Development and validation of an n-dodecane skeletal mechanism for spray combustion applications

n-Dodecane is a promising surrogate fuel for diesel engine study because its physicochemical properties are similar to those of the practical diesel fuels. In the present study, a skeletal mechanism for n-dodecane with 105 species and 420 reactions was developed for spray combustion simulations. The reduction starts from the most recent detailed mechanism for n-alkanes consisting of 2755 species and 11,173 reactions developed by the Lawrence Livermore National Laboratory. An algorithm combining direct relation graph with expert knowledge (DRGX) and sensitivity analysis was employed for the present skeletal reduction. The skeletal mechanism was first extensively validated in 0-D and 1-D combustion systems, including auto-ignition, jet stirred reactor (JSR), laminar premixed flame and counter flow diffusion flame. Then it was coupled with well-established spray models and further validated in 3-D turbulent spray combustion simulations under engine-like conditions. These simulations were compared with the recent experiments with n-dodecane as a surrogate for diesel fuels. It can be seen that combustion characteristics such as ignition delay and flame lift-off length were well captured by the skeletal mechanism, particularly under conditions with high ambient temperatures. Simulations also captured the transient flame development phenomenon fairly well. The results further show that ignition delay may not be the only factor controlling the stabilisation of the present flames since a good match in ignition delay does not necessarily result in improved flame lift-off length prediction.     

Development of a reduced biodiesel surrogate model for compression ignition engine modeling

Methylbutanoate (MB), a C₄ methyl ester, represents the simplest surrogate that captures the chemical effects of the ester moiety in biodiesel and biodiesel surrogates. An updated chemical kinetic model has been developed to characterize the ignition and flame characteristics of MB. The mechanistic elements within this model that relate to the MB and smaller ester/oxygenate sub-mechanisms are drawn from the prototypical Fisher et al. model and from more recent theory and modeling efforts. The MB model development which is based on an iterative procedure involving global sensitivity analyses to identify elementary reactions that govern ignition and subsequent high level ab initio based theoretical updates to these reaction rates are presented. The MB model makes reasonable predictions of ignition delays and laminar flame speeds.The C₅–C₇ submechanisms from the LLNL n-heptane (NH) model were merged with the present MB model to obtain a detailed chemical kinetics model for a surrogate blend representing biodiesel. The detailed MB-NH model (661 species) was reduced using graph based techniques. The robust reduction techniques employed result in a reduced model (145 species) that is in good agreement with the detailed model over a wide range of conditions. 3-D compression ignition (CI) engine simulations utilizing this reduced chemistry model for MB-NH blends as a surrogate for biodiesel show good agreement with the experimental data suggesting the utility of this model for predictions of combustion and emission characteristics of biodiesel in realistic CI engine simulations.     

适用于HCCI燃烧的PRF化学动力学骨架机理

本文构建了一个适用于HCCI燃烧的PRF化学反应动力学骨架机理。该机理包含40种组分和65个反应。通过与激波管、喷射搅拌反应器、流动反应器和HCCI发动机的实验数据对比表明,新机理适用于多种反应器,可以较准确地计算着火点及关键组分的演变规律,并且在不同的温度、压力和当量比下具有较好的性能。在HCCI发动机的单区模型计算中,对于燃料PRF 91.8和PRF 70,骨架机理计算结果与Curran等人的详细机理计算结果基本相同。     

Experimental and kinetic modeling studies on the auto-ignition of methyl crotonate at high pressures and intermediate temperatures

Biofuels, including biodiesel have the potential to partially replace the conventional diesel fuels for low-temperature combustion engine applications to reduce the CO₂ emission. Due to the long chain lengths and high molecular weights of the biodiesel components, it is quite challenging to study the biodiesel combustion experimentally and computationally. Methyl crotonate, a short unsaturated fatty acid methyl ester (FAME) is chosen for this chemical kinetic study as it is considered as a model biodiesel fuel. Auto-ignition experiments were performed in a rapid compression machine (RCM) at pressures of 20 and 40 bar under diluted conditions over a temperature range between 900 and 1074 K, and at different equivalence ratios (? = 0.25, 0.5 and 1.0). A chemical kinetic mechanism is chosen from literature (Gaïl et al. 2008) and is modified to incorporate the low-temperature pathways. The mechanism is validated against existing shock tube data (Bennadji et al. 2009) and the present RCM data. The updated mechanism shows satisfactory agreement with the experimental data with significant improvements in low-temperature ignition behavior. The key reactions at various combustion conditions and the improved reactivity of the modified mechanism are analyzed by performing sensitivity and path flux analysis. This study depicts the importance of low-temperature pathways in predicting the ignition behavior of methyl crotonate at intermediate and low temperatures.     

