TurboCharger and Supercharger

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WELCOME

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TURBOCHARGER AND SUPERCHARGER

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INTRODUCTION

• The power out put of an engine depends upon the
  amount of air inducted per unit time and the
  degree of utilization of this air , and the
  thermal efficiency of the engine.
• Indicated engine Power
• IPPLAnK/60000 ..(1)
• Where, IP indicated power (kW)
• Pindicated mean effective pressure(N/m2)
• Llength of stroke
• A area of piston
• n no of power stroke, for 2-s engine-N and for
  4-s engine N/2, N rpm
• K No of cylinders

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Three possible methods utilized to increase the
air consumption of an engine are as follows

• Increasing the piston displacement This
  increases the size and weight of the engine, and
  introduces additional cooling problems.
• Running the engine at higher speeds This results
  in increased mechanical friction losses and
  imposes greater inertia stresses on engine parts.
• Increasing the density of the charge This allows
  a greater mass of the charge to be inducted into
  the same volume.

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Definition

• The most efficient method of increasing the power
  of an engine is by supercharging, i.e. increasing
  the flow of air into the engine to enable more
  fuel to be burnt.
• A Supercharger is run by the mechanical drive,
  powered by engine power .
• A turbocharger uses the otherwise unused energy
  in the exhaust gases to drive a turbine directly
  connected by a co-axial shaft to a rotary
  compressor in the air intake system.

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COMPRESSED AIR
Air inlet
Fig.1 Supercharger
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Types
Fig. 2 Turbocharger
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Need of turbocharger and super charger

• For ground installations, it is used to produce a
  gain in the power out put of the engine.
• For aircraft installations, in addition to
  produce a gain in the power out put at sea-level,
  it also enables the engine to maintain a higher
  power out put as altitude is increased.

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Working principle of a turbocharger

• A turbocharger is a small radial fan pump driven
  by the energy of the exhaust gases of an engine.
• A turbocharger consists of a turbine and a
  compressor on a shared shaft.
• The turbine converts exhaust to rotational force,
  which is in turn used to drive the compressor.
• The compressor draws in ambient air and pumps it
  in to the intake manifold at increased pressure,
  resulting in a greater mass of air entering the
  cylinders on each intake stroke.

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Types of super charger

• Based on the use of compressor
• Centrifugal type
• Roots type
• Vane type

• Components of turbocharger
• Air compressor
• Turbine
• Intercooler

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Where the turbocharger is located in the car
FIG. 5
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Thermodynamic analysis of turbocharged engine
cycle
3
2
4
1
0
FIG. 6 Four-stroke cycle of an SI engine equipped
with a supercharger turbocharger, plotted on p-v
coordinates.
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Net work output Wnet work done by piston Gas
exchange work area
A area Area A
.......................(2) Area
B work done by turbocharger
..............(3) Wnet Work done
per unit of air mass. Where, p0 atmospheric
pressure, p1 pressure after compression, T0
atmospheric air temperature, V1 volume of
boosted air, rp pressure ratio, r
compression ratio, cpSpecific heat of air and ?
turbocharger efficiency,
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Selection process of turbocharger

• The concept of turbocharger is illustrated in
  Figure 7.

• Compressor air inlet,Point1- p1, T1
• Compressor air out let, point2-p2, T2
• Turbine exhaust gas inlet, point 3-p3,T3
• Turbine exhaust gas outlet-
• P4, T4

Figure7. Illustration of the concept of a
turbocharger.
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Terms essential for turbocharger selection
Air Consumption and Air-Delivery Ratio
.(4)
Where mat theoretical air consumption rate,
kg/h atm De engine displacement, L Ne
engine speed, rpm ?a density of air entering
compressor, kg/m3
The air-delivery ratio is the ratio of the
measured over the theoretical air consumption of
an engine
..(5)
where ev air-delivery ratio mat theoretical
air consumption of the engine, kg/h ma actual
air consumption of the engine, kg/h
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• A turbocharger air delivery ratio.

(5)

• The turbine pressure ratio is defined as , ?pt
  p3 / p4

.(6)

• Pressure ratio across the compressor, ?pc, as

.(7)

• The temperature ratio across the compressor

..(8)
Where ec compressor efficiency, decimal.
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• The compressor efficiency ( theoretical
  temperature rise across the compressor)/(the
  actual temperature rise). ec is always less than
  1.0.
• The turbine efficiency ( the actual temperature
  drop across the turbine )/(the theoretical
  temperature drop). The turbine efficiency is
  also always less than 1.0.

