Excess Air Factor Research Articles

Design optimization and CFD evaluation of a volute swirl burner with central gas supply

The reasonable design and optimization can be useful tools to solve issues in several industrial applications. Since it is time-consuming and costly to do the experimental performance assessment using various equipments, computational fluid dynamics (CFD) with suitable models has been widely used due to the good agreement with experiments. This paper presented a universal design calculation method of a volute swirl burner with central gas supply. Then, CFD simulations with standard k–e model, under non-reacting and reacting conditions, were carried out to verify the design feasibility. The mixedness of gas/air under non-reacting condition was evaluated from the perspective of normal distribution in statistics and checked by the designed excess air factor. A parametric study for various mixing section lengths and outlet diameters of the burner block was conducted to investigate their influence on the central recirculation zone and the temperature distribution. Simulation results show good agreement with empirical formula calculation. The gas and air have been mixed uniformly around the location that is 60 times of the gas orifice diameter. Additionally, an enlarged recirculation zone with increased recirculation strength can be formed with the increasing mixing length and block outlet diameter. In combustion simulation, the longer mixing length improves the flame stabilization but makes the combustion center move to the upstream of the burner due to the strengthened recirculation zone. The larger outlet diameter of the block stretches the flame and moves the high-temperature zone inside the flame to the downstream of the block wall.

Parametric study for reducing emission characteristics using different computational schemes

The present study numerically predicts emissions (NOx & CO) characteristics issued from swirl burner using different computational schemes adopted in ANSYS 17.2. Various turbulence models were tested and compared in a structured grid having an average skewness of 0.04. RSM model shows the best results in predicting the central toroidal recirculation zone for such severe swirling flow (S>0.6). Three different schemes of combustion modeling were also tested and compared. Flamelet PDF model was preferred among other combustion models for its potential to consider non-equilibrium chemistry, where its choice was recommended form many studies in the literature. A radiation heat transfer analysis was carried out using P1 radiation model to account radiation effects in estimating NOx and CO concentrations. The effect of varying swirl ratio, excess air, diluting fuel with N2 and CO2, oxidizer preheating, and oxidizer composition on emissions (NOx and CO) reduction strategy concluded that increasing the swirl number, excess air factor, and (N2 and CO2) mixing ratios have a considerable influence on NOx and CO emissions reduction. While increasing the preheating temperature, and the oxidizer Oxygen concentration leads to an increase the NOx and CO emissions. Hence, a considerable reduction in NOx and CO formation was apparently observed by lowering the peak flame temperature less than 1800 K. These predicted outcomes are in agreement with measurements data published in the literature.

Stage fuel combustion as an effective method to decrease metal losses in reheating furnaces

In the process of metal reheating before rolling, its losses as a result of high temperature oxidation (metal losses) reach 1–2%. At that the heat transfer for the flame jet to the metal decreases, which results in an increase of fuel consumption and increase of danger of surface defects formation. One of the ways to decrease metal losses in the form of scale during heating due to the organization of the stage burning of fuel considered. This principle implies creation of a neutral or reducing atmosphere of the furnace in the end zones in the direction of metal movement. This is achieved by supplying less amount of air to these zones than necessary for the complete combustion of the fuel. Afterburning of fuel occurs in the first zones of the furnace. Thus, the amount of air required for complete combustion of the fuel does not change and there is no increase in the formation of CO emissions. The technology implementation has been carried out on a reheating furnace equipped with instruments for monitoring the atmospheric composition along the entire furnace length. The values of the excess air factors were varied within the existing process schedule. The application of the stage mode on three walking beam furnaces of a wide-strip hot rolling mill made it possible to reduce metal losses to scale by an average of 9.3% (1.3 kg/t). At the same time, there were no cases of deterioration of other parameters of the heating process, such as fuel consumption, heating quality, formation of hard-to-remove scale.

The calculus of the temperatures in the characteristic points of the gasoline direct injection engine cycle

Based on an own model, the authors have realized the analytical calculus of the temperatures in the characteristic points of the thermodynamic cycle for a GDI engine. These temperatures were calculated depending on the engine’s rotational speed and on the environmental temperature (considered to be equal to the one in the intake valve port) and for an excess air factor λ=1. The first step was the development of the mathematical model of the engine’s cycle. The model includes the presentation of the initial data for the thermal calculus and the correlation between the expressions of the parameters in order to develop the computing programs. The calculated data were compared with experimental data acquired at environmental temperature, at maximum power and at the rotational speed corresponding to the maximum power (full load). The results show that the proposed model is accurate enough to be a useful tool for the study of GDI engines.