Ignition delay of fatty acid methyl ester fuel droplets: Microgravity experiments and detailed numerical modeling

Recent optical engine studies have linked increases in NO_x emissions from fatty acid methyl ester combustion to differences in the premixed autoignition zone of the diesel fuel jet. In this study, ignition of single, isolated liquid droplets in quiescent, high temperature air was considered as a means of gaining insight into the transient, partially premixed ignition conditions that exist in the autoignition zone of a fatty acid methyl ester fuel jet. Normal gravity and microgravity (10⁻⁴ m/s²) droplet ignition delay experiments were conducted by use of a variety of neat methyl esters and commercial soy methyl ester. Droplet ignition experiments were chosen because spherically symmetric droplet combustion represents the simplest two-phase, time-dependent chemically reacting flow system permitting a numerical solution with complex physical submodels. To create spherically symmetric conditions for direct comparison with a detailed numerical model, experiments were conducted in microgravity by use of a 1.1 s drop tower. In the experiments, droplets were grown and deployed onto 14 μm silicon carbide fibers and injected into a tube furnace containing atmospheric pressure air at temperatures up to 1300 K. The ignition event was characterized by measurement of UV emission from hydroxyl radical (OH*) chemiluminescence. The experimental results were compared against predictions from a time-dependent, spherically symmetric droplet combustion simulation with detailed gas phase chemical kinetics, spectrally resolved radiative heat transfer and multi-component transport. By use of a skeletal chemical kinetic mechanism (125 species, 713 reactions), the computed ignition delay period for methyl decanoate (C₁₁H₂₂O₂) showed excellent agreement with experimental results at furnace temperatures greater than 1200 K.     

正丁烷燃料中低温氧化的骨架反应机理

本文基于Healy等人建立的正丁烷详细反应机理(230个组分,1328个反应),采用直接关系图法,反应路径分析以及敏感性分析相结合的方法,构建了一个包含83个组分,397个反应的中低温反应动力学骨架模型。路径分析发现,在低温反应中,正丁烷氧化着火主要受链传播反应中的放热循环控制。而在中温反应中,正丁烷及其下游产物正丁基的裂解反应变得重要,大分子裂解后的小分子氧化加快反应进程。本文骨架模型在温度范围550~1050 K、压力范围0.1~3MPa、当量比范围0.5~2.0条件下对着火延迟时间、层流火焰速度、温度以及重要组分浓度分布的预测均与详细机理保持很好的一致性,同时与文献中快压机、定容燃烧弹和搅拌射流反应器的实验结果也吻合较好。     

Modelling biodiesel–diesel spray combustion using multicomponent vaporization coupled with detailed fuel chemistry and soot models

A multicomponent vaporization model is integrated with detailed fuel chemistry and soot models for simulating biodiesel–diesel spray combustion. Biodiesel, a fuel mixture comprised of fatty-acid methyl esters, is an attractive alternative to diesel fuel for use in compression-ignition engines. Accurately modelling of the spray, vaporization, and combustion of the fuel mixture is critical to predicting engine performance using biodiesel. In this study, a discrete-component vaporization model was developed to simulate the vaporization of biodiesel drops. The model can predict differences in the vaporization rates of different fuel components. The model was validated by use of experimental data of the measured biodiesel drop size history and spray penetration data obtained from a constant-volume chamber. Gas phase chemical reactions were simulated using a detailed reaction mechanism that also includes PAH reactions leading to the production of soot precursors. A phenomenological multi-step soot model was utilized to predict soot emissions from biodiesel–diesel combustion. The soot model considered various steps of soot formation and destruction, such as soot inception, surface growth, coagulation, and PAH condensation, as well as oxidation by oxygen and hydroxyl-containing molecules. The overall numerical model was validated with experimental data on flame structure and soot distributions obtained from a constant-volume chamber. The model was also applied to predict combustion, soot and NOx emissions from a diesel engine using different biodiesel–diesel blends. The engine simulation results were further analysed to determine the soot emissions characteristics by use of biodiesel–diesel fuels.     

