Burner Head Research Articles

Design and experimental investigation of an LPG injera baking stove for sustainable energy use in Ethiopia

About 40% of the world’s population use biomass as their primary energy source, especially for cooking but traditional and inefficient three-stone fires cause serious health issues and their high fuel consumption leads to deforestation problems. The objective of this study is to design and conduct an experimental investigation of injera baking stove using LPG to reduce exposure to household air pollution and environmental impact by providing clean, reliable and affordable stove to exposed populations. Here, in the present work, LPG injera baking stove is designed with circular ring burners with multiple flame ports to distribute heat to all parts of baking pan. The three concentric circular burner heads facilitate combustion and allow the distribution of heat through the plate. The burner is designed to ensure even heat distribution through all parts of the baking pan. The stove is manufactured from mild steel of 1.5 mm to withstand combustion temperature. Clay Injera baking pan of 450 mm diameter and 15 mm thickness is used in this study. Hence, reducing baking pan thickness from conventional size to 46 cm diameter and 15 mm thickness will result to reduce the heating time and hence enhance performance of stove. The result of experiment showed the designed injera baking stove has been tested and can bake injera of 440 mm diameter. The study showed the improvement in design of burner and selection of efficient baking pan enabled LPG application for Injera baking applications where electricity is not accessible. Thus, LPG technology can improve the lives of millions of people living in rural societies and meet efforts to combat climate change and meet sustainable development goal (SDG7).

An Experimental Study of the Emission Characteristics and Soot Emission of Fatty Acid Methyl Esters (FAME) in an Industrial Burner

The aim of this research is to investigate the environmental emission effects and combustion properties of burning different types of FAME biodiesel fuels in an industrial oil burner. These burner heads are used in many areas of industry for heating various boilers and tube furnaces. The fuels used, the area of use, the emission norm values, and the climatic conditions are key factors in this investigation. In this research, two plant-based oils are examined, the properties of which have been compared to standard commercial heating oil. The raw material of the two tested bio-based components was rapeseed. The main gas emission parameters CO, THC, CO2, O2, HC, water content, and consumption data were measured. The measurements were performed in an AVL engine brake platform infrastructure, where gas emissions were measured with an AVL AMA i60 FTIR emission gas analyzer, fuel consumption was meticulously gauged using a fuel flow meter, fuel temperature was monitored using an AVL 745 fuel temperature conditioning system, and air consumption was measured with an AVL Flowsonix intake air flow meter. The measurement results showed that both tested biofuels can be burned stably in industrial oil burners, have favorable properties in terms of ignition and flame extinction tendencies, and there is no significant difference in emission parameters compared to standard fuel oil.

Numerical Investigation of Flow and Flame Structures in an Industrial Swirling Inverse Diffusion Methane/Air Burner

In this study, a novel gas burner combining air swirl and an inverse diffusion flame (IDF) is designed for industrial applications. Numerical simulations using the Reynolds-averaged Navier–Stokes (RANS) method and simplified reaction mechanisms are conducted to predict the turbulent flow and combustion performance of the burner. Detailed flow structures, flame structures and effects of burner configurations are examined. The simulation results indicate that the swirl action of the burner creates a central recirculation zone and two external recirculation zones at the burner head, which stabilize combustion. The tangential velocity is minimal at the center of the burner and decreases with increasing distance from the outlet. As the distance from the exit increases, the maximum tangential velocity gradually decreases, and the peak value shifts towards the wall. This decrease in tangential velocity with axial distance signifies the gradual dissipation of the swirl effect, which disappears near the chamber outlet. The comparisons reveal that altering the number of burner fuel nozzles is more effective in reducing NO emissions than changing the inclination angle of the fuel nozzles, in the given conditions. Favorable combustion conditions are achieved when there are 16 fuel nozzles and the nozzle inclination angle is 60°, resulting in a 28.5% reduction in NO emissions at the outlet, compared to the reference condition.

