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1.
Kambale Mondo Senda Agrebi Fathi Hamdi Fatma Lakhal Amsini Sadiki Mouldi Chrigui 《Entropy (Basel, Switzerland)》2022,24(5)
Even though there is a pressing interest in clean energy sources, compression ignition (CI) engines, also called diesel engines, will remain of great importance for transportation sectors as well as for power generation in stationary applications in the foreseeable future. In order to promote applications dealing with complex diesel alternative fuels by facilitating their integration in numerical simulation, this paper targets three objectives. First, generate novel diesel fuel surrogates with more than one component. Here, five surrogates are generated using an advanced chemistry solver and are compared against three mechanisms from the literature. Second, validate the suggested reaction mechanisms (RMs) with experimental data. For this purpose, an engine configuration, which features a reacting spray flow evolving in a direct-injection (DI), single-cylinder, and four-stroke motor, is used. The RNG k-Epsilon coupled to power-law combustion models is applied to describe the complex in-cylinder turbulent reacting flow, while the hybrid Eulerian-Lagrangian Kelvin Helmholtz-Rayleigh Taylor (KH-RT) spray model is employed to capture the spray breakup. Third, highlight the impact of these surrogate fuels on the combustion properties along with the exergy of the engine. The results include distribution of temperature, pressure, heat release rate (HRR), vapor penetration length, and exergy efficiency. The effect of the surrogates on pollutant formation (, , ) is also highlighted. The fifth surrogate showed 47% exergy efficiency. The fourth surrogate agreed well with the maximum experimental pressure, which equaled 85 Mpa. The first, second, and third surrogates registered 400, 316, and 276 g/kg fuel, respectively, of the total CO mass fraction at the outlet. These quantities were relatively higher compared to the fourth and fifth RMs. 相似文献
2.
This investigation concerns numerical calculation of turbulent forced convective heat transfer and fluid flow in straight ducts using the RNG (Re-Normalized Group) turbulence method. A computational method has been developed to predict the turbulent Reynolds stresses and turbulent heat fluxes in ducts with different turbulence models. The turbulent Reynolds stresses and other turbulent flow quantities are predicted with the RNG κ?ε model and the RNG non-linear κ-ε model of Speziale. The turbulent heat fluxes are modeled by the simple eddy diffusivity (SED) concept, GGDH and WET methods. Two wall functions are used, one for the velocity field and one for the temperature field. All the models arc implemented for an arbitrary three dimensional duct. Fully developed condition is achieved by imposing cyclic boundary conditions in the main flow direction. The numerical approach is based on the finite volume technique with a non-staggered grid arrangement. The pressure-velocity coupling is handled by using the SIMPLEC-algorithm. The convective terms are treated by the QUICK, scheme while the diffusive terms are handled by the central-difference scheme. The hybrid scheme is used for solving the κ and ε equations. The overall comparison between the models is presented in terms of friction factor and Nusselt number. The secondary flow generation is also of major concern. 相似文献
3.
Swirling flow is a common phenomenon in engineering applications. A numerical study of the swirling flow inside a straight pipe was carried out in the present work with the aid of the commercial CFD code fluent. Two-dimensional simulations were performed, and two turbulence models were used, namely, the RNG k–ε model and the Reynolds stress model. Results at various swirl numbers were obtained and compared with available experimental data to determine if the numerical method is valid when modeling swirling flows. It has been shown that the RNG k–ε model is in better agreement with experimental velocity profiles for low swirl, while the Reynolds stress model becomes more appropriate as the swirl is increased. However, both turbulence models predict an unrealistic decay of the turbulence quantities for the flows considered here, indicating the inadequacy of such models in simulating developing pipe flows with swirl. 相似文献
4.
Analysis of Two-Phase Cavitating Flow with Two-Fluid Model Using Integrated Boltzmann Equations 下载免费PDF全文
Shuhong Liu Yulin Wu Yu Xu & Hua-Shu Dou 《advances in applied mathematics and mechanics.》2013,5(5):607-638
In the present work, both computational and experimental methods are employed
to study the two-phase flow occurring in a model pump sump. The two-fluid
model of the two-phase flow has been applied to the simulation of the three-dimensional
cavitating flow. The governing equations of the two-phase cavitating flow
are derived from the kinetic theory based on the Boltzmann equation. The isotropic
RNG$k-\epsilon-k_{ca}$ turbulence model of two-phase flows in the form of cavity number instead
of the form of cavity phase volume fraction is developed. The RNG $k-\epsilon-k_{ca}$ turbulence
model, that is the RNG$k-\epsilon$ turbulence model for the liquid phase combined
with the $k_{ca}$model for the cavity phase, is employed to close the governing turbulent
equations of the two-phase flow. The computation of the cavitating flow through a
model pump sump has been carried out with this model in three-dimensional spaces.
The calculated results have been compared with the data of the PIV experiment. Good
qualitative agreement has been achieved which exhibits the reliability of the numerical
simulation model. 相似文献
5.
