Accurate assessment of novel aviation fuels requires detailed insight about structural differences relative to conventional jet fuels. To support compositional characterization, retention behavior of cycloalkanes needs to be investigated further to evaluate fuels on an isomeric level. Current available literature models for the prediction of saturated cyclic retention indices (RI) are limited in carbon range or by neglection of stereo isomeric effects. This study addresses the challenge of comprehensive RI prediction of mono-cycloalkanes by utilizing available retention data from the NIST23 database and the combination of descriptors from PaDEL, Mordred and RDKit. Multiple model approaches (extreme gradient boosting, multi-layer perceptron regression, support vector regression and ridge regression) were tested via repeated k-fold cross-validation to evaluate robustness and reliability in prediction. As the available literature data was skewed, model tests were run for data up to carbon number C13 and the whole dataset to C20 individually. Cross-validation results showed the best error metrics for the validation sets with ridge regression (e.g. C13-models mean absolute error: MAE = 11.01 ± 1.32 RI; C20-model MAE = 13.68 ± 1.67 RI). Correct stereo sensitive retention of diastereomeric structures was achieved in 78 %, with cis/trans differentiation being the best represented stereo effect. These advancements will enable a more detailed characterization of compositional differences and will subsequently enhance evaluation of novel fuel production paths.

Alternative aviation fuels are crucial to achieve CO2 neutrality and reduce non-CO2 climate effects. By reducing soot and advancing the understanding of contrail formation, these fuels hold the potential to mitigate warming effects on a global scale while also improving local air quality. Consequently, a comprehensive understanding of pollutant formation during the combustion of fuels or single component model fuels, with a particular focus on soot formation, is crucial for further fuel optimization. The development of fast and efficient methods for measuring parameters like the soot potential with regard to different molecular components are essential to achieve this objective. A novel screening method is currently under development to provide a fast overview of soot tendencies of different fuels or fuel components. To enhance the efficiency of measuring the soot tendency related to the yield sooting index (YSI), through the reduction of sample volumes, automation, and increased throughput in a shorter time frame compared to existing experiments with diffusion flames. This approach is based on measurements of soot precursors in the DLR’s flow reactor coupled with molecular-beam mass spectrometry (MBMS). In order to optimize the throughput of samples, a standalone autosampler apparatus has been integrated into the existing experimental setup, together with a new method for the data evaluation. This study provides insights into the soot formation by demonstrating a correlation between measured signal intensities of C12H10 as soot precursor, obtained through the developed method, and the YSI, while also introducing a novel sooting index, called derived sooting index (DSI).

This study investigates the oxidation of three oxymethylene ethers (OME1-3) in a new elevated-pressure laminar plug-flow reactor, utilizing electron-ionization molecular-beam mass spectrometry. Experiments were conducted at an absolute pressure of 5 bar to mimic conditions more relevant to combustion systems but still allowing for the exploration of reaction kinetics and pathways in a controlled environment. The experimental work is supported by kinetic modeling using our in-house DLR Concise mechanism to gain deeper insights into OME1-3 combustion chemistry and highlight the controlling pathways. Kinetic modeling with two additional literature mechanisms was also employed to complement the findings. The measurements at constant carbon flow and similar conditions enable a systematic analogy among the three studied OMEs. The results reveal preferred formation of small C1-C2 hydrocarbons and oxygenates such as formaldehyde and methyl formate as combustion intermediates. Formation of methanol and formic acid was also observed during oxidation of all three OMEs, but the latter in significantly higher concentrations for both longer-chain OMEs. OME1 shows only low reactivity in the low-temperature chemistry (LTC) regime, while the two larger OMEs have a higher reactivity in the LTC regime and also show a negative temperature coefficient behavior at the studied conditions. In line with previous reactor studies at atmospheric pressure, the reactivity of OME2 and OME3 is also similar at 5 bar, but is clearly distinguishable from OME1. This work not only enhances our understanding of the fundamental chemistry underlying the oxidation mechanisms of OMEs, but also underscores their potential as cleaner fuel alternatives.