Investigating the Mixture Quality in Multi-Injector Burner Systems, Part II: Model Application

Abstract Multi-injector burner systems offer a high spatial-temporal mixture homogeneity due to their small size and thus have a high NOx emission reduction potential at increasing flame temperatures. This potential is reduced due to the sensitivity of the mixing quality to inflow distortions caused by the flow path in the burner head. A deep understanding of the link between the inflow conditions and the mixture quality helps to optimize the flow field upstream of the injectors within the spatial and pressure loss constraints of gas turbine combustors to obtain minimal NOx emissions. This paper presents a new model approach for determining the mixture quality in multi-injector burners with output-based proper orthogonal decomposition (O-POD). The sensitivity to the inflow distortion is considered with the so-called observable vector, which describes the injector inflow conditions and is given as model input. The target quantity is the probability mass function (PMF) of the equivalence ratio at the injector outlet. This model allows a fast estimation of the mixing PMF for arbitrary inflow conditions, which is otherwise only accessible with complex time-resolved experimental or numerical approaches. The performance of the model was demonstrated with 21 reference datasets, for which a good agreement between the experimental results and the model output was obtained.

Experimental investigation of various burner heads in residential gas stoves tested with hydrogen and natural gas blends

The current study is designed to investigate the effect of five different burner head geometries of gas stoves. The amounts of heat required for boiling 380 grams of water in a pot for a stove for these several burner heads are measured. The flow rates are set to be 3 L/min and 6 L/min for experimental tests. These experimental results show that the burner head with three lateral sets of holes and two circular sets of holes at the top gives the minimum heating time when burning natural gas alone. Once the hydrogen-natural gas mixture is used, the burner head with one lateral and three top circular sets of holes shows the best performance among others regarding heating time. The effect of the flow rate increase is also investigated. Once the flow rate doubles, the burner head with three lateral sets of holes offers the best performance. Based on the findings of the experiments, it can be said that burner heads with lateral sets of holes operate better than other geometries. When natural gas is utilized as fuel, it is observed that the burner head with three lateral sets of holes and two circular sets of holes at the top provided a 12% reduction in heating time compared to the conventional burner head. For the natural gas and hydrogen blends, the conventional burner head achieves the best in terms of heating time.

Innovative Air Bypass System for Low-Emission Multi-Can Combustors

Abstract Gas turbines that are used as compressor drives are often operated in the part load regime because compressor stations are usually designed for operation with full power at extreme weather conditions. Consequently, these gas turbines must comply with strict emission regulations at unfavorably low turbine inlet temperatures. To extend the low-emission operation range of the premixed combustion systems, many gas turbines bypass a part of the compressed air upstream of the combustor and either blow it off into the exhaust stack or reinject it into the secondary combustion zone. This study presents a new approach that overcomes shortcomings by injecting the compressed air in the burner head in the vicinity of the primary combustion zone. This is particularly attractive for multi-can combustors. Atmospheric combustion tests are conducted for two different air injection designs. The first design features lower air injection velocity and the second features higher injection velocities. Both injection strategies are tested with the industrial MGT gas turbine can combustor. The full size burner is tested at atmospheric conditions in a burner test rig with a quartz flame tube and natural gas as fuel. The performance of the air bypass system is assessed by means of CO and NOx emission measurements for different air bypass ratios. Additionally, OH* chemiluminescence camera pictures are presented and compared to numerical calculations. It is found that the air injection in the annular vicinity of the swirl flame does not cause increased CO emissions by quenching or other effects.

Optimum swirl angle of natural gas combustion in domestic cooker burner with various output port

Due to the wide spread use of household cooker burner, optimal design of these equipment can significantly reduce the natural gas consumption which consequently leads to energy consumption reduction, emissions reduction, and economic benefits. Shape of cooker-top and swirl angle are the most important effective factors on performance of domestic cooker burner. This paper investigates the impact of swirling the output port on performance of the burner, numerically. In this regard, four types of burners are three-dimensionally modeled and compared to determine the optimal port swirl angle based on burner temperature, heat transfer rate and pollutant emissions. Results show that the optimum swirl angle for output port is 20º where the maximum combustion temperature and desired heat transfer and pollutant emissions are obtained. The maximum burner head temperature for non-swirled burner is equal to 1610 K while for swirl angle of 20º, in addition to pollutant emissions reduction, the maximum burner head temperature of 1673 K is obtained. It is also concluded that the turbulence dissipation of flow increases by swirling the cooker-top burner.