A. Abdel‐Fattah 《国际流体数值方法杂志》2007,53(11):1673-1688
The calculations of quasi‐three‐dimensional momentum equations were carried out to study the influence of wall rotation on the characteristics of an impinging jet. The pressure coefficient, the mean velocity distributions and the components of Reynolds stress are calculated. The flow is assumed to be steady, incompressible and turbulent. The finite volume scheme is used to solve the continuity equation, momentum equations and k–ε model equations. The flow characteristics were studied by varying rotation speed ω for 0?ω?167.6 rad/s, the distance from nozzle to disk (H/d) was (3, 5, 8 and 10) and the Reynolds number Re base on VJ and d was 1.45 × 104. The results showed that, the radial velocity and turbulence intensity increase by increasing the rotation speed and decrease in the impingement zone as nozzle to disk spacing increases. When the centrifugal force increases, the radial normal stresses and shear stresses increase. The location of maximum radial velocity decreases as the local velocity ratio (α) increases. The pressure coefficient depends on the centrifugal force and it decreases as the distance from nozzle to plate increases. In impingement zone and radial wall jet, the spread of flow increases as the angular velocity decreases The numerical results give good agreement with the experiment data of Minagawa and Obi (Int. J. of Heat and Fluid Flow 2004; 25 :759–766). Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
6.
Akin Ozdemir Ihsan Pehlivan Akif Akgul Emre Guleryuz 《Chinese Journal of Physics (Taipei)》2018,56(6):2852-2864
A strange novel three-dimensional quadratic continuous autonomous chaotic system with fully golden proportion equilibria is proposed. It has only seven terms, three quadratic nonlinearities and one parameter ‘a’. The system equations have four equilibrium points and very interestingly all the equilibrium points have fully golden proportion values. Besides, this chaotic system has hidden amplitude control properties. The dynamic analyses of the system are presented such as equilibrium points, dissipativity, Lyapunov exponents, bifurcation diagrams, phase portraits and hidden amplitude control properties. Later, electronic circuit of the system is simulated in software and implemented in real environment. Finally, microcomputer-based random number generator (RNG) application and its NIST-800-22 tests are executed as another real-time application. 相似文献
7.
大型海上风力机尾迹区域风场分析 总被引:6,自引:4,他引:2
随着世界范围内海上风电场的不断兴起及海上风电场设计规模的日趋庞大,大型海上风力机尾迹区域风场特征的研究对于海上风电场的优化布局有着重要的指导意义。本文基于三维Navier-Stocks控制方程和适用于旋转流场分析的RNGk-ε湍流模型,采用滑移网格技术对美国可再生能源实验室(NREL)的5 MW海上风力机的性能及其尾迹区域的风场特征进行了较为系统的数值模拟。通过将不同风速下风力机输出功率的数值结果与NREL的设计参考数据进行对比,三维数值模型的有效性得到了很好地验证。此外,在此基础上进一步研究了大型海上风力机额定风速下及不同风轮转速下尾迹区域平均风速的分布特征,并得到了一系列具有参考价值的重要结论。 相似文献
8.
In the first part of the present study, an appropriate inflow turbulent boundary condition is chosen. Then, a comparison is
made between two turbulence models for a plasma jet discharged into air atmosphere. The plasma jet gas phase flow is predicted
with the standard k–ɛ model and the RNG model of turbulence. Particles behavior is modeled using stochastic particles trajectories.
A validation of the plasma jet model is made by comparison with experimental data. This part of the study shows that the flow
features are better predicted with the RNG model. The choice of appropriate boundary conditions seems to be crucial for a
better simulation of plasma thermal spraying. Afterwards, computations are performed for projection of Ni particles. It is
found that the computed particles velocities and temperatures are also better predicted with the RNG model compared with the
k–ɛ model. The second part of this study is concerned with the effect of the substrate movement on the gas flow field. This
is performed in order to simulate a realistic coatings process where a relative movement between the torch and the substrate
always exists. Three substrate velocities have been used and it is found that the flow fields are affected only very near
the substrate wall. 相似文献
9.
Simon Schneiderbauer Stefan Pirker 《International Journal of Computational Fluid Dynamics》2013,27(1-2):51-68
The open boundary conditions for the CFD simulation of the micro- and meso-scale flow and temperature distribution around the Grimming mountain, Austria, are determined by an optimisation approach from interior observations. The numerical weather prediction model ALADIN–Austria provides wind speed and wind direction at those spatially arbitrarily defined observations. Furthermore, the plausibility of the resulting flow over the Grimming mountain is checked (a) by data of a ground station at the top of the Grimming mountain showing suitable correlation with the measurements. Besides, (b) the vertical turbulence profiles at the ground station are qualitatively compared to extensive studies covering the Askervein hill. In addition, (c) the wavelength of internal gravity waves obtained from the numerical CFD model is examined by analytic approximations at the Grimming mountain and by linear mountain wave theory at a mathematically idealised hill. Finally, the grid independence of the presented CFD model is shown. 相似文献
10.