Ignition Combustion Research Articles

Gap initiation with 20.35 mm: an initiator integrating the Al/CuOx multilayer film and traditional electronic plug to enhance the ignition ability.

In order to enhance the ignition ability and reliability of traditional electronic initiators, a novel electronic initiator has been designed to integrate with a nanothermite multilayer film and an electrode plug. The Al/CuOx nanothermite multilayer film with different thickness is deposited on the surface of the electrode plug by magnetron sputtering which uses Pt–W wire as electronic resistance. The exothermicity of Al/CuOx nanothermite multilayer film is so favourable that the ignition ability of electronic initiator is significantly improved. The full firing-voltage sensitivity of the electronic initiator is 10.8 V. The thickness of Al/CuOx multilayer film has negligible effects on the ignition time and ignition energy, but leads to great impacts on the function time, the maximum length of combustion flame and ignition ability. The electrical ignition experiments have exhibited outstanding ignition ability, since the electronic initiator can easily fire the insensitive ignition composition of boron-potassium nitrate (B-KNO3) tablet in a gap of 20.35 mm. It proves that this novel proposal of remoulding the traditional electronic ignition devices will distinctly improve the ignition ability and reliability of electronic initiator.

A Computational Investigation of Nonpremixed Combustion of Natural Gas Injected Into Mixture of Argon and Oxygen

Natural gas is traditionally considered as a promising fuel in comparison with gasoline due to the potential of lower emissions and significant domestic reserves. These emissions can be further diminished by using noble gases, such as argon, instead of nitrogen as the working fluid in internal combustion engines. Furthermore, the use of argon as the working fluid can increase the thermodynamic efficiency due to its higher specific heat ratio. In comparison with premixed operation, the direct injection of natural gas enables the engine to reach higher compression ratios while avoiding knock. Using argon as the working fluid increases the in-cylinder temperature at top dead center (TDC) and enables the compression ignition (CI) of natural gas. In this numerical study, the combustion quality and ignition behavior of methane injected into a mixture of oxygen and argon have been investigated using a three-dimensional transient model of a constant volume combustion chamber (CVCC). A dynamic structure large eddy simulation (LES) model has been utilized to capture the behavior of the nonpremixed turbulent gaseous jet. A reduced mechanism consists of 22-species, and 104-reactions were coupled with the CFD solver. The simulation results show that the methane jet ignites at engine-relevant conditions when nitrogen is replaced by argon as the working fluid. Ignition delay times are compared across a variety of operating conditions to show how mixing affects jet development and flame characteristics.

Flame combustion of single wet-torrefied wood particle: Effects of pretreatment temperature and residence time

In this work, combustion behaviors of single wet-torrefied wood particle in a high temperature flame reactor (1226 °C, 4.2 vol% O2) simulating suspension biomass fired combustion were studied. 4 mm schima wood spheres were pretreated at various wet torrefaction (WT) conditions (at 175, 200, 225, 250 °C, for 5, 30, 60 min). For the WT pretreated particle has less mass than the raw feedstock, linear regressions were performed to fit ignition, devolatilization and char burnout time with R2 higher than 0.961, 0.995 and 0.988 respectively. The slopes of the fitting lines, indicating the conversion rates, were then used to assess the combustion time on the basis of per sample mass. All three combustion stages, i.e., ignition, devolatilization and char combustion, are prolonged after WT, which is related to the severity of the torrefaction conditions and the diminished AAEMs content. The largest variation lies in the char combustion behavior: the wet-torrefied wood particle produces significantly less char (accumulated char yield reduced from 8.2% to as low as 2.8% after WT), but the char combustion rate decreases up to a factor of 2.4–4.6. The reduced char reactivity is also confirmed by the TGA analysis.

