Simulating the Idle: A New Load Case for Vehicle Thermal Management

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1 Simulating the Idle: A New Load Case for Vehicle Thermal Management Jan Eller FKFS / IVK University of Stuttgart Thomas Binner and Heinrich Reister Daimler AG Nils Widdecke and Jochen Wiedemann FKFS / IVK University of Stuttgart STAR Global Conference 2016, Prague Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart

2 Testing for elastomer components needs collective data, maximum temperature is not sufficient Engine mount Component failure Temperature limit exceeded Propeller shaft disc Component failure Temperature limit never exceeded Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 2

3 Goal: Replacing endurance testing as the source for component temperature collectives Starting point endurance testing: 100 Component temperature in C Collective based on endurance testing 0, Time in hours Example: front suspension mount Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 3

4 Component temperature in C Goal: Replacing endurance testing as the source for component temperature collectives Current component testing process: Thermal testing Collective based on endurance testing Thermal and mechanical testing 0, Time in hours Example: front suspension mount Optional Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 4

5 Goal: Replacing endurance testing as the source for component temperature collectives New definition of testing temperatures with support points: 100 Component temperature in C Collective based on endurance testing 0, Time in hours Example: front suspension mount Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 5

6 Goal: Replacing endurance testing as the source for component temperature collectives New definition of testing temperatures with support points: 100 Component temperature in C , Time in hours Example: front suspension mount Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 6

7 Goal: Replacing endurance testing as the source for component temperature collectives Support points are load cases for simulation: 100 Component temperature in C Slow Uphill Drive with Trailer Idle 0, Time in hours Example: front suspension mount Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 7

8 Experimental data for the Idle load case is collected at the Daimler Climatic Wind Tunnel The load case is usually performed during Death Valley testing A wind tunnel is used for better repeatability Roller shutter and bypass openings to simulate zero-velocity conditions Approximation of open-field conditions Source: ATZ Extra, Mercedes-Benz S-Klasse, July 2013 Preconditioning 30 min. Idle in D 90 min. Idle in P Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 8

9 Control is more important for low engine load, example: HVAC dominates component temperature Fan speed HVAC load Heat exchanger exit temperature Component temperature Heat rejection Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 9

10 Standard process: 3D simulation of fluid and solid models to include all heat transfer mechanisms 10 Velocity in m/s 0 Fluid model Solid model Temperature Higher Lower Air temperature and velocity Component temperature Surface temperature Fluid film temperature & heat transfer coefficient Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 10

11 In-/Outflow boundary conditions influence flow topology in the simulation box, significantly pressure outlet p = 0 Pa velocity inlet V = 0.01 m/s Standard setup - 2 Velocity in x direction in m/s + 2 Example: E Class Sedan Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 11

12 In-/Outflow boundary conditions influence flow topology in the simulation box, significantly velocity inlet V = 0.01 m/s Standard setup pressure outlet p = 0 Pa pressure outlet p = 0 Pa pressure outlet p = 0 Pa pressure outlet p = 0 Pa - 2 Velocity in x direction in m/s + 2 Idle setup Example: E Class Sedan Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 12

13 Flow topology and comparison to measurements: investigation of the Daimler Climatic Wind Tunnel Example: C Class Sedan Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 13

14 Flow topology in the wind tunnel differs from box Example: C Class Sedan Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 14

15 Higher air temperature in wind tunnel setup due to surrounding walls and insufficient ventilation Simulation in standard box Simulation in wind tunnel Example: C Class Sedan Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 15

16 Heat package inlet temperature increases with plenum air temperature T wt T box * Simulation in standard box total: +1,9 K Simulation in wind tunnel +1,3 K +1,6 K +6,9 K * surface average of air temperature; wt: wind tunnel Example: C Class Sedan Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 16

17 Underhood component temperatures are predicted correctly by the simulation model Higher Component Temperature Lower Example: E Class Sedan Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 17

18 Underhood component temperatures are predicted correctly by the simulation model Example: Temperature prediction at front suspension mounts Left T experiment -T simulation = -2.1 K Left T experiment -T simulation = -1.0 K Temperature deviation tension strut Temperature deviation spring control arm Front suspension mounts are focus of this project Deviation for other underhood parts is generally < 3 K Results for wind tunnel model are similar Right T experiment -T simulation = 2.7 K Right T experiment -T simulation = -0.8 K Higher Component Temperature Lower Example: E Class Sedan Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 18

19 Idle shown to work in standard simulation box with pressure outlets and in wind tunnel environment The presented method for predicting component temperature collectives needs additional load cases with lower engine load requirements Example load case: Idle already tested on-road Measurements: control becomes more important for these load cases Numerical simulation of the Idle load case is successful Additional investigation of climatic wind tunnel Geometry changes influence flow topology Component temperatures dominated by fan-induced flow Increase in air temperature around car in wind tunnel setup Both the standard box and the wind tunnel setup can be used to investigate component temperatures for the Idle load case Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart 19

20 Simulating the Idle: A New Load Case for Vehicle Thermal Management Jan Eller FKFS / IVK University of Stuttgart Thomas Binner and Heinrich Reister Daimler AG Nils Widdecke and Jochen Wiedemann FKFS / IVK University of Stuttgart STAR Global Conference 2016, Prague Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart