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Technische Universität Berlin FG Verbrennungskraftmaschinen
Turbochargers at the edge of a new generation – a discussion of potentials and limits Prof. Dr.-Ing. Roland Baar
Honolulu, 11.04.2016
2 FG Verbrennungskraftmaschinen
Fuel consumption potentials in a passenger car
example: Diesel car 1.700 kg, Euro6 potential 20% fuel consumption
start-stop and recuperation
downspeeding downsizing
turbocharger- optimizaition
reduction of friction
thermo mana gement
1% 1% 1%
5%
2%
10%
(Quelle: Bosch 2010)
vehicle ! weight ! aerodynamics ! wheel friction powertrain ! gear ! start-Stop ! hybrid engine ! downsizing ! thermodynamics ! friction ! ancillary unit energy management
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
3 FG Verbrennungskraftmaschinen
Boosting technologies DWL Druckwellenlader / Comprex K Kompressor / Compressor V Strömungsverdichter / Turbo compressor T Turbine / Turbine
K
LLK
M
c) Compressor
V T
LLK
M
d) Turbocharger a) Natural
VOL
SR
M
LLK
M
b) Comprex
DWL
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
4 FG Verbrennungskraftmaschinen
Engine comparison Pass.car Otto Pass.car Diesel Truck Diesel
17,6
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
5 FG Verbrennungskraftmaschinen
Engine comparison - Specific fuel consuption [g/kWh]
Pass.car Otto Pass.car Diesel Truck Diesel
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
6 FG Verbrennungskraftmaschinen
Engine comparison - Lambda [-]
Pass.car Otto Pass.car Diesel Truck Diesel
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
7 FG Verbrennungskraftmaschinen
Engine comparison – boost pressure p2/p1 [-]
Pass.car Otto Pass.car Diesel Truck Diesel
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
8 FG Verbrennungskraftmaschinen
Engine comparison – exhaust temperature T3 [°C]
Pass.car Otto Pass.car Diesel Truck Diesel
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
9 FG Verbrennungskraftmaschinen
a) Passenger car (Gasoline) b) Commercial vehicle (Diesel)
redu
zier
ter T
urbi
nenm
asse
n-st
rom
[kg*
K^0
,5/(s
*bar
)]
0.00.20.40.60.81.01.21.41.61.82.0
totales Turbinendruckverh‰ltnis [-]1.0 1.5 2.0 2.5 3.0 redu
zier
ter T
urbi
nenm
asse
n-
stro
m [k
g*K
^0,5
/(s*b
ar)]
1.01.21.41.61.82.02.22.42.62.83.0
totales Turbinendruckverh‰ltnis [-]1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Totales Turbinendruckverhältnis [-] Totales Turbinendruckverhältnis [-]
WG controll
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
10 FG Verbrennungskraftmaschinen
Turbocharger, HP- & LP-EGR
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
12 Fachgebiet Verbrennungskraftmaschinen
HP- & LP-EGR
Que
lle: I
AV, H
TT
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
13 Fachgebiet Verbrennungskraftmaschinen
MK
Z [
kg/s
• K
0.5 /
bar]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
∏ T,tot/st [-]1 2 3 4
∏ C
,tot
[-]
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
m• C,red [kg/s]0.0 0.1 0.2 0.3 0.4
0.74
Effects of downsizing – map width compressor of basic engine - reference
R6 6,6l – 220 kW- basic singelstage / wastegate / pulse pressure charging GT-Power simulation
Source: Baar (Voith), IQPC 2011, Downsizing & Turbocharging Concepts
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
14 Fachgebiet Verbrennungskraftmaschinen
∏ C
,tot
[-]
