analysis of sequential turbocharger systems for diesel engines · analysis of sequential...

Analysis of Sequential Turbocharger Systems for Diesel EnginesRob Stalman, Vanco Smiljanowski, Uwe Späder,Ford Research & Advanced Europe

October 24th 2011, Ford Forschungszentrum Aachen GmbH, All rights reserved

Contents:

• Introduction & motivation• Comparison of Sequential Turbocharging Systems• Switching of a parallel sequential system• Summary

GT Power User Conference 2011, Rob Stalman, Ford R&A Europe

Specific Power of Passenger Car Diesel Engines in Europe.

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1930 1940 1950 1960 1970 1980 1990 2000 2010 2020

Year [-]

Spec

ific

Pow

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Introduction

Naturally AspiratedTurbochargedTurbocharged & IntercooledSequential Systems


Introduction


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-80% PM

-56% NOx -28% NOx

EU6 EU5

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NOx [mg/km]

Contents:



Sequential Boosting Systems Layout

TC1 TC2

CompressorRecirc Valve

TC1

TC2

TurbineBypass Valve

CompressorBypass Valve

TurbineShutoff Valve

wastegate


Series SequentialParallel Sequential

Sequential Boosting Systems Layout


Series SequentialParallel Sequential

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Massenstrom

Compressor 2Compressor 1Pr

essu

re ra

tio

Pres

sure

ratio

Mass flow Mass flow


Compressor Maps – Parallel Sequential

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Massenstrom

Compressor 2Compressor 1

Full load –single turbo

first operating pointparallel (twin turbo)

first operating pointparallel (twin turbo)

Pres

sure

ratio

Pres

sure

ratio

Mass flow Mass flow



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Compressor 2Compressor 1

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Full loadparallel

Full loadparallel

Pres

sure

ratio

Pres

sure

ratio

Mass flow Mass flow



Compressor Maps – Series Sequential

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Pres

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Mass flow


Single VNTSeries SequentialSeries Sequential + VNTParallel Sequential

1000 4000

Torq

ue

Engine Speed

Application with lowest weight

FTP75 & US06

Full Load Performance & Emissions Range


Comparison• Package:

– Series Sequential general has a very big TC2 which is a challenge to package.

– Parallel Sequential is more compact and flexible to package.– All are more complex to package than single VNT.

• Aftertreatment / Emissions:– Series sequential turbine side has a high thermal inertia that impacts

temperature available for the aftertreatment system..– The boosting systems in general compete for the same package space as

parts of the aftertreatment system. This can lead to unfavourable compromises.

• Transient & driveability:– Both sequential systems have better transient behaviour than single VNT – Parallel has slightly better transient behaviour.– Series Sequential is more suited to extend engine rpm range


Comparison

• Fuel economy over NEDC slightly better for parallel sequential• Longer design lead time for complex boosting systems, special care

must be taken in case of series sequential. Series Sequential usually involves a big exhaust manifold casting including one of the turbine stages, requiring design effort

• Turbine side valves are critical for both (leakage, DP, response, robustness).

• Both systems cost more than a single VNT.• Mode switching performance critical.

– Mode switch of parallel sequential discrete, serial sequential much more smooth

– Switching with EGR?


Contents:



2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

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Turbine shut-off valve

Para

met

er [%

]

Time [sec]

Closed


Parallel Sequential Switching - Valves

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

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Turbine shut-off valve Compressor bypass valve Recirculation valve

Para

met

er [%

]

Time [sec]

Closed



2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

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20

40

60

80

100Open

Turbine shut-off valve Compressor bypass valve Recirculation valve Turbine VNT position

Para

met

er [%

]

Time [sec]

Closed



2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

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20

40

60

80

100Open

Turbine shut-off valve Compressor bypass valve Recirculation valve Turbine VNT position

Dashed: measured signals

Para

met

er [%

]

Time [sec]

Closed



time [s]2.00 2.20 2.40 2.60 2.80 3.00

Torq

ue, P

ress

ure

(rel)

[%]

30

40

50

60

70

80

90

100

110

Torque Boost Pressure Pressure ds TC1 Pressure ds TC2

Sign

al [%

]

-10

10

30

50

70

90

110

VT2 VNT Position Compressor Shut Off Valve Recirculation Valve

TC s

peed

[rpm

]

0

60000

120000

180000

240000

Speed TC1 Speed TC2

time [s]2.00 2.20 2.40 2.60 2.80 3.00

Torq

ue, P

ress

ure

(rel)

[%]

30

40

50

60

70

80

90

100

110


Sign

al [%

]

-10

10

30

50

70

90

110


TC s

peed

[rpm

]

0

60000

120000

180000

240000

Speed TC1 Speed TC2

time [s]2.00 2.20 2.40 2.60 2.80 3.00

Torq

ue, P

ress

ure

(rel)

[%]

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110


Sign

al [%

]

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110


TC s

peed

[rpm

]

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120000

180000

240000

Speed TC1 Speed TC2


Parallel Sequential Switching - Measured

Switch from single turbo to biturbo, high partload, measured. Video courtesy of L. Bartsch


Parallel Sequential Switching - Measured

Contents:



• Both Parallel Sequential and Series Sequential offer the potential to increase specific power and torque, with Series Sequential more suitable for engine rpm increase.

• This increase can either be used to increase performance or allow downsizing.

• Both systems face a number of constraints: – package– cost– complexity

• High thermal inertia is a risk for series sequential• “Step-wise” switching poses a challenge for parallel sequential• Correct system choice depends entirely on the application (In-Line

or V-engine, vehicle, duty cycle etc....)

Summary


analysis of sequential turbocharger systems for diesel engines · analysis of sequential...

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