Effect of Fuel Dilution on the Structure and Pollutant Emission of Syngas Diffusion Flames

2007 ◽  
Author(s):  
Xin Hui ◽  
Zhedian Zhang ◽  
Kejin Mu ◽  
Yue Wang ◽  
Yunhan Xiao
Keyword(s):  
Diffusion Flames ◽  
Flame Temperature ◽  
Nox Emission ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
No Emission ◽  
Exhaust Temperature ◽  
Fuel Dilution ◽  
Fuel Stream ◽  
Co Emission

Combustion with diluted syngas is important for integrated gasification combined cycle (IGCC) system that attains high efficiency and low pollutant emissions. In syngas diffusion flames, peak flame temperature is higher than that in nature gas flames, so NOx emission is more significant. To achieve low NOx emission, fuel dilution is an effective way. In the present study, Flame structure and emission characteristics were experimentally and numerically studied in various fuel diluted syngas diffusion flames, and H2O, N2 and CO2 were employed as diluents respectively. The purpose of this paper is to better understand the behavior and mechanism of fuel diluted combustion and to provide fundamental data base for the development of syngas combustion techniques. Experiments were conducted by using jet diffusion flames in a model combustor. Flame size, exhaust temperature and emission concentration were measured. It was found that by introducing diluents into fuel stream, the stoichiometric surface was brought inward, namely the flame envelope shrunk due to a relatively low fuel concentration. The exhaust temperature was decreased. The results also indicated that with diluted fuel stream, there was an increase of CO emission and an apparent decrease of NO emission. For the same exhaust temperature, H2O had the most significant influence on NO emission among the three diluents, while CO2 affected CO emission most by inhibiting its oxidation thermally and chemically. Numerical simulations were performed in counterflow diffusion flames by applying Chemkin software. To reveal the mechanisms of various diluents in flames, the detailed chemistry of H2-CO-N2 system was employed. It was found that the concentration of OH radical is important for both NO and CO emissions. The OH concentration is affected not only by the type of diluents but also by the flame temperature, therefore it is determined by the coupling and competition of diluents’ chemical and thermal effects.

scholarly journals A Numerical Study on the Effect of CO Addition on Flame Temperature and NO Formation in Counterflow CH4/Air Diffusion Flames

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Hongsheng Guo ◽  
W. Stuart Neill
Keyword(s):  
Carbon Monoxide ◽  
Strain Rate ◽  
Diffusion Flames ◽  
Numerical Study ◽  
Formation Rate ◽  
Flame Temperature ◽  
No Emission ◽  
No Formation ◽  
Air Diffusion ◽  
Emission Index

A numerical study was carried out to understand the effect of CO enrichment on flame temperature and NO formation in counterflow CH4/air diffusion flames. The results indicate that when CO is added to the fuel, both flame temperature and NO formation rate are changed due to the variations in adiabatic flame temperature, fuel Lewis number, and chemical reaction. At a low strain rate, the addition of carbon monoxide causes a monotonic decrease in flame temperature and peak NO concentration. However, NO emission index first slightly increases, and then decreases. At a moderate strain rate, the addition of CO has negligible effect on flame temperature and leads to a slight increase in both peak NO concentration and NO emission index, until the fraction of carbon monoxide reaches about 0.7. Then, with a further increase in the fraction of added carbon monoxide, all three quantities quickly decrease. At a high strain rate, the addition of carbon monoxide causes increase in flame temperature and NO formation rate, until a critical carbon monoxide fraction is reached. After the critical fraction, the further addition of carbon monoxide leads to decrease in both flame temperature and NO formation rate.

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 A Numerical Study on the Effect of CO Addition on Flame Temperature and NO Formation in Counterflow CH4/Air Diffusion Flames

2007 ◽  
Author(s):  
Hongsheng Guo ◽  
W. Stuart Neill
Keyword(s):  
Carbon Monoxide ◽  
Strain Rate ◽  
Diffusion Flames ◽  
Numerical Study ◽  
Formation Rate ◽  
Flame Temperature ◽  
No Emission ◽  
No Formation ◽  
Air Diffusion ◽  
Emission Index

A numerical study was carried out to understand the effect of carbon monoxide enrichment on flame temperature and NO formation in counterflow methane/air diffusion flames. Detailed chemistry and complex thermal and transport properties were employed. The results indicate that when carbon monoxide is added to the fuel, both flame temperature and NO formation rate are changed due to the variations in adiabatic flame temperature, fuel Lewis number and chemical reaction. The combination effects of three factors result in the different characteristics of flame temperature and NO formation at various strain rates, when carbon monoxide is added. At a low strain rate, the addition of carbon monoxide causes a monotonic decrease in flame temperature and peak NO concentration. However, NO emission index first slightly increases, and then decreases. When the value of strain rate is moderate, the addition of carbon monoxide has negligible effect on flame temperature and leads to a slight increase in both peak NO concentration and NO emission index, until the fraction of carbon monoxide reaches about 0.7. Then with a further increase in the fraction of added carbon monoxide, all three quantities quickly decrease. When strain rate is increased to a value close to the strain extinction limit of pure methane/air diffusion flame, the addition of carbon monoxide causes increase in flame temperature and NO formation rate, until a critical carbon monoxide fraction is reached. After the critical fraction, the further addition of carbon monoxide leads to decrease in both flame temperature and NO formation rate. The paper also analyzed the variation in the mechanism of NO formation, when carbon monoxide is added.

