Nonlinear saturation amplitude of cylindrical Rayleigh Taylor instability

The nonlinear saturation amplitude （NSA） of the fundamental mode in the classical Rayleigh-Taylor instability with a cylindrical geometry for an arbitrary Atwood number is analytically investigated by considering the nonlinear corrections up to the third order. The analytic results indicate that the effects of the initial radius of the interface （r0） and the Atwood number （A） play an important role in the NSA of the fundamental mode. The NSA of the fundamental mode first increases gently and then decreases quickly with increasing A. For a given A, the smaller the ro/λ（λ is the perturbation wavelength）, the larger the NSA of the fundamental mode. When ro/λ is large enough （r0 〉〉 λ）, the NSA of the fundamental mode is reduced to the prediction in the previous literatures within the framework of the third-order perturbation theory.

The vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of kerosene

In ground tests of hypersonic scramjet, the highenthalpy airstream produced by burning hydrocarbon fuels often contains contaminants of water vapor and carbon dioxide. The contaminants may change the ignition characteristics of fuels between ground tests and real flights. In order to properly assess the influence of the contaminants on ignition characteristics of hydrocarbon fuels, the effect of water vapor and carbon dioxide on the ignition delay times of China RP-3 kerosene was studied behind reflected shock waves in a preheated shock tube. Experiments were conducted over a wider temperature range of 800-1 500 K, at a pressure of 0.3 MPa, equivalence ratios of 0.5 and 1, and oxygen concentration of 20%. Ignition delay times were determined from the onset of the excited radical OH emission together with the pressure profile. Ignition delay times were measured for four cases： （1） clean gas, （2） gas vitiated with 10% and 20% water vapor in mole, （3） gas vitiated with 10% carbon dioxide in mole, and （4） gas vitiated with 10% water vapor and 10% carbon dioxide, 20% water vapor and 10% carbon dioxide in mole. The results show that carbon dioxide produces an inhibiting effect at temperatures below 1 300 K when Ф = 0.5, whereas water vapor appears to accelerate the ignition process below a critical temperature of about 1 000 K when Ф = 0.5. When both water vapor and carbon dioxide exist together, a minor inhibiting effect is observed at Ф = 0.5, while no effect is found at Ф = 1.0. The results are also discussed preliminary by considering both the combustion reaction mechanism and the thermophysics properties of the fuel mixtures. The current measurements demonstrate vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of China RP-3 kerosene at air-like O2 concentration. It is important to account for such effects when data are extrapolated from ground testing to real flight conditions.

Thermal cracking of aviation kerosene for scramjet applications

Thermal cracking of China No.3 aviation kerosene was studied experimentally and analytically under supercritical conditions relevant to regenerative cooling system for Mach-6 scramjet applications. A two-stage heated tube system with cracked products collection/analysis was used and it can achieve a fuel temperature range of 700―1100 K,a pressure range of 3.5―4.5 MPa and a residence time of ap-proximately 0.5―1.3 s. Compositions of the cracked gaseous products and mass flow rate of the kerosene flow at varied temperatures and pressures were obtained experimentally. A one-step lumped model was developed with the cracked mixtures grouped into three categories:unreacted kerosene,gaseous products and residuals including liquid products and carbon deposits. Based on the model,fuel conversion on the mass basis,the reaction rate and the residence time were estimated as functions of temperature. Meanwhile,a sonic nozzle was used for the control of the mass flow rate of the cracked kerosene,and correlation of the mass flow rate gives a good agreement with the measurements.

Theoretical solutions to three-dimensional asymmetrical shock/shock interaction

这份报纸探索理论答案到三维(3D ) 不均匀的交叉压缩在超声的 inviscid 挤的 3D 导致的吃惊 / 吃惊相互作用流动。为马赫相互作用，作为空间尺寸的减小知道的一个分析方法，它转变 3D 的问题稳定的吃惊 / 吃惊相互作用进一二维(2D ) 生气的节上的伪 steady 问题，被用来在马赫茎的附近获得答案。理论答案包括压力，温度，密度，在马赫茎后面的马赫数字，和全部的压力恢复系数。数字模拟被执行验证理论结果。这里， NND 计划被解决 3D inviscid Euler 方程采用，并且好协议被获得。流动特征的不对称现象由楔角度导致了并且扫角度彻底地被讨论。