Hot & Cold: Schaeffler’s Thermal Management for a … · Hot & Cold: Schaeffler’s Thermal...

N O D H I O E A S M I O u E N l O A N G A D F J G I O J E R u I N K O P J E W l S P N Z A D F T O I E O H O I O O A N G A D F J G I O J E R u I N K O P O A N G A D F J G I O J E RO I E u G I A F E D O N G I u A M u H I O G D N O I E R N G M D S A u K Z Q I N K J S l O G D W O I A D u I G I R Z H I O G D N O I E R N G M D S A u K N M H I O G D N O I E R N GY H A S G S V N P I c R W Q S V G l R T u F R S F V N K F N K R E W S P l O C Y Q D M F E F B S A T B G P D R D D l R A E F B A F V N K F N K R E W S P D l R N E F B A F V N K F NM P B D T H M G R x o D P B D l D B E u B A F V N K F K F N K R E W S P l O C Y Q D M F E F B S A T B G P D B D D l R B E Z B A F V R K F N K R E W S P Z l R B E O B A F V N K F NT R u H e A T N f l o w A S G S V N P I Z R W Q S C G Z N J I M N S T u K Z Q I N K J S l W O I E P N N B A u A H I O G D N P I E R N G M D S A u K Z Q H I O G D N W I E R N G M DO Z B E m M D S A u l A R N H I O G D N O I P R N G M G M D S A u K Z Q I N K J S l W O Q T V I E P N Z R A u A H I R G D N O I Q R N G M D S A u K Z Q H I O G D N O I Y R N G M DJ I C K p I J G R D i K I O P M N E S W l N C A W Z Y Z Y K F E Q l O P N G S A Y B G D S W l Z u K O G I K C K P M N E S W l N C u W Z Y K F E Q l O P P M N E S W l N C T W Z Y KT M Q O e N T Z D S n O M G D N V u S G R V l G R A K A K G E C l Z E M S A C I T P M O S G R u C Z G Z M O Q O D N V u S G R V l G R M K G E C l Z E M D N V u S G R V l G R x K Gu G I N R l u J G D g N G R E E O M N Y A Z T E F N A N A x J R C N I F Z K M N D A B O N Y A M E C R J G N I N E E O M N Y A Z T E W N l x J R C N I F E E O M N Y A Z T E W N Y xO S A N A B D P M N V C S E Y l I N E W C l V V V H N H N V u A J K u V x E S Y M N R E E W C l O M E P S C V C Y l I N E W C l V V F H N V O A J K u V Y l I N E W C l V V F H N VI J C Y T H I N C W Q Y J A O B R N l N F x T J G l D l D Q F H B V T G u P W Q V Z E S l N F A M u A N J Y Q Y O B R N l N F x T J O l D Q F H B W N G O B R N l N F x T J O l D QE l Q P u S E B u N O P l M Q A Y C B E F V B N C T E T E N A O D F E C K T A C T S V Q D E F B N I M B l P O P Q A Y C B E F V B N R T E N A O D F E C Q A Y C B E F V B N R T E NP E I B R O P B D E G B E Q P M N E S W l N C A P Z Y Z Y K F E Q l O P N G F G R G H N W E D W C Y Q B E B G B A Y x S W A D C B P l M I J N T B G H u A Y x S W A D C B P l M I JE H V N e W E D C V B N H Z u I O P l K u H G F T S A S A C V B O F E T Z H N A x C F T J K J Z M H Z D H N B N u I O P l K u H G F D S A C V B O F E T u I O P l K u H G F D S A CO E Q R H P O I u Z T R E W Q H G F D l G E N D R R T R T C A S N I N R O A x E V E D K D l A G Q S W I E R T R Q H G F D l G E N D E R T C A S N I N R Q H G F D l G E N D E R T CF S N E m Z H A O G W E S C B u P S K u P P l u Y G S G S G E B E R Z Y l I N D E R Z N u B F I M B C H S E H E B u P S K u P P l u N G S G E B E R Z Y B u P S K u P P l u N G S GB I N C A G B Z N J I O P S D C V F E W C V T E E N M N M Z G O H A S E D C K l P S x W E W C E C B S T P O I O D C V F E W C V T E B N M Z G O H A S E D C V F E W C V T E B N M ZI K D O i N T Z D S Q O M G l K J H G F D S A M O B V B V C x Y M l M O K N I N B H u Z G F D G V T Q u J x R E l K J H G F D S A M M B V C x Y M l M O l K J H G F D S A M M B V C

