Hydrogen Enrichment Effects in Gaseous Fuels on Distributed Combustion

2019 ◽  
Author(s):  
Serhat Karyeyen ◽  
Joseph S. Feser ◽  
Ashwani K. Gupta
Keyword(s):  
Oxygen Concentration ◽  
Hydrogen Content ◽  
Reaction Rates ◽  
Flame Speed ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Flame Stability ◽  
Limited Information ◽  
High Hydrogen ◽  
Gaseous Fuels

Abstract High intensity colorless distributed combustion has been a promising combustion technique as it enables much reduced pollutant emissions such as NO and CO, as well as more thermal uniformity, flame stability and combustion efficiency. The main requirement for achieving distributed conditions is to provide controlled entrainment of reactive hot product gases into the fresh mixture prior to ignition. In this way, the oxygen concentration is reduced, which results in lower reaction rates, promoting longer mixing times and volumetric distribution of the reaction zones. Though distributed combustion has been extensively studied for various heat loads and intensities, fuels, geometries, there is limited information related to fuel flexibility. Therefore, it is of interest to investigate hydrogen enriched gaseous fuels for greater understanding of low calorific high flame speed fuels in a distributed combustion system. Three various hydrogen content gaseous fuel (40–60% by volume) were investigated in a swirl-stabilized burner for this study, through the use of either N2 or CO2 as the diluent in order to achieve distributed conditions. The OH* chemiluminescence flame signatures were obtained in the flame front and emissions were measured from the combustor exit. The results showed that both the hydrogen concentration and diluent type considerably impacted the oxygen concentration at which transition to CDC occurred. Distributed conditions were achieved at oxygen concentrations of 10–12% with entrained N2 and 13–15% with entrained CO2 for various gaseous fuels consumed. It was determined that the transition to CDC occurred at a lower oxygen concentration for high hydrogen content fuels due to the higher flame speed of hydrogen. The flame images demonstrated that the flashback propensity of the gaseous fuels were eliminated and enhanced flame stability was achieved under the favorable CDC conditions. For NO pollutant emission, ultra-low NO level was achieved under CDC (less than 1 ppm) while CO pollutant emission decreased gradually with condition approaching distributed conditions, and then increased slightly due to the lower flammability limit and dissociation of CO2.

Measurements of Stretch Statistics at Flame Leading Points for High Hydrogen Content Fuels

2014 ◽  
Author(s):  
Andrew Marshall ◽  
Julia Lundrigan ◽  
Prabhakar Venkateswaran ◽  
Jerry Seitzman ◽  
Tim Lieuwen
Keyword(s):  
Flame Front ◽  
Hydrogen Content ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Fuel Composition ◽  
Mean Flow ◽  
Tangential Strain ◽  
High Hydrogen ◽  
High Hydrogen Content ◽  
Turbulent Flame Speed

Fuel composition has a strong influence on the turbulent flame speed, even at very high turbulence intensities. An important implication of this result is that the turbulent flame speed cannot be extrapolated from one fuel to the next using only the laminar flame speed and turbulence intensity as scaling variables. This paper presents curvature and tangential strain rate statistics of premixed turbulent flames for high hydrogen content fuels. Global (unconditioned) stretch statistics are presented as well as measurements conditioned on the leading points of the flame front. These measurements are motivated by previous experimental and theoretical work that suggests the turbulent flame speed is controlled by the flame front characteristics at these points. The data were acquired with high speed particle image velocimetry (PIV) in a low swirl burner (LSB). We attained measurements for several H2:CO mixtures over a range of mean flow velocities and turbulence intensities. The results show that fuel composition has a systematic, yet weak effect on curvatures and tangential strain rates at the leading points. Instead, stretch statistics at the leading points are more strongly influenced by mean flow velocity and turbulence level. It has been argued that the increased turbulent flame speeds seen with increasing hydrogen content are the result of increasing flame stretch rates, and therefore SL,max values, at the flame leading points. However, the differences observed with changing fuel compositions are not significant enough to support this hypothesis. Additional analysis is needed to understand the physical mechanisms through which the turbulent flame speed is altered by fuel composition effects.

scholarly journals Evolution of Emission Species in an Aero-Engine Turbine Stator

Aerospace ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 11
Author(s):  
André A. V. Perpignan ◽  
Stella Grazia Tomasello ◽  
Arvind Gangoli Rao
Keyword(s):  
Gas Turbines ◽  
Engine Performance ◽  
Energy Transition ◽  
Chemical Reactor ◽  
Reaction Rates ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Operating Pressure ◽  
Performance And Emission ◽  
Turbine Stator

