a brief introduction to turbocharger and supercharger.

1. TURBOCHARGER AND
SUPERCHARGER
Prepared by:-
HET SHAH

2. Historic background
The history of turbocharging is almost as old as that of the internal combustion
engine. As early as 1885 and 1896, Gottlieb Daimler and Rudolf Diesel
investigated increasing the power output and reducing the fuel consumption of
their engines by precompressing the combustion air. In 1925, the Swiss engineer
Alfred Büchi was the first to be successful with exhaust gas turbocharging, and
achieved a power increase of more than 40 %. This was the beginning of the
gradual introduction of turbocharging into the automotive industry.
The first turbocharger applications were limited to very large engines, e.g.
marine engines. In the automotive engine industry, turbocharging started with
truck engines. In 1938, the first turbocharged engine for trucks was built by the
"Swiss Machine Works Saurer"

3. Historic background
• The Chevrolet Corvair Monza and the Oldsmobile Jetfire were the first turbo-
powered passenger cars, and made their debut on the US market in 1962/63.
Despite maximum technical outlay, however, their poor reliability caused them to
disappear quickly from the market.
• After the first oil crisis in 1973, turbocharging became more acceptable in
commercial diesel applications. Until then, the high investment costs of
turbocharging were offset only by fuel cost savings, which were minimal.
Increasingly stringent emission regulations in the late 80's resulted in an increase
in the number of turbocharged truck engines, so that today, virtually every truck
engine is turbocharged.

4. Classification between turbocharger and supercharger
Turbochargers were originally known as turbosuperchargers when all forced
induction devices were classified as superchargers. Today the term
"supercharger" is typically applied only to mechanically driven forced induction
devices. The key difference between a turbocharger and a
conventional supercharger is that a supercharger is mechanically driven by the
engine, often through a belt connected to the crankshaft, whereas a
turbocharger is powered by a turbine driven by the engine's exhaust gas.
Compared with a mechanically driven supercharger, turbochargers tend to be
more efficient, but less responsive. Twin-charger refers to an engine with both a
supercharger and a turbocharger.
Turbochargers are commonly used on truck, car, train, aircraft, and construction
equipment engines. They are most often used with Otto cycle and Diesel
cycle internal combustion engines.

5. WHY ARE TURBOCHARGERS OR SUPERCHARGERUSED IN
AN INTERNAL COMBUSTION ENGINE??
The amount of power an internal-combustion engine can produce largely
depends upon how much fuel it can burn and how quickly and efficiently it
converts that heat to mechanical force. But fuel requires air (the oxygen
contained in air, actually) to combust, so an engine's maximum output
depends largely on how much air it can take in to burn that fuel. So we can
easily conclude that more power requires more air.
Due to this, the concept of forcing-feeding an engine with more air than it
would normally ingest, so that it can burn more fuel and produce more power.
This additional intake air can be supplied by either a turbocharger or a
supercharger. Both are air compressors, but they operate and perform very
differently. The basic difference between them is how they are driven.

6. WHY ARE TURBOCHARGERS OR SUPERCHARGERUSED IN
AN INTERNAL COMBUSTION ENGINE??
Turbochargers increase a piston engine's critical altitude, which is the maximum
altitude at which an engine can maintain its full, rated horsepower. Because the
maximum horsepower of a naturally aspirated (no turbocharged) engine is achieved in
standard, sea level conditions, sea level is the engine's critical altitude. However, since
most airports are above sea level, naturally aspirated engines—which account for the
vast majority of piston aircraft engines including those on almost all trainers—don't
produce their full, rated power on takeoff. This is why aircraft performance charts give
performance data for various pressure altitudes.
A turbocharger compresses the engine's intake air to maintain sea-level takeoff
manifold pressure and full, rated power up to the engine's critical altitude. This altitude
depends on the individual engine/turbocharger installation. But when the aircraft
climbs above its critical altitude, the manifold pressure and resulting power decrease,
just as a normally aspirated engine does when climbing away from sea level

7. Mechanical supercharging
Schematic of a
mechanically
supercharged four-
cylinder engine
With mechanical supercharging, the
combustion air is compressed by a compressor
driven directly by the engine. However, the
power output increase is partly lost due to the
parasitic losses from driving the compressor.
The power to drive a mechanical turbocharger
is up to 15 % of the engine output. Therefore,
fuel consumption is higher when compared
with a naturally aspirated engine with the
same power output.

8. Exhaust gas turbocharging
Schematic of an
exhaust gas
turbocharged four-
cylinder
In exhaust gas turbocharging, some of the exhaust gas
energy, which would normally be wasted, is used to
drive a turbine. Mounted on the same shaft as the
turbine is a compressor which draws in the combustion
air, compresses it, and then supplies it to the engine.
There is no mechanical coupling to the engine.

