Burner Tip Research Articles

Study of polycyclic aromatic hydrocarbons (PAHs) in hydrogen-enriched methane diffusion flames

Polycyclic aromatic hydrocarbons (PAHs) are the carcinogenic components of soot. Detailed understanding of PAH formation characteristics is required for development of effective strategies to curtail PAH formation and reduce soot in combustion devices. This study presents an experimental methodology to analyse PAH formation characteristics of a non-premixed methane-air flame with and without hydrogen (H2) addition, using simultaneous planar laser induced fluorescence (PLIF) imaging of PAH and hydroxyl radical (OH). OH PLIF was used to represent peak temperature regions in the flame front. One-dimensional, opposed-jet laminar non-premixed flame simulations were also carried out for the same fuel mixture conditions. This work describes comparison of trends from both sets of studies. PAH fluorescence intensity values were observed to increase with increasing height above burner, however this rate of increase reduced with H2 addition. This observed rate of change in PAH fluorescence (that is, PAH growth characteristics) is indicative of the sooting potential of the fuel mixture. PAH fluorescence from experiments and PAH concentration from simulation show strong reduction with increase in H2 addition. The percentage reduction in PAH fluorescence signal with H2 addition closer to the burner tip was of a similar magnitude to that observed with flame simulations. The reduction in PAH with H2 addition could be attributed to the reduction in acetylene and propargyl concentrations, and reduced H-abstraction rates, which reduced the availability of active sites for PAH growth. The proposed experimental methodology for PAH measurements can be readily applied to any fuel mixtures.

Failure analysis of gas turbine burner tips

In this study, the causes of failure in gas turbine burner tips were investigated. For this purpose, two burner tips used in a petrochemical company with different failure evidence as well as service times were inspected. These parts showed signs of deterioration such as multiple cracks, corrosion, and wear following 4000 h and 8000 h operations. The examinations included chemical composition analysis using optical emission spectroscopy (OES), stereo-, optical-, and scanning electron microscopy studies, and macro/micro-hardness measurements. These investigations revealed high thermal stresses to be the main failure cause of the burner tips. Moreover, due to flame inclination, a local increase in the temperature in some parts occurred. So, hot oxidation was a further reason for the fracture of these burner tips. Last but not least, improper jointing processes facilitated the failure in the studied components.

Design evaluation of diesel-oxygen diffusion flame burner for start-up of high-pressure coal gasifier

Commercial entrained-flow coal gasifiers operate at high temperatures and pressures for increased efficiency. For reduced operation costs, the start-up burner (SUB) of a gasifier requires fast heating and pressurization by intensive combustion, minimizing damage to the refractory lining and to itself. We evaluated different designs of the SUB adopting diesel-oxygen diffusion flame under the stoichiometric condition to improve the performance of the existing premixed flame burner that has been subjected to frequent failures. Using computational fluid dynamics, the combustion characteristics of the SUB with a thermal input up to 2.28MWth and pressure up to 8 bar were predicted for tests in a pilot-scale cylindrical gasifier. The results showed that the injection of diesel and oxygen through separate multiple inlets can intensify the combustion, leading to short and stable turbulent diffusion flames. Varying the design of the burner tip and inlet arrangement reduced the influence of pressure on the flame length while achieving high heat flux to the wall, which is essential for a fast and stable start-up. Further investigations are required to understand the influence of the reactor geometry on the circulation flow of high-temperature gas back to the burner tip in the actual gasifier.

Temperature field investigation of hydrogen/air and syngas/air axisymmetric laminar flames using Mach-Zehnder interferometry.

In this study, the optical method of Mach-Zehnder interferometry (MZI) is utilized in order to explore the flame structure and temperature field of syngas/air and hydrogen/air flames. Two axisymmetric burners with inner diameters of 4mm and 6mm are used for temperature field measurement of hydrogen and syngas, respectively. The effects of fuel composition, equivalence ratio, and Reynolds number (Re) are investigated at ambient condition (P=0.87 bar, T=300 K). Three different H2/CO fuel compositions with hydrogen fractions of 30%, 50%, and 100% are studied. Temperature profiles are reported at four different sections above the burner tip. Measured temperatures using the interferometry method are compared with thermocouple data and good agreement between them is observed. The results obtained in this investigation indicated that the MZI can be applied for accurate determination of flame front and temperature field, especially for high-temperature flames where other methods cannot be properly utilized. Analyses of the data reduction method revealed that the exact determination of the refractive index distribution and reference temperature is critical for accurate determination of the temperature field. The results indicated that by increasing the Re, the maximum flame temperature is enhanced. Increasing the equivalence ratio leads to expansion of the flame radial distribution (at the same distance from the burner tip). At higher distances from the burner tip, temperature increases uniformly from the flame boundary toward the flame axis, while at lower heights it shows reduction at the burner axis. By increasing the CO content of fuel, the maximum flame temperature increases at all equivalence ratios except at the stoichiometric condition, where SH100 illustrates the highest maximum flame temperature.

Assessment of porous media combustion with foam porous media for surface/submerged flame

One of the popular ways to improve thermal efficiency of porous media burners is by enabling smart materials in reaction zone. In this experimental work, a predefined bilayer porous media micro burner was made to achieve both surface and submerged flame for a foam type (Alumina) of reaction layer and compared with conventional style of using discrete type. Moreover, preheat layer was also made up of foam (porcelain), which helped in attaining stable flame. This work mainly aimed to show burner behavior from rich to lean region at critical equivalence ratios. During surface mode combustion highest temperature was recorded for foam type was at equivalence ratio of 1.1, while discrete type was 1.3. Similarly, submerged mode combustion reordered maximum temperature for both foam and discrete type was around 0.6. Finally, thermal efficiencies where calculated at suitable equivalence ratios and emitted emission from the burner tip was also taken into considerations.

Electric Field Damping of Rijke Tube Combustion Instabilities

A direct-current electric field was investigated as a damping method for thermoacoustic instabilities generated in a horizontal Rijke tube driven by a premixed propane torch. Electrode lengths of 2.54, 5.08, and 15.24 cm were used with electrode locations relative to the burner tip of , , and 0.458 cm and voltages up to 4.68 kV being tested. Electrodes downstream of the burner tip, rather than surrounding the burner, and longer electrodes were most effective at damping instabilities. Damping also increased with applied voltage. These findings held true for both laminar and turbulent flames and were in agreement with theoretical predictions made based on two-dimensional static electric field models. Sound pressure level reductions up to 21 dB for the laminar flame, which completely damped the instability, and 4.4 dB for the turbulent flame were seen using the 15.24 cm electrode at 4.68 kV. When the entire Rijke tube acted as the electrode, a reduction of 19 dB was seen for the turbulent flame at 9 kV, which suppressed the instability. The damping effect was attributed to stabilization of the oscillating flame and its unsteady heat release, driven by the combustion instability pressure fluctuations, via the ionic wind.

Flame base structures of micro-jet hydrogen/methane diffusion flames

In this study, a comparison of flame base structures of hydrogen/methane–air diffusion flames formed over a tiny-jet is made numerically for both isothermal and thermal conductive burner conditions, in order to clarify the fuel dependent flame stabilization mechanisms. It is found that, unlike a methane flame, the flame base of a hydrogen flame always attaches to the burner. The analyses indicate that the dominant intermediate-consumption steps have significantly lower activation energies for the hydrogen flame as compared to a methane flame. More importantly, one of the HO2 production reactions (R43f: H+O2+M→HO2+M), which has a dominant role in sustaining reactivity at the flame base, shows a negative temperature dependence, causing the heat release rate in the flame base kernel to increase as the burner wall temperature decreases. With a thermal conductive burner (thermal conductivity of 16W/m-K) over a wide range of fuel jet velocities (0.5–4.0m/s), it is found that the burner tip is heated to a significantly higher temperature by a hydrogen flame due to its unique stabilization mechanism. The mixing effects of hydrogen and methane are then considered. It is found that the burner tip temperature can be reduced by adding methane into the fuel flow. This is because, according to the investigation of the structures of the hydrogen/methane jet diffusion flames, the reaction rate of R43f is suppressed due to the included intermediates (e.g., CH3, CH2O) consumption steps of methane. It is expected that the flame attachment feature associated with the flame base structure can be easily controlled by mixing hydrogen and methane, making it possible to control the burner tip temperature in advance.

