Energy and Exergy Balance in the Process of Spray Combustion in a Gas Turbine Combustor

2002 ◽  
Vol 124 (5) ◽  
pp. 828-836 ◽  
Author(s):  
S. K. Som ◽  
N. Y. Sharma
Keyword(s):  
Gas Turbine ◽  
Gas Phase ◽  
Transport Processes ◽  
Operating Conditions ◽  
Spray Combustion ◽  
Second Law ◽  
Gas Turbine Combustor ◽  
Thermodynamic Irreversibility ◽  
Entropy Transport ◽  
Exergy Balance

A theoretical model of exergy balance based on availability transfer and flow availability in the process of spray combustion in a gas turbine combustor has been developed to evaluate the total thermodynamic irreversibility and second law efficiency of the process at various operating conditions, for fuels with different volatilities. The velocity, temperature and concentration fields in the combustor, required for the evaluation of the flow availabilities and process irreversibilities, have been computed numerically from a two phase separated flow model of spray combustion. The total thermodynamic irreversibility in the process of spray combustion has been determined from the difference in the flow availability at inlet and outlet of the combustor. The irreversibility caused by the gas phase processes in the combustor has been obtained from the entropy transport equation, while that due to the inter-phase transport processes has been obtained as a difference of gas phase irreversibilities from the total irreversibility. A comparative picture of the variations of combustion efficiency and second law efficiency at different operating conditions for fuels with different volatilities has been made to throw light on the trade off between the effectiveness of combustion and the lost work in the process of spray combustion in a gas turbine combustor.

scholarly journals CFD Analysis of Liquid Spray Combustion in a Gas Turbine Combustor

1997 ◽  
Author(s):  
Mark K. Lai
Keyword(s):  
Gas Turbine ◽  
Gas Phase ◽  
Numerical Study ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Numerical Code ◽  
Gas Turbine Combustor ◽  
Conservation Equations ◽  
Liquid Spray ◽  
Fuel Nozzle

A numerical method is presented for predicting steady, three-dimensional, turbulent, liquid spray combusting flows in a gas turbine combustor. The Eulerian conservation equations for gas flow and the Lagrangian conservation equations for discrete fuel liquid droplets were solved. The trajectory computation of the fuel droplets provided the source terms for all the gas-phase equations. A standard k-ε submodel was used for turbulence. The combustion submodel used was a global local equilibrium model, where chemical species (CxHy, O2, CO2, H2O, CO, H2 and N2) approached local thermodynamic equilibrium with a rate determined by a combination of local turbulent mixing and global chemical kinetics times. The numerical methodology for gas-phase calculations involved a staggered finite-volume formulation with a multi-block curvilinear orthogonal coordinate computational grid, and the PISO algorithm. This numerical code was applied to a model gas turbine combustor similar to that of the Allison 570KF currently in use by the Canadian Navy. The combustor was equipped with an advanced airblast fuel nozzle. The calculations included the analysis of the internal passages of the fuel nozzle. Through the numerical study at full-power and low-cruise operating conditions, a better understanding of the physical processes of flow and temperature fields inside the primary zone was obtained. Predicted hot spots corresponded to locations where deterioration of the combustor liner has been observed in practice.

Energy and Exergy Balance in the Process of Pulverized Coal Combustion in a Tubular Combustor

2005 ◽  
Vol 127 (12) ◽  
pp. 1322-1333 ◽  
Author(s):  
S. K. Som ◽  
S. S. Mondal ◽  
S. K. Dash
Keyword(s):  
Coal Combustion ◽  
Particle Diameter ◽  
Pulverized Coal ◽  
Operating Conditions ◽  
Second Law ◽  
Pulverized Coal Combustion ◽  
Two Phase ◽  
Thermodynamic Irreversibility ◽  
Coal Particles ◽  
Exergy Balance

A theoretical model of exergy balance, based on availability transfer and flow availability, in the process of pulverized coal combustion in a tubular air-coal combustor has been developed to evaluate the total thermodynamic irreversibility and second law efficiency of the process at various operating conditions. The velocity, temperature, and concentration fields required for the evaluation of flow availability have been computed numerically from a two-phase separated flow model on a Eulerian-Lagrangian frame in the process of combustion of pulverized coal particles in air. The total thermodynamic irreversibility in the process has been determined from the difference in the flow availability at the inlet and outlet of the combustor. A comparative picture of the variations of combustion efficiency and second law efficiency at different operating conditions, such as inlet pressure and temperature of air, total air flow rate and inlet air swirl, initial mean particle diameter, and length of the combustor, has been provided to shed light on the trade-off between the effectiveness of combustion and the lost work in the process of pulverized coal combustion in a tubular combustor.

