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101.
Fei Liu Fei Wei Yu Zheng Yong Jin 《中国颗粒学报》2006,4(3):160-166
A mathematical model has been developed for the simulation of gas-particle flow and fluid catalytic cracking in downer reactors. The model takes into account both cracking reaction and flow behavior through a four-lump reaction kinetics coupled with two-phase turbulent flow. The prediction results show that the relatively large change of gas velocity affects directly the axial distribution of solids velocity and void fraction, which significantly interact with the chemical reaction. Furthermore, model simulations are carried out to determine the effects of such parameters on product yields, as bed diameter, reaction temperature and the ratio of catalyst to oil, which are helpful for optimizing the yields of desired products. The model equations are coded and solved on CFX4.4. 相似文献
102.
B. Peters 《Flow, Turbulence and Combustion》2005,73(3-4):217-229
The objective of this contribution is to investigate whether the mechanism of the thermal diffusion instability in gaseous
flames causing cellular flame structures also occurs during the combustion of porous solid fuel. Based on conservation for
mass and energy, the relevant set of differential equations was derived. Assuming thermal equilibrium between fuel and oxidiser,
a global energy equation was valid for both solid and gaseous phase. The resulting set of differential equations was discretised
by the Collocation method to arrive at a system of algebraic equations. In order to investigate into cellular flame structures,
an infinitesimal disturbance was superimposed onto the plane conversion front. Carrying out a linear instability analysis,
yielded eigenvalues dependent on the wave number of the disturbance. A critical wave number exists below which the real part
of the eigenvalues is positive, thus, indicating a regime of instability. Within this region, eigenvalues with a not-vanishing
imaginary part of the eigen value existed causing cellular flame structures. However, the growth rate of disturbances was
found to be small, which may explain the difficulty to investigate this phenomena experimentally. 相似文献
103.
A. Brandl M. Pfitzner J. D. Mooney B. Durst W. Kern 《Flow, Turbulence and Combustion》2005,75(1-4):335-350
In order to simulate the turbulent combustion process occurring in spark-ignition (IC) engines, it is necessary to provide
suitable and numerically economical models, the latter being particularly important in the application to industrial problems.
Moreover, these models must deliver sufficiently accurate results for the unsteady operation of spark combustion engines,
concerning variable geometries, temperatures, pressures and charge development in different configurations. In this work different
turbulent combustion models for premixed hydrocarbon combustion are compared with respect to their ability to accurately predict
the propagation of turbulent perfectly premixed flames.
As a first configuration a cylinder of constant volume was studied. Transient calculations were used to simulate the propagation
of the turbulent flame and to evaluate the resulting turbulent burning velocity. These calculations were performed for a perfect
mixture of air and hydrocarbons at stoichiometric mixture and different initial conditions concerning pressure, temperature
and turbulence intensity. As a second configuration a stationary turbulent bunsen-type flame with methane fuel was used to
validate the turbulent combustion model of [Lindstedt and Vaos, Combust. Flame 116 (1999) 461] at different pressures. Calculated results were then compared to experimental data of [Kobayashi, Tamura,
Maruta and Niioka. In: Proceedings of the 26th Symposium on Combustion, 1996, p. 389] and show excellent agreement for the turbulent burning velocity at several pressure levels using only a single
set of model parameters. 相似文献
104.
超声速燃烧火焰稳定凹腔质量交换特性的数值研究 总被引:2,自引:0,他引:2
对超声速冷流条件下用于超燃冲压发动机的凹腔火焰稳定器的质量交换特性进行研
究. 采用混合RANS/LES方法对非定常流场进行数值模拟,考虑了凹腔的长深比和后缘角度两
个关键参数. 计算得到了凹腔剪切层拟序结构的演化过程. 对凹腔压力振荡历程进行幅频分
析,所得到的频率和理论分析结果及一些计算结果十分吻合. 结果表明,凹腔的长深比和后
缘倾角对凹腔质量交换过程都有较大的影响. 凹腔驻留时间随着长深比的增加而增加. 随着
后缘倾角减小,长深比较小的凹腔的驻留时间增加,长深比较大的凹腔则完全相反. 该计算
结果为凹腔设计提供了新认识. 相似文献
105.
