Chemical Kinetic Analysis of a Flameless Gas Turbine Combustor

2008 ◽  
Author(s):  
G. Arvind Rao ◽  
Yeshayahou Levy ◽  
Ephraim J. Gutmark
Keyword(s):  
Combustion Chamber ◽  
Kinetic Analysis ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Plug Flow ◽  
Combustion Process ◽  
Chemical Reactor ◽  
Chemical Kinetic ◽  
Combustion Regime ◽  
Reactor Model

Flameless combustion (FC) is one of the most promising techniques of reducing harmful emissions from combustion systems. FC is a combustion phenomenon that takes place at low O2 concentration and high inlet reactant temperature. This unique combination results in a distributed combustion regime with a lower adiabatic flame temperature. The paper focuses on investigating the chemical kinetics of an prototype combustion chamber built at the university of Cincinnati with an aim of establishing flameless regime and demonstrating the applicability of FC to gas turbine engines. A Chemical reactor model (CRM) has been built for emulating the reactions within the combustor. The entire combustion chamber has been divided into appropriate number of Perfectly Stirred Reactors (PSRs) and Plug Flow Reactors (PFRs). The interconnections between these reactors and the residence times of these reactors are based on the PIV studies of the combustor flow field. The CRM model has then been used to predict the combustor emission profile for various equivalence ratios. The results obtained from CRM model show that the emission from the combustor are quite less at low equivalence ratios and have been found to be in reasonable agreement with experimental observations. The chemical kinetic analysis gives an insight on the role of vitiated combustion gases in suppressing the formation of pollutants within the combustion process.

Numerical Simulation of Pollutant Emissions in a Can-Type Low NOx Gas Turbine Combustor

2010 ◽  
Author(s):  
Di Wang ◽  
Wenjun Kong ◽  
Yuhua Ai ◽  
Baorui Wang
Keyword(s):  
Gas Turbine ◽  
Plug Flow ◽  
Combustion Process ◽  
Chemical Reactor ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Gas Turbine Combustor ◽  
In Series

A research program is in development in China in order to realize a demonstrator of combined cooling heating and power system (CCHP) with net electrical output around 100kW by using of a can-type micro gas turbine. In this paper, numerical simulations were completed to investigate the pollutant emissions in a can-type low NOx gas turbine combustor. Based on the analysis of the computational fluid dynamics (CFD) results, a Chemical Reactor Network (CRN) model was set up to simulate the pollutant emissions in the combustor with detailed gas-phase chemical kinetic mechanism of GRI-Mech 3.0. The CRN consists of a number of ideal reactors of the perfectly stirred reactors (PSR) and plug flow reactors (PFR) in series and parallel structures. Two types of CRN models were designed. One is relatively simple, another is more complex. The results show that the complex CRN model corresponds with the actual combustion process better. The trends of nitrogen oxides (NOx) and carbon monoxide (CO) varying with the equivalence ratio were conducted. Effects of the inlet temperature and pressure on NOx and CO emissions were also presented in this paper. At last, the numerical results are compared with the experimental results.

Effect of Fuel Staged Proportion on NOX Emission Performance of Centrally Staged Combustor

2013 ◽  
Author(s):  
Fuqiang Liu ◽  
Yong Mu ◽  
Cunxi Liu ◽  
Jinhu Yang ◽  
Yanhui Mao ◽  
...  
Keyword(s):  
Equivalence Ratio ◽  
Flow Reactor ◽  
Flame Temperature ◽  
Plug Flow ◽  
Combustion Process ◽  
Chemical Reactor ◽  
Nox Emission ◽  
Wide Range ◽  
Pilot Fuel ◽  
Pollution Emissions

The low NOX emission technology has become an important feature of advanced aviation engine. A wide range of applications attempt to take advantage of the fact that staged combustion operating under lean-premixed-prevaporized (LPP) conditions can significantly decrease pollution emissions and improve combustion efficiency. In this paper a scheme with fuel centrally staged and multi-point injection is proposed. The mixing of fuel and air is improved, and the flame temperature is typically low in combustion zone, minimizing the formation of nitrogen oxides (NOX), especially thermal NOX. In terms of the field distribution of equivalence ratio and temperature obtained from Computational Fluid Dynamics (CFD), a chemical reactor network (CRN), including several different ideal reactor, namely perfectly stirred reactor (PSR) and plug flow reactor (PFR), is constructed to simulate the combustion process. The influences of the pilot equivalence ratio and percentage of pilot/main fuel on NOX and carbon monoxide (CO) emissions were studied by Chemical CRN model. Then the NOX emission in the staged combustor was researched experimentally. The effects of the amount of pilot fuel and primary fuel on pollution emissions were obtained by using gas analyzer. Finally, the effects of pilot fuel proportion on NOX emission were discussed in detail by comparing predicts of CRN and experimental results.

