scholarly journals The Role of Fuel Preparation in Low Emissions Combustion

1995 ◽  
Author(s):  
A. H. Lefebvre
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Fuel Injection ◽  
Flame Temperature ◽  
Pollutant Emissions ◽  
Alternative Methods ◽  
Nox Emissions ◽  
Oxides Of Nitrogen ◽  
Lean Burn ◽  
The Impact

The attainment of very low pollutant emissions, in particular oxides of nitrogen (NOx), from gas turbines is not only of considerable environmental concern but has also become an area of increasing competitiveness between the different engine manufacturers. For stationary engines, the attainment of ultra-low NOx has become the foremost marketing issue. This paper is devoted primarily to current and emerging technologies in the development of ultra-low emissions combustors for application to aircraft and stationary engines. Short descriptions of the basic design features of conventional gas turbine combustors and the methods of fuel injection now in widespread use are followed by a review of fuel spray characteristics and recent developments in the measurement and modeling of these characteristics. The main gas turbine generated pollutants and their mechanisms of formation are described, along with related environmental risks and various issues concerning emissions regulations and recently-enacted legislation for limiting the pollutant levels emitted by both aircraft and stationary engines. The impact of these emissions regulations on combustor and engine design are discussed first in relation to conventional combustors and then in the context of variable-geometry and staged combustors. Both these concepts are founded on emissions reduction by control of flame temperature. Basic approaches to the design of “dry” low NOx and ultra-low NOx combustors are reviewed. At the present time lean, premix, prevaporize, combustion appears to be the only technology available for achieving ultra-low NOx emissions from practical combustors. This concept is discussed in some detail, along with its inherent problems of autoignition, flashback, and acoustic resonance. Attention is also given to alternative methods of achieving ultra-low NOx emissions, notably the rich-bum, quick-quench, lean-burn and catalytic combustors. These concepts are now being actively developed, despite the formidable problems they present in terms of mixing and durability. The final section reviews the various correlations which are now being used to predict the exhaust gas concentrations of the main gaseous pollutant emissions from gas turbine engines. Comprehensive numerical methods have not yet completely displaced these semi-empirical correlations but are nevertheless providing useful insight into the interactions of swirling and recirculating flows with fuel sprays, as well as guidance to the combustion engineer during the design and development stages. Throughout the paper emphasis is placed on the important and sometimes pivotal role played by the fuel preparation process in the reduction of pollutant emissions from gas turbines.

The Role of Fuel Preparation in Low-Emission Combustion

1995 ◽  
Vol 117 (4) ◽  
pp. 617-654 ◽  
Author(s):  
A. H. Lefebvre
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Fuel Injection ◽  
Flame Temperature ◽  
Acoustic Resonance ◽  
Pollutant Emissions ◽  
Alternative Methods ◽  
Nox Emissions ◽  
Oxides Of Nitrogen ◽  
Lean Burn

The attainment of very low pollutant emissions, in particular oxides of nitrogen (NOx), from gas turbines is not only of considerable environmental concern but has also become an area of increasing competitiveness between the different engine manufacturers. For stationary engines, the attainment of ultralow NOx has become the foremost marketing issue. This paper is devoted primarily to current and emerging technologies in the development of ultralow emissions combustors for application to aircraft and stationary engines. Short descriptions of the basic design features of conventional gas turbine combustors and the methods of fuel injection now in widespread use are followed by a review of fuel spray characteristics and recent developments in the measurement and modeling of these characteristics. The main gas-turbine-generated pollutants and their mechanisms of formation are described, along with related environmental risks and various issues concerning emissions regulations and recently enacted legislation for limiting the pollutant levels emitted by both aircraft and stationary engines. The impacts of these emissions regulations on combustor and engine design are discussed first in relation to conventional combustors and then in the context of variable-geometry and staged combustors. Both these concepts are founded on emissions reduction by control of flame temperature. Basic approaches to the design of “dry” low-NOx and ultralow-NOx combustors are reviewed. At the present time lean, premix, prevaporize combustion appears to be the only technology available for achieving ultralow NOx emissions from practical combustors. This concept is discussed in some detail, along with its inherent problems of autoignition, flashback, and acoustic resonance. Attention is also given to alternative methods of achieving ultralow NOx emissions, notably the rich-burn, quick-quench, lean-burn, and catalytic combustors. These concepts are now being actively developed, despite the formidable problems they present in terms of mixing and durability. The final section reviews the various correlations now being used to predict the exhaust gas concentrations of the main gaseous pollutant emissions from gas turbine engines. Comprehensive numerical methods have not yet completely displaced these semi-empirical correlations but are nevertheless providing useful insight into the interactions of swirling and recirculating flows with fuel sprays, as well as guidance to the combustion engineer during the design and development stages. Throughout the paper emphasis is placed on the important and sometimes pivotal role played by the fuel preparation process in the reduction of pollutant emissions from gas turbines.

