Influence of jet velocity and heat recuperation on the flame stabilization in a non-premixed mesoscale combustor: An exergetic approach

Abstract

An experimental and numerical model to determine the exergy balance based on flow availability and availability transfer in the process of liquefied petroleum gas (LPG)/air combustion in mesoscale gas turbine combustor is developed to elucidate the second law efficiency and total thermodynamic irreversibility. In terms of developing an energy and exergy-efficient combustor design, the present work highlights the influence of vortex shedding and recirculation in the volumetric entropy production and the exergy efficiency. It is performed in a heat recuperative high-intensity LPG-fueled mesoscale combustor for mini-gas turbine applications. The combustor is operated at different thermal inputs ranging from 0.2 to 1.0 kW under range of equivalence ratios of φ = 0.4-1.23. The Favre-averaged governing equations are solved by using finite volume-based approach. The standard k-ϵ turbulence model with modified empirical constant, Cϵ1 = 1.6, is considered to model the turbulence quantities. The volumetric reaction-based eddy-dissipation concept model and a reduced skeletal model (50 species and 373 reactions) are used for turbulence-chemistry interaction. The design methodology, total volumetric entropy generation, destructive exergy due to thermodynamic irreversibility, exergy efficiency, flow recirculation, and mixing characteristics (reacting and non-reacting) are reported. The entropy generation rate due to thermal conduction is approximately 50% of the total entropy generation, while its contribution percentage due to chemical reaction is the smallest. The exergy efficiency reaches its peak with η I I = 79.41% at 1.0 kW under fuel-rich condition, while its minimum value of 41.49% is obtained at 0.2 kW under fuel-lean (φ = 0.8) condition.