Operating limitation and degradation modeling of micro solid oxide fuel cell-combined heat and power system

The micro Solid Oxide Fuel Cell-Combined Heat and Power (SOFC-CHP) System is one of the most promising technologies of distributed generation and has been commercialized in Japan and Europe. However, the performance degradation of an SOFC stack still exists, causing the ratio of power and heat to change and the Joule heat to increase in the stack. This phenomenon should not have been neglected. A zero-dimension SOFC model including basic Nernst, ohmic, activation and concentration voltage loss was used to simulate the micro SOFC-CHP system, and a degradation model was also applied to modeling the power change with respect to operating time in different situations. Both of the models were verified by real stacks experiment data and the effectiveness was proved in system-level modeling. Three key operating parameters of the system were promoted: stack current I, excess air factor α and fuel utilization Uf. Given the safe temperature ranges of an SOFC stack, combustor and reformer, the most appropriate parameter range was illustrated to be limited in a shape of a small triangle. Within the safe parameter range, while the excess air factor α was fixed at 2.64, the electrical efficiency reached a maximum 44.9% (HHV) at 120 A, while the electric power output of SOFC and hot water were both 5.58 kW. As for the dynamic modeling, by comparing constant current, constant voltage and constant power three operating patterns, results showed that the constant current pattern had the longest lifetime and the constant power pattern followed.

Experimental research on operational process of petrol engine on lean air-and-fuel mixtures on the edge of combustion knock

The results of experimental research are provided regarding the operational process of VAZ-21124 petrol engine with the compression ratio of 12.0 on lean air-and-fuel mixtures with various values of heating the air charge at intake, and of the ignition advance angle. In the course of performing the experimental research, the pressure of gases in the engine cylinder was registered, as well as the temperature of the air charge in the intake manifold, the ignition advance angle, and the concentration of toxic components in the exhaust gases. The obtained pressure indicator diagrams were processed using a special program for determining indices of the operating cycle, cycle consumption of fuel and air, air excess factor, and heat release rate. The obtained cycle consumption of fuel and air, as well as the air excess factor were compared to the ones measured experimentally. As a result, possible boundaries of leaning of air-and-fuel mixture were revealed, as well as the values of heating the air charge, and of the ignition advance angle, for intensification of the process of combustion till the knock moment. When the air charge temperature at the intake was raised from 29°C to 112°C;, the ignition advance angle retarded from 35.5 to 15 degrees, and the air excess factor decreased from 1.55 to 1.41 respectively.

Experimental Investigation of the Stability Limits for a Low-Emission, Two-Stage Combustor

Results are presented of the experimental investigation of gaseous fuel combustion in a combustor comprising two zones in series each of which has its own burner unit (BU). The first burner unit (BU1) is a conventional one for low-emission combustors. It contains swirlers, a fuel-air mixing zone, a pilot burner, and a main burner. BU1 is fed with a premixed fuel-air mixture (FAM). The second burner unit (BU2) is located downstream along the flow, behind the first combustion zone. It is supplied with gaseous fuel (i.e., natural gas) without premixing with air. Diffusion combustion occurs in the second zone. The potential was studied for extending the stable operation range of the first combustion zone to the range of low excess air factors by creating radial nonuniformity in the FAM concentration at the BU1 outlet. This is accomplished by feed air in one hole in the fuel tubes above the vanes of the main burner swirler. The best FAM concentration at the first stage minimizing NOx and CO emission during joint operation of two combustion stages installed in series was determined. The results of the experiments with BU2, which is a thick hollow disk with a nozzle-shaped orifice with holes in the bore surface for fuel injection, are presented. The experiments were carried out with a model combustor in the test facility at OAO VTI.

Experimental research of mitigation strategy for high-temperature corrosion of waterwall fireside in a 630 MWe tangentially fired utility boiler based on combustion adjustments

With the extensive use of the staged combustion systems to meet the stricter standard for NOx emission, the high-temperature corrosion caused by reducing atmosphere has become much serious. In this study, seven groups of industrial-scale experiments of combustion adjustments were conducted in a 630 MW tangentially fired utility boiler to study the effects of different operating conditions on the high-temperature sulfur corrosion, NOx emission and boiler efficiency. The experimental results showed that the reducing atmosphere in the vicinity of the waterwall was mainly controlled by distributions of O2 concentration and combustion temperature. For alleviating the reductive gases, the increase of the O2 concentration near the waterwall was much effective but more vigorous combustion with the higher temperature was negative (except increasing the CFS air). The overall excess air factor, the distribution of DFS air, the flow rates of CFS air, CCOFA and SOFA had great effects on the reducing atmosphere near the waterwall while the impacts of the flow rate of primary air and coal fineness were unobvious. Through the comprehensive assessment, the optimal operation parameters which reached the balance among the low high-temperature sulfur corrosion, low NOx emission and high boiler efficiency can be obtained.

