High-frequency transition characteristics of synthetic natural gas combustion in gas turbine

2019 ◽  
Vol 123 (1259) ◽  
pp. 138-156
Author(s):  
S. Joo ◽  
S. Kwak ◽  
S. Kim ◽  
J. Lee ◽  
Y. Yoon
Keyword(s):  
Gas Turbine ◽  
Heat Load ◽  
Laminar Flame ◽  
Burning Velocity ◽  
Combustion Instability ◽  
Radial Profile ◽  
Frequency Mode ◽  
Abel Inversion ◽  
Inversion Process ◽  
Mode Shift

AbstractIn this study, the combustion instability and emission characteristics of flames of different H2/CH4 compositions were investigated in a partially premixed model gas turbine combustor. A mode shift in the frequency of instability occurred under varying experimental conditions from the first to the seventh mode of longitudinal frequency in the combustor, and a parametric study was conducted to determine the reasons for this shift by using the length of the combustor, a factor that determines the mode frequency of longitudinal instability, as the main parameter. Furthermore, heat load and fuel composition (H2 ratio) were considered as parameters to compare the phenomenon under different conditions. The GRI-3.0 CANTERA code, OH chemiluminescence and the Abel inversion process were applied to analyse the frequency mode shift. NOx emissions, which occurred through the thermal NOx mechanism, increased with increasing heat load and H2 ratio. The instability frequency shifted from the first to the seventh mode as the H2 ratio increased in the H2/CH4 mixture. However, 100% H2 as fuel did not cause combustion instability because it has a higher burning velocity and extinction stretch rate than CH4. Furthermore, the laminar flame speed influenced the frequency mode shift. These phenomena were confirmed by the flame shapes. The Abel inversion process was applied to obtain the cross section of the flames from averaged OH chemiluminescence images. Stable and unstable flames were identified from the radial profile of OH concentration. The combustor length was found to not influence frequency mode shift, whereas the H2 ratio significantly influenced it as well as the flame shape. The results of this experimental study can help in the reliable operation of gas turbine systems in SNG plants.

Influence of Radiation Reabsorption on Laminar Burning Velocity of Methane Premixed Flame Composed With Steam and Carbon Dioxide

2005 ◽  
Author(s):  
Takumi Ebara ◽  
Norihiko Iki ◽  
Sanyo Takahashi ◽  
Won-Hee Park
Keyword(s):  
Carbon Dioxide ◽  
Gas Turbine ◽  
Laminar Flame ◽  
Burning Velocity ◽  
Chemical Kinetic ◽  
Laminar Burning Velocity ◽  
Premixed Laminar ◽  
Kinetic Calculations ◽  
Reforming Gas ◽  
Radiation Reabsorption

Replacing the Nitrogen with another kind of inert gas such as steam and Carbon dioxide is effective for both reducing NOx and enhancing system efficiency in gas turbine combustor. But the flame properties of such radiative mixture are complicated because of the third body effect and radiation reabsorption. So, we made detailed chemical kinetic calculations including the effect of radiation reabsorption to clarify the premixed laminar flame speed of such mixture as one of the most important properties for controlling the combustion. The concentrations of mixture are varied, and addition of other species such as Carbon monoxide and Hydrogen are also calculated to simulate the utilization of reforming gas and partially oxidized gas. And the pressure was varied up to 5.0 MPa to simulate the 1700 °C class combined gas turbine system. The results show remarkable incensement of laminar burning velocity by considering the radiation reabsorption. Laminar burning velocities were accelerated up to 150% in cases of Methane–Oxygen and steam or Carbon dioxide mixture. It was found that preheating of upstream-unburned mixture caused this acceleration. And the influence of radiation reabsorption was much larger in case of lower pressure.