Acceleration of the chemistry solver for modeling DI engine combustion using dynamic adaptive chemistry (DAC) schemes

Acceleration of the chemistry solver for engine combustion is of much interest due to the fact that in practical engine simulations extensive computational time is spent solving the fuel oxidation and emission formation chemistry. A dynamic adaptive chemistry (DAC) scheme based on a directed relation graph error propagation (DRGEP) method has been applied to study homogeneous charge compression ignition (HCCI) engine combustion with detailed chemistry (over 500 species) previously using an R-value-based breadth-first search (RBFS) algorithm, which significantly reduced computational times (by as much as 30-fold). The present paper extends the use of this on-the-fly kinetic mechanism reduction scheme to model combustion in direct-injection (DI) engines. It was found that the DAC scheme becomes less efficient when applied to DI engine simulations using a kinetic mechanism of relatively small size and the accuracy of the original DAC scheme decreases for conventional non-premixed combustion engine. The present study also focuses on determination of search-initiating species, involvement of the NO_x chemistry, selection of a proper error tolerance, as well as treatment of the interaction of chemical heat release and the fuel spray. Both the DAC schemes were integrated into the ERC KIVA-3v2 code, and simulations were conducted to compare the two schemes. In general, the present DAC scheme has better efficiency and similar accuracy compared to the previous DAC scheme. The efficiency depends on the size of the chemical kinetics mechanism used and the engine operating conditions. For cases using a small n-heptane kinetic mechanism of 34 species, 30% of the computational time is saved, and 50% for a larger n-heptane kinetic mechanism of 61 species. The paper also demonstrates that by combining the present DAC scheme with an adaptive multi-grid chemistry (AMC) solver, it is feasible to simulate a direct-injection engine using a detailed n-heptane mechanism with 543 species with practical computer time.     

Development of a reduced chemical kinetic mechanism for a gasoline surrogate for gasoline HCCI combustion

A reduced chemical kinetic mechanism consisting of 48 species and 67 reactions is developed and validated for a gasoline surrogate fuel. The surrogate fuel is modeled as a blend of iso-octane, n-heptane, and toluene. The mechanism reduction is performed using sensitivity analysis, investigation of species concentrations, and consideration of the main reaction path. Comparison between ignition delay times calculated using the proposed mechanism and those obtained from shock tube data show that the reduced mechanism can predict delay times with good accuracy at temperatures above 1000 K. The mechanism can also predict the two-stage ignition at the moment of ignition. A rapid compression machine (RCM) is designed to measure ignition delay times of gasoline and gasoline surrogates at temperatures between 890 and 1000 K. Our experimental results suggest that a new gasoline surrogate that has a different mixture ratio than previously defined surrogates is the most similar to gasoline. In addition, the reduced mechanism is validated for the RCM experimental conditions using CFD simulations.     

Experimental counterflow ignition temperatures and reaction mechanisms of 1,3-butadiene

The ignition temperatures of nitrogen-diluted 1,3-butadiene by heated air in counterflow were experimentally determined for pressures up to 5 atmospheres and pressure-weighted strain rates from 100 to 250 s⁻¹. The experimental data were compared with computational results using the mechanism of Laskin et al. [A. Laskin, H. Wang and C.K. Law, Int. J. Chem. Kinet. 32 (10) (2000) 589-614], showing that while the overall prediction is approximately within the experimental uncertainty, the mechanism over-predicts ignition temperature by about 25-40 K, with the differences becoming larger at high pressure/low temperature region. Sensitivity analyses for the near-ignition states were performed for both reactions and diffusion, which identified the importance of H₂/CO chain reactions, three 1,3-butadiene reaction pathways, and the binary diffusion between 1,3-butadiene and N₂ on ignition. The detailed mechanism, consisting of 94 species and 614 reactions, was then simplified to a skeletal mechanism consisting of 46 species and 297 reactions by using a new reduction algorithm combining directed relation graph and sensitivity analysis. The skeletal mechanism was further simplified to a 30-step reduced mechanism by using computational singular perturbation and quasi-steady-state assumptions. Both the skeletal and reduced mechanisms mimic the performance of the detailed mechanism with good accuracy in both homogeneous and heterogeneous systems.     

