Experimental study of flame zones variations of biogas enriched with hydrogen

Enriching biogas with hydrogen could enable conventional natural gas systems to be used for clean energy. This technique has generally been evaluated using laboratory devices, so this study addresses a conventional combustion system, consisting of a 100 kW burner fed with biogas-hydrogen mixtures instead of natural gas. Flame behavior and ignition behavior were investigated. The flame structure was analyzed by infrared thermography. The tests were performed with three different mixtures of CH₄–CO₂ recreating an energetically rich biogas, 30% CO₂ (BG70), standard biogas 40% CO₂ (BG60) and poor biogas 50% CO₂ (BG60). Then, each biogas type was enriched with hydrogen up to 20%. Major improvements were obtained between 5% and 10% hydrogen composition since the flame stability increases considerably. Flame structure closest to natural gas flame was achieved for BG60 and BG70 at 10% H₂. However, the flame temperature remained lower than that of natural gas in all cases.     

Enhancement of biogas/air combustion by hydrogen addition at elevated temperatures

In this study, combustion characteristics of various biogas/air mixtures with hydrogen addition at elevated temperatures were experimentally investigated using bunsen burner method. Methane, CH₄, was diluted with different concentrations of carbon dioxide, CO₂, 30 to 40% by volume, to prepare the biogas for testing. It is followed by the hydrogen, H₂, enrichment within the range of 0 to 40% by volume and the temperature elevation of unburned gas till 440 K. Blowoff velocities were measured by lowering the jet velocity until a premixed flame could be stabilized at the nozzle exit, while laminar burning velocities were calculated by analyzing the shape of the directly captured premixed bunsen flames. The results showed that hydrogen had a positive effect on the blowoff velocity for all three fuel samples. Nonlinear growth of the blowoff velocity with hydrogen addition was associated to the dominance of methane-inhibited hydrogen combustion process. It was also observed that the increase in the initial temperature of the unburned mixture led to a linear increase of the blowoff velocity. Moreover, specific changes in flame structure such as flame height, standoff distance, and the existence of tip opening were attributed to the change in the blowoff velocity. The effect of CO₂ content in the mixture was examined with regards to laminar burning velocity for all compositions. The outcome of the experiment showed that the biogas mixture with higher content of CO₂ possessed lower values of laminar burning velocity over the wide range of equivalence ratios. A reduced GRI-Mech 3.0 was used to simulate the combustion of biogas/air mixtures with different compositions using ANSYS Fluent. The numerically simulated stable conical flames were compared with the experimental flames, in terms of flame structure, showing that the reduced GRI-Mech 3.0 was suitable for modeling the combustion of biogas/air mixtures.     

Experimental investigation of the stability and emission characteristics of premixed formic acid-methane-air flames in a swirl combustor

Formic acid (FA) is a potential hydrogen energy carrier and low-carbon fuel by reversing the decomposition products, CO₂ and H_2, back to restore FA without additional carbon release. However, FA-air mixtures feature high ignition energy and low flame speed; hence stabilizing FA-air flames in combustion devices is challenging. This study experimentally investigates the flame stability and emission of swirl flames fueled with pre-vaporized formic acid-methane blends over a wide range of formic acid fuel fractions. Results show that by using a swirl combustor, the premixed formic acid-methane-air flames could be stabilized over a wide range of FA fuel fractions, Reynolds numbers, and swirl numbers. The addition of formic acid increases the equivalence ratios at which the flashback and lean blowout occur. When Reynolds number increases, the equivalence ratio at the flashback limit increases, but that decreases at the lean blowout limit. Increasing the swirl number has a non-monotonic effect on stability limits variation because increasing the swirl number changes the axial velocity on the centerline of the burner throat non-monotonically. In addition, emission characteristics were investigated using a gas analyzer. The CO and NO concentrations were below 20 ppm for all tested conditions, which is comparable to that seen with traditional hydrocarbon fuels, which is in favor of future practical applications with formic acid.     