D O N G n H M G R I B D P B P H C E Q A Y W S x Z E C E C R F V E G B Z H N u J M I K O Q A Y l M R T x A G Y W P H C E Q A Y W S x E E C R F V E G B Z P H C E Q A Y W S x E E C RM F I J T R I u Z T R E W Q B Z G V T F C R D x V S N S N W A S R E C V F H K N u T E Q T F C x V N H O u B I J B Z G V T F C R D x E S N W A S R E C V B Z G V T F C R D x E S N WT V D G e E C l P Q A C E Z Y C B M W R Z I P V O N M N M I Q W u R T O I J E u H B Z G W R Z V T F l u J A D G Y C B M W R Z I P S F H K T V N Z l M O Y C B M W R Z I P S F H K TZ G E T n l M O K N I J u H M B C Y N V x A D G B l K l K H E S Y S C B F G M H T I l Q N V x D B P O R u T E T M B C Y N V x A D G J l K H E S Y S C B M B C Y N V x A D G J l K HV W M C A W u u M P I Z R W O u Z T W H N E D K u N W P O N C A l V I K N D V S G W J P N E D C S K u P O W R W Z T W H N E D K u N W P O N C A l V I K Z T W H N E D K u N W P O NA K D P n K P S D F G H J K l P O I u Z T R E W Q Y x C V B N M I Q W u R T Z B C S D G T R E H K l P F l K J K O I u Z T R E W Q Y x C V B N M I Q W u O I u Z T R E W Q Y x C V Bl S J T c S Y K J H G F D S A Y V N P I Z R W Q S C G Z N J I M N S T R E C l P Q A C E Z R W D x A Y H A S G S V N P I Z R W Q S C G Z N J I M N S T R V N P I Z R W Q S C G Z N JE K J R e K O I J G R D C K I O P M N E S W l N C x W Z Y K F E D I O P N G S A Y B G D S W l Z u K O G I K C K P M N E S W l N C x W Z Y K F E D I O P P M N E S W l N C x W Z Y KM O T Y Q O G N T Z D S Q O M G D N V u S G R V l G R V K G E C E Z E M S A C I c P M R S G R u C Z G Z M Q G O D N V u S G R V l G R V K G E C E Z E M D N V u S G R V l G R V K GT N u E I N R l u J G D I N G R E x O M N Y A Z T E W N F x J l R N I F Z K M N o A B O I Z Q A T S l O K Z I N E x O M N Y A Z T E W N F x J l R N I F E x O M N Y A Z T E W N F xD C O O V C E S O P M N V C S E Y l J N E W C l V V F H N V R D J K u V x E S Y m N R E Z W C l O M E P S C V C Y l J N E W C l V V F H N V R D J K u V Y l J N E W C l V V F H N VJ Y I Z Q Y A H I N C W Q Y J A O B R E l N F x T J O l K Q F H B Q F G u P W Q p Z E G l N F A M u A N J Y Q Y O B R E l N F x T J O l S Q F H B Q F G O B R E l N F x T J O l A QN J K V N J R A K D O B N J O R O I D F N G K l D F M G O I Z P M F D R N Q B O A R x W N G K M N S R D O J N J O I D F N G K l D F M G O I Z P M F D R O I D F N G K l D F M G O IA A O O u A N D O N G I u A R N H K O G D N O I E R N G M G S A u K Z Q I N K J c l T O M P l I E P N N R A u A H I O G D N O I E R N G M T S A u K Z Q H T O G D N O I E R N G M Ku D M B B D B H M G R E B D P B D l R B E F B A F V N K F N K R E W S P l O C Y T G M F E F B S A T B G P D B D D l R B E F B A F V N K F N Q R E W S P D l R B E F B A F V N K F NA A O E u A N D O N G I u A R N H I O G D N O I E R N G M D S A G K Z Q I N K O Z l W I K A P I E P N N R A u A H I O G D N O I E R N G M D S A l K Z Q H I O G D N O I E R N G M DM O T M Q O G N T Z D S Q O M G D N V u S G R V l G R V K G E C l Z E M S A C I m P M O S G R u C Z G Z M O Q O D N V u S G R V l G R V K G E C l Z E M D N V u S G R V l G R V K Gu D M T B D B H M G R I B D P B D l R B E F B A F V N K F N K R E W S P l O C Y o D M F E F B S A T B G P D B D D l R B E F B A F V N K F N K R E W S P D l R B E F B A F V N K F NF E I D R E Q R I u Z T R E W Q l K J H G F D S A M M B V C x Y M l M O K N I J D H u Z G F D G V T Q u O T R E l K J H G F D S A M M B V C x Y M l M O l K J H G F D S A M M B V CC I M N S T R E C l P Q A C E Z R W D x A Y H B M W R Z o i l I T e m p e R A T u R e O Q A Y l M R T x A Z Y W P H C E Q A Y W S x E E C R F V E G B Z P H C E Q A Y W S x E E C RP J M N I J H l M O K N I J u H B Z G V T F C R D x E S N W A S R E C V F H K N l T E Q T F C x V N H O u B I J B Z G V T F C R D x E S N W A S R E C V B Z G V T F C R D x E S N WC G T J D G l E T u O A D G J l Y C B M W R Z I P S F H K T V N Z l M O I J E u e B Z G W R Z V T F l u J R D G Y C B M W R Z I P S F H K T V N Z l M O Y C B M W R Z I P S F H K TJ T Z u E T O I Z R W Q E T u O M B C Y N V x A D G J l K H E S Y S C B F G M H T I l Q N V x D B P O R u T E T M B C Y N V x A D G J l K H E S Y S C B M B C Y N V x A D G J l K HV W M O R W u u M P I Z R W O u Z T W H N E D K u N W P O N C A l V I K N D V S G W J P N E D C S K u P O W R W Z T W H N E D K u N W P O N C A l V I K Z T W H N E D K u N W P O NA K D l J K P S D F G H J K l P O I u Z T R E W Q Y x C V B N M I Q W u R T Z B C S D G T R E H K l P F l K J K O I u Z T R E W Q Y x C V B N M I Q W u O I u Z T R E W Q Y x C V Bl S J A D S Y K J H G F D S A Y V N P I Z R W Q S C G Z N J I M N S T R E C l P Q A C E Z R W D x A Y H A S E S V N P I Z R W Q S C G Z N J I M N S T R V N P I Z R W Q S C G Z N JE K J I C K O I J G R D C K I O P M N E S W l N C x W Z Y K F E D I O P N G S A Y B G D S W l Z u K O G I K C K P M N E S W l N C x W Z Y K F E D I O P P M N E S W l N C x W Z Y Kl S J A D S Y K J H G F D S A Y V N P I Z R W Q S C G Z N J I M N S T R E C l P Q A C E Z R W D x A Y H A S u S V N P I Z R W Q S C G Z N J I M N S T R V N P I Z R W Q S C G Z N JE K J I C K O I J G R D C K I O P M N E S W l N C x W Z Y K F E D I O P N G S A Y B G D S W l Z u K O G I K C K P M N E S W l N C x W Z Y K F E D I O P P M N E S W l N C x W Z Y KM O T M Q O G N T Z D S Q O M G D N V u S G R V l G R V K G E C E Z E M S A C I T P M O S G R u C Z G Z M O x O D N V u S G R V l G R V K G E C E Z E M D N V u S G R V l G R V K GT N u G I N R l u J G D I N G R E x O M N Y A Z T E W N F x J l R N I F Z K M N D A B O B N x Z P E W N Q M I N E x O M N Y A Z T E W N F x J l R N I F E x O M N Y A Z T E W N F xD C O S V C E S O P M N V C S E Y l J N E W C l V V F H N V R D J K u V x E S Y M N R E I W C l O M E P S C V C Y l J N E W C l V V F H N V R D J K u V Y l J N E W C l V V F H N VM O T M Q O G N T Z D S Q O M G D N V u S G R V l G R V K G E C E Z E M S A C I T P M O S G R u C Z G Z M A x O D N V u S G R V l G R V K G E C E Z E M D N V u S G R V l G R V K GA A O R u A N D O N G I u A R N H I O G D N O I E R N G M D S A u K Z Q I N K J S l W O Z W u I E P N N R A u A H I O G D N O I E R N G M D S A u K Z Q H I O G D N O I E R N G M D