Future energy and transport scenarios will still rely on gas turbines for energy conversion and propulsion. Gas turbines will play a major role in energy transition and therefore gas turbine performance should be improved, and their pollutant emissions decreased. Consequently, designers must have accurate performance and emission prediction tools. Usually, pollutant emission prediction is limited to the combustion chamber as the composition at its outlet is considered to be “chemically frozen”. However, this assumption is not necessarily valid, especially with the increasing turbine inlet temperatures and operating pressures that benefit engine performance. In this work, Computational Fluid Dynamics (CFD) and Chemical Reactor Network (CRN) simulations were performed to analyse the progress of NOx and CO species through the high-pressure turbine stator. Simulations considering turbulence-chemistry interaction were performed and compared with the finite-rate chemistry approach. The results show that progression of some relevant reactions continues to take place within the turbine stator. For an estimated cruise condition, both NO and CO concentrations are predicted to increase along the stator, while for the take-off condition, NO increases and CO decreases within the stator vanes. Reaction rates and concentrations are correlated with the flow structure for the cruise condition, especially in the near-wall flow field and the blade wakes. However, at the higher operating pressure and temperature encountered during take-off, reactions seem to be dependent on the residence time rather than on the flow structures. The inclusion of turbulence-chemistry interaction significantly changes the results, while heat transfer on the blade walls is shown to have minor effects.

scholarly journals Investigation of Hydrogen Content and Dilution Effect on Syngas/Air Premixed Turbulent Flame Using OH Planar Laser-Induced Fluorescence

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1894
Author(s):  
Li Yang ◽  
Wubin Weng ◽  
Yanqun Zhu ◽  
Yong He ◽  
Zhihua Wang ◽  
...  
Keyword(s):  
Hydrogen Content ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Laser Induced Fluorescence ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
High Hydrogen ◽  
Turbulent Flame Speed ◽  
Planar Laser Induced Fluorescence ◽  
Planar Laser

Syngas produced by gasification, which contains a high hydrogen content, has significant potential. The variation in the hydrogen content and dilution combustion are effective means to improve the steady combustion of syngas and reduce NOx emissions. OH planar laser-induced fluorescence technology (OH-PLIF) was applied in the present investigation of the turbulence of a premixed flame of syngas with varied compositions of H2/CO. The flame front structure and turbulent flame velocities of syngas with varied compositions and turbulent intensities were analyzed and calculated. Results showed that the trend in the turbulent flame speed with different hydrogen proportions and dilutions was similar to that of the laminar flame speed of the corresponding syngas. A higher hydrogen proportion induced a higher turbulent flame speed, higher OH concentration, and a smaller flame. Dilution had the opposite effect. Increasing the Reynolds number also increased the turbulent flame speed and OH concentration. In addition, the effect of the turbulence on the combustion of syngas was independent of the composition of syngas after the analysis of the ratio between the turbulent flame speed and the corresponding laminar flame speed, for the turbulent flames under low turbulent intensity. These research results provide a theoretical basis for the practical application of syngas with a complex composition in gas turbine power generation.

Combustion of Hydrogen-Methane-Air-Mixtures in a Generic Triple Swirl Burner: Numerical Studies

2021 ◽  
Author(s):  
Neha Vishnoi ◽  
Agustin Valera-Medina ◽  
Aditya Saurabh ◽  
Lipika Kabiraj
Keyword(s):  
Hydrogen Content ◽  
Energy Demand ◽  
Combustion Process ◽  
Flow Fields ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Temperature Fields ◽  
Nox Emissions ◽  
Swirl Burner ◽  
High Hydrogen

Abstract Ever-increasing energy demand, limited non-renewable resources, requirement for increased operational flexibility, and the need for reduction of pollutant emissions are the critical factors that drive the development of next generation fuel flexible gas turbine combustors. The use of hydrogen and hydrogen-rich fuels such as syngas helps in achieving decarbonisation. However, high temperatures and flame speeds associated with hydrogen might increase the NOx emissions. Humidified combustion presents a promising approach for NOx control. Humidification inhibits the formation of NOx and also allows for operating on hydrogen and hydrogen-rich fuels. The challenge in the implementation of this technology is the combustor (burner) design, which must provide a stable combustion process at high hydrogen content and ultra-wet conditions. In the present work, we investigate the flow field and combustion characteristics of a generic triple swirl burner running on humidified and hydrogen enriched methane-air mixtures. The investigated burner consists of three co-axial co-rotating swirling passages: outer radial swirler stage, and two inner concentric axial swirler stages. Reynold’s Averaged Navier-Stokes (RANS) simulation approach has been utilized here for flow description within the burner and inside the combustor. We present the flow fields from isothermal and lean pre-mixed methane-air reactive simulations based on the characterization of velocity profiles, streamwise shear layers, temperature fields and NOx emissions. Subsequently, we investigate the effect of combustion on flow fields, and flame stabilization for hydrogen enriched methane-air mixtures as a function of hydrogen content. We also investigate the effect of humidified combustion on methane-hydrogen blends and present comparison of temperature estimations and NOx emissions.

