Burning Speed Research Articles

Detailed kinetics for anisole oxidation under various range of operating conditions

Biofuels produced from biomass are considered a potential source of renewable energy that can be used as an alternative to fossil fuels. Lignocellulosic biomass produces phenolic compounds like anisole which is a promising source of biofuel. Anisole (methoxybenzene) is an aromatic compound and has advantageous features as a drop-in fuel in combustion devices. In this work, a detailed mechanism of anisole is generated to numerically study the oxidation of this fuel at engine-relevant conditions. The comprehensive model is developed using the reaction mechanism generator (RMG). The mechanism is used for calculating laminar burning speed (LBS), ignition delay time (IDT), and species concentration, to compare with experimental data. Sensitivity and reaction path flux analyses are considered in evaluating the mechanism. Important reactions are identified which have a very significant effect on the prediction of the model. The rate of these important reactions is studied from the literature to make the mechanism perform well for a wide range of conditions. The final mechanism named PCRL-Mech3 contains 466 species and 3691 reactions. PCRL-Mech3 shows a successful validation of IDT at both rapid compression machine (RCM) and shock tube (ST) experiment which cover temperatures of 800–1600 K and pressures of 10–40 atm. Validation of LBS is performed using recently published work by the same group. This data enables the opportunity to evaluate and improve PCRL-Mech3 for a wider range of LBS conditions (i.e., 0.5–5.5 atm, 460–550 K, and 0.8–1.4 equivalence ratio). Species concentration of anisole and stable intermediates of final mechanism match reasonably well with different jet stirred reactor experiments. Compared with the literature, the mechanism can show improved prediction over a larger span of engine-relevant conditions that also helps to identify the regimes where more experimental and numerical improvement is required.

Premixed syngas/air combustion in closed ducts with varied aspect ratios and initial pressures

Syngas is a promising renewable energy carrier, and its combustion can result in a significant reduction of pollutant emissions. However, syngas has various production sources, its compositions are diverse accordingly. That brings some challenges in its practical application. Therefore, in order to deeply investigate the premixed stoichiometric syngas/air combustion in confined spaces, experiments were conducted in a closed duct with varied aspect ratios (12, 26 and 40) and initial pressures from 0.5 atm to 1.5 atm. Flame shape evolutions in varied cases were captured through high-speed photography, and four flame speed oscillation regimes were distinguished qualitatively. The pressure buildup was recorded by sensors and scrutinized by dimensionless method. The results denoted the propagation dynamics became more violent with higher initial pressure or aspect ratio. Further, the combustion instability was examined, and it indicated the acoustic effect and the Rayleigh-Taylor/Richtmyer-Meshkov instability would be stronger in cases with large aspect ratio, resulting in the deformation of elongated tulip flame. Besides, the Bychkov's theory considering gas compression effect was validated by the experimental data. The discrepancy between them was interpreted with a comprehensive view of enlarged laminar burning speed, non-adiabatic sidewall and finite flame front thickness.

Effect of MnO2 morphology on the thermal properties and combustion behavior of nano-Al/MnO2 thermite

