Hello, A yearly allocation for the LCRC cluster has been requested with the following updated information: Submitter/PI: Sibendu Som Project Name: cavitation-modeling Division: ES Project title: Development of cavitation models for compression ignition engines Associated funding: DOE - Office of Vehicle Technologies Other Systems: Convergent Science, General Motors Research and Development Science: Injection process plays a significant role in the optimization of internal combustion engines. Performance of direct injection engines is strongly affected by fuel spray quality. Atomization process and spray development largely depends on nozzle design. Inside the injector, fuel can be subjected to cavitation which acts as a mean for promoting liquid break-up thus enhancing primary atomization. Three dimensional un-steady fluid dynamics simulations of the injector internal fluid domain can capture much of the physics involved in the phenomenon. The nature of the inner nozzle flow at the orifice exit directly impacts the fuel atomization and spray. Therefore a link with the primary atomization model is necessary and straightforward. Droplet size, velocity and many other relevant quantities can be inferred from the inner nozzle flow. Different classes of models can be conceived in this area of primary breakup modeling (in order of complexity: PDF assumption, atomizat ion without spatial resolution, with spatial resolution, ELSA models, LES, DNS) with different levels of complexities. Project description: This research activity will mainly focus on comparing the cavitation models existing in the state-of-the-art engine modeling codes CONVERGE, OpenFOAM, and AVL-FIRE. Most cavitation models assume that vapor formation is initiated by the presence of cavitation nuclei which grow to become bubbles and then to form the complex structures also observed experimentally. The transport of vapor can be modeled either as discrete vapor bubbles or as a continuum. The Lagrangian tracked approach can handle natively different velocities for bubbles and liquid by solving the Newton law expressing the balance of forces acting on them. Among Eulerian methods, the multi-fluid model (implemented in AVL-FIRE) is conceptually superior to the single-fluid model (implemented in CONVERGE), since the latter is a homogeneous method therefore only one velocity is shared by all phases; while in a multi-fluid model each phase has its own velocity since momentum is solved separately for each fluid. In this case proper source terms accounting for the exchange of momentum between the phases have to be accounted for. In addition to that, a number of other physical processes have to be simulated. The most important one is the mechanism leading to bubble growth/collapse, i.e. the mass exchange model in cavitating conditions. The so-called Rayleigh-Plesset equation forms the basis for this modeling. The complete non-linear form, even if it is numerically stiff to be integrated, can be implemented in a multi-fluid model. Cavitation threshold can be expressed in terms of saturation pressure if the flow is quasi-steady, or adding viscous shear stress effects for high viscous or high velocity flows. By introducing a plenum for the outlet chamber and using a three-fluid model consisting of liquid, vapor and air, the nozzle outlet region can be resolved. This avoids the setting of unphysical boundary conditions at the nozzle exit and it allows reproducing the flow field accurately even in the proximity of the outlet. In case of super-cavitation the vapor plume can extend slightly beyond the outlet ; in case of hydraulic flip air can re-enter the hole region. An advantage of this approach is that the nozzle flow analysis is coupled to the in-cylinder flow, which results in the possibility of consideration of in-cylinder pressure variations, recirculation in cavitating flows (hydraulic flip), etc. Specific deliverables: - Comparison between single-fluid model (CONVERGE) and multi-fluid (FIRE) models and validation against experimental x-ray radiography data from Argonne. - Perform transient simulations of ECN injectors and perform validation against ECN data - Compare CONVERGE and FIRE results against transient ECN data - Assessment of transient effects: Series of steady simulations at fixed lift vs. transient simulations. - True needle movement (by x-ray visualization, Argonne) vs. idealized needle movement with n-dodecane as diesel surrogate - Coupling with outlet chamber in steady and time varying pressures (combustion chamber conditions) Project URL: http://www.transportation.anl.gov/engines/multi_dim_model_home.html Current FY Hours Used: undetermined amount New FY Requested allocation: 499000 Q1: 125000 Q2: 125000 Q3: 125000 Q4: 124000 Justification: Thank You, The LCRC Accounts System