Experimental study of methane reforming with products of complete methane combustion in a reformer filled with a nickel-based catalyst

An experimental investigation of methane reforming with flue gases obtained by combustion of methane with an excess air factor of 1 is carried out over a nickel-based catalyst. A set of experiments was conducted to understand the effects of operational parameters such as temperature, pressure, residence time and inlet gas composition on the conversion of the reactants. In addition, two shapes of catalysts such as a solid cylinder and ring were used in experiments. It is found that at the residence time above 4 kgcat s/mol the methane conversion has a value close to equilibrium. A change in pressure from 1 to 5 bar has a negligible effect on methane conversion, not more than 1–2% for various operating parameters. It has been experimentally determined that the use of an extended surface catalyst gives a higher methane conversion at a fixed catalyst weight. Therefore, for a fixed residence time, the methane conversion over a Raschig rings is 1–2% higher than over a solid cylinder. The steam addition to the inlet reaction gas mixture increases the methane conversion significantly; especially at the temperature range from 500 to 800 °C.

ИССЛЕДОВАНИЕ ОСОБЕННОСТЕЙ СГОРАНИЯ В КАМЕРЕ СГОРАНИЯ ПЕРЕМЕННОГО ОБЪЕМА

The paper covers the study of special aspects of the application of ionization sensors intended for determining the characteristics of flame propagation (flame propagation velocity and the width of chemical combustion reactions area) in the variable volume combustion chamber. The review of contemporary methods of study of the process of hydrocarbon fuel combustion in piston engines showed the perspectivity of ionization sensors application. On a single-cylinder engine, the authors experimentally obtained and studied the main parameters of fuel combustion using the specially developed ionization sensors designed for identifying the characteristics of flame propagation when changing temperature, pressure, turbulence, and the combustion chamber volume in a wide range within several milliseconds. The variance of ion current, flame propagation turbulent velocity and the width of combustion chemical reactions area are determined depending on the fuel-air mixture composition when changing its physical and chemical properties due to the addition of hydrogen. It is shown that the change in the flame propagation turbulent velocity when adding hydrogen is caused by the increase in its normal component, and the width of turbulent combustion area is linearly related to the ion current value and its variance reflects the intensity of chemical combustion reactions. It is identified that despite the change in the excess air factor, the hydrogen concentration in fuel, and the engine speed rate, the linear dependence of flame width on the flame propagation turbulent velocity in the second combustion phase remains: the velocity increase corresponds to the flame width narrowing.

Feasibility assessment for replacing rapeseed oil by selected vegetable oils in diesel engine

To study the feasibility of replacing rapeseed oil used as fuel of diesel engines by other vegetable oils, comparative studies were conducted of rapeseed oil combustion process with palm and sunflower oil. The tests have been carried out for the fuel injection pressure:70, 100 and 135 MPa, pressure in chamber equal to 0.5, 0.7 and 0.9 MPa and the excess air factor from 1.25 to 5 (1.25; 2.50; 3.75; 5.00). The progress of the combustion process was studies for four temperature levels: 350°C, 425°C, 500°C and 575°C. The following were considered as analysed parameters of the process: self-ignition delay, burning time and pressure growth. Based on the results of the conducted research, it is recommended to use palm oil to replace rapeseed oil as a fuel in a diesel engine. In addition, it is possible to use sunflower oil for this purpose. Characteristics of the rapeseed oil combustion process is most similar to process of palm oil. Moreover, the parameters of the palm oil combustion process are similar to those characterizing diesel (at temperature equalling to 575°C and pressure of 0.7 MPa and 0.9 MPa). Sunflower oil was characterized by lower maximum combustion pressure, longer autoignition delay (after 0.1s in every case) compared to other tested vegetable oils.