Combustion Characteristics of Small Size Gas Turbine Combustor Fueled by Biomass Gas Employing Flameless Combustion

2007 ◽  
Author(s):  
Masato Hiramatsu ◽  
Yoshifumi Nakashima ◽  
Sadamasa Adachi ◽  
Yudai Yamasaki ◽  
Shigehiko Kaneko
Keyword(s):  
Gas Turbine ◽  
Combustion Efficiency ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Gas Turbine Combustor ◽  
Flameless Combustion ◽  
Engine Exhaust ◽  
Micro Gas Turbine

One approach to achieving 99% combustion efficiency (C.E.) and 10 ppmV or lower NOx (at 15%O2) in a micro gas turbine (MGT) combustor fueled by biomass gas at a variety of operating conditions is with the use of flameless combustion (FLC). This paper compares experimentally obtained results and CHEMKIN analysis conducted for the developed combustor. As a result, increase the number of stage of FLC combustion enlarges the MGT operation range with low-NOx emissions and high-C.E. The composition of fuel has a small effect on the characteristics of ignition in FLC. In addition, NOx in the engine exhaust is reduced by higher levels of CO2 in the fuel.

Towards Improved Prediction of Aero-Engine Combustor Performance Using Large Eddy Simulations

2008 ◽  
Author(s):  
S. James ◽  
M. S. Anand ◽  
B. Sekar
Keyword(s):  
Gas Turbine ◽  
Radial Profile ◽  
Design Tool ◽  
Operating Conditions ◽  
Outlet Temperature ◽  
Gas Turbine Combustor ◽  
Systematic Assessment ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Aero Engine

The paper presents an assessment of large eddy simulation (LES) and conventional Reynolds averaged methods (RANS) for predicting aero-engine gas turbine combustor performance. The performance characteristic that is examined in detail is the radial burner outlet temperature (BOT) or fuel-air ratio profile. Several different combustor configurations, with variations in airflows, geometries, hole patterns and operating conditions are analyzed with both LES and RANS methods. It is seen that LES consistently produces a better match to radial profile as compared to RANS. To assess the predictive capability of LES as a design tool, pretest predictions of radial profile for a combustor configuration are also presented. Overall, the work presented indicates that LES is a more accurate tool and can be used with confidence to guide combustor design. This work is the first systematic assessment of LES versus RANS on industry-relevant aero-engine gas turbine combustors.

Experimental and numerical study of flame structure and emissions in a micro gas turbine combustor

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Vedant Dwivedi ◽  
Srikanth Hari ◽  
S. M. Kumaran ◽  
B. V. S. S. S. Prasad ◽  
Vasudevan Raghavan
Keyword(s):  
Gas Turbine ◽  
Rural Areas ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
Numerical Study ◽  
Operating Conditions ◽  
Emission Characteristics ◽  
Nitric Oxides ◽  
Gas Turbine Combustor ◽  
Micro Gas Turbine

Abstract Experimental and numerical study of flame and emission characteristics in a tubular micro gas turbine combustor is reported. Micro gas turbines are used for distributed power (DP) generation using alternative fuels in rural areas. The combustion and emission characteristics from the combustor have to be studied for proper design using different fuel types. In this study methane, representing fossil natural gas, and biogas, a renewable fuel that is a mixture of methane and carbon-dioxide, are used. Primary air flow (with swirl component) and secondary aeration have been varied. Experiments have been conducted to measure the exit temperatures. Turbulent reactive flow model is used to simulate the methane and biogas flames. Numerical results are validated against the experimental data. Parametric studies to reveal the effects of primary flow, secondary flow and swirl have been conducted and results are systematically presented. An analysis of nitric-oxides emission for different fuels and operating conditions has been presented subsequently.

