Experimental study of the unsteady aerodynamics the compressor-combustor interface of a lean burn combustion system

To meet the technological challenges of lean burn, low emission combustion knowledge based design methodologies must be developed. This paper presents back-to-back, time-averaged and time-resolved aerodynamic measurements made using a unique state-of-the-art fully annular isothermal test facility incorporating a 1/2 stage axial compressor and a typical lean burn, low emission combustor geometry and either a clean or a strutted OGV/pre-diffuser system. The various measurement techniques employed (miniature five-hole probe, hot-wire anemometry, PIV) show a good level of agreement highlighting both the effect of including pre-diffuser struts and the notable unsteadiness present in the OGV/pre-diffuser system. The data presented provide the first evidence of the highly unsteady nature of the flow issuing from a pre-diffuser and potentially influencing the downstream external combustor aerodynamics.