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
m• C,red [kg/s]0.0 0.1 0.2 0.3 0.4
0.74
MK
Z [
kg/s
• K
0.5 /
bar]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
∏ T,tot/st [-]1 2 3 4
Effects of downsizing – map width compressor of downsized engine
R4 4,5l – 220kW singelstage / VTG („large�) / constant pressure charging - simulation critical surge and speed limit
Source: Baar (Voith), IQPC 2011, Downsizing & Turbocharging Concepts
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
15 Fachgebiet Verbrennungskraftmaschinen
Low Pressure Turbine
High Pressure Turbine
MK
Z [
kg/s
• K
0.5 /
bar]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
∏ T,tot/st [-]1 2 3 4
∏ C
,tot
[-]
1.0
1.5
2.0
2.5
3.0
3.5
4.0
m• C,red [kg/s]0.0 0.1 0.2 0.3 0.4
0.770.73
Low Pressure Compressor
High Pressure Compressor
Effects of downsizing – map width compressor downsized engine
R4 4,5l – 220kW twostage / 1 wastegate / constant pressure charging – simulation reduced load
Source: Baar (Voith), IQPC 2011, Downsizing & Turbocharging Concepts
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
twostage
16 FG Verbrennungskraftmaschinen
Specific load
fuel: 269 kW
engine out: 100kW 37%
ambient heat: 92kW 34%
turbine: 16kW 6%
rest exhaust: 61kW 23%
Pcompressor
Pengine
1
7
14 kW
100 kW = =
nTC
nengine
45
1
180000 min-1
4000 min-1 = =
mTC
mengine
1
21
8 kg
170 kg = =
Power/mass-ratio: engine: 0,59 kW/kg TC: 1,75 kW/kg
x 3
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
17 FG Verbrennungskraftmaschinen
Specific load
Que
lle: I
CS
I
turbine power 25000 W
tip speed 580 m/s = 2088 km/h
Centrifugal force at turbine blade appr. 19000 N
Molecular residence time < 2ms
~130 mm
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
18 FG Verbrennungskraftmaschinen
Market development
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
19 FG Verbrennungskraftmaschinen
! exploded market
! increased number of suppliers
! maximum number of variants due to power an package demands
! high specific load
! difference in applications
! meaning for engine themodynamics
! quality demands
world market
0"
10"
20"
30"
40"
50"
60"
70"
1940" 1960" 1980" 2000" 2020"
0,01"
0,1"
1"
10"
100"
1940" 1960" 1980" 2000" 2020"
Ein
heite
n [M
io. T
C/ a
]
Market development
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
20 FG Verbrennungskraftmaschinen
1989 Start TDI
2000 10 Mio / a wolrd production
1999 Inhouse VW (til 2004) J/V Daimler IHI (til2013)
2005 Start Bosch, Mahle, Continental
2002 Competence team BMW
1998 Competence team Daimler
2011 Competence team VW
2012 SOP BoschMahle, Continental
Competence development
1982 Inhouse Toyota (70%)
1978 1. Diesel-car with TC (Mercedes 300 SD)
196x 1. Otto-car with TC (USA)
bis 2000 Market dominance Garrett (HTT), KKK (BWTS)
ab 2000 Intensification IHI, MHI
OE
M-a
ctiv
ities
TIE
R1-
activ
ities
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
21 FG Verbrennungskraftmaschinen
Market development Market share 2007 world 17 Mio.
HTT: Honeywell Turbo Technology BWTS: BorgWarner Turbosystems ICSI: IHI Chargingsystems International MHI Mitsibishi Heavy Industries CTT: Cummins Turbo Technologies BMTS:Bosch Mahle TurboSystems Continental
HTT"36%"
BWTS"32%"
MHI"13%"
ICSI"10%"
CTT"7%"
HTT""30%"
BWTS""24%"
MHI""14%"
ICSI"12%"
CTT""7%"
BMTS"5%"
Con89nental"4%"
Sons8ge"4%"
Market share2015 world 50 Mio.
