Kerosene Surrogate Research Articles

Development of a Skeletal Mechanism for Aviation Kerosene Surrogate Fuel

In this study, a kerosene surrogate model fuel containing 65 mol % -dodecane, 10% -tetradecane, and 25% decalin is developed by considering both the physical and chemical characteristics of practical aviation kerosene. By combining the skeletal (carbon number) core mechanism and the reduced large hydrocarbon submechanisms, a high-temperature chemical kinetic mechanism including 50 species and 274 reactions is constructed for the kerosene surrogate model fuel. This relatively small size enables the application of computational fluid dynamics. The performance of the skeletal mechanism is validated by examining various experimental laminar flame speeds of single components, mixtures, and practical kerosene. A sensitivity analysis of the laminar flame speed based on the constructed mechanism shows that the flame propagation of the kerosene is strongly dependent on the kinetics, and it is independent of the fuel-specific species and reactions.

Error-controlled kinetics reduction based on non-linear optimization and sensitivity analysis

Efficient reduction techniques are necessary for the construction of compact chemical kinetic mechanisms to enable the application to large-scale simulations. In this work, a new formulation is proposed to derive skeletal mechanisms by species elimination. The proposed method relies on a gradient-based non-linear optimization (NLO) method, allowing for direct error control on user-defined quantities of interest (QoIs). The key idea consists in formulating the species elimination by relaxing an integer-optimization problem into a continuous optimization problem that is solved iteratively. A species-targeted sensitivity analysis (SA) formulation is presented that can be combined with the optimization method to reduce the overall computational complexity of the procedure. After illustrating its principle, the NLO procedure is applied to different fuels of increasing chemical complexity, including methane, n-dodecane, and a four-component kerosene surrogate. Direct comparisons are performed with the directed relation graph method with error propagation (DRGEP) and SA. For the reduction of a detailed methane mechanism, consistency with DRGEP and SA is demonstrated, and the NLO procedure is shown to generate smaller mechanisms compared to the other two methods. In application to larger hydrocarbon and multicomponent transportation fuels, it is shown that significantly smaller mechanisms are obtained with the NLO procedure compared to the other approaches.

Deflagration/Autoignition/Detonation Transition Induced by Flame Propagation in an N-Decane/O2 /Ar Mixture

The aim of this study is to experimentally investigate the combustion regime transitions of a single-component kerosene surrogate (n-decane). For this purpose, a deflagration is generated by a spark in a constant-volume vessel with a length-to-width aspect ratio of 4.3. By consuming the unburnt gas, the flame behaves as a piston that compresses the end gas. The pressure and temperature of the end gas increase with the flame propagation until autoignition conditions are reached. Ultrafast schlieren visualizations are set up to monitor the dynamics of the reactive processes, whereas the time-pressure evolution associated with non-dimensional (0D) numerical models is used to characterize the unburnt gas thermodynamic conditions. Once the thermodynamic conditions needed to initiate the autoignition reactions are reached in the end gas, a transition between deflagration (flame speed of approximately ten m/s) and autoignition fronts is observed (propagation velocity ˜200 m/s). This transition occurs for various fuel equivalence ratio values (0.75 – 1). For the strongest thermodynamic conditions, once the velocity of this autoignition front reaches the speed of sound, a new reactive front propagating up to 1800 m/s is observed, thus indicating the transition to detonation combustion mode. Parametric studies indicated that the occurrence of both transitions was a function of the pressure, temperature and equivalence ratio for n-decane fuel. A small initial temperature variation (approximately 40 K) could change the phenomenology of the constant-volume combustion from deflagration to detonation through the autoignition process, even for lean mixtures. The results obtained using our experimental setup show that the transition between autoignition and detonation is due to the acceleration of the autoignition front towards the speed of sound in the unburnt gas.