Combustion Visualization of Partially Premixed and Non Premixed Diesel Fuel on Single Cylinder Optical Engine

Ignition and flame propagation phenomenon of diesel fuel combustion was investigated in an optical single cylinder engine. Conventional non-premixed diesel combustion and partially premixed combustion types were investigated. Experiments were performed on an optical single cylinder, heavy duty, four-stroke compression ignition engine with a quartz elongated piston bowl and 45° mirror was used for visualization as a measurement technique. . Self-ignition, flame propagation, heat rejection and effects on number of pilot injections on combustion visualization are investigated. In conventional diesel with closed and far pilot and partially premixed charge compression ignition (PCCI) tests were performed.

Simulating volatiles conversion in dense burning coal suspensions. 2. Extrapolations to commercial p.f. firing conditions

This simulation study uses the reaction mechanisms from Part 1 to simulate the chemical transformations along a single coal jet from an injector in a tangentially fired utility furnace. CFD simulations based on detailed engineering specifications determined the operating conditions along the coal jet, including coal mass loading, thermal histories, and transit times. A reactor network developed from the CFD results staged the chemistry in this environment with a utility grind of the same three diverse coal types in Part 1. Variations in mass loadings were then characterized to span the behavior from the commercial specification to the loading in the validation tests in Part 1.Volatiles combustion under commercial loadings in an isolated primary coal suspension alters the species concentrations but does not necessarily add or eliminate any fuel components or N-species. With all but low volatility coals, the effluents contain CH4, C2H2, H2, CO, HCN, and H2S, char, and soot. With low volatility coals, effluents have minimal or no gaseous hydrocarbons and appreciable amounts of NO. Soot burnout is negligible with all coals, and char burnout is appreciable with only low rank coals. Variations in loading do not change the dynamics of volatiles combustion or char ignition but progressively heavier loadings accelerate O2 elimination. The elimination of O2 allows gaseous reductants to accumulate along the post-flame region and drive the effluent NO concentration well below its maximum, even when extents of char and soot burnout are negligible. Coal quality primarily affects near-burner NO production via variations in char oxidation reactivity. Rapid char burning rates accelerate O2 consumption during volatiles combustion, which biases the partitioning of HCN toward N2, away from NO. The simulations also gave nearly identical tendencies for progressively greater O2 levels in the validation database in Part 1 and for progressively lighter loadings in the primary suspension simulations, provided that the thermal histories of both coal and gas are similar.

Influence of Carbon Nano-tube on Combustion, Performance and Emission Parameters of DI CI Engine Fuelled with Blends of Lemongrass Biodiesel

In the present investigation, bio-oil is extracted from lemongrass through steam distillation process, Single stage trans esterification using methanol and potassium hydroxide at molar ration of 1:8 yielded lemongrass biodiesel. The biodiesel was characterized using Gas chromatography Mass spectrometry and Fourier transforms infrared spectrometry analysis and found to have Behenic and Stearic acid in prominent proportions. The cetane number and calorific value was enhanced by ultrasonicating carbon Nano-tubes at various proportions. Kirloskar TV1 compression ignition engine coupled with eddy current dynamometer was employed to analyse the combustion, performance and emission characteristics. Addition of carbon Nano-tubes significantly affected the ignition delay and combustion duration. D80LGB20CNT100 fuel blend exhibited higher in-cylinder pressure up to 65.144 bars along with enhanced rate of heat release upto 73.953 kJ/kg at full load condition. Higher brake thermal efficiency with notable reduction in unburned hydrocarbon and smoke was seen with elevated levels of carbon-monoxide and oxides of nitrogen.

Combustion analysis of modified light duty diesel engine under high pressure split injections with cooled EGR

