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© by VKA – all rights reserved. Confidential – no passing on to third parties
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Institute for Combustion Engines RWTH Aachen University Prof. Dr.-Ing. Stefan Pischinger
1 Institute for Combustion Engines RWTH Aachen University 2 FEV GmbH, Aachen
Modeling of Axial Forces on Turbocharger Rotors
Frankfurt, October 26th, 2015
Max Stadermann1, Johannes Scharf2
© by VKA – all rights reserved. Confidential – no passing on to third parties
Precise consideration of TC bearing losses for TC efficiency calculation
Definition of boundary conditions for TC bearing simulations
Design of TC thrust bearings – One of the most frequent causes for TC failure
Enhanced part load simulation accuracy – Prediction of fuel consumption in driving cycles (GT-Drive) – Set point for load step simulations
BM
EP /
bar
0
4
8
12
16
20
Engine speed / 1/min1000 2000 3000 4000
1.5 l TC DI WLTP
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
Turb
ine
Effi
cien
cy η
T/
-.
Turbine Pressure Ratio p3t/p4 / - .
)hh(mP)hqh(m
stis,4,tot3,T
Ftot1,Ctot2,Vadis,T, −
+−−=
η
Isentropic adiabatic efficiency
)hh(mP)hh(m
stis,4,tot3,T
Ftot1,tot2,VisT, −
+−=
η
Isentropic efficiency
)hh(m)hh(m
*stis,4,tot3,T
tot1,tot2,VTCm,isT, −
−=
ηη
Net turbine efficiency
Do we need thrust load modeling?
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Agenda
General Behavior of TC Friction Losses
Overview of TC Thrust Load Modeling
Impact of TC Friction Losses on Engine Modeling – Full Load Operation at Rated Power Condition – Transient Response during Load Steps at Low Engine Speeds
Conclusion
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Main Influential Parameters on TC Bearing Friction Thrust Load Difficult to Predict during TC Operation
-60 -40 -20 0 20 40 60A i lk ft / N
Axial Load Fax / N
pOil = 4 bar (abs.) TOil = 90 °C nTC = 120 000 1/min
nTC = 80 000 1/min
nTC = 40 000 1/min
0
50
100
150
200
250
300
350
400
450
500
550
0 40000 80000 120000 160000
pOil = 4 bar (abs.) TOil = 90 °C FAx = 0 N
TC Speed nTC / 1/min
TC B
earin
g Fr
ictio
n P
F / W
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TC Friction Test Bench Independent Speed and Thrust Load Control
Electric Drive
Toil,out
MF
Toil,in, poil Thrust Load Actuator
Fax
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Agenda
General Behavior of TC Friction Losses
Overview of TC Thrust Load Modeling
Impact of TC Friction Losses on Engine Modeling – Full Load Operation at Rated Power Condition – Transient Response during Load Steps at Low Engine Speeds
Conclusion
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Overview of Thrust Load Modelling Model Validation using Strain Gage and Pressure Sensors
C,1mF
CS,F
CWheel,FTWheel,F
TS,F
T,4mF
Tp4,FCp1,F
2p
1p
3p
4p
BFC,p
BFT,p
Model has been calibrated using TC test bench data and works for different temperature and pressure boundary conditions
© by VKA – all rights reserved. Confidential – no passing on to third parties
Agenda
General Behavior of TC Friction Losses
Overview of TC Thrust Load Modeling
Impact of TC Friction Losses on Engine Modeling – Full Load Operation at Rated Power Condition – Transient Response during Load Steps at Low Engine Speeds
Conclusion
© by VKA – all rights reserved. Confidential – no passing on to third parties
Impact of Friction Losses on Engine Modelling Calculation of Thrust Load Based on 3-Cylinder GT-Power Model
Look-up table based on friction test bench results
20000400006000080000
100000120000140000160000180000200000220000240000260000
-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60
100100 100
300300 300
600600 600
2525 25
5050 50
150150 150
200200 200
