Hydrogen-Enriched Methane Combustion Diluted With Exhaust Gas and Steam: Fundamental Investigation on Laminar Flames and NOx Emissions

2017 ◽  
Author(s):  
Charles Lhuillier ◽  
Romain Oddos ◽  
Lisa Zander ◽  
Finn Lückoff ◽  
Katharina Göckeler ◽  
...  
Keyword(s):  
Power Plants ◽  
Numerical Study ◽  
Flame Temperature ◽  
Methane Combustion ◽  
Steam Injection ◽  
High Reactivity ◽  
Stable Operation ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Nox Formation

Hydrogen utilization in conventional power plants can offer a possibility to cover the residual load of volatile renewable energies while at the same time reducing the carbon footprint of power production. The challenge here is the high reactivity of hydrogen posing a risk of flashback, whereas increased flame temperature may result in higher NOx emissions. A promising approach to overcome this challenges is the dilution of combustion mixtures by exhaust gas recirculation or by steam injection. The present paper provides experimental laminar burning velocities of hydrogen-enriched methane/air mixtures diluted with major components of exhaust gas and with steam. The corresponding numerical study based on a fictive species approach is used to quantify the chemical and physical effects of dilution on laminar burning velocities. The influence of hydrogen-enrichment and dilution on NOx formation is studied numerically. The results demonstrate high potential of dilution with steam or exhaust gas to ensure stable operation even for hydrogen-rich mixtures while maintaining low NOx emissions.

Analysis of the Mixing and Emission Characteristics in a Model Combustor

2018 ◽  
Author(s):  
Shan Li ◽  
Shanshan Zhang ◽  
Lingyun Hou ◽  
Zhuyin Ren
Keyword(s):  
Gas Turbines ◽  
Schmidt Number ◽  
Numerical Study ◽  
Flame Temperature ◽  
Scalar Dissipation ◽  
Mixing Process ◽  
Nox Formation ◽  
Turbulent Schmidt Number ◽  
Wide Range ◽  
Air Mixing

Modern gas turbines in power systems employ lean premixed combustion to lower flame temperature and thus achieve low NOx emissions. The fuel/air mixing process and its impacts on emissions are of paramount importance to combustor performance. In this study, the mixing process in a methane-fired model combustor was studied through an integrated experimental and numerical study. The experimental results show that at the dump location, the time-averaged fuel/air unmixedness is less than 10% over a wide range of testing conditions, demonstrating the good mixing performance of the specific premixer on the time-averaged level. A study of the effects of turbulent Schmidt number on the unmixedness prediction shows that for the complex flow field involved, it is challenging for Reynolds-Averaged Navier-Stokes (RANS) simulations with constant turbulent Schmidt number to accurately predict the mixing process throughout the combustor. Further analysis reveals that the production and scalar dissipation are the key physical processes controlling the fuel/air mixing. Finally, the NOx formation in this model combustor was analyzed and modelled through a flamelet-based approach, in which NOx formation is characterized through flame-front NOx and its post-flame formation rate obtained from one-dimensional laminar premixed flames. The effect of fuel/air unmixedness on NOx formation is accounted for through the presumed probability density functions (PDF) of mixture fraction. Results show that the measured NOx in the model combustor are bounded by the model predictions with the fuel/air unmixedness being 3% and 5% of the maximum unmixedness. In the context of RANS, the accuracy in NOx prediction depends on the unmixedness prediction which is sensitive to turbulent Schmidt number.