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Hot & ColdSchaeffler’s Thermal Management for a CO2 Reduction of up to 4 %

Michael Weiss

304 30521Thermal Management

Introduction

Improved and variable use of the heat flows in a vehicle is a requirement for fur-ther reducing emissions and fuel con-sumption and increasing the air condition-ing comfort in passenger cars. The integrated turbochargers (ITL) increasing-ly used in vehicles place increased re-quirements on cooling systems. ITLs re-quire a predictive cooling system if possible instead of a system, which reacts to different operating conditions. This re-quirement cannot be met with conven-tional thermostats because thermostats have a delayed reaction to energy input into the cooling system and also suffer from pressure losses.

Innovative mechatronic components are required for making a predictive cal-culation of the cooling requirements from the engine load and speed. Schaeffler’s thermal management modules (TMM) are able to adjust the coolant flow to zero, for example, in order to achieve accelerated heating of the engine. At the same time,

they are able to decouple thermal masses and thus dissipate quantities of energy to other components such as the engine oil, transmission oil, heater or traction battery via the residual mass. In contrast to con-ventional thermostats (Figure 1) TMMs are controlled using a load-based calculation model. This allows the integration of a large number of connected components as well as a narrow temperature range of +/-2 °C.

The first multifunctional thermal management module in volume production

The first volume produced engine to be equipped with a multifunctional thermostat is the Audi 1.8-liter TFSI engine (four-cylin-der in-line engine EA888Gen.3). This mod-ule was developed jointly by Audi and Schaeffler (Figure 2).