scholarly journals Influence of over fire air system on NOx emissions: An experimental case study

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 2037-2045
Author(s):  
Nihad Hodzic ◽  
Anes Kazagic ◽  
Sadjit Metovic
Keyword(s):  
Emission Reduction ◽  
Nox Emission ◽  
No Emission ◽  
Coal Basin ◽  
Air Supply ◽  
Primary Zone ◽  
Biomass Blend ◽  
Air Staging ◽  
Co Emission

In this work, various combinations of the NO emission influencing factors and their x combined effects in air staging combustion on level of furnace, using over fire air, were investigated in an experimental lab-scale furnace. At this, process temperature were varied in the range from 950?C to 1450?C, excess air ratio in primary zone in the range ? = 0.9 - 1.2, while distance of over fire air nozzles from the burner outlet varied until a 1 given distance of 2/5 of total length of furnace. Basic fuel is brown coal from Middle Bosnia coal basin, mixed in two coal blends and one coal-woody biomass blend, to combine an effect of fuel characteristics variation on NO emission. Results shows that x an average reduction of NO emission over tested temperature range, when using over x fire air against conventional air supply with over fire air switched off, is 26.5%. At this, much more NO emission reduction for two coal blends were occurred at higher x temperatures ? at 1350?C and above, where an average NO emission reduction is x 32.5%. Furthermore, it was found that the NO emission decreased with an increase in x distance of over fire air nozzles from the outlet level of burner until a distance of 1/3 of total furnace length; with further increase of the distance, NOx emission is stabilised and no further effect to NOx emission reduction was observed, while CO emission and unburnt increased.

Effect of the exhaust thermal insulation on the engine efficiency and the exhaust temperature under transient conditions

2020 ◽  
pp. 146808742096120
Author(s):  
Francisco Jose Arnau ◽  
Jaime Martín ◽  
Pedro Piqueras ◽  
Ángel Auñón
Keyword(s):  
Treatment Effectiveness ◽  
Internal Surface ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Exhaust Manifold ◽  
Test Cycle ◽  
One Dimensional ◽  
Exhaust Temperature ◽  
Engine Efficiency ◽  
Exhaust Line

As well as new advances in the after-treatment systems are required to achieve the new pollutant emission requirements, new designs of the exhaust line can be considered in order to increase the engine efficiency and the after-treatment effectiveness. In the present work, a one-dimensional gas dynamic model has been used to carry out a simulation study comparing several exhaust insulation solutions. This solutions include the insulation of the exhaust ports, the exhaust manifold, the internal surface of the turbine volute, the turbine external housing, as well as different combinations of these solutions. A transient analysis has been done in order to evaluate the increment in the exhaust gases temperature, fuel economy and pollutant emission levels over the WLTC (Worldwide harmonized Light vehicles Test Cycle) at three different temperature conditions. As a conclusion, a 12% increment in the turbine outlet gas enthalpy can be achieved by insulating both the exhausts ports and the exhaust manifold. Moreover, more than 30% less pollutant emissions are released to the environment with this setup.

Simulation of NO Formation in Hydrogen-Air Counterflow Diffusion Flame

2013 ◽  
Vol 284-287 ◽  
pp. 937-943
Author(s):  
Yan Peng Wang ◽  
Pei Yong Wang
Keyword(s):  
Carbon Dioxide ◽  
Numerical Simulation ◽  
Diffusion Flames ◽  
Flame Temperature ◽  
No Emission ◽  
Practical Applications ◽  
No Formation ◽  
Radical Concentration ◽  
Global Environmental ◽  
Counterflow Diffusion Flame

The combustion of hydrocarbon fuels produces large amounts of carbon dioxide. In order to cope with the challenge of greenhouse effect and global environmental protection. H2, as a cleaner and more energy-burning fuel, is being considered in many of the practical applications of combustion equipments. However, H2 fuel combustion will still produce pollutant NOx. Thus, the study of NOx emission is one of the most important topics in H2 combustion. With the classical counterflow burner, a numerical simulation of NO emission was carried out on the H2 diffusion flames. The stretch effects on flame temperature, NO concentration, and EINO are analyzed; the contribution of different NO generation routs are also quantified and analyzed. The major parameters influencing NO emission are flame temperature, radical concentration, and residence time, the observed relationship between stretch rate and NO emission is explained with the three major parameters.

