engine vehicle integration scuola di dottorato di ricerca 2010 - road vehicle and engine engineering...

Engine Vehicle Integration

Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science

1. Combustion engines main principles and definitions

2. Reciprocating combustion engines architecture

3. Reciprocating engines dynamic properties

4. Engine components and systems

5. The engine management system for gasoline and Diesel engines

6. The emission Requirements & Technology

7. Engine vehicle integration8.

7.1 Engine layout and mounting7.2 Engine-vehicle cooling system7.3 Intake system7.4 Exhaust system

Light and heavy vehicle technology (Malcolm James Nunney - Elsevier)



Cooling system

System Targets

To extract from the engine the heat quantity necessary to

maintain the working temperature of every engine components

below the safety limit in any vehicle operating condition.

To assure the thermal balance between the heat extracted

from the engine hardware and the heat released to external

ambient through the heat exchanger (radiator) even in the most

severe vehicle operating conditions.

2



Critical engine components

Combustion chamber walls

Cylinder wall

Cylinder head

Piston

Exhaust valve

Spark plug

Gasoline / Diesel injector

Engine lubricants

Cooling system

3



Centrifugal pump

Cooling fluid

Radiator

Fan

Thermostat

System components Function

Cooling fluid circulation

Heat transfer

Heat exchange with the ambient

Air through the radiator at low vehicle speed

Engine temperature stabilization

Cooling system

4



Expansion tank (nourice)

Filler pressure cap

Passenger compartment radiator

Lubricant radiator

EGR cooling radiator (Diesel)

Fluid expansion and gas release

Cooling circuit pressure

Passenger compartment heating

Engine lubricant cooling

Exhaust gas cooling

System components Function

Cooling system

5



Heat transfer fluid Etilene glycol mixture in water (30 –60% concentration)

Water

High specific heat

Low viscosity

High heat of vaporization

Constant characteristics vs time and temperature

Etilene glycol

High thermal capacity

Low pressure drop

Low gas formation

Low freezing point

Cooling system

6


Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 7

EG Weight Percent (%)

Freezing Point (deg F)

Freezing Point (deg C)

0 32 0

10 25 -4

20 20 -7

30 5 -15

40 -10 -23

50 -30 -34

60 -55 -48

70 -60 -51

80 -50 -45

90 -20 -29

100 10 -12

Ethylene glycol freezing point vs concentration in water

Cooling system



SCHEMA CIRCUITO ACQUA MOTORE 1910 JTD - 8V - EURO 4 (impiego per FIAT e GM)

motore

riscaldatore

radiatore

term

osta

to

EG

R C

oole

r

pom

pa

nourice

scambiatore acqua/olio

spurgo A

spurgo B

spurgo C

Cooling circuit scheme

Cooling system

8



Engine-Vehicle cooling system

LEGENDALEGENDA

1 RADIATORE CON CONVOGLIATORE E 1 RADIATORE CON CONVOGLIATORE E VENTOLEVENTOLE

2 VASCHETTA DI ESPANSIONE2 VASCHETTA DI ESPANSIONE

3 MANICOTTO DA RADIATORE A POMPA3 MANICOTTO DA RADIATORE A POMPA

4 MANICOTTO DA RISCALDATORE A 4 MANICOTTO DA RISCALDATORE A POMPAPOMPA

5 RISCALDATORE ABITACOLO5 RISCALDATORE ABITACOLO

6 MANICOTTO DA TERMOSTATO A 6 MANICOTTO DA TERMOSTATO A RISCALDATORERISCALDATORE

7 POMPA7 POMPA

8 MANICOTTO DA RADIATORE A TURBO 8 MANICOTTO DA RADIATORE A TURBO

9 MANICOTTO DA TERMOSTATO A 9 MANICOTTO DA TERMOSTATO A RADIATORERADIATORE

10 MANICOTTO DA TURBO A POMPA10 MANICOTTO DA TURBO A POMPA

11 TERMOSTATO11 TERMOSTATO

Cooling system

9



Thermal balance equations 1/6Thermal balance equations 1/6

hkJigwuf QQQQQ

fQ

uQ

wQ

gQ

iQ

= heat introduced into the engine through the fuel combustion

= work equivalent heat at the engine shaft

= heat realeased to the engine cooling system

= heat rejected to the exhaust gases

= lost heat for radiance

where:

General equation for engine thermal balance

Cooling system

10



Hi = net calorific or lower heating value (KJ/Kg)

mf = fuel consumption (Kg/h)

Heat released to the engine

hkJfm•

i=H

fQ

Heat released to the cooling fluid

hkJm

Teq

AKw

Q

K = heat transfer coefficient (KJ/m2°Kh)

Aeq = heat transfer equivalent surface area (m2)