NOx Emissions Modeling and Uncertainty From Exhaust-Gas-Diluted Flames

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Antonio C. A. Lipardi ◽  
Jeffrey M. Bergthorson ◽  
Gilles Bourque
Keyword(s):  
Nox Reduction ◽  
Flame Temperature ◽  
No Production ◽  
Exhaust Gas ◽  
Oxides Of Nitrogen ◽  
Nox Formation ◽  
Kinetic And Thermodynamic Parameters ◽  
Emissions Modeling ◽  
Combustion Processes ◽  
Gas Recirculation

Oxides of nitrogen (NOx) are pollutants emitted by combustion processes during power generation and transportation that are subject to increasingly stringent regulations due to their impact on human health and the environment. One NOx reduction technology being investigated for gas-turbine engines is exhaust-gas recirculation (EGR), either through external exhaust-gas recycling or staged combustion. In this study, the effects of different percentages of EGR on NOx production will be investigated for methane–air and propane–air flames at a selected adiabatic flame temperature of 1800 K. The variability and uncertainty of the results obtained by the gri-mech 3.0 (GRI), San-Diego 2005 (SD), and the CSE thermochemical mechanisms are assessed. It was found that key parameters associated with postflame NO emissions can vary up to 192% for peak CH values, 35% for thermal NO production rate, and 81% for flame speed, depending on the mechanism used for the simulation. A linear uncertainty analysis, including both kinetic and thermodynamic parameters, demonstrates that simulated postflame nitric oxide levels have uncertainties on the order of ±50–60%. The high variability of model predictions, and their relatively high associated uncertainties, motivates future experiments of NOx formation in exhaust-gas-diluted flames under engine-relevant conditions to improve and validate combustion and NOx design tools.

Nitrogen Oxides Reduction Effect and the Influence Mechanism of Exhaust Valve Lift on a Two-Stroke Marine Diesel Engine

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Lijiang Wei ◽  
Anmin Wu ◽  
Jie Liu ◽  
Mingliang Zhong ◽  
Xuebai Wang
Keyword(s):  
Diesel Engine ◽  
Nitrogen Oxides ◽  
Exhaust Valve ◽  
Marine Diesel Engine ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Nox Formation ◽  
Influence Mechanism ◽  
Marine Diesel ◽  
Reduction Effect

For the two-stroke marine diesel engine, the action of exhaust valve has a significant impact on scavenging and combustion processes and ultimately affects the engine performances and emissions. In order to reduce nitrogen oxides (NOx) emissions of a two-stroke marine diesel engine, different exhaust valve lifts (EVLs) were achieved by computational fluid dynamics simulation method in this study. The NOx reduction effect and influence mechanism of EVL on a two-stroke marine diesel engine were investigated in detail. The results showed that the in-cylinder residual exhaust gas and the internal exhaust gas recirculation (EGR) rate gradually increased with the decreasing EVL. Although the total mass of charge enclosed in the cylinder did not change much, the composition changed gradually and the maximum internal EGR rate reached 13.17% in this study. The maximum compression pressure and combustion pressure both rose first and then decreased with the decreasing EVL. While the start of combustion and the maximum combustion temperature were basically unaffected by EVL, the indicated power of the engine was also not much impacted when the EVL was changed from increasing 10 mm to decreasing 20 mm. The indicated specific fuel consumption first declined slowly and then rose rapidly as the EVL reduction exceeded 20 mm. NOx emissions decreased monotonously with the decreasing EVL. The reduction of NOx formation rate and the amount of NOx formation mass mainly occurred at the middle and late stages of combustion for the downward moving of residual exhaust gas. NOx emissions were reduced by 12.57% without compromising other engine performances at medium-reduced EVL in this study. However, in order to further reduce NOx emissions at low EVLs, other measures may be needed to make the residual exhaust gas more evenly distributed during the initial stage of combustion.