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• The following procedure may be used in selecting
  a turbocharger for an engine.
• 1. Select the desired, achievable power output,
  Pb verify that the chosen power level does not
  require an excessive pbme. Realistically, pbme
  1250 kPa is achievable.
• 2. Calculate mf Pb BSFC, using an achievable
  value for BSFC. Typically, for a well-designed
  engine, it is possible to achieve , 0.2 lt BSFC lt
  0.25 kg/kW h.
• 3. Calculate ma mf (A/F), using the desired
  A/F ratio of the turbocharged engine. For a CI
  engine running on diesel fuel, typically 25 lt
  (A/F) lt 32.
• 4. Select the compressor and the point on the
  compressor map (see Figure 8 for an example map)
  at which the compressor will operate at rated
  load and speed of the engine. Equations 3 through
  4 can be reworked into

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Performance curve
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5. Select the turbine and the operating point on
the turbine map. The turbine and compressor must
rotate at the same speed, the turbine flow must
equal the compressor flow times (1 FA), and the
turbine must supply enough power to drive the
compressor while overcoming bearing friction.
The mechanical efficiency of the turbocharger
..(9)
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Equation 10 can be reworked into
characteristic-value equations that incorporate
the speed, flow and power constraints
.(10)
.(11)
where t avaiablel characteristic value
available t required characteristic value
required u - (k' - 1)/k' et turbine
efficiency, decimal em turbocharger mechanical
efficiency, decimal Cpc constant-pressure
specific heat of ambient air, kJ/kgK Cpt
constant-pressure specific heat of heated air,
kJ/kgK The available characteristic value
depends upon the FA ratio, the turbocharger
efficiencies, and the temperature ratio across
the engine.
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Advantages of supercharger and turbocharger

• The more increase the pressure of the intake air
  above the local atmospheric pressure (boost), the
  more power the engine produces. Automotive
  superchargers for street use typically produce a
  maximum boost pressure between 0.33 to 1.0 bar ,
  providing a proportionate increase in power.
• Engines burn air and fuel at an ideal
  (stoichiometric) ratio of about 14.71, which
  means that if you burn more air, you must also
  burn more fuel.
• This is particularly useful at high altitudes
  thinner air has less oxygen, reducing power by
  around 3 per 1,000 feet above sea level, but a
  supercharger can compensate for that loss,
  pressurizing the intake charge to something close
  to sea level pressure.

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Disadvantages of turbocharger and supercharger

• Cost and complexity
• Detonation
• Parasitic losses
• Space
• Turbo lag

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Performance evaluation of the Turbo charged
Agricultural Tractor Engine
Place Agricultural Machinery Research Centre,
Massey University, Palmerston North, New Zealand
in 1990. Tractor- John Deere 3140 No of
cylinder-6 Compression ratio- 16.8 1 Fuel 10
tallow ester 90 diesel
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Experimental Setup

• Monitor exhaust temperature with (Fe/ Cn
  thermocouple and oil sump temperature with (Cu/Cn
  thermocouple).
• Before each run the engine was worked under load
  for 10-15 min to achieve normal operating
  conditions.
• Using a calibrated A W Nebraska 200 p.t.o.
  dynamometer, a series of steady state
  measurements of p.t.o. speed, torque and hence
  power was taken
• Settings an injection pressure of 210 bar and
  fuel pump calibration to provide 51 mm3 of fuel
  at rated speed and full load.
• A Campbell 21X data logger

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Experimental Conditions

• Naturally aspirated engine
• 2. Naturally aspirated servicing and
• 3. Turbocharged engine.
• In the experiment the following parameters were
  measured.
• Torque
• Power
• Exhaust gas temperature
• Turbocharger Oil Temperature.

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30
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32
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Type of Compressor.
2. Vane type
1.Centrifugal type
3. Roots type
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FIG.3
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Results and discussion

• Torque Torque-rise percentage (from torque at
  maximum power at approximately 570 rev/min at the
  p.t.o. to maximum torque, which represents the
  torque back-up, or lugging ability of the
  tractor), was 18.9 for the original naturally
  aspirated mode, rose to 21.6 after servicing,
  and reached 33 after turbocharging.
• Power Due to the increased torque after
  servicing, maximum power increased from 63.1 kW
  to 65.9 kW at 570 rev/min and remained higher
  throughout the working speed range. The
  turbocharged version produced a maximum power of
  77.1 kW
• Exhaust gas temperature
• Oil temperatures

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Conclusions

• Due to low speed of operation and less power in
  agricultural tractor, turbocharger is used not
  supercharger for more power generation and to
  operate it higher altitude.
• Turbo-charging a tractor engine is an acceptable
  method of increasing its performance if carried
  out within manufacturers specifications.
• Lower engine operating temperatures result which
  can be beneficial.
• Since the engine lubricating oil is subjected to
  high temperatures as it passes through the
  turbocharger the correct oil must be used as
  specified for turbocharged engines.

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• THANK YOU