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
22 Department of Internal Combustion Engines 22 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Comparison of advanced technologies
23 FG Verbrennungskraftmaschinen
Solutions Turbocharger technologies
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
0
200
400
600
800
1000
1200
0 500 1000 1500
GMR235 713C MAR247 Titanaluminid
redu
zier
ter T
urbi
nenm
asse
n-st
rom
[kg*
K^0
,5/(s
*bar
)]
0.00.20.40.60.81.01.21.41.61.82.0
totales Turbinendruckverh‰ltnis [-]1.0 1.5 2.0 2.5 3.0 re
duzi
erte
r Tur
bine
nmas
sen-
st
rom
[kg*
K^0
,5/(s
*bar
)]
1.01.21.41.61.82.02.22.42.62.83.0
totales Turbinendruckverh‰ltnis [-]1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
V T
V T
Turbolader (Hochdruck-
stufe) mit Regelklappe
Turbolader (Niederdruck-
stufe)
Ball bearing Titanium-Aluminide
Mixedflow- axial-turbine
E-Turbo WG
twostage VTG
sour
ces:
Dai
mle
r, H
TT, V
aleo
Mass production Specific applications Future potential
Efficiency and transient response
24 FG Verbrennungskraftmaschinen
Transient response Different measure
measures to improve transient response with similar effectiveness ! different level of availability ! other effects (efficiency) ! unclear interaction
electric ball titanium- axial booster bearing aluminide TW TW –
0
200
400
600
800
1000
1200
0 500 1000 1500
GMR235 713C MAR247 Titanaluminid
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Advanced development tools needed ! Heat transfer (turbocharger) ! Friction losses (turbocharger)
! Cycle simulation (engine process) ! Energy management (engine process)
25 FG Verbrennungskraftmaschinen
Electrically assisted turbocharger
Characteristics • integrated motor-generator • external power electronics • cooling with oil and/or
water • eventually cooling with
compressor air
pros and cons + transient boost + package (only small
increase of turbo size) + cold start emissions + energy recovery - 2-3 kW electric power - temperature sensible - surge of compressor - only transient operation
V T
LLK
M
E-Motor
source: ICSI
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
26 FG Verbrennungskraftmaschinen
Electric booster plus turbocharger
V T
LLK B
ypas
s
E-Motor
V
source: Valeo
Characteristics • separate component • two compressors in series • integrated power
electronics • cooling with oil and/or
water • turbocharger without
change
pros and cons + transient boost + package (freedom of
placement) + cold start emissions + energy recovery - 2-3 kW electric power - temperature sensible - additional bypass - only transient operation
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
27 FG Verbrennungskraftmaschinen
Electric booster Transient response
2.0l 110kW Diesel engine EU5 load step at 1250 1/min GT-Power-simulation Phase I ! torque increase similar to
naturally aspirated engine
Phase II ! influence of boosting
with / without electric booster in series setup
! time improvement to Mmax: 1,5 s
! influence reduced with increasing speed
1,0
1,2
1,4
1,6
1,8
2,0
2,2
2,4
2,6
2,8
3,0
0
50
100
150
200
250
300
0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 9,0 10,0
Lade
druc
k [b
ar]
Dre
hmom
ent [
Nm
]
Zeit [s]
I II !
