Methane Number Research Articles

Experimental Evaluation of the Methane Number Measurement Procedure for Gaseous Fuel Rating

Methane Number (MN) is a fuel rating technique for gaseous fuels analogous to Octane Number. This study establishes and shares a repeatable and reproducible method for MN determination of a gaseous fuel using a modified Cooperative Fuel Research Engine (CFR). Adaptations required to convert a CFR engine for use in the MN test procedure are identified. The investigation includes allowable environmental parameters and operating variation limits. An essential aspect of the MN method involves identifying and quantifying Knock Intensity (KI) during engine operation. CFR engines, originally designed for gasoline testing, come equipped with their own knock measurement systems utilizing a capacitive detonation sensor. The original system is compared with a Fast Fourier Transform (FFT) approach that uses a piezoelectric pressure transducer. Quantification of methane number requires an accurate assessment of the reference fuel blend (CH4 + H2). A comparison is carried out between dynamic blending using mass flow meters and bracketing using certified gas bottles containing various CH4/H2 blends from a gas supplier.

Experimental study of the performance of a SI-engine fueled with hydrogen-natural gas mixtures

Green hydrogen has become more attractive as a fuel for engines to reduce greenhouse gas emissions. By mixing it with natural gas (NG), the modification work on the engine can be minimized but the carbon dioxide emissions from combustion can still be decreased. In this paper, an experimental study was accomplished to investigate the performance of a spark-ignition engine fueled with hydrogen-natural gas blends by either keeping a constant ignition timing or changing it. Up to 25 mol-% hydrogen was mixed into natural gases with different compositions and the methane number and Wobbe index were calculated and compared to the requirements set by Euromot. The results show that up to 15 mol-% hydrogen can be blended into NG to meet the limits of Euromot. However, when 25 mol-% hydrogen was mixed into NG the methane number varied between 56 and 64 depending on the gas composition. This would most likely cause knock for a mixture consisting of higher hydrocarbons but during the executed tests knock was never a problem. Furthermore, it was detected that the methane number alone cannot tell the knock tendency of a gas in a certain engine and an additional condition is needed such as the hydrogen level. An adjusted ignition timing was also preferable compared to a constant one to keep the engine component temperature at a moderate level.

APPLICATION OF INSTRUMENTATION AND CONTROL SYSTEM FOR BIOGAS POWER GENERATION COMMISSIONING AT PTPN V KAMPAR PALM OIL MILL

Biogas Power Plant (PLT) from palm oil mill effluent had been commissioned by a team from the Center of Technology for the Energy Resources and Chemical Industry, Agency for the Assessment and Application of Technology (PTSEIK-BPPT). The biogas power plant is located in PTPN V Kampar, Riau Province. A PLC (Programmable Logic Controller) has been implemented to support the operation of biogas power plant. Proper sensor selection has been done for each measurement applications. A computer and mimic panel is used as an interface for the operation of PLC. The master control system communicates with the slave control systems and Human Machine Interface (HMI) by means of ethernet communication protocol. Commissioning phase is carried out for 2 hours with a load of 450 kW. Instrumentation and control system is able to measure important variables such as fluctuation in methane numbers, pressures, and biogas flow rate to check the suitability of biogas supply in accordance to gas engine specification.

Efficiency of fuel gas supply on LNG-fueled vessels

The widespread use of LNG as a fuel for marine internal combustion engines makes to pay attention to the quality of gas fuel supply systems and its specifics. The objective of this paper is to review modern gas fuel supply systems and analyze their efficiency. The goal is to determine the most important parameters of gas fuel that affect the stability of the working process of marine dual-fuel engines and ways to maintain them within the specified limits. Evaluation of the gas fuel preparation efficiency is carried out on the basis of operational data obtained on the gas carrier vessel board. Data collection is carried out under non-standard operating conditions, which makes it possible to evaluate the quality of the resulting gas fuel with a time-varying composition of the initial natural gas. To analyze the obtained data, modern software, which is used by leading developers of marine diesel engines, is used (Wartsila Methane Number Calculator, AVL BoostTM and Python 3 statistic libraries). The analysis results are approximated for gas fuel supply systems for gas-fueled vessels, but not being gas carriers. This approximation is made taking into account the design features of gas fuel supply systems, since the specificity of the design imposes certain restrictions on the applicability of the conclusions obtained as a result of the previous analysis. Also, attention is paid to the accumulation of residual heavy hydrocarbons in bunker tanks, the excess of which can adversely affect the quality of gas fuel. Since there is no universal way to solve this problem, only general assumptions about possible ways to dispose of them have been made.

