Effect of injection scheme on asymmetric phenomenon in rectangular and circular scramjets

The asymmetric separation has a crucial effect on the performance of the scramjet.In this study,the asymmetric separation and combustion in both rectangular and circular scramjets are investigated numerically,and the effect of injection scheme is analyzed.The characteristics of the flow field are analyzed based on sufficient code verification.In the rectangular scramjet,the separation tends to occur in the corner due to the corner boundary-layer effect.The separation is asym-metric and only two corners have serious separation.The fuel penetration depth in the separation zone increases and the combustion is intensified.When the injection scheme is uniform,both the combustion and separation become weak.In the circular scramjet,the separation and combustion are basically axisymmetric in the scramjet with one-row injection scheme.The asymmetric combustion becomes obvious in cases with multi-row injection scheme.When the injection orifices distribute intensively on the top and bottom sides,the strongest and weakest separations occur near these two sides respectively.When the distribution of orifices becomes uniform,the direction of separation cannot be predicted.For multi-row cases,the nonuniform injection scheme could result in violent combustion and asymmetric flow structures compared with the uniform injection scheme.

Numerical research on mixing characteristics of different injection schemes for supersonic transverse jet

A numerical method using AUSMDV scheme and k-ω SST turbulence model with an explicit compressibility correction was developed,and a 3-D numerical simulation of a supersonic flow field with a vertical sonic jet of hydrogen was performed.Good agreement between numerical results and experimental data validated the reliability of the numerical method.Whereafter,two parameters,mass-weighted average total pressure and mixing efficiency,were defined to evaluate the mixing performance of different injection schemes.Based on the numerical method and evaluation criterion,the mixing characteristics of different injection schemes were studied in detail.It was found that for the mixing field of supersonic transverse jet,the near-field mixing is controlled by convection transport while the far-field mixing is controlled by mass diffusion;the circular-hole injection causes a loss of total pressure comparable to the slot injection,but can induce a much higher mixing efficiency because of its 3-D flow characteristic;the variation of injection angle under circular-hole injection mainly affects the near-field mixing degree,and among the five injection angles studied in the present paper,angle 120° is the optimal one;with the increase of the ratio between injector space and diameter,the induced mixing efficiency increases while the caused loss of total pressure can grow greatly;the two-stage injection method designed through reducing the injector area to keep the same hydrogen mass flowrate can induce a much higher mixing efficiency while only a bit larger loss of total pressure when compared to the single-stage injection,and hence the two-stage injection is superior to the single-stage injection.The research results can direct the design of the fuel injection method in the combustor of scramjet engine.

A Tunable Dual-Wavelength Fiber Ring Laser with a Fabry-Perot Laser Diode in an External Injection Seeding Scheme

A tunable dual-wavelength fiber ring laser with a Fabry-Perot laser diode is proposed and demonstrated. The dual-wavelength outputs have the optical side-mode-suppression-ratio (SMSR) over 31 dB. The wavelength tuning range can be up to 9 run.

NUMERICAL SIMULATION AND FIELD IMPLEMENTATION OF SURFACTANT FLOODING

Based on the features of surfactant flooding, a mathematical model for surfactant flooding is established. The adsorption-retentlon, convection diffusion of surfactant and influence of concentration change upon relative permeability curve are included in the model. The novel description of adsorption quantity of surfaetant and relative permeability curve are presented, which enhance the coincidence between mathematical model and field practice, the relative errors of main development indexes arc within 6%. The model is applied to the numerical research of the surfactant flooding in the untabulated beds of Xingl-3 surfactant flooding pilot site of No. 4 Oil Production Company of Daqing Oilfield, the influences of surfaetant concentration, injection quantity, slug combination mode upon the development effect and economic benefit are quantitatively analyzed, the injection scheme is optimized as follows： surfaetant concentration is 0.5%, slug volume is 0.02 PV, slug combination mode is 2 slugs. After the implementation of scheme in oilfield, the cumulative increase of oil is 2186.0 t, up to nearly 30%.