400400 400
500500 500
700 700 700
Thrust Load Fax / N
TC S
peed
nTC
/ 1/
min
PF / W
p3 = f(° CA)
p2 = f(° CA) Thrust Load Model
Fax = f(° CA)
Input for thrust load model
p1 = f(° CA) p4 = f(° CA)
nTC = f(° CA)
TC Geometry Data Loss Coefficients
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-60
-40
-20
0
20
40
60
80
100
120
0 60 120 180 240 300 360 420 480 540 600 660 720
Thru
st L
oadi
ng F
ax/ N
Crank Angle / ° CA
Thrust Loading During an Engine Cycle (neng = 5500 1/min WOT) Maximum amplitude reaches ΔFax,max = 42 N
Thrust Load Compressor Turbine Turbine+Compressor
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-60
-40
-20
0
20
40
60
80
100
120
0 60 120 180 240 300 360 420 480 540 600 660 720
Thru
st L
oadi
ng F
ax/ N
Crank Angle / ° CA
Thrust Loading During an Engine Cycle (neng = 5500 1/min WOT) Maximum amplitude reaches ΔFax,max = 42 N
Thrust Load Compressor Turbine Turbine+Compressor
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-60
-40
-20
0
20
40
60
80
100
120
0 60 120 180 240 300 360 420 480 540 600 660 720
Thru
st L
oadi
ng F
ax/ N
Crank Angle / ° CA
Thrust Loading During an Engine Cycle (neng = 5500 1/min WOT) Maximum amplitude reaches ΔFax,max = 42 N
Thrust Load Compressor Turbine Turbine+Compressor
ΔFax,max = 42 N Sign change before and after each blow down phase
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Contribution of Friction Losses to Overall Compressor Power Friction needs to be Considered in Part Load
Engine Speed
Eng
ine
Load
0
20
40
60
80
100
Turbine Power BearingFriction
BearingFriction (Fax)
Nor
mal
ized
Pow
er /
%
5 %
0
20
40
60
80
100
Turbine Power BearingFriction
BearingFriction (Fax)
Nor
mal
ized
Pow
er /
%
66 %
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Load Step 1500 rpm 2bar to WOT Consideration of Thrust Load Leads to Slower Load Step
Normalized Time To Torque (TTT) Comment
14
. Both load steps start at the same part load point
The WG has been closed before and during the load step
Difference in response time only caused by different friction losses of the turbocharger
Load
t
0.8
0.9
1
1.1
1.2
1 2
norm
aliz
ed T
TT
PF = f(nTC) PF = f(nTC,Fax)
∼10 %
TTT
90 %
Increase TTT by 10 %
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Conclusion
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MotivationDetailed Sub-Models enable Precise Modelling of Turbochargers
Extended turbine maps
ηT
CoolantOil
Environment
Turbine housingCompressor housing Centre housing
Shaft
Compressorwheel
Turbine wheel
TC
mcp mcp mcp
mcp mcpmcp
πC
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-60 -40 -20 0 20 40 60A i lk ft / N
Axial Load Fax / N
pOil = 4 bar (abs.)TOil = 90 °CnTC = 120 000 1/min
nTC = 80 000 1/min
nTC = 40 000 1/min
40 60 80 100 120
Oil Inlet Temperature Toil / °C
pOil = 4 bar (abs.)FAx = 0 NnTC = 120 000 1/min
nTC = 80 000 1/min
nTC = 40 000 1/min
0
50
100
150
200
250
300
350
400
450
500
550
0 40000 80000 120000 160000
pOil = 4 bar (abs.)TOil = 90 °CFAx = 0 N
TC Speed nTC / 1/min
TC B
earin
g Fr
ictio
n P F
/ W
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C,1mF
CS,F
CWheel,FTWheel,F
TS,F
T,4mF
Tp4,FCp1,F
2p
1p
3p
4p
BFC,p
BFT,p
© by VKA – all rights reserved. Confidential – no passing on to third parties
© by VKA – all rights reserved. Confidential – no passing on to third parties
BMEP
/ ba
r
0
4
8
12
16
20
Engine speed / 1/min1000 2000 3000 4000
1.5 l TC DI WLTP
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
Turb
ine
Effi
cien
cy η
T/
-.
Turbine Pressure Ratio p3t/p4 / - .
Isentropic adiabatic efficiency Isentropic efficiency
Net turbine efficiency
© by VKA – all rights reserved. Confidential – no passing on to third parties
Special thanks to AiF and FVV !
Thank you for your Attention !