Design Improvement Survey for NOx Emissions Reduction of a Heavy-Duty Gas Turbine Partially Premixed Fuel Nozzle Operating With Natural Gas: Experimental Campaign

2015 ◽  
Author(s):  
Matteo Cerutti ◽  
Roberto Modi ◽  
Danielle Kalitan ◽  
Kapil K. Singh
Keyword(s):  
Pressure Drop ◽  
Natural Gas ◽  
Gas Turbine ◽  
Pollutant Emissions ◽  
Nox Emissions ◽  
Heavy Duty ◽  
Fuel Nozzle ◽  
Partially Premixed ◽  
Heavy Duty Gas Turbine ◽  
The Impact

As government regulations become increasingly strict with regards to combustion pollutant emissions, new gas turbine combustor designs must produce lower NOx while also maintaining acceptable combustor operability. The design and implementation of an efficient fuel/air premixer is paramount to achieving low emissions. Options for improving the design of a natural gas fired heavy-duty gas turbine partially premixed fuel nozzle have been considered in the current study. In particular, the study focused on fuel injection and pilot/main interaction at high pressure and high inlet temperature. NOx emissions results have been reported and analyzed for a baseline nozzle first. Available experience is shared in this paper in the form of a NOx correlative model, giving evidence of the consistency of current results with past campaigns. Subsequently, new fuel nozzle premixer designs have been investigated and compared, mainly in terms of NOx emissions performance. The operating range of investigation has been preliminarily checked by means of a flame stability assessment. Adequate margin to lean blow out and thermo-acoustic instabilities onset has been found while also maintaining acceptable CO emissions. NOx emission data were collected over a variety of fuel/air ratios and pilot/main splits for all the fuel nozzle configurations. Results clearly indicated the most effective design option in reducing NOx. In addition, the impact of each design modification has been quantified and the baseline correlative NOx emissions model calibrated to describe the new fuel nozzles behavior. Effect of inlet air pressure has been evaluated and included in the models, allowing the extensive use of less costly reduced pressure test campaigns hereafter. Although the observed effect of combustor pressure drop on NOx is not dominant for this particular fuel nozzle, sensitivity has been performed to consolidate gathered experience and to make the model able to evaluate even small design changes affecting pressure drop.

Study of a Rich/Lean Staged Combustion Concept for Hydrogen at Gas Turbine Relevant Conditions

2013 ◽  
Author(s):  
Felipe Bolaños ◽  
Dieter Winkler ◽  
Felipe Piringer ◽  
Timothy Griffin ◽  
Rolf Bombach ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Carbon Capture ◽  
Flame Temperature ◽  
Nox Emissions ◽  
Hydrogen Fuel ◽  
Auto Ignition ◽  
Wide Range ◽  
The Rich

The combustion of hydrogen-rich fuels (> 80 % vol. H2), relevant for gas turbine cycles with “pre-combustion” carbon capture, creates great challenges in the application of standard lean premix combustion technology. The significant higher flame speed and drastically reduced auto-ignition delay time of hydrogen compared to those of natural gas, which is normally burned in gas turbines, increase the risk of higher NOX emissions and material damage due to flashback. Combustion concepts for gas turbines operating on hydrogen fuel need to be adapted to assure safe and low-emission combustion. A rich/lean (R/L) combustion concept with integrated heat transfer that addresses the challenges of hydrogen combustion has been investigated. A sub-scale, staged burner with full optical access has been designed and tested at gas turbine relevant conditions (flame temperature of 1750 K, preheat temperature of 400 °C and a pressure of 8 bar). Results of the burner tests have confirmed the capability of the rich/lean staged concept to reduce the NOx emissions for undiluted hydrogen fuel. The NOx emissions were reduced from 165 ppm measured without staging (fuel pre-conversion) to 23 ppm for an R/L design having a fuel-rich hydrogen pre-conversion of 50 % at a constant power of 8.7 kW. In the realized R/L concept the products of the first rich stage, which is ignited by a Pt/Pd catalyst (under a laminar flow, Re ≈ 1900) are combusted in a diffusion-flame-like lean stage (turbulent flow Re ≈ 18500) without any flashback risk. The optical accessibility of the reactor has allowed insight into the combustion processes of both stages. Applying OH-LIF and OH*-chemiluminescence optical techniques, it was shown that mainly homogeneous reactions at rich conditions take place in the first stage, questioning the importance of a catalyst in the system, and opening a wide range of optimization possibilities. The promising results obtained in this study suggest that such a rich/lean staged burner with integrated heat transfer could help to develop a new generation of gas turbine burners for safe and clean combustion of H2-rich fuels.

