380 THERMA L MANA GEMENT 24 38124 THERMA L MANA GEMENTSchaeffler Symposium 2018 cooling output of the powertrain components or the required heat output with the latter not only referring to the vehicle interior but also to the de sired minimum operating temperature of the indi vidual powertrain components This is particular ly relevant for hybrid vehicles since on the one hand the heat inputs provided by the combus tion engine are reduced through the electric drive components and on the other the electrical en ergy stored in the battery is to be used as much as possible for propulsion alone and not for heating processes In the practical design of a thermal management system the upshot of this is that most powertrain components can be used both as a heat source as well as a heat sink Linking a thermal management control system to the driving and hybrid strategy is also essential because the cooling output in electrical opera tion is a decisive factor with regard to perfor mance For example the temporary peak perfor mance of electric motors is generally devised with a view to the admissible thermal load To this end it is necessary to be able to simulate the heat inputs occurring in cycles and in certain driving situations and the heat dissipation ca pacity with as much accuracy as possible at an early development phase already Figure 9 shows an example of the heat inputs of an electric motor during the NEDC and during full load accele ration It can be seen that despite moderate ac celeration levels the average heat input at 600 W is greater in a specifically designed tractive mo tor during the driving cycle than during a single full load acceleration 500 W The background for this is a very rapid derating of the electric mo tor in combination with a relatively high thermal mass To validate the simulation model extensive measurements were taken on a standard plug in hybrid vehicle and compared with the simulation results The measurements included the follo wing parameters Volume flows in all cooling circuits Coolant temperatures Temperatures of the engine and transmission oil Component temperatures in the electric motor and battery Charge status voltage and currents in the bat tery Heat inputs of the relevant components Heat outputs of the heat exchangers Based on the sample comparison of measure ment and simulation results for the heat exchan ger in the low temperature circuit battery cool ing Figure 10 shows that the current state of development has already achieved good model quality The system assessment answers the question re garding at what points it makes sense to use con trollable actuators for optimizing the efficiency of the overall system This gain in efficiency is to be demonstrated and quantified soon on the basis of a standard plug in hybrid vehicle modified by Schaeffler Models of the Cooling Circuit and the Thermal Management Module Beneath the complete system level a detailed simulation of the material and heat flows and the electrical signal flow is necessary for designing actively switchable and dynamically controllable cooling circuits To this end hydraulic operating modes electric loads and mechanical parame ters are coupled in a physical model that can al ready be used for virtual tests as a digital twin 9 Model calculations for the heat entry through the electric motor in the NEDC left and during full load acceleration 0 20 40 60 80 100 140 120 0 20 40 60 80 100 140 120 0 10 20 30 40 6050 70 80 0 3 0 4 0 5 0 6 0 7 Velocity Temperature E motor Heat flow E motor 0 200 400 600 800 1 000 1 200 Time in s 0 0 2 0 4 0 6 0 8 1 0 1 2 1 4 H ea r fl ow in k W Time in s Ve lo ci ty in k m h Te m pe ra tu re in C Ve lo ci ty in k m h Te m pe ra tu re in C H ea r fl ow in k W 10 Measured and simulated heat exchange in the low temperature heat exchanger of a plug in hybrid vehicle LT1 Radiator heat exchange simulation LT1 Radiator heat exchange measurement 0 200 400 600 800 1 000 1 200 1 400 6 000 5 000 4 000 3 000 2 000 1 000 0 H ea t fl ow i n W Time in s 8 Simulation model for a plug in hybrid vehicle Hybrid strategy Friction model Engine model Vehicle model E motor HV battery Transmission cycleTransmissionCooling cycleTherm engine modelEngine oil cycle Driving profile Cabin Coldcircle

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