Developing Additive Manufacturing Technology for Burner Repair

Low emission combustion is one of the most important requirements for industrial gas turbines. Siemens industrial gas turbines SGT-800 and SGT-700 use dry low emission (DLE) technology and are equipped with third generation of DLE burners. These burners demonstrate high-performance and reliable operation for the duration of their design lifetime. The design and shape of the burner tip is of great importance in order to achieve a good fuel/ air mixture and at the same time a resistance to the fatigue created by heat radiation input. This gives a requirement for a tip structure with delicate internal channels combined with thicker structure for load carrying and production reasons. It was found that the extension of the burner lifetime beyond the original design life could be accomplished by means of repair of the burner tip. Initially, the tip repair has been done by conventional methods— i.e., cutting off the tip and replacing it with a premanufactured one. Due to the sophisticated internal structure of the burner, the cuts have to be made fairly high upstream to avoid having the weld in the delicate channel area. Through the use of additive manufacturing (AM) technology, it has been possible to simplify the repair and only replace the damaged part of the tip. Special processes have been developed for AM repair procedure, including the following: machining off of the damaged and oxidized tip, positioning the sintered model on the burner face, sintering a new tip in place, quality assurance and inspection methods, powder handling, material qualification including bonding zone, development of methods for mechanical integrity calculation, and qualification of the whole repair process. This paper describes how we have developed and qualified SGT-800 and SGT-700 DLE burners repair with the help of additive manufacturing technology and our research work performed. In addition, this paper highlights the challenges we faced during design, materials qualification, and repair work shop set up.

The Role of Expansion and Fragmentation Phenomena on the Generation and Chemical Composition of Dust Particles in a Flash Converting Reactor

A compositional fragmentation model was used to clarify the effect of expansion and fragmentation phenomena on the generation and chemical composition of dust particles in a flash converting reactor. A fragmentation index is introduced to represent the fraction of particles undergoing fragmentation, as opposed to expansion, within the particle population. Under typical operating conditions, the local dust content and the net amount of dust generated compared with the dust content in the feed first decreased and then increased along the reactor length, whereas the amount of particles undergoing fragmentation (fragmentation index) increased steadily. Dust generation was found to be the result of two competing phenomena, i.e., the expansion of dust particles in the feed and the production of dust from fragmentation of large particles. At short distance from the burner tip, the dust mostly consists of particles in the feed undergoing oxidation and expansion, whereas farther down the reactor it mostly consists of fragments of partially reacted particles. Based on the computer simulations under a variety of experimental conditions, a map of dust generation against fragmentation index was developed. For most practical purposes, dust generation may be approximated by the change in the mass fraction of dust in the population. At the reactor exit, the composition of the dust is approximately the same as the entire particle population.

Impinging nonpremixed coflow methane–air flames with unity Lewis number

The present work extends earlier theoretical models in order to analyze nonpremixed flames stabilized between an axisymmetric coflow burner and a downstream plate that produces a stagnating flow field. This unusual configuration (i.e., it is not a coflow nor a counterflow flame but an impinging nonpremixed flame) is analyzed with two approaches previously developed as extensions to the Burke–Schumann theory: the Extended Roper Model and the Stream Function as a Coordinate Model. The flow field is obtained through the solution of a stagnation point viscous flow for incompressible fluids between stationary porous plates. In order to simplify the analysis, unity Lewis number is considered. Infinitely fast conversion of the reactants into products is assumed together with the Shvab–Zel’dovich coupling function approach, which allows the solution of a reduced number of conservation equations free of source terms. The influence of the distance between the impinging plate and the burner tip on a methane–air flame is analyzed and the semi-analytical results are compared with experimental data for several vertical positions of the stagnation plate with respect to the burner port. The model is able to effectively capture general aspects of the flame such as its shape, standoff distance, and separation distance at which flame tip opening is observed.

Effect of self-entrainment and porous geometry on stability of premixed LPG porous burner