Research on the new combustion chamber design to operate with low methane number fuels in an internal combustion engine with pre-chamber

Research on the new combustion chamber design to operate with low methane number fuels in an internal combustion engine with pre-chamber

CLIMATE AND ENVIRONMENTAL BACKGROUNDS OF FUEL UTILIZATION, INFLUENCING UPON ALTERATION THE EUROPEAN AND UKRAINIAN TRENDS OF GAS SUPPLY P.1 PRESENT REQUIREMENTS TO SELECTION THE GAS FUELS. THERMODYNAMIC EVALUATION THE PRINCIPAL CHARACTERISTICS OF GAS FUEL

The work examines the starting points on the formation of fuel markets in Europe within the framework of the concept of sustainable development of the countries’ economics, taking into account the main limitations, primarily the climatic and environmental consequences of fuels combustion. This approach has led in the past years to simultaneous increase in absolute volumes’ consumption of mineral (organic, carbon-rich) fuel’s flow rate and to reduction of their shares in the overall fuel balance. The relevant changes had occurred because of simultaneous production and consumption the alternative fuels, including renewable gas and energy sources. New schemes, methods and ways of fuel supply have been analyzed, including maritime transportation of liquefied fuels (liquefied natural gas LNG, liquid hydrocarbons LPG, ammonia NH3) along with creation of a modern tanker fleet with floating and land-based regasification and gas storage (FSRU) systems; systems of interconnecting the pipelines for fuel supply, including hydrogen-enriched natural gas (HENG). According to the cultivated opinion, the global warming is considered as a consequence of the carbonization of environment due to emission of C-rich combustion products (CO2) into the atmosphere. The specified contribution of CO2 to atmospheric pollution is caused by the insufficient efficiency of fuel use, for example, in heating furnaces (up to 40 % of the total amount of fuel consumed in the industry is burned in furnaces). If the emissions value of a conventional natural gas combustion systems in furnaces meets the level of emissions up to 0.45 kg СО2/kW.h, then in the case of equipping the furnace with an efficient waste gas heat recovery system, the emissions are reducing to 0.2–0.25 kg СО2/kW.h, (Wunning J.). The determinant role of the efficiency of fuel use ηf has been correlated with the scale of atmospheric pollution with greenhouse gases (CO2) emission by means of thermodynamic analysis of energy efficiency. The efficiency of fuel utilization: by enthalpy ηH and by exergy ηeff — has been computed for the cases of burning the widespread fuels and the comparative analysis has been performed. The calculations of thermal energy characteristics of the fuels have been carried out by using the original author’s methodology based upon assumption of equilibrium thermodynamics for the cases of using the widespread gas fuels within the temperature range T from the standard T0 to the theoretical combustion temperature TT. In accordance with original author’s method the most important heat engineering characteristics of the fuels have been studied by means of approaches of equilibrium thermodynamics. Higher and lower combustion heat, higher and lower Wobbe numbers, theoretical (adiabatic) combustion temperature of the widespread fuels have been determined. An influence of hydrogen content in CH4/H2 gas fuel mixtures on the mentioned properties has been determined. From the list of firing engineering characteristics, the formation of the methane number MN for different organic and alternative fuels have been considered. The accumulated numerical values of MN for the widespread types of fuels have been stated and compared. Bibl. 38, Fig. 4, Tab. 1.

Analysis of Influencing Factors and Kinetic Characteristics of Spherical Methane Hydrate Decomposition

Herein, several molecular systems are simulated by molecular dynamics to study the decomposition process and fluctuation-dissipation characteristics of spherical methane hydrates under different conditions. The spherical radius and the movement of the hydrate-liquid water interface during decomposition are measured. Different fitted formulas of the variation of methane numbers are obtained from the decomposition of spherical and bulk methane hydrates. Fluctuation-dissipation characteristics for spherical methane hydrates with different radii are analyzed, which show that increasing the scale of hydrates can increase the relaxation time and slow down the fluctuation process. The variations of the hydrogen bond and hydrogen-bond lifetime are calculated. For hydrate phase water, the peak of the hydrogen-bond lifetime lies between 8 and 10 ps. After complete decomposition, the hydrogen-bond lifetime mainly distributes in 0 and 2 ps and the peak disappears. The effects of temperature, cage occupancy, liquid phase environment, and spherical hydrate scale are explored. The decomposition activation energy for the spherical hydrate with a radius of 20 Å is calculated to be 52.23 kJ/mol. It can speed up the decomposition rate as well as the diffusion of methane and water molecules with a lower cage occupancy. For the effect of the liquid phase environment, it is found that the number of liquid water rarely affects the decomposition. However, when the Na+ and Cl- concentrations change from 0 to 10%, the decomposition time reduces from ∼511 to ∼369 ps, which indicates that there is an obviously positive impact on decomposition.