Chemical Reactor Network Application to Emissions Prediction for Industial DLE Gas Turbine

2006 ◽  
Author(s):  
I. V. Novosselov ◽  
P. C. Malte ◽  
S. Yuan ◽  
R. Srinivasan ◽  
J. C. Y. Lee
Keyword(s):  
Gas Turbine ◽  
Chemical Reactor ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Reacting Flow ◽  
Ongoing Research ◽  
Chemical Reactor Network ◽  
Reaction Zones ◽  
Reactor Network

A chemical reactor network (CRN) is developed and applied to a dry low emissions (DLE) industrial gas turbine combustor with the purpose of predicting exhaust emissions. The development of the CRN model is guided by reacting flow computational fluid dynamics (CFD) using the University of Washington (UW) eight-step global mechanism. The network consists of 31 chemical reactor elements representing the different flow and reaction zones of the combustor. The CRN is exercised for full load operating conditions with variable pilot flows ranging from 35% to 200% of the neutral pilot. The NOpilot. The NOx and the CO emissions are predicted using the full GRI 3.0 chemical kinetic mechanism in the CRN. The CRN results closely match the actual engine test rig emissions output. Additional work is ongoing and the results from this ongoing research will be presented in future publications.

The Role of the Recirculating Gases at the Mild Combustion Regime Formation

2007 ◽  
Author(s):  
Y. Levy ◽  
V. Sherbaum ◽  
V. Erenburg
Keyword(s):  
Gas Turbine ◽  
Ignition Delay ◽  
Ignition Delay Time ◽  
Combustion Process ◽  
Combustion Regime ◽  
Reaction Products ◽  
Gas Turbine Combustor ◽  
Mild Combustion ◽  
Recirculation Rate ◽  
Co Emission

The present work is concerned with the thermodynamic and chemical kinetics of gas turbine combustor operating in the Moderate or Intense Low-oxygen Dilution (MILD) combustion regime. The objective of the present study is to evaluate analytically the effect of the recirculation rate of combustion products within the FLOXCOM gas turbine combustor on a number of combustion parameters, mainly on the ignition delay time, NOx and CO emission, minimum ignition temperature, rate of pollutant formation and the dilution rate. The study also refers to the mechanism of influence of the recirculation rate on these values. Combustion pressure and inlet air temperature are used as parameters. The gas turbine is fueled with methane. The analysis is mainly based on CHEMKIN simulations where the calculation scheme of the combustion process in the combustor is modeled by a combination of plug reactors and mixers. Due to the unique characteristics of gas turbines, inlet air temperature is directly linked to combustion pressure while assuming conventional adiabatic compression efficiencies. It is shown that free radicals, which are part of the reaction products and exists for only a short period of time within the recirculated gases, decrease ignition delay time. The importance of shortening the ignition delay is further highlighted because of the adverse effect oxygen dilution has on this parameter (dilution of the reactants by the reaction products). It was found that there is an optimal recirculation rate, which corresponds to maximum heat density. In addition, results indicate that CO emission values rise with the recirculation rate, however the NOX values are more complicated. NOX depends on recirculation rate when flame temperatures are kept held constant. The NOX emission increases and the CO emission decreases with compressor pressure ratio. The CO concentration that is evaluated in the combustion process is further reduced during last dilution stage. Finally, basic rules for design optimization of the combustor are drafted. These are based on conventional one-dimensional fluid and thermodynamic relations and on the CHEMKIN simulations.

Gas Turbine Emission Characteristics in Perfectly Premixed Combustion

2011 ◽  
Author(s):  
A. M. Elkady ◽  
D. M. Kalitan ◽  
J. Herbon ◽  
G. Leonard ◽  
R. Akula ◽  
...  
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Chemical Reactor ◽  
Premixed Combustion ◽  
Emission Characteristics ◽  
Reactor Model ◽  
Chemical Reaction Mechanisms ◽  
Industrial Gas Turbine ◽  
Gas Turbine Cycle ◽  
Detailed Chemical

In the present study, a simple perfectly premixed research burner was utilized at temperatures, pressures and residence times representative of an industrial gas turbine cycle to identify the lower limit of NOx and CO emissions, and to establish an emissions benchmark for practical gas turbine combustors. In addition to experimental data, a chemical reactor model has been utilized for the prediction of the NOx and CO, based on detailed chemical reaction mechanisms. Several current kinetics mechanisms were evaluated and subsequently compared to the experimental data. In addition, sensitivity analysis was performed to identify important reactions at the conditions tested, and will be discussed.

