Papers by Author: Xin Long Chang

Abstract: In this paper, the detail numerical simulations were performed on the flow field of the scramjet combustor chamber with the hydrogen fuel, when the cavity parameters changed. The research results indicate that the effect of gas and air mixing and flame stability are altered when the parameter of cavity changed. From the research we will better understand the supersonic combustion. The high efficiency flame stabilities can be designed in future.

Abstract: In this paper, the detailed numerical simulations were performed in the hydrogen fuel combustion chamber with some different structure cavities. Through the analysis found that the effect of stabilized fire burning at supersonic flowing and mixed fuel and air are quite different. The research results will preferably represent the burning field in scramjet combustion so that the better performance flame stabilizer can be designed.

Abstract: In virtue of Fluent of CFD software, numerical computations of aerodynamics of an air-to-air missile in different mach numbers and different attack angles were carried though. The movement trends of lift coefficient, drag coefficient and pitching moment coefficient with variety of mach numbers and attack angles were gained, meanwhile, distributing trends of pressure, temperature and weather velocity were also obtained. The results indicated that the basis and references could be offered by numerical computation results for shape design of missile and definite preponderances were showed than traditionary numerical computation methods.

Abstract: With the support of powerful calculation ability of computer and Fluent of CFD software, integrative simulation research of the variable thrust liquid propellant rocket engine was developed. Numerical simulation of interior flow field of a variable thrust rocket engine with flux-oriented injector was done. The distributions of pressure, temperature, molar fraction of product and flow mach numbers were attained. By the contrast of the calculation results, the effects of structure parameters and working condition etc. on total whole performance of variable thrust rocket engine were analyzed. The results also provided theoretic references for design and optimization of variable thrust rocket engine.

Abstract: With increasing application of adhesive bonding structures, the quality assessment of adhesive bonding became critical. Ultrasonic approach was an acknowledged promising method in many Nondestructive testing (NDT) techniques. The research object was to use analytical models to develop a quantitative understanding of the affections in different situations on the dispersion properties. An improved global matrix method was introduced to compute the dispersive curves, which can effectively eliminate the instability for thicker layers and higher frequencies. In order to evaluate the disbond defect, the cohesive strength degradation mode and the spring mode were then adopted to describe the cohesive failure and the interface failure, respectively. In the paper, cohesive failure, interface failure and mixed failure were analyzed for the steel/adhesive layer/insulation layered structure. Interface failure induced the modes of multilayer structure to regress to the modes of single layers, while the cohesive failure made the dispersive curves move to the lower frequency direction, and changing the relative position of spring layer led the dispersive curves shift to the higher frequency direction. Among all the factors, the interface failure was dominant. Finally, the variety of the dispersive modes in a special frequency band (1~1.5MHz) was found that can be regarded as parameters of the adhesive bonding quality.

Abstract: This paper is devoted to studying influences of matrix/particle interface debonding and particulate size in micromechanical predictions of the effective moduli of particulate reinforced polymer composites (PRPC). The PRPC is regarded as a three-phase composite that includes the matrix, particle and interphase. The formulation for the effective moduli of the interphase is derived by the cohesive zone model, and combined with the Mori-Tanaka method, the micromechanical model for the effective moduli of the PRPC is formulated with emphasis on the effects of the matrix/particle interface, particulate size and volume fraction. The numerical example shows that the interface debonding, the particulate size and volume fraction have significant influences on the effective moduli of PRPC. The effective moduli of the PRPC can be used to characterize its damage degree.

Abstract: The fiber reinforced composite materials were widely used for aerospace aircrafts and missile weapons, and the delamination was a major problem which reduced the structural integrity and reliability of the solid rocket motor (SRM) composite shell seriously. In order to locate the delamination damage, the fiber Bragg grating (FBG) strain sensors network was embedded in SRM shell, and a multi-step approach of delamination damage location based on strain energy was performed: the strain field was measured in a scatter grid by the FBG strain sensors network in hydraulic testing; then the continuous displacement and strain field was reconstructed with relative sensors data using a moving least square (MLS) mesh-free fitting method; the strain energy of each subregions was calculated from the reconstructed data; finally the damaged subregions was identified successfully by singularity value of strain energy. The results of simulation and experiment indicated that the damage identification and location only required the measure of strain field of the SRM shell, and the presented approach achieved higher accuracy.