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In this study, a kerosene-fueled premixed burner system with a thick and large pore-sized (“coarse”) porous matrix was developed to achieve less-soot stable premixed combustion with variable combustion loads, i.e., turn-down ratio, TDR, defined as the ratio between the maximum and minimum loads. The present burner system mainly consists of the thick and coarse porous matrix made by packed ceramic balls of 8 mm-diameter, which acts as a vaporizer, mixer, and flame holder. The liquid fuel is fed into the porous matrix along with air. As the air and vaporized fuel are supplied toward the top-end (surface) of the porous matrix, a premixed flame is formed at this surface. Benefits of the adopted porous matrix include reduced wettability of the liquid fuel to pores of the porous matrix, which prevents its direct supply to the flame, promotes vaporization and mixing, and functions as a flame holder, allowing the flame to be sustained within the porous matrix. Combustion experiments were then carried out under various equivalence ratios (φ) between 0.47 and 1.34, and temperature measurement was conducted to evaluate the vaporization capability within the porous matrix. The experimental results confirmed that the quasi-steady and stable premixed combustion across the entire surface of the porous matrix throughout the burning event was successfully achieved under all φ values considered in this study. A simplified (one-dimensional) analytical model was developed to examine achievable range of TDR. It was found that the expected achievable TDR was higher than the value for the conventional spray combustion technology (∼ 6). Thus, the present burner system with a thick and coarse porous matrix was effective for attaining stable premixed combustion and a high TDR.

It is shown that the transition to a new low-temperature method of convective drying leads to a reduction in grain drying costs.The implementation of this method is confirmed to require expanded temperatures generated by the TBM-1.7 furnace unit that the SZSh-16A shaft dryer is equipped with. It is noted that a plant-manufactured burner nozzle works smoothly only when the fuel consumption is 40-100 kilograms per hour, and the air heating temperatures are 50-130 degrees Celsius. (Research purpose) To determine the jet optimal parameters for smooth operation of the nozzle in the TBM-1.7 combustion unit working on the liquid fuel at the extended air heating temperatures of 15-130 degrees Celsius. (Materials and methods) The designs of four types of jets were studied on the burner nozzle of the TBM-1.7 combustion unit. In total, the operation of 160 jets was examined. The jets were made of steel. They differed in the number of holes, their length, diameter, the availability of threads. (Results and discussion) It is determined that the nozzle smooth operation is provided only by jets with threaded holes, whose optimal length is 4 millimeters. The air heating temperature of 15-25 degrees Celsius is provided by M3 four-hole jet, and the temperature of 25-40 degrees Celsius is provided by M4 three-hole jet. (Conclusions) It is found that jets with smooth holes, regardless of their types, do not provide fuel combustion. It is found that the transition to a new low-temperature convective method led to a reduction in fuel consumption during the drying process, which, in turn, made it possible to save 300 thousand rubles during the harvesting period on the experimental farm in 2022.

The aim of this study is to determine the influences of chosen primary (mixing of standard recommended fuel with additives) and secondary (oxidation catalyst) measures on the composition of flue gas, produced by combustion of liquid fuels in a standard ethanol burner. The total amount of emitted NOxwas decreased by 63%, after replacing the fuel by pure methanol, while the total amount of emitted CO was the lowest during pure ethanol usage. The implementation of chosen catalyst significantly affected the total amount of emitted CO with high conversion rates (82%–90%). The amount of emitted water vapour was increased by 0%–25% (per 1 kWh of released energy) when additives were used. Overall, applying the mentioned measures together proved to be very beneficial from the total amount of emitted CO and NOxpoint of view.

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Currently, thermal power plants operating on hydrocarbon fuels (gas, fuel oil, peat, shale, etc.) are one of the main sources of electricity. An effective and promising method for suppressing harmful emissions (NOx, carbon oxides, soot) from the combustion of fossil fuels is the injection of steam into the combustion chamber. The influence of various mathematical submodels was studied on the accuracy of the numerical simulation of the process of n-heptane combustion in a laboratory burner with steam additive to the reaction zone as a promising chemical engineering method for the disposal of substandard liquid fuels and combustible waste with the production of thermal energy. The problem was solved in a three-dimensional stationary formulation. Systematic verification of these submodels, and a comparison of the results of the calculation with the experimental data obtained were carried out. The comparison with the experimental data was carried out for gas components and temperature distribution at the burner outlet; high agreement of the results was achieved. Optimal submodels of the methodology for calculating the process of fuel combustion in a jet of steam were determined. The best agreement with the experiment data was obtained using the EDC model in combination with a mechanism consisting of 60 components and 305 elementary reactions. More correct simulation results were obtained using the RSM turbulence model and the DO radiation model. [ABSTRACT FROM AUTHOR]

