Characterisation of the combustion performance of low emission fuel injectors with laser measurements

Abstract

This paper illustrates the utilisation of an optically accessible high-pressure sector test rig in combination with optical test methods as part of the development process of a lean injection combustion concept. First experimental results from a new single sector combustor are presented. The combustor allows the investigation of large burners for lean aero-engine combustion at full size and medium pressure up to 20 bar with wide optical access to the primary zone. Imaging and laser-based techniques are used to characterise fuel preparation, heat release and temperature. Gas analysis at the outlet of the combustor provides emission results, to which the flow field data can be related. The measurements focused on part load operation from idle to cruise, including pilot-only operation at idle to varying degrees of fuel staging at cruise. The circumferential homogeneity of the main fuel placement was also investigated. The measurements on the pilot injector demonstrated the influence of fuel loading on the pilot combustion at real operating conditions. Transition from attached to lifted flames was observed for different injector hydraulics but identical aerodynamics. The fuel staging variation showed the shift from a main combustion zone separated from the pilot to joint combustion zones and finally to combustion concentrated near the pilot. This global behaviour was linked to measurements of NOx and combustion efficiency. The measurement plane parallel to the combustor head revealed a near field periodicity of the fuel placement coinciding with vanes in the outer passage. Overall circumferential homogeneity increased with fuel loading. A first 3D dataset of temperature is presented, demonstrating the future potential to correlate different measurement variables, e.g. fuel concentration, temperature or velocity on arbitrary surfaces or volumes in the primary zone.