Reduction of a detailed chemical mechanism for a kerosene surrogate via RCCE-CSP

Detailed mechanisms for kerosene surrogate fuels contain hundreds of species and thousands of reactions, indicating a necessity for reduced mechanisms. In this work, we employ a framework that combines Rate-Controlled Constrained Equilibrium (RCCE) with Computational Singular Perturbation (CSP) for systematic reduction based on timescale analysis, to reduce a detailed mechanism for a jet fuel surrogate with n-dodecane, methylcyclohexane and m-xylene. Laminar non-premixed flamelets are utilised for the CSP analysis for different strain rates and therefore different scalar dissipation rate, covering the flammable region of strain rates for the surrogate fuel.Two RCCE-reduced mechanisms are developed via an RCCE-CSP methodology, one with 17 and one with 42 species, and their accuracy is assessed in a range of cases that test the performance of the reduced mechanism under both non-premixed and premixed conditions and its dynamic response. These include non-premixed flamelets with varying strain rate, laminar premixed flames for a range of equivalence ratios and pressures, flamelets ignited by an artificial pilot or by hot air, and unsteady flamelets with time-dependent strain rate.The profiles of both major and minor species, as well as important combustion characteristics such as the ignition strain rate and the laminar flame speed, are investigated. The structure of non-premixed flamelets is very well predicted, while the premixed flames are overall well predicted apart from a few deviations in certain species and an underprediction in the laminar flame speed. Apart from the large reduction in dimensionality, the reduction in computational time is also considerable (up to 19 times). As the detailed mechanism comprises 367 species and 1892 reactions, this paper presents the first application of RCCE to a mechanism of this size, as well as a comprehensive validation in a set of cases that include non-premixed and premixed laminar flames, atmospheric and elevated pressures and steady-state and dynamic response.

A simplified chemical reaction mechanism for two-component RP-3 kerosene surrogate fuel and its verification

The simplification of the dynamic model of aviation kerosene oxidation is one of the important problems in numerical simulation of combustion chamber. It plays a decisive role in CFD numerical calculation and for reducing the stiffness of convergence, as well as for introducing chemical reactions to more complex turbulent combustion problems. This study aims to present a two-component surrogate fuel model for chemical reactions. Furthermore, the simplified mechanism of the optimization of the ignition delay time and experimental value is adopted using the direct relation graph method (DRG). As the primary originality for the paper, the eclectic simplified mechanisms with certain precision and fewer components and elementary reactions were concluded. And the simplified mechanism was introduced into FLUENT to simulate the precast evaporation flame of the Bunsen burner, which is a RP-3 fuel. Numerical results are in good agreement with the experimental results. The existing simplified mechanism for the two-component RP-3 aviation kerosene alternative fuel can be applied to the practical engineering problems of the numerical forecast.

Experimental and Kinetic Modeling Study on Self-Ignition of α-Methylnaphthalene in a Heated Rapid Compression Machine

As an important component of diesel and kerosene surrogates, the experimental study and chemical kinetic modeling of α-methylnaphthalene (AMN) are still very insufficient. The ignition delay of an AMN/O2/Ar mixture in a heated rapid compression machine (RCM) was measured in this study. The data were obtained for equivalence ratios of 0.7, 1, and 1.2, at pressures of 12, 15, and 20 bar, over the temperature range of 860–1040 K. A semi-detailed kinetic mechanism for the oxidation of AMN was established, which consists of 196 species and 1330 reactions. In comparison to the different previous mechanism, the new mechanism can more accurately predict the ignition delay of AMN in RCM and shock tube experiments. It can also accurately predict the experimental data obtained in a jet-stirred reactor from the literature. The ignition delays using adiabatic constant-volume simulation and RCM simulation were compared, which indicated that RCM simulation could better predict the experimental data. Sensitivity and reac...

Formulation of Sasol Isomerized Paraffinic Kerosene Surrogate Fuel for Diesel Engine Application Using an Ignition Quality Tester