Swirl burners are widely used in numerous practical applications since they are characterized by low pollutant emission and a wide operating range. Besides reliable operation, a burner must fulfill noise emission regulations, which is often a sound pressure level in dB(A) when people are affected. Therefore, the present paper evaluates the overall sound pressure level (OASPL) variation of a 15-kW liquid-fueled turbulent atmospheric swirl burner at various setups. Firstly, the combustion air flow rate was adjusted, which induced a swirl number modification due to the fixed swirl vanes. Secondly, the atomizing pressure of the plain-jet airblast atomizer was modified, which also affected the swirl number. High atomizing air jets notably increased combustion noise by intensifying the shear layer. Thirdly, a geometrical modification was performed; 0°–60° half cone angle quarls in 15° steps were installed on the lip of the baseline burner for extended flame stability. By filtering the OASPL to the V-shaped flames, a linearly decreasing trend was observed as a function of swirl number. Their derivative also has a linearly decreasing characteristic as a function of the atomizing pressure.

The formation of nitrogen, sulfur, and carbon oxides in burning fuel oil in boiler furnaces, the elevated water content arising during unloading fuel oil from or its storage in tanks, the formation of deposits in fuel facilities' equipment during its operation, and the high cost of fuel oil are serious obstacles to the use of fuel oil as the main or backup fuel at thermal power stations (TPS). During the long-term storage of fuel oil, water partly settles and distributes in the form of lens, interlayers, or drops that are several to hundreds of micrometers in size. Water cannot be completely removed from the fuel oil by settling since the water and the fuel have nearly the same density. At present, fuel oil covers less than 2% of the fuel balance of TPSs. Considering the fact that there are regions in Russia where fuel oil is the only available fuel for boiler houses, the issues of fuel oil treatment as required for its burning or storage are urgent. Potential possibilities of the existing equipment for preparing fuel oil for burning in the form of fine water-fuel oil emulsions (WFOE) are examined, and the related performance effects are analyzed. The most promising and innovative method to produce WFOEs is the cavitation treatment of immiscible liquids. The equipment designs for cavitation treatment of viscous fluids at boiler houses and TPSs are reviewed. Preference is given to static type cavitation apparatuses featuring high capacity, reliability, and low capital and operating costs. [ABSTRACT FROM AUTHOR]

In this paper, numerical and experimental investigations have been carried out to delineate the effect of various spray parameters on CO and NO x emissions in a combustor operating in flameless combustion mode with kerosene fuel. Thermal input was varied in the range of 20–41 kW (Heat release density ∼5–10 MW/m 3 ) with different fuel injectors and various fuel injection pressures. Spray parameters were varied by employing two separate conditions (i) same fuel flow rate with different solid cone pressure swirl spray nozzles (N1 – N4) and injection pressures (2.5–14 bar) to achieve varying spray parameters at same thermal input (ii) same fuel injection nozzle at different fuel flow rates and injection pressures (5–13 bar) to understand their effect on combustion and emissions. In both the cases, Sauter Mean Diameter (SMD) varied in the range of 34–58 μm with spray cone angle varying from 42° to 56° using different nozzles and fuel injection pressures. Tangential air injection helped achieve higher recirculation of hot combustion products in the primary zone of the combustor for all thermal inputs. The finer sprays obtained at higher injection pressures helped achieve improved recirculation and better mixing, resulting in uniform temperature and hence reduced CO and NO x emissions. The measured CO and NO x emissions were in the range of 28–70 ppm and 2–10 ppm for all heat inputs with global equivalence ratio varying from ϕ = 0.6 to 1, respectively. Measured acoustic emission levels were in the range of 98–101 dB and 104–107 dB for the flameless and transition mode respectively. The measured CO, NO x and acoustic emissions are an order of magnitude smaller those corresponding to conventional combustion mode. It was observed that coarser sprays led to a significant increase in acoustic emissions, relatively non-uniform temperature distribution and higher CO, NO x emissions during flameless combustion mode. [ABSTRACT FROM AUTHOR]

