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821.
822.
气体状态方程对正十二烷射流燃烧的影响 总被引:1,自引:1,他引:0
选取正十二烷作为航空煤油的替代燃料,应用大涡数值模拟方法和详细化学反应动力学相结合的方法对该燃料在超临界环境下的射流燃烧进行计算,研究其射流、燃烧及排放特性。重点考察了气体状态方程对射流形态、贯穿距、温度、混合分数等的影响。结果表明:理想气体和真实气体状态方程对仿真得到的射流贯穿距和宏观形态影响不大,而真实气体状态方程可以更好地反映在超临界环境下的液体燃料射流内部特征,如混合分数、温度;燃烧方面,仿真的点火延迟与实验存在10%的误差,火焰浮起长度、火焰形态、碳烟等均得到很好的预测,NOx与OH分布与温度场具有高度一致性。 相似文献
823.
徐友良 《长沙航空职业技术学院学报》2009,9(3):66-70
本文按塑性力学方法,在求解位置建立坐标系,在充分考虑了大变形和材料硬化因素的影响下,提出了一个轴对称金属塑性大变形问题的理论模型。 相似文献
824.
《中国航空学报》2021,34(5):298-314
A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine. This paper proposes a cold gas flow experimental system based on a rotary valve and a corresponding rotation model. A 3D numerical model is proposed to obtain the transient flow inside the rotary valve, and the dynamic mesh technique and User-Defined Functions (UDFs) are adopted to implement a swing motion instead of a rotary motion. Several cold gas flow experiments are carried out at rotating speeds of 75 225, and 375 rpm to verify the validity of the numerical model. The effects of rotating speed, stroke length ratio and radius of the RED (Rotor Exhaust Duct) on the pressure oscillations are studied using this numerical model. The results show that the maximum and peak-to-peak values of the pressure oscillations gradually decrease with increasing rotating speed. The ratio of the corresponding peak-to-peak value to the maximum pressure (pressure amplitude ratio) is reduced from 1.81 to 0.6%. The stroke length ratio affects the pressure waveform because it leads to a change in the time spent in the non-exhaust stage. When the stroke length ratio is 0, the waveform closely resembles a sine wave. With the increase in the stroke length ratio, the pressure waveform exhibits a more square or a triangular wave shape. Finally, a high-frequency and high-amplitude pressure oscillation can be obtained by appropriately increasing the radius of the RED. 相似文献
825.
Petr Ammosov Galina GavrilyevaAnastasia Ammosova Igor Koltovskoi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
OH(6-2) rotational temperature trends and solar cycle effects are studied. Observations were carried out at the Maimaga station (63.04°N, 129.51°E) for the period August 1999 to March 2013. Measurements were conducted with an infrared spectrograph. Temperatures were determined from intensity ratios in the P branch of the OH band. The monthly average residuals of temperature after the subtraction of the mean seasonal variation were used for a search for the solar component of temperature response. The dependence of temperatures on solar activity has been investigated using the Ottawa 10.7 cm flux as a proxy. A linear regression fitting on residual temperatures yields a solar cycle coefficient of 4.24 ± 1.39 K/100 solar flux units (SFU). The cross-correlation analyses showed that changes of the residual temperature follow changes of solar activity with a quasi-two year delay (25 months). The temperature response at the delay of 25 months reaches 7 K/100 SFU. The possible reason of the observed delay can be an influence of quasi-biennial oscillations (QBO) of the atmosphere on the relation of temperature and solar activity. The value of the temperature trend after the subtraction of seasonal and solar components is not statistically significant. 相似文献
826.
基于自适应小波配点法和人工黏性,构造了二维激波问题的小波数值计算格式。利用最细尺度的小波系数构造两组激波定位函数,分别用以控制两个正交方向人工黏性的大小和分布。对三类二维激波问题进行计算和验证,结果表明:自适应小波配点法利用小波阈值滤波删除变化平缓区域大量网格点,而保留变化急剧区域的网格点,比传统方法计算效率高,且分辨率越高,计算效率更高;利用最细层小波系数构建的幂函数形式的激波定位函数能准确判断激波位置和控制X、Y方向人工黏性的大小和分布,从而捕捉不同方向和不同强度的激波。 相似文献
827.
W.M. Moslem S. Rezk U.M. Abdelsalam S.K. El-Labany 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(8):2190-2197
This paper introduces an investigation of shocklike soliton or small amplitude Double Layers (DLs) in a collisionless plasma, consisting of positive and negative ions, nonthermal electrons, as well as solar wind streaming protons and electrons. Gardner equation is derived and its shocklike soliton solution is obtained. The model is employed to recognize a possible nonlinear wave at Venus ionosphere. The results indicate that the number densities and velocities of the streaming particles play crucial role to determine the polarity and characteristic features (amplitude and width) of the shocklike soliton waves. An electron streaming speed modifies a negative shocklike wave profile, while an ion streaming speed modulates a positive shocklike wave characteristic. 相似文献
828.
The natural damped frequencies and the response to translational excitation of a viscous liquid in a circular cylindrical container are obtained. The response of the liquid surface elevation above its equilibrium position, as well as the viscous liquid force in x-direction due to translational excitation in this direction have been numerically evaluated. In this analysis the side wall adhesive boundary conditions have been satisfied, while only the normal bottom condition has been observed. This makes the results of the analysis applicable to liquid height ratio h/a>1. 相似文献
829.
830.
为了解决某型姿控发动机减压阀压力振荡导致阀芯密封面损坏,进而影响调压功能的问题,对其启动过程出口压力振荡和抑制方法进行了研究.基于AMESim仿真平台建立了减压阀仿真模型,分析了阀芯行程和限流孔对减压阀启动特性的影响,结果表明:减小阀芯行程和增加限流圈均有利于抑制减压阀启动过程出口压力振荡.基于此优化了阀芯行程,并在入... 相似文献