To evaluate sustainable aviation fuels (SAF) and other novel jet fuels, nontargeted comprehensive analysis by two-dimensional gas chromatography (GCxGC) is commonly utilized. The obtained results are necessary for subsequent model-based prescreening applications. The uncertainty of the respective property predictions is dependent on the degree of compositional detail as some properties (e.g., flash point, freezing point) are strongly influenced by structural molecular features. In the absence of sufficient structural reference data, individual identification from reference databases is usually not possible. Consequently, the results obtained from GCxGC are generally categorized by the carbon number and group type. To obtain greater details on the isomeric structure distribution of fuels, the iso-alkane family was further investigated. Therefore, a multilinear regression model for iso-alkane retention indices (RI) was constructed from molecular descriptors. Subsequently, the combined database from measurement and literature was extended by prediction to complete the data for all possible 42,900 branched isomers within the jet range (C7-C17). The isomeric structures were sorted into subgroups by their respective retention behavior, thereby correlating with the present number of molecular branches. The structural subgroup information was then used to create branching indicators to quantify and compare the subgroup distributions of different fuels. It was evident that isomeric distributions were unique to the respective samples. The new detail of composition will aid the characterization and differentiation of different fuels and present further potential for fuel assessment.

In our previous work on hydrocarbons (Kathrotia et al., Fuel 2021;302:120736) and jet fuels (Kathrotia et al., Fuel 2021;302:120737) the molecular fuel composition was shown to be an important aspect of understanding the fuel combustion chemistry and, more importantly, the emission behavior. In this extension, we elaborate our high-temperature jet fuel surrogate reaction mechanism (referred hereafter as DLR Concise) to include the chemical class of oxygenated hydrocarbons for transportation fuels. These oxygen containing species have been widely investigated in ground transportation fuels. With DLR Concise we aim for a flexible reaction model for alternative fuel surrogates; a single reaction model with the target application to both aviation- as well as transportation-fuels. The main focus of this work is to describe the reaction kinetics of oxymethylene ethers (OMEx, x = 0-5) in low to high temperatures. OMEs are promising alternative fuels that can be derived from a variety of sustainable sources. The absence or reduction of C-C bonds makes them attractive for the reduction of soot precursors and soot emissions. The reaction model of OMEs presented in this work is extensively validated against wide-ranging experiments both in-house and from literature. The main purpose of the DLR Concise is to provide a reaction mechanism with a large degree in flexibility to simulate various fuel surrogates (existing and new) and predict pollutants for the fuel assessment based on fuel molecular structure. A comprehensive model validation as well as new in-house experimental data set on C1-C4 alcohols and primary reference fuel (PRF90) measured in high-temperature flow reactor is available as supplemental material.

Comprehensive speciation datasets for the stoichiometric oxidation and pyrolysis of the two monoterpenes limonene (C10H16) and 1,8-cineole (C10H18O) are measured in an atmospheric laminar flow reactor using electron-ionization molecular-beam mass spectrometry. This setup allows direct sampling from the reactive flow and preserves the actual gas composition. Furthermore, clear determination of the exact elemental composition of the formed species is possible with the used time-of-flight mass spectrometer. Limonene is a monocyclic terpene and 1,8-cineole is a saturated bicyclic terpene ether and both terpenes might be potential biofuel candidates. Focus in this study is the intermediate temperature region between 673 and 1173 K to obtain insights into the first fuel decomposition steps and the formation of typical soot precursors. The obtained mole fraction profiles for over 40 species in each of the investigated terpenes are a first step for future development and validation of chemical kinetic combustion mechanisms. While the overall species pool is similar, significant concentration differences can be observed for certain combustion intermediates. For limonene, larger quantities of C8-C10 hydrocarbons are detected and most of them are probably substituted benzenes or cyclohexadienes formed from hydrogen abstraction. Some reaction steps in the decomposition of limonene may also involve initial isomerization of the fuel molecule. In contrast, direct formation of C 7 H 11 radicals and acetone (C3H6O) is identified as an important decomposition step of 1,8-cineole. C 7 H 11 is then a source of toluene (C7H8) and cyclohexadienes (C6H8). Generally, a higher sooting propensity of limonene compared to 1,8-cineole can be expected due to the higher concentrations of polycyclic aromatic hydrocarbons (PAHs) in the investigated temperature range. During limonene oxidation, formation of oxygenated species larger than the fuel molecule are observed and might represent carbonyls or cyclic ethers from the first oxygen addition due to low-temperature chemistry.

