Shock Tube Ignition Research Articles

Numerical investigation on critical ignition in shock tube with controlled expansion rate

To evaluate the potential of studying the competition between chemical heat release and expansion-induced cooling in shock tube facilities, one-dimensional numerical simulations using Stanshock were performed with focus on two approaches to obtain controlled expansion rate in the post-reflected shock region. A first approach is through the utilization of driver insert, and a second approach relies on the utilization of the reflected expansion head. Auto-ignition in hydrogen-oxygen-argon mixtures in the driven section was studied. Numerical simulations for the first approach were performed for various expansion rates induced by the driver insert, for two Ar dilutions of 99 % and 95 %, and for various target temperatures in two shock tubes with different lengths. For the second approach, numerical simulations were performed for various target temperatures, and for two Ar dilutions of 95 % and 90 %. Depending on the expansion rate, either ignition or chemical quenching could be effectively observed, which is consistent with the critical decay rate concept. To further investigate the mechanisms responsible for ignition and quenching, quantitative thermo-chemical analyses were performed for quenching and successful ignition conditions. Because of the lower expansion rates generated by using driver inserts, the first strategy is limited to the low-temperature regime, with dominant pathways at critical conditions related to the chemical dynamics of HO2. For the second strategy, the much higher expansion rate enables to access the high-temperature regime, for which successful ignition is driven by chain-branching chemistry.

Evaluation of high-pressure syngas ignition under high-CO2 dilution in shock tubes

Due to its importance as a candidate fuel for power cycles for future energy production, there have been active efforts to improve our understanding of the chemical kinetics of the Allam-Fetvedt cycle that utilizes syngas highly diluted with CO2. Shock-tube ignition delay times (IDT) of syngas-CO2 mixtures over a range of pressures, syngas blends, and equivalence ratios are now available in the literature, but their unique behavior deserves further study before the resulting data can be used to modify existing syngas kinetics models. In this study, an analysis of CO2-diluted syngas ignition behind reflected shock waves was conducted at the High-Pressure Shock Tube facility at Texas A&M University using an endwall imaging system. A syngas blend of 1:1 H2:CO at an equivalence ratio of 1 was studied at pressures around 12 atm for CO2 dilutions of 85, 88, and 94 % by volume. The combined results of the high-speed OH* imaging through the endwall and OH* time histories from sidewall windows indicate that the initial ignition event appears to be homogeneous and occurs first near the endwall, with no apparent premature ignition or localized flame kernels. An important finding of this investigation is that the existing syngas-CO2 IDT data in the literature are likely free from shock-tube ignition inhomogeneities. Therefore, they can be used to improve existing chemical kinetics mechanisms, which currently have trouble modeling the existing literature data over the range of temperatures of the shock-tube studies (∼1000 – 1400 K). Additionally, the lack of a measured post-combustion pressure rise makes it necessary to use a constant-pressure-enthalpy constraint when modeling the shock-tube IDT event.

Measurements of laminar burning velocities and an improved kinetic model of methyl isopropyl ketone

Methyl isopropyl ketone (MIPK) is the simplest branched ketone and a promising biofuel. In this work, laminar burning velocities (SL) of MIPK + air flames were measured using the heat flux method at atmospheric pressure, over initial mixture temperatures of 298–358 K and equivalence ratios of 0.7–1.4. With the help of the temperature dependence of the SL, data inconsistency between the present measurements and the experimental data reported by Li et al. (Proc. Combust. Inst. 38 (2021) 2135) was demonstrated. Moreover, existing kinetic models for MIPK combustion notably deviate from the present SL measurements. Therefore, the MIPK model suggested by Lin et al. (Proc. Combust. Inst. 39 (2023) 315) was updated by revisiting the MIPK H-abstraction reactions and methyl isopropenyl ketone sub-model. Furthermore, a new di-methyl ketene (critical intermediate during MIPK oxidation) sub-model was constructed and integrated into the MIPK model. Flux and sensitivity analyses revealed that integration of the new di-methyl ketene model improves predictions of the laminar burning velocities as well as shock tube ignition delay times over the pressures of 1–40 bar due to converting di-methyl ketene into C3H5-T (CH2 = C˙CH3) rather than C3H6 or C3H5-S (C˙H = CHCH3) predicted by other MIPK models from the literature. Updates of the MIPK H-abstraction reactions yield more reasonable products branching ratios of formation of the primary fuel radicals, and improve prediction of the SL. It was also found that the rate constants of the MIPK decomposition reaction (MIPK (+M) = CH3CO + IC3H7 (+M)) in the model proposed by Li et al. (Proc. Combust. Inst. 38 (2021) 2135) are significantly underestimated, resulting in underestimation of the present SL measurements and significant overprediction of the ignition delay times.