Gas Quality Impact on Gas Engine Performance: Case of an Indonesia Natural Gas Station

This research was conducted to find a correlation between changes in the variable composition of the natural gas fuel in gas engine generators, and the occurrence of a unit shutdown at a natural gas distribution facility in South Sumatra-Indonesia. The analysis is carried out by investigating the trend of changes in gas composition parameters, and simulation using the Methane Number Calculator application. The results obtained from the research results, in Changes in the composition of fuel gas cause changes in the methane number, Low Heating Value (LHV), High Heating Value (HHV), and Wobbe index (WI), which may indicate engine trouble and cause a unit shutdown. Several options of solutions can be carried out as discussions to solve problems that occur in the gas engine generator at the natural gas distribution facility

Dynamic simulation of Methane Number variations in LNG fueled vessels with periodic bunkering operations

Dynamic simulation of Methane Number variations in LNG fueled vessels with periodic bunkering operations

LNG 燃料 推進船의 燃料 品質基準에 關한 立法論적 硏究

The shipping industry, which has been using fossil fuels for a long time, has been making various efforts under the auspices of the International Maritime Organization to reduce air pollutants from ships. From January 2020, all ships engaged on international voyages must use fuel oil with a sulfur content of less than 0.5%. In order to comply with this international regulation, ships are required to install an Exhaust Gas Cleaning System, use Low-Sulfur Fuel Oil, or switch to Liquefied Natural Gas Fuelled ships. Among them, LNG, an eco-friendly fuel oil, is attracting attention as a new ship fuel. LNG fuel can reduce not only sulfur oxides but also nitrogen oxides and greenhouse gas emissions, so it is evaluated as the most commercialized marine fuel that can satisfy the currently reinforced air environment regulations. In order to revitalize the supply market for eco-friendly LNG fuel, it is most important to build a bunkering infrastructure in consideration of ship navigation routes, but the quality of the supplied fuel is also an important factor. In this study, the current international standards for ship fuel oil quality management, International Maritime Conventions, and domestic legal regulations are reviewed. Consider whether these regulations are appropriate to properly manage quality and prevent marine pollution caused by the use of LNG fuels of inappropriate quality in consideration of the characteristics of LNG fuels represented by aging effect. Through this, it recognizes the importance of LNG fuel quality management and proposes a legislative improvement proposal for LNG fuel quality management including LNG fuel delivery note containing information on methane number and fuel sample management, and providing material safety data sheet.

Impact of Hydrogen on Natural Gas Compositions to Meet Engine Gas Quality Requirements

To meet the target of reducing greenhouse gas emissions, hydrogen as a carbon-free fuel is expected to play a major role in future energy supplies. A challenge with hydrogen is its low density and volumetric energy value, meaning that large tanks are needed to store and transport it. By injecting hydrogen into the natural gas network, the transportation issue could be solved if the hydrogen–natural gas mixture satisfies the grid gas quality requirements set by legislation and standards. The end consumers usually have stricter limitations on the gas quality than the grid, where Euromot, the European association of internal combustion engine manufacturers, has specific requirements on the parameters: the methane number and Wobbe index. This paper analyses how much hydrogen can be added into the natural gas grid to fulfil Euromot’s requirements. An average gas composition was calculated based on the most common ones in Europe in 2021, and the results show that 13.4% hydrogen can be mixed with a gas consisting of 95.1% methane, 3.2% ethane, 0.7% propane, 0.3% butane, 0.3% carbon dioxide, and 0.5% nitrogen. The suggested gas composition indicates for engine manufacturers how much hydrogen can be added into the gas to be suitable for their engines.

Autoignition, knock, detonation and the octane rating of hydrogen

This paper presents an experimental and numerical study of hydrogen’s combustion, autoignition and octane rating. The experiments are conducted in a standard engine that is compliant for rating liquid fuels to the ASTM’s Research Octane Number (RON) method, with minor modifications to enable hydrogen fueling. The numerical analysis is undertaken using a combination of calibrated, two-zone combustion and kinetic modeling of the end-gas. Application of the standard RON method first shows that hydrogen has a RON of 62–64, which is significantly lower than that of standard gasolines. However, this standard RON method requires conditions that are not relevant to practical, hydrogen-fueled engines and, indeed, do not appear to feature autoignition and knock. A set of modified RON tests are therefore undertaken at more practical conditions. These indicate that hydrogen at standard knock intensity and λ=1,1.5 and 2 has a modified RON of 93.7,117 and greater than 120 respectively, spanning the range of λ that match the energy delivered by common SI engine fuels.Together, these results show that hydrogen is significantly more knock-resistant than standard gasolines when providing similar energy to the premixture. Indeed, it should have comparable knock resistance to some high-octane fuels. However, care must be taken when examining hydrogen autoignition, knock and abnormal combustion more generally. Hydrogen’s high flame speeds near stoichiometric conditions can produce high rates of pressure rise at lower compression ratios that can be mistakenly identified as autoignition, even with contemporary in-cylinder pressure measurement, while higher compression ratios near stoichiometric conditions can cause detonation. The identification and avoidance of conventional knock and other forms of abnormal combustion is therefore particularly important for hydrogen fueled engines. This also has significant implications for the development of standard test methods for determining the octane and methane numbers of hydrogen-rich fuel blends.

Properties and Analysis of Gaseous Alternative Fuels II: Fuels Based on Natural Gas and Biogas

The importance of alternative energy sources is constantly growing, especially due to the ever-increasing energy consumption of mankind and due to the effort to replace existing sources with more environmentally friendly ones. This article is another in a series of articles focused on an overview of technical requirements and testing methods for alternative gaseous, liquid, and solid fuels. This series of articles aims to provide an overview of the required properties of individual alternative fuels, the possibilities of their analysis, and the significance of individual analyzes. This article provides an overview of the technical requirements prescribed by legislation and relevant standards for automotive fuels based on natural gas (fossil methane) and biomethane. Furthermore, prescribed analytical tests are presented, which have been used to monitor the quality of these fuels. To a lesser extent, the importance of selected analytical tests is also discussed. Natural gas can be compressed or liquefied for use in automobile transport. In the first case, CNG fuel is obtained, and in the second, LNG. As a source of renewable methane or biomethane, biogas can be used, which is produced by anaerobic fermentation of agricultural waste or other raw materials in biogas plants. The obtained biogas can be used for the combined production of heat and energy. Alternatively, it can be purified into biomethane, which can be injected into the natural gas distribution network or used in automobile transport in the form of bio-CNG and bio-LNG. In general, it can be stated that the analysis of fuels based on natural gas and biomethane is well managed. Instrumental equipment and analytical methods used for natural gas analysis can be used to analyze these fuels. The properties of fuels based on natural gas and biomethane are closely related to their composition. In terms of proper operation and performance of the combustion engine, the lower heating value, Wobbe number, and methane number are critical parameters. An important parameter is also the sulfane content, increased content of which can lead to corrosion of engine components. In terms of emissions, the total sulfur content is an important parameter also. Sulfur compounds are undesirable in emissions for environmental reasons. At the same time, they are also catalytic poisons. Other critical parameters of fuels based on natural gas and bio-methane are the water content or dew point of water.

Исследование энергетических характеристик использования природного метана в газодизельном процессе ДВС

A chemmotological analysis of natural gas used as motor fuel for modern gas-diesel internal combustion engines is presented. An automated system for changing the fuel supply and the ignition timing angle is considered depending on the assessment of the energy characteristic (Wobbe number) and methane number (MH) of natural gas by measuring the physical characteristics of the gas mixture by the additivity of its composition using measurements of the content of each component in natural gas. Keywords: GAS DIESEL, CHEMICAL ANALYSIS, TESTS, LABORATORY INSTALLATION, COMBUSTIBLE MIXTURE, METHANE NUMBER, IGNITION DOSE, THERMODYNAMIC FUNDAMENTALS OF THE GAS DIESEL CYCLE, ENERGY INDICATORS