The Optimisation of Reaction Rate Parameters for Chemical Kinetic Modelling Using Genetic Algorithms

2002 ◽  
Author(s):  
L. Elliott ◽  
D. B. Ingham ◽  
A. G. Kyne ◽  
N. S. Mera ◽  
M. Pourkashanian ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Gas Turbine ◽  
Rate Constants ◽  
Reaction Rate ◽  
Kinetic Modelling ◽  
Burning Velocity ◽  
Chemical Kinetic ◽  
Rate Coefficients ◽  
Inversion Process ◽  
Experimental Findings

It is well recognised that many important combustion phenomena are kinetically controlled. Whether it be the burning velocity of a premixed flame, the formation of pollutants in an exhaust stack or the conversion of NO to NO2 in a gas turbine combustor, it is important that a detailed chemical kinetic approach be undertaken in order to fully understand the chemical processes taking place. This study uses a genetic algorithm to determine new reaction rate parameters (A’s, β’s and Ea’s in the Arrhenius expressions) for the combustion of both a hydrogen/air and methane/air mixture in a perfectly stirred reactor. In both cases, output species profiles obtained from an original set of rate constants are reproduced by a new different set obtained using a genetic algorithm inversion process. The new set of rate constants lie between predefined boundaries (±25% of the original values) which in future work can be extended to represent the uncertainty associated with experimental findings. In addition, this powerful technique may be used in developing reaction mechanisms whose newly optimised rate constants reproduce all the experimental data available, enabling a greater confidence in their predictive capabilities. The results of this study therefore demonstrate that the genetic algorithm inversion process promises the ability to assess combustion behaviour for fuels where the reaction rate coefficients are not known with any confidence and, subsequently, accurately predict emission characteristics, stable species concentrations and flame characterisation. Such predictive capabilities will be of paramount importance within the gas turbine industry.

Laminar Flame Speed Measurements of Hydrogen/Natural Gas Mixtures for Gas Turbine Applications

2021 ◽  
Author(s):  
Gihun Kim ◽  
Ritesh Ghorpade ◽  
Subith S. Vasu
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Laminar Flame ◽  
Burning Velocity ◽  
Nox Reduction ◽  
Pressure Rise ◽  
Initial Pressure ◽  
Chemical Kinetic ◽  
Experimental Conditions ◽  
Fuel Blend

Abstract Due to the increasingly challenging carbon emission reduction targets, hydrogen-containing fuel combustion is gaining the energy community’s attention, as highlighted recently in the U.S. Department of Energy’s (DOE) Hydrogen Program Plan [1]. Though fundamental and applied research of hydrogen-containing fuels has been a topic of research for several decades, there are knowledge-gaps and unexplored fuel blend combustion characteristics at conditions relevant to modern gas turbine combustors. Hydrogen will be burned directly or as mixtures with natural gas (NG) and/or ammonia (NH3) in these devices. Fundamental research on the combustion of hydrogen (H2) containing fuels is still essential, especially to overcome or accurately predict challenges such as nitrogen oxides (NOx) reduction and flashback and develop fuel flexible combustors for a prosperous hydrogen economy. We focused our investigation on a natural gas and hydrogen mixture. Measurements of laminar burning velocity (LBV) are necessary for these fuels to understand their applicability in the turbines and other engines. In this study, the maximum rate of pressure rise and LBV of methane (CH4), CH4/H2, natural gas, and natural gas/H2 mixture were measured in synthetic air. The experimental conditions were at an initial pressure of 1 atm and an initial temperature of 300 K. A realistic natural gas composition from the field was used in this study and consisted of CH4 and other alkanes. The experimental data were compared with simulations carried out with detailed chemical kinetic mechanisms.

Extension of the Combustion Stability Range in Dry Low NOx Lean Premixed Gas Turbine Combustor Using a Fuel Rich Annular Pilot Burner

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
L. Rosentsvit ◽  
Y. Levy ◽  
V. Erenburg ◽  
V. Sherbaum ◽  
V. Ovcharenko ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Combustion Zone ◽  
Combustion Instability ◽  
Experimental Results ◽  
Nox Emission ◽  
Combustion Stability ◽  
Stability Range ◽  
Numerical Effort ◽  
Lean Premixed ◽  
Pilot Burner