9. TYPES OF SUPERCHARGERS
• ROOT’S SUPERCHARGER
 It is the oldest among the other
superchargers.
 American inventors and brothers;
Philander and Francis Marion
Roots

11. ROOT’S SUPERCHARGER
MAIN PARTS:
1. Drive pulley
2. Lobes
3. Bearings
4. Gears
5. Shafts
6. casing

13. TWIN SCREW SUPERCHARGER
• It uses a pair of identical spiral
rotor in the shape of screw.
• More efficient than roots type.
• Less noisy

14. MAIN PARTS:
1. Bypass actuator
2. Housing
3. Front cover
4. Drive pulley
5. Bearings
6. Time gears
7. Rotors

15. WORKING
• Through pulley, power is transmitted to input shaft which makes the rotor
move in opposite direction.
• There is one rotor with taper teeth section and second rotor has warm gear
teeth section.
• When both side of rotor meshes together, air gets squeezed between
them.
• The air flow in auxiliary motion at inlet and transported horizontally all the
way to discharge side in radial motion.
• From discharge end it is passed to the intercooler where it’s temperature
decreases thus increase in density.

16. CENTRIFUGAL COMPRESSOR

18. CENTRIFUGAL SUPERCHARGER
Main parts:
1. Impeller
2. Diffuser
3. Driven pulley
4. Bearings
5. Gears
6. Transmission
7. Aeration pump
8. housing

19. Working
• Impeller rotates and suck high velocity and low pressure air from the
atmosphere axially.
• It compresses the air, reduces it’s velocity and provides high density air at
the outlet.
• The pressure increases and velocity decreases as the air moves from
impeller blades to the diffuser blades and then finally from casing.
• This high pressure and high density air is provided to the inlet manifold of
the engine to increase its power output.
• The impeller can rotate up to 100,000 rpm

20. Types of turbochargers
1. Single turbo
2. Sequential turbo
3. Twin-scroll turbo
4. VGT turbo
5. Electric turbo

21. Single turbo
• Simplest and most common of all.
• Because of its relative simplicity compare to all the others.
• It is the cheapest but arguably not the best.
• It can’t be effective across the whole rev. range.
• The boost range will be fairly narrow and lag will be an issue.

22. Sequential turbo
• Instead of having difficulty in selecting either small low-end turbo or big
high-end turbo; fit two, one small and one large.
• Thus small turbo gives starting torque while big one provides top end
grunt, resulting in a wide and flat torque curve.
• A flap in exhaust manifold will direct gas into second turbo.
• Due to this engine set-up is expensive, heavy and complex.

23. • The arrangement with one turbocharger being bypassed as another is
introduced, is called series sequential.
• If the first turbocharger continues to be used throughout the entire rev.
range, however, then this set-up is called parallel sequential
configuration.
Sequential arrangement

24. • Sequential turbocharging can be carried out using identically sized
turbochargers, with only one being employed until sufficient exhaust gas is
being produced to drive both properly.
• Mk4 Toyota Supra
• Parallel sequential setup, instead of large and small one.

25. Compound turbo
• The turbochargers are connected in series so the outlet of the compressor
of the first is fed into the compressor inlet of the second.
• This allows the pressure of the incoming air to be increased significantly, as
it works its way through the turbocharging ‘stages’, allowing for more
power.

26. Twin scroll turbo
• An engine’s cylinders fire in sequence, meaning that exhaust gases enter the
turbo in pulses.
• These pulses can easily overlap and interfere with one another when
powering the turbo, and a twin-scroll turbocharger solves this issue by using
a divided-inlet turbine housing and a specific exhaust manifold that pairs the
right cylinders to each scroll.
• Thus there is less pulse overlap and less lag.

27. Variable geometry turbo(VGT)
• A VGT is an expensive and complex power solution that’s especially
prevalent in diesel engines.
• A VGT has a ring of aerodynamically-shaped vanes in the turbine housing
that can alter their area-to-radius ratio to match the revolutions of the
engine.
• At low revs, area-to-radius creates more pressure and velocity to spool up
the turbo more effectively. At higher revs, the ratio increases to let in more
air.

28. Electric turbo
• Very recent development.
• The compressor provides instant boost to the engine, until the
turbocharger has spooled up enough.
• The system is expensive and complex.
• A compressor needs an motor, which in turn needs to be powered. So this
is not an simple system to implement.
• Audi’s SQ7.

