Combustion is directly related to energy conversion and the environment. Gas-phase chemical reactions such as thermal decomposition, oxidation and recombination play a critical role in combustion processes. Here we review six applications of synchrotron vacuum-ultraviolet (VUV) photoionization mass spectrometry (PIMS) in fundamental studies of combustion chemistry. These applications range from the use of flow reactors to probe elementary reaction kinetics, studies of pyrolysis in plug-flow reactors and oxidation in jet-stirred reactors, studies of spatial evolution of species concentrations in premixed and non-premixed flames, product distributions in pyrolysis of biomass, and analysis of polycyclic aromatic hydrocarbon (PAH) formation. These experiments provide valuable data for the development and validation of detailed chemical kinetic models. Furthermore, some additional potential applications are proposed.

Combustion chemistry probed by synchrotron VUV photoionization mass spectrometry

Soot formation in laminar counterflow flames

A review of cavity-based trapped vortex, ultra-compact, high-g, inter-turbine combustors

Research progress on strut-equipped supersonic combustors for scramjet application

n-Butanol pyrolysis in a flow reactor was investigated at the pressures of 5, 30, 80, 200, and 760 Torr. Synchrotron vacuum ultraviolet photoionization mass spectrometry was used for the identification of pyrolysis species and the measurement of their mole fractions. A detailed kinetic model consisting of 121 species and 658 reactions was developed to simulate the n-butanol pyrolysis. To enhance the accuracy of the model, the rate constants of unimolecular reactions of n-butanol and β-scission reactions of four n-butanol radicals (C4H8OH) were calculated with the variable reaction coordinate–transition-state theory (VRC–TST) and the Rice–Ramsperger–Kassel–Marcus (RRKM) theory coupled with the master equation method. These rates are very sensitive to the mole fractions of pyrolysis species and have been well-validated by the pyrolysis experiment. The model was further validated by the low-pressure premixed flames at different equivalence ratios, oxidation data from the jet-stirred reactor, and ignition del...

Experimental and Kinetic Modeling Study of n-Butanol Pyrolysis and Combustion

An experimental and kinetic modeling study of cyclohexane pyrolysis at low pressure

To explore the combustion performance of nonrectangular supersonic combustors, the flow and combustion characteristics in the round and round-to-elliptic shape-transition scramjet combustors were c...

https://arc.aiaa.org/doi/pdf/10.2514/1.B36721

Comparative Study of Elliptic and Round Scramjet Combustors Fueled by RP-3

Improved delayed detached Eddy simulation (IDDES) modeling based on a developed skeletal combustion mechanism of kerosene/air is conducted for a full-scale actively cooled scramjet combustor under two different global equivalence ratios. A reformulated partially stirred reactor (PaSR) is proposed to adapt it for high mesh resolution. A skeletal mechanism consisting of only 28 species and 92 reactions is reduced for the kerosene combustion modeling. A one-dimensional solid-gas-liquid coupling method is developed to simulate the active cooling effect. The time-averaged static pressure and wall heat flux profiles are well predicted for both fuel-lean and stoichiometric cases. The supersonic flow, mixing, and combustion characteristics under the two fuel/air ratios are quantitatively compared based on the efficiency indices, Takeno Flame Index, and the correlation statistics between heat release rate and mixture fraction. The vorticity and its evolution are analyzed through the five source terms for the two cases. The turbulence-chemistry interaction is then analyzed by the aid of numerous quantitative indices, such as Damkohler number, PaSR coefficient, and scalar dissipation rate, as well as their correlation statistics to identify the main combustion modes in the scramjet combustor.

https://arc.aiaa.org/doi/pdf/10.2514/1.B36866

Modeling Analysis of an Actively Cooled Scramjet Combustor Under Different Kerosene/Air Ratios

Large Eddy Simulation (LES) of kerosene fueled scramjet combustor is generally scare in the literature, due mainly to the formidable computational cost arisen by complex kerosene mechanism. In this study, the skeletal reduction of a detailed reaction mechanism (2185 species/8217 steps) of aviation kerosene is conducted using directed relation graph with error propagation and sensitivity analysis (DRGEPSA) method, resulting a skeletal mechanism consisting of 39 species/153 elemental reactions for China Daqing RP-3 aviation kerosene. The comparisons of adiabatic flame temperature, total heat release, ignition delay and laminar flame speed predicted by the skeletal mechanism show an overall good accordance with the original detailed reaction mechanism. Then a three-dimensional Detached Eddy Simulation (DES) modeling based on the skeletal kerosene mechanism is employed for the numerical analysis of a full-scale scramjet combustor, which has been experimentally tested in a long-time direct connect supersonic combustion test platform (abbreviated as DTZ) assembled in Chinese Academy of Sciences (CAS). Pressure and heat flux measurement systems are attached to the combustor assembly to monitor the real-time combustion performance and provide validation data for the numerical modeling. Three cases with fuel equivalence ratios from 0.8, 1.0 to 1.2 and the same crossflow conditions at Mach 2.0 are modeled. The time-averaged static pressure and heat flux are in generally good agreement with the experiment with the peak heat flux slightly underpredicted. The instantaneous and/or time-averaged pressure, momentum, temperature and turbulence fields, which are difficult to be measured, are analyzed to reveal the main flow and combustion physics, especially those related to the flame distribution and holding. The combustion is identified as in ramjet mode for the investigated cases. With the increasing of fuel equivalence ratio, the shock train propagates upstream in the isolator and the interaction between the upstream and downstream combustion assumes different patterns. c 2015, AIAA American Institute of Aeronautics and Astronautics. All rights reserved.(132 refs)

Full-scale Detached Eddy Simulation of kerosene fueled scramjet combustor based on skeletal mechanism

Blowout limits of cavity-stabilized flame of supercritical kerosene were experimentally studied by using Mach 2.5 and 3.0 direct-connect supersonic model combustors operated under various air and fuel conditions. Specifically, the effects of the stagnation temperature and the stagnation pressure on the blowout limits were investigated for supercritical kerosene injected from the wall upstream of a cavity flameholder in a Mach 2.5 combustor. Experiments were performed under the same conditions for supercritical kerosene injected from the rear part of the cavity bottom to study the influence of the location of fuel injection. The blowout limits of supercritical kerosene injected from the wall upstream of the cavity were further investigated in a Mach 3.0 combustor. Besides the effects of the stagnation temperature and stagnation pressure, the effect of the divergence angle of the combustor on the lean-fuel blowout limit was studied. Results show that there exist two blowout limits corresponding to the lean- and rich-fuel conditions for a given stagnation temperature. The location of fuel injection has substantial influence on the blowout limits, whereas the influence of the stagnation pressure and the divergence angle of the combustor can be neglected in the range of interest.

Jing Wang

Papers

An experimental and kinetic modeling study of cyclohexane pyrolysis at low pressure

Comparative Study of Elliptic and Round Scramjet Combustors Fueled by RP-3

Modeling Analysis of an Actively Cooled Scramjet Combustor Under Different Kerosene/Air Ratios

Full-scale Detached Eddy Simulation of kerosene fueled scramjet combustor based on skeletal mechanism

Blowout Limits of Cavity-Stabilized Flame of Supercritical Kerosene in Supersonic Combustors