Gas-phase oxidation of ethyl tert-butyl ether (ETBE) and methyl tert-butyl ether (MTBE) has been studied using molecular-beam mass spectrometry (MBMS) coupled with the DLR flow reactor for atmospheric and highpressure measurements. Over a temperature range of 750-1200 K at 1 bar and 500-1200 K at 5 bar, MTBE and ETBE were measured at slightly fuel-rich conditions with an equivalence ratio of 1.2. These experiments have been modeled using chemical kinetic mechanisms. An updated version of our in-house mechanism DLR Concise and literature mechanisms were used to model measured flow reactor mole fraction species profiles. Good agreement between computed and experimental values is obtained for measurements at both pressure conditions.

The resonance-stabilized cyclopentadienyl (C5H5) and propargyl (C3H3) radicals are important precursors for polycyclic aromatic hydrocarbons (PAHs) and thus play a significant role in molecular-weight growth and soot formation processes under combustion conditions. In this work, we describe an experimental and theoretical investigation of the C5H5 + C3H3 reaction. Experimentally, we studied this reaction in a resistively heated microtubular SiC reactor at a controlled temperature of ∼1150 K and a pressure of 10-20 mbar. The reactants C5H5 and C3H3 were pyrolytically generated from anisole (C6H5OCH3) and propargyl bromide (C3H3Br). We identified the reactants and the C8H8 products isomer-selectively utilizing photoion mass-selected threshold photoelectron spectroscopy (ms-TPES). The experimentally observed predominant formation of dihydropentalenes over the ring-enlargement reaction to styrene is consistent with our theoretical predictions of the kinetics on the newly calculated C8H8 potential energy surface. This work highlights dihydropentalenes as reactants in molecular-weight growth reactions and as potential building blocks in versatile routes for the formation of curved PAHs.

Radical-radical reactions play a crucial role in the molecular-weight growth that leads to the formation of polycyclic aromatic hydrocarbons (PAHs) and ultimately soot. In this study, we experimentally investigated the reaction between C6H5 (phenyl) and C3H3 (propargyl) at pressures around 30 Torr and combustion-relevant temperatures (∼1200 K). The reactants were generated through flash pyrolysis of nitrosobenzene and propargyl bromide in a resistively heated SiC tube. We identified the reaction intermediates and products using mass-selected threshold photoelectron spectroscopy (ms-TPES) with the photoelectron-photoion coincidence (PEPICO) instrument at the vacuum-ultraviolet (VUV) beamline of the Swiss Light Source at the Paul Scherrer Institute. Our findings indicate that C6H5 associates with C3H3 to form C9H8, which partially decomposes via hydrogen loss to yield C9H7 radicals. The C6H5 + C3H3 reaction is complex and yields more than just the most stable indene isomer. The experimental threshold photoelectron spectrum provides clear spectroscopic evidence of five isomers: indene, phenylallene, 1-phenyl-1-propyne, 1-phenyl-3-propyne, and cycloprop-2-en-1-ylbenzene. The inclusion of a sixth isomer, 3aH-indene, provides an even better fit to the experimental spectrum, although its presence should not be considered conclusive. All of these species correspond to minima on the known C9H8 potential energy surface [Selby et al., J. Phys. Chem. A, 2023, 127(11), 2577-2590 and Morozov et al., Phys. Chem. Chem. Phys. 2020, 22(13), 6868-6880]. Many of these isomers are not included in kinetic mechanisms that seek to describe the chemical pathways leading to PAHs.

This study addresses a fundamental source of uncertainty in predicting the properties of sustainable aviation fuels (SAF) based on their composition: the unresolved distribution of structural isomers within iso-alkanes. Two complementary weighted average models are applied to analyze the influence of subgroups in composition analysis on the prediction of fuel properties. Both models are based exclusively on isomer properties and mixing rules without any training or fitting process. The first, the Mean Matrix model, represents fuels using conventional two-dimensional gas chromatography (GCxGC) resolution (carbon number by hydrocarbon family), whereas the second, the SubGroup Mean Matrix (SGMM) model, incorporates retention index (RI) based subgroups within the C7-C17 iso-alkane range to capture structural differences among isomers. Both models are built from a comprehensive isomer database augmented by Quantitative Structure-Property Relationship (QSPR) predictions where experimental data was unavailable. The model performance is evaluated on eight samples (Jet A-1; ATJ-SPK, two FT-SPK and four paraffinic solvents), comparing absolute errors and a normalized Relative Performance Change (RPC) metric. By incorporating higher compositional resolution via iso-alkane subgroups in the SGMM, the predictive accuracy for all evaluated properties of the ATJ-SPK fuel, which is characterized by a narrow and highly branched composition, was significantly improved. These properties included distillation temperatures, density, viscosity, net heat of combustion, and cetane number. In general, the improvements in volatile properties are most noticeable. Bulk properties such as density and net heat of combustion show only minor changes in prediction accuracy. Although the approach improves or maintains the predictive accuracy for the fuel samples, a deterioration can also be observed to some extent in the property prediction of the paraffinic solvents. Overall, the results indicate that incorporating subgroup-level resolution not only improves prediction accuracy for fuels with narrow, highly branched isomer profiles, but also can lead to an average performance improvement for most of the samples.