= average difference in temperature between the exhaust gas and

the coolant (°K)

mT

where:

where:

Thermal balance equations 2/6Thermal balance equations 2/6Cooling system

11



cw = (KJ/Kg°K) water calorific value (4.1868 KJ/KgK)

mw = (Kg/h) coolant flow rate

Twu = (°K) coolant temperature at the engine outlet

Twe = (°K) coolant temperature at the engine inlet

cl = (KJ/Kg°K) lubricant calorific value

ml = (Kg/h) lubricant flow rate through the water-lubricant heat exchanger

Tlu = (°K) lubricant temperature at the outlet of the heat exchanger

Tle = (°K) lubricant temperature at the inlet of the heat exchanger

hkJwe

T-wu

Twmw

cw

Q

hkJT-TmcT-TmcQ lelullwewuwww

where:

Heat released to the cooling fluid from the engine

where:

Heat released to the cooling fluid from the engine and the water-lubricant heat exchanger


12



Kr = (KJ/m2°Kh) heat transfer coefficient of the cooling radiator

Ar = (m2) radiator frontal area

Trm = (°K) average tempearture of the coolant inside the radiator

Heat released to the external ambient through the cooling radiator

hkJT-TAKQ aermrrw

K

2ru

Tre

T

rmT

Tae = (°K) air temperature at the radiator inlet which differs from the ambient

temperature Ta when the condenser radiator of air conditioning system

is installed ahead

where:


13



Ta = (°K) ambient temperature

Tboil = (°K) boiling temperature of the coolant at the pressure of the circuit

Tre = (°K) temperature of the coolant at the radiator inlet

Air Temperature to Boil index (ATB): it defines the ambient temperature boiling point of the cooling fluid ( It represents an equilibrium condition between the heat rejected from the combustion gases to the cooling fluid and the heat rejected from the fluid to the external air for a specific vehicle operation mode.

KTTTATBreboila


where:

Cooling system

14



ATB index vs Qw

ATB index could be expressed as function of the heat to be rejected from the engine into the coolant and of the radiator exchanging performances.

Without air conditioning system (Tae = Ta)

KTT

AK

Q2TATB aeru

rr

wboil

With air conditioning system

KTTTT

AK

Q2TATB aeaaeru

rr

wboil

ATB index expresses an equilibrium condition determined by the engineering design of the cooling system. ATB index expresses an equilibrium condition determined by the engineering design of the cooling system. Practically some ATB values are defined for some severe operating vehicle modes that represents the project targets.Practically some ATB values are defined for some severe operating vehicle modes that represents the project targets.


where Kr [Kw/m2·°K] is a performance exchanger parameter of the radiator

Cooling system

15



The water pump provides circulation of the engine coolant (antifreeze) through the cooling system: it pushes the coolant through the passages (water jackets) in the engine cylinder block and cylinder head and then out into the radiator. The hot coolant passes through the radiator where it cools down and then returns back to the engine.

Centrifugal pump is the most used:it is a rotodynamic pump that uses a rotating impeller to increase the pressure and flow rate of a fluid. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward or axially into a diffuser or volute chamber, from where it exits into the downstream piping system.

A water pump is usually driven by the engine through the driving belt and only sometimes by a timing belt. A water pump consists of the housing with the shaft rotating on the bearing pressed inside. At the outer side there is a pulley mounted on the shaft. At the inner side there is a seal to keep the coolant from leaking out and the impeller.

Cooling systemComponent – Water pump 1/5Component – Water pump 1/5



• Impeller diameter ( = 60 75 mm)

• Impeller height (h = 12 20 mm)

• Paddles number and design (z = 5 10)

• Axial and radial impeller clearance

• Drive ratio

engine

pump

n

n = 1.3 1.6

Main design characteristics

Component – Water pump 2/5Component – Water pump 2/5Cooling system

17



Typical values

Tw = 8 – 10°C

/Pm = 0.030 – 0.043 Kg/sKw for gasoline engines

0.025 – 0.035 Kg/sKw for Diesel engines

Typical system back pressure

0.5 2.5 bar

Setting of the coolant flow rate

The coolant pressure at the pump inlet must not be negative to avoid cavitations phenomena and therefore the inlet speed shall be limited, generally lower than 3 m/s.


18



Hydrodynamic cavitation describes the process of vaporization, bubble generation and bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in pressure. Cavitation will only occur if the pressure declines to some point below the saturated vapor pressure of the liquid. In pipe systems, cavitation typically occurs either as the result of an increase in the kinetic energy (through an area constriction) or an increase in the pipe elevation.Hydrodynamic cavitation can be produced by passing a liquid through a constricted channel at a specific velocity or by mechanical rotation through a liquid. In the case of the constricted channel and based on the specific (or unique) geometry of the system, the combination of pressure and kinetic energy can be created when the hydrodynamic cavitation cavern downstream of the local constriction generating high energy cavitation bubbles.The process of bubble generation, subsequent growth and collapse of the cavitation bubbles results in very high energy densities, resulting in very high temperatures and pressures at the surface of the bubbles for a very short time. The overall liquid medium environment, therefore, remains at ambient conditions. When uncontrolled, cavitation is damaging; however, by controlling the flow of the cavitation the power is harnessed and non-destructive. Controlled cavitation can be used to enhance chemical reactions or propagate certain unexpected reactions because free radicals are generated in the process due to disassociation of vapors trapped in the cavitating bubbles.




Typical water pump characteristic (63.5mm impeller diameter, 8 paddles of 13.5mm height, axial clearance of 0.6mm, engine drive ratio 1/1.39)

POMPA ACQUA 1250 JTD (H) Prestazioni rilevate su motore completo

0

500

1000

1500

2000

2500

3000

3500

0 2000 4000 6000 8000 10000 12000

Portata liquido [l/h]

p

[m

ba

r]

5000 n/1 - 1,6 bar

4500 n/1 - 1,6

4000 n/1 - 1,6

3000 n/1 - 1,6

2000 n/1 - 1,6

1000 n/1 - 1,6

caratteristica impianto

5450


20



Target - In internal combustion engines a thermostat is used to maintain the engine at its optimum operating temperature by regulating the flow of coolant to the external air cooled radiator. It must balance the heat rejected from the engine to the coolant and the heat rejected from the radiator to the ambient in any operating vehicle mode.

This type of thermostat operates mechanically: it makes use of a wax pellet inside a sealed chamber. The wax is solid at low temperatures but as the engine heats up the wax melts and expands. The sealed chamber has an expansion provision that operates a rod which opens a valve when the operating temperature is exceeded. The operating temperature is fixed, but is determined by the specific composition of the wax, so thermostats of this type are available to maintain different temperatures, typically in the range of 70 to 90°C. Modern engines run hot, that is, over 80°C, in order to run more efficiently and to reduce the emission of pollutants. Most thermostats have a small bypass hole to vent any gas that might get into the system, e.g., air introduced during coolant replacement, which also allows a small flow of coolant past the thermostat when it is closed. This bypass flow ensures that the thermostat experiences the temperature change in the coolant as the engine heats up; without it a stagnant region of coolant around the thermostat could shield it from temperature changes in the coolant adjacent to the combustion chambers and cylinder bores.

Wax thermostatic elements permit the transforming of thermal energy into mechanical energy. Their working principle is based on the large increase in the thermal expansion of waxes when they pass from the solid to the liquid state

Cooling system Component – Thermostat 1/4Component – Thermostat 1/4



While the thermostat is closed, the flow of coolant in the loop is greatly slowed, allowing coolant surrounding the combustion chambers to warm up rapidly. The thermostat stays closed until the coolant temperature reaches the nominal thermostat opening temperature. The thermostat then progressively opens as the coolant temperature increases to the optimum operating temperature, increasing the coolant flow to the radiator. Once the optimum operating temperature is reached, the thermostat progressively increases or decreases its opening in response to temperature changes, dynamically balancing the coolant recirculation flow and coolant flow to the radiator to maintain the engine temperature in the optimum range as engine heat output, vehicle speed, and outside ambient temperature change. If the load on the engine increases, increasing the heat input to the cooling system, or the vehicle speed decreases or air temperature increases, decreasing the radiator heat output, the thermostat will open further to increase the flow of coolant to the radiator, preventing the engine from overheating. If the conditions reverse, the thermostat will reduce its opening to maintain the coolant temperature.

Cooling systemComponent – Thermostat 2/4Component – Thermostat 2/4



Under normal operating conditions the thermostat is open to about half of its stroke travel, so that it can open further or reduce its opening to react to changes in operating conditions. A correctly designed thermostat will never be fully open or fully closed while the engine is operating normally, or overheating or overcooling would occur. For instance, If more cooling is required, e.g., in response to an increase in engine heat output which causes the coolant temperature to rise, the thermostat will increase its opening to allow more coolant to flow through the radiator and increase engine cooling. If the thermostat were already fully open, then it would not be able to increase the flow of coolant to the radiator, hence there would be no more cooling capacity available, and the increase in heat output by the engine would result in overheating. If less cooling is required, e.g., in response to decrease in ambient temperature which causes the coolant temperature to fall, the thermostat will decrease its opening to restrict the coolant flow through the radiator and reduce engine cooling. If the thermostat were already fully closed, then it would not be able to reduce cooling in response to the fall in coolant temperature, and the engine temperature would fall below the optimum operating range. Modern cooling systems contain a relief valve in the form of a spring-loaded radiator pressure cap, with a tube leading to a partially filled expansion reservoir (most recent applications use to have the pressure cap directly on the expansion reservoir – see slides 25/26). Owing to the high temperature, the cooling system will become pressurized to a maximum set by the relief valve. The additional pressure increases the boiling point of the coolant above that which it would be at atmospheric pressure.The wax product used within the thermostat requires a specific process to produce. Unlike a standard paraffin wax, which has a relatively wide range of carbon chain lengths, a wax used in the thermostat application has a very narrow range of carbon molecule chains. The extent of the chains is usually determined by the melting characteristics demanded by the specific end application. To manufacture a product in this manner requires very precise levels of distillation, which is difficult or impossible for most wax refineries.

Cooling system Component – Thermostat 3/4Component – Thermostat 3/4



Typical thermostat characteristicOpening temperature 882 °C

Valve stroke of 9.5mm at 101105 °C

0

2

4

6

8

10

12

80 85 90 95 100 105 110

temperatura [°C]

co

rsa

va

lvo

la [

mm

]

ISTERESI 1.3 °C

1-Cooling systemComponent – Thermostat 4/4Component – Thermostat 4/4

24



Main target

To absorb the expansion of the coolant as it gradually increases into full operating temperature.

To generate pressure at the pump inlet to avoid cavitations phenomena.

To remove bubbles from the entire cooling system to absorb heat much faster.

To assure a coolant reservoir sufficient for the maintenance-free target

To fit the filler neck (the mouth of the header tank) covered with a pressure cap, which forms an air-tight joint due to which the coolant is maintained at some pressure higher than the atmospheric (generally 1.4-1.6 bar). Using the pressure cap brings about the following advantages in the cooling system: Elevating the boiling point: the engine can operate at higher temperatures without boiling the liquid coolant within. Allows for the usage of smaller tanks for the same engine sizes. Prevents any coolant to be wasted or drained away and maintains a self regulated system that can go maintenance free.

Component – Component – EExpansion reservoir and pressure cap 1/51-Cooling system



The reservoir is connected to the radiator that it receives the excess coolant as the engine temperature increases. When the liquid cools down, its volume decreases and the coolant in the reservoir returns to the reservoir to keep the coolant level in the cooling system optimal. This system is also known as coolant recovery system and it helps to prevent loss of coolant, doesn’t allow air to come into the system and allows for a smaller header tank. The expansion tank is a see-through plastic container that has to be mounted into the overflow tube from the radiator. With a properly working expansion bottle, radiator is always full even if the coolant inside it rises and falls. As a general rule, standard expansion tank volume is approximately 20 to 30-percent of the estimated volume of the specific thermal fluid of the system circuit. A pressure cap contains a pressure valve and a vacuum valve. If in severe operating conditions, the coolant starts to boil or to vaporize, the pressure in the system builds up and exceeds a certain pre-determined value , the pressure blow-off value, which operates against a pre-tensioned spring, opens releasing the excess pressure to the atmosphere through the over flow pipe.




The expansion tank should be located about the level of the radiator header tank.


27



Typical installation of the expansion reservoir inside a complex layout of the engine bay for a small segment vehicle


28



3 Control functions

1 - Filler neck sealing

2 - Max pressure control

3 - Min pressure control (vacuum valve)

Pressure cap


29



Air liquid heat exchanger (radiator) composition

• Core heat exchange

• Two tanks cooling collection & release

Heat exchange core made by stacked layers of pipes

Material (high thermal conductivity)brassaluminum

Technologymechanical expansion & interferencebrazing

1-Cooling system Component – Component – RadiatorRadiator

30



A radiator is a type of heat exchanger. It is designed to transfer heat from the hot coolant that flows through it to the air blown through it by the fan.

A typical radiator consists of a header tank, the core and the lower tank: both of these tanks have water outlets.

The water coolant mixture is cooled while it flows into the radiator’s core which is made of thin, flattened aluminum small tubes with aluminum fins outside which are present only to help increase the rate of heat transfer (secondary heat transfer surfaces). The tubes sometimes have a type of fin inserted into them called a turbulator, which increases the turbulence of the fluid flowing through the tubes.

The core is usually made of stacked layers of metal sheet, pressed to form channels and soldered or brazed together. For many years radiators were made from brass or copper cores soldered to brass headers. Modern radiators save money and weight by using plastic headers and may use aluminum cores. This construction is less easily repaired than traditional materials.