This paper presents findings on combustion stability of a self-entrained, rich-premixed LPG porous burner. Alumina (Al2O3) porous foams, with 15ppi carved into bulked and hollowed cylindrical shapes were placed at a convertible burner tip, while the conventional porous-free burner was used as a base case for comparison. Visual flame propagation, temperature and the percentage of oxygen in a premixed zone were monitored at different firing rates. Initially, the tests were carried out based on basic geometry of bulky porous cylindrical foam under a free flame mode. At this part, the limitation of burner operation was realized in term of premixed equivalence ratio which was a result from self-entrainment. Later, an improvement was made on porous geometry and its effect on burner performance was considered with the previous version. It was found that propagation of flame within a porous matrix had significant contribution to temperature of the premixed zone as a result of radiation. Discussion was made relating to two competing factors controlling flame propagation within the porous burner i.e.; local flame speed and local convective effect. Combustion stability was found with domination of flame speed over convection when Φ<4.1 in the premixed zone corresponding to illumination of the porous medium with the temperature of premixed zone being greater than 200°C. Beyond 980kW/m2 (equivalent to 4L/min of LPG) where convection effect dominated, heat recirculation within porous domain was broken down resulting in formation of soot burning outside porous medium corresponding to considerably drop of temperature. At this range, such short characteristic resident time, lower than 2s, was observed with Φ>4.1 in premixed zone. The hollowed cylinder, however, yielded stable flame throughout the operation range at the central port while propagation was maintained in a porous matrix which acted as a flame holder even at high firing rate. The temperature of premixed zone was also observed higher compared with bulked porous burner while the central port could eliminate flow blockage which otherwise gave significant adverse effect on primary air entrainment.

Air jet impingement technique for thermal characterisation of premixed methane–air impinging flame jets

A major part of the domestic and the industrial thermal energy requirement for the heating purpose is achieved by the combustion of hydrocarbon fuels using burners. The present study reveals that thermal characterisation of impinging flame jets can be performed with a steady state technique similar to thin metal foil technique used for impinging air jets. The target surface impinged by the premixed methane–air flame jet is simultaneously cooled from the rear side by impinging air jets at different Reynolds number. One dimensional energy balance across the thickness of the plate is performed. The Nusselt number and the effectiveness distributions for a tube burner with the present technique matched reasonably well with the two-equation technique proposed in our previous work. Maximum deviations of 12% and 15% are observed for Nu and η respectively. Correlations are developed for the local Nusselt number and effectiveness in terms of flame jet parameters. The burner is analysed for the thermal efficiency. For premixed cone flames, it is observed that the thermal efficiency increases with the Reynolds number and equivalence ratio and decreases with the burner tip to plate spacing.

Design of LPG burner for hot air puffing machine

In puffing machines the hot air is produced either by burning liquefied petroleum gas (LPG) or electric heaters to develop puffed ready-to-eat (RTE) product. In puffing machine the product is puffed in LPG flue gas mixed hot air based on the whirling bed principle. Therefore, to produce hot air by burning LPG, three non-premixed diffusion type burner configurations were designed to produce a stable blue flame with minimum soot length. In Type I burner of 20 cm length two concentric galvanized iron pipes-inner gas pipe of 2.7 cm (OD) and outer air pipe of 5 cm (OD) were used. The gas was introduced in the inner pipe of burner through copper pipe of 1.3 cm (OD) from outside. It works and produces the flame with an obstruction plate of diameter equal to inner burner pipe which was positioned in front of inner pipe for stability of flame. In experimental tests it was observed that flame do not catches when blower was started and forms a single jet unstable luminous (soot) flame at high air velocity. In Type II burner two steam pipes of diameter 4.7 and 2.7 cm (OD) were used for fabrication. In order to protect the flame from high velocity air, a truncated conical metal (cast iron) shield of 4.7 cm diameter was welded to the rim of air pipe. The Type II burner produced characteristic long blue flame and less soot length but there was soot formation in flame at relatively low air flow rates. To overcome the problem of flame instability and soot formation a third burner configuration was used. Three concentric steam pipes were used for Type III burner. It was observed that the secondary air from central pipe results in proper combustion, complete blue flame formation at the burner tip and better flame stability under variable air flow rates. In Type II and Type III burner, the flue gases of temperature ranging from 90 o – 300 o can be produced at gas flow rates from 7 – 22 lpm.

Heat transfer distribution of swirling flame jet impinging on a flat plate using twisted tapes

Impinging flame jets have wide applications in industrial and domestic heating purpose. The aim of the present study is to study the effect of swirl on flame jet impingement heat transfer characteristics. Four twisted tapes of twist ratios 2, 3.2, 4.5 and 7.5 (corresponding swirl numbers of 0.79, 0.49, 0.35 and 0.21) are used to experimentally obtain the swirling flame jet. The effect of twist ratio at Reynolds number varying from 500 to 2500 and equivalence ratio varying from 0.7 to 1.5 for burner tip to impingement plate distances of 2 and 4 is studied. The effect of swirl is compared with that of no tape in the tube burner by estimating the average heat flux distribution and coefficient of variation of heat flux for two impingement regions – within two times the burner diameter from the stagnation point and four times diameter from the stagnation point. From the experimental study, it is found that swirl enhances the heat flux distribution by 40–140% at low Reynolds number. At higher Reynolds number the effect of swirl is negative and is found to decrease the average heat flux distribution by 10–40%.