Hydrogen Enriched Combustion Testing of SIEMENS Industrial SGT-400 at Atmospheric Conditions

2014 ◽  
Author(s):  
Kam-Kei Lam ◽  
Philipp Geipel ◽  
Jenny Larfeldt
Keyword(s):  
Pressure Drop ◽  
Natural Gas ◽  
High Speed ◽  
Flame Temperature ◽  
Stable Operation ◽  
Nox Emissions ◽  
Atmospheric Conditions ◽  
Reference Velocity ◽  
Operation Conditions ◽  
Combustion Behaviors

In order to further extend the turbine fuel flex capability, a test under atmospheric conditions of a full-scale SGT-400 burner was performed to study the combustion behavior when operating on hydrogen enriched natural gas. A high speed camera was installed in the rig to investigate the flame dynamics on different operation conditions. NOx emissions were measured for all presented conditions. The combustion system was instrumented with thermocouples on all the key locations to allow flame position monitoring and to avoid flame attachment on the hardware. Further measurements included static pressure probes to monitor combustor pressure drop. The test was conducted in a systematic matrix format to include the most important combustion parameters in order to identify their individual effects on the combustion behaviors. The quantity of hydrogen in natural gas, fuel split, air preheat temperature, air reference velocity and flame temperature were the combustion related variables studied in the presented test campaign. The volumetric hydrogen quantity could be increased to 30% maintaining stable operation for all measured conditions. Higher hydrogen contents up to 80 vol-% were reached without flash back tendency. A glowing spark igniter prevented testing at even higher hydrogen contents. Hydrogen enriched gas showed higher NOx emissions and improved blowout limit. Hydrogen blending in the fuel also reduced the combustor pressure drop, lowered the prechamber temperature and raised the pilot tip temperature.

CFD Simulation of Humid Air Premixed Flame Combustion Chamber for Evaporative Gas Turbine Cycles

2001 ◽  
Author(s):  
M. Bianco ◽  
S. M. Camporeale ◽  
B. Fortunato
Keyword(s):  
Combustion Chamber ◽  
Equivalence Ratio ◽  
Flame Temperature ◽  
Oxidation Mechanism ◽  
Premixed Flame ◽  
Inlet Temperature ◽  
Nox Emissions ◽  
Humid Air ◽  
Nox Formation ◽  
Operation Conditions

Evaporative cycles, such as Recuperated Water lnjected (RWI) cycle, Humid Air Turbine (HAT) cycle, Cascaded Humidified Advanced Turbine (CHAT) offer the attractive possibility to increase plant efficiency without the use of a steam turbine, necessary for gas-steam combined cycles, appearing, therefore, as an interesting solution for industrial power applications such as electric utilities and independent power producers. It is expected that water addition may contribute to reduce NOx emissions in premixed flame combustors. In order to analyse this solution, a lean-bum combustor, fed with an homogeneous mixture formed by methane and humid air, has been analysed through CFD simulations, in order to predict velocity field, temperatures and emissions. The study has been carried out under the hypothesis of a two-dimensional, axisymmetric combustion chamber assuming, as set of operation conditions, atmospheric pressure, inlet temperature of 650 K, fuel-air equivalence ratio of the methane-air mixture ranging from 0.5 to 0.7 and water-air mass ratio varying from 0% to 5%. In the simulation, the presence of turbulence in the flow has been taken into account using a RNG k-ε model, whilst the chemical behaviour of the system has been described by means of a five-step global reduced mechanism including the oxidation mechanism and the NOx formation mechanism. The analysis of the results shows that the moisture in the premixed flow reduces both NOx and CO emissions at constant equivalence ratio; moreover the lean blow-out limit is shifted toward higher equivalence ratio. The main effect of the water seems to be the increase of the specific heat the mixture which causes a reduction in flame temperature, slowing the chemical reactions responsible of NOx formation. The reasonable agreement has been found between the simulation results concerning NOx emissions and recent experimental results carried out on premixed flamed with humid air. A discussion is also provided about the adopted turbulence models and their influence on the emission results.

scholarly journals Effect of Steam Addition on the Flow Field and NOx Emissions for Jet-A in an Aircraft Combustor

2016 ◽  
Vol 33 (4) ◽  
Author(s):  
Rui Xue ◽  
Chunbo Hu ◽  
Theoklis Nikolaidis ◽  
Pericle Pilidis
Keyword(s):  
Nox Reduction ◽  
Chemical Reactor ◽  
Steam Injection ◽  
Nox Emissions ◽  
Nox Formation ◽  
Steam Content ◽  
Injection Technology ◽  
Integrated Performance ◽  
Processing Techniques ◽  
The Impact

