DNMN Product Development 40-Ton Articulated Truck Cooling System Modelling Using STAR-CCM+ Gary Yu, Martin Timmins and Mario Ciaffarafa DENSO Marston Ltd, Bradford, BD17 7JR, UK DENSO MARSTON LTD.
DNMN Product Development DENSO Marston Founded in 1904 Acquired by DENSO in 1989 Located in Shipley, West Yorkshire Designs and Manufactures engine cooling modules for Heavy Duty Cooling applications Product Range includes radiators, oil coolers, inter-coolers and condensers DENSO MARSTON LTD.
DNMN Product Development Project Background • Research project partly funded by the UK government - Validation of Complex Systems (VOCS); • DNMN was part of a consortium of UK based companies participating in the project which was led by a major off highway original equipment manufacturer (OEM); • The project covered many aspects of vehicle simulation, with DNMN focussing on cooling system simulation and validation. Acknowledgement : This work was co-funded by the Technology Strategy Board (TSB) and One North East, UK under the Validation of Complex Systems (VOCS) grant programme. The Technology Strategy Board is an executive body established by the United Kingdom Government to drive innovation. It promotes and invests in research, development and the exploitation of science, technology and new ideas for the benefit of business - increasing sustainable economic growth in the UK and improving quality of life. DENSO MARSTON LTD.
DNMN Product Development Outline 1. 1D KULI simulation of cooling system – coupled with STAR-CCM+ single stream heat exchanger model ; 2. 3D CFD simulation of cooling system – STAR-CCM+ dual stream heat exchanger model; 3. Comparison of 1D KULI and 3D CFD results. Tier 3 Off Highway Truck Radiator module including radiator, Charge air cooler (CAC) condenser, oil cooler and cooling fan and cooling fan DENSO MARSTON LTD.
DNMN Product Development Computational Domain and Boundary Conditions Vehicle speed (m/s) 0 Wind tunnel size 22 X 13 X12 L X W X H (m^3) Top and Sides Pressure outlet Ground Wall Ambient temperature ( o C) 20 Radiator fan rpm 1500 Charge Air Cooler fan rpm 2100 • Vehicle overall size: 10.889 m (L) x 3.43 m (W) x 3.745 m (H); • Vehicle modelled at stationary and idle condition. DENSO MARSTON LTD.
DNMN Product Development Truck Model Meshing Import CAD volume mesh refinement Surface Wrap Surface Remesh Volume Mesh Mesh size : 8mm (in dense area) Number of cells : ~21.6 million DENSO MARSTON LTD.
DNMN Product Development Numerical Model 3D, steady state flow, κ - ε model for turbulence; 1. 2. Cooling air, charged air modelled as ideal gas, whilst radiator coolant, oil cooler oil as constant density; 3. Segregated flow temperature; 4. Heat exchangers modelled as porous media for fluid flow, dual stream model for heat rejection calculation; 5. Moving reference frame (MRF) fan model, momentum source model used but with convergence problem. DENSO MARSTON LTD.
DNMN Product Development Coupling of KULI with CFD KULI is a 1D tool used for vehicle cooling system simulation Images courtesy of Magna Powertrain Velocity distribution 1. Air flow distribution is uniform in traditional 1D KULI model across heat exchanger face; 2. 3D distribution based on velocity profile from CFD simulation. DENSO MARSTON LTD.
DNMN Product Development Coupling of KULI with CFD Typical procedure: CFD velocity field (isothermal) 1. Initial CFD isothermal simulation results; 2. KULI generation of resistance KULI resistance matrix matrix; 3. KULI modelling for heat rejection rate, Q; 4. Update of CFD model with Q values KULI Model STOP for all heat exchangers; Q 5. Calculation of thermal velocity field by CFD; CFD single stream heat exchanger model 6. Feedback to KULI for next iteration until converged. • It is very expensive for CFD volume cells > 20 M; CFD velocity field (thermal) • Dual stream heat exchanger model in STAR-CCM+ can avoid this. DENSO MARSTON LTD.
DNMN Product Development Dual Stream Heat Exchanger CFD Model Test Data Required: Cold stream side: Q Table for heat rejection rate and mass flow rate; Hot stream side: Mass flow rate in the test should be the same as the condition modelled in CFD. Thermal output (kW) hot stream mass flow rate @ actual working condition CAC cold stream flow rate (kg/min) Use KULI to obtain actual working condition Heat exchanger 3D heat transfer map from KULI DENSO MARSTON LTD.
