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

Abstract

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.

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

“…AstroFoam, together with the original rhoCentralFoam solver, was first validated for various frozen flows, including the canonical shock tube problem, forward step flow, hypersonic flow over a biconic, and supersonic jets [11][12][13][14]. The solver is then applied to different types of scramjet combustor cases [15][16][17] to examine its accuracy and robustness in the engineering modeling of supersonic combustion.…”

“…The chemical mechanism reduction from the original detailed kerosene mechanism consisting of 2185 species and 8217 elementary reactions [25] is conducted using the DRGEPSA method [26], which is the combination of directed relation graph with error propagation (DRGEP) and sensitivity analysis (SA). In our previous study [15], a skeletal mechanism consisting of 39 species and 153 reactions is obtained. Further reaction path analysis and SA continue to reduce the mechanism into a smaller skeletal mechanism consisting of only 28 species and 92 reactions, which are listed in the Appendix.…”

Development of zone flamelet model for scramjet combustor modeling

“…In the serial studies conducted by the authors' group, the detailed kerosene mechanism proposed by Dagaut et al [56] is reduced under the typical working condition range of scramjet combustors, i.e. equivalence ratio of 0.6-1.4, static pressure of 0.5-3.0 bar, and static temperature of 300-3000 K. Till now, four versions of skeletal mechanisms, respectively 48s/197r [55], 39s/153r [53,54], 28s/92r [34] and current 19s/54r [57], have been developed from the original 2815s/8217r mechanism [56] by using a highly efficient and reliable directed relation graph with error propagation and sensitivity analysis (DRGEPSA) method [58] in together with manual path analysis. Although the mechanism size has been significantly reduced, the key kinetic properties such as adiabatic flame temperature, heat release rate, ignition delay and laminar flame speed agree well with the original detailed mechanism.…”

“…In this study, the latest version of reduced RP-3 mechanism with species number of 19 and reaction number of 54 will be used in the combustion models. The solver is then applied for various scramjet combustor cases [34,54] million for the elliptical combustor. In the following analysis, the coordinate origin locates at the lower left corner of the isolator inlet plane viewed from outside, with X, Y and Z respectively represent the streamwise, height and spanwise directions.…”

Development of Skeletal Kerosene Mechanisms and Application to Supersonic Combustion

“…In the serial studies conducted by the authors' group, the detailed kerosene mechanism proposed by Dagaut et al 3 is reduced under the typical working condition range of scramjet combustors, i.e., equivalence ratio of 0.7-1.5, static pressure of 0.5-3.0 bar, and static temperature of 300-3000 K. In those mechanisms, kerosene is surrogated by three components: 28.8% iso-octane, 62.4% n-decane, 8.8% n-O 3 propylcyclohexane in mass fraction. Till now, five versions of skeletal mechanisms, respectively 89s/668r, 48s/197r 23 , 39s/153r 24 , 28s/92r 25 and 19s/54r 26 , have been developed from the original 2815s/8217r mechanism 3 by using a highly efficient and reliable Directed Relation Graph with Error Propagation and Sensitivity Analysis (DRGEPSA) method 27 in combination with manual path analysis. A comprehensive validation of the different versions of skeletal mechanisms and a sensitivity analysis of the chemical mechanisms on the supersonic combustion characteristics would be beneficial for improving the credibility of supersonic combustion modelings.…”