Energy efficiency improvement and emission reduction potential of domestic gas burners through re-orientating the angle and position of burner holes: Experimental and numerical study

The trend towards enhancing the thermal performance of domestic cooking burners necessitates developing a new design for such devices. With this picture in mind, this paper numerically and experimentally investigates the effect of burner head design configurations on the energy efficiency and CO emission of domestic gas burners. The results of a three-dimensional steady-state computational fluid dynamics (CFD) model is validated with the experimental data according to Volunteers in Technical Assistance (VITA) standard in cold start, hot start, and Simmer condition for two types of burners. Having the model validated, a step-by-step approach has been undertaken to improve the design of these reference cases, resulted in a total number of nine burner configurations analysed in this research. This is followed by determining the influence of introduced geometries on the thermal efficiency of burners. Based on the insights from the numerical model, the most efficient burner exhibits 3.3–22.2% higher thermal efficiency and 20.2–32.6% lower CO emission—depending on the gas flow rate—relative to the conventional burners. The optimised design can be implemented into existing burners with relatively little need for reconstruction. • Experimental and numerical study of natural gas combustion in domestic gas burners. • Experimental setup is designed to measure the thermal efficiency of typical burners. • A three-dimensional steady-state turbulent model is developed for numerical study. • Intense mixing induced by secondary effect improved the efficiency by 3.3–22.2%. • Optimum burner configuration lowered the carbon monoxide emission by 20.2–32.6%.

Effect of position of radial air injection plane on control of thermo-acoustic instability using active closed-loop method

Thermo-acoustic instability occurs when self-excited oscillations are generated due to the coupling between unsteady heat release and acoustics. This phenomenon can result in an increased rate of vibration, structural damage, and produces unwanted emissions. Thermo-acoustic instability occurs in rocket engines, gas turbines, combustors, and furnaces. When thermo-acoustic instability occurs, many modes are developed naturally at a specific point. Some waves are unstable and some are stable. So, to study this phenomenon the most unstable waves are considered and a technique is developed to suppress these unstable waves. A radial air injector as a closed-loop active control method is used for breaking the coupling between the heat waves and acoustics inside the 1D combustion chamber. The distance between the burner and the air injector is varied for the fixed position of the burner with respect to the Rijke tube, that is, x/L = 0.01125, 0.0075, and 0.00375. This closed-loop method works based on the feedback acquired from a microphone. The control method is built using DAQ and Arduino with the LabVIEW as interface for Arduino (LIFA). An air flow rate controller setup is developed to control and measure air required for suppressing the thermo-acoustic instability. Thermo-acoustic instability is effectively suppressed with the help of radial injection in the form of micro-jets at the downstream of the burner as the closed-loop controlling method. It is concluded that when the radial micro-jet air injection plane is closer to the burner head, the thermo-acoustic instability gets suppressed in a short time and with a lesser quantity of air.

NUMERICAL STUDY OF THE FACTORS THAT AFFECT THERMAL EFFICIENCY DURING INFRARED GAS STOVE HEATING

The Energy Policy and Planning Office, Ministry of Energy, Royal Thai Government reported from 2007 to 2015, the using of fuel increase every year. In addition, price of fuel increasescontinuously. The way of most efficiently of energy using is important. This paper aimed to study about thermal efficiency of infrared gas stove by varies with parameters which were diameters of pot (220, 240 and 260 mm), distances between burner (20, 25 and 30 mm) and pot and diameter of burner head (135, 145 and 155 mm) in 9 cases by simulation method. The numerical model was validated with results from experiment in 220, 240 and 260 mm of diameter of pot, average errors are 10.85011%, 6.754703% and 2.13054%, respectively. The results of this study showed with three sizes of pot, huger distances between burner and pot decrease thermal efficiency. The highest thermal efficiency was in 260 mm of diameter of pot. All of 9 cases by vary parameters, the highest thermal efficiency was 260 mm of diameter of pot, 20 mm of distance between burner and pot and 145 mm of diameter of burner head condition and the lowest thermal efficiency was 220 mm of diameter of pot, 20 mm of distance between burner and pot and 145 mm of diameter of burner head condition.The obtained results provide useful for development of heating process by infrared burner technologies and to guide the development of effective infrared burner too lead the way in energy-saving way and reduce environmental impacts.