troque
boost pressure
Electric booster
off on
1,4s
torq
ue
boos
t pre
ssur
e
time Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
28 FG Verbrennungskraftmaschinen
Electric booster Component testing
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Impe
ller s
peed
[rpm
]
0
20000
40000
60000
80000
100000
time [s]0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00
Current supply [A] Impeller speed [rpm] compressor pressure ratio [-]
nstart= 10.000 min-1
nend= 67.000 min-1
Πstart= 1.0Πend= 1.2
Current supply [A] Impeller speed [rpm] compressor pressure ratio [-]
nend= 80.000 min-1
Πend= 1.3
Current supplystart= 0,977 A Cur
rent
sup
ply
[A]
0
50
100
150
200
250
0.30 0.5
1.2
1.3
29 FG Verbrennungskraftmaschinen
Electric booster Potential assessment
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
! Development since 15 years, still no mass product, announced SOP at AUDI in 2016
! Competence mainly electrics / electronics ! Problem of availability of electric energy ! Voltage drop may be risks for ECU supply ! CO2 effect combined only in strong downsizing /
downspeeding concepts for transient compensation
! Very diverse opinions about mass production ! Will probably remain niche product (e.g. high specific engine
power)
30 FG Verbrennungskraftmaschinen
Ballbearing
Materials: ! High temperatur resistent, coated
steel ! Ceramic (balls)
Sou
rce:
Dai
mle
r
! First SOP at Daimler in 2010 6-Cylinder Diesel engine
! SOP at BMW in 2014 ! Audi rejected SOP after 2
postponements in 2011
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
31 FG Verbrennungskraftmaschinen 31
Motivation – less friction losses – better efficiency – better transient response
Challenges ! max speed ! durability ! acoustics (especially in cold
conditions)
Potentials (as of TC supplier) ! TC efficiency: +5% ! time to 90% torque: 60% ! boost pressure at 1500 rpm:
+130mbar
Source: BMTS
Ballbearing
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
32 FG Verbrennungskraftmaschinen
Ballbearing Potential for transient response
Sou
rce:
Hon
eyw
ell /
IAV
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
33 FG Verbrennungskraftmaschinen
full floating bearing ball bearing
-10�C
+80�C
engine test bench idle to full load variation of oil temp. frequency analysis of vibration signal
Ballbearing
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
34 FG Verbrennungskraftmaschinen
Ballbearing Potential assessment
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
! Development since more 25 years, first series applications in passenger cars
! Different problems, mainly acoustics and costs ! Few suppliers ! Potential for CO2 reduction and transient response in all
turbochargers if successfully realized
35 FG Verbrennungskraftmaschinen
VTG in gasoline applications
Porsche 911 Turbo 3,6l 353 kW 620/(680) Nm (Boxer-engine)
0 1000 2000 3000 4000 5000 6000 7000
400
500
600
700
200
250
300
350
torq
ue [N
m]
pow
er [k
W]
speed [1/min]
Overboost
Chalenges ! Exhaust temperature ! Costs
sour
ce; P
orsc
he
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
36 FG Verbrennungskraftmaschinen
VTG in gasoline engines Potential assessment
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
! Development since more 25 years, first series applications in passenger cars
! Effects on controllability, accuracy, lambda control, ... ! Different problems, mainly durability, reliability and costs ! Chance through water cooling (instead of fuel enrichment) ! Potential for CO2 reduction, emissions reduction and
transient response in all turbochargers if successfully realized
37 FG Verbrennungskraftmaschinen
Titanaluminid for the turbine wheel
0
200
400
600
800
1000
1200
0 500 1000 1500
GMR235 713C MAR247 Titanaluminid
tens
ile s
treng
th R
m in
MP
a
temperatur in °C
Potential ! lower inertia ! eventually higher may
speed Challenges • industrial availably • raw material price • material specific design • unknown LCF und HCF • welding of shaft an wheel • machining
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
38 FG Verbrennungskraftmaschinen
Titanaluminid for the turbine wheel Potential assessment
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
! New alloy, first series applications in gasturbines and passenger cars; recent failure in passenger car mass production
! Effects on inertia ! Unclear long-term behaviour (e.g. oxidation) ! Different problems, mainly machining, welding and costs ! Potential for transient response only
39 FG Verbrennungskraftmaschinen
Axial turbine
Potential ! better matching with
compressor (efficiency) ! lower interia (transient
respone) Challenges • reduced turbine power • thrust load on bearing
increased • little advantage (see above) • more complex casting • VTG more complex
Radial turbine Mixed flow turbine Axial turbine
sour
ce; H
oney
wel
l
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
40 FG Verbrennungskraftmaschinen
Axial turbine Potential assessment
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
! State of the art technology in gasturbines ! Effects on inertia ! Different problems, little advantage ! Potential for transient response only
41 FG Verbrennungskraftmaschinen
Variable compressor
Potential ! extend surge line / map
width ! apply operation to areas of
good compressor efficiency Challenges • complexity • limited use
sour
ce; I
AV /
VW
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
42 FG Verbrennungskraftmaschinen
Variable compressor Potential assessment
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
! Development since 10 years, still research ! Effects on compressor map width, eventually transient
response ! Different problems, little advantage ! Potential only in niche product (e.g. high specific engine
power)
43 FG Verbrennungskraftmaschinen
Passenger cars Turbocharger demands & technologies
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
level of relevanz WG VTG two-stage
e-turbo
ball bear.