scholarly journals Conversion of Liquid to Gaseous Fuel for Prevaporised Premixed Combustion in Gas Turbines

1997 ◽  
Author(s):  
Y. Wang ◽  
L. Reh ◽  
D. Pennell ◽  
D. Winkler ◽  
K. Döbbeling
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Liquid Fuel ◽  
Fuel Injection ◽  
Premixed Combustion ◽  
Fuel Oil ◽  
Injection System ◽  
Nox Emissions ◽  
Combustion Tests

Stationary gas turbines for power generation are increasingly being equipped with low emission burners. By applying lean premixed combustion techniques for gaseous fuels both NOx and CO emissions can be reduced to extremely low levels (NOx emissions <25vppm, CO emissions <10vppm). Likewise, if analogous premix techniques can be applied to liquid fuels (diesel oil, Oil No.2, etc.) in gas-fired burners, similar low level emissions when burning oils are possible. For gas turbines which operate with liquid fuel or in dual fuel operation, VPL (Vaporised Premixed Lean)-combustion is essential for obtaining minimal NOx-emissions. An option is to vaporise the liquid fuel in a separate fuel vaporiser and subsequently supply the fuel vapour to the natural gas fuel injection system; this has not been investigated for gas turbine combustion in the past. This paper presents experimental results of atmospheric and high-pressure combustion tests using research premix burners running on vaporised liquid fuel. The following processes were investigated: • evaporation and partial decomposition of the liquid fuel (Oil No.2); • utilisation of low pressure exhaust gases to externally heat the high pressure fuel vaporiser; • operation of ABB premix-burners (EV burners) with vaporised Oil No.2; • combustion characteristics at pressures up to 25bar. Atmospheric VPL-combustion tests using Oil No.2 in ABB EV-burners under simulated gas turbine conditions have successfully produced emissions of NOx below 20vppm and of CO below 10vppm (corrected to 15% O2). 5vppm of these NOx values result from fuel bound nitrogen. Little dependence of these emissions on combustion pressure bas been observed. The techniques employed also ensured combustion with a stable non luminous (blue) flame during transition from gaseous to vaporised fuel. Additionally, no soot accumulation was detectable during combustion.

Development of a Low NOx Combustor for 300kW-Class Ceramic Gas Turbine (CGT302)

1998 ◽  
Author(s):  
A. Okuto ◽  
T. Kimura ◽  
I. Takehara ◽  
T. Nakashima ◽  
Y. Ichikawa ◽  
...  
Keyword(s):  
Research And Development ◽  
Gas Turbine ◽  
Flow Rate ◽  
Gas Turbines ◽  
Combustion Efficiency ◽  
Development Project ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Nox Emissions

Research and development project of ceramic gas turbines (CGT) was started in 1988 promoted by the Ministry of International Trade and Industry (MITI) in Japan. The target of the CGT project is development of a 300kW-class ceramic gas turbine with a 42 % thermal efficiency and a turbine inlet temperature (TIT) of 1350°C. Three types of CGT engines are developed in this project. One of the CGT engines, which is called CGT302, is a recuperated two-shaft gas turbine for co-generation use. In this paper, we describe the research and development of a combustor for the CGT302. The project requires a combustor to exhaust lower pollutant emissions than the Japanese regulation level. In order to reduce NOx emissions and achieve high combustion efficiency, lean premixed combustion technology is adopted. Combustion rig tests were carried out using this combustor. In these tests we measured the combustor performance such as pollutant emissions, combustion efficiency, combustor inlet/outlet temperature, combustor inlet pressure and pressure loss through combustor. Of course air flow rate and fuel flow rate are controlled and measured, respectively. The targets for the combustor such as NOx emissions and combustion efficiency were accomplished with sufficient margin in these combustion rig tests. In addition, we report the results of the tests which were carried out to examine effects of inlet air pressure on NOx emissions here.