Sasol isomerized paraffinic kerosene (IPK) is a coal-derived synthetic fuel under consideration as a blending stock with jet propellant 8 (JP-8) for use in military equipment. However, Sasol IPK is a low ignition quality fuel with derived cetane number (DCN) of 31. The proper use of such alternative fuels in internal combustion engines (ICEs) requires the modification in control strategies to operate engines efficiently. With computational cycle simulation coupled with surrogate fuel mechanism, the engine development process is proved to be very effective. Therefore, a methodology to formulate Sasol IPK surrogate fuels for diesel engine application using ignition quality tester (IQT) is developed. An in-house developed matlab code is used to formulate the appropriate mixture blends, also known as surrogate fuel. And aspen hysys is used to emulate the distillation curve of the surrogate fuels. The properties of the surrogate fuels are compared to those of the target Sasol IPK fuel. The DCNs of surrogate fuels are measured in the IQT and compared with the target Sasol IPK fuel at the standard condition. Furthermore, the ignition delay, combustion gas pressure, and rate of heat release (RHR) of Sasol IPK and its formulated surrogate fuels are analyzed and compared at five different charge temperatures. In addition, the apparent activation energies derived from chemical ignition delay of the surrogate fuel and Sasol IPK are determined and compared.

Experimental Study of the Combustion of Kerosene and Binary Surrogate in the Model Combustion Chamber

The purpose of this paper is to conduct experimental research of hazardous substance emissions at the simulated combustion chamber output. The experiment was carried in a simulated combustion chamber. The combustion chamber included a burner device; a liquid fuel feed system; and a flame tube with two rows of mixing holes and one row of cooling holes. The combustion chamber operation mode was φ = 0.435, Tpreheat = 423 K, and the atmospheric pressure. The liquid fuel burn rate was 0.77 g/s. The pressure ratio in the combustion chamber remained constant at ΔP = 3%. Two types of fuel were used: aviation kerosene of Russia’s TS-1 brand and the fuel surrogate was n-decane mixture (C10H22) with benzene additions (C6H6). The benzene additions were 5% through 30% (n-decane/benzene: 95/5, 90/10, 85/15, 80/20, 75/25, and 70/30).

Simulations of laminar non-premixed flames of kerosene with hot combustion products as oxidiser

The effects of hot combustion product dilution in a pressurised kerosene-burning system at gas turbine conditions were investigated with laminar counterflow flame simulations. Hot combustion products from a lean (φ = 0.6) premixed flame were used as an oxidiser with kerosene surrogate as fuel in a non-premixed counterflow flame at 5, 7, 9 and 11 bar. Kerosene-hot product flames, referred to as ‘MILD’, exhibit a flame structure similar to that of kerosene–air flames, referred to as ‘conventional’, at low strain rates. The Heat Release Rate (HRR) of both conventional and MILD flames reflects the pyrolysis of the primary and intermediate fuels on the rich side of the reaction zone. Positive HRR and OH regions in mixture fraction space are of similar width to conventional kerosene flames, suggesting that MILD flames are thin fronts. MILD flames do not exhibit typical extinction behaviour, but gradually transition to a mixing solution at very high rates of strain (above A = 160, 000 s−1 for all pressures). This is in agreement with literature that suggests heavily preheated and diluted flames have a monotonic S-shaped curve. Despite these differences in comparison with kerosene–air flames, MILD flames follow typical trends as a function of both strain and pressure. Further still, the peak locations of the overlap of OH and CH2O mass fractions in comparison with the peak HRR indicate that the pixel-by-pixel product of OH- and CH2O-PLIF signals is a valid experimental marker for non-premixed kerosene MILD and conventional flames.

Development of efficient and accurate skeletal mechanisms for hydrocarbon fuels and kerosene surrogate

In this paper, the methodology of the directed relation graph with error propagation and sensitivity analysis (DRGEPSA), proposed by Niemeyer et al. (Combust Flame 157:1760–1770, 2010), and its differences to the original directed relation graph method are described. Using DRGEPSA, the detailed mechanism of ethylene containing 71 species and 395 reaction steps is reduced to several skeletal mechanisms with different error thresholds. The 25-species and 131-step mechanism and the 24-species and 115-step mechanism are found to be accurate for the predictions of ignition delay time and laminar flame speed. Although further reduction leads to a smaller skeletal mechanism with 19 species and 68 steps, it is no longer able to represent the correct reaction processes. With the DRGEPSA method, a detailed mechanism for n-dodecane considering low-temperature chemistry and containing 2115 species and 8157 steps is reduced to a much smaller mechanism with 249 species and 910 steps while retaining good accuracy. If considering only high-temperature (higher than 1000 K) applications, the detailed mechanism can be simplified to even smaller mechanisms with 65 species and 340 steps or 48 species and 220 steps. Furthermore, a detailed mechanism for a kerosene surrogate having 207 species and 1592 steps is reduced with various error thresholds and the results show that the 72-species and 429-step mechanism and the 66-species and 392-step mechanism are capable of predicting correct combustion properties compared to those of the detailed mechanism. It is well recognized that kinetic mechanisms can be effectively used in computations only after they are reduced to an acceptable size level for computation capacity and at the same time retaining accuracy. Thus, the skeletal mechanisms generated from the present work are expected to be useful for the application of kinetic mechanisms of hydrocarbons to numerical simulations of turbulent or supersonic combustion.