Al/granular MnO2 and Al/rod MnO2 thermite samples were prepared to investigate the effects of different morphologies of MnO2 on the thermal properties and combustion behavior of nano-Al/MnO2 thermite. The morphology and thermal properties of the thermite were characterized by field emission scanning electron microscopy (FE-SEM), x-ray diffractometry (XRD), and differential scanning calorimetry (DSC). DSC results show that the Al/rod MnO2 releases 1274.39 J·mol−1 heat, which is 292.58 J·mol−1 more than the Al/granular MnO2. The initial reaction temperature of Al/rod MnO2 is 567.39 °C, which is delayed by 17.39 °C versus 550 °C of Al/granular MnO2. Non-isothermal thermodynamic analysis was used to measure the activation energy of Al/rod MnO2 to be 234.36 kJ·mol−1, which is 46.53 kJ·mol−1 higher than that of Al/granular MnO2. This corresponds to an increase in the ignition temperature in the DSC curve and indicating a higher safety profile. In the open burning experiment, the burning time of Al/granular MnO2 was longer and sparks sputtered around the flame. The Al/rod MnO2 has a large combustion flame and a fast combustion rate. The light intensity peaks of the two groups of samples are close in the light intensity test. The light intensity existence time of Al/rod MnO2 is 0.0146 s, which is 0.094 s shorter than Al/granular MnO2. This shows that the combustion rate of Al/rod MnO2 is much faster than that of Al/granular MnO2. The closed-tube combustion experiment shows that the combustion wave velocity of Al/rod MnO2 increases first and then decreases; the maximum wave velocity reaches 339.6 m·s−1, and Al/granular MnO2 cannot self-propagate combustion in the microporous environment. In the constant volume combustion experiment, the peak combustion pressure of Al/rod MnO2 is 0.938 Mpa, and the peak value of Al/granular MnO2 combustion pressure is 0.581 Mpa; the difference is obvious. This shows that the rod MnO2 gas production performance is better. According to the duration of the pressure peak, the burning speed of Al/rod MnO2 in the light intensity test is confirmed again to be much faster than that of Al/granular MnO2. The Al/rod MnO2 is better than Al/granular MnO2 in thermal and combustion performance and is also safer. This provides a basis for future performance and safety research on aluminothermic materials.

Shock Tube and Flame Speed Measurements of 2,4,4-Trimethyl-1-Pentene: A Co-Optima Biofuel

Abstract The combustion of 2,4,4-trimethyl-1-pentene (diisobutylene, C8H16), which is a biofuel and a component of surrogate fuels, is examined in this work. Carbon monoxide time–histories and ignition delay times are collected behind reflected shock waves utilizing a shock tube and mid-infrared laser absorption spectroscopy. Measurements were obtained near 10 atm pressure during stoichiometric oxidation of 0.15%C8H16/O2/Ar. Simulated results from chemical kinetic models are provided, and sensitivity analyses are used to discuss differences between models for both ignition delay times and carbon monoxide formation. In addition, laminar burning speeds are obtained at 1 atm, 428 K, and equivalence ratios, phi, between 0.91 and 1.52 inside a spherical chamber facility. Measured burning speeds are found to be less than that of ethanol over the equivalence ratio span. Burning speed measurements are compared to predictions of chemical kinetic mechanisms and are in agreement for the richest conditions; however, at lean conditions, the model predicts a far slower-burning speed. The maximum burning speed occurs at an equivalence ratio of 1.08 with a magnitude of 0.70 m/s. The current work provides the crucial experimental data needed for assessing the feasibility of this biofuel and for the development of future combustion chemical kinetics models.

Effects of pre-mixed gas composition on combustion characteristics of micro pilot dual fuel (MPDF) in a heavy-duty dual fuel engine

The effects of premixed gas compositions on the combustion characteristics in micro pilot duel fuel (MPDF) conditions were investigated. Propane, hydrogen, and carbon dioxide gases were added to methane gas, and engine experiments were conducted under various premixed gas compositions. A single-cylinder heavy-duty engine with a combustion chamber volume of 1100 mm3 and compression ratio of 17.0 was used. A 55 kW DC dynamometer was used to operate the single-cylinder dual-fuel engine at a constant engine speed. At high propane mixture ratios, knocking combustion occurred, accompanied by intense engine vibrations, owing to the low octane number of propane. Knocking combustion led to an increase in the combustion variation and ringing intensity (which represents the knocking combustion intensity). In contrast, at high ratios of hydrogen, which has a high octane number, knocking combustion was suppressed, and the speed of combustion was lower than that in the case of high propane mixture ratios. The optimum conditions corresponded to a ringing intensity of 3–5 MW/m2. The addition of even a small amount of propane gas enhanced the engine performances in misfiring conditions. In contrast, a considerable amount of hydrogen gas was required to prevent abnormal combustion because of the low density of hydrogen gas. The presence of carbon dioxide effectively stabilized MPDF combustion by suppressing knocking combustion.

