Etm 08 Turbocharging
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Transcript of Etm 08 Turbocharging
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To increase the engine power
increase the size of the engine (swept volume)
increase the mass of the air/fuel charge compressedin the cylinders by using a supercharger or a turbocharger .
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Increase the Engine Size
To increase the engine size, a greater mass of air/fuel is burnt.
Higher fuel costs as more fuel is burnt.
More mechanical losses
The engine is heavier/larger as the vehicle is carrying more loadand the vehicle needs to be larger to take the engine.
At high altitudes, insufficient oxygen to burn the fuel, resultingin low power and black smoke.
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Supercharge
A supercharger increases the pressure of the air in the inletmanifold of the engine.
Greater than atmospheric pressure has a higher density i.e. moreoxygen.
Greater mass of air rushes into the cylinder to be burnt with thefuel. More power is generated at each engine speed.
But the supercharger is driven by the engine. A supercharger could increase a 200hp engine to a 275hp engine. It needs 50hp tooperate therefore only increases the engine to 225hp.
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Turbocharge
A turbocharger acts in a similar way as a supercharger.It pressurises the air at the inlet manifold.
Greater mass of air is drawn into the cylinder to be burnt with the fuel. More power is generated.
Unlike the supercharger it is not driven by the engine. It uses the wasteenergy from the exhaust gas to drive a turbine wheel that is linked to thecompressor through a shaft.
At high altitudes the turbocharger rotates faster to increase delivery of air tothe engine to compensate. So a turbocharger maintains power from theengine and produces clean emissions.
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Air Intercooler
Fitting a turbocharger and an air cooler can increase engine
power even more.
An Intercooler removes the heat of compression between the
stages of a compressor whereas an aftercooler reduces thetemperature of the air leaving the compressor.
Delivering colder air means more oxygen per cylinder (cold air has a higher density than warm air) thus more engine power.
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To conclude, the benefits of turbocharging
increased engine power output
(upto 50% increase)
improved fuel consumption (improved pressure balance
across the engine)
improved emissions
altitude compensation
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Dual entry
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Dual entry
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Variable vane unit,
note servo control
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Waste gate by-pass
A wastegate is to allow some of the exhaust to bypass theturbine when the set intake pressure is achieved
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How it works
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How it works
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Gas flow passages
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Rotor design
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Intercooler
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Transient operation: small A/R ratio (nozzle area over turbine wheeldiameter ) to get good acceleration
Large loads: compressed pressure may exceed the pressure limit.
Wastegate bypass is required.
By altering the geometry of the turbine housing as the engine accelerates,
the turbine's A/R ratio can be maintained at its optimum. (VGT )
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Structure and operating principle of VGT
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Garrett Variable Geometry TurbochargerVane mechanism
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Fixed nozzle end platesSets side vane clearance
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The integral designVane positions to ensure maximum efficiency and zero blade stall
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Efficiency vs. turbine flow
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Chubby vane design
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Position of vane in the housingSimple yet efficient design, zero vane cocking.
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Note the stepper motor and rack and pinion
mechanism
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( )
( ) kg kJ T T cwwork turbine
kg kJ T T cw
work compressor
pt
pc
/ _
/
_
43
12
=
=
Torque curve shows limits to bmep caused by;
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Torque curve shows limits to bmep caused by;allowable smoke, cylinder pressure, exhaust
temperature and turbo rev/min
b h h f
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Engine & turbocharger characteristics of a 6 cyl. 2.28 litre swirl chamber IDI diesel engine at full load
Fuel consumption map for TC & NA versions of IDI 2.38 litre
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p p
TC
NA
Power increased, fuel consumption decreased with TC
Torque & bfsc of NA &
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Torque & bfsc of NA &
boosted 1.2 litre IDI1=1.2 NA
2= 1.2, Roots blower
3= 1.2, Comprex
4=1.2, TC5= 1.6 NA
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Performance of medium speed TC after- cooled DI. (a) =V12 (b) = V8
TC after-cooled DI, fuels with differing sulphur
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TC after cooled DI, fuels with differing sulphurcontent
Two stage TC after cooled quiescent-chamber DI.
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Two stage TC after cooled quiescent chamber DI.Boost ratio = 3, 14 litre
Comparison of boost pressure between VGT and
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p pwastegate TC
Comparison of pumping loss ~ between VGT and
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wastegate turbocharger (2000rev/min at 2.0 bar
BMEP)
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Base calculations are available on the net
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Benz map
Turbocharger compressor performance map
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TC characteristic, with airflow requirements for engine
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C c a acte st c, w t a ow equ e e ts o e g esuperimposed with constant TC Speed and efficiency
lines also shown
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A very Badly matched
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compressor !!
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Torque curve shows limits to bmep caused by;allowable smoke, cylinder pressure, exhaust
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temperature and turbo rev/min
Effect of charge air cooling
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(intercooler)
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Engine TestingR q i t d fi d b l gi l ti
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Requirements defined by legislation
14,40
0,02
0,1
0,15
0,36
1,1
5 7 9
Euro 0
Euro 1
Euro 2
Euro 3
Euro Euro4/II 4/I
2,0 3,50
US2007
Year EURO PM NOx1990 0 1,1* 14,41992 1 0,36 91995 2 0,15 7
2000 3 0,10 52005 4/I 0,02 3,52008 4/II 0,02 2
2007 US 0,01 0,5
Year EURO PM NOx1990 0 1,1* 14,41992 1 0,36 91995 2 0,15 7
2000 3 0,10 52005 4/I 0,02 3,52008 4/II 0,02 2
2007 US 0,01 0,5
P a r
t i c l e
[ g
/ k W h ]
NOx [ g/kWh ]
Development of legislation for Heavy Duty Engines in EuropeDevelopment of legislation for Heavy Duty Engines in Europe