Actuation Studies for Active Control of Mild Combustion for Gas Turbine Application

2014 ◽  
Author(s):  
Emilien Varea ◽  
Stephan Kruse ◽  
Heinz Pitsch ◽  
Thivaharan Albin ◽  
Dirk Abel
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Active Control ◽  
Gas Turbines ◽  
Reverse Flow ◽  
Air Flow ◽  
Combustion Regime ◽  
Nox Emissions ◽  
Low Oxygen ◽  
Mild Combustion

MILD combustion (Moderate or Intense Low Oxygen Dilution) is a well known technique that can substantially reduce high temperature regions in burners and thereby reduce thermal NOx emissions. This technology has been successfully applied to conventional furnace systems and seems to be an auspicious concept for reducing NOx and CO emissions in stationary gas turbines. To achieve a flameless combustion regime, fast mixing of recirculated burnt gases with fresh air and fuel in the combustion chamber is needed. In the present study, the combustor concept is based on the reverse flow configuration with two concentrically arranged nozzles for fuel and air injections. The present work deals with the active control of MILD combustion for gas turbine applications. For this purpose, a new concept of air flow rate pulsation is introduced. The pulsating unit offers the possibility to vary the inlet pressure conditions with a high degree of freedom: amplitude, frequency and waveform. The influence of air flow pulsation on MILD combustion is analyzed in terms of NOx and CO emissions. Results under atmospheric pressure show a drastic decrease of NOx emissions, up to 55%, when the pulsating unit is active. CO emissions are maintained at a very low level so that flame extinction is not observed. To get more insights into the effects of pulsation on combustion characteristics, velocity fields in cold flow conditions are investigated. Results show a large radial transfer of flow when pulsation is activated, hence enhancing the mixing process. The flame behavior is analyzed by using OH* chemiluminescence. Images show a larger distributed reaction region over the combustion chamber for pulsation conditions, confirming the hypothesis of a better mixing between fresh and burnt gases.

Modeling the Formation of Pollutant Emissions in Large-Bore, Lean-Burn Gas Engines

2017 ◽  
Author(s):  
Anamol Pundle ◽  
David G. Nicol ◽  
Philip C. Malte ◽  
Joel D. Hiltner
Keyword(s):  
Partial Oxidation ◽  
Flow Reactor ◽  
Batch Reactor ◽  
Plug Flow ◽  
Chemical Reactor ◽  
Chemical Kinetic ◽  
Pollutant Emissions ◽  
Lean Burn ◽  
Reciprocating Engines ◽  
Stroke Engine

This paper discusses chemical kinetic modeling used to analyze the formation of pollutant emissions in large-bore, lean-burn gas reciprocating engines. Pollutants considered are NOx, CO, HCHO, and UHC. A quasi-dimensional model, built as a chemical reactor network (CRN), is described. In this model, the flame front is treated as a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR), and reaction in the burnt gas is modeled assuming a batch reactor of constant-pressure and fixed-mass for each crank angle increment. The model treats full chemical kinetics. Engine heat loss is treated by incorporating the Woschni model into the CRN. The mass burn rate is selected so that the modeled cylinder pressure matches the experiment pressure trace. Originally, the model was developed for large, low speed, two-stoke, lean-burn engines. However, recently, the model has been formatted for the four-stroke, open-chamber, lean-burn engine. The focus of this paper is the application of the model to a four-stroke engine. This is a single-cylinder non-production variant of a heavy duty lean-burn engine of about 5 liters cylinder displacement Engine speed is 1500 RPM. Key findings of this work are the following. 1) Modeled NOx and CO are found to agree closely with emission measurements for this engine over a range of relative air-fuel ratios tested. 2) This modeling shows the importance of including N2O chemistry in the NOx calculation. For λ = 1.7, the model indicates that about 30% of the NOx emitted is formed by the N2O mechanism, with the balance from the Zeldovich mechanism. 3) The modeling shows that the CO and HCHO emissions arise from partial oxidation late in the expansion stroke as unburned charge remaining mixes into the burnt gas. 4) Model generated plots of HCHO versus CH4 emission for the four-stroke engine are in agreement with field data for large-bore, lean-burn, gas reciprocating engines. Also, recent engine tests show the correlation of UHC and CO emissions to crevice volume. These tests suggest that HCHO emissions also are affected by crevice flows through partial oxidation of UHC late in the expansion stroke.

