Spray Combustion Modeling in Lean Direct Injection Combustors, Part II: Multi-Point LDI

Abstract

The multi-point lean direct injection (MPLDI) strategy, which incorporates several lean direct injection (LDI) modules, has been developed for low-emission aero-propulsion systems. There is a lack of information on MPLDI flow physics and spray characteristics. In extending previous work, this article investigates the reacting spray characteristics of an MPLDI system and makes an effort to highlight the salient features of this system, which enable low NOx combustion. The simulation approach and the numerical models applied and validated for the single-element LDI are used to compute the combusting spray in MPLDI. Simulations are performed under different inlet flow conditions to study the spray properties and combustion due to multi-swirler injection. The results illustrate small-sized drops and uniform distribution of drop diameter with increasing swirl, resulting in rapid fuel vaporization and mixing. In comparison with the single-element LDI, MPLDI creates smaller reaction zones and accomplishes a more uniform drop diameter distribution and a thorough mixing of fully vaporized fuel and air at a shorter distance from the fuel nozzles. Overall, the numerical results are able to explain the underlying features of the MPLDI technique, which primarily influence its NOx reduction performance.