Исследование режимов работы и методика теплового расчета жаротрубно-дымогарного котла мощностью 3 МВт

The article presents the results from studying the fire-tube boiler operation mode and describes the heat transfer processes occurring in it. The boiler design characteristics are given: specifically, the flame tube length and diameter are 3.2 m and 0.926 m, respectively. An adequate boiler analysis model has been developed, which simulates the heat transfer processes in the boiler using the Boiler Designer software package for computer-aided designing of boilers. The boiler efficiency is 90.92% in firing diesel fuel with a heating value of 42 705 kJ/kg with a flowrate of 0.278 t/h and an excess air factor of 1.37. Recommendations for carrying out thermal design calculations of the fire-tube boiler and further tasks of its research are given. The results obtained from experimental and theoretical investigations are compared with each other. It is shown that the design calculation of a small-capacity fire-tube boiler cannot be carried out strictly in line with the standard boiler unit thermal design method. In accordance with this method, the temperatures at the furnace and boiler outlets should be equal to 1221°C and 222°C. According to the experimental results, the flame tube and the flue tubes receive a significantly larger amount of heat. According to the recommendations, the furnace outlet temperature should not exceed 1200°C. The boiler test results have shown that the flue gas temperature was 195°C. An assessment of the thermal analysis output data has shown that a convection heat transfer component exists in the flame tube, which accounts for up to 30% of the total heat absorption.

Research on characteristics and effects of combustion performance by amplified ignition energy in CVCC system

This study was conducted to analyze the flame characteristics, which is generated through the combustion process according to air/propane mixture ratio and initial pressure as well as increasing the area of flame kernel generation by connecting high capacity capacitor to a standard ignition device. The experiment method involved constant volume combustion chamber system featuring a standard ignition device connected to amplified ignition device and the flame kernel and flame propagation were observed through the spark generated between the electrodes of spark plug. Also, ANSYS Fluent program was used to suggest interpretive results in order to analyze the characteristics of chemical reaction generated within the flame. Experiment conditions included initial pressure being configured at 2, 3, and 4 bar along with air/propane mixture ratio configured at excess air factor (λ) = 1.0, 1.2, and 1.4. Experimental results showed that amplified ignition increased the flame kernel generation compared to standard ignition and was able to decrease the rate of loss for flame propagation speed compared to that of standard ignition as initial pressure and excess air factor increased. In conclusion, the amplified flame can reduce flame instability by increasing the reaction zone rather than the standard flame even if the initial pressure increases. In addition, it is considered that the thermal expansion on the flame front can be increased by the amplification of ignition energy.

Combustion of Lean Hydrogen-Based Mixtures in a Spark Ignition Engine

In this paper, the results of an experimental and modeling study of the combustion of lean mixtures based on hydrogen in a spark ignition engine are presented. A hydrogen and a hydrogen (90 vol %)-methane (10 vol %) mixture with air excess coefficients of 1.4–3.0 were used as fuel. “Back flashes” in the intake manifold were experimentally observed when the hydrogen-air mixture was burned at the air excess coefficient of 1.4. At large air excess coefficients, the key indicators of the engine performance are determined by using the experimental indicator diagrams. The efficiency indicator for hydrogen-air mixtures was 30–32%. The highest efficiency of 37% was obtained by using an earlier ignition in mixtures with methane addition. A weak dependence of the efficiency on the air excess coefficient was found. The major qualitative relationships obtained experimentally were supported by the performed 2D numerical simulation of the dynamics and combustion of mixtures under experimental conditions. Incomplete hydrogen combustion of up to 60% is observed at an air excess factor of 3.0.

INCREASING THE EFFICIENCY OF INTERNAL COMBUSTION ENGINE FOR LOW-TONAGE SHIPS BY ADDING SYNTHESIS GAS

When using alternative fuels in ICE, it is first of all necessary to take into account their physicochemical properties, which introduce significant adjustments to the way the work process is organized and significantly affect the effective and environmental performance of the engine and the entire power plant as a whole. Presented are the results of studies of the engine operation 4 × 10,16 / 9,1 with spark ignition and external mixture formation when working on ethanol with synthesis gas additives. Obtained indicator charts and diagrams of gas temperature changes in the cylinder of the engine when working on ethanol and with the addition of synthesis gas. It is established that an increase in the indicator efficiency of a spark ignition engine by 10.5% is achieved with a mass addition of synthesis gas in ethanol of 1...10% due to an increase in the excess air factor α to 0.98...1.2 when combustion of a mixture of ethanol and synthesis gas (for ethanol - 0.8...0.95), which leads to a reduction in heat losses, a decrease in the temperature of the exhaust gases and a reduction in emissions of toxic substances, while an increase in the amount of the synthesis gas additive leads to increase in the indicator efficiency of the engine. It is proved that the addition of synthesis gas to ethanol reduces the total mixture burning time by 45% and improves the environmental performance of the engine.