Backward-Inclined Diffusion Jet Flames in Crossflow at Low Jet-to-Crossflow Momentum Flux Ratios

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Dickson Bwana Mosiria ◽  
Rong Fung Huang ◽  
Ching Min Hsu
Keyword(s):  
Inclination Angle ◽  
Momentum Flux ◽  
Diffusion Flames ◽  
Thermal Power ◽  
Flux Ratio ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Jet Flames ◽  
Air Mixing ◽  
Flame Flashback

In the design of gas turbine combustors, efforts are engineered toward reducing the combustion pollutant emission levels. The pollutant emissions can be reduced by premixing the fuel and the air prior to ignition. However, the main challenges encountered with premixing are flame flashback and blowout, thus, the preference of diffusion flames. In this study, flame behavior, flow patterns, and thermochemical fields of backward-inclined diffusion jet flames in crossflow at low jet-to-crossflow momentum flux ratio of smaller than 0.04 were studied in a wind tunnel. The backward-inclination angle was varied within 0–50 deg. The flames presented three characteristic modes: crossflow dominated flame (low backward inclination angle) denoted by a large down-washed recirculation flame, transitional flame (mediate backward inclination angle) identified by a recirculation flame and a tail flame, and jet dominated flame (high backward inclination angle) characterized by a blue flame base, a yellow tail flame, and the absence of a recirculation flame. Short flames are detected in the regime of the crossflow dominated flames—an indication of improved fuel–air mixing. The findings suggest that for low exhaust emissions which are vigorously pursued in the aviation and thermal power plant industries, especially during low-load operations, the jet dominated flames are the preferable flames as they generate low unburned hydrocarbon, carbon monoxide, and nitric oxide emissions compared to the other flames.

scholarly journals Experimental and numerical studies on combustion characteristics of N 2 -diluted CH 4 and O 2 diffusion combustion in a packed bed

2019 ◽  
Vol 6 (9) ◽  
pp. 190492 ◽  
Author(s):  
Houping Li ◽  
Junrui Shi ◽  
Mingming Mao ◽  
Yongqi Liu
Keyword(s):  
Diffusion Processes ◽  
Packed Bed ◽  
Gas Diffusion ◽  
Combustion Characteristics ◽  
Pollutant Emission ◽  
Diffusion Combustion ◽  
No Emission ◽  
Numerical Studies ◽  
And Diffusion ◽  
Co Emission

Experimental and numerical studies were conducted to determine the combustion characteristics of gas diffusion combustion in a porous combustor packed with 2.5 mm or 3.5 mm alumina pellets, special attention being focused on the effect of packed bed height ( h ) on combustion, NO and CO emissions. The pollutant emission of diffusion filtration combustion is studied with different packed bed lengths in the range of 40 mm ≤ h ≤ 240 mm, fixed excess air ratio of 1.88 and fixed gas inlet velocity of 0.06 m s −1 . Results show that both immersed and surface flames coexist in the combustor. Although porous media enhance the mixing and diffusion processes, the diffusion flame shape is still observed from the side and top views of the combustor, and the diffusion filtration retains properties of diffusion combustion. The immersed flame is always observed with increase in h , whereas the height of surface flame decreases. The NO emission decreases sharply when h is increased from 40 mm to 120 mm. However, the NO emission decreases slightly when h > 120 mm. In the investigated range of h , it is shown that h has a significant influence on the CO emission, an increase in h leading to a constant increase in CO for the combustors packed with 2.5 mm or 3.5 mm pellets. The maximum CO emission is 662 ppm and the minimum value is 67 ppm. In the scope of this study, the temperature on the external wall of the combustor reaches 434–513°C.

Effects of Location and Direction of Diluent Injection on Radiation and Pollutant Emissions of a Burning Spray

1989 ◽  
Vol 111 (1) ◽  
pp. 16-21 ◽  
Author(s):  
R. Puri ◽  
S. R. Gollahalli
Keyword(s):  
Diffusion Flames ◽  
Flame Length ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Emission Characteristics ◽  
Temperature Profiles ◽  
Spray Flame ◽  
Nitric Oxide Emission ◽  
Radial Injection ◽  
Thermochemical Processes

Introduction of diluents into diffusion flames is an effective method of changing their combustion and pollutant emission characteristics. Since the dominant thermochemical processes vary from region to region of a burning spray, diluent injection at different locations of a flame can affect its overall characteristics differently. This study examines the effects of location and orientation of N2 injection into an air-atomized kerosene spray flame. Flame length, radiant emission, temperature profiles, flame opacity, and concentration profiles of NO, CO, and soot are measured. The overall emission indexes of NO, CO, and soot are calculated. Results show that the diluent injection in the axial downstream direction is superior to the radial injection from the point of reducing heat loss to the combustor walls. The location of injection affects flame characteristics substantially. Injection of diluent into midflame region produces largest reductions in radiation, flame length, and emissions of soot and CO. Nitric oxide emission does not depend significantly on the location of injection.

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