Simultaneous 5 kHz OH-PLIF/PIV for the study of turbulent combustion at engine conditions

Abstract

Simultaneous measurements of velocity and scalar fields were performed in turbulent nonpremixed flames at gas turbine engine-operating conditions using 5 kHz particle image velocimetry (PIV) and OH planar laser-induced fluorescence (OH-PLIF). The experimental systems and the challenges associated with acquiring useful data at high pressures and high thermal powers are discussed. In this work, a wide range of operating conditions were studied, with a maximum pressure and thermal power of 1.8 MPa and 950 kW, respectively. In the PIV measurements, the high thermal power conditions were shown to cause significant defocusing of the particle images. This was the result of variations in the optical refractive index of the gas which were caused by strong temperature gradients within the inner structure of the flame. High flame luminosity also led to decreased SNR with increasing flame power. The OH-PLIF measurements did not show indication of strong laser sheet absorption at any condition tested. However, a decrease in the peak SNR was observed with increasing chamber pressure. An analysis of the true measurement resolution with respect to the scales of the flow is also given. Based on the resolved scales, the present dataset was used to study the time-averaged flow structure and its effect on flame behavior. Heat release conditioned flow statistics were studied to elucidate the flow–flame interactions in high-power flames.