Generalized entropy production analysis for mechanism reduction

The paper introduces a generalized formulation for the computation of the relative contribution of each elementary reaction to the total entropy production, which has been proposed as a measure of the importance of elementary reactions and used for the reduction of detailed chemical reaction mechanisms. The reduction method is extended for the cases where the principle of detailed balance does not hold or apply, namely in the case of irreversible reactions or when the reverse rate constants are not computed via the thermodynamic equilibrium constants. Using a mechanism for n-butane consisting exclusively of reversible reactions, the new formulation is compared to the original one, and then applied for the construction of a skeletal mechanism for n-dodecane starting from a detailed mechanism which includes predominantly irreversible reactions. The skeletal scheme is found to accurately capture the ignition delay times over an extended range of pressure, initial temperature and equivalence ratio, the steady-state temperature as function of the residence time in a non-isothermal adiabatic perfectly stirred reactor, and the laminar flame speed of atmospheric flames at different unburned mixture temperatures and equivalence ratios.     

Skeletal mechanism generation and analysis for n-heptane with CSP

We use a procedure based on the decomposition into fast and slow dynamical components offered by the Computational Singular Perturbation (CSP) method to generate automatically skeletal kinetic mechanisms for the simplification of the kinetics of n-heptane oxidation. The detailed mechanism of the n-heptane oxidation here considered has been proposed by Curran et al. and involves 561 species and 2538 reactions. After carrying out a critical assessment of important aspects of this procedure, we show that the comprehensive skeletal kinetic mechanisms so generated are able to reproduce the main features of n-heptane ignition at various initial pressures and temperatures and equivalence ratios. A by-product of the algorithm that generates the skeletal mechanisms is the identification of the network of important species and reactions at a given state of the kinetic system. The analysis of this network is carried out by resorting to a visual representation of the pathways at selected time instants of the ignition process. Visual inspection of the pathways enables the identification and comparison of the relevant kinetic processes as obtained at different ignition regimes. The graphs are generated by interfacing the model reduction procedure with the open-source package graphviz.     

Ignition and extinction of low molecular weight esters in nonpremixed flows

An experimental and kinetic modeling study is carried out to characterize combustion of low molecular weight esters in nonpremixed, nonuniform flows. An improved understanding of the combustion characteristics of low molecular weight esters will provide insights on combustion of high molecular weight esters and biodiesel. The fuels tested are methyl butanoate, methyl crotonate, ethyl propionate, biodiesel, and diesel. Two types of configuration – the condensed fuel configuration and the prevaporized fuel configuration – are employed. The condensed fuel configuration is particularly useful for studies on those liquid fuels that have high boiling points, for example biodiesel and diesel, where prevaporization, without thermal breakdown of the fuel, is difficult to achieve. In the condensed fuel configuration, an oxidizer, made up of a mixture of oxygen and nitrogen, flows over the vaporizing surface of a pool of liquid fuel. A stagnation-point boundary layer flow is established over the surface of the liquid pool. The flame is stabilized in the boundary layer. In the prevaporized fuel configuration, the flame is established in the mixing layer formed between two streams. One stream is a mixture of oxygen and nitrogen and the other is a mixture of prevaporized fuel and nitrogen. Critical conditions of extinction and ignition are measured. The results show that the critical conditions of extinction of diesel and biodiesel are nearly the same. Experimental data show that in general flames burning the esters are more difficult to extinguish in comparison to those for biodiesel. At the same value of a characteristic flow time, the ignition temperature for biodiesel is lower than that for diesel. The ignition temperatures for biodiesel are lower than those for the methyl esters tested here. Critical conditions of extinction and ignition for methyl butanoate were calculated using a detailed chemical kinetic mechanism. The results agreed well with the experimental data. The asymptotic structure of a methyl butanoate flame is found to be similar to that for many hydrocarbon flames. This will facilitate analytical modeling, of structures of ester flames, using rate-ratio asymptotic techniques, developed previously for hydrocarbon flames.     