Experimental Assessment of the Emissions Benefits of a Ceramic Gas Turbine Combustor

1996 ◽  
Author(s):  
K. O. Smith ◽  
A. Fahme
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Gas Turbine Combustor ◽  
Experimental Assessment ◽  
Industrial Gas Turbine ◽  
Combustor Liner

Three subscale, cylindrical combustors were rig tested on natural gas at typical industrial gas turbine operating conditions. The intent of the testing was to determine the effect of combustor liner cooling on NOx and CO emissions. In order of decreasing liner cooling, a metal louvre-cooled combustor, a metal effusion-cooled combustor, and a backside-cooled ceramic (CFCC) combustor were evaluated. The three combustors were tested using the same lean-premixed fuel injector. Testing showed that reduced liner cooling produced lower CO emissions as reaction quenching near the liner wall was reduced. A reduction in CO emissions allows a reoptimization of the combustor air flow distribution to yield lower NOx emissions.

Influence of fuel volatility on combustion and emission characteristics in a gas turbine combustor at different inlet pressures and swirl conditions

2002 ◽  
Vol 216 (3) ◽  
pp. 257-268 ◽  
Author(s):  
N. Y. Sharma ◽  
S. K. Som
Keyword(s):  
Gas Turbine ◽  
Gas Phase ◽  
Combustion Efficiency ◽  
Inlet Pressure ◽  
Emission Characteristics ◽  
Spray Parameters ◽  
Gas Turbine Combustor ◽  
Spray Cone ◽  
Emission Level ◽  
Inlet Swirl

The practical challenges in research in the field of gas turbine combustion mainly centre around a clean emission, a low liner wall temperature and a desirable exit temperature distribution for turboma-chinery applications, along with fuel economy of the combustion process. An attempt has been made in the present paper to develop a computational model based on stochastic separated flow analysis of typical diffusion-controlled spray combustion of liquid fuel in a gas turbine combustor to study the influence of fuel volatility at different combustor pressures and inlet swirls on combustion and emission characteristics. A κ-ɛ model with wall function treatment for the near-wall region has been adopted for the solution of conservation equations in gas phase. The initial spray parameters are specified by a suitable probability distribution function (PDF) size distribution and a given spray cone angle. A radiation model for the gas phase, based on the first-order moment method, has been adopted in consideration of the gas phase as a grey absorbing-emitting medium. The formation of thermal NO x as a post-combustion reaction process is determined from the Zeldovich mechanism. It has been recognized from the present work that an increase in fuel volatility increases combustion efficiency only at higher pressures. For a given fuel, an increase in combustor pressure, at a constant inlet temperature, always reduces the combustion efficiency, while the influence of inlet swirl is found to decrease the combustion efficiency only at higher pressure. The influence of inlet pressure on pattern factor is contrasting in nature for fuels with lower and higher volatilities. For a higher-volatility fuel, a reduction in inlet pressure decreases the value of the pattern factor, while the trend is exactly the opposite in the case of fuels with lower volatilities. The NOx emission level increases with decrease in fuel volatility at all combustor pressures and inlet swirls. For a given fuel, the NOx emission level decreases with a reduction in combustor pressure and an increase in inlet swirl number.

Demonstration of Active Control of Combustion Instabilities on a Full-Scale Gas Turbine Combustor

2001 ◽  
Author(s):  
C. E. Johnson ◽  
Y. Neumeier ◽  
M. Neumaier ◽  
B. T. Zinn ◽  
D. D. Darling ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Active Control ◽  
Fast Response ◽  
Dominant Mode ◽  
Broadband Noise ◽  
Full Scale ◽  
Operating Conditions ◽  
Combustion Instabilities ◽  
Gas Turbine Combustor ◽  
Airflow Distribution

This paper presents the results of an investigation of active control of combustion instabilities in a natural gas, high-pressure, full-scale gas turbine combustor that was retrofitted with an Active Control System (ACS). The combustor test rig simulates the geometry, inlet airflow distribution, and pressurization of a can-type combustor that exhibits dynamic flame instabilities at some off-design operating conditions. Two essential features of the investigated ACS are 1) a real-time mode observer that identified the frequencies, amplitudes and phases of the dominant modes in the pressure signal and 2) a fast response servo valve that can modulate a large portion of the gaseous fuel. Two active control configurations were studied. In the first configuration, the actuator was mounted on one of two premixed fuel stages, and in the second configuration it was mounted on the inlet to the stabilizing diffusion stage. In both configurations, the ACS damped combustion instabilities, attenuating the dominant mode by up to 15dB and reducing the overall broadband noise by 30-40%. NOx emissions were also reduced by approximately 10% when control was applied. Finally, this study demonstrated the importance of having a fast multiple-mode observer when dealing with complex combustion processes with inherently large time delays.