This study presents the design and development of a novel, self-aspirating, liquid fuel, annular, porous medium burner (SLAPMB) with stabilized flame inside a packed bed using liquid ethanol. The SLAPMB is built in an annular shape with an open area at the center for more secondary air ( SA ) entrainment, and a vaporizer for vaporizing the liquid ethanol is embedded inside the burner wall. The transient period of the SLAPMB during the switching period from LPG to ethanol vapor is investigated for understanding the simultaneous combustion phenomena within the porous medium burner and the vaporization process within the vaporizer. Effects of the primary air ( PA ), firing rate ( FR ) on the flame stabilization, temperature profiles within the burner, and emission characteristics are investigated. The PA strongly affects the flame stabilization within the burner. Flame moves upstream as the PA increases and vice versa with the flame moving downstream as the PA decreases. The existence of an SA inlet can significantly reduce CO emission and increase thermal efficiency. The ethanol flame can be successfully stabilized within the burner with a temperature peak occurring at the middle region of the burner with a relatively low emission of CO and NOx of about 900 ppm and 50 ppm, respectively. Thermal efficiency is 33.6%. The SLAPMB can offer a relatively wide turndown ratio with the firing rate ( FR ) ranging from 16 kW to 23 kW without the problem of flame stabilization and emission. [ABSTRACT FROM AUTHOR]

• Diesel combustion in the pre-chamber vortex burner with a steam blast atomizer is numerically studied. • The flow structure inside the burner and characteristics of fuel combustion are determined. • The air excess ratio in the combustion chamber with the natural air supply is 0.96–1.23. • At mass steam concentration of 44–50%, emissions are CO = 5 ppm and NOx = 27 ppm. • The concentration of toxic emissions meets the EN:267 standard. The combustion of diesel fuel in a pre-chamber vortex burner with a steam blast atomizer has been studied numerically. The well-proven k-w SST (URANS) model was chosen for calculations. Combustion was simulated using the Eddy Dissipation Concept (EDC) model, taking into account detailed chemical mechanisms in turbulent reacting flows. The results of testing the selected mathematical model showed good agreement of calculations with the known experimental data, a high agreement of the results was achieved: temperature, CO, NOx, O2, and CO2. The influence of steam and fuel flow rates on the flow structure and physicochemical processes in the burner and at the nozzle outlet has been studied. The structure of the flow inside the burner was shown. A high-velocity jet of steam ejects fuel, oxidizer flow and hot combustion products, forming a large zone of circulation and intense mixing. The influence of burner operating regimes on fuel underburning and environmental performance has been investigated. It was found that in the selected range an increase in the relative steam flow rate leads to almost complete combustion of fuel inside the burner. In the combustion chamber with a natural air supply, the excess air ratio was (0.96–1.23). For the considered fuel flow rate of (0.8–1.2 kg/h), the concentration of toxic emissions meets the environmental standard EN:267 – CO < 40 ppm, NOx < 50 ppm. The minimum emissions of CO = 5 ppm and NOx = 27 ppm are achieved at mass steam concentration of 44–50%. [ABSTRACT FROM AUTHOR]

Abstract: The potential of biodiesel as an alternative fuel for various applications leads to an investigation to understand the combustion characteristics of pure and blended biodiesel. The concept of internal recirculation of combustion products is employed in a high swirl and low emission burner to reduce emissions. Due to high boiling point (613K) and SMD (37μm) of biodiesel, air preheating with minimum temperature above the boiling point of biodiesel is considered. Air at different temperatures of 623, 673 and 703K is injected tangentially. Swirl flow pattern in the combustor creates the central low pressure zone due to vortex breakdown and improves the recirculation of combustion products. Results in improved mixing and high residence time of reactants. Biodiesel is blended with diesel to reduce the surface tension and viscosity and improve the combustion characteristics. Literature has little consensus on NOx emissions from the combustion system operating with biodiesel. Therefore, the present study aims to reduce the thermal NO formation through the concept of exhaust gas recirculation. The CO, HC, NOx emissions and soot-volume fraction from biodiesel (100B0D), 50% blending (50B50D), diesel and kerosene are compared at different air preheating temperatures. A drastic reduction in emissions is observed in 50B50D as compared with pure biodiesel. [Copyright &y& Elsevier]

Abstract: In this work we analyze a diffusion flame established in a low-permeability medium. A low-strained impinging jet of oxidant against a pool of low-volatility liquid fuel is the considered geometry. Owing to the differences on the transport properties of gas, liquid and solid, the problem presents physical processes occurring in different length scales. Hence, we perform an asymptotic analysis in order to obtain the profiles of temperature and species concentration in each length scale. As a result of the low-permeability feature of the medium, the velocity field is determined mainly by the gradient pressure (Darcy equation). The viscous effects become confined into small regions near the stagnation-point and the liquid–fuel interface. The effects of porosity, fuel Lewis number, strain-rate and liquid–fuel volatility on the flame temperature, flame position and vaporization rate are discussed. It is shown that the low-permeability medium is necessary in order to sustain the vaporization process of the low-volatility liquid fuel, as it enhances the heat transfer to the fuel reservoir. This model is valid for high rates of interphase heat exchange and low rates of strain. [Copyright &y& Elsevier]