The aim of the present research work is to study the combustion phenomenon in modified light duty diesel engine to run on Common rail direct injection (CRDI) system under cooled exhaust gas recirculation (EGR). The test engine is single cylinder 3.7 kW@1500 rpm direct injection diesel engine capable of injecting high pressure fuel for both retarded and split injections. The engine is fitted with separate electronic variable timing fuel injection kit instead of conventional fuel supply system. Retarded injection consists of single injection at 11° before top dead centre (BTDC) and split injection consists of both pilot injection at 54°BTDC of 10% mass share and main injection at 11°BTDC of 90% mass share. Diesel is injected directly in to the engine cylinder for both retarded and split injections at pressures of 200,230,250,300 and 350 bar respectively. Cooled EGR is circulated along with intake air for flow rates of 5% and 10% (wt/wt) basis. The experimental set up is capable of delivering precise control of fuel and EGR flow rates at all operating conditions. Test results show that there is trade-off exists between retarded and split injections at 350 bar injection pressure at full load conditions. Retarded injection has 34% brake thermal efficiency while split injection exhibits only 32.1% for 5% EGR flow rates. But higher EGR flow rates of 10% both retarded and split injection has nearly same brake thermal efficiency of 30.1%. Split injection reduced the combustion duration, ignition delay and exhaust gas temperatures for higher EGR flow rates compared to single retarded injection.

Prechamber optimal selection for a two stage turbulent jet ignition type combustion system in CNG-fuelled engine

Searching for further reduction of fuel consumption simultaneously with the reduction of toxic compounds emission new systems for lean-mixture combustion for SI engines are being discussed by many manufacturers. Within the European GasOn-Project (Gas Only Internal Combustion Engines) the two-stage combustion and Turbulent Jet Ignition concept for CNG-fuelled high speed engine has been proposed and thoroughly investigated where the reduction of gas consumption and increasing of engine efficiency together with the reduction of emission, especially CO2 was expected. In the investigated cases the lean-burn combustion process was conducted with selection of the most effective pre-combustion chamber. The experimental investigations have been performed on single-cylinder AVL5804 research engine, which has been modified to SI and CNG fuelling. For the analysis of the thermodynamic, operational and emission indexes very advanced equipment has been applied. Based on the measuring results achieved for different pre-chamber config-urations the extended methodology of polioptimization by pre-chamber selection and the shape of main chamber in the piston crown for proposed combustion system has been described and discussed. The results of the three versions of the optimization methods have been comparatively summarized in conclusions.

Techno-economic assessment of coconut biodiesel as a potential alternative fuel for compression ignition engines

Over the past years, there were dramatic improvements in identifying and assessing various feedstocks for the production of biodiesel fuels. To promote a particular feedstock as a renewable source of energy, it is important to analyze their energy, economic, and engine performance characteristics. The current work attempts to evaluate the net energy and economic indices for both fossil diesel and coconut-blended diesel (B20) considering the diesel consumption by the Indian railways. Further, we present the experimental results of a multi-cylinder diesel engine operated with neat coconut biodiesel (B100) and fossil diesel at various load and speed conditions. The engine experiments reveal that the coconut biodiesel exhibits leaner combustion and shorter ignition delay than fossil diesel. Lower amount of carbon monoxide, hydrocarbon, and smoke emission is observed in the case of coconut biodiesel, with higher levels of nitric oxide (14%) and fuel consumption than diesel. The coefficient of variation in indicated mean effective pressure is within the range of better driveability zone for both the fuels at all test conditions. Overall the engine performance, emission and combustion results with neat coconut biodiesel are favorable with a penalty in NO emission at high load conditions. The techno-economical study highlights higher production cost per liter of B20 than the cost of fossil diesel. However, the net energy ratio (NER) for B20 is 1.021, favoring higher output than diesel and thus lowers the dependency on crude oil.

Perspective on Low-Temperature Combustion Applied to the Strategies of NOx Emission Reduction

Compression ignition engine and PPCI-Partially Premixed Combustion Ignition, in which part of the fuel is sprayed on the fill line and the remainder is directly sprayed in the cylinder, bringing the advantages of both gasoline engine (fuel blends well with air) and diesel engine (compressed by compression). At the same time, it is possible to control the burning time of the mixture and the engine is stable and continuous thanks to the second fuel injection directly in the combustion chamber. This new method of forming mixtures and fire concepts in engines can solve both the problem of toxic combustion and emissions on internal combustion engines as well as energy security due to the use of various types. renewable fuel.