In the warm-up phase of the engine, the ther-mal management module is able to com-pletely close the coolant inlet in the engine or set a minimum flow rate. If the engine is warm from operation, the coolant temperature can be adjusted quickly and fully variably to dif-ferent temperature levels depending on load requirements and external boundary condi-tions [1]. The thermal management module has two coupled rotary slide valves, which are operated by only one drive motor. One of these rotary slide valves is on the pressure side of the water pump and is designed for shutting off the coolant. The second rotary slide valve is used for distributing coolant on the intake side. The entire cooling circuit also has switching valves to enable the flow of coolant through the heater and the transmis-sion oil heat exchanger to be switched on and off in a targeted manner.

Two rotary slide valves, which are coupled mechanically, control the flow of coolant in-side the rotary slide valve module. An electric motor drives rotary slide valve 1 via a worm

gear with a high reduction ratio. Rotary slide valve 1 is, in turn, connected with rotary slide valve 2 via a lantern pinion. Rotary slide valve 1 replaces the conventional wax thermostat and can very quickly and fully variably adjust the coolant temperature between 80 °C and 110 °C depending on requirements. In addi-tion, rotary slide valve 1 switches the coolant return from the engine oil cooler (Figure 3). The coolant water is heated 30 % faster com-pared to the previous engine with a wax ther-mostat. The time required to reach the target oil temperature is reduced by around 50 %.

The module essentially comprises high-performance plastics. The coolant-carrying parts comprise polyphenylene sulfide (PPS) with extreme levels of fill. This means the material is almost as strong as aluminum, is insensitive to media and has thermal stabil-ity. A search was made for an alternative for polytetrafluorethylene (PTFE) during the de-sign of the seal materials because the plas-tic known under the trade name Teflon is expensive and has a tendency to creep un-

Around 1922

From the engine

To the pump

Thermostat (controlled by bellows)

To the radiator

Figure 1 Early thermostat controlled by bellows

Engine connections

Fail-safe thermostat

Engine oil heatexchanger connection

DC motor withreduction gear

Rotary valve 2 for zero flow

Water pumpconnection surface

Intermediategear with lockingfunction

Radiator feed

Radiator return line

Rotary slide valve 1

Sensor plate withintegrated rotation

angle sensor

Connection for transmissionoil heat exchanger andinterior heating

Figure 3 TMM design for the Audi 1.8-liter R4 TFSI engine

Figure 2 Thermal management module in the Audi 1.8-liter R4 TFSI engine


der the influence of temperature. An alterna-tive material was developed on the basis of polyvinylidene fluoride (PVDF).

The materials used in the gears were developed by the Schaeffler Group in-house. Particular attention was paid to the selection of fiber materials. The gears oper-ate under dry running conditions because lubricants would be ejected over the oper-ating life and would no longer be effective. The seals are not pressure-dependent and are able to compensate for angular offsets due to the integration of a pretensioning spring instead of an O-ring (Figure 4).

High-precision manufacturing of the ro-tary slide valves and sealing assemblies al-lows leak rates of less than 1 liter per hour. An auxiliary thermostat ensures protection against failure. This means a return spring is not required on the drive motor and the en-ergy consumption of the TMM is minimized.

Compact to comprehensive Schaeffler solutions

Schaeffler’s thermal management mod-ules can have different designs depend-ing on customer requirements and the

available space. A particularly compact solution, for example, offers up to three regulated channels and fits into the design envelope of conventional thermostat housings (Figure 5). The integration of a temperature sensor is also possible. Stan-dardized actuators also allow efficient de-velopment. The use of technologies and materials validated in volume production is an excellent basis for a robust new de-velopment.

The development of a multifunctional module with separate circuits for the en-gine block and cylinder head (split cooling) is going in another direction. It has up to five controlled channels as well as a feed and flow control system. A high level of in-tegration is one of the advantages of the multifunctional module. In addition, only one interface is required to the control unit (Figure 6).

Maintaining the engine oil temperature

Plate-type heat exchangers of stacked-disk design are frequently used for indirect cooling with coolant. The plates are pro-vided with turbulence inserts to improve the heat transfer between the media. The design of a plate-type heat exchanger comprises a number of corrugated plates. Chambers are created between the plates, in which the heated fluid and the fluid to be heated can flow. A chamber with heated fluid is followed by a counter-flow of the fluid to be heated separated by a plate (Figure 7).

The use of an oil/coolant heat ex-changer has two advantages: The cool-ant, which heats more rapidly than the engine oil during cold starts, can be used to ensure the oil reaches its target tem-

perature more quickly. It also assists heat-ing of the pistons, which quickly reduces the piston clearance. This results in an im-proved level of particle emissions. The oil can also reach higher temperatures dur-ing engine operation. The oil can dissipate this heat to the coolant via the heat ex-changer. The ability to maintain the oil temperature within narrow limits has an advantageous effect on the stress placed on the lubricant.