Cylinder-to-cylinder variation of knock and effects of mixture formation on knock tendency for a heavy-duty spark ignition methanol engine

The knock characteristics of a high-pressure port fuel injection heavy-duty SI engine fueled with pure methanol were investigated experimentally and numerically. This paper aims to provide the optimization direction of the injection strategy from the perspective of knock suppression and thermal efficiency improvement. Both experiment and simulation prove that injection during the intake stroke with high injection pressure can mitigate knock because the strong interaction between spray and intake flow helps to form the more homogeneous and lower temperature mixture which prolongs the ignition delay of end-gas. As the injection timing (αinj) varies from 320°CA to 480°CA, the combustion speed and thermal efficiency increase first and then decrease, while the knock tendency is the opposite. Take the combustion at αinj of 320°CA as a baseline, the faster combustion speed at αinj of 380°CA caused by the homogeneous mixture contributes to the higher thermal efficiency, while that of 480°CA caused by the higher temperature further enhances the knock tendency. There is a significant cylinder-to-cylinder variation of the knock tendency. The knock tendency of the cylinder with the less fresh air charge is lower because of the lower in-cylinder temperature and pressure.

A Study on the Effect of Initial Temperature on Combustion Characteristics of RDX Based on the Optical Diagnosis Methods

The purpose of this work is to investigate the effect of different initial temperatures on the combustion characteristics of RDX materials. In the experiments, the electric heating plate below the RDX samples was controlled so that the initial temperatures were set to be 298, 323, 373, 423, and 473 K (below the material melting point), respectively. Three optical diagnostic methods were employed to capture the ignition process, flame thermal radiation, and NO distribution in the flame at different conditions. The results show that the increase in initial temperature can improve the reaction rate, shorten the ignition delay time, and increase the flame combustion intensity and speed, because of the earlier evaporation and pyrolysis process in the RDX samples. Increasing the initial temperature also enhances the thermal effect of the flame, which is related to the generation and consumption of NO to a certain extent.

Laminar Burning Speed of Aviation Kerosene at Low Pressures

Aero-engine combustors may experience extreme low pressures in the case of an in-flight shutdown, which makes the study of aviation kerosene flame propagation characteristics at low pressures important. The present work examined flame propagation during the combustion of aviation kerosene over the pressure range from 25 to 100 kPa using a constant-volume bomb apparatus. The laminar burning speeds at different initial pressures, temperatures and equivalence ratios were measured and compared. In addition, numerical simulations were used to examine the reaction sensitivity of the laminar burning speed at low pressure. In trials at the lean flammability limit, the data indicated that it was more difficult to ignite the fuel under a lower pressure condition of 25 kPa and a lower temperature condition of 420 K. The experimental results of laminar burning speed were fitted to an equation providing the laminar burning speeds expected at different pressures (25–100 kPa), temperatures (400–480 K) and equivalence ratios (0.8–1.5). The temperature index (α=1.76) and pressure index (β=−0.15) of the fitting equation were obtained. Both hydrodynamic and diffusional thermal flame instabilities were found to be suppressed at low pressures. The negative effects of two specific reactions on laminar burning speed were greatly reduced at these same low pressures of 25 kPa.

Combustion Performance and Low NOx Emissions of a Dimethyl Ether Compression-Ignition Engine at High Injection Pressure and High Exhaust Gas Recirculation Rate

Dimethyl ether (DME) is a promising alternative to diesel for compression-ignition (CI) engines used in various industrial applications. However, the high nitrogen oxide (NOx) emissions of DME combustion have restricted its use. The primary cause of high NOx emissions is a high combustion temperature. In this study, a high exhaust gas recirculation (EGR) rate was used when testing a common-rail direct injection CI engine suitable (with minor modifications) for a passenger car. A modified fuel supply system created high injection pressure during evaluation of combustion performance. The physical and chemical properties of DME were the principal determinants of the ignition delay, combustion speed, and heat release rate. Although a high injection pressure accelerated formation of the fuel-air mixture and the combustion speed, combustion performance deteriorated with increased NOx emissions. An increased EGR rate affected combustion and the NOx concentration. A high EGR rate effectively reduced NOx formation and emission under low-temperature combustion conditions. Also, the good DME combustion characteristics were maintained when the EGR rate was high, unlike for an ultra-low sulfur diesel engine.