TiAl axial turb.
var. compr
efficiency
boost pressure
operation range
transient response
controllability
durability
noise
44 Department of Internal Combustion Engines 44 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Engine process simulation
FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Hybrid powertrain
clutch gear differential
Driving profile (vSoll))
Pedals
VM
Wheel Vehicle
Pedal position comparing vIst / vSoll
Vehicle data - mFzg - cW • A - etc. vIst
Pedal position
nAntr MAntr
vIst
Gear selection
nM
EM Powertrain
nM Md
nM Md + MEM
Battery Pel
Powertrain manager
Driver incl. gear change
strategies
FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
mLΔhV .
mAΔhT .
Hybrid powertrain Extension of degree of freedom of supercharging
clutch / gear / differential
VM
nAntr MAntr
Gear selection
EM Powertrain
nM Md
nM Md + MEM
Battery Pel
Boosting system (incl. compound)
Pel
Pmech
56 FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Heat-up performance RDE time scale
Turbulence 0,0000005 s
Blade passing 0,00005 s
Engine pulsation 0,005 s
Load step 5 s
Cycle 5000 s
time scale issue ▶ models and
simplification necessary
57 FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Cycle analysis NEDC G
esch
win
digk
eit [
km/h
]
0
20
40
60
80
100
120
140
Zeit [s]0 200 400 600 800 1000 1200
Geschwindigkeit NEDC Beschleunigungsbereich Bereich konstanter Fahrt Bremsbereich Stillstandsbereich Restlicher Bereich
58 FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Comparison WLTC / NEDC
WLTC NEDC
Duration 1800 s 1180 s Ø speed 46,5 km/h 33,6 km/h Max. acceleration 1,7 m/s² 1,0 m/s² Max. deceleration -1,5 m/s² -1,4 m/s² Standstill 231 s 267 s Number of accelerations 32 (381 s) 31 (278 s) Number of decelerations 46 (622 s) 18 (204 s) Number of stationary operations 44 (350 s) 24 (431 s) Rest 216 s 15 s
59 FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Cycle simplification Definition of representative load change collective
stationary
transient
Examine / develop possibilities in simulation
Definition of criteria for delimitation stationary / transient operation
Model assumptions: stationary operation
Reality: Quasi-stationary operation
Consumption (CO2), emissions (measurable variables (PST))
vs.
NEFZ
RDE
X
Transientfactor
Representative load changes
10 x 5 x +
Correction factor
60 Department of Internal Combustion Engines 60 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Current turbocharger model based on SAE922
61 FG Verbrennungskraftmaschinen
Thermodynamics Mechanics
61
Turbocharger
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
62 Fachgebiet Verbrennungskraftmaschinen
Compressor map
• Relation of and
• Compressor air mass flow
with
• Normalised compressor air mass flow
0,Vm!tV ,π
ref
t
t
refVV T
Tpp
mm ,1
,10, ⋅⋅= !!
0
02TRppAm ev ⋅
⋅Δ⋅⋅⋅⋅= εα!
ττ
κτκ
εκκ
κ
−
−⋅
−
⋅=
−
11
1
12
kritV ππ ≤
skgin
skgin
0
0
ppp Δ−
=τ
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
63 Fachgebiet Verbrennungskraftmaschinen
Compressor map • Total absolute pressure
• Density
• Velocity
• Compressor pressure ratio
2,1
2,12,1 TR
p⋅
=ρ
2,12,12,1 A
mc v
⋅=ρ!