Investigation of flame characteristics using various design parameters in a pulverized coal burner for oxy‐fuel retrofitting

In oxy‐coal combustion for carbon capture and storage, oxygen and recirculated CO₂ are used as oxidizers instead of air to produce CO₂‐rich flue gas. Owing to differences between the physical and chemical properties of CO₂ and N₂, the development of a burner and boiler system based on fundamental understanding of the flame type, heat transfer, and NOx emission is required. In this study, computational fluid dynamic analysis incorporating comprehensive coal conversion models was performed to investigate the combustion characteristics of a 30 MWth tangential vane swirl pulverized coal burner. Various burner design parameters were evaluated, including the influence of the burner geometry on the swirl strength, direct O₂ injection, and O₂ concentrations in the primary and secondary oxidizers. The flame characteristics were sensitive to the oxygen concentration in the primary oxidizer. The performance of direct O₂ injection around the primary oxidizer with low O₂ concentration was dependent on the mixing of the fuel and oxidizer. The predictions showed that swirl number adjustment and careful direct oxygen injection design are essential for retrofitting air‐firing pulverized coal burners as oxy‐firing burners.     

MILD combustion of hydrogenated biogas under several operating conditions in an opposed jet configuration

MILD combustion of biogas takes its importance firstly from the combustion process that diminishes significantly fuel consumption and reduces emissions and secondly from the use of biogas which is a renewable fuel. In this paper, the influence of several operating conditions (namely biogas composition, hydrogen enrichment and oxidizer dilution) is studied on flame structure and emissions. The investigation is conducted in MILD regime with a special focus on chemical effects of CO₂ in the oxidizer. Opposed jet diffusion combustion configuration is adopted. The combustion kinetics is described by the Gri 3.0 mechanism and the Chemkin code is used to solve the problem.It is found that oxygen reduction has a significant effect on flame temperature and emissions while less sensitivity corresponds to hydrogen enrichment in MILD combustion regime. Temperature and species are considerably reduced by oxygen decrease in the oxidizer and augmented by hydrogen addition to the fuel. The maximum values of temperature and species are not influenced by the composition of the biogas in MILD regime. Blending biogas with hydrogen can be used to sustain MILD combustion at very low oxygen concentration in the fuel.In MILD combustion regime, the chemical effect of CO₂ in the oxidizer stream reduces considerably the flame temperature and species production, except CO which is enhanced. For high amounts of CO₂ in the oxidizer, the chemical effect of CO₂ becomes negligible.     

Effects of synthetic gas constituents on combustion and emission behavior of premixed H2/CO/CO2/CNG mixture flames

In this study, effects of synthetic gas constituents on combustion and emission behavior of premixed H₂/CO/CO₂/CNG blending synthetic gas flames were experimentally investigated in a swirl stabilized laboratory scale combustor. Effects of these constituents on flashback and blowout equivalence ratios of respective mixtures were also determined. Firstly, mixtures of CNG/H₂/CO with varying H₂/CO ratios were tested and then each mixture was diluted with the same amount of CO₂ (20% by volume) to better represent synthetic gas. H₂/CO ratios of tested gas mixtures were so adjusted that heating value of each gas mixture was low, moderate or high. Combustion behavior of such mixtures was evaluated with respect to measured axial and radial temperature values. Moreover, emission behavior was analyzed by means of emitted CO, CO₂ and NO_x levels. Flame temperature measurements were conducted with B and K type thermocouples. Emission measurements were performed with a flue gas analyzer, which was equipped with a ceramic coated probe, as well. Results of this study revealed the great impact of gas composition on combustion and emission behavior of studied flames. Two main findings are: H₂/CO ratio slightly alters temperature distribution throughout combustor, while hydrogen reaction kinetics play the most significant role in synthetic gas combustion (1), CO₂ addition tremendously increases emissions of CO (2).     

Mechanism analysis on the pulverized coal combustion flame stability and NOx emission in a swirl burner with deep air staging

Low NOx burner and air staged combustion are widely applied to control NOx emission in coal-fired power plants. The gas-solid two-phase flow, pulverized coal combustion and NOx emission characteristics of a single low NOx swirl burner in an existing coal-fired boiler was numerically simulated to analyze the mechanisms of flame stability and in-flame NOx reduction. And the detailed NOx formation and reduction model under fuel rich conditions was employed to optimize NOx emissions for the low NOx burner with air staged combustion of different burner stoichiometric ratios. The results show that the specially-designed swirl burner structures including the pulverized coal concentrator, flame stabilizing ring and baffle plate create an ignition region of high gas temperature, proper oxygen concentration and high pulverized coal concentration near the annular recirculation zone at the burner outlet for flame stability. At the same time, the annular recirculation zone is generated between the primary and secondary air jets to promote the rapid ignition and combustion of pulverized coal particles to consume oxygen, and then a reducing region is formed as fuel-rich environment to contribute to in-flame NO_X reduction. Moreover, the NOx concentration at the outlet of the combustion chamber is greatly reduced when the deep air staged combustion with the burner stoichiometric ratio of 0.75 is adopted, and the CO concentration at the outlet of the combustion chamber can be maintained simultaneously at a low level through the over-fired air injection of high velocity to enhance the mixing of the fresh air with the flue gas, which can provide the optimal solution for lower NOx emission in the existing coal-fired boilers.     