The formation of five-membered ring structures is important for the generation of curved and bowl-shaped polycyclic aromatic hydrocarbons (PAHs) under combustion conditions. Here, we report the identification of the indenyl (C9H7) 9 H 7 ) radical - the simplest aromatic hydrocarbon radical carrying an adjacent five- and six- membered ring, as the major product of the o- benzyne (o-C6H4) o- C 6 H 4 ) reaction with propargyl (C3H3). 3 H 3 ). Because real flames exhibit a complex chemistry, elucidation of a specific reaction is very challenging. Instead, we studied the o- C 6 H 4 + C3H3 3 H 3 reaction in a resistively heated microtubular SiC reactor at controlled conditions of 1150 K and a pressure near 10-20 Torr. To this end, the reactants o- benzyne and propargyl were pyrolytically generated from benzoyl chloride and propargyl bromide. We identified the reactants and the indenyl radical isomer-selectively utilizing photoion mass-selected threshold photoelectron spectroscopy (ms-TPES). The experimentally observed predominant formation of indenyl radicals finally confirms the theoretical predictions of Matsugi and Miyoshi [Phys. Chem. Chem. Phys. 14 (2012), 9722-9728] and highlights a versatile route for the formation of five- membered rings and curved PAHs via reactions of o- benzyne that favor the formation of multiring species over aliphatically substituted aromatic species.

Oxymethylene ethers (OMEs) are potential alternative fuels that can be produced in a sustainable way based on CO2 and electricity. Additionally, they exhibit low tendencies to emit NOx or soot during practical combustion. Dimethoxy methane (DMM, CH3OCH2OCH3) has received increasing attention as the smallest OME with a O-CH2-O moiety. In the face of a possible application in exhaust gas recirculation (EGR) scenarios, understanding the influence of NOx on DMM oxidation is of importance. In this work, eleven mixtures of DMM/NO/O2/Ar were investigated in an atmospheric laminar flow reactor employing an extensive set of diagnostics. Molecular-beam mass spectrometry (MBMS), Fourier-transform infrared (FTIR) spectroscopy, NOx chemiluminescence detection, and double imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy were combined to obtain a reliable speciation. All in all, species concentrations from different instruments showed a good agreement and one technique could counterbalance the physical limitations of another technique in many cases. In this manner, accurate mole fraction profiles of intermediates like e.g. CH4, C2H4, NO2, and methyl formate (C2H4O2) were gained. Based on i2PEPICO results, nitromethane (CH3NO2) and trans-HONO could additionally be identified as crucial intermediates in the NO-assisted oxidation of DMM. The present data set therefore provides an excellent basis to enhance future model development.

The development of the hybrid chemistry (HyChem) methodology for the chemical kinetic modeling of real fuel combustion has introduced new possibilities for the generation of compact, reduced models. The key feature of this methodology is the separation of the chemical kinetic reaction scheme into two main parts. The first part is a global reaction scheme, representative of a real fuel fast pyrolysis step, which models the decomposition of the fuel into the main gas phase products of combustion processes. The second part of the model consists of a detailed gas phase reaction scheme for the oxidation of the aforementioned main gas phase products. The main prerequisite for the generation of a HyChem model is the identification of the branching factors of the main gas phase products from the fast pyrolysis reaction step. The original parameter identification requires an extensive experimental investigation of the fuel pyrolysis and combustion characteristics. We introduce new procedures to create hybrid chemistry models with chemical kinetic parameter optimization based either on experimental or numerically generated targets. With the experimental target approach, indirect chemical kinetic experiments are targeted by the parameter optimization, including ignition delay times and laminar burning velocities as well as species profiles measured in a flow reactor. For the numerical target approach, target data (reactive species profiles) are generated with the chemical kinetic fuel model DLR Concise in combination with a fuel surrogate strategy. HyChem models were generated for two jet fuels. Both the experimental and numerical target approaches are appropriate for generating HyChem models, allowing for highly adaptable model creation with relatively minimal experimental effort.

