11

TurbochargingTurbocharging

22

Why turbocharging ?Why turbocharging ?

σληηηηη c

cc

L

tdqcombmtrapmeP

TRhP ××××××=

• Obtain more power from a cylinder of given size

• To increase mass of air increase intake manifold pressure and

decrease temperature

33

Cylinder pressures in naturally aspirated (1Cylinder pressures in naturally aspirated (1--22--33--44--5) 5) and turbocharged (1and turbocharged (1--22--33’’--44’’--55’’) engines) engines

44

Improvements in power: weight ratio due to Improvements in power: weight ratio due to turbochargersturbochargers

55

Why turbocharging ?Why turbocharging ?

66

Turbocharger configurationsTurbocharger configurations

Compressors:•Axial flow (very rare)•Centrifugal

• vane less diffuser• vaned diffuser

Turbines:•Radial (with or without guide vanes)•Mixed flow (with or without guide vanes)•Axial flow (guide vanes essential)

Turbine mode:•Constant pressure•Pulsed

77

TurbochargingTurbocharging

88

Turbocharger with axialTurbocharger with axial--flow turbineflow turbine

99

Variable inlet guide vanes Variable inlet guide vanes for a radial flow for a radial flow turbineturbine

The ability to vary the throat area provides good turbine/compressor matching over a much wider operating range than is possible with a fixed geometry.

1010

Ideal turbocharged limiting pressure cycleIdeal turbocharged limiting pressure cycle

Options• Turbine acts as a flow restrictor creating a constant pressure P7 in the flow duct

• Available energy = 7-8-10-11• Turbine placed very close to the exhaust valve

• available energy = 5-6-7-8

1111

Modes of turbocharging (1)Modes of turbocharging (1)•• Constant pressureConstant pressure

–– Exhaust manifold with large volumeExhaust manifold with large volume

–– Steady flow of exhaust into the turbineSteady flow of exhaust into the turbine

–– Matched for optimum efficiency at specified engine Matched for optimum efficiency at specified engine conditioncondition

–– Not responsive to sudden load changesNot responsive to sudden load changes

–– Pulse energy 5Pulse energy 5--77--13 cannot be used13 cannot be used

•• PulsedPulsed–– Not pure pulse but constant pressure + pulseNot pure pulse but constant pressure + pulse

–– High energy available at turbine inletHigh energy available at turbine inlet

–– Good turbocharger accelerationGood turbocharger acceleration

–– Good performance at low speeds and loadGood performance at low speeds and load

–– Poor turbine efficiency due to unsteady flowPoor turbine efficiency due to unsteady flow

–– Complex exhaust manifoldComplex exhaust manifold

–– Possible pressure wave reflection problemsPossible pressure wave reflection problems

1212

Modes of turbocharging (3)Modes of turbocharging (3)

1313

Modes of turbocharging (2)Modes of turbocharging (2)

1414

Efficiency definitions (1a) Efficiency definitions (1a) –– isentropic efficiencyisentropic efficiency

Compressor:Compressor:

( )( )

2 12 1

2 1 2 1

(for a perfect gas, ).sisen sC p

Cp T TW h h h C TW h h Cp T T

η−−

= = = =− −

1

21

12 2

21 1

1

1 so

1

sC

PPT PTT PT

γγ

γγ

η

−

−⎛ ⎞

−⎜ ⎟⎛ ⎞ ⎝ ⎠= =⎜ ⎟⎝ ⎠ −

1515

Efficiency definitions (1b) Efficiency definitions (1b) –– isentropic efficiencyisentropic efficiency

Turbine:Turbine:

4

3 4 31

3 44

3

1

1

Tisen s

TT T TW

W T T PP

γγ

η −

−−

= = =− ⎛ ⎞

− ⎜ ⎟⎝ ⎠

1616

Turbocharger cycle analysis (1)Turbocharger cycle analysis (1)

1

, 2 1 , 1 2, 2 1

1

Compressor work:

C ( ) CC ( ) 1a p a s a p a

C a p aC C

m T T m T pW m T Tp

γγ

η η

−⎡ ⎤− ⎛ ⎞⎢ ⎥= − = = −⎜ ⎟⎢ ⎥⎝ ⎠⎢ ⎥⎣ ⎦

& && &

1

4, 4 3 , 4 3 , 3

3

Turbine work:

C ( ) C ( ) C 1T e p e e p e s T e p epW m T T m T T m Tp

γγ

η

−⎡ ⎤⎛ ⎞⎢ ⎥= − = − = −⎜ ⎟⎢ ⎥⎝ ⎠⎢ ⎥⎣ ⎦

& & & &

1717

Turbocharger cycle analysis (2)Turbocharger cycle analysis (2)