106.
The development of mathematical models for the design of controlstrategies for spark ignition automotive engines is described. The objectiveof the models, used for both simulation and optimization analysis, is theprediction of the effects of control strategies on fuel consumption andemissions of a vehicle over arbitrary driving cycles. In order to achievethe best compromise between precision, experimental costs, computationaltime and flexibility, a mixed modelling approach is used, withphenomenological and input-output models integrated within a hierarchicalsystem.Mean value models have been used to describe the most significant dynamiceffects: (i) air flow. (ii) two phases fuel flow in the intake manifold, and(iii) thermal flow in the cylinder walls. Stochastic effects due to sensorsand actuators can be also predicted.Two-zone and multizone thermodynamic models for the prediction ofpressure cycle sub-models for engine emissions (HC, CO, andNO
x
and mechanical losses have been developed. Experimentaldesign techniques are also under development to optimize the interactionsbetween experimental analysis and models. Most of the models have beenintegrated in a computer code, used by a major automotive supplier. 相似文献
107.
To allow for a reliable examination of the interaction between velocity fluctuations, acoustics and combustion, a novel numerical procedure is discussed in which a spectral solution of the Navier–Stokes equations is directly associated to a high-order finite difference fully compressible DNS solver (sixth order PADE). Using this combination of high-order solvers with accurate boundary conditions, simulations have been performed where a turbulent premixed V-shape flame develops in grid turbulence. In the light of the DNS results, a sub-model for premixed turbulent combustion is analyzed. To cite this article: R. Hauguel et al., C. R. Mecanique 333 (2005). 相似文献
108.
109.
This study reports on experimental investigations on isothermal and reacting swirled non-premixed flows under varying pressure
conditions. In this configuration, a central high speed fuel jet was surrounded by a heated swirling air flow. For the reacting
case natural gas served as fuel whereas for isothermal conditions fuel was replaced by a mixture of helium and air to achieve
Reynolds-similarity. The optically accessible combustor allowed for application of laser diagnostics. Here we report on Laser
Doppler Anemometry and planar laser-induced fluorescence (PLIF) experiments used to characterize the flow field and visualize
selected scalars, respectively. Acetone served as a fluorescence marker for mixture fraction investigations. The hydroxyl
radical was used to provide general features of the reaction zone such as flame shape and mean stabilization. To expose the
influence of pressure on the flame structure three different operating points were investigated varying the combustor pressure
between 2 and 6 bar while the inflow bulk velocities remained the same. Striking features of the present configuration are
a detached flame, multiple recirculation zones, and complex coherent flow structures. 相似文献
110.
重度原油注空气低温氧化过程研究(英文) 总被引:1,自引:0,他引:1
低温氧化反应对现场燃烧(ISC)技术点火的成功有十分重要的影响.采用高压氧化管,研究了不同温度压力下,新疆克拉玛依重度原油的低温氧化过程.结果表明,温度和压力的变化对低温氧化反应的放热程度、持续时间以及气体产物有明显影响.适合油样低温氧化反应的温度和压力分别为150℃和10MPa.此外,采用纯组分替代原油族组分进行低温氧化实验,研究低温氧化反应对原油族组分(饱和烃、芳香烃、胶质、沥青质)含量的影响.结果表明,原油所含族组分中,芳香烃组分最易被氧化,其含量由氧化前的19.17%减少到12.38%(150℃)和9.51%(250℃).随着低温氧化过程的进行,结构复杂的族组分(胶质、沥青质)的含量明显增加.实验数据对油藏实施注空气技术,以及该技术现场实施条件的确定有十分重要的指导意义. 相似文献