Ethane formation via catalytic low-temperature steam reforming of C3+-alkanes

The present work aims at studying low-temperature steam reforming (LTSR) of model mixtures of flare gases containing C2H6-C4H10 in methane excess over a highly dispersed Rh-based catalyst. 1 wt% Rh/Ce0.75Zr0.25O2 catalyst was prepared by sorption-hydrolytic deposition. Catalytic properties were studied in the LTSR of model fuel gas mixtures at 200–350 °C. The catalysts provided complete conversion of C2+-hydrocarbons into CH4, CO2 and H2 at 320–350 °C. The conversion of propane and heavier alkanes over Rh at low temperature (200–300 °C) allows obtaining high ethane concentrations in the products, which is not observed in the case of nickel catalysts. The influence of hydrogenolysis reaction to ethane formation is discussed. Ethane has a higher calorific value than methane and can compensate the negative effect of the product gas dilution by carbon dioxide and hydrogen that are formed in the reaction. This can be useful for adjusting the fuel properties (calorific value, Wobbe index, methane number) of the resulting gas mixtures.

Research on an internal combustion engine with an injected pre-chamber to operate with low methane number fuels for future gas flaring reduction

Flaring gas is the action of burning waste crude natural gas that is not possible to process or sell during the extraction and processing of oil and gas extraction. However, the surge of the oil and gas (O&G) fields caused an augmentation of flared gas; making society aware of its impact on the planet. To solve this problem, internal combustion engines showed clear advantages. However, there is a lack of information about how to utilize this associated petroleum gas (APG) as fuel for these engines due to its reduced methane number (MN). A methodical investigation about the optimal combustion and design needs for low MN fuels is proposed based on tests conducted in a natural gas engine with an injected pre-chamber ignition technology and a future technology that could replace flaring is proposed. Experiments conducted when using low MN gases showed different misfire limits and knocking margins. A 15% efficiency drop was obtained, however, this could be considered as a good performance as the Brake Mean Effective Pressure (BMEP) or output power reduction was 53.3%. In consequence, different engine design modifications are proposed to improve the former situation.

Phenomenological Analysis of the Combustion of Gaseous Fuels to Measure the Fuel's Energy Quality and Availability to Produce Work in Spark Ignition Engines, Part 2

Abstract A novel methodology is proposed to evaluate fuel’s performance in spark ignition (SI) engines based on the fuel’s energy quality and availability to produce work. Experiments used a diesel engine with a high compression ratio (CR), modified by SI operation, and using interchangeable pistons. The interchangeable pistons allowed for the generation of varying degrees of turbulence during combustion, ranging from middle to high turbulence. The generating efficiency (ηq), and the maximum electrical energy (EEmax) were measured at the knocking threshold (KT). A cooperative fuel research (CFR) engine operating at the KT was also used to measure the methane number (MN), and critical compression ratio (CCR) for gaseous fuels. Fuels with MNs ranging from 37 to 140 were used: two biogases, methane, propane, and five fuel blends of biogas with methane/propane and hydrogen. Results from both engines are linked at the KT to determine correlations between fuel’s physicochemical properties and the knocking phenomenon. Certain correlations between knocking and fuel properties were experimentally determined: energy density (ED), laminar flame speed (SL), adiabatic flame temperature (Tad), heat capacity ratio (γ), and hydrogen/carbon (H/C) ratio. Based on the results, a mathematical methodology for estimating EEmax and ηq in terms of ED, SL, Tad, γ, H/C, and MN is presented. These equations were derived from the classical maximum thermal efficiency for SI engines given by the Otto cycle efficiency (ηOtto). Fuels with MN > 97 got higher EEmax, and ηq than propane, and diesel fuels.

Mechanism study of natural gas pre-ignition induced by the auto-ignition of lubricating oil