Study on Co-firing Characteristics and NOx emission of Ammonia/Propane

Reducing the use of carbon fuel is one of the important measures to achieve zero carbon emission. As a carbon-free and high-hydrogen fuel, ammonia has promising application prospects because of its high energy density and low transportation and storage cost. Due to the characteristics of high ignition temperature, low flame propagation combustion speed and high NOx concentration in the combustion process, its wide application needs further research. In this paper, the co-combustion and the NOx emission characteristics of ammonia mixed with propane are experimental investigated for pure ammonia, 5% propane and 10% propane mixtures. The effects of ammonia/propane ratio, air excess coefficient and inlet gas oxygen concentration on combustion and NOx emission characteristics are explored. The results obtained show that the highest NOx emission is formed by 10% propane ratio case, and the lowest NOx is for pure ammonia. With the increase of propane, the concentrations of NOx, NO and NO2 increase and the concentration of oxygen decreases. With the increase of air excess coefficient from 15% to 21%, NOx, NO and NO2 also increase, and the concentration of oxygen goes up. With the increase of inlet oxygen concentration from 15% to 21%, the concentrations of NOx and NO at the exit of furnace changes less for pure ammonia, and 75% increase for 5% propane; while for 10% propane, the concentration of NO first decreases rapidly from 1498ppm to 1071ppm with O2 decreasing from 15% to 18%, then increases to about 1700ppm again when the inlet O2 concentration increases from 18% to 21%.

Theoretical and experimental research of an automotive gasoline engine fuelled with butanol

Among alcohols used for spark ignition engine fuelling, butanol can be a viable alternative fuel due to its very good combustion proprieties. Butanol has a high miscibility with the gasoline and stable blends can be assured. The higher oxygen content and the higher combustion speed of butanol comparative with gasoline are proprieties which may improve the combustion process and may lead to the reduction of greenhouse gases level such as CO2 and pollutants like CO, HC, and NOx. A theoretical and experimental study was conducted on a spark-ignition engine with 1.5L displacement fuelled with n-butanol-gasoline blends at different volume percentages and different excess air coefficients at the 55% engine load of and 2500 min-1 engine speed. Starting from a predefined model in AMESim was developed and calibrated a physical-mathematical model for the process’s simulation from the engine cylinder. The objective of the paper is to get a good representation of the real engine in numeric to have a better prediction of the engine performance at the different operating conditions. The theoretical and experimental investigations show important advantages of n-butanol in blend with gasoline: the increase of the thermal efficiency due to the stable engine operation at lean mixtures use.

Effect of background turbulent field on ion current characteristics of methane-air premixed combustion

Ion current detection technology has a broad application prospect in natural gas engines. The effect of background turbulent environment on ionic current characteristics of methane - air mixture premixed combustion needs further study. The premixed combustion of methane-air mixtures under different turbulence intensities was studied on the constant volume combustor with controllable turbulence intensities. The effects of turbulence intensity on flame image, combustion pressure and ion current signal during combustion were analyzed. The ion current calculation model was built by coupling Cantera chemical reaction calculation program in the MATLAB environment. The variation of the concentration of the main species under different conditions was analyzed and the ion current signals under different turbulent conditions were simulated. The results show that in turbulent environment, the flame front appears fold and cellular structure, which increases the flame front area and accelerates the combustion speed. With the increase of turbulence intensity, the peak of combustion pressure increases and the peak time is advanced. The ion current appeared earlier in turbulent environment, and the duration of ion current decreased with the increase of turbulence intensity. When the equivalent ratio is near 1, the species concentration change greatly due to the influence of incomplete combustion. The concentration of species except water and carbon dioxide increases with the increase of temperature. The ion current calculation model can predict the overall trend of ion current signal in turbulent premixed combustion, but the simulation results of ion current signal in the later stage of combustion are too large.

