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环膜液体射流的破碎机理研究对于GDI汽油机的雾化过程具有重要的意义。利用线性不稳定性理论研究了旋转气体运动对低阶和高阶模式黏性环膜液体射流破碎的影响。对于色散方程的数值计算结果表明,无论是对称模式还是非对称模式,低阶模式的扰动增长率通常较之高阶模式要大得多,但较之低阶模式扰动,高阶模式对气体旋转运动更为敏感。研究结果同时表明,对于非对称模式,无论是低阶模式还是高阶模式的扰动,气体旋转运动都是液体破碎的失稳因素;对于对称模式,气体旋转运动是低阶模式扰动的促稳因素,然而却是高阶模式扰动的强烈的失稳因素。 相似文献
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利用线性热不稳定性理论,对黏性液体射入高温气体介质模型所对应的色散方程进行了数值求解。利用所得到的计算结果,研究了加热条件下轴对称模式扰动液体射流破碎机理,探讨了表征各种影响射流破碎作用力的无量纲Weber数(We)、密度比(Q)、Marangoni数(Ma)和Ohnesorge数(Z)对液体射流破碎最大扰动增长率及占优波数的影响。研究结果表明,液体和气体介质之间的温度梯度对液体射流稳定性有着非常显著的影响,表明热毛细力对于液体射流的破碎有促进作用,这种作用对处于Taylor模式下的液体射流尤为显著,并且这种热力作用可使液体射流从一种模式进入另一种模式,并可以大大改变射流的破碎尺序。 相似文献
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利用线性热不稳定性理论,对黏性液体射入高温气体介质所对应的色散方程进行了数值求解.利用所得到的计算结果,研究了加热条件下射流速度、气液密度比、液体黏度、温度梯度及液体种类等实际射流参数对射流最大扰动增长率及占优波数的影响规律.研究结果表明:对于加热条件下Reyleigh模式的液体射流,气液密度比、温度梯度是射流破碎的失稳因素,而射流速度、液体黏度则是液体射流破碎的促稳因素;对于Taylor模式的液体射流,射流速度、温度梯度、气液密度比是射流破碎的失稳因素,而液体黏度是液体射流破碎的促稳因素.研究结果同时证明了液体种类的改变对射流不稳定性的影响是多种因素共同作用的结果. 相似文献
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基于非线性稳定性理论,在同时考虑射流周围气体同轴旋转、射流和周围气体可压缩性以及射流液体中含空化气泡的条件下,建立了描述同轴旋转可压缩气体中含空泡液体射流稳定性的色散方程,并验证了色散方程及其求解方法的正确性.在此基础上,进行了同轴旋转可压缩气体中含空泡液体射流形态的研究.结果表明:周围气体的同轴旋转改变了射流表面的占优扰动模式,即扰动模式由轴对称扰动占优转变为非轴对称扰动占优;随着气体同轴旋转强度的增加,射流周向形态的变化越来越明显,射流表面会逐渐形成越来越多凹凸不平的波纹.射流及其周围气体的可压缩性对射流周向形态的影响不明显,但会对射流的轴向形态产生一定作用.总体上看,空泡的存在对射流形态的影响弱于气体同轴旋转的影响.通过研究进一步完善了液体射流稳定性数学模型,加深了对液体射流分裂与雾化机理的理解. 相似文献
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基于线性稳定性理论,针对具有线性温度分布的液体射流分裂过程,建立了射流扰动控制方程,给出了扰动方程在气/液分界面上应满足的边界条件,推导出了描述存在温度扰动的圆柱形液体射流自由表面三维扰动发展的色散关系;模型中同时考虑了空化气泡、射流周围气体的旋转以及射流和周围气体的可压缩性;对建立的数学模型及相应的求解方法进行了验证.在此基础上,分析了非轴对称扰动下具有线性温度分布的射流表面扰动波数和扰动增长率的演化,讨论了存在温度扰动时,空化气泡、气体旋转以及射流和气体可压缩性对射流稳定性作用的变化.结果表明:温度扰动的存在不仅会对液体射流稳定性产生较大影响,使得最大扰动增长率明显增大,扰动波波数范围显著拓宽,而且还会对空化气泡、气体旋转以及射流和气体可压缩性对射流稳定性的作用产生一定的影响. 相似文献
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本文分析粘性液体射流的线性稳定性问题,本文首次根据理论预测所确定的物理条件观察到了射流在各种非轴对称模式支配下的破碎情况,实验采用的是高速公路分幅激光全息技术,实验结果表明,液体射流结构遵守稳定性理论所预测的规律,实验还发现,液体射流的实际破碎尺寸要大于线性稳定必伯预测结果。 相似文献
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射流参数对旋流雾化的影响 总被引:3,自引:0,他引:3
本文利用线性不稳定性理论,分析了无粘旋转液体射流射入无界气体介质中的破碎机理。通过改变各项射流参数,着重分析了液体旋流数对射流分裂雾化的影响,同时也探讨了与各种射流条件相对应的射流分裂雾化的主导模式。其研究结果可为旋流在工程实际中的应用,特别是在直喷式汽油机中的应用提供了一定的理论依据。 相似文献
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通过自行搭建的环膜射流试验系统,采用高速摄影技术对牛顿流体(水)与剪切变稀型幂律流体(卡波姆凝胶)环膜射流的破碎模式及破碎特征进行了试验.结果表明:牛顿流体与幂律流体都存在相同的3种射流破碎模式,且两种流体在射流破碎机理上没有本质性的差异.在3种射流破碎模式中,圣诞树状破碎模式下的射流破碎效果最佳,泡状破碎模式次之,波辅助破碎模式下的射流破碎效果最差.且射流破碎效果随卡波姆凝胶黏度的增加而显著恶化;射流的表面波波长随液体速度的增加而增加,随气体速度的增加而减小.与水相比,卡波姆凝胶射流的表面波波长受液体速度的影响更加明显.在高气/液速度比条件下,气/液剪切作用力是影响射流破碎的主导因素.基于环膜射流的理论分析结果和经验公式,提出了量纲为1波长与射流气/液速度、流体流变特性相关联的公式,式中量纲为1波长随参数T的增加逐渐增加. 相似文献
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A spatial linear instability analysis is conducted on an annular viscous liquid jet injected into compressible gases and a three-dimensional model of the jet is developed. The model takes into account differences between the velocities, densities of the gases inside and outside of the liquid jet. Theoretical analysis reveals that there exist 9 dimensionless parameters controlling the instability of the liquid jet. Numerical computations reveal some basic characteristics in the breakup and atomization process of the liquid jet as well as influences of these relevant parameters. Major observations and findings of this study are as