Combustion and emission performances of coconut,palm and soybean methyl esters under reacting spray flame conditions

The spray combustion characteristics of coconut (CME), palm (PME) and soybean (SME) biodiesels/methyl esters were compared with diesel by using an axial swirl flame burner. Atomisation of the liquid fuels was achieved via an airblast-type nozzle with varied atomising air-to-liquid ratios (ALR) of 2–2.5. The fully developed sprays were mixed with strongly swirled air to form combustible mixtures prior to igniting at the burner outlet. Under fuel-lean condition, biodiesel spray flames exhibited bluish flame core without the yellowish sooty flame brush, indicating low sooting tendency as compared to baseline diesel. Increasing the atomising air led to the reduction of flame length but increase in flame intensity. Measurements of post-combustion emissions show that SME produced higher NO as compared to CME and PME due to higher degree of unsaturation, while the most saturated CME showed the lowest NO and CO emissions amongst the biodiesels tested across all equivalence ratios. By preheating the main swirl air to 250 °C, higher emissions of NO, CO and CO₂ were observed for biodiesels. Higher ALR led to reduced NO and CO emissions regardless of the fuel used, making it a viable strategy to resolve the simultaneous NOCO reduction conundrum. This work shows that despite different emission characteristics exhibited by biodiesels produced from different feedstock, they are in principle potential supplemental fuels for practical combustion systems. The pollutants emitted can be mitigated by operating at higher ALR in a twin-fluid based swirl combustor.     

An experimental comparative study of the stabilization mechanism of biogas-hydrogen diffusion flame

This work describes an experimental study of the effect of hydrogen addition on the stabilization characteristics of laminar biogas diffusion flame. The focus is to identify and compare various factors influencing the blowoff process. Three compositions of biogas, BG₄₀, BG₅₀ and BG₆₀ were considered and the amount of hydrogen added was varied from 5% to 25% of the biogas by volume.With increasing hydrogen addition, the critical flow velocity beyond which the flame blows off increases faster than the laminar burning velocity (LBV) does, indicating that flame stabilization is not solely dependent on laminar burning velocity. An exponential relationship is observed between LBV and flame propagation speed. Therefore, both flame propagation speed and LBV, together with other factors, contribute to flame stabilization. The reason for no stable lift for either biogas or H₂-biogas flame is analyze by Schmidt number calculation, and the results agree with the literature. Also found is that hydrogen added to biogas accelerates the fuel mass diffusion, which may play an important role for stabilization of the nozzle-attached flame.The CO₂-C₃H₈ and BG₆₀ flames were compared to exclude the possible dominant role played by insufficient heat release and/or excessive heat loss due to CO₂ present in biogas. Tested on varied-size burners show that flame stabilization depends on burner pore size, where larger diameter allows better flame stability. The universal equation for predicting blowout/blowoff velocity in the literature was found to be invalid for H₂-enriched biogas flame and a new scaling law was put forwards.     

Effect of hydrogen enrichment on combustion characteristics of methane swirling and non-swirling inverse diffusion flame

Influence of hydrogen addition on appearance of swirling and non-swirling inverse diffusion flame (IDF) along with emissions characteristics are investigated experimentally. The combustion characteristics including flame length, axial and radial temperature variation, and noise level are analysed for hydrogen addition in methane by mass basis for constant energy input and by volume basis for constant volumetric fuel flow rate. Hydrogen addition in methane IDF produces shorter flame by compressing entrainment zone, mixing zone, reaction zone, and post-combustion zone. Hydrogen addition shift these zones towards fuel and air exit from the burner. Enrichment of methane with hydrogen on a mass basis up to 6% reduces CO emission considerably and increases NO_x emission moderately. Effect of H₂ addition on combustion and emission characteristics is more prominent in non-swirling IDF. Combustion noise is augmented with the hydrogen addition and the magnitude of sound level depends on the hydrogen concentration.     