A Novel Reduced Reaction Mechanism for Diesel/2,5-Dimethylfuran Engine Application

The application of 2,5-dimethylfuran (DMF) as an alternative fuel for internal combustion engines has been gaining popularity. However, it has rarely been studied in previous research on the chemical kinetics of DMF for engine combustion simulations. In the present study, a reduced n-heptane/toluene/DMF-polycyclic aromatic hydrocarbon (PAH) reaction mechanism containing only 78 species amongst 190 reactions was proposed and applied to predict the combustion and emissions of a diesel engine using diesel/DMF blend fuel. First, a detailed reaction mechanism for DMF from the literature was chosen and reduced using combined mechanism reduction methods under engine-relevant conditions. Second, the reduced mechanism of DMF was incorporated into an existing reduced n-heptane/toluene-PAH mechanism to establish a three-component chemistry mechanism. Third, the predictive capability of the combined mechanism was improved by adjusting the rate constants of selected gas-phase reactions. Subsequently, the proposed three-component mechanism was compared and validated with experimental measurements of shock tube ignition delay times and premixed flame species profiles acquired from published papers. Moreover, new experimental data from a conventional diesel engine were used to evaluate the developed mechanism. Overall, the predicted results obtained by this proposed reduced n-heptane/toluene/DMF-PAH mechanism are in reasonable agreement with the available experiments.

NOx formation from ammonia, and its effects on oxy-combustion of hydrocarbon fuels under supercritical-CO2 conditions

NOx formation from ammonia impurities and its effects on fuel oxidation is not well understood for high-pressure supercritical CO2 oxy-combustion conditions. This effect is investigated computationally and experimentally in the present work. A chemical kinetic analysis revealed that the reaction between NH radical and CO2 plays an important role in determining the rate of NOx formation at these conditions. It was also found that a significant reduction in the NOx formation from ammonia oxidation occurs with sCO2 oxy-combustion at 300 atm when compared to traditional gas turbine conditions. A chemical reactor network simulation of realistic sCO2 cycle conditions confirmed the reduced NOx emissions. Monte Carlo simulations used to study the sensitivity of model input variables on the emissions showed that CO2 cooling impacts the CO emissions while most of the NOx are generated in the flame zone. Uncertainty analysis showed that the reaction between NH and CO2 to form HNO radical is an important contributor to the model uncertainty under sCO2 oxy-combustion conditions.The presence of combustion-generated NOx in the recycled-CO2 can impact the fuel oxidation in the primary zone of the combustor. Hence, to understand the effect of NOx on ignition, high-pressure shock tube ignition delay time experiments were performed at conditions relevant to sCO2 oxy-combustion. The ignition delay time measurements were made for syngas and CH4 fuels with and without NO addition under supercritical conditions using CO2 as the bulk diluent at nominal pressures around 100 atm. Experimental data showed that the presence of NO promotes ignition at these conditions. The effect is more pronounced for CH4 compared to syngas. Nitric oxide acts as a chemical catalyst to promote ignition by increasing the combustion radical pool. The catalytic cycle involves the conversion of NO to NO2 which also contributes to CH4 oxidation by H-atom abstraction to generate CH3 radical.

Simultaneous side-wall-schlieren and -emission imaging of autoignition phenomena in conventional and constrained-reaction-volume shock-tube experiments