Renewable fuels are essential to meet climate protection goals, especially for decarbonizing the existing vehicle fleet. In addition, optimized and specially designed fuels allow emissions to be avoided before they occur. This paper presents fuel effects on emission characteristics of six chemically complex gasoline blends compliant with the DIN EN 228 standard and one ethanol/gasoline blend, focusing on particle emissions. First, the sooting propensity of the fuels was examined using different soot indices, such as the Particulate Matter Index (PMI), the Oxygen Extended Sooting Index (OESI), the Yield Sooting Index (YSI), and the soot threshold (phi ST), which is drawn on measurements of the particle number (PN) density in the exhaust gas of a laminar flat flame. Second, PN emissions (particle number concentration) from a production-calibrated turbo gasoline direct injection en-gine with four cylinders were investigated. Third, soot precursor chemistry was investigated using a laminar flow reactor at atmospheric pressure. Finally, correlations to fuels' volatility and chemical characteristics were made for the complete data set. Based on the soot precursor chemistry in the homogeneous gas phase reaction, the analysis shows that engine PN emissions are primarily influenced by fuel chemistry for the investigated engine conditions. In particular, the composition of the hydrocarbon fraction is decisive, with the heavy C9+ aromatics and the upper distillate significantly influencing soot formation. In order to reduce PN engine emissions, future fuels should contain fewer soot-increasing hydrocarbon fractions.

Oxidation processes of a linear and a branched ether, oxymethylene ether 2 (OME2) and trimethoxymethane, also known as trimethyl orthoformate (TMOF), were investigated in two complementary atmospheric flow reactor setups coupled to electron ionization molecular-beam mass spectrometer (EI-MBMS). One with high mass resolution to measure speciation data and the second with photoionization MBMS (i2PEPICO) to gain isomer distribution. It can be shown that both ethers have different reactivity with trimethoxymethane reacting at lower temperatures. Furthermore, fuel decomposition and intermediate profiles can be analyzed by combining the results of isomer fractionation using i2PEPICO combined with the quantitative species profiles of EI-MBMS. The results show a huge number of oxygenated species. While the obtained species pool is similar, measured mole fractions differ. Isomers, as for example ethanol and dimethyl ether, are separated and quantified. Direct comparison of the oxidation intermediates of the linear and branched ether clarifies the different reactivity due to their given fuel structures.

The combustion chemistry of tetramethylethylene (TME) was studied in a premixed laminar low-pressure hydrogen flame by combined photoionization molecular-beam mass spectrometry (PI-MBMS) and photoelectron photoion coincidence (PEPICO) spectroscopy at the Swiss Light Source (SLS) of the Paul Scherrer Institute in Villigen, Switzerland. This hexene isomer with the chemical formula C6H12 has a special structure with only allylic CH bonds. Several combustion intermediate species were identified by their photoionization and threshold photoelectron spectra, respectively. The experimental mole fraction profiles were compared to modeling results from a recently published kinetic reaction mechanism that includes a TME sub-mechanism to describe the TME/H2 flame structure. The first stable intermediate species formed early in the flame front during the combustion of TME are 2-methyl-2-butene (C5H10) at a mass-to-charge ratio (m/z) of 70, 2,3-dimethylbutane (C6H14) at m/z 86, and 3-methyl-1,2-butadiene (C5H8) at m/z 68. Isobutene (C4H8) is also a dominant intermediate in the combustion of TME and results from consumption of 2-methyl-2-butene. In addition to these hydrocarbons, some oxygenated species are formed due to low-temperature combustion chemistry in the consumption pathway of TME under the investigated flame conditions.

Dimethyl ether (DME) is a widely recognized alternative fuel which can be sustainably produced from different feedstock. Its oxidation mechanism belongs to the most deeply understood within oxygenated fuels. The oxidation of DME in the presence of NO has gained renewed attention in recent experimental and modeling efforts because of a rather complex behavior in accelerating or inhibiting DME consumption, depending on the respective temperature and mixture conditions, similarly to what has been already observed for n- and iso-alkanes. The present investigation focuses on the interaction chemistry of DME–O2–NO mixtures in the low- to intermediate-temperature regime. Previously reported flow reactor data from mass spectrometric analysis with and without NO addition are extended by isomer-resolved detection of some key intermediates, including species of formula {HNO2} and {CH3NO2} by using double-imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy. Specifically trans-HONO is highlighted as the most abundant isomer. Starting from the recently published CRECK mechanism for DME oxidation and other models available in the literature, the relevant kinetics of DME/NOx interactions are included and analyzed. The model thus obtained is compared with new experimental data from this study and others from the literature and is used to interpret observed discrepancies. A systematic polynomial chaos expansion (PCE) analysis is also performed to assess the joint uncertainty of key influential reactions under the present conditions. Nevertheless, remaining differences of model and experiment can only be addressed jointly, demonstrating the value of a concurrent experimental–modeling approach.