Tubes

Ailettes

DMS

DMS: 23R7 60µ av Ailett e Diabolo 12/99 ? ? effet Volume effet Volume ?

actuel prévu actuel prévu actuel prévu actuel prévu actuel prévu actuel prévu actuel prévu

Ep. tube 0,35 0,325 0,35 0,325 0,35 0,325 0,35 n/a 0,35 n/a 0,35 0,3

Ep. d'ailette 0,077 0,060 0,077 0,060 0,077 0,060 0,077 n/a 0,077 n/a 0,077 0,07

1,15

A A7072 H19

1,0 - 1,05 - 1,15

8006/8011/1230 H19

Itatiba

3003 F 3103 F

Pas d'ailettes 1,0 - 1,05 - 1,15

Site de production Laval Saragossa

1,0 - 1,05 - 1,15

1050 H19

3003 H12 3103 H18

St Luis Potosi

Matière3003 H12

Pologne

A A3003 H18

1100 H19 1050 H19

3103 H12

1100 H19

Actions de productivité

23R7

Frosinone Greensburg

1,0 - 1,15

02/2000

3003 H18

1100 H19

1,15

Tubes

Ailettes

pour l e t ube dé c-00


Ep. tube 0,38 0,33 0,38 0,33

Ep. d'ailette 0,077 0,07 0,077 0,07


Matière


Pas d'ailettes 1,0

18V14

1,0 - 0,90

1050 H191050 H19

Gre ensburg St Luis Potosi

3103 H12

Frosinone

3103 H12

Pologne Itatiba

(épo xy )

Tubes

Ailettes



Ep. tube 0,38 0,33 0,38 0,33

Ep. d'ailette 0,077 0,07 0,077 0,07


Matière


Pas d'ailettes 1,0

18V14

1,0 - 0,90

1050 H191050 H19


3103 H12

Frosinone

3103 H12

Pologne Itatiba

(épo xy )Tubes

Ailettes



Ep. tube 0,38 0,33 0,38 0,33

Ep. d'ailette 0,077 0,07 0,077 0,07


Matière


Pas d'ailettes 1,0

18V14

1,0 - 0,90

1050 H191050 H19


3103 H12

Frosinone

3103 H12

Pologne Itatiba

(épo xy )

Typical main and secondary (louvers) fins of a aluminum brass radiator

Fins of an aluminum mechanical built radiator(oval and elyptical tubes)

Twin row brazed radiator


32



Automotive cooling radiators with horizontal tanks and with vertical tanks

Tank material -PA 66 glass reinforcedTank material -PA 66 glass reinforced


33



Radiator thermal performance per surface unit depend on

Material

Construction technology

Radiator thickness

Tubes and fins passo/technology

brass

brazing

18 – 34 mm mechanical techn.18 – 40 mm brazed techn.

Manufacture patents

Air velocity (flow rate)

Coolant velocity (flow rate)

Air velocity (flow rate)

Coolant velocity (flow rate)Heat exchanged per surface area unitHeat exchanged per surface area unit

Air pressure drop

Coolant pressure drop

Air flow rate

Coolant flow rate


34



ConstructionTechnology

Radiator thickness[mm]

Heat exchangecapacity[W/dm2 °C]

Interference mech.

18 40.2

Interference mech.

32 46.4

Brazed 13 41.6

Brazed 18 46.0

Brazed 27 64.1

Brazed 40 70.8

Heat Transfer Capacity in Kalories (W) per dm2 and per °C of Heat Transfer Capacity in Kalories (W) per dm2 and per °C of temperature difference between coolant and airtemperature difference between coolant and air

( ) ( )hkJae-TrmTr

Ar

Kw

Q =


35



0

10

20

30

40

50

0 2 4 6 8 10 12 14

Varia [m/s]

Sc

am

bio

te

rmic

o s

pe

cif

ico

[W

/dm

2 °C

] Vliq 1 m/s

Vliq 1.5 m/s

Vliq 1.75 m/s

0

10

20

30

40

50

0 2 4 6 8 10 12 14

Varia [m/s]

Sc

am

bio

te

rmic

o s

pe

cif

ico

[W

/dm

2 °C

] Vliq 1 m/s

Vliq 1.5 m/s

Vliq 1.75 m/s

Specific heat transfer of an aluminum interf. mech. radiator (Alm) 580x317x18 (LxHxP)

Specific heat transfer of an aluminum brazed radiator (Alm) 580x305x18 (LxHxP)


36



Air pressure drop of some radiators

0

100

200

300

400

500

600

700

0 2 4 6 8 10 12

Varia [m/s]

P

[P

a]

rad. 580x317x18 Alm

rad. 580x322x18 Als

rad. 580x405x28 Als

0

100

200

300

400

500

600

0 0.5 1 1.5 2 2.5

Vliq [m/s]

P

[m

ba

r]

rad. 580x317x18 Alm

rad. 580x322x18 Als

rad. 580x405x28 Als

Coolant pressure drop of some radiators


37



The primary task of the fan is to generate sufficient air flow rate at low engine speed or more generally when the coolant temperature exceeds a set point.