The present work is concerned with improving combustion stability in lean premixed (LP) gas turbine combustors by injecting free radicals into the combustion zone. The work is a joint experimental and numerical effort aimed at investigating the feasibility of incorporating a circumferential pilot combustor, which operates under rich conditions and directs its radicals enriched exhaust gases into the main combustion zone as the means for stabilization. The investigation includes the development of a chemical reactors network (CRN) model that is based on perfectly stirred reactors modules and on preliminary CFD analysis as well as on testing the method on an experimental model under laboratory conditions. The study is based on the hypothesis that under lean combustion conditions, combustion instability is linked to local extinctions of the flame and consequently, there is a direct correlation between the limiting conditions affecting combustion instability and the lean blowout (LBO) limit of the flame. The experimental results demonstrated the potential reduction of the combustion chamber's LBO limit while maintaining overall NOx emission concentration values within the typical range of low NOx burners and its delicate dependence on the equivalence ratio of the ring pilot flame. A similar result was revealed through the developed CHEMKIN-PRO CRN model that was applied to find the LBO limits of the combined pilot burner and main combustor system, while monitoring the associated emissions. Hence, both the CRN model, and the experimental results, indicate that the radicals enriched ring jet is effective at stabilizing the LP flame, while keeping the NOx emission level within the characteristic range of low NOx combustors.

A Numerical Study on the Reactivity of Biogas/Reformed-Gas/Air and Methane/Reformed-Gas/Air Mixtures at Gas Turbine Relevant Conditions

2016 ◽  
Author(s):  
Pablo Diaz Gomez Maqueo ◽  
Philippe Versailles ◽  
Gilles Bourque ◽  
Jeffrey M. Bergthorson
Keyword(s):  
Gas Turbine ◽  
Laminar Flame ◽  
Numerical Study ◽  
Flame Temperature ◽  
Flame Speed ◽  
Flame Stability ◽  
Laminar Flame Speed ◽  
Fuel Reforming ◽  
Numerical Work ◽  
Chemical Effects

This study investigates the increase in methane and biogas flame reactivity enabled by the addition of syngas produced through fuel reforming. To isolate thermodynamic and chemical effects on the reactivity of the mixture, the burner simulations are performed with a constant adiabatic flame temperature of 1800 K. Compositions and temperatures are calculated with the chemical equilibrium solver of CANTERA® and the reactivity of the mixture is quantified using the adiabatic, freely-propagating premixed flame, and perfectly-stirred reactors of the CHEMKIN-Pro® software package. The results show that the produced syngas has a content of up to 30 % H2 with a temperature up to 950 K. When added to the fuel, it increases the laminar flame speed while maintaining a burning temperature of 1800 K. Even when cooled to 300 K, the laminar flame speed increases up to 30 % from the baseline of pure biogas. Hence, a system can be developed that controls and improves biogas flame stability under low reactivity conditions by varying the fraction of added syngas to the mixture. This motivates future experimental work on reforming technologies coupled with gas turbine exhausts to validate this numerical work.

Analysis of Water–Fuel Ratio Variation in a Gas Turbine With a Wet-Compressor System by Change in Fuel Composition

2017 ◽  
Vol 140 (5) ◽  
Author(s):  
Yonatan Cadavid ◽  
Andres Amell ◽  
Juan Alzate ◽  
Gerjan Bermejo ◽  
Gustavo A. Ebratt
Keyword(s):  
Gas Turbine ◽  
Burning Velocity ◽  
Thermal Power ◽  
Flame Temperature ◽  
Fuel Composition ◽  
Nox Formation ◽  
Gaseous Hydrocarbon ◽  
Power Generators ◽  
Fuel Ratio ◽  
Combustion Properties

The wet compressor (WC) has become a reliable way to reduce gas emissions and increase gas turbine efficiency. However, fuel source diversification in the short and medium terms presents a challenge for gas turbine operators to know how the WC will respond to changes in fuel composition. For this study, we assessed the operational data of two thermal power generators, with outputs of 610 MW and 300 MW, in Colombia. The purpose was to determine the maximum amount of water that can be added into a gas turbine with a WC system, as well as how the NOx/CO emissions vary due to changes in fuel composition. The combustion properties of different gaseous hydrocarbon mixtures at wet conditions did not vary significantly from each other—except for the laminar burning velocity. It was found that the fuel/air equivalence ratio in the turbine reduced with lower CH4 content in the fuel. Less water can be added to the turbine with leaner combustion; the water/fuel ratio was decreased over the range of 1.4–0.4 for the studied case. The limit is mainly due to a reduction in flame temperature and major risk of lean blowout (LBO) or dynamic instabilities. A hybrid reaction mechanism was created from GRI-MECH 3.0 and NGIII to model hydrocarbons up to C5 with NOx formation. The model was validated with experimental results published previously in literature. Finally, the effect of atmospheric water in the premixed combustion was analyzed and explained.