Stability Characteristics of a Turbulent Nonpremixed Conical Bluff Body Flame

The thermal characteristics of turbulent non-premixed methane flames were investigated by four burner heads with the same exit diameter but different heights. The fuel flow rate was kept constant with an exit velocity of 15 m/s, while the co-flow air speed was increased from 0 to 7.6 m/s. The radial profiles of the temperature and flame visualizations were obtained to investigate the stability limits. The results evidenced that the air co-flow and the cone angle have essential roles in the stabilization of the flame: An increase in the cone angle and/or the co-flow speed deteriorated the stability of the flame, which eventually tended to blow off. As the cone angle was reduced, the flame was attached to the bluff body. However, when the cone angle is very small, it has no effect on stability. The mixing and entrainment processes were described by the statistical moments of the temperature fluctuations. It appears that the rise in temperature coincides with the intensified mixing, and it becomes constant in the entrainment region.

Experimental investigation and modeling of boundary layer flashback for non-swirling premixed hydrogen/ammonia/air flames

Carbon free fuels such as hydrogen/ammonia blends show a promising potential to become sustainable and renewable fuels for gas turbines and other combustion systems. One interesting aspect about these blends is the possibility to adjust different combustion properties like the laminar burning velocity or ignition delay time by changing the ratio between H2 and NH3. Such fuel blends can be produced via partial catalytic decomposition of NH3. However, such mixtures can lead to flame instabilities such as flashback, especially if the hydrogen content is high. In the present study, the boundary layer flashback of premixed hydrogen/ammonia/air mixtures is investigated experimentally for non-swirling flows at normal temperature (293 K) and normal pressure (101 kPa). A new experimental setup for boundary layer flashback investigation with a fully automated measurement procedure is introduced. With preliminary studies, the influence of various measurement procedures on the flashback limits is firstly investigated. For a broad flashback study, the data of 351 flashback experiments are collected. The ammonia content in H2/NH3 fuel mixtures is varied from 0 vol% to 50 vol% in 10 vol% steps. The fuel–air equivalence ratio is ranging from 0.38 to 1.17. As the ammonia content is increasing, the mean flow velocities at flashback are exponentially decreasing. Additionally, theoretical modeling is performed. A model is derived based on the concept of the critical velocity gradient which is able to predict the measured data with high accuracy. For two exemplary cases with H2/air and 80% H2/20% NH3/air mixtures, the process of boundary layer flashback is investigated in detail with low and high speed direct imaging and image post-processing. During the flashback onset of H2/NH3/air flames a separate reaction of H2 followed by the reaction of NH3 can be observed. Also, a flame-oscillation between fused silica tube and burner head with approximately 10 Hz was observed. Furthermore, indications for an adverse pressure gradient based on the flame propagation speed is seen. Details about the flame structure during the flashback process of H2/NH3/air flames are shown. During the upstream flame propagation of H2/NH3/air flames, high frequency oscillations with about 830 Hz of the leading flame tip are observed, which are assumed to be related to thermoacoustic instabilities.

An experimental study on the carbon conversion efficiency and emission indices of air and steam co-flow diffusion jet flames

Industrial flaring is a notable global contributor to carbon dioxide emissions and other key pollutants. Introducing a separate assisting fluid near the base of these flames affects their hydrodynamics, thermodynamics, and chemistry, which in turn affects their efficiency and emissions. In this study, a burner constructed of two concentric tubes allowed for various generic burner geometries, where different fuels (methane or propane) and co-flow assisting fluids (air, steam, or inert gases) flowed through the annular space and the center tube, respectively. The effects of the composition and flow rate of the fuel and assisting fluid, as well as the burner head geometry, were investigated in terms of carbon conversion efficiency (CCE) and emission indices of black carbon and oxides of nitrogen. The CCE was observed to be essentially 100% for unassisted flames and remained at that level when assisting fluid, irrespective of composition, was added. However, at some critical flow rate of assisting fluid, the CCE collapsed, and the main flame blew off. In general, the CCE collapse occurred at considerably more mass of air compared to that of steam. Furthermore, adding the assisting fluid co-flow monotonically reduced the black carbon emission by orders of magnitude. On the other hand, the emission of oxides of nitrogen rose slightly with increasing air co-flow flow rate and dropped when steam or other diluents were added. These results showed that there was a range of assisting fluid flow rates, where the CCE was approximately 100%, while the emission of black carbon and nitrogen oxides were highly suppressed.