Highlights: [•] Examined distributed combustion for gas turbines applications using HiTAC. [•] Gaseous, liquid, conventional and bio-fuels are examined with ultra-low emissions. [•] Novel design of fuel flexibility without any atomizer for liquid fuel sprays. [•] Demonstrated fuel flexibility with emissions <4.5PPM of NO for different fuels. [•] Demonstrated CO emission <10ppm for methane based fuels, <40PPM for others. [Copyright &y& Elsevier]

Abstract: This paper presents the experimental and numerical results for a two stage combustor capable of achieving flameless combustion mode with 20kW thermal input and heat release density up to 5MW/m3. The fuel and oxidizer are supplied at ambient conditions. The concept of high swirl flows has been adopted to achieve high internal recirculation rates, residence time and increased dilution of the fresh reactants in the primary combustion zone, resulting in flameless combustion mode. Air is injected through four tangential injection ports located near the bottom of the combustor and liquid fuel is injected through a centrally mounted pressure swirl injector. Preliminary computational analysis of the flow features shows that decrease in the exit port diameter of the primary chamber increases the recirculation rate of combustion products and helps in achieving the flameless combustion mode. Based on preliminary computational studies, a 30mm primary chamber exit port diameter is chosen for experimental studies. Detailed experimental investigations show that flameless combustion mode was achieved with evenly distributed combustion reaction zone and uniform temperature distribution in the combustor. The CO and NO x emissions are reduced from 350 to 11ppm and 45 to 12ppm respectively at an equivalence ratio of 0.92, as operation of the combustor changes from conventional to flameless combustion mode. Measurement of CO and NO x emissions show that these emissions are reduced by an order of magnitude when operated in flameless combustion mode. The acoustic emission levels are reduced by 6–8dB as combustion mode shifts from conventional mode to flameless combustion mode. [Copyright &y& Elsevier]

Abstract: Utilization of a porous medium for combustion of liquid fuels is proved to be a promising approach for future applications. The porous medium burner for liquid fuels is more advantageous than the conventional open spray flame burner for several reasons; these include enhanced evaporation of droplet spray owing to regenerative combustion characteristics, low emission of pollutants, high combustion intensity with moderate turn-down ratio and compactness. This article provides a comprehensive picture of the global scenario of research and developments in combustion of liquid fuels within a porous medium that enable a researcher to determine the direction of further investigation. Accordingly, a glossary of the important terminology, the modeling approach, advances in numerical and experimental works and applications are included. The papers published in standard journals are reviewed and summarized with relevant comments and suggestions for future work. [Copyright &y& Elsevier]

• N-heptane combustion in a low emission burner has been investigated numerically. • Effect of steam and air forced supply on the combustion characteristics was analyzed. • Soot and NOx formation are significantly reduced with increasing steam flow rate. Combustion of n-heptane in a laboratory pattern of an original evaporative-type burner with the supply of air or superheated steam to the reaction zone was studied experimentally and numerically. Turbulence was simulated on the basis of the k-ω SST RANS model. Combustion was simulated using the Eddy Dissipation Concept (EDC) model with a detailed kinetic mechanism. The developed mathematical model was verified; a good agreement between calculation results and obtained experimental data is shown. For the first time, a comparative analysis of the effect of forced supply of steam and air on the local and integral characteristics of combustion is carried out. Radical difference in the effect of steam supply in comparison with air supply on reducing emissions of nitrogen oxides and soot from the burner is shown. The burner operating regimes have been studied in detail in a wide range of flow rates of supplied steam and fuel. It has been found that with an increase in steam flow rate, underburning, soot formation and production of nitrogen oxides are significantly reduced. [ABSTRACT FROM AUTHOR]