AbstractThe steam injection technology for aircraft engines is gaining rising importance because of the strong limitations imposed by the legislation for NOx reduction in airports. In order to investigate the impact of steam addition on combustion and NOx emissions, an integrated performance-CFD-chemical reactor network (CRN) methodology was developed. The CFD results showed steam addition reduced the high temperature size and the radical pool moved downstream. Then different post-processing techniques are employed and CRN is generated to predict NOx emissions. This network consists of 14 chemical reactor elements and the results were in close agreement with the ICAO databank. The established CRN model was then used for steam addition study and the results showed under air/steam mixture atmosphere, high steam content could push the NOx formation region to the post-flame zone and a large amount of the NOx emission could be reduced when the steam mass fraction is quite high.

The Effect of Using High FFA Rubber Seed Based Biodiesel With Cold and Hot EGR on Performance and Emissions of a CI Engine

2008 ◽  
Author(s):  
B. Baiju ◽  
L. M. Das ◽  
M. K. G. Babu
Keyword(s):  
Carbon Monoxide ◽  
Thermal Efficiency ◽  
Flame Temperature ◽  
Nox Emissions ◽  
Exhaust Gas ◽  
Rubber Seed Oil ◽  
Rubber Seed ◽  
Performance And Emissions ◽  
Ci Engine ◽  
Ci Engines

This paper analyses the effect of exhaust gas recirculation (EGR) on the engine performance and emissions of a compression ignition (CI) engine operating on diesel-biodiesel (rubber seed oil methyl ester) blends. Biodiesel operated engines generally produce less unburned hydrocarbon, carbon monoxide and smoke compared to diesel fuel but more NOx emissions. NOx formation is a temperature dependent phenomenon and takes place when the combustion temperature is more than 2000K. EGR is an effective method for reducing NOx emissions in CI engines because it reduces the flame temperature and the oxygen concentration in the combustion chamber. In this study both hot EGR and cold EGR (5%, 10% and 15%) are used. It was found that NOx emission decreases substantially with both hot and cold EGR but smoke and carbon monoxide emissions are increasing with higher EGR rates. Brake thermal efficiency (BTE) increases with hot egr but cold EGR gives lower thermal efficiency than hot egr. Hot EGR emits less smoke and less NOx at higher loads compared to cold EGR. It was observed that exhaust gas between 10% and 15% can be recirculated for getting better results. The use of EGR is thus considered to be one of the most effective in reducing NOx emissions.

scholarly journals Scaling of an Aviation Hydrogen Micromix Injector Design for Industrial GT Combustion Applications

2021 ◽  
Author(s):  
Johannes Berger
Keyword(s):  
Renewable Energy ◽  
Gas Turbine ◽  
Power Plants ◽  
Supply And Demand ◽  
Pressure Ratio ◽  
Flame Temperature ◽  
Orifice Diameter ◽  
Design Parameters ◽  
Nox Emissions ◽  
The Impact

AbstractDecarbonising the energy grid through renewable energy requires a grid firming technology to harmonize supply and demand. Hydrogen-fired gas turbine power plants offer a closed loop by burning green hydrogen produced with excess power from renewable energy. Conventional dry low NOx (DLN) combustors have been optimized for strict emission limits. A higher flame temperature of hydrogen drives higher NOx emissions and faster flame speed alters the combustion behavior significantly. Micromix combustion offers potential for low NOx emissions and optimized conditions for hydrogen combustion. Many small channels, so-called airgates, accelerate the airflow followed by a jet-in-crossflow injection of hydrogen. This leads to short-diffusion flames following the principle of maximized mixing intensity and minimized mixing scales. This paper shows the challenges and the potential of an economical micromix application for an aero-derivative industrial gas turbine with a high-pressure ratio. A technology transfer based on the micromix combustion research in the ENABLEH2 project is carried out. The driving parameter for ground use adaption is an increased fuel orifice diameter from 0.3 mm to 1.0 mm to reduce cost and complexity. Increasing the fuel supply mass flow leads to larger flames and higher emissions. The impact was studied through RANS simulation and trends for key design parameters were shown. Increased velocity in the airgates leads to a higher pressure drop and reduced emissions through faster mixing. Altering the penetration depth shows potential for emission reduction without compromising on pressure loss. Two improved designs are found, and their performance is discussed.

