This report are based on other references in the website.

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FACULTY OF MECHANICAL AND MANUFACTURING ENGINEERING
AERONAUTICAL ENGINEERING TECHNOLOGY
(PROFESSIONAL PILOTING)
AMALAN KEJURUTERAAN II BDU28001
REPORT ENGINE COOLING & EXHAUST SYSTEM
Lectures:
EN. QAMARUL EZANI BIN KAMARUDIN
EN. MOHD FIKRI BIN MOHD MASROM
Group Members:
AMAL IQMAL B. ADNAN AD110189
MOHAMAD FHAIZZUDDIN B. ABD KADIR AD110030
MOHAMAD IRFAN B. AZMI AD110169
MOHAMAD FAZLE B. MOHAMMED AD110201
MUHAMMAD ZAHIN B. NORIZAN AD110210
NIK MUHAMMAD HISHAMUDDIN B. NICK HAMASHOLDIN AD110140

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TABLE OF CONTENTS
No. Topics Pages
1. Introduction 3
2. Air Cooling System 3-5
3. Liquid Cooling System 6-10
4. Straight Stack Exhaust System 10-12
5. Collector Exhaust System 13-14
6. Exhaust System with Supercharger 15-18
7. References 19

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ENGINE COOLING & EXHAUST SYSTEMS
INTRODUCTION
Engine cooling is a system that capable to transfer heat from hot region to cold
region either by conduction or convection in order to cool down the engine. There are two
types of engine cooling which are air cooled and liquid cooled. While an exhaust system is
a system usually piping used to guide reaction exhaust gases away from a controlled
combustion inside an engine or stove. The entire system conveys burnt gases from the
engine and includes one or more exhaust pipes. Depending on the overall system design,
the exhaust gas may flow through one or more of cylinder head and exhaust manifold, a
turbocharger to increase engine power, a catalytic converter to reduce air pollution, a
muffler/silencer, to reduce noise.
AIRCRAFT ENGINE COOLING SYSTEMS
AIR COOLING
Function
The burning fuel within the cylinders produces intense heat, most of which is
expelled through the exhaust system. Much of the remaining heat must be removed to
prevent the engine from overheating. So air cooled system was installed in motor vehicle to
cools down the engine.
Basic Principle
Majority of aircraft piston engine cooling is done by air. Some of them are cooled by
liquid. Air cooling is accomplished by air flowing into the engine compartment through
openings in front of the engine cowling. Baffles route this air over fins attached to the engine
cylinders, and other parts of the engine, where the air absorbs the engine heat. Expulsion of
the hot air takes place through one or more openings in the lower, aft portion of the engine
cowling. The outside air enters the engine compartment through an inlet behind the
propeller hub. Baffles direct it to the hottest parts of the engine, primarily the cylinders,
which have fins that increase the area exposed to the airflow.

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Figure 1: Aircraft air cooled system
In air cooled engine, thin metal fins project from the outer surfaces of the walls and
heads of the engine cylinders. When air flows over the fins it absorbs excess heat from the
cylinders. Fins on the cylinder head are forged or cast as part of the head. Fins on the steel
cylinder barrel are machined from the cylinder barrel forging. Deflector baffles is made from
aluminum sheet, it will fastened around the cylinders direct the flow of air to obtain the
maximum cooling effects.
Figure 2: Cylinder with baffles for cooling.

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The air cooling system is less effective during ground operations, takeoffs, go-
around, and other periods of high-power, low-airspeed operation. Conversely, high-speed
descents provide excess air and can shock cool the engine, subjecting it to abrupt
temperature fluctuations.
Operating the engine at higher than its designed temperature can cause loss of
power, excessive oil consumption, and detonation. It will also lead to serious permanent
damage, such as scoring the cylinder walls, damaging the pistons and rings, and burning
and warping the valves. Monitoring the flight deck engine temperature instruments will aid in
avoiding high operating temperature.
Engine operating temperature can be controlled by the movable cowl flaps located
on the engine cowling. Cowl flaps are hinged covers that fit over the opening through which
the hot air is expelled. If the engine temperature is low, the cowl flaps can be closed, so that
it will increase engine temperature. If the engine temperature is high, the cowl flaps can be
open to permit a greater flow of air through the system, so that it will decrease the engine
temperature. But under normal operating conditions in aircraft not equipped with cowl flaps,
the engine temperature can be controlled by changing the airspeed or the power output of
the engine. High engine temperatures can be decreased by increasing the airspeed and/or
reducing the power. The oil temperature gauge gives an indirect and delayed indication of
rising engine temperature, but can be used for determining engine temperature if this is the
only means available.
Advantages and disadvantages
1. Advantage
i. Less expensive compare to liquid cooled system.
ii. More light-weight.
iii. More environment-friendly.
2. Disadvantage
i. Uneven and unreliable cooling based on airflow.
ii. Air-cooled engine that fail generally require a major overhaul.
iii. Their maintenance and repair tasks tend to be more frequent and more time-
consuming.

