Abstract
To calculate the governing equations for the turbulent two-phase flow an Extended TAB-model (TP) model is presented to fit for the gas phase and the liquid phase. In the gas phase, Favre-averaging is used for continuity equation, momentum equation. As a result of the averaging, unclosed terms appear which require modeling. In order to close the turbulent Reynolds stress tensor in the momentum equation, the so-called Boussinesque-approximation, which is based on an analogy between molecular diffusion and diffusion turbulent eddies, has been employed. Turbulent kinetic energy k equation and turbulent dissipation ε equation are added to close the Navier-Stokes equations. The temporal differencing scheme in CFD(computational fluid dynamics) code (KIVA-3V) is largely implicit. In the Lagragian phase, implicit differencing is used for all diffusion terms and terms associated with pressure wave propagation. A method similar to the Semi-Implicit Method for Pressure Linked Equations (SIMPLE)-algorithm is used to solve the couple implicit set of equations. In the liquid phase, probability density function (PDF) method is used for solving droplet spray equation. Taylor Analogy Breakup (TAB) model used in the standard KIVA-code is extended with a deformation velocity such that their lifetime is extended to match experimentally observed jet breakup lengths. Furthermore, other models such as Rayleigh-Taylor (R-T) model, Discrete Droplet Models (DDM) etc are discussed. Finally, cylinder pressure and corresponding heat release rates in a directed-injection diesel engine are calculated and compared with the experiments. It gives the theory and method about calculating turbulence exactly in directed-injection diesel engine.DOI: http://dx.doi.org/10.5755/j01.mech.18.1.1283
Highlights
The Taylor Analogy Breakup (TAB)-model was found to be appropriate for injection pressure up to around 400 bar, which was observed by Tanner et al In the paper, the governing equations for the turbulent reacting two-phase flow solved in the KIVA-3V fluid dynamics code are presented
For each of the simulations cylinder pressure and heat release rate are compared with measured values
The heat release rates are similar between TP model (45 J/°CA) and experiment (42 J/°CA), but in the original KIVA model it is 55 J/°CA
Summary
In the last years a considerable improvement of High Speed Direct Injection (HSDI) Diesel Engine technology has occurred, with a strong increase of fuel economy and a remarkable reduction of emissions and combustion noise [1]. Since the flow is turbulent in most engineering applications, the urgent need to resolve engineering problems has led to preliminary solutions based on the Navier-Stokes equations up to a certain point, but they introduce closure hypothesis that rely on dimensional arguments and require empirical input [2] This semiempirical nature of turbulence models puts them into the category of an art rather than a science. In order to close the turbulent Reynolds stress tensor in the momentum equations, the so-called Boussinesque-approximation, which is based on an analogy between molecular diffusion and diffusion turbulent eddies, has been employed. On the other hand, are clearly anisotropic, which poses a significant constraint for the applied turbulence model
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