Uncertainty Quantification of NOx Emission Due to Operating Conditions and Chemical Kinetic Parameters in a Premixed Burner

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Sajjad Yousefian ◽  
Gilles Bourque ◽  
Rory F. D. Monaghan
Keyword(s):  
Sensitivity Analysis ◽  
Uncertainty Quantification ◽  
Gas Turbine ◽  
Flow Reactor ◽  
Epistemic Uncertainty ◽  
Plug Flow ◽  
Chemical Kinetic ◽  
Operating Conditions ◽  
Nox Emission ◽  
Gas Turbine Combustion

Many sources of uncertainty exist when emissions are modeled for a gas turbine combustion system. They originate from uncertain inputs, boundary conditions, calibration, or lack of sufficient fidelity in a model. In this paper, a nonintrusive polynomial chaos expansion (NIPCE) method is coupled with a chemical reactor network (CRN) model using Python to quantify uncertainties of NOx emission in a premixed burner. The first objective of uncertainty quantification (UQ) in this study is development of a global sensitivity analysis method based on the NIPCE method to capture aleatory uncertainty on NOx emission due to variation of operating conditions. The second objective is uncertainty analysis (UA) of NOx emission due to uncertain Arrhenius parameters in a chemical kinetic mechanism to study epistemic uncertainty in emission modeling. A two-reactor CRN consisting of a perfectly stirred reactor (PSR) and a plug flow reactor (PFR) is constructed in this study using Cantera to model NOx emission in a benchmark premixed burner under gas turbine operating conditions. The results of uncertainty and sensitivity analysis (SA) using NIPCE based on point collocation method (PCM) are then compared with the results of advanced Monte Carlo simulation (MCS). A set of surrogate models is also developed based on the NIPCE approach and compared with the forward model in Cantera to predict NOx emissions. The results show the capability of NIPCE approach for UQ using a limited number of evaluations to develop a UQ-enabled emission prediction tool for gas turbine combustion systems.

Visualization of the Effects of Post Injection and Swirl on the Combustion Process of a Passenger Car Common Rail DI Diesel Engine

2003 ◽  
Author(s):  
Arjan Helmantel ◽  
Joop Somhorst ◽  
Ingemar Denbratt
Keyword(s):  
Diesel Engine ◽  
Combustion Chamber ◽  
Flame Temperature ◽  
Combustion Process ◽  
Small Diameter ◽  
Ccd Camera ◽  
Common Rail ◽  
Post Injection ◽  
Passenger Car ◽  
Di Diesel Engine

The effects of variations in injection strategy and swirl on a DI Diesel engine performance and emissions were tested. The cylinder head was fitted with a small diameter endoscope, coupled with a triggered CCD camera, in order to study the effect of these variations on the combustion process. The images that were taken of the combustion process were used to calculate the spatial and temporal distribution of flame temperature and soot kks factor by using the 2-color method. The engine used in the experiments is a single cylinder version of a modern, passenger car type, common rail Diesel engine with a displacement of 480 cc. The fitted endoscope caused very little interference with the combustion chamber due to its small dimensions. The 65 degree angle view of the endoscope allowed coverage of a large portion of the entire combustion chamber. The combustion images and derived temperatures and soot concentrations were used to study the influence of post injection and high swirl. Adding a third (post) injection to the pilot and main injection increases the mixing and the flame temperature during the second half of the combustion process, thereby improving soot oxidation. The fuel efficiency was not negatively affected by the later phasing of part of the heat release. Increased swirl of the intake air was also studied. An 80% increase in swirl-ratio was achieved by closing off one of the two intake ports with a butterfly valve. The improved mixing gave significant reductions in soot emissions, with a small increase in NOx formation.

Large Eddy Simulation and Experimental Analysis of Combustion Dynamics in a Gas Turbine Burner

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Daniel Moëll ◽  
Andreas Lantz ◽  
Karl Bengtson ◽  
Daniel Lörstad ◽  
Annika Lindholm ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Cross Flow ◽  
Flame Stabilization ◽  
Large Eddy Simulations ◽  
Combustion Dynamics ◽  
Flamelet Generated Manifold ◽  
Large Eddy ◽  
Gas Turbine Burner

Large eddy simulations (LES) and experiments (planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) and pressure transducer) have been carried out on a gas turbine burner fitted to an atmospheric combustion rig. This burner, from the Siemens SGT-800 gas turbine, is a low NOx, partially premixed burner, where preheat air temperature, flame temperature, and pressure drop across the burner are kept similar to engine full load conditions. The large eddy simulations are based on a flamelet-generated manifold (FGM) approach for representing the chemistry and the Smagorinsky model for subgrid turbulence. The experimental data and simulation data are in good agreement, both in terms of time averaged and time-resolved quantities. From the experiments and LES, three bands of frequencies of pressure fluctuations with high power spectral density are found in the combustion chamber. The first two bands are found to be axial pressure modes, triggered by coherent flow motions from the burner, such as the flame stabilization location and the precessing vortex core (PVC). The third band is found to be a cross flow directional mode interacting with two of the four combustion chamber walls in the square section of the combustion chamber, triggered from general flow motions. This study shows that LES of real gas turbine components is feasible and that the results give important insight into the flow, flame, and acoustic interactions in a specific combustion system.

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