Use Use of Euler of Eulerian ian multi multi-ph phas ase e (E2P) (E2P) algo algorith rithm m to to mode model l leak leakag age e of of hydrocarbon hydrocarbon vapors vapors duri during ng vehi vehicl cle e refueling re fueling Star Global Forum 2009 December 8 Syed Ali & Marek Lockhart Ford Motor Company 1 Ford Motor Co. CONFIDENTIAL
Agenda • Background Refueling systems Fill Nozzle Capless filler pipe • Star E2P model and BCs • Results • Conclusion • Q & A 2 Ford Motor Co. CONFIDENTIAL
Standard & ORVR Systems Evaporative system with Recirculation line (RL) Carbon canister Fill pipe To engine Fuel tank 3 Ford Motor Co. CONFIDENTIAL
Fuel Storage and Delivery System Fuel System Fill pipe Storage Tank Carbon Canister System 4 Ford Motor Co. CONFIDENTIAL
Nozzle Geometry & Air flow Contents of this slide have been derived from the SAE Paper # 970311 Air flow rate into nozzle shut-off mechanism Fuel, GPM Air, LPM Air/Fuel Ratio 4.0 3.3 0.218 7.0 3.9 0.147 10.0 4.0 0.106 5 Ford Motor Co. CONFIDENTIAL
Fill Pipe Geometry FP entrance Drain hose Recirc Line Fill pipe Flexible Hose 6 Ford Motor Co. CONFIDENTIAL
Problem Definition • Early ORVR SHED test of the first vehicle with capless FP failed at 4 GPM fill rate. • CAE was tasked to investigate! • In general, FP flows are both multi-phase (Liq./Gas) and multi-constituent (Air/HC vapors). • Since the flow in the capless part is gas only, liquid flow in the FP can be omitted. 7 Ford Motor Co. CONFIDENTIAL
About E2P – from Star notes • Both phases coexist everywhere in the flow domain: concept of “Interpenetrating continua”. • Conservation equations for mass, momentum and energy are solved for each phase. • Cover the full range of volume fractions, from 0 to 1. • Mean quantities: velocity, pressure, volume fraction are obtained directly. • Turbulence can be included at little extra cost. 8 Ford Motor Co. CONFIDENTIAL
E2P Model for Fill Pipe • A simplified, gas-only model has been solved using the CFD code StarCD. • Air and hydrocarbon (HC) flows are solved using the Eulerian-2-Phase model. • Estimates of both air and HC flow rates are used as input at various ports. • The discharge of HC vapor from the drain port is used as the metric of performance. 9 Ford Motor Co. CONFIDENTIAL
E2P Model for Fill Pipe • The CFD models have about 1.7 million cells. • Boundary conditions are derived from test data. • Steady state solution is run with double precision. • Need over 15,000 iterations for good convergence. 10 Ford Motor Co. CONFIDENTIAL
BCs for Multiphase Flow Flow of HC/air from fuel tank Air from ambient Flow of HC/air into refueling nozzle Pressure boundary condition 11 Ford Motor Co. CONFIDENTIAL
Results of Design 1 SHED Test CAE Run # 4 GPM 10 GPM 4 GPM 10 GPM 1 0.20966 0.066942 0.31944 0.103775 2 0.39084 The tables present mass of HC/Gallon. Acceptable emission: 0.2 g HC/gallon CAE driven design - D2 Design 1- BC 12 Ford Motor Co. CONFIDENTIAL
ORVR Test & CAE Results CFD Design 1 Design 2 4 GPM 10 GPM 4 GPM 10 GPM 0.31944 0.103775 2.140E-07 3.116E-07 Rig test Design 1 Design 2 Run # 4 GPM 10 GPM 4 GPM 10 GPM 1 0.20966 0.066942 0.04868 0.02440 2 0.39084 0.04870 0.02440 3 0.00830 0.01700 The tables present mass of HC/Gallon. Acceptable emission: 0.2 g HC/gallon 13 Ford Motor Co. CONFIDENTIAL
Results D1, D2 & D1-modified Drain port flow ratios from CFD simulations D1. D2. 4 GPM 10 GPM 4 GPM 10 GPM Q(HC)/Q(Air) -5.7E-07 6.3E-07 Q(HC)/Q(Air) 0.759 0.173 Q(HC)/Total -5.7E-07 6.3E-07 Q(HC)/Total 0.431 0.148 Total Q, lpm 0.818 2.688 Total Q, lpm 1.610 3.816 D1 Modified – RL rotated 30 degrees 4 GPM 10 GPM Q(HC)/Q(Air) -6.667E-06 -1.716E-06 Q(HC)/Total -6.667E-06 -1.716E-06 Total Q, LPM 1.027 2.850 14 Ford Motor Co. CONFIDENTIAL
Results D1 @ 4 GPM Contour plots of concentration of HC (red) in the capless insert Figure 1. HC vapors leaving the drain port – plane near the top. 15 Ford Motor Co. CONFIDENTIAL
Results D1 @ 10 GPM Contour plots of concentration of HC (red) in the capless insert Figure 2. Flow near bottom of drain port. No flow was observed near the top of the drain port. 16 Ford Motor Co. CONFIDENTIAL
Results D2 @ 4 GPM Contour plots of concentration of HC (red) in the capless insert No HC flow observed in the Figure 3. vicinity of the drain port. 17 Ford Motor Co. CONFIDENTIAL
Results D2 @ 10 GPM Contour plots of concentration of HC (red) in the capless insert Figure 4. 18 Ford Motor Co. CONFIDENTIAL
D1-Modified; Results @ 4GPM Contour plots of concentration of HC (red) in Velocity vectors in the capless insert. the capless insert 19 Ford Motor Co. CONFIDENTIAL
Conclusions • The simple gas-based multi-phase model works quite satisfactorily to model flow of hydrocarbon vapors in the filler cup – both standard and capless filler pipes. • The methodology has been instrumental in several programs to guide the design process. Both time and money have been saved. 20 Ford Motor Co. CONFIDENTIAL
Conclusions • The investigation exhibits the important role CAE tools play to better reveal the physics related to failures. • The model will be extended to include the liquid fuel/air flow into the fill pipe. This will allow the model to naturally ingest the ambient air. 21 Ford Motor Co. CONFIDENTIAL
Q & A 22 Ford Motor Co. CONFIDENTIAL
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