Experimental and Numerical Study of the Effect of Fuel/Air Mixing Modes on NOx and CO Emissions of MILD Combustion in a Boiler Burner

The Moderate or Intense Low-oxygen Dilution (MILD) combustion is characterized by low emissions, stable combustion and low noise for various kinds of fuel, which has great potential in the industry. The aim of this study is to investigate the effect of fuel/air mixing modes on NOx and CO emissions of MILD combustion in a boiler burner by experiments and numerical simulations. Three types of fuel/air mixing modes (premixing mode, diffusion mode and hybrid mode) have been considered in this study. The realizable k-e turbulent model and the Eddy Dissipation Concept (EDC) combustion model were used in numerical simulations. In addition to the temperature near the burner head, the calculation results match very well with the axial temperature distribution at the furnace center. The flow pattern under different mixing modes is similar, while the hybrid mode has a higher OH concentration near the diffusive fuel nozzle than the premixing mode, and the corresponding position of the peak OH concentration is closer to the rear half of the furnace. The distribution of temperature is extremely uniform for the premixing mode in the main reactive zone, which is typical for MILD combustion. There is a distinct area where the reaction temperature is higher than 1600 K for the hybrid mode. Moreover, in the main reactive zone, the gas recirculation ratio is high enough to ensure flue gas recirculation, which is beneficial to achieve MILD combustion at local areas. At the location where the axial distance is greater than 0.2 m, the gas recirculation ratio of the premixing mode is larger than that of the hybrid mode, which strengthens the entrainment of hot flue gas into the recirculated gas. The experimental results show that when the thermal intensity is less than 1.67 MWm−3, the NOx emissions are less than 15×10−6@3.5%O2 in near stoichiometric ratio in the premixing mode, and the CO emissions are less than 10×10−6@3.5%O2 under the same conditions. In the diffusion mode, the NOx emissions are less than 30×10−6@3.5%O2. In order to keep NOx and CO emissions low, the hybrid modes with optimized fuel distribution ratio are found under different thermal intensities.

Study on the Effects of Cone Height on the Turbulent Nonpremixed Flames Downstream of a Conical Bluff Body

Abstract Flow, thermal, and emission characteristics of turbulent nonpremixed CH4 flames were investigated for three burner heads of different cone heights. The fuel velocity was kept constant at 15 m/s, while the coflow air speed was varied between 0 and 7.4 m/s. Detailed radial profiles of the velocity and temperature were obtained in the bluff body wake at three vertical locations of 0.5D, 1D, and 1.5D. Emissions of CO2, CO, NOx, and O2 were also measured at the tail end of every flame. Flames were digitally photographed to support the point measurements with the visual observations. Fifteen different stability points were examined, which were the results of three bluff body variants and five coflow velocities. The results show that a blue-colored ring flame is formed, especially at high coflow velocities. The results also illustrate that depending on the mixing at the bluff-body wake, the flames exhibit two modes of combustion regimes, namely fuel jet- and coflow-dominated flames. In the jet-dominated regime, the flames become longer when compared with the flames of the coflow-dominated regime. In the latter regime, emissions were largely reduced due to the dilution by the excess air, which also surpasses their production.

Evaluation of emission indices and air quality implications of liquefied petroleum gas burners

Major cities in Nigeria has adopted the use of liquefied petroleum gas (LPG) as their main source for domestic cooking, however, this adoption led to different designs of LPG burners in Nigeria market. The emission indices of these burners and their air quality implications are yet to be ascertain. To solve these problems and fill the data gap, laboratory analysis were carried out on 16 conventional LPG burner heads identified in Nigeria market. The emission factors for Carbon monoxide (CO), Oxide of Nitrogen (NOx), Carbon dioxide (CO2), Hydrocarbons (HC) and sulphur dioxide (SO2) on the basis of useful energy delivered were 0.123–21.784 g/MJd, 1.973–32.943 g/MJd, 73.819–147.639 g/MJd, 4.069–171.643 g/MJd and 0–0.1644 g/MJd while the emission rates were 0.000238–0.1125 g/s, 0.0071–0.2 g/s, 0.1083–0.7 g/s, 0.0117–1.2583 g/s and 0–0.000194 g/s respectively. It was observed that results from the study were within the International Organization for Standardization, International Workshop Agreement 11 and World Health Organization indoor air quality guidelines for human protection.