Front-wheel drive cars have electric fans (150-600W) because the engine is usually mounted transversely, meaning the output of the engine points toward the side of the car.

The fans are controlled either with a thermostatic switch or by the engine electronic system (ECU), and they turn on when the temperature of the coolant goes above a set point, they turn back off when the temperature drops below that point.

Rear-wheel drive cars with longitudinal engines usually have engine-driven cooling fans. These fans have a thermostatically controlled viscous clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator.

1-Cooling system Component – Component – FanFan



Core face to fan distance is the distance from the fan blade face and the next cooling component inline, typically the radiator core. This distance is critical to proper airflow and to the durability to the fan. If the distance is too close the air flow will focus on only that portion of the core that is covered by the fan blades, rendering the core section covered by the center hub section of the fan useless. If the fan is too close there will also be a constant flexing of the fan blades due to the proximity of the core face and some air pressure gradient problems. For more efficient use of the whole radiator core surface, the fan is shrouded in the most severe applications.

Typical engine-driven cooling fan application for a longitudinal engine installation




el

aerst

PP

Electrical fan stationary efficiency (ca.40%)

Air flow power [W]

where:

a

Paaer a

.

mP

Electrical power absorbed by the fan [W]

Air flow rate[kg/s]

Air density [kg/m3]

Back pressure [Pa]

Electrical motor voltage [V]

Current adsorbed by electrical motor [A]

a.m

Pel = V I

V

I

DPa


40



Coooling air

Shrouded mono and twin fan


Coooling air

Up front fan

41



500W fan typical performance (380mm blade diameter)

0

50

100

150

200

250

300

350

400

0,00 0,20 0,40 0,60 0,80 1,00 1,20 1,40 1,60 1,80

Portata Aria kg/s

Pre

va

len

za [

Pa

]

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

45,0

50,0

Co

rre

nte

as

so

rbit

a d

al m

ot.

ele

ttri

co

[A

] R

en

dim

en

to [

%]

Dp ventola

Corrente mot. elettrico

Rendimento


Optimal working area

42



Engine oil lubricates and cleans moving / rotating metallic surfaces. As metallic surface rub on each other, that causes friction, thus creating heat. Heat is the enemy to motor oil. As motor oil heats up it loses its ability to lubricate and the surfaces requiring lubrication begin to wear. Continued use at elevated temperatures can result in premature engine wear and eventual failure.

Engine oil coolers are commonly used on higher performance engines, heavy duty commercial vehicles, vehicles with increased trailer towing capacity, and most high speed diesel engines. As engines become more efficient engine oil coolers will become common on most motor vehicles.

The general target is to avoid oil temperature exceeding 160-180°C in the most severe operating conditions, but generally the cooling system is design and set to keep a constant temperature around 120-130°C.

Component – Component – Oil coolerOil cooler1-Cooling system



Filter Mounted Engine Oil CoolerThis type of engine oil cooler is designed to be mounted onto the engine block with a hollow bolt and uses the engine water as cooling fluid. The oil flow is as follows: engine oil leaves engine and enters the oil cooler, circulates through the oil cooler, exits oil cooler and enters oil filter, oil is filtered and returns to engine through the hollow mounting bolt. The cold fluid comes from the radiator circuit. Optimal performance will be achieved if the cold fluid can be taken from the exit side of the radiator (cooled water/glycol).

Engine Mounted Engine Oil CoolersThis type of engine oil cooler is designed to be mounted directly onto the engine block. The oil flow is as follow: engine oil leaves the engine and enters the oil cooler, circulates through the oil cooler, exits oil cooler and re-enters the engine. The cold fluid can either be routed to the heat exchanger in 2 ways: 1) fed from the radiator circuit through flexible lines or, 2) fed directly into the heat exchanger from the engine block, eliminating the need for additional lines. Optimal performance will be achieved when the hot oil and cold fluid (glycol/water mixture) have the greatest inlet temperature difference.




Remote Mounted Engine Oil CoolerThis type of design is normally mounted remotely from the engine block. This design is well suited to applications where additional engine oil cooling is required over the original design intent of the vehicle (I.e. increased trailer tow, large engine displacements and racing applications).There are 2 types of designs and mounting strategies in this class of engine oil coolers.

Mounted directly in an air stream (most often in front of the radiators). Cooling occurs by passing hot oil through the cooler via fluid lines coming from the engine and ambient air passing through the core of the oil cooler. Liquid-to-liquid remote oil cooler. Engine oil and coolant are both fed to the oil cooler via fluid lines coming from the engine and coolant circuit respectively. This design can be mounted anywhere there is room to package under the hood. Optimal performance will be achieved when the hot oil and cold fluid (glycol/water mixture or air) have the greatest inlet temperature difference.