Influence of hydrogen addition to pipeline natural gas on the combustion performance of a cooktop burner

Displacing pipeline natural gas with renewable hydrogen is a promising way to reduce the emission of carbon dioxide, which is a major greenhouse gas. However, due to significantly differing characteristics of hydrogen and natural gas, such as flame speed, adiabatic flame temperature and stability limits, the combustion performance of hydrogen/natural gas mixture differs from pure natural gas. From the perspective of residential end users, a key question is: how much hydrogen can be injected into the pipeline natural gas without influencing the performance of the residential burners? A representative cooktop burner is selected to study the influence of hydrogen addition on the combustion and cooking performance. Flashback limits, ignition time, flame characteristics, cooking performance, combustion noise, burner temperature, and various emissions (NO, NO₂, N₂O, CO, unburned hydrocarbon (UHC), NH₃) are evaluated for different levels of hydrogen addition. According to the experimental results, the combustion performance of the cooktop burner is not significantly affected with up to about 15% hydrogen addition by volume, which shows the feasibility of utilizing hydrogen on existing cooking appliances without any modification. The experiment methodologies and results in this study will serve as a reference for future test and emission regulation standards on domestic burners.     

Frontiers in combustion techniques and burner designs for emissions control and CO2 capture: A review

The use of fossil fuel is expected to increase significantly by midcentury because of the large rise in the world energy demand despite the effective integration of renewable energies in the energy production sector. This increase, alongside with the development of stricter emission regulations, forced the manufacturers of combustion systems, especially gas turbines, to develop novel combustion techniques for the control of NO_x and CO₂ emissions, the latter being a greenhouse gas responsible for more than 60% to the global warming problem. The present review addresses different burner designs and combustion techniques for clean power production in gas turbines. Combustion and emission characteristics, flame instabilities, and solution techniques are presented, such as lean premixed air‐fuel (LPM) and premixed oxy‐fuel combustion techniques, and the combustor performance is compared for both cases. The fuel flexibility approach is also reviewed, as one of the combustion techniques for controlling emissions and reducing flame instabilities, focusing on the hydrogen‐enrichment and the integrated fuel‐flexible premixed oxy‐combustion approaches. State‐of‐the‐art burner designs for gas turbine combustion applications are reviewed in this study, including stagnation point reverse flow (SPRF) burner, dry low NO_x (DLN) and dry low‐emission (DLE) burners, EnVironmental burners (including EV, AEV, and SEV burners), perforated plate (PP) burner, and micromixer (MM) burner. Special emphasis is made on the MM combustor technology, as one of the most recent advances in gas turbines for stable premixed flame operation with wide turndown and effective control of NO_x emissions. Since the generation of pure oxygen is prerequisite to oxy‐combustion, oxygen‐separation membranes became of immense importance either for air separation for clean oxy‐combustion applications or for conversion/splitting of the effluent CO₂ into useful chemical and energy products. The different carbon‐capture technologies, along with the most recent carbon‐utilization approaches towards CO₂ emissions control, are also reviewed.     

Characterization of biogas-hydrogen premixed flames using Bunsen burner

Experimental study is conducted to clarify the effects of hydrogen addition to biogas and hydrogen fraction in the biogas-H₂ mixture on the stability, thermal and emission characteristics of biogas-H₂-air premixed flames using a 9 mm-ID-tube Bunsen burner. Variation in biogas composition is allowed to range from BG₆₀ (60%CH₄–40%CO₂), down to BG₅₀ (50%CH₄–50%CO₂) and to BG₄₀ (40%CH₄–60%CO₂). For each biogas, the fraction of hydrogen in the biogas-H₂ mixture is varied from 10% to 50%. The results show that upon hydrogen addition and increasing hydrogen fraction in the fuel mixture, there are corresponding changes in flame stability, laminar burning velocity, flame tip temperature and CO pollutant emission.     

Emission characteristics and axial flame temperature distribution of producer gas fired premixed burner

This paper presents the emission characteristics and axial flame temperature distribution of producer gas fired premixed burner. The producer gas fired premixed burner of 150 kW capacity was tested on open core throat less down draft gasifier system in the present study. A stable and uniform flame was observed with this burner. An instrumented test set up was developed to evaluate the performance of the burner. The conventional bluff body having blockage ratio of 0.65 was used for flame stabilization. With respect to maximum flame temperature, minimum pressure drop and minimum emissions, a swirl angle of 60° seems to be optimal. The experimental results also showed that the NO_x emissions are inversely proportional to swirl angle and CO emissions are independent of swirl angle. The minimum emission levels of CO and NO_x are observed to be 0.167% and 384 ppm respectively at the swirl angle of 45–60°. The experimental results showed that the maximum axial flame temperature distribution was achieved at A/F ratio of 1.0. The adiabatic flame temperature of 1653 °C was calculated theoretically at A/F ratio of 1.0. Experimental results are in tune with theoretical results. It was also concluded that the CO and UHC emissions decreases with increasing A/F ratio while NO_x emissions decreases on either side of A/F ratio of 1.0.     