Skeletal mechanism generation with CSP and validation for premixed n-heptane flames

An automated procedure has been previously developed to generate simplified skeletal reaction mechanisms for the combustion of n-heptane/air mixtures at equivalence ratios between 0.5 and 2.0 and different pressures. The algorithm is based on a Computational Singular Perturbation (CSP)-generated database of importance indices computed from homogeneous n-heptane/air ignition solutions. In this paper, we examine the accuracy of these simplified mechanisms when they are used for modeling laminar n-heptane/air premixed flames. The objective is to evaluate the accuracy of the simplified models when transport processes lead to local mixture compositions that are not necessarily part of the comprehensive homogeneous ignition databases. The detailed mechanism was developed by Curran et al. and involves 560 species and 2538 reactions. The smallest skeletal mechanism considered consists of 66 species and 326 reactions. We show that these skeletal mechanisms yield good agreement with the detailed model for premixed n-heptane flames, over a wide range of equivalence ratios and pressures, for global flame properties. They also exhibit good accuracy in predicting certain elements of internal flame structure, especially the profiles of temperature and major chemical species. On the other hand, we find larger errors in the concentrations of many minor/radical species, particularly in the region where low-temperature chemistry plays a significant role. We also observe that the low-temperature chemistry of n-heptane can play an important role at very lean or very rich mixtures, reaching these limits first at high pressure. This has implications to numerical simulations of non-premixed flames where these lean and rich regions occur naturally.     

An improved path flux analysis with multi generations method for mechanism reduction

An improved path flux analysis with a multi generations (IMPFA) method is proposed to eliminate unimportant species and reactions, and to generate skeletal mechanisms. The production and consumption path fluxes of each species at multiple reaction paths are calculated and analysed to identify the importance of the species and of the elementary reactions. On the basis of the indexes of each reaction path of the first, second, and third generations, the improved path flux analysis with two generations (IMPFA2) and improved path flux analysis with three generations (IMPFA3) are used to generate skeletal mechanisms that contain different numbers of species. The skeletal mechanisms are validated in the case of homogeneous autoignition and perfectly stirred reactor of methane and n-decane/air mixtures. Simulation results of the skeletal mechanisms generated by IMPFA2 and IMPFA3 are compared with those obtained by path flux analysis (PFA) with two and three generations, respectively. The comparisons of ignition delay times, final temperatures, and temperature dependence on flow residence time show that the skeletal mechanisms generated by the present IMPFA method are more accurate than those obtained by the PFA method, with almost the same number of species under a range of initial conditions. By considering the accuracy and computational efficiency, when using the IMPFA (or PFA) method, three generations may be the best choice for the reduction of large-scale detailed chemistry.     

Theoretical studies on the hydrogen abstraction reactions of methyl esters with HO2 radical and the following β‐scission reactions

Unsaturated fatty acid methyl esters are ubiquitous in biodiesel fuels. The C = C double bond greatly affects the combustion characteristics of biodiesel, especially its ignition behavior at low temperatures. In this work, we report detailed theoretical study on the mechanism and kinetics of the hydrogen abstraction reactions of linear unsaturated C6 methyl esters with hydroperoxy radical (HO₂), which play a critical role in the low‐temperature combustion of biodiesel. Reaction profiles are obtained via intrinsic reaction coordinate (IRC) analysis including the formation of reactant complexes and product complexes at the entrance and exit channels, respectively. The potential energy surfaces are explored at the CBS‐QB3 level. The following β‐scission reactions of the forming radicals are also investigated at the same level of theory. The high‐pressure limit rate constants for all the reactions in the temperature range from 500 to 2000 K are calculated via conventional transition‐state theory with quantum tunneling effect and fitted to the modified Arrhenius expression.     

Systematic analysis and reduction of combustion mechanisms for ignition of multi-component kerosene surrogate

Currently, most detailed chemical kinetic mechanisms for combustion are still not comprehensive enough and update of key reaction rate is still required to improve the combustion mechanisms. The development of systematic mechanism reduction methods have made significant progress, and have greatly facilitated analysis of the reaction mechanisms and identification of important species and key reactions. In the present work, time-integrated element flux analysis is employed to analyze a skeletal combustion mechanism of a tri-component kerosene surrogate mixture, consisting of n-decane, n-propylcyclohexane, and n-propylbenzene. The results of element flux analysis indicate that major reaction pathways for each component in the surrogate model are captured by the skeletal mechanism compared with the detailed mechanism. After that, sensitivity analysis (SA) and chemical explosive mode analysis (CEMA) are conducted to identify the dominant ignition chemistry. The SA and CEMA results demonstrate that the ignition of n-decane and n-propylcyclohexane is sensitive only to the oxidation chemistry of H₂/CO and C1–C4 small hydrocarbons, while the ignition of n-propylbenzene is very sensitive to the initial reactions of n-propylbenzene and related aromatic intermediates. This demonstrates that the hierarchic structure should be maintained in the reduction of detailed mechanism of substituted aromatic fuels. The skeletal mechanism is further reduced by combining the computational singular perturbation (CSP) method and quasi steady state approximation (QSSA). A 34-species global reduced mechanism is obtained and validated over a wide range of parameters for ignition.     