2
22,1
2,12,12,1
cpp tt ⋅+= ρ
t
ttV pp
,1
,2, =π
defines the ratio of total absolute pressure at compressor outlet to total absolute pressure at compressor inlet
tV ,π
static + dynamic part 2s
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
64 Fachgebiet Verbrennungskraftmaschinen
Compressor map
Turbocharger Measurement Technology | KTH Stockholm 2013 | September 2013
• Isentropic compressor efficiency
κκ
π1
,,1,2 )(−
⋅= tVtts TT
Assumed:
• Adiabatic compression
• Mean values of in temperature range R,κ
tV
V
tt
ttssV h
Yhhhh
,,1,2
,1,2
Δ=
−
−=η
2s
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
65 Fachgebiet Verbrennungskraftmaschinen
Turbine map • Represents steady state operation
• Reduced turbine air mass flow
• Density
• Velocity
• Total absolute pressure at turbine inlet
• Turbine pressure ratio
t
tTredT p
Tmm
,3
,3, ⋅= !!
2
23
333cpp t ⋅+= ρ
4
,3
pp t
T =π
3
33 TR
p⋅
=ρ
333 A
mc T
⋅=ρ!
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
66 Fachgebiet Verbrennungskraftmaschinen
Turbine map
Turbocharger Measurement Technology | KTH Stockholm 2013 | September 2013
• Turbocharger power balance
• Turbocharger efficiency
• Turbine efficiency
sV
TL
tT
ttsV
sVmsTT hhm
hhmηη
ηηηη =
−⋅
−⋅⋅=⋅=
)()(1
43
1,2
!!
sT
sV
tT
ttsVmsTsVTL P
Phhmhhm
=−⋅
−⋅=⋅⋅=
)()(
43
1,2
!!
ηηηη
msTtTsV
ttsV hhmhhm ηηη
⋅⋅−⋅=⋅−⋅ )(1)( 43,1,2 !!
Assumed:
• turbocharger mechanical losses are assigned to the turbine )( mηPotentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
67 FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Modeling in engine process simulation Comparison cylinder - turbocharger
Heat transfer
Combustion
Wall temperature
Friction
Cylinder Turbocharger
Aerodynamics
Heat transfer
Pulsation
Friction
Model extension requirement
68 Department of Internal Combustion Engines 68 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Advanced turbocharger model
69 Department of Internal Combustion Engines 69 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
a) Pulsation
Problem: engine process simulation uses steady state maps in transient cycle simulation
70 Department of Internal Combustion Engines 70 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Simulation CFD Pulse Simulation
• Separation in volute and turbine wheel by using different evaluation planes
• Mass flow in volute is following a loop around the steady state results due to storage effects
• Loop size widens with higher pulse frequency
• The turbine wheel does not exhibit this behavior
• Major effect on isentropic efficiency that leads to (physically impossible) values greater one
filling
emptying
71 Department of Internal Combustion Engines 71 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Simulation 1-D Pulse Simulation Volute and wheel separated
MF
P [k
g*(K
^0.5
)/(s
*bar
)]
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
turbine pressure ratio ΠT_tt [-]1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2
mturbine;standard mturbine; ideal volute mturbine,volute sparation
mturbine;standard,MW mturbine; ideal volute,MW mturbine;volute sparation;MW
• Pulse simulation with different amplitudes and frequencies
• Volute approaches small show differences in their loops
• Average values are identical • Increased amplitude has no
additional effect towards mean values
72 Department of Internal Combustion Engines 72 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Simulation 1-D Pulse Simulation Volute and wheel separated
turb
ine
effic
ienc
y η
T [-
]
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
turbine pressure ratio ΠT_tt [-]1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2
ηturbine;classic ηturbine;Chen ηturbine,VS
ηturbine;classic,MW ηturbine;Chen,MW ηturbine;VS;MW
mturbine;standard mturbine; ideal volute mturbine,volute sparation
mturbine;standard,MW mturbine; ideal volute,MW mturbine;volute sparation;MW
Difference in efficiency 3 %p.