KESAN SUDUT PUSARAN TERHADAP PEMBAKARAN MENGGUNAKAN PEMUSAR JEJARIAN DWI ALIRAN

2015 ◽  
Vol 77 (8) ◽  
Author(s):  
Muhammad Roslan Rahim ◽  
Mohammad Nazri Mohd Ja’afar
Keyword(s):  
Swirling Flow ◽  
Combustion Process ◽  
Combustion Efficiency ◽  
Flame Length ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Flame Stability ◽  
Wide Spread ◽  
Blue Colour ◽  
The One

Development of combustion systems which involves retrofitting or design of new burners, is made to reduce the formation of pollutant emissions. The reduction of this pollutant emission results from the complete mixing of fuel and air during the combustion process. Meanwhile, non-complete mixing of fuel and air during combustion process can cause ignition problem and create problems in terms of flame stability and combustion efficiency. This article describes a study on the effects of swirling flow generated by a double radial swirler on flame characteristics that is related to the emission of NO. The double radial swirlers used in this study have the angles of 30°/40°, 30°/50° and 30°/60°. Diesel is used as a fuel in this study. The results show that all double radial swirlers used have different effects on the flame characteristics and temperature profile. From all these double radial swirlers, the one with an angle of 30°/60° produces flame with high temperature, short flame length with blue colour and wide spread.

CFD Investigation of a Lean Premixed Burner Redesign for High Hydrogen Content Syngas Operation

2015 ◽  
Author(s):  
C. Bianchini ◽  
R. Da Soghe ◽  
A. Andreini ◽  
V. Anisimov ◽  
A. Bulli ◽  
...  
Keyword(s):  
Hydrogen Content ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Lookup Table ◽  
Pollutant Emissions ◽  
Chemical Mechanism ◽  
Alternative Methods ◽  
High Hydrogen ◽  
High Hydrogen Content ◽  
Lean Premixed

The continuous challenge to develop more efficient and cleaner combustion systems for energy production, promotes the exploitation of traditional fossil fuels in alternative energy cycles capable of abating pollutant emissions. Integrated coal gasification combined cycle (IGCC) technology for instance permits to convert standard coal and other carbon based fuels into hydrogen-rich syngas. These gases are generally used to fuel standard gas turbine engines typically designed for natural gas combustion. Due to the increased propensity to flashback with high hydrogen content, lean premixed burners usually need a specific redesign to ensure adequate flow velocity at the burner exit section so as to extend lean blow out limits. However design practices for flashback prevention are far from being established especially for these unconventional fuels and it is therefore of interest to rely on CFD analysis to establish flame stabilization process and to predict incipient flashback. The purpose of this work is to assess the accuracy and reliability of a CFD methodology to describe the flame anchoring process and exhaust pollutant emissions in a high hydrogen syngas version of a standard swirled lean premixed burner which has been tested in a tubular test rig. Considered numerical setup is based on the use of the Flamelet-Generated Manifolds (FGM) method which is a good choice to combine computational efficiency and detailed chemistry modelling. This work aims at providing a first assessment of the FGM model as implemented in Fluent v15 in the framework of RANS turbulence approach. Four different operating conditions at increasing pressure levels are tested and a detailed sensitivity analysis of the combustion model is provided exploring flamelet generation parameters, turbulence-chemistry interaction closures and methods to assign progress variable variance. A specifically developed detailed chemical mechanism for H2 was implemented and used to verify NOx emission predicting capabilities of three alternative methods: lookup table generated integrating with presumed PDF, automatic reactor network model based on CFD aero-thermal solution and Fluent native NOx model. Obtained results are validated against available experimental data.

Measurements of Stretch Statistics at Flame Leading Points for High Hydrogen Content Fuels

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Andrew Marshall ◽  
Julia Lundrigan ◽  
Prabhakar Venkateswaran ◽  
Jerry Seitzman ◽  
Tim Lieuwen
Keyword(s):  
Flame Front ◽  
Hydrogen Content ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Fuel Composition ◽  
Mean Flow ◽  
Tangential Strain ◽  
High Hydrogen ◽  
High Hydrogen Content ◽  
Turbulent Flame Speed