Экспериментальные исследования горения сферических водородно-воздушных смесей в открытом пространстве при воздействии на них замедляющих и ускоряющих факторов

It is shown that the experimental studies of flame propagation speed, the maximum pressure of the explosion of hydrogen-air mixtures were carried out in free space under the influence of slowing down and accelerating factors, such as power and type of ignition source, the effect of flame acceleration in the pipe, the effect of obstacles on the flame propagation path, the volume and composition of the combustible mixture when the content of the oxidizing agent or phlegmatizer changes in it. The dependence was established allowing to estimate the volume of a hydrogen-air mixture, during the combustion of which one can expect the burning speed that is close to the speed of sound in the initial mixture, and at which the transition of deflagration combustion to detonation is possible. When phlegmatizing hydrogen-air and oxygen-hydrogen mixtures with inert gases, such as nitrogen for example, the effect of reducing the burning speed and explosion pressure is achieved. The processes and conditions for the transition of deflagration combustion to detonation of free volumes of hydrogen-air mixtures and mixtures enriched and depleted of oxygen, depending on the power of the ignition source, volume, composition of the mixture and its turbulence, were studied. It is noted that as the content of the inert gas in the mixture increases, these indicators decrease, and the profile of the pressure wave changes qualitatively. Turbulization of hydrogen-air and hydrogen-oxygen mixtures with dilution using nitrogen to certain limits by turbulators leads to an increase in the values of the apparent burning speed and the maximum speed of explosion burning, up to the transition to detonation. Irrigation of combustible mixtures with atomized water leads to the same effect.

The study on the influence of utilizing n-butanol at fuelling spark ignition engines

The ever-increasing emissions restrictions on internal combustion engines have led researchers into the study of alternative fuels solutions. As hybrid and electric vehicles started becoming more and more present in the markets worldwide, the popularity of conventional internal combustion engines started to decrease (we see this especially with diesel fueled engines). For spark ignition engines, alcohols and gasoline-blended mixes have proven to be an attractive solution in the last years. Out of these alcohols, we mention ethanol, methanol and butanol. Butanol is a promising solution because of its high oxygen content with the possibility of improving the combustion process and thus even reducing emissions. Butanol also has a high combustion speed and can potentially reduce the combustion duration while improving the overall thermal efficiency. High miscibility is another important aspect of butanol, allowing a higher percentage volume of butanol to be mixed with gasoline. The additional oxygen content may also improve combustion stability thus reducing cyclic variability. The objective of this study is to determine what is the impact of fueling a spark ignition engine with a blend of 10% vol. n-butanol and 90% vol. gasoline. The study will look at combustion stability, variability, thermal efficiency and emissions. A baseline was established at fueling the engine with pure gasoline at an engine speed of 2500 min−1 and an engine load of 55%. After the baseline, the same measurements were done at fueling with a blended mix of n-butanol and gasoline.

Electrode Design for Thermal and Nonthermal Plasma Discharge Inside a Constant Volume Combustion Chamber