Fuel Flexibility Test Campaign on a 10 MW Class Gas Turbine Equipped With a Dry-Low-NOx Combustion System

2007 ◽  
Author(s):  
Stefano Cocchi ◽  
Michele Provenzale ◽  
Gianni Ceccherini
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Flame Temperature ◽  
Nox Emission ◽  
Pollutant Emissions ◽  
Combustion System ◽  
Fuel Flow ◽  
Fuel Flexibility ◽  
Air Staging

An experimental test campaign, aimed to provide a preliminary assessment of the fuel flexibility of small power gas turbines equipped with Dry Low NOx (DLN) combustion systems, has been carried over a full-scale GE10 prototypical unit, located at the Nuovo-Pignone manufacturing site, in Florence. Such activity is a follow-up of a previous experimental campaign, performed on the same engine, but equipped with a diffusive combustion system. The engine is a single shaft, simple cycle gas turbine designed for power generation applications, rated for 11 MW electrical power and equipped with a DLN silos type combustor. One of the peculiar features of such combustion system is the presence of a device for primary combustion air staging, in order to control flame temperature. A variable composition gaseous fuel mixture has been obtained by mixing natural gas with CO2 up to about 30% vol. inerts concentration. Tests have been carried over without any modification of the default hardware configuration. Tests performed aimed to investigate both ignition limits and combustors’ performances, focusing on hot parts’ temperatures, pollutant emissions and combustion driven pressure oscillations. Results indicate that ignition is possible up to 20% vol. inerts concentration in the fuel, keeping the fuel flow during ignition at moderately low levels. Beyond 20% vol. inerts, ignition is still possible increasing fuel flow and adjusting primary air staging, but more tests are necessary to increase confidence in defining optimal and critical values. Speed ramps and load operation have been successfully tested up to 30% vol. inerts concentration. As far as speed ramps, the only issue evidenced has been risk of flameout, successfully abated by rescheduling combustion air staging. As far as load operation, the combustion system has proven to be almost insensitive to any inerts concentration tested (up to 30% vol.): the only parameter significantly affected by variation in CO2 concentration has been NOx emission. As a complementary activity, a simplified zero-dimensional model for predicting NOx emission has been developed, accounting for fuel dilution with CO2. The model is based on main turbine cycle and DLN combustion system controlling parameters (i.e., compressor pressure ratio, firing temperature, pilot fuel and primary air staging), and has been tuned achieving good agreement with data collected during the test campaign.

scholarly journals Conceptual Studies of a Fuel-Flexible Low-Swirl Combustion System for the Gas Turbine in Clean Coal Power Plants

2010 ◽  
Author(s):  
Kenneth O. Smith ◽  
Peter L. Therkelsen ◽  
David Littlejohn ◽  
Sy Ali ◽  
Robert K. Cheng
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Fuel Injection ◽  
Pollutant Emissions ◽  
Injection System ◽  
Combustion System ◽  
High Hydrogen ◽  
Swirl Combustion ◽  
Auto Ignition

This paper reports the results of preliminary analyses that show the feasibility of developing a fuel flexible (natural gas, syngas and high-hydrogen fuel) combustion system for IGCC gas turbines. Of particular interest is the use of Lawrence Berkeley National Laboratory’s DLN low swirl combustion technology as the basis for the IGCC turbine combustor. Conceptual designs of the combustion system and the requirements for the fuel handling and delivery circuits are discussed. The analyses show the feasibility of a multi-fuel, utility-sized, LSI-based, gas turbine engine. A conceptual design of the fuel injection system shows that dual parallel fuel circuits can provide range of gas turbine operation in a configuration consistent with low pollutant emissions. Additionally, several issues and challenges associated with the development of such a system, such as flashback and auto-ignition of the high-hydrogen fuels, are outlined.

Numerical Study on the Reduction of NOx Emissions From Pulse Detonation Combustion

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Neda Djordjevic ◽  
Niclas Hanraths ◽  
Joshua Gray ◽  
Phillip Berndt ◽  
Jonas Moeck
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Emissions Reduction ◽  
Nox Emissions ◽  
Primary Methods ◽  
Detonation Cell ◽  
Pulse Detonation ◽  
Detonation Combustion

