Because of restriction of fossil fuel reservoirs and increasing it ?s price, energy saving has become very important in all of the world. Today, different industries effort for energy saving. Over the last two decades, significant progress has been made in the development of computational fluid dynamics (CFD) based models to simulate the performance of practical combustion systems. In this computational study, three turbulent models and two radiation models has been assessed in predicting a turbulent, non-premixed combusting swirling flow of the type frequently found in practical combustion systems. The predictions are compared against the experimental data of mean axial and tangential velocities, gas temperatures and oxygen concentration collected in a 400 kW semi-industrial scale combustor fired with coke-oven gas using an industry-type swirl burner and a combustion flow with bluff-body burner.CFD studies using Fluent code were carried out for three cases; Standard k-? Model, renormalization group k-? Model (RNG) and Reynolds Stress Model (RSM). The model results from these three cases are compared with each other and with the experimental results. Three turbulent models coupled with PDF/mixture fraction combustion model were applied and the predicted results were compared. Radiation heat transfer was modeled by the discrete ordinates model (DO) and p1. The numerical simulation has been performed with a triangular and unstructured mesh composed of 40,000 cells and the method for this study is axisymmetric swirl. The absorption coefficient of the gas mixture is calculated by the means of a Weighted-Sum-of-Gray-Gas model (WSGGM). The algorithms PRESTO and SIMPLE have been used for pressure interpolation and coupling of pressure and velocity, respectively.The overall agreement between the measurements and the predictions obtained with both the k–? and Reynolds-stress turbulence models are reasonably good. The levels of gas temperature and oxygen concentration in the internal recirculation zone and the enveloping shear region are on the whole better predicted by the Reynolds-stress model.Three-dimensional mathematical model has been developed for the simulation of flow, temperature and concentration fields in the radiation section of furnace 101 of Isfahan refinery. The calculations employ a composition probability density function (PDF) approach coupled to the commercial CFD package, FLUENT. In this work preheating of entrance air has offered as a practical way to increasing heater efficiency. Another practical way for increasing efficiency is reducing percentage of excess air. Keywords : Swirl combustion, Combustion flow with bluff-body, Turbulence, Radiation.
