the context of the model parameters and the combustor’s ignition behavior. For that, a Reynolds-averaged Navier-Stokes simulation of the cold flow in the combustor was performed and used as an input for the ignition model. Ignition was possible with a Sauter mean diameter (SMD) of 50 μm, and was enhanced by increasing the spark volume. Although doubling the spark volume at larger SMDs (75 and 100 μm) resulted in the suppression of short-mode failure events, ignition was not achieved due to a reduction of the effective flammable volume in the combustor. Overall, a lower ignition probability is obtained when using the stochastic procedure for the spray, which is to be expected due to the additional detrimental effects associated with poor spray atomisation and high polydispersity.

Numerical Investigation of a Coupled Blow-Off/Flashback Process in a High-Pressure Lean-Burn Combustor

“…The effect of droplets on the flame structure during the evaporation process is not considered in this study. Although this effect could be important in general [47], previous studies [12,27] have shown that for the particular injectors used in this work most of the fuel evaporates before entering the flame region. Also, a very good match was observed in [12] between measured and computed SMD and spray velocities.…”

A laser-induced breakdown spectroscopy method to assess the stochasticity of plasma-flame transition in sprays

“…where X > 0, q > 0 are the parameters of the distribution that can be related to the statistical moments of the spray, e.g. d 10 and d 32 [27]. Alternatively, sometimes a modified Rosin-Rammler function, where (d/X) is replaced by (ln d/ ln X), is used to better fit the small-size range [28].…”

Coating roughness impact on the combustion chambers life of the turbo engines

“…Different types of combustion chambers have been developed in the past century and different fuels are used there. In aero-engine or gas turbine combustor design, complete combustion, 1-3 low total pressure loss, 4 stability, 5,6 freedom from flash back and flame out, 7,8 relightabality, 9,10 occupying a small space, and no hot spots [11][12][13] are desired, and many researches have been performed on these areas to have better designs.…”