29. Reducing friction through bearing design
• Traditionally- Journal and thrust bearing.
• New technology – ball bearing cartridges and oil free air bearings.
• Decrease in friction due to the usage of this new technologies.
• Decrease in friction enables the central core of turbocharger to spool up more
quickly.
• Thus increases the efficiency.
• But the only holding thing in its implementation is reliability, but this will become
less as manufacturing process is refined.

30. Improving the compressor
• To increase the pressure in each cylinder and maximize the efficiency of the
airflow, development work is focused on creating new blade configuration
and optimize compressor wheel design.
• New concepts in compression, like a combined axial and radial compressor
stage are being manufactured.
• If successful, this will be a radical shift in the way compressor function, and
has the potential to provide significant pressure increase.

31. HYBRID TURBOCHARGER FOR MARINE ENGINE
• Hybrid turbocharger is developed by Mitsubishi heavy industries and it
differs from conventional turbochargers in terms of both waste recovery
and fuel saving.
• The turbine and compressor does the heat energy recovery work and the
alternator is used to generate electrical power without consuming any
extra fuel as it is driven by the shaft power of the turbocharger.

32. Requirements for setting up hybrid
turbocharger
 For a hybrid turbocharger, three basic things required are:
1. Conventional turbocharger with extended shaft to accommodate alternator
at blower end.
2. A specially designed very compact alternator to run at very high speed of
around 9000 rpm.
3. A cooling system for alternator as heat generated will be more due to its
compact size for given rpm.

34. Construction of hybrid turbocharger
• A two part shell made form cast steel is fitted to the blower side
scroll, which is built up with higher rigidity, in order to support
alternator.
• The lower half shell is attached first and is made such that it acts like
a sump to collect lubricating oil discharged from the alternator.

35. Application:
MV Shin Koho, a 292 m
long 180,000 dwt bulk
carrier with a draft of
24.5m is the world’s first
merchant vessel to
successfully equipped with
the hybrid turbocharger
technology

38. Intake filter and silencer are mounted above the alternator assembly with
sufficient gap to allow air to pass over the shell in to the compressor blades.
Cooling water jacket made up of aluminium is provided around the rotor
winding and external cooling air is also supplied at extreme ends and centre of
the windings.
The alternator and compressor are connected by special designed flexible
coupling.
The length and weight of the Hybrid T/C is 313mm and 4600kg more as
compare to conventional system.

39. At 9500 rpm, the hybrid system can generate about 750 KW which is enough to take up full sea load of a
normal size merchant vessel.

40. Advantages
 With only little increase in the dimensions, enough power can be generated
from main engine operation.
Fuel saving as the heat recovery system is used for driving the alternator.
The generator can function as motor at low load operation to drive blower
for maintaining scavenge air pressure of the main engine.
Eliminate the installation of auxiliary blower for main engine.
As no extra fuel is used, it helps in emission cut down from ship.

41. Water-Methanol injection
In modern turbocharged vehicles, air is inducted through the intake,
through the cold side of the turbo, passes through the intercooler, and into
the intake valve port where it is mixed with fuel and combusted.
Cold Air Intake and bigger Intercooler reduce intake air temperatures,
which improves the performance.
Water meth injection further cools the intake air temperature by misting a
mixture of 50% water and 50% methanol into the intake behind the
intercooler but before the throttle body. This allows the mixture to
vaporize rather than condense.
The water-meth mixture is essentially steam as it enters the combustion
chamber, where it has two main effects: both reducing the temperature of
the intake air and producing a steam-engine effect. Both factors combine
to make a significant increase in performance.

43. Advantages of Water-Methanol injection
The addition of water as pressurized steam effectively steam-cleans
engine internals, which helps with performance as well as reliability.
With water meth injection, the lower temperatures combat
premature detonation and increase the octane rating.
And higher octane ratings are more explosive, so the whole system
effectively makes full use of all physical, thermal, and chemical
properties to increase power and reliability.

44. RAAX Turbocharger
RAAX stands for “radial-axial”
Usually all the turbochargers used now are of radial type in which they
have radial exhaust gas inlet but in this new RAAX turbocharger it has
radial-axial (semi-radial/semi-axial) inlet path.
It’s new blade design increase the angle of incidence which is 90 degree in
the case of radial turbocharger.
Due to it’s blade design a substantial reduction of approximately 40
percent in the rotational moment of inertia of the turbine wheels.
This means the turbocharger responds faster to engine load changes, so
boost pressure is developed more quickly and turbo lag is minimized.
It also results in up to 3 percent greater efficiency in the engine relevant
operating range, leading to reduced emissions

45. Difference between Radial
and RAAX turbocharger