Heat transfer distribution for three interacting methane–air premixed impinging flame jets

Multiple impinging flame jets are widely used in industrial heating (Ex. ladle preheating) and melting applications (Ex. glass forming). In the present method, high resolution heat flux distribution is obtained by applying the inverse heat conduction technique using thermal infrared camera. The high resolution thermal imaging enables to capture the steep gradients of spatial heat flux distribution. Nusselt number and effectiveness distributions are obtained by analytical–numerical method of estimation of the adiabatic wall temperature. Three circular tube burners arranged in a staggered pattern with inter tube spacing (S/d) of 2 to 6 is considered. The ratio of distance from tube burner tip to the impingement plate (z/d) is varied from 2 to 6 while the Reynolds number is varied from 400 to 1000. For the smallest S/d=2, the interaction amongst the flames is significant and leads to non-circular hot spot distribution for heat flux. The average Nusselt number and average effectiveness are higher for higher Re for all z/d unless the inner premixed cone touches the impingement plate. The average Nusselt number and average effectiveness are marginally higher for smaller S/d for the same z/d and Re. The coefficient of variance increases with the increase in S/d.

Pembakaran Premixed Minyak Nabati pada Bunsen Burner Type Silinder

In the premixed combustion wave propagation combustion occurs is called the flame front. Premixed flame will propagate at the speed of moving towards the reactants unique. If the speed of the reactants is equal to the speed of propagation of fire, the fire (reaction zone) will be stationary. It is necessary to follow up on the influence of equivalence ratio (φ) varied with laminar flame speed (SL) in the premixed combustion of vegetable oil (virgin coconut oil, jatropha and cotton seeds). Research using experimental (true experimental research), which is put through direct observation by the equivalence ratio (φ), 1.5, 1.6, 1.7 and 1.8 m / l, to determine the causal relationship. Then the results showed a pattern of fire Bunsen burner pure coconut oil with equivalence ratio (φ), namely: 2.00, 1.87, 1.78, and 1.66, jatropha oil with equivalence ratio (φ) are: 1.73, 1.62, 1:52, and 1:44 and seed oil kapok with equivalence ratio (φ) are: 1.76, 1.65, 1:55, and 1:46, the richer the air the flame pattern that looks smaller and smaller until the blow off. This happens because the richer the air causes the fuel has an air excess so that the fuel (fuel) burning diffusion semakain reduced and cause combustion close to the surface of the tip of the nozzle Bunsen burner to high flame formed shorter until there blow off or extinguished.

Effect of preheated mixture on heat transfer characteristics of impinging methane–air premixed flame jet

Energy from spent flame or other low grade energy can be used to increase the temperature of the air before mixing with fuel. This would improve the heat transfer characteristics of the impinging flame jet. The studies on impinging flame jets reported in the literature are based on the fuel–air mixture at ambient temperature. In the present work, the inlet air for mixture is heated by an electrical heater. The heat flux distribution is estimated using an inverse heat conduction (IHCP) technique. The Nusselt number (Nu) and effectiveness (η) distributions are obtained by estimating the adiabatic wall temperature (Taw) by the analytical–numerical method. A circular burner of 13.5mm is used for impingement on quartz plate of 3mm thickness. Reynolds number (Re) varying from 500 to 2000 for the non-dimensional burner tip to impingement plate spacing (Z/d) of 2–6 and stoichiometric condition (ϕ=1.0) is considered for varying preheated condition. The effect of equivalence ratio is studied for ϕ=0.75 to 1.5 for Re=1000 and Z/d=4. By increase in preheat temperature, the stagnation point heat flux increases from 20% to 50% unless the inner premixed zone touches the impingement plate. CFD simulations are carried out in FLUENT software to explain the distribution of heat flux.