• Efficiencies show characterisitic loops
• Average values for volute approaches are similar – standard approach deviates
• Increased amplitude has no additional effect towards mean values
73 Department of Internal Combustion Engines 73 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
b) heat transfer and T4
Problem: heat losses in turbine influence turbine efficiency inhomogeneous outlet temperature does generally not allow to compute isentropic turbine efficiency
74 Department of Internal Combustion Engines
Heat-transfer in a turbocharger
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Experiment (diabatic) Simulation (adiabatic)
Turbine Compressor
outTH ,!
TP CP
inCH ,!
outCH ,!
inTH ,!
System boundary
Turbine Bearing Compressor
outTH ,!
TP FrP CP
inCH ,!
outOilH ,!
inOilH ,!
outCH ,!
TQ! CQ!
inTH ,!
System boundary
CTH →!
OilTH →!
75 Department of Internal Combustion Engines
! Compressor
Turbocharger performance map
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
isen
tropi
c co
mpr
esso
r effi
cien
cy η
C,is
[-]
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
corrected mass flow ṁC,0 [kg/s]0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
40000
100000
nTC, corr=160000 min-1
Exp. T3=600°C, TOil=90°CTRef=298KpRef=1000mbar
76 Department of Internal Combustion Engines
! Compressor
Turbocharger performance map
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
TRef=298KpRef=1000mbar
isen
tropi
c co
mpr
esso
r effi
cien
cy η
C,is
[-]
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
corrected mass flow ṁC,0 [kg/s]0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
100000
nTC, corr=160000 min-1
Exp. T3=600°C, TOil=90°C CFD
40000
77 Department of Internal Combustion Engines
! Compressor
Turbocharger performance map
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
isen
tropi
c co
mpr
esso
r effi
cien
cy η
C,is
[-]
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
corrected mass flow ṁC,0 [kg/s]0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
100000
nTC, corr=160000 min-1
Exp. T3=600°C, TOil=90°C Exp. cold T3=25°C, TOil=25°C CFD
TRef=298KpRef=1000mbar
40000
78 Department of Internal Combustion Engines
isen
tropi
c co
mpr
esso
r effi
cien
cy η
C,is
[-]
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
corrected mass flow ṁC,0 [kg/s]0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
100000
nTC, corr=160000 min-1
Exp. T3=600°C, TOil=90°C Exp. cold T3=25°C, TOil=25°C CFD Uncertainty envelope
TRef=298KpRef=1000mbar
40000
! Compressor
Turbocharger performance map
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
CFD only at small rpms inside the envelope.