DNMN Product Development Determination of Porous Media Pressure Drop Coefficients • Pressure drop over heat exchanger core is calculated by DP/DL= α v 2 + β v , α and β are determined based on test data, v is the inlet flow velocity; • CFD under predicts the pressure drop at a fixed mass flow rate because it does not use the correct throughway area, so needs to be corrected using these equations. Radiator, Oil cooler α cfd = (A cfd /A test ) 2 α test β cfd = (A cfd /A test ) β test Charge Air Cooler Real Geometry α cfd = ( ρ cfd / ρ in ) 2 (A cfd /A test ) 2 α test CFD β cfd = ( ρ cfd / ρ in ) (A cfd /A test ) β test DENSO MARSTON LTD.
DNMN Product Development Example Results from Dual Stream Model: Charge Air Cooler Charged Air Temperature Distribution • Better cooled in the core center corresponding to the cooling air velocity profile on front face; • Charged air temperature drop: ΔT≈ 115 o C. Air flow distribution matches front grille DENSO MARSTON LTD.
DNMN Product Development Example Results from Dual Stream Model: Radiator Coolant Temperature Distribution • Better cooled on one side due to the cooling air velocity profile on front face; Air flow distribution matches layout • Coolant temperature drop: ΔT≈ 6 o C. (more complex than CAC) DENSO MARSTON LTD.
DNMN Product Development Comparison of 1D KULI and 3D CFD results • Cooling air velocity and temperature fields from CFD dual stream heat exchanger model used by KULI to compare the heat rejection and pressure drop predictions; • Working conditions modeled in CFD and KULI: Mass flow rate and inlet temperature of internal fluid in each heat exchanger e.g. coolant, charge air and oil; Ambient temperature. DENSO MARSTON LTD.
DNMN Product Development Comparison of CFD and Initial KULI Model Results D P cold stream D P hot stream Heat transfer rate (%) (%) (%) KULI CFD KULI CFD KULI CFD Radiator 103 100 99 100 95 100 Oil Cooler 140 100 99 100 136 100 Charge Air 96 100 90 100 95 100 Cooler • Big discrepancy in Oil Cooler predictions DENSO MARSTON LTD.
DNMN Product Development KULI Model Set-up Based on CFD Results T1 Uniform cooling air temperature T2 T3 T4 Basic 1D KULI model Improved 1D KULI model requires STAR-CCM+ Simulation 4 blocks with targeted Ambient temperature 2D temperature map temperatures from CFD plus uniform warm up DENSO MARSTON LTD.
DNMN Product Development KULI Model Set-up Based on CFD Results • Dummy plane in front of heat exchangers to show cooling air inlet temperature distribution; • From CFD results, 4 separate inlet temperature targets / zones are required in the KULI model. DENSO MARSTON LTD.
DNMN Product Development KULI Model Set-up Based on CFD Results RAD Oil Cooler m 3 m 1 m 2 m cfd = m 1 = 0.24 kg/s m KULI = m 1 + m 2 = m 3 = 0.404 kg/s • In basic KULI model, cooling air mass flow through oil cooler is m 3 which is higher than real condition & CFD; • From CFD results, a separate mass flow target is required for the oil cooler. DENSO MARSTON LTD.
DNMN Product Development KULI Model Set-up Based on CFD Results 1. Two mass flow targets, one of which is for Oil Cooler; 2. Four blocks; 3. Four cooling air inlet temperature targets; 4. Three resistance matrixes; 5. No resistance matrix for oil cooler. DENSO MARSTON LTD.
DNMN Product Development Comparison of CFD and Improved KULI Model Results D P cold stream D P hot stream Heat transfer rate (%) (%) (%) KULI CFD KULI CFD KULI CFD Radiator 105 100 99 100 103 100 Oil Cooler 94 100 99 100 95 100 Charge Air 96 100 90 100 95 100 Cooler • Good correlation between KULI and CFD models DENSO MARSTON LTD.
DNMN Product Development Conclusions and Summary • Standard procedure for coupling KULI and CFD requires multiple iterations and is not practical in this case; • The dual stream heat exchanger model in STAR-CCM+ is efficient and was used successfully to simulate the cooling system of the 40-ton truck; • STAR-CCM+ can be used to help generate an improved KULI model; • STAR-CCM+ and KULI predictions agree well. DENSO MARSTON LTD.
DNMN Product Development THANK YOU DENSO MARSTON LTD.
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