Most common applications for this design can be found on heavy-duty trucks, large displacement engines and racing or high speed applications.




Component – Component – Oil coolerOil cooler



0

50

100

150

200

250

300

350

400

450

500

15 20 25 30 35 40 45

Portata olio [l/min]

Pot

enza

term

ica

[W/°

C]

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

Cad

uta

di P

ress

ione

[kP

a]

Coolant Flow = 20 L/min



Oil Side Pressure Drop

Filter Mounted Engine Oil Cooler – Thermal performances80x140mm e 12 layers (oil 140 °C, coolant 82 °C)


47



Remote Mounted Engine Oil Cooler – Thermal performances200x150x30 mm (oil 100 °C, air 20°C)

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0.03 0.08 0.13 0.18 0.23Portata olio [l/s]

Po

ten

za te

rmic

a [k

W/K

]

0

50

100

150

200

250

300

350

400

Ca

du

ta d

i Pre

ssio

ne

inte

rna

[kP

a]

Portata aria - 2m/sPortata aria - 4m/sPortata aria - 6m/sPortata aria - 8m/sPortata aria - 10m/sDP olio


48



An intercooler (original UK term, sometimes aftercooler in US practice), or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged (forced induction) internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric (constant pressure) cooling. The general target is to cool the compressed air down to below 60°C at the engine intake.

aeai

aoai

- Air temperature at intercooler inlet

- Air temperature at intercooler outlet

- Temperature of the ambient cooling air

TaiTaoTae

where:

Component – Component – IntercoolerIntercooler1-Cooling system



Tai

Tao

TURBOCHARGER

ENGINE

Brick type air to air intercooler Full Face air to air intercooler




Intercooler performance characteristic (280x130x50). Charge air temperature 140°C, ambient air temperature 30°C (ETD external temperature difference = 110°C)


51



Cooling system designCooling system design

Engine protection

Reduced packaging of the radiator/fan module

Minimized system cost

ATB index

Vehicle design & aerodynamic penetration

Product competitivity

Design targets

1-Cooling system

52



In the most severe vehicle operating modes the engine outlet temperature must

not exceed

100° - 105°C for long time

110° - 115°C for limited time

V=30 Km/h1° gear9% slope with trailer equal to the vehicle weight

V=140 Km/hLongest gearMax engine power

ATB = Ta + Tboil - Tre

Low vehicle speedATB = 40°C

High vehicle speedATB = 60°C

Engine protection targets

Two severe conditions

ATB design target

Cooling system designCooling system design1-Cooling system

53



Radiator performance characteristic

Heat to be rejected at the high speed severe driving mode

with Tru calculated from the the temperature drop through the radiator by

Design target

Kr [Kw/m2·°K]

∆Tr[°K]

Qw[Kw]

ATB

The radiator frontal area can be calculated by:

In theory, being knowed:

_r

ATBΔT

2

1TK

QA

rebr

wr

aru

T_T

Cooling system designCooling system design

Cooling module design

1-Cooling system

54



Radiator size defined by the layout constraints

In real practice:

A value of air flow rate trough the radiator is estimated at the vehicle speed of the high speed ATB target

By iterative approach, type and thickness of the radiator are selected so that the Kr coefficient can satisfy the following equation:

ATBΔT

2

1TK

QA

rebr

w

r



55



Exchanged heat coefficient Kr vs air flow rate of a typical automotive cooling radiator

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Portata aria [kg/s]

Co

effi

cien

te s

cam

bio

ter

mic

o K

r [k

W/m

2 /K]

7200 kg/h

5000 kg/h

3000 kg/h



56



Through the radiator performance characteristic by Qw heat to be rejected at the low speed mode it can be defined

Fan selection and design (Low speed ATB)

The necessary air flow rate

Electrical fan is selected from a catalogue suitable for the specific layout and able to deliver the necessary air flow

rate at maximum fan efficiency


57



Rejected heat vs air flow rate for a typical radiator

10

15

20

25

30

35

40

45

50

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Portata aria [Kg/s]

Po

ten

za t

erm

ica

scam

bia

ta [

kW]

7200 Kg/h

5000 Kg/h

3000 Kg/h

Performance characterisric of a typical electric fan

0

50

100

150

200

250

300

350

400

0,00 0,20 0,40 0,60 0,80 1,00 1,20 1,40

Portata Aria [kg/s]

Pre

vale

nza

[P

a]

0,0

5,0

10,0

15,0

20,0

25,0

30,0

35,0

40,0

45,0

Co

rren

te a

sso

rbit

a d

al m

ot.

ele

ttri

co [

A]

Ren

dim

ento

[%

]