INFLUENCE OF CHARACTERISTICS VORTEX BURNER FOR HEAT TRANSFER EFFICIENCY IN THE FURNACE BOILER

In Ukraine, a significant number of domestic and industrial boilers are in operation. In this paper, we present the results of a numerical study of the processes of burning gaseous fuels in a furnace of a steam water-tube boiler DE-10/14. The burner device GMG-7 with a capacity of 728 m3/h of natural gas provides a swirling short and wide torch. The fuel-air mixture is formed by premixing 15% of the air, with a primary twist factor n = 2.4, and a secondary burner twist ratio n = 1.6, and an excess air factor αa = 1.10. The option of installing blades in the primary air duct with an angle φ1 = 45° was considered, and in the secondary air channel with an angle φ2=60°. The burner embrasure is conical with an opening angle of 60°. Twist of primary and secondary air – one way. As a result of the research, the temperature and velocity distributions of gases in the combustion chamber, the density of heat flows on the screen tubular surfaces, and the concentrations of the combustion components were determined. The mathematical model of radiation-convective heat transfer in the gas path of the boiler is formed on the basis of the Reynolds-averaged Navier-Stokes equations with allowance for gravity and neglect of compressibility. The model is the equation of continuity, momentum transfer, energy and chemical components of the gas mixture recorded in a stationary form. The equations are closed by the Newton law for the pressure tensor, the Fourier law for the heat flux, the Fick law for the mass flow, the Clapeyron-Mendeleyev law for the thermodynamic state of the gas mixture, the equations of the Launder-Spaulding turbulence model and the Magnusen-Hertager turbulent combustion model. The simulation is performed by the control volume method. At a slope angle of the blades of the register φ2=60° in the secondary air flow path and φ1 = 45° in the primary air duct, a wide opening of the V-shaped flame near the cutoff of the burner at a distance of 0.5 to 0.6 m is observed. Combustion of the gas – in narrow jets of the open torch at a distance of 1.0 – 1.5 m. The temperature of the gases in the streams of the torch is about 1500 – 1700°C. In this case, narrow jets move near the screen surfaces of the heat exchange tubes. It is established that the structure of the flame at the angle of installation of the blades φ2 = 45° is symmetrical and stable, and the dimensions of the torch correspond more to the geometry of the combustion volume. At the same time, no flare is observed on the screen side surfaces and the bottom of the furnace, tightening the torch in a convective beam. However, the temperature of the gases and the density of the heat flow are not high enough – the average values are about q=100 kW/m2 (at qcp = 76.8 kW/m2).

Studying the Aerodynamics of the TPP-210A Boiler Furnace When It Is Shifted to Operate with Dry-Ash Removal and Vortex Fuel Combustion

To reduce the amount of nitrogen oxide emissions and achieve more reliable operation of the TPP-210A boiler, a process arrangement for firing Grade TR Kuznetsk coal that involves using straight-flow burners and shifting the boiler from slag-tap to dry-ash removal is developed. Owing to a large burner downward slope angle and special arrangement of burners and nozzles, four large vertical vortices rotating in opposite directions are produced in the furnace lower part, as a result of which the combustion products dwell for a longer period of time in the burning zone and more complete fuel combustion is achieved. For verifying the operability and efficiency of the proposed combustion arrangement, investigations on a boiler furnace physical model were carried out using a technique for visualizing fuel jets and secondary and tertiary overfire air jets. The fuel jet temperature boundaries in the course of jet propagation in the furnace model are also determined. The study results have shown that staged fuel combustion will be set up with using the proposed arrangement of burners and nozzles. In addition, large vertical vortices produced in the furnace lower part will help to achieve more efficient use of the dry bottom hopper heating surfaces, due to which lower coal combustion product temperature in the furnace upper part and smaller content of combustible products in fly ash will be obtained. Owing to low values of air excess factor at the pulverized coal burner outlet and gradual admission of air into the vortex zone through a few nozzles with intense inner recirculation of combustion products to the jet initial section, staged combustion of pulverized coal and low nitrogen oxide emissions will be secured. Owing to expansion of fuel jets, a rapid growth of mass in the fuel jet is achieved, which is obtained both due to ejection of the jet itself and due to forced admission of hot fuel gases from other jets. Investigations carried out on the physical model have confirmed that the proposed combustion arrangement features high efficiency and that a low content of nitrogen oxides in flue gases is obtained.