CO and H2O Time-Histories in Shock-Heated Blends of Methane and Ethane for Assessment of a Chemical Kinetics Model

2017 ◽  
Author(s):  
O. Mathieu ◽  
C. Mulvihill ◽  
E. L. Petersen ◽  
Y. Zhang ◽  
H. J. Curran
Keyword(s):  
Gas Turbine ◽  
Chemical Kinetics ◽  
Laminar Flame ◽  
Combustion Process ◽  
Practical Interest ◽  
Time History ◽  
Good Marker ◽  
Ignition Delay Times ◽  
Time Histories ◽  
Detailed Kinetics

Methane and ethane are the two main components of natural gas and typically constitute more than 95% of it. In this study, a mixture of 90% CH4 /10% C2H6 diluted in 99% Ar was studied at fuel lean (ϕ = 0.5) conditions, for pressures around 1, 4, and 10 atm. Using laser absorption diagnostics, the time histories of CO and H2O were recorded between 1400 and 1800 K. Water is a final product from hydrocarbon combustion, and following its formation is a good marker of the completion of the combustion process. Carbon monoxide is an intermediate combustion species, a good marker of incomplete/inefficient combustion, as well as a regulated pollutant for the gas turbine industry. Measurements such as these species time histories are important for validating and assessing chemical kinetics models beyond just ignition delay times and laminar flame speeds. Time-history profiles for these two molecules measured herein were compared to a modern, state-of-the-art detailed kinetics mechanism as well as to the well-established GRI 3.0 mechanism. Results show that the H2O profile is accurately reproduced by both models. However, discrepancies are observed for the CO profiles. Under the conditions of this study, the measured CO profiles typically increase rapidly after an induction time, reach a maximum and then decrease. This maximum CO mole fraction is often largely over-predicted by the models, whereas the depletion rate of CO past this peak is often over-estimated by the models for pressures above 1 atm. This study demonstrates the need to improve on the accuracy of the HCCO reactions involved in CO formation for pressures of practical interest for the gas turbine industry.

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 Studies of Diesel Spray Evaporation and Combustion in a Gas Turbine Matrix Burner

2009 ◽  
Author(s):  
Dieter Bohn ◽  
James F. Willie ◽  
Nils Ohlendorf
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Combustion Instability ◽  
Cone Angle ◽  
Spray Angle ◽  
Test Rig ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Flow Simulations ◽  
Air Inlet

Lean gas turbine combustion instability and control is currently a subject of interest for many researchers. The motivation for running gas turbines lean is to reduce NOx emissions. For this reason gas turbine combustors are being design using the Lean Premixed Prevaporized (LPP) concept. In this concept, the liquid fuel must first be atomized, vaporized and thoroughly premixed with the oxidizer before it enters the combustion chamber. One problem that is associated with running gas turbines lean and premixed is that they are prone to combustion instability. The matrix burner test rig at the Institute of Steam and Gas Turbines at the RWTH Aachen University is no exception. This matrix burner is suitable for simulating the conditions prevailing in stationary gas turbines. Till now this burner could handle only gaseous fuel injection. It is important for gas turbines in operation to be able to handle both gaseous and liquid fuels though. This paper reports the modification of this test rig in order for it to be able to handle both gaseous and liquid primary fuels. Many design issues like the number and position of injectors, the spray angle, nozzle type, droplet size distribution, etc. were considered. Starting with the determination of the spray cone angle from measurements, CFD was used in the initial design to determine the optimum position and number of injectors from cold flow simulations. This was followed by hot flow simulations to determine the dynamic behavior of the flame first without any forcing at the air inlet and with forcing at the air inlet. The effect of the forcing on the atomization is determined and discussed.

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