Mohsin M. Sies

Effect of diluted and preheated oxidizer on the emission of methane flameless combustion

In combustion process, reduction of emissions often accompanies with output efficiency reduction. It means, by using current combustion technique it is difficult to obtainlow pollution and high level of efficiency in the same time. In new combustion system, low NOxengines and burners are studied particularly. Recently flameless or Moderate and Intensive Low oxygen Dilution (MILD) combustion has received special attention in terms of low harmful emissions and low energy consumption. Behavior of combustion with highly preheated air was analyzed to study the change of combustion regime and the reason for the compatibility of high performance and low NOx production. Sustainability of combustion under low oxygen concentration was examined when; the combustion air temperature was above the self-ignition temperature of the fuel. This paper purposes to analyze the NOx emission quantity in conventional combustion and flameless combustion by Chemical Equilibrium with Applications (CEA) software.

Effect of Vertical Baffle Installation on Forced Convective Heat Transfer in Channel Having a Backward Facing Step

In this study, forced convective heat transfer is considered in channel over a backward facing step having a baffle on the top wall. Four different geometries with different expansion ratios and different type of baffles are numerically investigated. The study clearly shows that the geometry with expansion ratio 2 and solid baffle has the highest Nusselt number compared to other geometries. Considering both Nusselt number and skin friction coefficient for all four geometries clearly illustrated an increase in average Nusselt number by increasing the expansion ratio. This study clearly shows that mounting a slotted baffle at the top wall instead of a solid baffle caused a decline in average Nusselt number. It is also found that for geometry with expansion ratio of 3 and a slotted baffle on the top of the channel, skin friction coefficient in both bottom wall and step wall has its minimal compared to other geometries.

Comparison of eddy dissipation model and presumed probability density function model for temperature prediction in a non-premixed turbulent methane flame

Temperature distribution is predicted through numerical simulation of a turbulent non-premixed methane flame using the standard Eddy Dissipation Model (EDM) and a model based a presumed shape of probability density function (PDF) along with an equilibrium chemistry model. Results are validated against existing experimental data. Two models are compared to each other in terms of accuracy and their advantages and disadvantages are discussed.

Review of Numerical Studies on NOx Emission in the Flameless Combustion

Today one source of pollution emission in the combustion of fossil fuels is the formation of nitrogen oxides. To solve this problem many technologies have been introduced such as flameless combustion. Flameless combustion is of a great interest since it simultaneously provides higher thermal efficiency together with controlling the pollutant emission such as NOX. In this technology, the preheat temperature of the combustion air must be higher than the auto-ignition temperature of the reactant mixture. In this study, papers showing the numerical studies on the flameless combustion to reduce NOX emission are presented.

Main Steam Temperature Modeling Based on Levenberg-Marquardt Learning Algorithm

Main steam temperature is one of the most important parameters in coal fired power plant. Main steam temperature is often describe as non-linear and large inertia with long dead time parameters. This paper present main steam temperature modeling method using neural network with Levenberg-Marquardt learning algorithm. The result of the simulation showed that the main steam temperature modeling based on neural network with Levenberg-Marqurdt learning algorithm is able to replicate closely the actual plant behavior. Generator output, main steam flow, main steam pressure and total spraywater flow are proven to be the main parameters affected the behavior of main steam temperature in coal fired power plant.

Effects of CO2 Dilution on the Premixed Combustion of CH4 in Microcombustor

A numerical study on premixed combustion of CH4 + CO2 + Air in two dimensional is done. Parameters of inlet velocity and temperature of fuel and combustor geometry and size are considers the same but the CO2 dilution rate changes. Results of this simulation shows that while the CO2 dilution rate increases, flame temperature and velocity decrease. There is a limitation for increasing of CO2 in the mixture. If amount of CO2 in the mixture goes beyond the 47.7%, the fuel will lose its ability to be ignited and thus there will be no flame in the combustor. In addition, knowing the maximum temperature of flame may help to analyze the combustion process and choose suitable material in manufacturing the micro combustor.

Analyzing the Effect of Free Stream Turbulence on Gaseous Non‐Premixed Flames

The effects of free stream turbulence on non‐premixed flames are numerically analyzed. The Spalding eddy dissipation mathematical model is used to control the reaction rate by the large‐eddy time scale. The turbulence energy production and dissipation rates are simulated by the κ—e turbulence model in order to investigate the dependence of the combustion properties on free stream turbulence. The reacting NS equations were spatially discretized and solved through a finite volume scheme and a decoupled pressure‐velocity approach, respectively. The flame was assumed to be steady‐state, two dimensional and axisymmetric. The reported results include the velocity, temperature and turbulent reaction rate along the flame propagation field. It is found that the increase of free stream turbulence intensity reduces the reaction zone significantly, hence, induces the flame extinction process.

Effects of Firing Mode on the Performance of Flameless Combustion: A Review Paper

Flameless combustion is of a great interest since it simultaneously provides higher thermal efficiency together with controlling the pollutant emission such as NOX. This technology has been used to provide large energy savings in power system and industrial heating applications. In this technology, the preheat temperature of the combustion air must be higher than the auto-ignition temperature of the reactant mixture. In this review, papers concern the effect of firing mode to reduce pollutant emissions such as NOX emission and combustion efficiency for flameless combustion were reviewed. Summaries on the influences of the firing mode in the flameless combustion were presented, discussed and analyzed. The review concludes that all the previous studies have asserted that a parallel firing mode gives much lower pollutant emissions and high efficiency compared with staggered and counter modes.

Highly-resolved large eddy simulation of the nonreacting flow in an asymmetric vortex combustor

In this paper, we present a computational investigation of the nonreacting flow structure inside a novel asymmetric vortex combustor that was recently proposed by the authors. Large Eddy Simulation using the Smagorinsky-Lilly subgrid turbulence closure has been used to study such flow. A computational grid of 2.22×106 cells was used to ensure that the resolved turbulence kinetic energy is fairly more than 80% of the total turbulence kinetic energy budget. The flow was found to exhibit a central recirculation zone, and two secondary recirculation zones in the asymmetry regions. The vortex structure was found to be a completely forced vortex field. The effect of turbulence on the size and structure of the statistically averaged mean flow phenomena has been analyzed as discussed.

Simulation of corrected mass flow and non-adiabatic efficiency on a turbocharger

The aim of this project is to evaluate turbine’s performance based on its actual condition. Holset H3B nozzles turbine geometry was used as simulation model. Turbine’s actual working condition was simulated using finite volume method (FVM). Three-dimensional Navier Stoke equations with heat convection loss via turbine volute are solved. The parameters studied are corrected mass flow and turbine’s efficiency at different heat transfer coefficients. Temperature difference within turbine’s volute is the major factor that deteriorates turbine’s efficiency. It is found that the higher the heat transfer coefficient, the lower turbine’s efficiency will be.