BMW Diesel. March th, 2008, London manifold in a high performance diesel engine

Transcription

1 Diesel BMW 22 th March Thermal 2011 Star European simulation User Conference of an exhaust Slide 1 of 20 March th, 2008, London manifold in a high performance diesel engine Star European User Conference 1, G. Hofer 2, Dr. M. Prosi 1, Dr. Ch. Samhaber 1, G. Pessl 1 1 BMW Motoren GmbH, Austria 2 University of applied science, FH-Wels, Austria Noordwijk March 2011 Sheer Freude Driving am Pleasure Fahren

2 Slide 2 of 27 BMW Overview BMW s Diesel Engine R & D Center in Steyr/Austria Motivation Simulation Target Modelling Approach Simulation Geometry Discussion of Results Summary

3 Slide 3 of 27 BMW BMW Motoren GmbH Steyr / Austria Employees ~ 2700 Complete Diesel engine R & D for the BMW Group (~ 500 engineers) Production of 6-cylinder petrol and 4- and 6-cylinder Diesel engines Volume of output (engines) ~ pcs. per year

4 Slide 4 of 27 BMW Motivation Simulation Target Actual state: During design process cracks in exhaust manifold Finite element simulation not satisfying Possible reason: no adequate HTC-boundary condition at exhaust manifold s cold side Simulation Target: Improve boundary condition for FE simulation at manifold s cold side

5 Slide 5 of 27 BMW Modelling approach Existing entire car aerodynamics (StarCD 3.26) Focusing on vicinity of exhaust manifold (StarCCM+) Including solid elements Including radiation Extracting HTC for FE simulation and mapping Compare FE results

6 Slide 6 of 27 BMW Geometry and boundary conditions Existing entire car aerodynamics (StarCD 3.26) Vehicle: BMW X5 Series, 36 mio. cells High performance diesel engine 6 cylinders inline Double stage turbo charging 265 hp, 650 Nm Velocity distribution high low

7 BMW 23th March 2011 Slide 7 of 27 BMW Geometry preparation Focusing on vicinity of exhaust manifold Definition of simulation area

8 Slide 8 of 27 BMW Meshing cold side Exhaust manifold ~ 3 mio. cells, Poly mesh, 2 prism layers Volume cut cold side fluid mesh

9 BMW 23th March 2011 Slide 9 of 27 BMW Meshing solids and hot side Heat protection shield s Solid: exhaust manifold Solid: heat protection shield Fluid: cold side

10 Slide 10 of 27 BMW Extracting boundaries Results in StarCD 3.26 Extract under hood flow in StarCD 4.08: ccmg Create table of flow distribution Star CCM+: Mapping results to faces Export table for boundary condition of detail simulation Star CCM+: Import ccmg and table Import surfaces of detail simulation

11 Slide 11 of 27 BMW Definition of boundaries Gray: Wall Red: Velocity inlet Orange: Pressure outlet

12 Slide 12 of 27 BMW Definition of boundaries: hot side GT-Power StarCD coupling Base engine StarCD v3.26 Crank angle [ ]

13 Slide 13 of 27 BMW Cycle averaged values for hot side Wall temperature [ C] high Heat transfer coefficient [W/m²K] low

14 Slide 14 of 27 BMW Operation points Maximum torque (Uphill run) 35 km/h Trailer with 2500kg load 35% uphill gradient Normal highway run: 120 km/h Maximum velocity (v max ): 220 km/h

15 Slide 15 of 27 BMW Model set up Star CCM CHT Turbulence model: k all y + Radiation: Surface to surface Gray thermal radiation patches HTC results of GT-Power coupling for hot side

16 Slide 16 of 27 BMW Streamlines, Uphill run low high

17 Slide 17 of 27 BMW Velocity distribution, Uphill run high Cut A-A low Near wall velocity [m/s]

18 Slide 18 of 27 BMW Streamlines, v max low high

19 Slide 19 of 27 BMW Velocity distribution, v max high Cut A-A low Near wall velocity [m/s]

20 Slide 20 of 27 BMW Temperature distribution, v max Differences to Measurement [K] +4 K -2 K -18 K +6 K +23 K -8 K +11 K low Temperature (C) high

21 Slide 21 of 27 BMW Temperature distribution Actual state FE Simulation low Temperature (C) high Uphill run 120 km/h v max 220 km/h

22 Slide 22 of 27 BMW Heat transfer coefficient Actual state FE Simulation low Heat transfer Coefficient (W/m²K) (Reference temperature 280 C) high Uphill run 120 km/h v max 220 km/h

23 Slide 23 of 27 BMW Averaged heat transfer coefficient

24 Slide 24 of 27 BMW FE-Simulation(TMF): Number of endurance cycles (N F ) Actual state FE Simulation HTC constant Improved BC Detailed HTC distribution high low

25 Slide 25 of 27 BMW FE-Simulation(TMF): Number of endurance cycles (N F ) Actual state FE Simulation HTC constant Improved BC Detailed HTC distribution high low

26 Slide 26 of 27 BMW Summary Extensive work input is necessary Acceptable effort only, if underhood flow is existing Useful improvement of FE-Simulation More exact prediction of cracks in the manifold Possibility of mapping results to similar projects

27 Slide 27 of 27 BMW Ready for the future Thank you very much for your Attention!