(A) study on the inverse analysis of diffusion-controlled turbulent combustion phenomena in cylindrical combustor

Abstract

In this thesis, the repulsive particle swarm optimization (RPSO) method which is one of high performance global optimization algorithms is employed as an efficient, robust and stable inverse analysis method rather than existing developed methods to various inverse thermal problems encountered in engineering which are highly non-linear, non-monotonic, or a very complex form. For inverse heat problems, three simple inverse heat problems with one-dimensional heat conduction, two-dimensional convection, and one-dimensional radiation cases are investigated to estimate unknown parameter values to verify the feasibility of the RPSO method. From the results, the RPSO method shows that it has superior advantages in terms of easy implementation and low computational costs because conjugate gradient method generally requires to solve additional complex mathematical equations such as the sensitivity problem and adjoint problem at the same time. Also, the RPSO method is applied to inverse radiation analysis in estimating the wall emissivities, absorption and scattering coefficients in a 2-D absorbing, emitting and scattering irregular medium with measured temperatures. A total of six cases are investigated depending on the combination of unknown parameters to compare the overall characteristics of RPSO with PSO and HGA. Based on the results, it is sufficiently observed that the RPSO has better computational performance than the other two algorithms. To extend the applications of an inverse analysis from traditional heat transfer problems to new engineering area, a practical turbulent diffusion flow in a cylindrical axisymmetric combustion chamber is investigated with or without a thermal radiation effect. The combinations of unknown inlet mass fractions and inlet velocities of methane and oxygen in fuel/oxidizer are estimated successfully from given temperature measurements by the present RPSO method although a thermal radiation effect is involved.