Model verification

The warm-up behavior of the oil at differ-ent water temperature levels was verified experimentally on an oil cooler at Schaef-fler. The oil temperature is 20 °C on a spe-cial test setup (Figure 8) at the start of the test. The water inlet temperature is to be held constantly at 40, 60, 80 or 100 °C. Four measurements with different oil pump speeds, oil flows and water flows are carried out for every coolant tempera-ture. The measurement results are shown in Figure 9 as an example

In general, the measurements show that a higher level of friction reduction can be achieved if the water starts to flow through the oil cooler earlier rather than

Figure 5 Compact module with two to three regulated outlets

Heater Cylinder head

Cylinderblock

(Turbo)

Bypass

Radiator feed

Figure 6 Multifunctional module with integrated split cooling

Figure 7 Design of a plate-type heat exchanger

Figure 4 Rotary slide valve module for full electronic control of heat flows in the engine and vehicle


of a control valve in the oil circuit would also be a possible solution. This would al-low rapid and requirement-based control of the oil.

NEDC

When determining the standardized fuel consumption it must be taken into consid-eration that consumption is strongly influ-enced by the driving style of the driver. Today, standardized driving cycles are run in order to achieve comparable values. A synthetic speed curve, the New European Driving Cycle, was defined for Europe. Phases of constant acceleration, constant speed, constant deceleration and idling phases at zero speed are run during this cycle. The shifting points for vehicles were also defined in the NEDC because engine speed also has a large influence on fuel consumption. The NEDC is a sequence of five cycles, four identical urban cycles with a maximum speed of 50 km/h and an extra urban cycle with a maximum speed of 120 km/h. Figure 10 shows how the coolant and oil temperature affect fuel consumption.

Figure 11 also shows the speed curve in relation to time. It can be seen that the en-

gine is initially subjected to low loads. It is all the more important not to lose any energy and to quickly bring the motor up to tem-perature in this early phase.

Maintaining the temperature in the interior

After cold starting a passenger car, opti-mum air conditioning should be achieved in the passenger compartment as quick-ly as possible. A defined interior air tem-perature is recommended for comfort-able air conditioning of the interior. The fed und dissipated heat flows must be designed and adjusted to achieve this temperature.

A comfortable mean air temperature in the closed rooms of buildings is approxi-mately 22 °C according to DIN 1946-2. The mean interior air temperature in a passenger car is calculated from the arith-metic mean of the mean air temperature in the footwell and the mean air temperature in the ceiling area. The mean interior air temperature required for ensuring comfort in the interiors of passenger cars is not constant. It is dependent on the physical, physiological and intermediate influencing factors (Table 1).

later. The coolant should be used to heat the oil as quickly as possible in order to achieve a reduction in CO2 and fuel con-sumption. The oil cooler must be taken into consideration in the design of the oil circuit because the heat exchanger is a restriction at low temperatures.

The NEDC is started with a cold en-gine. This means that the oil is in a highly viscous state and can only flow through the heat exchanger with difficulty. If heat-ed coolant does not flow through the oil/water heat exchanger (OWHE) from the start, it is also not advisable to direct the oil via the OWHE. The cooler can also be bypassed until the oil is within a tempera-ture range, in which it must be cooled. This means the heat in the oil is not dissi-pated to the surroundings via the cooler or to the coolant via the heat exchanger. In both cases, this causes the heat to ac-cumulate in the oil circuit , which, in turn, means that the operating temperature can be reached more quickly. The installation

20253035404550556065

Oil

out

let

tem

per

atur

e in

°C

0 200 400 600 800 1,000 1,200

Parameter 1Parameter 2

Parameter 3Parameter 4

Measuring time in s

Parameter 1 640 8 4Parameter 2 1,290 16 8Parameter 3 1,950 24 12Parameter 4 2,470 32 16

Oil pump speed in rpm

Oilflow rate in l/min

Coolantflow ratein l/min

Figure 9 Oil outlet temperature over the measur-ing period at a coolant temperature of 60 °C for different flow rates

Toil = 60 °C

2 bar, 2,000 rpm

Tcoolant = 110 °C

400.670.680.690.700.710.720.730.740.750.76

50Oil and coolant temperature in °C

Fuel

co

nsum

pti

on

in g

/s

60 70 80 90 100 110120

Figure 10 Influence of coolant and oil temperature on fuel consumption

0 200 400 600 800 1,000 1,200Time in s

0

20

40

60

80

100

120

140

Sp

eed

in k

m/h

Figure 11 Speed curve of the NEDC

Temperature and pressure measurement points:1. Heat exchanger inlet (coolant)2. Heat exchanger outlet (coolant)3. Heat exchanger inlet (oil)4. Heat exchanger outlet (oil)

Restrictor

Heat exchanger (test part)

Coolant feed

1

2

3

4

Coolant return

Bypass

Heat exchanger for cooling the oilbetween measurements

Flow sensor

Oil pump

Figure 8 Test setup for determining the warm-up behavior of the oil


The interior air temperature perceived as comfortable depends strongly on the am-bient air temperature (Figure 12). If the am-bient air temperature is 20 °C, the interior air temperature perceived as comfortable is 22 °C. The interior temperature consid-ered to be comfortable is higher than 22°C at lower ambient air temperatures. This higher interior temperature is re-quired, for example, in order to compen-sate for the thermal radiation dissipated to enclosing surfaces. The optimum temper-ature at high ambient air temperatures is also over 22 °C because, for example, lighter clothing is worn.

Influence of different shut-off systems on comfort

As part of the measurements for a master thesis supervised by Schaeffler, tests were carried out to determine which strategy heats the engine and coolant more quickly than the standard strategy and what influ-ence the different strategies have on heat-ing the passenger compartment. A pas-senger car was driven on a rolling test stand under the specified loads for the measurements.

Measurements were carried out on the engine with different strategies for the coolant pump. These included: – the standard coolant pump, which is

permanently connected,

– a switchable coolant pump, which is controlled by the vehicle control sys-tem in accordance with the cold-start strategy of the automobile manufac-turer,

– a coolant pump which is disconnected in the warm-up phase and is only con-nected when a defined coolant tem-perature is reached and

– a shut-off element, which prevents the thermo-syphon effect

In order to assess the different coolant pump strategies, the engine was initially operated with the coolant pump discon-nected (thermo-syphon effect permitted) and subsequently with the coolant circuit shut off (thermo-siphon effect prevent-ed). Table 2 shows details of the test sce-narios.

The scope of the measurements included: – the coolant temperature before and

after the heater core (HC), – the temperature of the coolant after

the shut-off or after the coolant pump,

– the temperature of the air after the heater core and

– the air temperature in the interior.

Figure 13 shows a diagram of the test setup.-20 -10 0 10 20 30 40

15

20

30

25

Ambient air temperature in °C

Mea

n ai

r te

mp

erat

ure

in

vehi

cle

inte

rio

r in

°C

Figure 12 Mean air temperature in a vehicle interior depending on the ambient air temperature

Control unit

Eng

ine

SEKP

Coolant

Air

Hea

ter

core

Car

Temperature of coolant after shut-off element and water pump

Coolant temperature before and after heater core and coolant flow rate Ambient

temperature

CP - water pumpSE - shut-off element

Air temperature before and after heater core and air speed

Water pump speed

• Crankshaft speed• Coolant temperature• Pedal travel• Throttle valve• Lambda• Temperature of intake air• Temperature of engine oil

Measurement on the roller:• Torque• Speed

Temperature on the center console ventilation system

Car interior

Figure 13 Diagram of the test setup

Factors influencing thermal comfort

Physical Physiological Intermediate factors

• Enclosing surfaces

• Solar radiation

• Air temperature

• Air flow

• Humidity

• Activity

• Status

• Skin moisture level

• Clothing

• Number of occupants

Table 1 Factors influencing thermal comfort

Measuring time

Standard (cyclical CP)

Standard (SE opens in cycle times as in 1)

Coolant pump switched on after motor start

Coolant pump disconnected (CP switched on after coolant temperature reaches 50 °C)

Coolant pump disconnected (CP switched on after coolant temperature reaches 80 °C)

Shut-off element closed (SE opens after same time as in 4)

Shut-off element closed (SE opens after same time as in 5)

15 min x

15 min x

15 min x

15 min x

15 min x

15 min x

15 min x

1

2

3

4

5

6

7

** 5 kW at 2,000 rpm (crankshaft)

Load5 kW**

Table 2 Test scenarios


The measurement point for the interior tem-perature was at the height of the head re-straint on the passenger side (Figure 14 left). The measurement of the air speed after the heater core is carried out after the fan (Figure 14 bottom right). Figure 14 shows the measurement point before

the coolant pump at top right.

Figure 15 shows the coolant temper-ature curve at the measurement point before the coolant pump depending on the switching strategy. This curve progression is simi-lar to the coolant temperature curve after the heater core. A temperature increase during the “stationary coolant” phase can be seen. For the curves with the strategy “cycli-cal coolant pump”

and the coolant pump that is connected above a coolant temperature of 50 °C, there is only a slight effect before connecting the coolant pump. For the strategy, in which the coolant pump is connected above a coolant temperature of 80 °C, a significant increase of the coolant temperature is noticeable be-fore the coolant pump is connected. The increase for the measurements with a shut-off is significantly larger than for the mea-surements without a shut-off.

For the measurements at the measure-ment point before the coolant pump, heat transfer is only possible by means of ther-mal conduction in the coolant if the coolant pump is disconnected. The heat transfer for the measurement without a shut-off ele-ment continues in the coolant pipe. The coolant in the measurements with a shut-off element can only be heated as far as the shut-off element. The coolant is continu-ously heated at the measurement point be-fore the engine inlet without any heat dis-sipation due to the shut-off in the pipe. Therefore, the coolant temperature mea-

sured at this position is higher than the cool-

ant temperature in the test without a shut-off element.

After the pump is connected at 124 sec-onds and 215 seconds, there is initially a short drop in temperature, because cooler coolant is fed from the heater core and pipes to the measurement point. This is fol-lowed by a significant increase in tempera-ture due to the warm coolant, which was heated in the motor and now reaches the measurement point.

With the cyclical coolant pump strate-gy, temperature differences occur with de-lays after the coolant pump is connected. Initially, the warm coolant is moved through the circuit by the pump, until it reaches the engine inlet. The coolant temperature drops only slightly during the periods when the coolant pump is disconnected. The coolant only loses heat slowly because heat continues to reach the measurement point from the engine due to heat conduc-tion in the coolant. The curves with the cy-cled coolant pump strategy catch up the other curves after the pump has been con-nected four times. The curves for all strate-gies have the same progression after per-manent connection of the coolant pump,

whereby the curve with the cyclical cool-ant pump is slightly higher. The strategy for the cyclical coolant pump has the lon-gest coolant pump disconnection times. This means a very small quantity of heat is dissipated from the engine, which is why the engine and coolant are heated mini-mally faster.

The heating characteristics of the air af-ter it exits the heater core due to different heating strategies can be seen in Figure 16. This shows that the air temperature curve with a coolant pump that is permanently connected cannot be improved by any of the air temperature curves of the other strategies. Above 550 seconds, the curves

of all the coolant pump strategies lie on top of each other. Heating up the air requires different periods of time depending on the strategy. The earlier the heat is transferred to the HC, the earlier the air will be heated. The greater the quantity of heat transferred to the HC, the faster the air will be heated.

The measured interior temperature de-pending on different heating strategies is plotted in Figure 17. These curves follow the air temperature curve after the heater core,

102030405060708090

100

Tem

pera

ture

in

°C

0 100 200 300 400 500 600 700 800Time in s

CP switched on after motor startCP with SE switched on after 124 sCP with SE switched on after 215 sCyclical CP with SE

Figure 15 Coolant temperatures for different coolant pump strategies

102030405060708090

Tem

pera

ture

in

°C

0 100 200 300 400 500 600 700 800Time in s


Figure 16 Air temperatures with different coolant pump strategies after the heater core

10

20

30

40

50

60

70

Tem

pera

ture

in

°C

0 100 200 300 400 500 600 700 800Time in s


Figure 17 Comparison of the air temperature in the interior.

Figure 14 Measurement points in the test setup


however, they have a different gradient. The air, which exits the heater core, mixes with the air in the passenger compartment after it leaves the noz-zles. A change of temperature there-fore requires a lon-ger period due to the large quantity of air in the vehicle in-terior. The strategy, with which the inte-rior is heated most quickly, is the strat-egy with the coolant pump permanently connected. The less the coolant pump is connected in the heating phase, the more slowly the in-terior will be heated.

The measure-ments carried out to determine cool-ant and air temperatures at different measuring points in the warm-up phase of the engine show that the strategy with a coolant pump that is permanently con-nected is still the most appropriate for heating the interior of a passenger car as quickly as possible. Other coolant pump strategies with disconnected phases do show a faster heating phase after the coolant pump is connected, but are not an improvement on the curve with the coolant pump that is permanently con-nected. These results show that a switch must be made to the strategy with a coolant pump that is permanently con-nected as soon as a passenger operates the heater – customer satisfaction is the highest priority.

Cold-start strategies

Schaeffler modified a conventional naturally aspirated engine and replaced the thermo-stat control system with a thermal manage-ment module in order to verify the effects of a TMM on cold starting (Figure 18).

The system is able to distribute or shut off the coolant due to the combination of a coolant pump and two valves instead of a coolant pump and a thermostat. The shut-off function is particularly attractive for the cold-start strategy. This has a significant in-fluence on the fuel consumption figures in the NEDC. Schaeffler tested two different operating strategies for the TMM with this

setup: Zero flow for quick heating and load-based temperature variations (part load 110 °C, full load 85 °C) (Figure 19).

The temperature curve in Figure 19 does not correspond with the real values because motion of the coolant and a change in coolant temperature do not occur until after 100 sec-onds. The temperature can subsequently be

maintained at a constant level +/- 2 °C using a simple calculation model. This system can re-act immediately to the driver’s load require-ments and significantly reduce the tempera-ture. The zero flow strategy alone resulted in a reduction in fuel consumption of 1.2 %. In ad-dition, significant reductions in secondary ex-haust gases such as HC, NOX or CH4 were achieved by means of the higher exhaust gas temperature and operation of the catalytic converter at an earlier stage (Figure 20). Even though these results are impressive at first glance, the full potential can only be realized in close collaboration with heat physicists from automobile manufacturers.

