Investigation On The Injection And Combustion Characteristics Of Vaporized Kerosene In Supersonic Flow

The present study, focusing on the injection and combustion characteristics of vaporized kerosene in supersonic flows, investigated the supersonic flow characteristics of vaporized RP-3(China No.3 aviation kerosene), the transverse injection, flameholding and combustion characteristics of vaporized RP-3 in supersonic flows both experimentally and numerically.Based on the one-dimensional isentropic flow assumption and the extended corresponding states principle, the supersonic flow characteristics of the supercritical and gaseous RP-3 were analyzed with the 3-component surrogate and 10-component surrogate of RP-3. Subsequently, a series of tests were conducted to investigate the supersonic flow characteristics of supercritical, gasous and thermal cracked RP-3. Based on the static pressure distributions along the supersonic injector wall, the experimental results and calculated results of the 3-component surrogate and 10-component surrogate were compared and discussed. It is found that when the test conditions approaching the pseudo-critical point of RP-3, the experimental results and calculated results of the two surrogate models both had large discrepancies; Modifying the calculation method to let RP-3 and its surrogate fuels have the same corresponding temperature Tcr(Tcr=T/Tc, temperature nominalized by the critical temperature) and corresponding pressure Pcr, calculated accuracies of the two surrogate models were both remarkably improved. With the test condition departing from the pseudo-critical point, the gap of the experimental results and calculated results of the two surrogate models was both rapidly narrow; Then, the modification method had a weak effect on the calculated results.Based on the one-dimensional isentropic flow assumption, the mass flow rate of supercritical and gaseous RP-3 with flow choking was analysed with the 3-component surrogate and 10-component surrogate. The calculated results of the two surrogate models were verified by a series of tests. The results indicated that the modified 3-component surrogate exhibited the least error.The penetration depth of the supercritical RP-3 injected into a supersonic cross flow was investigated using high speed camera and pulsed laser schlieren system. As supercritical RP-3 has a lower dynamic pressure ratio, the penetration depth of the supercritical RP-3 is smaller than that of ethylene. The effects of the injection angle and fuel temperature on the penetration depth of supercritical RP-3 were also investigated. Additionally, the supersonic injection characteristics of supercritical RP-3 were analyzed with the modified 10-component surrogate, and found that the vaporized RP-3 has the highest dynamic pressure ratio when Ma≈1.4.The combustion characteristics in a single-side-expansion supersonic model combustor with gaseous ethylene injection upstream of dual parallel cavities were investigated experimentally and numerically. Based on the static pressure distributions along the combustor wall, high-speed flame luminosity and schlieren images, the flame structure and flowfield characteristics under different combustion modes were analyzed and compared. The results showed that two clusters of separated and asymmetric flames were found to be stabilized near the dual parallel cavities in all tests. The flame and flow characteristics changed with the combustion modes. For scramjet mode, no obvious flow separation occurred near the walls and the two flames were both stabilized in the cavity shear layer and recirculation zone. For ramjet mode, the high back pressure resulting from intense heat release induced a large-scale recirculation zone upstream of the cavity mounted on the expanded wall, which supplied a favorable combustion condition and the flame was stabilized in the jet-wake. Meanwhile, there was no obvious separation near the horizontal wall, with the local flame stabilized in the cavity shear layer. There exist competitive and cooperative effects between the two opposite flames. The joint interactions of the two effects ultimately decide the combustion characteristics in the supersonic combustor.Adopting the vaporized RP-3, ethylene, ethylene –methane mixture, methane and liquid RP-3, the effects of phase change and fuel compositions variation on the lean blowout limit in a supersonic model combustor with dual parallel cavities were investigated experimentally. The experimental results demonstrated that the gaseous RP-3 which omitting the atomization and evaporation process has a lower lean blowout limit than the liquid RP-3. Compare to the vaporized RP-3 and methane, higher active fuel, such as the ethylene and ethylene –methane mixture, decreased the lean blowout limit. The flame of ethylene and ethylene –methane mixture could hold itself both under the scramjet mode and ramjet mode, while the flame of the vaporized RP-3, methane and liquid RP-3 couldn’t hold itself under the scramjet mode. The cracking of RP-3 also improved its flameholding performance.To investigate the effect of phase change and fuel compositions variation resulting from cracking on the combustion characteristics of supersonic combustors, a series of combustion tests were conducted under a wide range of equivalence ratios. The combustion characteristics of room temperature ethylene, vaporized RP-3 with negligible cracking and liquid RP-3 were analyzed and compared based on the measured static pressure distributions along the combustor wall, fuel specific impulses, flame luminosity images and the one-dimensional average flow parameter distributions calculated by a quasi-one-dimensional data analysis method. The experimental results indicated that the differences between the combustion characteristics of vaporized RP-3 and ethylene were sensitive to equivalence ratio. Under low equivalence ratios, vaporized RP-3 and ethylene had remarkably different combustion characteristics. Ethylene had an obvious higher static pressure level, specific impulse and combustion efficiency than vaporized RP-3 for its higher activity. The difference of combustion performance between vaporized RP-3 and ethylene was narrowed with the increase of equivalence ratio and the corresponding combustion condition improvement. When the equivalence ratio increased to 1.09, vaporized RP-3 and ethylene had tiny difference in combustion performance. The difference of combustion characteristics between vaporized RP-3 and liquid RP-3 was also narrowed with the increase of equivalence ratio.A series of supersonic combustion tests were conducted to investigate the supersonic combustion characteristics of vaporized RP-3 and ethylene under different cavity arrangement schemes. The results indicated that the cavity arrangement schemes have great impacts on the flame distribution, heat release characteristic and combustor performance. And the effects of the cavity arrangement schemes changed with the fuel properties and equivalence ratios.