Perspective on Low-Temperature Combustion Applied to the Strategies of NOx Emission Reduction

Compression ignition engine and PPCI-Partially Premixed Combustion Ignition, in which part of the fuel is sprayed on the fill line and the remainder is directly sprayed in the cylinder, bringing the advantages of both gasoline engine (fuel blends well with air) and diesel engine (compressed by compression). At the same time, it is possible to control the burning time of the mixture and the engine is stable and continuous thanks to the second fuel injection directly in the combustion chamber. This new method of forming mixtures and fire concepts in engines can solve both the problem of toxic combustion and emissions on internal combustion engines as well as energy security due to the use of various types. renewable fuel.

Ion chemistry in premixed rich methane flames

External electric field and plasma assisted combustion show great potential for combustion enhancement, e.g., emission and ignition control. To understand soot suppression by external electric fields and flame ignition in spark ignition engines, flame ion chemistry needs to be investigated and developed. In this work, comprehensive and systematic investigations of neutral and ion chemistry are conducted in premixed rich methane flames. Cations are measured by quadrupole molecular beam mass spectrometry (MBMS), and neutrals are measured by synchrotron vacuum ultra violet photoionization time of flight MBMS (SVUV-PI-TOF-MBMS). The molecular formula and dominant isomers of various measured cations are identified based on literature survey and quantum chemistry calculations. Experimentally, we found that H3O+ is the dominant cation in slightly rich flame (ϕ=1.5), but C3H3+ is the most significant in very rich flames (ϕ=1.8 and 2.0). An updated ion chemistry model is proposed and used to explain the effects of changing equivalence ratio. To further verify key ion-neutral reaction pathways, measured neutral profiles are compared with cation profiles experimentally. Detailed cation and neutral measurements and numerical simulations by this work help to understand and develop ion chemistry models. Deficiencies in our current understanding of ion chemistry are also highlighted to motivate further research.

Experimental Analysis of Partially Premixed Charge in a Diesel Engine with Jatropha Oil Methyl Ester and Diesel Blends

Homogeneous charge compression ignition (HCCI) is an alterna -tive combustion process which received considerable interest to meetthe stringent emission norms. One such technology developed is par -tially premixed charge compression ignition (PCCI) combustion modea variant of HCCI combustion mode. In this work an attempt has beenmade to experimentally analyze the performance and emission char-acteristics with Premixed Charge Compression Ignition (PCCI) modeassisted with pilot injection. Experiments were conducted in a modifiedsingle cylinder water-cooled diesel engine employing a conceptual sys -tem known as transient state fuel induction with different modes suchas diesel and biodiesel conventional mode, diesel PCCI–diesel, biodieselPCCI-diesel and biodiesel PCCI-biodiesel modes. In the present work,diesel and jatropha methyl ester was used premixed fuel along with con-ventional injection of either diesel or 20% jatropha oil methyl ester blendwith diesel. The results indicate that brake thermal efficiency decreasesmarginally as the methyl ester in the conventional and PCCI modes andHC, CO emissions are higher and soot levels are lower in the case ofbiodiesel PCCI-biodiesel mode.

Theoretical and numerical study on ignition behaviour of coal dust layers on a hot surface with corrected kinetic parameters.

Industrial fires and explosions initiating from self-ignition of combustible porous dust deposits represent a serious hazard for human beings, environment and industry. Understanding the fundamental basis of combustible dust ignition behaviours at different geometries is of importance to prevent and mitigate the accidental risks. A correlation of self-ignition temperatures (SITs) measured by hot-oven tests and minimum ignition temperatures of dust layers (MITLs) determined by hot-plate tests has been established previously. However, this analogy approach based on Frank-Kamenetzkii model is limited by ignoring the influence of oxygen diffusion. In this work, an improved method is developed by implementing a correction factor for the pre-exponential factor caused by the boundary geometry. This method is testified by comparing with experimental data, previous analogy method and numerical simulation. Results show that our proposed method performs a better predictability of MITLs and simplicity. The improved analogy method indicates that the different boundary geometries of a dust deposit significantly impact the apparent pre-exponential factor, while have an ignorable influence on the activation energy, which is also verified by numerical investigations. Furthermore, the numerical model with the corrected kinetic parameters provides a satisfactory explanation compared with experimental observations regarding to temperature and concentration evolutions of dust layers.