RP-3 Aviation Kerosene Surrogate Fuel and the Chemical Reaction Kinetic Model

RP-3 Aviation Kerosene Surrogate Fuel and the Chemical Reaction Kinetic Model

Study on the Effects of Hydrogen Addition on Ignition Delay of Surrogate Fuel for RP-3 Kerosene

In order to reduce the emission and realize the sustainable development in aviation industry, looking for alternative fuel as kerosene has become more and more important. Hydrogen is regarded as one of the most promising alternative fuels. In our study RP-3 kerosene with hydrogen addition is used as the alternative kerosene. A RP-3 kerosene surrogate includes n-decane, toluene and propyl cyclohexane (volume fraction is 0.65/0.1/0.25) was chosen and the ignition delay times are calculated in CHEMKIN-PRO, it is found that hydrogen addition can shorten ignition delay.

Simulation of self-ignition of aviation kerosene by a shock wave

The self-ignition of an aviation kerosene surrogate by a shock wave is studied. Based on the kinetic mechanisms of fuel surrogate combustion in air, the aviation kerosene ignition is numerically simulated. The shock wave parameters are determined. The induction time dependence on the gas temperature is obtained.

초임계 압력 조건 스월 인젝터에서 4개 화학종 혼합물 케로신 대체 모델의 열역학 물성 특성 연구

초임계 압력 조건 스월 인젝터에서 4개 화학종 혼합물 케로신 대체 모델의 열역학 물성 특성 연구

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.

Thermodynamic modeling based on a generalized cubic equation of state for kerosene/LOx rocket combustion

Based on a generalized cubic equation of state proposed by Cismondi and Mollerup [Fluid Phase Equilib. 232 (2005) 74–89], this study derived formulations for the thermodynamic properties of mixtures that are needed for combustion simulations of liquid rocket engines. The present model was validated thoroughly against reference data provided by NIST in order to assess its validity over a wide range of critical compressibility factors, pressures, and temperatures. The numerical results clearly indicate that the present model is superior in its handling of fluid mixtures with quite different critical compressibility factors, while maintaining the advantages of the cubic equation of state compared to those of the Soave–Redlich–Kwong and Peng–Robinson equations of state. In addition, steady flamelet analysis has been performed to investigate the effects of detailed chemical kinetics, real fluid behavior, and increased pressure on the local flame structures of the kerosene surrogate and liquid oxygen relevant to liquid rocket engines.

Soot predictions in premixed and non-premixed laminar flames using a sectional approach for PAHs and soot

A new soot model is presented, which has been developed for CFD applications, combining accuracy and efficiency. While the chemical reactions of small gas phase species are captured by a detailed chemical kinetic mechanism, polycyclic aromatic hydrocarbons (PAHs) and soot particles are represented by sectional approaches. The latter account for important mechanisms such as the formation of sections, their oxidation, the condensation of acetylene, and the collisions between sections. The model has been designed to predict soot for a variety of fuels with good accuracy at relatively low computational cost. Universal model parameters are applied, which require no tuning in dependence of test case or fuel. Soot predictions of ethylene, propylene, kerosene surrogate, and toluene flames are presented, which show good agreement with the experimental data. Furthermore, the importance of the correct choice for thermodynamic data of PAHs and soot is highlighted and the impact of heat radiation is discussed.