A change in the combustion concept of gas turbines from conventional isobaric to constant volume combustion, such as in pulse detonation combustion (PDC), promises a significant increase in gas turbine efficiency. Current research focuses on the realization of reliable PDC operation and its challenging integration into a gas turbine. The topic of pollutant emissions from such systems has so far received very little attention. Few rare studies indicate that the extreme combustion conditions in PDC systems can lead to high emissions of nitrogen oxides (NOx). Therefore, it is essential already at this stage of development to begin working on primary measures for NOx emissions reduction if commercialization is to be feasible. The present study evaluates the potential of different primary methods for reducing NOx emissions produced during PDC of hydrogen. The considered primary methods involve utilization of lean combustion mixtures or its dilution by steam injection or exhaust gas recirculation. The influence of such measures on the detonability of the combustion mixture has been evaluated based on detonation cell sizes modeled with detailed chemistry. For the mixtures and operating conditions featuring promising detonability, NOx formation in the detonation wave has been simulated by solving the one-dimensional (1D) reacting Euler equations. The study enables an insight into the potential and limitations of considered measures for NOx emissions reduction and lays the groundwork for optimized operation of PDC systems.

Combustion Characteristics of Hydrogen-Methane Hybrid Fuels in Coflow Jet Diffusion Flames

2008 ◽  
Author(s):  
Hui Wu ◽  
Wenxing Zhang ◽  
Kejin Mu ◽  
Yue Wang ◽  
Yunhan Xiao
Keyword(s):  
Gas Turbines ◽  
Flame Temperature ◽  
Flame Length ◽  
Combustion Characteristics ◽  
Pollutant Emissions ◽  
Maximum Temperature ◽  
Production Test ◽  
Pure Hydrogen ◽  
Nox Emissions ◽  
Nature Gas

As the development and increasingly widespread use of IGCC and zero emission energy system, the development of advanced combustion capabilities for gaseous hydrogen and hydrogen rich fuels in gas turbine applications is becoming an area of much great concern. The combustion characteristics of hydrogen rich fuel is very different from nature gas in aspects such as flame stability, flame temperature, combustor acoustics, pollutant emissions, combustor efficiency, and some other important quantities. However, few of these issues are clearly understood by far. The purpose of this paper is to compare in detail the combustion performance of hydrogen-methane hybrid fuels with various volumetric H2 fractions ranging from 0% to 100%. Meanwhile, the comparison of pure H2, pure CH4, and 80%H2+20%CH4 was the emphasis. 80%H2+20%CH4 hybrid gas is selected expressly because its component is approximately equal to the outcome of a hydrogen production test bed of our laboratory, and it is considered by the team to be a potential transition fuel of gas turbines between nature gas and pure hydrogen. Detailed experimental measurements and numerical simulations were conducted using a coflow jet diffusion burner. It was found that in the extent of experiments, when under equal general power, the flame length of hydrogen contained fuels wasn’t much shorter than methane, and didn’t get shorter with the increase of H2 fraction as expected. That was because the shortening tendency caused by the increase of H2 fraction was counteracted partially by the increase of fuel velocity, results of which was the extending of flame length. Maximum temperature of H2 flame was 1733K, which was 30K higher than 80%H2+20%CH4 and 120K higher than CH4. All of the highest temperatures of the three fuels were presented at the recirculation zone of the flame. Although it seemed that the flame of CH4 had the longest dimension compared with H2 contained fuels when observed through photos, the high temperature region of flames was getting longer when increasing H2 fractions. Curves of temperature distribution predicted by all the four combustion models in FLUENT investigated here had a departure away from the experimental data. Among the models, Flamelet model was the one whose prediction was comparatively close to the experimental results. Flame of H2 and 80%H2+20%CH4 had a much better stability than flame of CH4, they could reach a so called recirculating flame phase and never been blew out in the extent of experiments. On the contrary, CH4 flames were blew out easily soon after they were lifted up. Distribution of OH concentration at the root of flames showed that the flame boundary of H2 and 80%H2+20%CH4 was more clearly than CH4. That is to say, at the root of the flame, combustion of H2 was the most intensive one, 80%H2+20%CH4 took the second place, while CH4 was the least. NOx emissions didn’t show a linear relationship with the volumetric fraction of H2, but showed an exponential uptrend instead. It presented a fairly consistent tendency with flame temperature, which proved again there was a strong relationship between flame temperature and NOx emissions in the combustion of hydrogen contained fuels. If adding CH4 into pure H2, NOx concentration would have a 17.2ppm reduction with the first 20% accession, but only 11.1ppm with the later 80% accession. Hence, if NOx emission was the only aspect to be considered, 80%H2+20%CH4 seemed to be a better choice of transition fuel from pure CH4 to pure H2.

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.

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