Chemical Analysis of Combustion Products From a High-Pressure Gas Turbine Combustor Rig Fueled by Jet A1 Fuel and a Fischer-Tropsch-Based Fuel

2006 ◽  
Author(s):  
Fredrik Hermann ◽  
Jens Klingmann ◽  
Rolf Gabrielsson ◽  
Jo¨rgen R. Pedersen ◽  
Jim O. Olsson ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Gas Turbine ◽  
Combustion Products ◽  
Jet Fuel ◽  
Synthetic Jet ◽  
Operating Conditions ◽  
Gas Chromatography Mass Spectrometry ◽  
Gas Turbine Combustor ◽  
Fischer Tropsch ◽  
Synthetic Fuel

A comparative experimental investigation has been performed, comparing the emissions from a synthetic jet fuel and from Jet A1. In the investigation, the unburned hydrocarbons were analyzed chemically and the regulated emissions of NOx, CO and HC were measured. All combustion tests were performed under elevated pressures in a gas turbine combustor rig. A Swedish company, Oroboros AB, has developed a novel clean synthetic jet fuel, LeanJet®. The fuel is produced synthetically from synthesis gas by a Fischer-Tropsch process. Except for the density, the fuel conforms to the Standard Specification for Aviation Turbine Fuels. The low density is due to the lack of aromatics and polyaromatics. Organic emissions from the gas turbine combustor rig were collected by adsorption sampling and analyzed chemically. Both the fuels and the organic emissions were analyzed by gas chromatography/flame ionization (GC/FID) complemented with gas chromatography/mass spectrometry (GC/MS). Under the operating conditions investigated, no significant differences were found for the regulated emissions, except for emission of CO from the synthetic fuel, which, at leaner conditions, was one-quarter of that measured for Jet A1. Detailed analysis of the organic compounds showed that the emissions from both fuels were dominated by fuel alkanes and a significant amount of naphthalene. It was also found that Jet A1 produced a much higher amount of benzene than the synthetic fuel.

Bioethanol Combustion in an Industrial Gas Turbine Combustor: Simulations and Experiments

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Joost L. H. P. Sallevelt ◽  
Artur K. Pozarlik ◽  
Martin Beran ◽  
Lars-Uno Axelsson ◽  
Gerrit Brem
Keyword(s):  
Gas Turbine ◽  
Model Comparison ◽  
Reverse Flow ◽  
Operating Conditions ◽  
Fuel Spray ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Gas Turbine Combustor ◽  
Diffusion Type ◽  
Flamelet Model

Combustion tests with bioethanol and diesel as a reference have been performed in OPRA's 2 MWe class OP16 gas turbine combustor. The main purposes of this work are to investigate the combustion quality of ethanol with respect to diesel and to validate the developed CFD model for ethanol spray combustion. The experimental investigation has been conducted in a modified OP16 gas turbine combustor, which is a reverse-flow tubular combustor of the diffusion type. Bioethanol and diesel burning experiments have been performed at atmospheric pressure with a thermal input ranging from 29 to 59 kW. Exhaust gas temperature and emissions (CO, CO2, O2, NOx) were measured at various fuel flow rates while keeping the air flow rate and air temperature constant. In addition, the temperature profile of the combustor liner has been determined by applying thermochromic paint. CFD simulations have been performed with ethanol for five different operating conditions using ANSYS FLUENT. The simulations are based on a 3D RANS code. Fuel droplets representing the fuel spray are tracked throughout the domain while they interact with the gas phase. A liner temperature measurement has been used to account for heat transfer through the flame tube wall. Detailed combustion chemistry is included by using the steady laminar flamelet model. Comparison between diesel and bioethanol burning tests show similar CO emissions, but NOx concentrations are lower for bioethanol. The CFD results for CO2 and O2 are in good agreement, proving the overall integrity of the model. NOx concentrations were found to be in fair agreement, but the model failed to predict CO levels in the exhaust gas. Simulations of the fuel spray suggest that some liner wetting might have occurred. However, this finding could not be clearly confirmed by the test data.

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