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LIQUID COOLING
There are few aircraft currently fitted with liquid-cooled engines, but liquid cooling is
used extensively in cars. In liquid-cooled engines, the cylinders and cylinder head are
double walled, or and a liquid is circulated through the jackets. Preventing overheating is
one function of the cooling system. It also helps the engine reach its best operating
temperature as soon as possible. Every engine has a temperature at which it operates best.
Below this temperature, ignition and combustion can be difficult. Most engine wear occurs
during this warm-up period and most pollution too.
The basic coolant use for liquid cooling system is water, but because of the lower
temperatures at altitude, the addition of an anti-freeze agent is essential with aero engines
and a mixture of 70% water and 30% ethylene glycol is normally used. The industry term for
the antifreeze mixture is engine coolant. Some antifreezes use no water at all, instead using
a liquid with different properties, such as propylene glycol or a combination of propylene
glycol and ethylene glycol. Most "air-cooled" engines use some liquid oil cooling, to maintain
acceptable temperatures for both critical engine parts and the oil itself. Most "liquid-cooled"
engines use some air cooling, with the intake stroke of air cooling the combustion chamber.
An exception is Wankel engines, where some parts of the combustion chamber are never
cooled by intake, requiring extra effort for successful operation.
Working principle
In this very basic liquid-cooling system, a coolant is stored in a radiator, and in the
engine. As the engine heats up, a natural circulation starts, as coolant rises through the
engine block by convection. It passes through the top hose, and into the radiator. Inside the
radiator, heat is removed from the coolant as it falls from the top to the bottom. When it

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reaches the bottom, it returns to the engine through the lower radiator hose. This process is
called thermo-siphon. It was common in older cars which had low-powered engines and
high, narrow radiators. In modern cars, the engines are more powerful, and radiators are
low and wide, and a there siphon process couldn’t move the coolant quickly enough.
Instead, a water pump forces it through passages called water jackets in the engine block. It
collects heat by conduction, and becomes hot itself. Heated coolant then returns to the
radiator for cooling. And the cycle is repeated. Heat is removed from the engine, and
dispersed.
One function of the thermostat is to shorten the warming-up period. It operates
according to coolant temperature. When coolant is cold, it is closed. When a cold engine
starts, coolant circulates within the engine block and cylinder head and through a coolant
bypass to the water pump inlet. It can’t get to the radiator. As the engine warms up, the
coolant trapped in the engine gets hotter and hotter. This starts to open the thermostat,
allowing hot coolant to flow to the radiator.
Components of liquid cooling systems
1. Radiator
It mainly consists of an upper tank and lower tank and between them is a core.
The upper tank is connected to the water outlets from the engines jackets by a hose
pipe and the lover tank is connect to the jacket inlet through water pump by means
of hose pipes. There are 2-types of cores:
i. Tubular
ii. Cellular as shown.

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When the water is flowing down through the radiator core, it is cooled partially
by the fan which blows air and partially by the air flow developed by the forward
motion of the vehicle. As shown through water passages and air passages, wafer
and air will be flowing for cooling purpose. It is to be noted that radiators are
generally made out of copper and brass and their joints are made by soldering.
2. Thermostat Valve
It is a valve which prevents flow of water from the engine to radiator, so that
engine readily reaches to its maximum efficient operating temperature. After attaining
maximum efficient operating temperature, it automatically begins functioning. Generally,
it prevents the water below 70°C.
When the temperature of water increases, the liquid alcohol evaporates and the
bellow expands and in turn opens the butterfly valve, and allows hot water to the
radiator, where it is cooled.

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3. Water Pump
It is used to pump the circulating water. Impeller type pump will be mounted at
the front end. Pump consists of an impeller mounted on a shaft and enclosed in the
pump casing. The pump casing has inlet and outlet openings. The pump is driven by
means of engine output shaft only through belts. When it is driven water will be pumped.
4. Water Jackets
Cooling water jackets are provided around the cylinder, cylinder head, valve
seats and any hot parts which are to be cooled. Heat generated in the engine cylinder,
conducted through the cylinder walls to the jackets. The water flowing through the
jackets absorbs this heat and gets hot. This hot water will then be cooled in the radiator.