Analysis of MSW Combustion Temperature in a Hot Water Boiler with the Low-Capacity

The paper analyzes the combustion temperature of solid waste in a small-capacity hot-water boiler with a great depending on the humidity of the solid waste, the excess air factor, the temperature of the air supplied to the combustion and the amount of heat taken and the range of parameters that provide the required combustion temperature is 900 ... 1100 ° C, which provides complete destruction of organic waste substances in the waste, but does not lead to ash melt and the formation of sprays. It is concluded that the necessary temperatures are provided for a wide range of regime parameters and the humidity of solid waste. But selection of heat in the boiler leads to a significant decrease in the combustion temperature. Therefore, in boilers for burning low-power MSW, it is necessary to constructively separate the combustion zone and the heat extraction.

Calculation analysis of the effect of uneven distribution of solid fuel on burners on ecological safety of boiler plants of TPPS

Ensuring environmental safety for energy companies in accordance with the requirements of Federal Law No. 219 of 21.07.2014 is a top priority task today. Experimental studies and industrial experience show that one of the main factors for the formation of virtually all toxic fuel combustion products in boiler plants is the ignition conditions in each burner of the furnace: the fuel-air ratio in the ignition zone, the proportion of primary air, the ratio between the secondary and primary air velocities, etc. However, according to the current regulations, the calculation of emissions of fuel oxides of nitrogen, as well as benz(a)pyrene, is based on averaged values for all burners of the furnace, and the influence of the most important factor — the uniformity of the distribution of fuel and air over the burners — on their formation is not taken into account.In the work presented, a calculation analysis is performed of the effect of uneven distribution of solid fuel on the burners of boiler plants on emissions of nitrogen oxides, as well as benz(a)pyrene, in combustion products. A calculation procedure has been developed and the dependences of the change in NOx emissions on the nonuniformity of the Δg distribution, the average air excess factor in the αG burners, the number of burners and the dust distribution models have been obtained. It is shown that with the value of the parameter Δg <10%, the uneven distribution of fuel has practically no effect on emissions of nitrogen oxides and benz(a)pyrene, and Δg5 (at which the increase in NOx emissions due to uneven distribution of dust does not exceed 5%) should make: for two burners — 22% ... 27%, four — 12% ... 22%, six — 11% ... 13%. At higher values of Δg and with increasing α, there is a significant increase in emissions of nitrogen oxides and benz(a)pyrene. It is obtained that simultaneously there is a simultaneous increase in NOx and BP. Recommendations are given on the use of dust distribution circuits and designs of dust dividers that meet the requirements to ensure that the uneven distribution of fuel over the burners would not affect emissions of nitrogen oxides.

Effect of Operational Parameters on Combustion and Emissions in an Industrial Gas Turbine Combustor

Enhancing a combustion system requires increased combustion efficiency, fuel savings, and reduction of combustion emissions. In this paper, the combustion of CH4 in the combustor of an industrial gas turbine is studied and NO and CO formation/emission is simulated numerically. The objective of the current work is to investigate the influence of combustive parameters and varying the percentage of distributed air flow rate via burning, recirculation, and dilution zone on the reactive flow characteristics, NOx and CO emissions. The governing equations of mass, momentum, energy, turbulence quantities Renormalized group (RNG) (k–ε), mixture fraction and its variance are solved by the finite volume method. The formation and emission of NOx is numerically simulated in a postprocessing fashion, due to the low concentration of the pollutants as compared to the main combustion species. The present work focuses on different physical mechanisms of NOx formation. The thermal-NOx and prompt-NOx mechanism are considered for modeling the NOx source term in the transport equation. Results show that in a gaseous-fueled combustor, the thermal NOx is the dominant mechanism for NOx formation. Particularly, the simulation provides more insight into the correlation between the maximum combustor temperature, exhaust average temperatures, and the thermal NO concentration. Results indicate that the exhaust temperature and NOx concentration decrease while the excess air factor increases. Moreover, results demonstrate that as the combustion air temperature increases, the combustor temperature increases and the thermal NOx concentration increases dramatically. Furthermore, results demonstrate that the NO concentration at the combustor exit is at maximum value in a swirl angle of 55 deg and a gradual rise in the NOx concentration is detected as the combustion fuel temperature increases. In addition, results demonstrate that the air distribution of the first case at laboratory conditions is optimal where the mass fractions of NO and CO are minimum.