Liquid fuels such as gasoline, kerosene, or diesel exhibit a very complex chemical composition. The transition toward a sustainable world requires the development of novel alternatives to fossil-based light and middle distillates, leading to a further increase in the composition complexity by the introduction of chemical structures absent in fossil fuels. The transfer of fundamental knowledge on molecular behavior in combustion demands in the first place a reliable analysis of the composition of such fuels, containing hundreds of molecules and chemical structures. This study presents a universal comprehensive two-dimensional gas chromatography (GCxGC) method for the complete group-type to component-by-component analysis of fossil and alternative fuels. The emphasis was placed on the optimized separation of hydrocarbon groups in a large number of different synthetic and fossil fuels and their crude products, with simultaneous sensitive detection by mass spectrometry and flame ionization. The optimized analysis method is applicable for the full range of fossil light to middle distillates as well as various synthetic fuels. In addition to the classification and quantification of the composition in up to 20 chemical groups, the method is characterized by the fact that a component-by-component evaluation is possible. This level of detail is suitable to derive chemicophysical and combustion properties solely from the composition analysis. This is demonstrated by the prediction of the sooting behavior of 20 gasoline fuels including various types of alternative non-petroleum fractions. The sooting tendency is obtained from tabulated molecular Yield Sooting Indices (YSI). The results are successfully validated against smoke point and soot precursor species measurements from a molecular-beam mass spectrometry (MBMS) flow reactor experiment.

This paper presents a systematic study of oxymethylene ethers (OMEs) oxidation in an atmospheric laminar flow reactor setup. Oxymethylene ethers with different number of oxymethylene ether groups (n = 0-5) have been investigated under lean and rich conditions (750-1250 K). The flow reactor is coupled to an electron ionization molecular-beam mass spectrometer (EI-MBMS) with high mass resolution to measure speciation data. Additional isomer-selective speciation analysis was performed using a novel atmospheric laminar flow reactor combined with double-imaging photoelectron photoion coincidence (i(2)PEPICO) spectroscopy at the vacuum ultraviolet radiation (VUV) beamline of the Swiss Light Source. The results show a dominance of oxygenated intermediates during the combustion of all OMEs in the investigated temperature regime. The observed species pool is thereby nearly independent of the OME' s chain length. In particular the presence of significant fractions of ethanol is remarkable and indicates unknown or underestimated reaction pathways to form C-C bonds from OME structures. Formation of combustion intermediates during oxidation of longer OMEs occurs at lower temperatures and correlates with the ignition delay time. No hydrocarbons with more than four carbon atoms are detected. The combination of high mass resolution provided by EI-MBMS detection and isomer-selective analysis by i(2)PEPICO enables a complete overview of all intermediates. This allows for in-depth discussion and analysis of systematic trends for several intermediate species.

Sustainably produced synthetic fuels offer great potential for a fast reduction of the greenhouse gas emissions of the transport sector. For an immediate application within the existing infrastructure and vehicle fleet, synthetic fuels need to comply with existing standards such as the EN 228 for gasoline. Beyond these standards and with optimized fuel design, certain properties can be improved compared to conventional fuels. For this purpose, methods for evaluating the properties are needed. This work discusses the development of a simplified numerical quasi-dimensional two-zone cylinder model, combined with chemical kinetic models, for the estimation of octane numbers. The model emulates fuel specific operating conditions of the standardized procedure for the determination of octane numbers in the cooperative fuel research engine with variable compression ratios. The two zones represent the burned and unburned in-cylinder volume and are modeled with homogeneous reactors. The octane numbers are determined by the identification of the critical compression ratio, for which premature ignition occurs in the unburned reactor. A two-zone cylinder model is validated against experimental data for various primary reference fuels, blended with toluene, ethanol, isobutanol and ethyl tert-butyl ether. The successful application of different kinetic models is demonstrated and enables the application on a wide range of fuels. It is shown that the simulated research octane numbers are in good agreement with the experimental data.