The lubricating oil auto-ignition induced pre-ignition (LOAP) is the most threatening abnormal combustion in natural gas engines. To reveal the mechanisms of the occurrence and the suppressing methods of abnormal combustion in natural gas/diesel marine engines, influence mechanisms of thermodynamic condition, reagent gas composition and the volume of oil droplet on abnormal combustion were investigated by a newly developed visual rapid compression machine (RCM). Experimental results indicate that the auto-ignition of in-cylinder suspended oil droplet can cause the fuel–air pre-ignition. Furthermore, the heated burning residuals of oil droplet can glow to become the ignition source which can induce the pre-ignition. Two factors, total combustion duration and maximum pressure rise rate (PRRmax), are introduced. Shorter total combustion duration and higher PRRmax represent a stronger occurrence tendency of LOAP in the dual-fuel engine. Under the range of reagent gas composition and thermodynamic condition in the dual-fuel engine, rising equivalence ratio (ϕ) and reducing methane number (MN) of natural gas can reduce the total combustion duration by 57% and 41% respectively, and increase PRRmax by about 30 times and 1.9 times. Rising compression temperature and pressure shortens the total combustion duration by 40.7% and 40.1% respectively and increases PRRmax by about 1.3 times and 0.8 times. Reducing oil droplet volume only slightly advances its ignition moment, and has little effect on subsequent natural gas pre-ignition. Based on the result, the most influential factors on the promotion extent of pre-ignition are ranked as: ϕ, MN, temperature, pressure, droplet volume (strongest: reagent gases, moderate: thermodynamic conditions, weakest: droplet volume). Therefore, to prevent the occurrence of LOAP, the existence of in-cylinder local rich natural gas region should be avoided first. Then the high-MN natural gas ought to be applied. The compression temperature and pressure need to be reduced moderately on the premise of ensuring thermal efficiency. Moreover, the small volume oil mist should be avoided to enter into cylinder by optimizing oil injection strategies and scavenging port structures. These findings are beneficial to prevent abnormal combustions and further improve engine power performance.

Natural gas methane number and its influence on the gas engine working process efficiency

The natural gas usage as a vehicle fuel in the mining industry is one of the priority tasks of the state. The article pays special attention to the component composition of natural gas from the point of view of its thermal efficiency during combustion in the combustion chamber of a power plant on a heavy-duty vehicle in difficult quarry conditions. For this, domestic and foreign methods for determining the main indicator characterizing the knock resistance of fuel in the combustion process – the methane number – are considered. Improvement of technical and economic indicators will be carried out by changing the composition of the gas mixture based on methane to fit the design features of the gas power plant, the methane number will be the determining indicator. A theoretical analysis of the influence of the methane number on such engine parameters as the compression ratio and the maximum speed of the flame front propagation in the second phase of combustion in the engine cylinder, expressed through the angle of rotation of the crankshaft, is presented. Based on the results of theoretical and experimental studies, the dependences of the influence of the methane number on the efficiency of the working process of the engine and its external speed characteristic were obtained.

End-gas autoignition fraction and flame propagation rate in laser-ignited primary reference fuel mixtures at elevated temperature and pressure

Knock in spark-ignited (SI) engines is initiated by autoignition of the unburned gasses upstream of spark-ignited, propagating, turbulent premixed flames. Knock propensity of fuel/air mixtures is typically quantified using research octane number (RON), motor octane number (MON), or methane number (MN; for gaseous fuels), which are measured using single-cylinder, variable compression ratio engines. In this study, knock propensity of SI fuels was quantified via observations of end-gas autoignition (EGAI) in unburned gasses upstream of laser-ignited, premixed flames at elevated pressures and temperatures in a rapid compression machine. Stoichiometric primary reference fuel (PRF; n-heptane/isooctane) blends of varying reactivity (50 ≤ PRF ≤ 100) were ignited using an Nd:YAG laser over a range of temperatures and pressures, all in excess of 545 K and 16.1 bar. Laser ignition produced outwardly-propagating premixed flames. High-speed pressure measurements and schlieren images indicated the presence of EGAI. The fraction of the total heat release attributed to EGAI (i.e., EGAI fraction) varied with fuel reactivity (i.e., octane number) and the time-integrated temperature of the end-gas prior to ignition. Flame propagation rates, which were measured using schlieren images, were only weakly correlated with octane number but were affected by turbulence caused by variation in piston timing. Under conditions of low turbulence, measured flame propagation rates approached one-dimensional premixed laminar flame speed computations performed at the same conditions. Experiments were simulated with a three-dimensional CONVERGE™ model using reduced chemical kinetics (121 species, 538 reactions). The simulations accurately captured the measured flame propagation rates, as well as the variation in EGAI fraction with fuel reactivity and time-integrated end-gas temperature. The simulations also revealed low-temperature heat release as well as formaldehyde and hydrogen peroxide formation in the end-gas upstream of the propagating flame, which increased the temperature and degree of chain branching in the end-gas, ultimately leading to EGAI.