Dp ventola

Corrente mot. elettrico

Rendimento


58



Design criticities during the project development

Difficult estimation of the air flow rate through the radiator

Different power train to be installed on the same vehicle (different Qw)

Continuous evolution of the engine compartment layout during development

Optimized process for the project design development Design phase

Approximate calculationApproximate calculation

Mono-dimensionalanalysis

Mono-dimensionalanalysis

Experimental checkExperimental check

Three-dimensionalanalysis

Three-dimensionalanalysis

Design conceptDesign concept

Design developmentDesign development

Design validationDesign validation


59



Input dataInput data OutputOutput

Coolant flow rate, rejected engine and oil cooler heats, exchange heat and perssure drop radiator characteristics….engine power and torque curve, vehicle features and front end design and air permeability , total gear ratio…

CAD file: Vehicle extrenal design Cooling module installation Engine bay layout for the major

components

Coolant flow rate, rejected engine and oil cooler heats, exchange heat and perssure drop radiator characteristics….engine power and torque curve, vehicle features and front end design and air permeability , total gear ratio…

CAD file: Vehicle extrenal design Cooling module installation Engine bay layout for the major

components

Air speed distribution through the radiator surfacea rea

ATB index

Coolant temperature at the engine outlet

Air speed distribution through the radiator surfacea rea

ATB index

Coolant temperature at the engine outlet

Accurate estimation of the air speed distribution

Accurate estimation of the air speed distribution

High work load and long time

High work load and long time

AdvantagesAdvantages

DisadavantagesDisadavantages

Three-dimensional analysisThree-dimensional analysis


60



CFD analysis: examples of calculation output. Under bonnet air speed and temperature map at two different vehicle speeds


61



CFD analysis: examples of calculation output. Air speed and temperature distribution through radiator at two different vehicle speeds


62



CFD and test results comparison

ATB exp. test

1° gear at 30 km/h 9% slope with trailer A/C OFF

5° gear at140 km/h full load A/C ON

Testing data 3D simulation

Heat to be rejected

[kW]

Air T[°C]

ATB [°C]

ATB [°C]

22.5

30.1

29.7

30.7

60

75.3

101

84.8

61.2

77.1

Rad inlet temperature

102.3

87.9

Rad inlet temperature


63



Heat (Qw) rejected to the coolant

Test equipment

Engine test bench Temperature, flow meter,

engine parameters ….

Test equipment

Engine test bench Temperature, flow meter,

engine parameters ….

Prerequisites

Engine design conformity Coolant flow rates

representative of the vehicle configuration

Prerequisites

Engine design conformity Coolant flow rates

representative of the vehicle configuration

Measurement of

Coolant temperature at the engine inlet (Twe) and outlet (Twu)

Coolant flow rate (mw) Engine speed Engine torque

At ATB operating conditions

Measurement of

Coolant temperature at the engine inlet (Twe) and outlet (Twu)

Coolant flow rate (mw) Engine speed Engine torque

At ATB operating conditions

°

°Qw = Cw · mw · (Twu -Twe)

64




Heat rejected to the coolant as % of the engine power measured on the test bench (gasoline engine 1242cc 16v 80 CV, diesel engine 1910cc 8v 105 CV

65

Heat (Qw) rejected to the coolant

3000 32 533500 38 524000 45 504500 53 475000 59 48

2000 44 612250 50 522500 56 542750 59 523000 63 473250 67 483500 70 503750 74 514000 75 544250 75 57

Rilascio termico all'acqua in % della Potenza Utile

Potenza Utile [kW]

Motori Benzina

Motori Diesel

Regime motore [gg/min]




Test equipment

Chassis dynomometer inside climatic chamber

Tempertaure and pressure measure devices

Test equipment

Chassis dynomometer inside climatic chamber

Tempertaure and pressure measure devices

ATB test measurement

Procedure

When engine temperature is stabilized at the vehicle load & speed defined by ATB targets, it has to be measured the ambient and radiator inlet temperatures

Procedure

When engine temperature is stabilized at the vehicle load & speed defined by ATB targets, it has to be measured the ambient and radiator inlet temperatures

Prerequisite - Conformity of

Engine and electronic management system

Vehicle and vehicle system, particularly front end and engine bay layout

Cooling module (radiator and fan) Pressure cap

Prerequisite - Conformity of

Engine and electronic management system

Vehicle and vehicle system, particularly front end and engine bay layout

Cooling module (radiator and fan) Pressure cap

ATB = Ta + Tboil - TreATB = Ta + Tboil - Tre


66

engine vehicle integration scuola di dottorato di ricerca 2010 - road vehicle and engine engineering...

Documents

engine heat

engine cooling system

engine shaft

engine hardware

engine layout

engine management system

road vehicle

engine outlet t