Safran Helicopter Engines has recently patented the spinning combustion technology in which the burnt gases from one injector travel tangentially along the combustor annulus towards the neighboring injectors. Compared to conventional designs, the new kerosene injection systems are dedicated to improve air/fuel mixture ignition but also to further reduce NOx and soot particle emissions. Experimental studies are performed on these fuel injectors in a high-pressure/high-temperature combustion facility designed by the CORIA research laboratory. This test bench is able to reproduce the same operating conditions encountered in a helicopter combustor over the entire range of nominal operating conditions and has large optical accesses for the implementation of laser-based diagnostics. In the current paper, we present results concerning flame structure and NO formation in the primary zone under pressure conditions of up to 14 bar, using simultaneous OH-PLIF, NO-PLIF and kerosene-PLIF laser diagnostics. These experimental studies were supplemented by high-speed PIV measurements. A good spatial correlation between the distribution of liquid and vapour kerosene and the location of the flame front was observed. Depending on the operating conditions in terms of fuel/air ratio, mass flow rates and pressure, different flame structures resulting from the modification of the interaction between fuel injection and aerodynamics are observed. Furthermore, it was found that the Zeldovich pathway mainly controls the formation of NO in the vicinity of the flame front. In addition, the effects of FAR and pressure also have a significant impact on NO production. All these results are now intended to serve as a comprehensive validation database for the development and testing of high-fidelity LES tools dedicated to the simulation of reactive flows in aero-engine combustion chambers.
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