Xinyu Chang

Simultaneous measurements of multiple flow parameters for scramjet characterization using tunable diode-laser sensors

This paper reports the simultaneous measurements of multiple flow parameters in a scramjet facility operating at a nominal Mach number of 2.5 using a sensing system based on tunable diode-laser absorption spectroscopy (TDLAS). The TDLAS system measures velocity, temperature, and water vapor partial pressure at three different locations of the scramjet: the inlet, the combustion region near the flame stabilization cavity, and the exit of the combustor. These measurements enable the determination of the variation of the Mach number and the combustion mode in the scramjet engine, which are critical for evaluating the combustion efficiency and optimizing engine performance. The results obtained in this work clearly demonstrated the applicability of TDLAS sensors in harsh and high-speed environments. The TDLAS system, due to its unique virtues, is expected to play an important role in the development of scramjet engines.

Thrust and drag of a scramjet model with different combustor geometries

Many efforts have been made to improve performance of scramjets (1-4). For this purpose cavities and struts were frequently used as the functions of mixing enhancement and flame stabilization. The present work focused on the effects of different strut and cavities on the thrust and drag of a side-wall compression scramjet model. This model consisting of a side-wall compression inlet, a combustor and a thrust nozzle and fueled by kerosene was tested in a propulsion tunnel that typically provides the testing flow with Mach number of 5.8, total temperature of 1800K, total pressure of 4.5MPa and mass flow rate of 4kg/s(5). A strut was used to increase the contraction ratio and to inject fuels, as well as a mixing enhancement device. Several wall cavities were also employed for flame-holder. The experimental results show that the cavities do not produce significant drag, but improve thrust performance well. It is found that the strut functions as an isolator and also helps the mixing enhancement, resulting in the improvement of the thrust performance. However the strut causes big drag to the scramjet model. Copyright

Combined TDLAS and OES technique for CO concentration measurement in shock-heated Martian atmosphere

This paper describes the CO concentration and gas temperature distribution measurements behind a strong shock wave in the simulated Martian atmosphere by an optical diagnostic system. The strong shock wave (6.31 ± 0.11 km/s) is established in a shock tube driven by combustion of hydrogen and oxygen. The optical diagnostic system consists of two parts: the optical emission spectroscopy (OES) system and the tunable diode laser absorption spectroscopy (TDLAS) system. For OES system, high temporal and spatial resolution experimental spectra of CN violet system (B2Σ+→X2Σ+, v = 0 sequence) have been observed. Rotational and vibrational temperature distribution along the shock wave is inferred through a precise analysis of high-resolution experimental spectra. For TDLAS system, a CO absorption line near 2335.778 nm is utilized for detecting the CO concentration using scanned-wavelength direct absorption mode. Combined with these experimental results using OES, CO concentration in the thermal equilibrium region is derived. The detected average CO concentration is 7.46 × 1012 cm-3 with the average temperature of 7400 K ± 300 K, which corresponds to the center fractional absorption of 2.7%.

Flow-field of the Excited Jet and Mixing in the Supersonic Flow

The planar laser scattering and gas sampling were used to investigate the mixing of the excited CO2 jet into the supersonic flow in this article. The jet was from the HartmannSprenger tube, which was put into the traditional jet device. The jet was excited at three different frequencies and compared with the base case without excitation. The results shown that the better mixing with less total pressure loss could be obtained in the excited cases. The penetration was the deepest for 900Hz-excited jet while the number of the large-scale structures was the most in the 5 kHz-excited case. The excited jet didn’t only take effects on the jet shear layer, but also in fluenced the boundary layer.

Performance of the fuel injector in supersonic combustor

Enhancing the fuel-air mixing is critical for scramjet combustor performance. The performance of four different aerodynamic ramp injectors was reported in this paper. The experiments were conducted in a direct-connected scramjet test facility. The concentration profiles were obtained by gas sampling and chromatogram analysis. The pictures of the flow field were obtained by using laser scatter. It would be used to analyze the flow field generated by the aerodynamic ramp, then optimize the layout of the injectors. The results would offer some useful information for engine design.

Experimental Study of Strut Parameters Effects on Performances of Scramjet Combustor

An experimental investigation of strut parameters for enhancing supersonic mixing and combustion had been carried out on direct-connect supersonic combustion test facility. The wall static pressure, gas sampling analysis system, CH* chemiluminescence imaging and the schlieren system were used to research the effect of different strut parameters. This paper uses the method of orthogonal experimental method, parametric modeling of strut configurations was performed by the orthogonal design with 5 factors at 3 levels. Undisturbed length and combustion efficiency were set as objective functions of combustion performance of scramjet combustor. The results are as follows: For combustion efficiency of scramjet, the order of significance levels of the strut factors in turn decreases on jet, height, distance, equivalence ratios and thickness of strut respectively. For undisturbed length of scramjet, the order of significance levels of the strut factors in turn decreases on respectively equivalence ratios, jet, height, thickness, and distances of strut. The higher the strut is, the deeper fuel mixing and combustion area are in the mainstream, the shorter and narrower the flames are, the greater the intensity and efficiency of combustion are. As the height of strut increases from 10mm to 30mm, the combustion efficiency increased accordingly by 15.1%. Meanwhile, moderate distance between strut and cavity can help to improve combustion performance of strut.