Gasoline Technology Car

Schaeffler has built a concept vehicle called the Gasoline Technology Car (GTC) using advanced components on the basis of a

Car speed

Average value of cylinder head outlet coolant temperature with base engineAverage value of cylinder head outlet coolant temperature with TMMCylinder head outlet coolant temperature in different TMM control modes

Car

sp

eed

in h

/km

Co

ola

nt t

emp

erat

ure

in °

C

Rapid warm-up

due to zero flow

With TMM, the warm up time (25 °C to 90 °C) has been decreased by 130 scompared with base engine

At part load, the coolant temperaturewith TMM is nearly 15 °C

higher than compared to base engine

Allows fastadjustment to any coolant temperature

130 °C

Figure 19 Load-based temperature control on a modified naturally aspirated engine

0 %

5 %

10 %

15 %

20 %

HC CO NOX CO2 HC+NOX CH4

HC CO NOX CO2 HC+NOX CH4

Benefit

Emission Benefit

8 % 6 % 18 % 1 % 13 % 8 %

Figure 20 Reduction in secondary exhaust gases due to operation of the catalytic converter at an earlier stage

Coolant temperaturesensor 1located on cylinderhead outlet port

TMM forbypass

TMM2 forradiator

Figure 18 Modified naturally aspirated engine with a TMM


Ford Focus with a 1.0 liter Fox engine. The original engine has two thermostats. One of the thermostats is used for block control, the second operates the radiator. These two thermostats were replaced in the GTC by a TMM, which bundles the functions and is also able to switch the oil cooler on and off (Figure 21).

In contrast to the original engine, it is possible to realize a zero flow due to the integration of the TMM. The required mod-ule is so compact that it can be fitted in the existing design envelope of the main ther-mostat. The results of the first tests show a significant increase in the thermal and me-chanical efficiency (Figure 22). Also in the GTC, the significantly faster increase in the temperature of the exhaust gas leads to a more rapid response of the catalytic con-verter and reduced secondary exhaust gases.

The heating of the oil is slower despite the steeper heating curve because there is no flow through the oil/water heat exchang-er in the initial phase. The objective is to achieve the optimum switching point be-

tween thermal and mechanical efficiency. This depends on both the engine architec-ture and the parameters of the engine oil used. The closer the collaboration with the automobile manufacturer, the more efficient the realization of potential will be.

Even though the presented results are only an approximate model of the first tests, these measurements show that the differ-ence in temperature gradients is significant and the system offers an additional degree of freedom for engine design. Fine calibra-tion of the engine control unit at Continental will result in a significant smoothing of the curves.

Design of the cooling circuit for conventional powertrains

A multi-stage design is recommended for future cooling circuits of conventional pow-ertrains on the basis of the findings present-ed in this article. A zero flow phase should initially ensure that the interior of the engine is heated in order to enable a rapid reaction of the catalytic converter. A bypass with an integrated oil cooler or heater offers the required flexibility. The decoupling of the OWHE from the bypass with variable inlet control allows an additional degree of free-dom.

After dealing with the engine control, the conditioning of the transmission must be taken into consideration. The requirements for transmissions will also increase due to the increasing number of gear ratios and bearing positions. There is still a large potential for increasing the efficiency of hydraulically actuated transmissions. Initial tests have already been carried out on dou-ble clutch transmissions.

The radiator’s control system should de-couple as much thermal mass as possible. This means the focus can be placed on ef-ficiency with normal or warm ambient air and on comfort with cold ambient air. The use of finely regulated systems instead of conventional on/off switches offers signifi-cant potential.

Outlook

Mechatronic systems for coolant control are a trend with the potential to optimize the fuel consumption and emission characteristics of vehicles and at the same time increase the air conditioning comfort in vehicle interi-ors. This results in a wide range of design options for specific designs depending on the configuration of the powertrain. As a partner with a holistic approach in develop-ment and production, Schaeffler offers con-cepts with a wide range of options.

Literature

[1] Eiser, A.; Doerr, J.; Jung, M.; Adam, S.: Der neue 1,8-l-TFSI-Motor von Audi. MTZ 6/2011, pp. 466-474

Faster warm-up offers potential for increased efficiency and passenger comfort

Exhaust valve bridgeCylinder liner top

Thermal Efficiency

Mechanical efficiencyCylinder liner centerEngine oil

OriginalModified

0

100

200

300

400

500

20

40

60

80

100

120

140

Tem

per

atur

e in

°C

Ro

tary

slid

e va

lve

ang

le in

°

0 500 1,000 1,500

Bypass open

Heat control

Zeroflow

Heatingof oil

Time in s

Figure 22 Faster heating for increased efficiency and comfort

U

Thermostats replaced by a module: higher functionalityquick responsereduced assembly costs

Degasbottle

Turbo

Original Modification with TMM

Cyl. head, exhaust side

Oil cooler

Rad

iato

r

Cabinheater

Cyl. head, intake side

Cyl. head, exhaust sideCyl. head, intake side

Cyl. blockBlockthermostat

Thermostatwith bypass

Coolantpump

EGRcooler

System scopeContinental

TH

Degasbottle

Turbo Oil cooler

Rad

iato

r

Cabinheater

Cyl. blockCoolantpump

Figure 21 Design of the GTC with advanced Schaeffler components

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