Simultaneous schlieren and emission imaging through the side wall of a round shock tube is reported for application to experimental autoignition studies. A round, optically accessible shock tube featuring windows designed as aberration-corrected cylindrical lenses provides a large side-wall field of view compatible with both emission and schlieren imaging. Autoignition experiments are reported for non-dilute propane–oxygen–argon mixtures (ϕ=1 C3H8 in 21% O2, 79% Ar) at temperatures (T5) spanning the range 1,203–1,438 K and pressures near 1 atm. Experiments are performed using both conventional and constrained-reaction-volume (CRV) filling, allowing for the most detailed comparison to date of ignition dynamics between these two types of experiments. When T5 exceeds 1,290 K, strong ignition is observed to initiate in the immediate proximity of the end wall regardless of the filling strategy. In lower-T5 experiments, mild ignition is observed to initiate spontaneously at remote locations, which often exceeding the imaging FOV in conventional experiments but are constrained within about 5 cm of the end wall in CRV experiments. Measured ignition delay times (IDTs) are compared to predictions from three kinetic mechanisms. IDTs simulated using the San Diego and USC Mech II mechanisms are of the same magnitude as the measurements but exhibit a lower activation energy; the propane submechanism from NUIG 1.1, meanwhile, systematically over predicts observed IDTs by roughly a factor of two. Comparisons are also made between the experimental measurements and predictions from a recently introduced 1-D axial-temperature-gradient model describing remote ignition in shock tubes. Considering the effect of a supposed dT5/dz=150 K/m gradient, the 1-D model functionally predicts the remote ignition observed in T5< 1,290 K experiments and suggests the use of CRV filling may significantly reduce the error introduced into IDT measurements by remote ignition at low-T5 conditions.

An optimized kinetic model for H[formula omitted]/CO combustion in CO[formula omitted] diluent at elevated pressures

Oxy-fuel combustion is a promising strategy for carbon capture. Existing syngas combustion models overpredicted recently measured ignition delay time data in high-level CO2 diluent and elevated pressures (40, 80, 100 and 200 atm). A trial model was constructed by updating the Kéromnès mechanism (Combust. Flame, 2013, 160, 995–1011) with some recent reaction rate studies and the addition of O+OH+M = HO2+M. Among all 33 reactions, 23 influential reactions were selected for optimization based on sensitivity results. 787 syngas shock-tube ignition delay time data and 1900 laminar flame speed measurements were considered. The optimized model was computed from the trial model using an efficient two-stage optimization strategy. Temperature-dependent initial uncertainty was implemented and all Arrhenius parameters were optimization simultaneously. The optimized model significantly improves the prediction accuracy for the ignition delay time targets, especially those in CO2 diluent, and produces comparable prediction performance for the laminar flame speed targets to the other models. Most of the reaction rate adjustments were well within the corresponding uncertainty (≤30%). Five reactions with relatively large rate adjustment were discussed. Sensitivity and reaction path analysis were conducted to examine the kinetic difference between the optimized model and the Kéromnès model at relevant conditions. Chemical and physical effects of CO2 as a diluent were investigated.

Experimental and computational studies of methanol and ethanol preignition behind reflected shock waves

Experimental and computational investigations are carried out to identify the generalized criterion to predict the preignition tendency of methanol and ethanol mixtures in shock tubes. Preignition or weak ignition in shock tubes has been reported to be a significant factor impacting the accuracy of the ignition delay times data. A systematic means to predict the extent of non-idealities needs to be established and validated with experimental data over a wide range of conditions. Measurements of ignition delay times of methanol and ethanol mixtures were performed to identify unexpectedly expedited ignition. Methanol mixtures showed preignition at low temperatures, similarly to ethanol mixtures. Endwall high-speed imaging was implemented to assess spatial uniformity of ignition for methanol and ethanol. Furthermore, 1-D simulations of ethanol/methanol mixtures, in the presence of ignition sources, were utilized to investigate various preignition criteria. The Sankaran number criterion (Sap), proposed earlier for ignition regime identification, was found to be the most successful predictor of the experimental observations.

Ignition delay and chemical–kinetic modeling of undiluted mixtures in a high‐pressure shock tube: Nonideal effects and comparative uncertainty analysis

AbstractHigh‐pressure shock tube ignition delay data are essential for fuel characterization and for the validation and optimization of chemical–kinetic models. Therefore, it is crucial that realistic measurement conditions are considered in modeling. Furthermore, an accurate uncertainty quantification for experimental data is the basis for evaluation of the predictive reliability of chemical–kinetic models. Several measurement aspects are investigated to improve the interpretation of measurement results: (1) A new approach for integrating the nonideal pressure rise into chemical–kinetic modeling based on a correlation to measurement data is introduced, which enables the determination at each condition and fuel–air mixture individually with minimal effort. (2) A semiempirical model for available test times of reactive mixtures is introduced, which is based on measurement data of nonreactive mixtures. It allows for a priori prediction of test times and provides experimental limits to support the measurement. (3) A literature review shows that different uncertainty sources are considered in ignition delay time uncertainty analysis. A comparative analysis is conducted to investigate the significance of different uncertainty sources for test temperature and ignition delay time. The analysis of ignition delay time uncertainty indicates that for fuels with negative temperature coefficient behavior a comprehensive uncertainty analysis has to be conducted to accurately estimate measurement uncertainty in the intermediate temperature range. Additionally, ignition delay times of dimethyl ether–air mixtures are measured at pressures of 8, 12, and 35 bar and at equivalence ratios of 0.5, 1.0, and 2.0. Furthermore, the data on first‐stage ignition delay are rather scarce and have therefore been recorded additionally. The new approach of integrating the nonideal pressure rise into modeling and the comprehensive uncertainty analysis supports the interpretation of measurement data, such that the prediction capabilities of chemical–kinetic models can be evaluated thoroughly.