1818

Turbocharger cycle analysis (3)Turbocharger cycle analysis (3)

1919

Turbocharger cycle analysis (4)Turbocharger cycle analysis (4)

12

12 1

1 )]11(1[ γγ

γγδβχτη

−

−−+=tur

ctccomp

rr

β = pulsating pressure correction

δ = (1 + (1/σλ))

σ = stoichiometric air to fuel ratio

λ = excess air ratio

τ = driving temperature ratio

ηtc = overall turbocharger efficiency = ηcomp* ηtur * ηm

X = ratio of specific heat

rcomp = compressor pressure ratio

rtur = turbine pressure ratio

2020

Turbocharger cycle analysis (5)Turbocharger cycle analysis (5)

1 1.5 2 2.5 3 3.5 41

1.5

2

2.5

3

3.5

4

4.5

5Relationship between charge air and turbine pressure ratio, Overall efficiency = 0.63

Com

pres

sor

pres

sure

rat

io

Turbine pressure ratio

* Iran Noahx Iran Najmo Iran Noor Test Bed Trial 75%+ Iran Noor Test Bed Trial 85%

temp.ratio = 2.15temp.ratio = 2.30temp.ratio = 2.5temp.ratio = 2.64

2121

Turbocharger cycle analysis (6)Turbocharger cycle analysis (6)

1 1.5 2 2.5 3 3.5 41

1.5

2

2.5

3

3.5

4

4.5

Com

pres

sor

pres

sure

rat

iooverall efficiency 0.60

1 1.5 2 2.5 3 3.5 41

1.5

2

2.5

3

3.5

4

4.5

Com

pres

sor

pres

sure

rat

io

Turbine pressure ratio

Relationship between charge air and turbine pressure ratio, Overall eff. = 0.60 & 0.65

* Iran Noahx Iran Najmo Iran Noor Test Bed Trial 75%+ Iran Noor Test Bed Trial 85%

overall efficiency 0.65

2222

Turbocharger cycle analysis (7)Turbocharger cycle analysis (7)

2323

Turbocharger performance (1)Turbocharger performance (1)

2424

Turbocharger cycle analysis (2)Turbocharger cycle analysis (2)

)(2)(22

)(

21

..

.

eiei

ei

CRCRmNCCmNRNTP

CCmF

+=+==

+=

πππ

)()22( '.

21

.

ibiebeei wCwCmCNRCNRmP −=+= ππ

ebe

we

we

we

fCC

CC

βμ

cot

''

−==

2.

2..

'.

)( DNmCmwCmwCmP beebeebe πμμμ ====

2.

1

1

)(

)1(

DNm

rTC comppis

πμη

γγ

−=

−

ηtc = overall turbocharger efficiency = ηcomp* ηtur * ηm

2525

InterInter--cooling (1)cooling (1)

2 3

2 1

T TT T

ε −=

−

( )3 2 11T T Tε ε= − +

1

22 1

1

11 1C

PT TP

γγ

η

−⎡ ⎤⎛ ⎞⎛ ⎞⎢ ⎥⎜ ⎟= + −⎜ ⎟⎢ ⎥⎜ ⎟⎝ ⎠⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦

( ) ( )1 1

3 2 2

1 1 1

111 1 1 1 1C C

T P PT P P

γ γγ γε

ε εη η

− −⎡ ⎤⎛ ⎞ ⎛ ⎞−⎛ ⎞ ⎛ ⎞⎢ ⎥⎜ ⎟ ⎜ ⎟= + − + − = + −⎜ ⎟ ⎜ ⎟⎢ ⎥⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠⎜ ⎟ ⎜ ⎟⎢ ⎥⎝ ⎠ ⎝ ⎠⎣ ⎦

,

( )11

3 3 31 2

1 1 3 1 1

11 1

C

P PT PP T P P

γγερ

ρ η

−−⎡ ⎤⎛ ⎞− ⎛ ⎞⎢ ⎥⎜ ⎟= = + −⎜ ⎟⎢ ⎥⎜ ⎟⎝ ⎠⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦

2626

Intercooling (2)Intercooling (2)

• Intercooler increases density of air entering engine – increases engine power.2Mass of air drawn into each cylinder a sw volm Vρ η=

2727

Advanced turbocharging conceptsAdvanced turbocharging concepts

•• Waste gate and/or blow offWaste gate and/or blow off•• Power take offPower take off•• Variable geometryVariable geometry•• Sequential turbochargingSequential turbocharging•• Two stage turbochargingTwo stage turbocharging

2828

Blow offBlow off

2929

Sequential turbochargingSequential turbocharging

3030

Two stage turbochargingTwo stage turbocharging