Abstract Previous methods of achieving ignition in the Plasma, Combustion and Fluid imaging (PCFi) Laboratory’s Constant Volume Combustion Chamber (CVCC) utilizes either a standard or modified spark plug. The standard spark plug achieves a representation of side wall ignition (similar to a combustion engine), while the modified spark plug has an extended electrode to allow for a center camber ignition used for laminar burning speed (LBS) measurements. The creation of the modified spark plug required welding a stainless-steel (SS) wire to the electrode of the plug. This process is time consuming and requires a large quantity to effectively test a wide range of parameters such as gap size or electrode geometry. Two custom-design electrodes are presented in this paper which extend the experimental range of the PCFi’s CVCC system. Electrode Design A, gives the ability to test thin wire electrode with adjustability of gap size and different diameters through use of a compression fitting. This electrode design (i.e., tip-to-tip) is utilized with a traditional style of automotive ignition system (i.e., capacitive discharge) to study ignition process (i.e., thermal plasma) and spherical flame propagation. Electrode Design B, adds the ability to change tip geometry (i.e., plate-to-plate, tip-to-plate, tip-to-sphere, plate-to-sphere, etc.). In this paper, the plate-to-plate configuration is demonstrated to study uniform low-temperature nanosecond plasma discharge. Both electrode designs reduce structural weakness by removing the welded joint and allow for linear gap size adjustment. The electrode utilizes high-temperature epoxy, ceramic, and grafoil seals to make parameter adjustments easy and precise. The design was analyzed, prior to building and testing, based on the stress induced from the sealant, the total rated voltage, the rated temperature, and the fracture stress of the ceramic material. The stress induced in the electrodes was analyzed with finite element analysis (FEA) and the results were found to be within the limits of the material in terms of the compressive and fracture strengths. The maximum voltage was found to be around 30 kV. Design A is presented with three different electrode diameters of 1.3, 1, and 0.5 mm and Design B which utilizes a threaded connection for adjustable tip geometry. A sample of data, visual and electrical, is presented for the newly created electrode with a 0.5 mm diameter as well as combustion images for up to 10 atm of initial pressure for methane-air mixture. The new electrode design was able to survive several months of experimental use with few issues compared with the previous welded design.

Impact of ignition energy on the combustion performance of an SI heavy-duty stoichiometric operation natural gas engine

Nowadays, natural gas engine has been brought opportunities because of its low C/H ratio. For the stoichiometric combustion natural gas engine, improving its combustion stability is the main challenge under the condition of high EGR rate. To better understand the effect of the ignition energy on combustion stability, a detailed study was conducted by experiment. A 6-cylinder turbocharged intercooler natural gas heavy-duty engine was used in this study, and the ignition energy was controlled over a wide range under different working conditions. The results show that the ignition energy has an obvious effect on the ignition process of combustion including flame inception and early development when exceeds 100 mJ. Under heavy-load conditions, the elevating of early combustion speed can shorten the duration of combustion (DOC), manifesting more concentrated heat release, and improve the combustion stability and economy of the engine. However, under light-load conditions, the increase of early flame speed has little impact on the subsequent combustion process, and engine performance is not significantly improved. For a specific ignition energy under 1200r/min-80% load working condition, with the advancing of ignition timing (IT), there is a little effect on ignition delay time (IDT), but has more obvious effect on DOC. What’s more, the improvement amplitude of Pmax and indicated mean effective pressure (IMEP) gradually decrease with the advancing of IT at 105 mJ, but they are still larger than at 150 mJ. Overall, better engine performance and thermal efficiency can be achieved by organizing ignition energy.

Smart Host-Guest Energetic Material Constructed by Stabilizing Energetic Fuel Hydroxylamine in Lattice Cavity of 2,4,6,8,10,12-Hexanitrohexaazaisowurtzitane Significantly Enhanced the Detonation, Safety, Propulsion, and Combustion Performances.

The host-guest inclusion strategy has become a promising method for developing novel high-energy density materials (HEDMs). The selection of functional guest molecules was a strategic project, as it can not only enhance the detonation performance of host explosives but can also modify some of their suboptimal performances. Here, to improve the propulsion and combustion performances of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW), a novel energetic-energetic host-guest inclusion explosive was obtained by incorporating energetic rocket fuel, hydroxylamine (HA), into the lattice cavities of HNIW. Based on their perfect space matching, the crystallographic density of HNIW-HA was determined to be 2.00 g/cm3 at 296 K, which has reached the gold standard regarding the density of HEDMs. HNIW-HA also showed higher thermal stability (Td = 245.9 °C) and safety (H50 = 16.8 cm) and superior detonation velocity (DV = 9674 m/s) than the ε-HNIW. Additionally, because of the excellent combustion performance of HA, HNIW-HA possessed higher propulsion performances, including combustion speed (SC = 39.5 mg/s), combustion heat (QC = 8661 J/g), and specific impulse (Isp = 276.4 s), than ε-HNIW. Thus, the host-guest inclusion strategy has potential to surpass the limitations of energy density and suboptimal performances of single explosives and become a strategy for developing multipurpose intermolecular explosives.