Numerical Investigation of Remote Ignition in Shock Tubes

Highly resolved two- and three-dimensional computational fluid dynamics (CFD) simulations are presented for shock-tube experiments containing hydrogen/oxygen (H2/O2) mixtures, to investigate mechanisms leading to remote ignition. The results of the reactive cases are compared against experimental results from Meyer and Oppenheim (Proc Combust Inst 13(1): 1153–1164, 1971. https://doi.org/10.1016/s0082-0784(71)80112-1) and Hanson et al. (Combust Flame 160(9): 1550–1558, 2013. https://doi.org/10.1016/j.combustflame.2013.03.026). The results of the non-reactive case are compared against shock tube experiments, recently carried out in Duisburg and Texas. The computational domain covers the end-wall region of the shock tube and applies high order numerics featuring an all-speed approximate Riemann scheme, combined with a 5th order interpolation scheme. Direct chemistry is employed using detailed reaction mechanisms with 11 species and up to 40 reactions, on a grid with up to 2.2 billion cells. Additional two-dimensional simulations are performed for non-reactive conditions to validate the treatment of boundary-layer effects at the inlet of the computational domain. The computational domain covers a region at the end part of the shock tube. The ignition process is analyzed by fields of localized, expected ignition times. Instantaneous fields of temperature, pressure, entropy, and dissipation rate are presented to explain the flow dynamics, specifically in the case of a bifurcated reflected shock. In all cases regions with locally increased temperatures were observed, reducing the local ignition-delay time in areas away from the end wall significantly, thus compensating for the late compression by the reflected shock and therefore leading for first ignition at a remote location, i.e., away from the end wall where the ignition would occur under ideal conditions. In cases without a bifurcated reflected shock, the temperature increase results from shock attenuation. In cases with a bifurcated reflected shock, the formation of a second normal shock and shear near the slip line is found to be crucial for the remote ignition to take place. Overall, the two- and three-dimensional simulations were found to qualitatively explain the occurrence of remote ignition and to be quantitatively correct, implying that they include the correct physics.

Studying the influence of single droplets on fuel/air ignition in a high-pressure shock tube.

The interaction of fuel and lubricant droplets with gaseous fuel/air mixtures close to autoignition is relevant in the context of unwanted early autoignition in spark-ignition internal combustion (IC) engines. To study the influence of droplets on the ignition of fuel/air mixtures independent from the in-cylinder pressure/temperature history, the shock-tube technique in combination with an injection system was established, which enables the generation and injection of single droplets or droplet clusters of n-dodecane and lubricant base oil behind reflected shock waves at pressures and temperatures representative for the compression phase of IC engines. Injected droplets were imaged by high-repetition-rate laser-induced fluorescence. The ignition process was observed by imaging in the visible and UV simultaneously through the shock-tube end wall with a combination of color- and UV-sensitive high-repetition-rate cameras. It was found that the amount and composition of the injected liquid are important factors determining the extent of the interference with the ongoing autoignition of the premixed fuel/air bath gas. For a stoichiometric mixture of primary reference fuels (PRF95) in air, the droplets significantly accelerate ignition especially in the negative temperature coefficient regime at around 760 K. The comparison of the timing of local ignition and the occurrence of volumetric ignition indicates that only in cases where the surrounding gas is close to autoignition, the droplets can trigger early autoignition. This required temporal and spatial coincidence might explain the high level of randomness of early autoignition in engines.