Empirical modelling of oxidation behaviours of coals stored under different conditions

ABSTRACTIn this study, oxidation behaviours of lignite samples stored under different conditions (deep freezer;-25°C, nitrogen tank; 18°C and oven; 30°C) for 16 weeks were investigated. Therefore; oxygen consumption rates of the coal having two size fractions (74 μm and 500 μm) and activation energies were calculated by oxygen analyser and TG/DTG analysis, respectively. In addition, the ignition temperatures and combustion risk index values of coal samples were determined by the crossing point method. As a result, the activation energies were determined to be between 28.0413 and 39.5839 kJ/mol. It was also determined that the consumption of oxygen increased after the temperature of the coal reaching 90°C. At the beginning of the storage period, lignite samples with a fine particle size in the ‘medium risk’ class in terms of the propensity to spontaneous combustion were included in the ‘high risk’ class at the end of the process. Finally, the relationship among all the obtained experimental results was outlined for the first time by creating a numerical model through the design of experiment (DOE) and it was seen that the coal samples stored in the deep freezer had advantages in terms of oxidation behaviour compared to the other two storage conditions.

Modeling of a Dielectric-Barrier Discharge-Based Cold Plasma Combustion Ignition System

We present a computational modeling study of plasma phenomena in a dielectric-barrier discharge (DBD) for automotive combustion ignition applications. The study was performed using a self-consistent, two-temperature plasma model with finite-rate plasma chemical kinetics for methane-air combustion mixture. The structure of a DBD discharge and the yield of active combustion enhancing radicals from the discharge is quantified for positive and negative pulsing, and a comparison is made with a single electrode corona discharge. The DBD plasma develops as a streamer discharge with individual streamers preferentially emerging from sharp features on the bare electrode of DBD which quickly propagates to the opposite dielectric surface where it is quenched. The dielectric barrier therefore self-limits the discharge resulting in a total radical yield that saturates in time. The corona on the other hand provides a radical yield that can continuously increase in time. The negative polarity pulsing of the DBD results in a more intense plasma with a higher radical yield compared to a positive polarity pulse. Simulations are also performed for a long 1-μs duration afterglow period once the active pulse is terminated. The active combustion enhancing radicals are found to remain relatively stable in density over this duration, indicating that ~100-kHz pulse repetition rates can sustain or even gradually increase the radical densities over long durations of transient time.

Strength Analysis of the CNG Direct Injector for the Combustion Ignition Engine in Real Driving Conditions

The paper presents the results of strength test simulations of the CNG injector structure for direct injection of compression-ignition engines. This article is a continuation of the works presented in paper [1]. Life cycles estimation of particular parts of the injector were calculated using the Kocańda relation. The simulation tests of injector strength carried out earlier have allowed us to determine the stress concentration points. On the basis of NEDC driving tests carried out in three different cars, engine load histograms were made for subsequent runs and an average load profile was determined. For the points most exposed to damage,i.e.the needle and injector housing, the stress curve was generated as a function of time. This dependence was the base for fatigue calculations with the use of MatLab program in order to calculate the limit number of repetitions for a given injector element. All the calculation works have served to determine the maximum number of work cycles of a given injector design.