Skeletal mechanism generation for high-temperature oxidation of kerosene surrogates

A skeletal mechanism with 106 species and 382 reactions is developed from a detailed kerosene combustion chemical kinetic mechanism that includes 209 species and 1673 reversible reactions for a tricomponent surrogate mixtures, consisting of n-decane, n-propylcyclohexane, and n-propylbenzene. The directed relation graph (DRG) method for skeletal mechanism reduction is applied as the first step for reduction of mechanisms with large numbers of species. A revised DRG approach (Z.Y. Luo, T.F. Lu, et al., Energy Fuels 24 (2010) 6283–6293) is compared with the original one and it is shown to be more stable than the original DRG method. The simplified iterative screening and structure analysis method (ISSA) is used subsequently based on the reduced mechanism generated by the DRG method to remove redundant species and reactions simultaneously. A minimal skeletal mechanism from the detailed mechanism for kerosene combustion is thus obtained. It is found that the discrete local reaction rates rather than the time-averaged reaction rates should be adopted when using the ISSA method for mechanism reduction due to large temperature difference and different reaction pathways in combustion at different simulation conditions. Although reduced in size by a factor of 2 for species and a factor of 4 for reactions, the skeletal mechanism exhibits high accuracy for high-temperature applications in predicting global combustion parameters, such as ignition delay, detailed profiles of species concentrations, and laminar flame speed. Furthermore, numerical simulation results of different mixture compositions are also comparable with those based on the detailed mechanism, indicating that the major reaction pathways of each component are captured by the reduced mechanism and the hierarchical structure of the detailed mechanism is maintained.

Laminar flame speeds and extinction limits of conventional and alternative jet fuels

Experimental results of laminar flame speeds and extinction stretch rates for the conventional (Jet-A) and alternative (S-8) jet fuels are acquired and compared to the results from our earlier studies for neat hydrocarbon surrogate components, including n -decane and n -dodecane. Specifically, atmospheric pressure laminar flame speeds are measured using a counterflow twin-flame configuration for Jet-A/O 2 /N 2 and S-8/O 2 /N 2 mixtures at preheat temperatures of 400, 450, and 470 K and equivalence ratios ranging from 0.7 to 1.4. The flow field is recorded using digital particle image velocimetry. Linear extrapolation is then applied to determine the unstretched laminar flame speed. Experimental data for the extinction stretch rates of the nitrogen diluted jet fuel/oxidizer mixtures as a function of equivalence ratio are also obtained. In addition, the experimental data of Jet-A are compared to the computed values using a chemical kinetic mechanism for a kerosene surrogate reported in literature. A sensitivity analysis is further performed to identify the key reactions affecting the laminar flame speed and extinction stretch rate for this kerosene surrogate.

Synthetic and jet fuels pyrolysis for cooling and combustion applications

Large heat load are encountered in hypersonic flight applications due to the high vehicle speed (over Mach 5, i.e. 5000 km h −1) and to the combustion heat release. If passive and ablative protections are a way to ensure the thermal management, the regenerative cooling is probably the most efficient one to enable the structures withstanding (notably for reusable structures). The present study is a part of COMPARER project (COntrol and Measure of PArameters in a REacting stReam) which aims at investigating the highly coupled phenomenon (heat and mass transfers, pyrolysis, combustion) in a cooling channel surrounding a SCRamjet combustion chamber and at proposing some parameters to enable the control of such a complex technology. In this paper, we present the comparative numerical pyrolysis study of some selected synthetic and jet fuels (heptane, decane, dodecane, kerosene surrogate). The fluid pyrolysis has been studied experimentally and the results of RESPIRE numerical simulation under lab and in-flight conditions are given with validation to provide a deep understanding of phenomenon. The impact of the density, of the critical parameters, of the viscosity and of the chemistry is investigated to analyze their effect on the cooling efficiency of the engine. That also enables to estimate properties which the best cooling fuel should have. Furthermore, a combustion study is conducted because the cooling fuel is the one that ensure the thrust. The RESPIRE code enables to conduct both coupled pyrolysis and combustion studies. A first approach of the dynamic regeneratively cooled SCRamjet is provided to get a large vision of the fuel nature impact on the system.