scholarly journals Semi–Empirical Correlation of NOx Emissions From Combustion Turbines With Water/Steam Injection

1995 ◽  
Author(s):  
Donald M. Newburry ◽  
Arthur M. Mellor
Keyword(s):  
Standard Deviation ◽  
Formation Rate ◽  
Flame Temperature ◽  
Steam Injection ◽  
Measured Data ◽  
Fuel Oil ◽  
Nox Emissions ◽  
Time Model ◽  
Water Steam ◽  
Semi Empirical

Inert (water or steam) injection is commonly used to reduce NOx emissions in stationary gas turbine combustors, both lean premixed when oil–fired and conventional. Thus, having an accurate phenomenological model to predict these reductions could be useful in both design and implementation for low emissions. In this work, the semi–empirical characteristic time model (CTM), which has been validated for thermal NOx emissions from conventional, diffusion flame combustors, is modified to account for inert injection effects. Measured NOx data from two heavy–duty, utility combustion turbines operating on natural gas and fuel oil #2, both dry and with water or steam injection, are correlated. Inert injection is modeled as thermal, and two limiting cases are proposed which successfully bound the measured data. An empirically selected effective inert injection flame temperature was substituted for the stoichiometric flame temperature used to estimate the thermal NO formation rate in the CTM. This procedure correlated all of the measured data from both combustors for both fuels with a standard deviation of 1.02 g NO2/kg fuel. The high standard deviation results from systematic trends in the dry data for one combustor which propagate through the lower NOx values of the inert injection data. Removing these trends empirically improves the combined correlation to a standard deviation of 0.28 g/kg (approximately 3.2 ppmvd at 15% O2).

scholarly journals Parametric Performance of Combined-Cogeneration Power Plants With Various Power and Efficiency Enhancements

1997 ◽  
Author(s):  
T. Korakianitis ◽  
J. Grantstrom ◽  
P. Wassingbo ◽  
A. F. Massardo
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Power Plants ◽  
Steam Injection ◽  
Hot Water ◽  
Plant Performance ◽  
Specific Power ◽  
Specific Rate ◽  
Exhaust Gas ◽  
Design Point

The design-point performance characteristics of a wide variety of combined-cogeneration power plants, with different amounts of supplementary firing (or no supplementary firing), different amounts of steam injection (or no steam injection), different amounts of exhaust gas condensation etc, without limiting these parameters to present-day limits are investigated. A representative power plant with appropriate components for these plant enhancements is developed. A computer program is used to evaluate the performance of various power plants using standard inputs for component efficiencies; and the design-point performance of these plants is computed. The results are presented as thermal efficiency, specific power, effectiveness, and specific rate of energy in district heating. The performance of the simple-cycle gas turbine dominates the overall plant performance; the plant efficiency and power are mainly determined by turbine inlet temperature and compressor pressure ratio; increasing amounts of steam injection in the gas turbine increases the efficiency and power; increasing amounts of supplementary firing decreases the efficiency but increases the power; with sufficient amounts of supplementary firing and steam injection the exhaust-gas condensate is sufficient to make up for water lost in steam injection; and the steam-turbine power is a fraction (0.1 to 0.5) of the gas-turbine power output. Regions of “optimum” parameters for the power plant based on design-point power, hot-water demand, and efficiency are shown. A method for fuel-cost allocation between electricity and hot water is recommended.

Sign in / Sign up

Export Citation Format

Share Document