Acetaldehyde oxidation at elevated pressure

A detailed chemical kinetic model for oxidation of CH3CHO at intermediate to high temperature and elevated pressure has been developed and evaluated by comparing predictions to novel high-pressure flow reactor experiments as well as shock tube ignition delay measurements and jet-stirred reactor data from literature. The flow reactor experiments were conducted with a slightly lean CH3CHO/O2 mixture highly diluted in N2 at 600–900 K and pressures of 25 and 100 bar. At the highest pressure, the oxidation of CH3CHO was in the NTC regime, controlled to a large extent by the thermal stability and reactions of peroxide species such as HO2, CH3OO, and CH3C(O)OO. Model predictions were generally in good agreement with the experimental data, even though the predicted temperature for onset of reaction was overpredicted at 100 bar. This discrepancy was attributed mainly to uncertainties in the CH3C(O)OO reaction subset. Predictions of ignition delays in shock tubes and species profiles in JSR experiments were also satisfactory. At temperatures above the NTC regime, acetaldehyde ignition and oxidation is affected mainly by the competition between dissociation of CH3CHO and reaction with the radical pool, and by reactions in the methane subset.

Modes of mild ignition in shock tubes: Origins and classification

The paper analyses numerically the scenarios of ignition kernels formation in the shock tube in the intermediate temperature range. Three modes of mild ignition are distinguished among which are: ignition related to the shear heating in the developed boundary layer, ignition due to the shear heating in the recirculation zone behind the reflected shock and ignition in the central region of the tube due to the axial compression. All three modes define short ignition delays at low temperatures compared to the ideal shock-tube values. Moreover, it is shown that the gas-dynamic mechanisms responsible for additional local heating of the test mixture provide close rates of heating. As a result, all the data on ignition delays fall in a certain range defined by the mixture composition and pressure, independent on the particular mode of mild ignition.

Ethanol ignition in a high-pressure shock tube: Ignition delay time and high-repetition-rate imaging measurements

Ethanol is known to be prone to pre-ignition in internal combustion engines under high-load conditions and its ignition shows large deviations from ideal, spatially, and temporally-homogeneous ignition in shock tubes at moderate temperatures (800–950 K). In this context, the ignition of stoichiometric ethanol/O2 mixtures with various levels of inert gas dilution was investigated in a high-pressure shock tube at ≅20 bar between 800 and 1250 K. Ignition delay times were determined from spatially integral detection of chemiluminescence emission. Additionally, high-repetition-rate color imaging enabled the differentiation of the luminescence in time, space, and spectral range between various ignition modes. In the low-temperature range (800–860 K), different inhomogeneous ignition modes were identified. The addition of small amounts of helium into the undiluted fuel/air mixture was found to be efficient to mitigate pre-ignition, attributed to a variation in heat transfer and thus suppression of the build-up of local temperature inhomogeneities. The experiments in case of spatially homogeneous ignition show very good agreement with the predictions based on three detailed kinetics mechanisms (Zhang et al., CNF 190 (2018) 74, Frassoldati et al., CNF 159 (2012) 2295, and Zhou et al. CNF 197 (2018) 423), inhomogeneities, however, resulted in a shortening of the ignition delay times up to a factor of 2.6.

High-speed imaging of n-heptane ignition in a high-pressure shock tube

Homogeneous and inhomogeneous ignition modes of n-heptane were studied using high-speed imaging in a high-pressure shock tube (HPST). n-Heptane, a fuel with strong negative temperature coefficient (NTC) behavior, was mixed with 4%-21% oxygen in argon or nitrogen and ignited over a wide temperature range (700–1250 K) and at elevated pressures (> 10 atm). Ultraviolet (UV) images of OH* emission were captured through a sapphire shock-tube end wall using a high-speed camera and a UV intensifier. The current study demonstrates the capability to study auto-ignition modes using high-speed imaging in a high-pressure shock tube. Both homogeneous and inhomogeneous auto-ignition events were observed with the latter generally confined to intermediate temperatures and reactive n-heptane mixtures. We also observed that conventional sidewall diagnostic signals are, in many cases, sufficient to identify inhomogeneous ignitions that are not accurately modeled under the assumption of spatially uniform chemistry.