Fuel composition has a strong influence on the turbulent flame speed, even at very high turbulence intensities. An important implication of this result is that the turbulent flame speed cannot be extrapolated from one fuel to the next using only the laminar flame speed and turbulence intensity as scaling variables. This paper presents curvature and tangential strain rate statistics of premixed turbulent flames for high hydrogen content (HHC) fuels. Global (unconditioned) stretch statistics are presented as well as measurements conditioned on the leading points of the flame front. These measurements are motivated by previous experimental and theoretical work that suggests the turbulent flame speed is controlled by the flame front characteristics at these points. The data were acquired with high-speed particle image velocimetry (PIV) in a low-swirl burner (LSB). We attained measurements for several H2:CO mixtures over a range of mean flow velocities and turbulence intensities. The results show that fuel composition has a systematic, yet weak effect on curvatures and tangential strain rates at the leading points. Instead, stretch statistics at the leading points are more strongly influenced by mean flow velocity and turbulence level. It has been argued that the increased turbulent flame speeds seen with increasing hydrogen content are the result of increasing flame stretch rates, and therefore, SL,max values, at the flame leading points. However, the differences observed with changing fuel compositions are not significant enough to support this hypothesis. Additional analysis is needed to understand the physical mechanisms through which the turbulent flame speed is altered by fuel composition effects.

Numerical study of the flame stability of premixed methane–air combustion in a combined porous-free flame burner

2018 ◽  
Vol 233 (4) ◽  
pp. 530-544 ◽  
Author(s):  
Seyed Mohammad Hashemi ◽  
Seyed Abdolmehdi Hashemi
Keyword(s):  
Equivalence Ratio ◽  
Numerical Study ◽  
Flame Stabilization ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Flame Stability ◽  
Emission Analysis ◽  
Porous Burner ◽  
Flame Burner ◽  
Stability Limits

Premixed methane–air combustion process within a combined porous-free flame burner was investigated numerically in the present study. The burner consisted of a perforated porous ceramic pellet forming combination of submerged and free flame zones. Nonequilibrium thermal condition between the gas and solid phases was implemented and governing equations were solved in a two-dimensional model using finite volume method. Detailed chemistry based on reduced GRI 3.0 mechanism with 41 reaction steps and 16 species including NOx mechanisms was utilized to simulate the combustion processes and pollutant emissions. In order to investigate the validation of the implemented numerical model, the burner was manufactured and tested. The predicted results were consistent with the experimental data. Comparison of the combined porous-free flame burner with porous burner showed that the flame stability limits of the combined burner were higher than those of porous burner. Multimode heat transfer within the porous medium was perused and the effect of heat recirculation on the flame stabilization was discussed. Investigation of the effect of pore density on the flame stabilization showed that the lower pore densities were desirable in order to improve the flame stability limits. Pollutant emission analysis proved that the NO concentration increased with increasing the equivalence ratio while the minimum quantity of CO concentration was evaluated at an equivalence ratio of 0.6.

scholarly journals Environmental Impact and External Costs Associated with Hub-and-Spoke Network in Air Transport

2021 ◽  
Vol 13 (2) ◽  
pp. 465
Author(s):  
Mengyuan Sun ◽  
Yong Tian ◽  
Yao Zhang ◽  
Muhammad Nadeem ◽  
Can Xu
Keyword(s):  
Environmental Impact ◽  
Living Environment ◽  
Strategic Decision ◽  
Air Transport ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Civil Aviation ◽  
External Costs ◽  
Hub And Spoke ◽  
City Network

Under the background of economic globalization, the air transport industry developed rapidly. It turns out that the city-to-city network has not been able to adapt well to the development of the society, and the hub-and-spoke network came into being. The hub-and-spoke network demonstrates the advantages of reducing the operating costs of airlines to keep a competitive advantage, and by maintaining the interests of airlines in the rapidly developing context. However, during the operation of aircrafts, they consume fuel and spew a great deal of harmful pollutants into the air, which has an adverse impact on the living environment. This paper explores the impact and external costs associated with hub-and-spoke network in air transport from an environmental perspective. With some mathematical models, we construct a hub-and-spoke network and take a quantitative study on the environmental impact of air transport. For calculating pollutant emissions, meteorological conditions were considered to revise the pollutant emission factors of the Engine Emissions Data Base (EEDB) published by International Civil Aviation Organization (ICAO). The environmental external costs measurement model is employed to calculate the externality of toxic gas and greenhouse gas (GHG). In order to make the study more convincing, two alternative networks are computed: hub-and-spoke network and city-to-city network. It is found that the hub-and-spoke network is associated with poorer environmental impact and environmental external costs because of the different network characteristics and the scale of the fleets. Therefore, under the general trend of green aviation, the environmental impact and environmental external costs associated with hub-and-spoke network in air transport provides a certain reference for airlines’ strategic decision-making.

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