Hydrogen addition effects in a confined swirl-stabilized methane-air flame

The effect of hydrogen addition in methane-air premixed flames has been examined from a swirl-stabilized combustor under confined conditions. The effect of hydrogen addition in methane-air flame has been examined over a range of conditions using a laboratory-scale premixed combustor operated at 5.81 kW. Different swirlers have been investigated to identify the role of swirl strength to the incoming mixture. The flame stability was examined for the effect of amount of hydrogen addition, combustion air flow rates and swirl strengths. This was carried out by comparing adiabatic flame temperatures at the lean flame limit. The combustion characteristics of hydrogen-enriched methane flames at constant heat load but different swirl strengths have been examined using particle image velocimetry (PIV), micro-thermocouples and OH chemiluminescence diagnostics that provided information on velocity, thermal field, and combustion generated OH species concentration in the flame, respectively. Gas analyzer was used to obtain NO_x and CO concentration at the combustor exit. The results show that the lean stability limit is extended by hydrogen addition. The stability limit can reduce at higher swirl intensity to the fuel-air mixture operating at lower adiabatic flame temperatures. The addition of hydrogen increases the NO_x emission; however, this effect can be reduced by increasing either the excess air or swirl intensity. The emissions of NO_x and CO from the premixed flame were also compared with a diffusion flame type combustor. The NO_x emissions of hydrogen-enriched methane premixed flame were found to be lower than the corresponding diffusion flame under same operating conditions for the fuel-lean case.     

Flame characteristics of hydrogen-enriched methane–air premixed swirling flames

The effect of hydrogen addition in methane–air premixed flames has been examined from a swirl-stabilized combustor under unconfined flame conditions. Different swirlers have been examined to investigate the effect of swirl intensity on enriching methane–air flame with hydrogen in a laboratory-scale premixed combustor operated at 5.81 kW. The hydrogen-enriched methane fuel and air were mixed in a pre-mixer and introduced into the burner having swirlers of different swirl vane angles that provided different swirl strengths. The combustion characteristics of hydrogen-enriched methane–air flames at fixed thermal load but different swirl strengths were examined using particle image velocimetry (PIV), OH chemiluminescence, gas analyzers, and micro-thermocouple diagnostics to provide information on flow field, combustion generated OH radical and gas species concentration, and temperature distribution, respectively. The results show that higher combustibility of hydrogen assists to promote faster chemical reaction, raises temperature in the reaction zone and reduces the recirculation flow in the reaction zone. The upstream of flame region is more dependent on the swirl strength than the effect of hydrogen addition to methane fuel. At lower swirl strength condition the NO concentration in the reaction zone reduces with increase in hydrogen content in the fuel mixture. Higher combustibility of hydrogen accelerates the flow to reduce the residence time of hot product gases in the high temperature reaction zone. At higher swirl strength the NO concentration increases with increase in hydrogen content in the fuel mixture. The effect of dynamic expansion of the gases with hydrogen addition appears to be more dominant to reduce the recirculation of relatively cooler gases into the reaction zone. NO concentration also increases with decrease in the swirl strength.     

Effects of turbulator angle and hydrogen addition on a biogas turbulent diffusion flame

This study is concerned with combustion characteristics of a biogas under varying turbulator angle conditions and hydrogen addition in a combustor. Turbulator angles have been changed 15°–45° at intervals of 15°. Investigations have been performed by using a CFD code. PDF/Mixture Fraction combustion and k-? standard turbulence models were used during predictions. The predicted temperature and emission profiles of the biogas are compared with the existing experimental measurements under turbulator angle of 15°. These predictions are in good agreement with the measurements in terms of distributions and values. It has been determined that percentage differences between the measured and the predicted values vary from about 0% to 12%. Then, predictions have been performed under 30° and 45° of turbulator angle cases and compared with each other. The effect of the hydrogen addition to the biogas fuel on combustion performances of the biogas has also been studied in the present study. Findings show that changes in turbulator angles highly affect the temperature and emission profiles of the biogas throughout the combustion chamber. Especially, the flame temperature zones move to the downstream of the burner. It may be also said that the flame temperatures of the biogas increase as the turbulator angle is changed due to better fuel–air mixture. In addition to these findings, it is demonstrated that the axial temperature levels increase as the hydrogen is added into the biogas.     