follows. The Mach number plays a destabilizing role and the inner Mach number has a greater effect on the jet instability than the outer Mach number. The Reynolds number always tends to promote the instabilities of the liquid jet, but its influence is very limited. The Weber number and the gas-to-liquid density ratio also have unstable effects and can improve the atomization of liquid jets. Furthermore, the effects of the Weber number and gas-to-liquid density ratio on the maximum growth rates of axisymmetric and non-axisymmetric disturbances and corresponding dominant wave numbers are manifested in a linear way, while that of the Mach number is non-linear. The effect of Reynolds on the maximum growth rates is non-linear, but the dominant wavenumber is almost not affected by the Reynolds number. 相似文献
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A spatial linear instability analysis is conducted on an annular viscous liquid jet injected into compressible gases and a
three-dimensional model of the jet is developed. The model takes into account differences between the velocities, densities
of the gases inside and outside of the liquid jet. Theoretical analysis reveals that there exist 9 dimensionless parameters
controlling the instability of the liquid jet. Numerical computations reveal some basic characteristics in the breakup and
atomization process of the liquid jet as well as influences of these relevant parameters. Major observations and findings
of this study are as follows. The Mach number plays a destabilizing role and the inner Mach number has a greater effect on
the jet instability than the outer Mach number. The Reynolds number always tends to promote the instabilities of the liquid
jet, but its influence is very limited. The Weber number and the gas-to-liquid density ratio also have unstable effects and
can improve the atomization of liquid jets. Furthermore, the effects of the Weber number and gas-to-liquid density ratio on
the maximum growth rates of axisymmetric and non-axisymmetric disturbances and corresponding dominant wave numbers are manifested
in a linear way, while that of the Mach number is non-linear. The effect of Reynolds on the maximum growth rates is non-linear,
but the dominant wavenumber is almost not affected by the Reynolds number. 相似文献
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液体燃料射流最不稳定频率的理论分析(1)——液体燃料射流的最不?… 总被引:3,自引:0,他引:3
利用线性不稳定性理论,对粘性液体燃料射流射入气体介质的射流模型所对应的色散方程进行了数值求解。利用计算结果,分析了液体燃料射流不稳定性研究中的3个最重要的无量纲参数参韦韦伯数We、雷诺数Re及密度比Q,对分别处于瑞利模式和泰勒模式下的液体射流的最不稳定频率及对应的最大扰动增长率的影响。 相似文献
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《Numerical Heat Transfer, Part A: Applications》2013,63(6):591-609
The article presents a numerical simulation of swirling turbulent flows and heat transfer in an annular duct. The time-averaged governing equations are solved, which are closed by a new algebraic Reynolds stress model (ASM). The simulation is performed under different flow conditions. The calculated results of gas axial and tangential velocities, turbulent kinetic energy, temperature, and local heat transfer coefficients on the inner and outer walls of the annulus are provided. They illustrate the effect of swirl number, inlet axial velocity, and ratio of inner to outer radius on the mean flow and turbulence properties, as well as on enhancing heat transfer in the annular duct. 相似文献