Fully coupled modeling of nanosecond pulsed plasma assisted combustion ignition

A coupled 2D computational model of nanosecond pulsed plasma induced flame ignition and combustion for a lean H2–air mixture (dry air) in a high pressure environment is discussed. The model provides a full fidelity description of plasma formation, combustion ignition, and flame development. We study the effects of three important plasma properties that influence combustion ignition and flame propagation, namely (a) plasma gas temperature, (b) plasma produced primary combustion radicals O, OH and H densities, and (c) plasma generated charged and electronically excited radical densities. Preliminary 0D studies indicate that plasma generated trace quantities of O, OH and H radicals drastically reduce the ignition delay of the H2–air mixture and become especially important for high pressure lean conditions. Multi-dimensional simulations are performed for a lean H2–air mixture () at 3.3 atm and an initial temperature of 1000 K. The plasma is accompanied by fast gas heating due to N2 metastable quenching that results in uniform volumetric heating in the interelectrode gap. The spatial extent of the high temperature region generated by the plasma is a key parameter in influencing ignition; a larger high temperature region being more effective at initiating combustion ignition. Plasma generation of even trace quantities (~0.1%) of primary combustion radicals, along with plasma gas heating, results in a further fifteen-fold reduction in the ignition delay. The radical densities alone did not ignite the H2–air mixture. The generation of other plasma specific species results only in a slight ~10% improvement in the ignition delay characteristics over the effect of primary combustion radicals, with the slow decaying ions () and oxygen metastable species () primarily contributing to combustion enhancement. These species influence the ignition delay, directly by power deposition due to quenching, attachment and recombination reactions, and indirectly by enhancing production of primary combustion radicals.

A numerical investigation of the combustion kinetics of reactivity controlled compression ignition (RCCI) combustion in an optical engine

This work numerically investigates the detailed combustion kinetics occurring in an optical, reactivity controlled compression ignition (RCCI) engine. Experimental data from the engine combustion network (ECN) relating to spray H and optical RCCI engine spray/combustion were used for model validation. It was found that the RCCI combustion ignition occurred in the squish, bowl rim edge, and downstream of the spray periphery. To provide insight into key reaction pathways, an in-cylinder reaction pathway analysis method was used, and four characteristic RCCI combustion features were selected: (1) initial low temperature heat release (LTHR) from the high-reactivity fuel (n-heptane) on the spray periphery; (2) intense LTHR, where both iso-octane and n-heptane were converted to intermediates (e.g., CH2O) through oxygen-related reactions; (3) early stage high temperature heat release (HTHR) with CH2O as the core source species; (4) and intense HTHR, characterized by a substantial energy release. Further analysis of the reactive combustion surfaces demonstrated that the interior flame structure was controlled by OH-CO-O2 combustion kinetics and the exterior was controlled by CH2O-HCO (formyl radical) combustion kinetics. In addition, surrounding the reactive surfaces, iso-octane was consumed primarily through decomposition reactions, forming CH2O, which further fueled the following high temperature combustion.

Effect of Airflow Temperature on the Formation of Initial Flame Kernel and the Propagation Characteristics of Flame

Using liquid RP-3 aviation kerosene as the fuel to study, the effect of airflow temperature on the formation of initial flame kernel during the ignition of spray combustion and on the propagation characteristics of flame was investigated. Combining high-speed camera and dynamic temperature acquisitions at the outlet of combustor, the internal triggering mode was used under a constant fuel flow rate and airflow velocity. This combined system simultaneously recorded the formation of initial flame kernel, flame propagation, and outlet temperature variation of combustor under different airflow temperatures. MATLAB software was used to obtain the reaction zones at different moments and to analyze the effects of airflow temperature on morphological characteristics such as flame area, perimeter-to-area ratio, maximum length-to-height ratio, equivalent mean length-to-height ratio, mass center, and centroid. According to the growth rate in flame area, the ignition process can be divided into three stages: formation of flame kernel, rapid development of flame, and stable development of flame. Airflow temperature not only affects the formation time of flame kernel but also affects the growth rate of flame area. During the development of flame, the movements of mass center and centroid are irregular, and their positions do not coincide with each other. However, the overall moving trends are consistent. With the increase of the airflow temperature, the position, where the flame kernel is gradually formed, moves closer to the center of the end face of spark plug. The force of airflow on flame is the main factor that increases the flame area and heat-release rate. Therefore, the folds around the flame edge mainly result from the stretching under the action of airflow. With the increase in airflow temperature, the heat release of the initial flame kernel increases, and the ratio of perimeter to area as a characterization parameter increases by 8%, 86%, and 33%, respectively. In addition, the maximum outlet temperature rise increased by about 53%, 73.5%, and 0.65%, respectively. Meanwhile, the maximum rate of temperature rise increased by about 42.8%, 57%, and 5.1%, respectively.