Theoretical analysis on the exergy destruction mechanisms and reduction under LTC relevant conditions

Low temperature combustion (LTC) is a potential thermodynamic pathway to maximize the thermal efficiency of internal combustion (IC) engines. However, high exergy loss is also observed within this combustion concept. The present study focuses on the homogeneous combustion process and examines the detailed exergy destruction mechanisms under representative LTC engine conditions. By varying both equivalence ratios (φ) and temperatures (T) at initial pressure of 50?bar, it is found that the decreased total exergy destruction fraction (f_ED) with increasing initial temperature mainly results from the decreased exergy destruction in the high temperature heat release stage, while using rich mixture can significantly reduce the f_ED in the ignition delay stage, which is dominated by the reactions involving large molecules (C7 species). Reaction pathway analysis reveals that the detailed exergy destruction sources are significantly affected by the reaction pathways. Furthermore, a qualitative exergy loss φ-T map was created to illustrate the exergy loss reduction potential. It is concluded that the combustion pathway that reforming the rich fuel/air mixtures before ignition followed by the low temperature combustion of lean reforming products offers the potential to simultaneously reduce exergy destruction and avoid soot and NOx formation. However, the potential advantages of this exergy reduction combustion concept still require further work.     

Numerical simulation and validation of SI-CAI hybrid combustion in a CAI/HCCI gasoline engine

SI-CAI hybrid combustion, also known as spark-assisted compression ignition (SACI), is a promising concept to extend the operating range of CAI (Controlled Auto-Ignition) and achieve the smooth transition between spark ignition (SI) and CAI in the gasoline engine. In this study, a SI-CAI hybrid combustion model (HCM) has been constructed on the basis of the 3-Zones Extended Coherent Flame Model (ECFM3Z). An ignition model is included to initiate the ECFM3Z calculation and induce the flame propagation. In order to precisely depict the subsequent auto-ignition process of the unburned fuel and air mixture independently after the initiation of flame propagation, the tabulated chemistry concept is adopted to describe the auto-ignition chemistry. The methodology for extracting tabulated parameters from the chemical kinetics calculations is developed so that both cool flame reactions and main auto-ignition combustion can be well captured under a wider range of thermodynamic conditions. The SI-CAI hybrid combustion model (HCM) is then applied in the three-dimensional computational fluid dynamics (3-D CFD) engine simulation. The simulation results are compared with the experimental data obtained from a single cylinder VVA engine. The detailed analysis of the simulations demonstrates that the SI-CAI hybrid combustion process is characterised with the early flame propagation and subsequent multi-site auto-ignition around the main flame front, which is consistent with the optical results reported by other researchers. Besides, the systematic study of the in-cylinder condition reveals the influence mechanism of the early flame propagation on the subsequent auto-ignition.     

Comparative study on ethyl butanoate reactivity – Experimental investigation and kinetic modeling of the C6 ethyl ester

Ethyl butanoate is a representative for oxygenated hydrocarbons as they are discussed as future liquid fuels from sustainable production pathways. An in-depth understanding of the influence of oxygen on the reactivity of those fuel candidates is mandatory for the molecular design and their application in internal combustion engines. Towards this goal, ignition delay times for ethyl butanoate were measured at conditions relevant to internal combustion engines using a shock tube and a rapid compression machine. These experiments were conducted for stoichiometric mixtures with air-like conditions at pressures of 20, 30 and 40 bar and a total temperature range of 680–1260 K. A negative temperature coefficient regime was found where the ignition delay times increased with increasing temperatures for all covered pressures. To further understand the kinetics of ethyl butanoate and the influence of the ester functional group, a detailed kinetic mechanism was developed and validated against the measured ignition delay times. A good agreement between the measured data and the prediction by the newly developed mechanism was achieved. The findings of this work were then used to compare ethyl butanoate to di-ethyl carbonate, methyl pentanoate and n-heptane, which also show a seven-heavy-atom-membered main chain and have all been kinetically studied before. The differences between the molecular structures and their effect on the kinetic pathways was discussed to extract information for future fuel design. It was found that especially the inhibting effect of oxgen atoms on six-membered internal H-atom migration reactions has a significant impact on the fuel’s reactivity.