Design Optimization for Enhanced Fuel Mixing and Reduced Combustion Instability: Enhancing Swirler Performance of a Small Turbojet Engine Combustor

Aero-engine performance is becoming an increasingly regulated aspect in aerospace indus- tries with tighter restrictions on emissions, greater expectations for efficiency and thrust as well as broader requirements for the range of the operating flight envelope. With an increasing consciousness toward these factors during the design of combustors, research led development and improvement of every single aspect of the combustor design needs to be considered in this modern era of aerospace technology. A major contributor to such performance enhancement is the design of flow swirlers used to induce central re- circulation zones in the primary fuel/air mixing region. In the current study, the effect of modification to a swirler’s vane blade angle on mixing effectiveness and combustion stability is investigated, using flow properties such as turbulent kinetic energy, fuel dis- tribution and pressure losses as a measure of combustor performance. The study takes a sensitivity analysis approach and makes use of an existing combustor design that acts as a benchmark for verification of results. A cold flow computational fluid dynamics anal- ysis is used to test the effect of blade angle modifications based on a ‘cause and effect’ methodology. The computational fluid dynamics model is validated against experimental data from a similar combustor. It was found that optimal fuel/air mixing occured in a 70? blade angle swirler however large pressure losses and excessive vortex shedding directly behind the center body indicated a strong likelihood of combustion instability. Good fuel atomisation through strong shear layers and excellent pressure recovery seen in a 30? blade angle swirler was accompanied by poor fuel/air mixing. A swirler design featuring 50? blade angles was found to be the optimum, with good fuel atomisation, stable recir- culation zones, promising flame anchoring potential, dispersive but orderly homogenous fuel/air mixing and desireable pressure recovery characteristics.Flight Performance and PropulsionFlight Performance and PropulsionAerospace Engineerin