Abstract: Combustion of kerosene inside porous inert medium (PIM) has been investigated with the goal of reducing the emissions of nitric oxides (NO x ), carbon monoxide (CO) and soot. Silicon-carbide (SiC) coated carbon foam is used as PIM to attain high structural strength. The two-zone porous burner design consists of preheat and combustion sections. Different PIM configurations were tested by stacking together square porous pieces of 2.5cm thickness. Two types of fuel injectors are considered: (i) in the air-assist injector, approximately 5% of the combustion air is used for atomization and the remaining air enters as the primary co-flow around the injector, and (ii) in the swirling-air injector, all of the combustion air enters the injector to create a swirling flow around the fuel jet to enhance atomization and fuel–air premixing. The distance between the injector and PIM inlet is a key operational parameter, which was varied in experiments with both injectors over a range of equivalence ratios and heat release rates. The NO x and CO emissions were measured to optimize the PIM configuration with minimum emissions. Results show stable combustion over a wide operating range. Three combustor operational regimes are identified depending upon the injector location. [Copyright &y& Elsevier]

Abstract: The present model is based on a combined self-sustained liquid fuel vaporization – combustion system, where the liquid fuel vaporization occurs on a wetted wall plate with energy transferred through the plate from the combustion of vaporized oil. The vaporization energy has been derived through the radiative interaction of the vaporizing plate and an upstream end surface of the porous medium. The inert porous medium, used in the flow passage of combustion gas, is allowed to emit and absorb radiant energy. The radiative heat flux equations for the porous medium have been derived using the two-flux gray approximation. The work analyzes the effect of emissivities of vaporizing plate and porous medium, the optical thickness of medium and equivalence ratio on the kerosene vaporization rate, combustion temperature and radiative output of the system. Combination of low and high emissivities of vaporizing plate and porous medium respectively with low optical thickness of medium makes the system operable over a wide range of power. The study covers the data concerning the design and operating characteristics of a practical system. [Copyright &y& Elsevier]

Abstract: Present work is a numerical analysis of fuel oil combustion inside an inert porous medium where fuel oil flows through the porous medium under gravity wetting its solid wall with concurrent movement of liquid fuel and air under steady state conditions. A one-dimensional heat transfer model has been developed under steady state conditions using a single step global reaction mechanism. The effects of optical thickness, emissivity of medium, flame position and reaction enthalpy flux on radiation energy output efficiency as well as the temperature, position and thickness of vaporization zone have been presented using kerosene as fuel. Low values of optical thickness and emissivity of porous medium will ensure efficient combustion, maximize downstream radiative output with minimum upstream radiative loss. [Copyright &y& Elsevier]

Abstract: To avoid the complexities associated with the droplet/vapor transport and nonuniform evaporation processes, a fundamental investigation of liquid fuel combustion in idealized configurations is very useful. An experimental–computational investigation of prevaporized n-heptane nonpremixed and partially premixed flames established in a counterflow burner is described. There is a general agreement between various facets of our nonpremixed flame measurements and the literature data. The partially premixed flames are characterized by a double flame structure. This becomes more distinct as the strain rate decreases and partial premixing increases, which also increases the separation distance between the two reaction zones. The peak partially premixed flame temperature increases with increasing premixing of the fuel stream. The peak CO2 and H2O concentrations are relatively insensitive to partial premixing. The CO and H2 peak concentrations on the premixed side increase as the fuel-side equivalence ratio decreases. These species are transported to the nonpremixed reaction zone where they oxidize. The C2 species have peaks in the premixed reaction zone. The concentrations of olefins are ten times larger than those of the corresponding paraffins. The oxidizer is present in partially premixed flames throughout the combustion system and there are no regions characterized by simultaneous high temperature and high fuel concentration. As a result, pyrolysis reactions leading to soot formation are greatly diminished. [Copyright &y& Elsevier]

The large presence of aromatic compounds in distillate fossil fuels should allow, in line of principle, to follow the fuel consumption and/or the presence of unburned fuel in a high temperature environment like a burner or the exhaust of combustion systems by exploiting the high fluorescence emission of aromatic fuel components. To this aim an UV-excited fluorescence source has to be used since the aromatic fuel components are strongly fluorescing in the UV region of the emission spectrum.In this work UV-excited laser induced fluorescence (LIF) diagnostics was applied to spray flames of kerosene in order to follow the fuel consumption and the formation of aromatic species. A strong UV signal was detected in the spray region of the flame that presented a shape similar to that found in the LIF spectra preliminary measured on the cold spray and in the room-temperature fluorescence of fuel solutions.The decrease of UV signal along the spray flame region was associated to the consumption of the fuel, but more difficult seems to be the attribution of a broad visible emission, that is present downstream of the flame.The visible emission feature could be assigned to flame-formed PAH species contained in the high molecular weight species, hypothesizing that their fluorescence spectra are shifted toward the visible for effect of the high temperature flame environment. [Copyright &y& Elsevier]