A Comparison of Combustion Properties in Biomass-Coal Blends Using Characteristic and Kinetic Analyses.

This paper presents comparative research on the combustion of coal, wheat, corn straw (CS), beet residues after extracting sugar (BR), and their blends, coal–corn straw blends (CCSBs), coal–wheat blends (CWBs), and coal–beet residue blends (CBRBs), using thermogravimetric (TG) analysis under 10, 20, 30, 40 and 50 °C/min. The test results indicate that CS and wheat show better combustion properties than BR, which are recommended to be used in biomass combustion. Under the heating rate of 20 °C/min, the coal has the longest thermal reaction time when compared with 10 and 30 °C/min. Adding coal to the biomass can improve the burnout level of biomass materials (BM), reduce the burning speed, and make the reaction more thorough. The authors employed the Flynn–Wall–Ozawa (FWO) method and the Kissinger–Akahira–Sunose (KAS) method to calculate kinetics parameters. It was proven that overall, the FWO method is better than the KAS method for coal, BM, and coal–biomass blends (CBBs), as it provides higher correlations in this study. It is shown that adding coal to wheat and BR decreases the activation energy and makes conversion more stable under particular α. The authors selected a wider range of biomass raw materials, made more kinds of CBB, and conducted more studies on different heating rates. This research can provide useful insights into how to choose agricultural residuals and how to use them.

The Effect of Biogas Purification Process Using Calcium Oxide-Based Sorbents on the Diffusion Flame Combustion Characteristics

Biogas is an alternative energy source that could solve two problems at once, the problem of environmentally friendly energy needs and the problem of waste treatment. One of the sources of biogas is obtained from anaerobic bacterial fermentation of cow dung waste. The biogas fermentation process produces impurities such as carbon dioxide (CO2) as a combustion inhibitor. Carbon dioxide will inhibit the combustion reaction, resulting in incomplete combustion. The biogas purification process is needed to reduce the amount of carbon dioxide in the biogas. The purification process is carried out using an absorbent compound of calcium oxide (CaO) to bind carbon dioxide contained in the biogas. Thus, the purpose of this study was to analyze the effect of the biogas purification process using calcium oxide on the characteristics of the diffusion flame produced by combustion. The research was conducted experimentally using the physicochemical-absorption method of purification by flowing biogas through a purificator device that contained a purification solution. After passing through the purification solution, the biogas was regulated at a fuel flow rate of 3 liters/min and then proceed to the bunsen burner. The results showed that purification affected increasing the characteristics of the diffusion flame combustion due to the reduced amount of carbon dioxide in the biogas. This is indicated by increasing the purification molarity, it also increases the flame speed of combustion and the flame angle, as well as a decrease in the flame height.

Laminar Burning Speeds and Flammability Limits of CH4/O2 Mixtures With Varying N2 Dilution at Sub-Atmospheric Conditions

ABSTRACT This paper presents experimentally determined laminar burning speeds () of premixed methane/oxygen/nitrogen mixtures at sub-atmospheric conditions obtained by using the constant-pressure spherical flame method. The goal of the conducted experiments was to investigate the effects of nitrogen dilution and pressure reduction on the laminar flame speed and flammability limits of methane/oxygen mixtures. Nitrogen content was varied between 3.1 and 79.3 volume percent. at a target pressure of 0.5 bar was investigated. Actual pressure levels ranged between 0.506 and 0.568 bar. Experiments at 1 bar were conducted as a benchmark case of the setup compared to results from literature. The laminar flame speed is found to increase with decreasing nitrogen content and decreasing pressure. The obtained results show good agreement with simulated data using the several chemical reaction mechanisms within 4.8% for near stochiometric mixtures. The upper flammability limit (UFL) is shown to be pressure-sensitive while the lower flammability limit (LFL) remains stationary for both pressure levels compared to reference data at 1 bar. Furthermore, the LFL is shown to stay at 6% vol methane content, independent of nitrogen dilution ratio.