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5. Fan
It is driven by the engine output shaft through same belt that drives the pump. It
is provided behind the radiator and it blows air over the radiator for cooling purpose.
Advantages and disadvantages
3. Advantages
i. Uniform cooling of cylinder, cylinder head and valves.
ii. Specific fuel consumption of engine improves by using water cooling system.
iii. If we employ water cooling system, then engine need not be provided at the
front end of moving vehicle.
iv. Engine is less noisy as compared with air cooled engines, as it has water for
damping noise.
4. Disadvantages
i. It depends upon the supply of water.
ii. The water pump which circulates water absorbs considerable power.
iii. If the water cooling system fails then it will result in severe damage of engine.
iv. The water cooling system is costlier as it has more number of parts. Also it
requires more maintenance and care for its parts.
AIRCRAFT EXHAUST SYSTEMS
Engine exhaust systems vent the burned combustion gases overboard, provide heat
for the cabin, and defrost the windscreen. An exhaust system has exhaust piping attached
to the cylinders, as well as a muffler and a muffler shroud. The exhaust gases are pushed
out of the cylinder through the exhaust valve and then through the exhaust pipe system to
the atmosphere.
For cabin heat, outside air is drawn into the air inlet and is ducted through a shroud
around the muffler. The muffler is heated by the exiting exhaust gases and, in turn, heats
the air around the muffler. This heated air is then ducted to the cabin for heat and defrosts
applications. The heat and defrost are controlled in the cockpit, and can be adjusted to the

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desired level.
Exhaust gases contain large amounts of carbon monoxide, which is odorless and
colorless. Carbon monoxide is deadly, and its presence is virtually impossible to detect. The
exhaust system must be in good condition and free of cracks.
Some exhaust systems have an exhaust gas temperature probe. This probe
transmits the exhaust gas temperature (EGT) to an instrument in the cockpit.
The EGT gauge measures the temperature of the gases at the exhaust manifold.
This temperature varies with the ratio of fuel to air entering the cylinders and can be used
as a basis for regulating the fuel/air mixture. The EGT gauge is highly accurate in indicating
the correct mixture setting. When using the EGT to aid in leaning the fuel/air mixture, fuel
consumption can be reduced.
For specific procedures, refer to the manufacturer's recommendations for leaning the
mixture.
STRAIGHT TYPE EXHAUST SYSTEM
Straight exhaust system is means that straight pipe direct connected to the engine
and that is why it is called as straight exhaust system. It is also can be defined as the
exhaust runs straight from the engine to out from under the car without any muffler or
catalytic converter.
STACK TYPE EXHAUST SYSTEM
Stack type exhaust system is defined as a pipe projecting from an aircraft engine
and serving as an outlet for exhaust gases. In other words, short pipes that carry the
exhaust gases from the cylinder into the surrounding air and it is also be called exhaust
pipe. While short stack means the exhaust system of an aircraft reciprocating engine made
of short pipes that direct the exhaust gases from each individual cylinder of the engine away
from the aircraft. Vintage aircraft sometimes have these short stacks on each side of the
engine as 'exhaust'. They do are easy to maintain and inspect, have no back pressure and
keep the exhaust valves cool. But a major drawback is that they are not really quiet. This is
nowadays not the way to go for everyday use aircraft. Besides, it is generally used on non-

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supercharged engines and low powered engines where noise level is not too objectionable.
Moreover, the short stack system is relatively simple, and its removing and installation the
hold-down nuts and clamps.

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COLLECTOR EXHAUST SYSTEM
In automotive engineering, an exhaust manifold collects the exhaust gases from
multiple cylinders into one pipe. Exhaust manifolds are generally simple cast iron or
stainless steel units which collect engine exhaust from multiple cylinders and deliver it to the
exhaust pipe. These consist of individual exhaust head-pipes for each cylinder, which then
usually converge into one tube called a collector. The most common types of aftermarket
headers are made of mild steel or stainless steel tubing for the primary tubes along with flat
flanges and possibly a larger diameter collector made of a similar material as the primaries.
They may be coated with a ceramic-type finish (sometimes both inside and outside), or
painted with a heat-resistant finish, or bare. Chrome plated headers are available but they
will tend to blue after use. Polished stainless steel will also color (usually a yellow tint), but
less than chrome in most cases. Another form of modification used is to insulate a standard
or aftermarket manifold. This decreases the amount of heat given off into the engine bay,
therefore reducing the intake manifold temperature. There are a few types of thermal
insulation but three are particularly common:
i. Ceramic paint is sprayed or brushed onto the manifold and then cured in an
oven. These are usually thin, so have little insulator properties however
reduce engine bay heating by lessening the heat output via radiation.
ii. A ceramic mixture is bonded to the manifold via thermal spraying to give a
tough ceramic coating with very good thermal insulation. This is often used on
performance production cars and track-only racers.
iii. Exhaust wrap is wrapped completely around the manifold. Although this is
cheap and fairly simple, it can lead to premature degradation of the manifold.
The goal of performance exhaust headers is mainly to decrease flow resistance (back
pressure), and to increase the volumetric efficiency of an engine, resulting in a gain in
power output. The processes occurring can be explained by the gas laws, specifically the
ideal gas law and the combined gas law.