The effect of hydrogen containing fuel blends upon flashback in swirl burners

Lean premixed swirl combustion is widely used in gas turbines and many other combustion Processes due to the benefits of good flame stability and blow off limits coupled with low NO_x emissions. Although flashback is not generally a problem with natural gas combustion, there are some reports of flashback damage with existing gas turbines, whilst hydrogen enriched fuel blends, especially those derived from gasification of coal and/or biomass/industrial processes such as steel making, cause concerns in this area. Thus, this paper describes a practical experimental approach to study and reduce the effect of flashback in a compact design of generic swirl burner representative of many systems. A range of different fuel blends are investigated for flashback and blow off limits; these fuel mixes include methane, methane/hydrogen blends, pure hydrogen and coke oven gas. Swirl number effects are investigated by varying the number of inlets or the configuration of the inlets. The well known Lewis and von Elbe critical boundary velocity gradient expression is used to characterise flashback and enable comparison to be made with other available data.Two flashback phenomena are encountered here. The first one at lower swirl numbers involves flashback through the outer wall boundary layer where the crucial parameter is the critical boundary velocity gradient, G_f. Values of G_f are of similar magnitude to those reported by Lewis and von Elbe for laminar flow conditions, and it is recognised that under the turbulent flow conditions pertaining here actual gradients in the thin swirl flow boundary layer are much higher than occur under laminar flow conditions. At higher swirl numbers the central recirculation zone (CRZ) becomes enlarged and extends backwards over the fuel injector to the burner baseplate and causes flashback to occur earlier at higher velocities. This extension of the CRZ is complex, being governed by swirl number, equivalence ratio and Reynolds Number. Under these conditions flashback occurs when the cylindrical flame front surrounding the CRZ rapidly accelerates outwards to the tangential inlets and beyond, especially with hydrogen containing fuel mixes. Conversely at lower swirl numbers with a modified exhaust geometry, hence restricted CRZ, flashback occurs through the outer thin boundary layer at much lower flow rates when the hydrogen content of the fuel mix does not exceed 30%. The work demonstrates that it is possible to run premixed swirl burners with a wide range of hydrogen fuel blends so as to substantially minimise flashback behaviour, thus permitting wider used of the technology to reduce NOx emissions.     

3D numerical modelling of turbulent biogas combustion in a newly generated 10 KW burner

This study concentrates on the 3D numerical modelling of combustion of different biogases in a generated burner and combustor. The main goal of this study is to investigate the combustion characteristics (such as temperature and emissions) of biogases through a combustor due to depletion of natural gas. Moreover, the effect of the preheated air on flame temperatures of biogases have been studied in the present study. Finally, the effect of H₂S amount in biogas on SO₂ emissions has been investigated within these predictions. The numerical modelling of turbulent diffusion flames has been performed by using the standard k–ε model of turbulent flow, the PDF/Mixture Fraction combustion model and P-1 radiation model in the combustor. A CFD code has been used for all predictions. Temperature gradients have been determined on axial and radial directions for better understanding combustion characteristics of biogases. Modelling has been studied for thermal power of 10 kW and excess air ratio of λ = 1.2 for each biogas combustion. The first finding is that combustion of biogases is possible via the newly generated burner. Moreover, the results show that the one of biogas is very close to methane in terms of temperature distributions in the combustor due to including high amount of methane compared to other biogases. It is also concluded that the flame temperatures of biogases increase with preheating the combustion air as expected. It is finally revealed that SO₂ emissions increase as amount of H₂S in biogas is increased through the combustor.     

直流二次风率对径向浓淡旋流煤粉燃烧器空气动力特性的影响

本文阐述了径向浓淡旋流煤粉燃烧器的基本原理，通过在一台４１０ｔ／ｈ的锅炉上的冷态，热态实验，研究了直流二次风率对燃烧器空气动力特性的影响，得到了直流二次风率与射流的扩展角，中心回流区直径及长度，一，二次风混合的关系，以及对燃烧器高效，稳燃，低污染，防结渣及防高温腐蚀性能的影响。