Study on corrosion cracking and oxidation mechanism of Inconel 718 burner of gasifier pulverized coal

The cracking mechanism of pulverized coal burner head of Inconel 718 gasifier was analyzed by means of macro-morphology examination, metallographic examination, scanning electron microscopy observation (SEM) and EDS analysis. The results show that the micro-cracks in the central hole of the burner intensify under the action of thermal stress, resulting in macro-cracks at the central hole of the burner head and oxidation corrosion layer on the surface during the repeated start-up and shut-down of the gasifier. Thermal fatigue and oxidation are the main causes of central cracking and surface oxidation of burner. Distribution and migration of elements such as Nb, Cr and Al during oxidation were studied.

Determination of Trace Amounts of Gold in Electroplating Rinsing Bath by Slotted Quartz Tube Flame Atomic Absorption Spectrometry with Matrix Matching Calibration Strategy after Preconcentration with Vortex Assisted Dispersive Liquid–Liquid Microextraction

With the aim of mitigating the low sensitivity of the conventional flame atomic absorption spectrometer (FAAS) for gold determination, a dispersive liquid–liquid microextraction (DLLME) method was used to preconcentrate gold from the sample solution and a slotted quartz tube (SQT) was attached to the FAAS burner head to boost the residence time of the atoms in the flame. Three main optimization studies were performed to enhance the absorbance signal of gold by the FAAS system. The SQT-FAAS system was optimized based on the fuel and sample flow rates and the position of SQT on the burner head. Parameters including the pH and volume of buffer solution, volume of ligand solution, and mixing period were optimized for the efficient complexation of gold with diethyldithiocarbamate. The DLLME method was optimized based on the type and volume of dispersive and extraction solvents, type of ionic salt and mass of ionic salt. With the optimized values obtained, 1.7 and 5.6 µg/L were determined to be the method limit of detection (LOD) and limit of quantification (LOQ), respectively. The method applicability and accuracy in quantifying gold in a real sample matrix were determined by the use of spike recovery tests of electroplating rinse bath solution. Close to 100% recovery results were obtained using a matrix matching calibration method.

Heat recovery and metal oxide particles trapping in a power generation system using a swirl-stabilized metal-air burner

In order to tackle future challenges concerning zero greenhouse gases emissions, an innovative power generation system was designed and analyzed. It included a swirled-stabilized metal-air burner confined in a water-cooled combustion chamber, a secondary heat exchanger and a particle filtration system leading to a unique system of this kind. Magnesium particles in the range 50–70 µm were used as metal fuel. The effect of the swirl intensity was evaluated first on the flame position within the combustion chamber. As expected, the flame was stabilized closer to the burner head with the high swirl number than with the low one. To reach optimal heat to-mechanical conversion efficiency, an analysis of the heat recovery in the power generation system was performed. Experiments were conducted with a total chemical power ranging from 6 kW to 11 kW. Eighty percent of the power released by combustion were recovered in the power generation system and 50% in the combustion chamber. Ninety-eight percent of the magnesium oxide produced by combustion were trapped inside the system. Laser granulometry showed a number distribution for the metal oxide particles around 500 nm. Untrapped particles were measured by a Pegasor Particle Sensor (PPS), which was previously calibrated by comparison with measurements of the total suspended particles (TSP). Complementary TEM analysis confirmed that the metal oxide particles were aggregates of elementary submicron MgO cubic particles (10–1000 nm).

Lifting and yellow tip characteristics of small-scale partially premixed combustor burning pipeline natural gas and liquefied natural gas

In this article, a small-scale partially premixed combustor was designed with 1.5 kW heat input rate. Through altering premixing ratio of gas and air, the lifting and yellow tip characteristics were experimentally tested with the burner head material of cast-iron and copper–aluminum respectively. Combined with burner head temperature influences, the lifting and yellow tip characteristics of small-scale partially premixed combustor are discussed when natural gas is substituted. It is found that when lifting and yellow tip occur, the cast-iron burner shows a slow tendency of temperature change, but the temperature of copper–aluminum burner fluctuates sharply. Yellow tip is related to gas properties and burner structure, and is more likely to appear with the increase of the Wobbe index and heavy hydrocarbon fraction, while lifting is very likely to appear when temperature fluctuates. Yellow tip characteristic can be predicted by Wobbe index, but this method is unsuitable for lifting prediction.