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Diamond DA-40 exhausts collector system
Cessna exhausts collector system

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EXHAUST SYSTEM WITH SUPERCHARGER
Firstly, supercharger is an air compressor used for forced induction (the process of
delivering compressed air to the intake of an internal combustion engine) of an internal
combustion engine. A forced induction engine uses a gas compressor to increase the
pressure, temperature and density of the air. Superchargers have almost no lag time to
build pressure because the compressor is always spinning proportionally to the engine
speed.
If you can shove more fuel-air mixture into the cylinder of a piston engine, you will
produce more power and thrust. You need compressed air to keep maximum engine
performance at higher altitudes because the density of air decreases with altitude. Air
density decreases because, as you fly away from the earth, there is less air to pile on top of
the air below it. A supercharger compresses the air back to sea-level-equivalent pressures,
or even much higher, in order to make the engine produce just as much power at cruise
altitude as it does at sea level. With the reduced aerodynamic drag at high altitude and the
engine still producing rated power, a supercharged airplane can fly much faster at altitude
than a naturally aspirated one.
The Impeller in a supercharger's compressor is like the impeller in a hair dryer. Stationary
vanes are added outside the impeller to make the compressor work better.

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Since the size of the supercharger is chosen to produce a given amount of pressure
at high altitude, the supercharger is over-sized for low altitude. The pilot must be careful
with the throttle and watch the manifold pressure gauge to avoid over boosting at low
altitude. As the aircraft climbs and the air density drops, the pilot must continuously open
the throttle in small increments to maintain full power. The altitude at which the throttle
reaches full open and the engine is still producing full rated power is known as the critical
altitude. Above the critical altitude, engine power output will start to drop as the aircraft
continues to climb.
There are at least two different ways to drive the compressor. First is by gear it
directly to the engine’s crankshaft, and second is by letting the gasses that come out the
exhaust pipe spin a fan or turbine that in turn, spins the compressor. For this report, we will
explain on exhaust system with supercharger only. It is called turbo-supercharging. Exhaust
gases coming out of the engines cylinders are sent through a turbine. The turbine’s shaft
then will turns the compressor.
Turbo-supercharging system layout
Turbo-supercharging produces good boost at altitude, the turbine spins faster at
higher altitudes because there is less air pressure restricting the flow out of the exhaust
pipe. Even if there was no natural tendency for the turbine to spin faster, its speed can be
regulated by changing the amount of exhaust that is routed to the turbine.

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Besides altitude performance, a big advantage of turbo-supercharging is that it can
be added externally to existing engine designs. Many modern automotive applications use
turbo-supercharging for boost, just because of this add-on convenience, even though a
geared supercharger would be better in automotive applications. One problem with
Superchargers is that because they spin at such a high rate of speed, they also produce a
lot of heat. Some company’s overcame this obstacle by tapping into the vehicles oil pan to
lubricate the gears inside the head unit of the Supercharger to minimize heat and friction.
Others use internal belts or self-contained head units where the oil never needs to be
changed.
The air itself also becomes hot because you are condensing it. Intercoolers are often
used to cool the air and create a more densely packed air charge. An intercooler is much
like a cars radiator. Two common types of intercoolers are Air-To-Air, which uses outside air
to cool the air that just passed through the Supercharger, and Air-To-Water, which forces
the air through a heat exchanger that is cooled by water. Intercooler are not always needed,
but are usually found on applications that produce higher levels of boost.
You can see the turbo supercharger at the left of the picture is added onto an existing engine. On
the other side of the compressor is the turbine, which is spun by hot exhaust gases.

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Another term you will commonly hear among Supercharger conversations is the
Bypass Valve. When a Supercharger is trying to force air into the engine, but the throttle
shaft is closed, a situation called Compressor Surge is created. This can occur during
deceleration or when the driver is between gears. When the Supercharger is trying to force
the air into a closed throttle body, and the pressure inside the throttle body is greater than
the pressure created by the Supercharger, the air tries to force itself backwards into the
compressor. When this happens, the pressure inside the throttle body is released and the
compressor forces the air back through the Supercharger and then back into the throttle
body again, creating a loop. This is where a Bypass valve comes into play. It’s actuated by
the vacuum from the intake, and then releases the excess pressure either into the
atmosphere (blow off valve) or back through the compressor.
Position of the turbocharger (supercharger driven by exhaust gas)

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REFERENCES
1. Powerplant.pdf
2. www.enginehistory.org/Convention/2005/.../Cooling.pdf
3. http://en.wikipedia.org/wiki/Engine_cooling
4. Reciprocating Machinery Dynamics, Abdulla S. Rangwala, New Age
International, 2006.
5. Pilot’s Handbook of Aeronautical Knowledge, Federal Aviation Administration
(FAA) 2009.
6. www.littleflyers.com/enycool.htm
7. Aviation Maintenance Technician’s Handbook,(FAA) 2008