FAILURE OF GAS TURBINE CONE BURNER BY CARBURIZATION

Gas turbine for a power plant has 72 pieces of cone burner in its combustion chamber. High-speed diesel oil (HSD) is use as fuel to produce 130 MW of power at 3,000 rpm. The maximum temperature at the turbine inlet is estimated about 1087oC and at the outlet is between 400-540oC. Sixty percent of the cone burner failed repetitively at one side of the tip-end after 6,000 hours of service. The refurbished cone burner has to be replaced by a new one after 18,000 of service-hours. The cone burner material is cast Hastelloy-X (nickel based alloys). Metallurgical analyses by microstructural observation using optical and scanning electron microscopes, and energy dispersive spectroscope have been performed to observe the change in burner microstructure. Thermodynamics analysis has been performed to obtain temperature distribution around the failed section. Two failed cone burners have been examined; cone burner that has not been repaired, and that has been repaired twice. Thermodynamics analysis result shown that the temperature around the failed section is between 897 to 1087oC. Microstructure of the good part, far from the failed section, consists of cast structure of austenite matrix and fine carbide particles. Severe carbide precipitation and growth was observed on the failed section even the nominal carbon content in material is only 0.10% (max.). Severe carbide precipitation occurred because of carbon ingress from the environment (carburization) which combines with carbide forming elements in material (chromium, molybdenum, and tungsten). As a result, the corrosion and oxidation resistance of material decreased significantly after long time exposure at high temperature that led to oxidation, thinning, and failure of the cone burner tip. Failure only localized on one side of the tip-edge, therefore refurbishment by welding and coating can be performed to extend the life cycle of cone burner. The current examination results shows that the replacement cycle is not only limited to 18,000 hours but can also be extended to 48,000 hours.

Thermal and chemical structures formed in the micro burner of miniaturized hydrogen-air jet flames

The thermal and chemical structure formed in the micro burner potentially leading to the unique stability mechanism of miniaturized jet diffusion flame via excess heat recirculation through the burner wall, is studied numerically. 2-D axis-symmetric heat and mass transport processes with chemical reactions are considered in gas phase, while the heat transport process is considered in solid phase. The burner materials and fuel ejecting velocities are considered as the main numerical parameters in order to examine the role of the burner on the thermal and chemical structure inside the burner. A skeletal reaction mechanism consists of twelve steps chemical reactions and nine species is applied to consider the radical generation/consumption, and their transport in the burner. It is found that the tiny flame is stabilized even with extra-ordinary small Reynolds number, at which an extinction is generally experienced, when the low conductivity burner is adopted. This is due to the effective usage of the transferred heat from the flame to the burner to improve the stability owing to (1) preheating the incoming fuel, (2) the least heat loss from the flame toward the burner tip, and (3) enhancing the reactivity inside the burner. In such low Reynolds number jet flow with the low conductive burner, ambient air can easily diffuse back into the burner and oxidative reactions at the vicinity of the burner tip is then promoted. Accordingly, the flame structure along the axis is dramatically modified beyond the typical 1-D flame. It is suggested that the further chemical process could be promoted in the substantially-heated micro burner by considering the catalytic reaction at the inner burner surface or using oxygenated fuel likely alcohol or ether.

A novel concept to estimate the steady state heat flux from impinging premixed flame jets in an enclosure by numerical IHCP technique

Most of the flame jet impingement in industrial and domestic applications is carried out in an enclosure. However, no data is available in the literature for impinging flame jets in an enclosure. The present experimental study proposes a novel concept for obtaining the heat flux distribution using numerical IHCP technique. The heat flux evaluated by the present method has high spatial resolution, requires short time and is found to be reasonably accurate. The heat transfer distribution of a single flame jet from tube burner of 7.5 mm diameter is studied at Reynolds number varying from 500 to 900 with and without enclosure. The heat transfer distribution of three circular tube burners of diameter 7.5 mm is studied at Reynolds number varying from 500 to 900 with and without enclosure. The ratio of distance from the burner tip to the impingement plate to the burner diameter is varied from 1.9 to 5.1. A comparison of average heat flux distribution of three tube burner pair (7.5 mm diameter) with two tube burner pair (11.25 mm diameter) is carried out for similar conditions. The presence of enclosure has negligible effect on the heat transfer distribution from flame jets for both single and multiple jets. It is found that two tube burner pair has higher (8% to 18%) average heat flux distribution and more uniformity as compared to three tube burner pair.