Effects of Particle Size on the Ignition of Static CH4/Air and H2/Air Mixtures by Hot Particles

ABSTRACT Understanding and characterizing the non-homogenous ignition of flammable mixtures by hot particles are important for industry safety. In this study, one-dimensional transient simulations considering detailed chemistry and transport are conducted for the ignition of static methane/air and hydrogen/air mixtures by hot particles with different radii. The objective is to assess the effects of particle size on the ignition delay time for the hot particle-induced ignition process. Unlike the nearly homogenous ignition in shock tubes or rapid compression machines, the non-homogeneous ignition caused by a hot particle depends on not only chemical kinetics but also transport of reactive species. It is found that 1D hot particle ignition is much slower than the 0D homogenous ignition (in which the mixture temperature is the same as the fixed particle temperature) since there is radical loss near the particle surface caused by mass diffusion. The ignition delay time for hot particle ignition is found to strongly depend on the particle radius and temperature. This is interpreted through the change of radical loss with particle radius and temperature. Moreover, to characterize the hot particle ignition, we introduce a Damköhler number which is the ratio between two characteristic times for chemical reaction and mass diffusion. The change of the normalized ignition delay time for 1D hot particle with the Damköhler number is discussed; and a linear relationship is observed for certain conditions.

Two Mechanisms of Kernel Ignition in Shock Tubes

The structure of the flow and temperature field behind a reflected shock wave in a shock tube is studied by numerical modeling. Two possible scenarios of the formation of the regions of elevated temperature, which are the potential ignition kernels of the gaseous mixture under the study, are demonstrated. Both scenarios are assessed as equally probable; however, depending on the parameters of the flow and diameter of the tube, one of the scenarios may be implemented earlier than the other, which is demonstrated by the example of a hydrogen–air mixture. The scenario with the ignition on the axis is the most probable one for the case of high temperatures and narrow channels, while ignition in the region of the boundary layer is implemented with a higher probability at moderate temperatures in wide channels.

Shock tube ignition delay time measurements for methyl propanoate and methyl acrylate: Influence of saturation on small methyl ester high‐temperature reactivity

AbstractWe report ignition delay time measurements for methyl propanoate (MP) and methyl acrylate (MA), carried out in a high‐pressure shock tube. Experiments were performed behind reflected shock waves across a temperature range of 989‐1 367 K, for fuel‐air mixtures at equivalence ratios of ϕ = 0.5, 1.0, and 2.0, and nominal pressures of 1 and 4 MPa. Ignition delay times were found to decrease with increasing temperature, equivalence ratio, and pressure, and are well described with correlations involving Arrhenius temperature dependence and power‐law dependence on equivalence ratio and pressure. Ignition delay times are compared with model predictions from literature kinetic models, with the models of Zhang et al (Energy &amp; Fuels 2014; 28(11): 7194‐7202) and Bennadji et al (International Journal of Chemical Kinetics 2011; 43(4): 204‐218.) in good agreement with measured ignition delay times for MP and MA, respectively. Kinetic sensitivity analysis shows that the reactions most important for modeling ignition fall into two categories: initiation reactions (ie, decomposition and H‐atom abstraction) and C0‐C1 chemistry controlling the pool of small radicals. The unsaturated MA was observed to have lower reactivity than MP, due to its greater bond strengths for C─C and C─H bonds, resulting in slower rates for initiation reactions.

Comment on “Simultaneous lateral and endwall high-speed visualization of ignition in a circular shock tube” [Combustion and Flame 214 (2020) 263–265

Comment on “Simultaneous lateral and endwall high-speed visualization of ignition in a circular shock tube” [Combustion and Flame 214 (2020) 263–265

A skeletal n-butane mechanism with integrated simplification method

A new skeletal mechanism of n-butane is developed for describing its ignition and combustion characteristics applicable over a wide range of conditions: initial temperature 690–1430 K, pressure 1–30 atm, and equivalence ratio 0.5–2.0. Starting with a detailed chemical reaction kinetic model of 230 species and 1328 reactions (Healy et al., Combust. Flame, 2010), the directed relation graph method is applied as the first step to derive a semi-detailed mechanism with 134 species. Then, the reaction path analysis in conjunction with temperature sensitivity analysis is used to remove the redundant species and reaction paths simultaneously under the condition of low-temperature and moderate-to-high temperatures, respectively. Finally, a skeletal n-butane mechanism consisting of 86 species and 373 reactions can be obtained. Mechanism validation indicates that the new developed skeletal mechanism is in good agreement with the detailed mechanism in predicting the global ignition and combustion characteristics. The new skeletal mechanism is further validated using extensive available literature data including rapid pressure machine ignition delay time, shock-tube ignition delay time, laminar flame speed, and jet-stirred reaction oxidation, covering a large range of temperatures, pressures, and equivalence ratios. The comparison results demonstrate that a satisfactory agreement between predictions and experimental measurements is achieved.