79 Department of Internal Combustion Engines 79 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Turbine outlet temperature
Heat loss
V-Element Mixer
Problems: • Inhomogeneous temperature at turbine outlet • Heat loss through convection, thermal radiation (to environment) and thermal
conduction (to turbo charger housing " compressor)
80 Department of Internal Combustion Engines 80 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Turbine
Mixer
V-Element Mixer - Concept
! ideal for blending of turbulent gas flows within pipes
! Principle: homogenization of the fluid through vortex detachment
! high mixing qualities, even at short lengths; modular design
! pressure drop ∆p=0,01…0,12 bar
81 Department of Internal Combustion Engines
Effects of mixer and isolation
! Significant influence of heat losses to temperature measurement ! Positive effect of mixer especially at low mass flow ! Positive effect of isolation in the complete range of operation
ṁT=54 kg/h
Markerohne Isolierungohne Mischer
mit Isolierungohne Mischer
mit Isolierungmit Mischer
ṁT=103 kg/h
ṁT=138 kg/h ṁT=278 kg/h
Länge in mm0 400 800 1200
Tem
pera
tur i
n °C
440460480500520540560580600620
T
T4** T4*
T3*
T4
T3
Tem
pera
tur i
n °C
440460480500520540560580600620
Länge in mm0 400 800 1200
ṁT=54 kg/h
Markerohne Isolierungohne Mischer
mit Isolierungohne Mischer
mit Isolierungmit Mischer
ṁT=103 kg/h
ṁT=138 kg/h ṁT=278 kg/h
Länge in mm0 400 800 1200
Tem
pera
tur i
n °C
440460480500520540560580600620
T
T4** T4*
T3*
T4
T3
Tem
pera
tur i
n °C
440460480500520540560580600620
Länge in mm0 400 800 1200
ṁT=54 kg/h
Markerohne Isolierungohne Mischer
mit Isolierungohne Mischer
mit Isolierungmit Mischer
ṁT=103 kg/h
ṁT=138 kg/h ṁT=278 kg/h
Länge in mm0 400 800 1200
Tem
pera
tur i
n °C
440460480500520540560580600620
T
T4** T4*
T3*
T4
T3
Tem
pera
tur i
n °C
440460480500520540560580600620
Länge in mm0 400 800 1200
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
82 Department of Internal Combustion Engines 82 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Adiabatic Measurement Conditions
! Problem: creating an adiabatic situation for a component which normally shows high temperature gradients
! T2, T3 (and Oil temperature) are primarily responsible for heat flows within the turbo charger housing.
Desired conditions for adiabatic measurements:
! T2 = T3 = TOil.mean " reduced heat flow within the turbo charger
! T4 = T0 = 20�C " reduced heat loss from Turbine to measurement point
! Extensive isolation " reduction of heat loss to environment
Oil out
Oil in
T1 T4
T2 T3
Turbo charger test bench – TU-Berlin
83 Department of Internal Combustion Engines 83 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Adiabatic criterion
Definition: • Actual turbine enthalpy flow
plotted over the isentropic compressor efficiency
• Interpolated straight line connects operation points of maximum isentropic compres-sor power
• Distance between intersection of straight and y-axis determines heat transfer under current boundary conditions
Isentropic compressor power PC_is [kW]0.0 0.5 1.0 1.5 2.0 2.5
Turb
ine
enth
alpy
flow
ΔH
T [k
W]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Adiabatic speed lines
230 m/s
270 m/s
310 m/s
350 m/s
380 m/s
84 Department of Internal Combustion Engines 84 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Adiabatic criterion
Experimental results: • Red lines represent
SAE measurements • Black lines represent
measurements under adiabatic conditions
• Black straight lines all cut the y-axis almost at the point of origin
• Red lines indicate significant offset
140k
Isentropic compressor power PC_is [kW]0.0 0.5 1.0 1.5 2.0 2.5
Turb
ine
enth
alpy
flow
ΔH
T [k
W]
0
2
4
6
8
160k185k
208k
233k
137k
TC 1
Isentropic compressor power PC_is [kW]0 1 2 3 4 5 6 7
Turb
ine
enth
alpy
flow
ΔH
T [k
W]
02468
10121416
80k100k
120k
160k180k
adiabatic speed linesspedd lines at 600∞C
TC 2
Isentropic compressor power PC_is [kW]0 1 2 3 4 5 6 7
Turb
ine
enth
alpy
flow
ΔH
T [k
W]
02468
10121416
210m/s
360m/s
440m/s
TC 3
Isentropic compressor power PC_is [kW]0 1 2 3 4 5
Turb
ine
enth
alpy
flow
ΔH
T [k
W]
0
2
4
6
8
10
12
60k80k
100k
120k
adiabatic speed lines speed lines at 600∞C
TC 4
85 FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Turbocharger thermal model
sour
ce; D
r. B
urke
et a
l, U
nive
rsity
of B
ath
Heat model extension for engine process simulation
86 Department of Internal Combustion Engines 86 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
c) friction
Problem: Measurement of friction losses complicated Influence of thrust force
87 Department of Internal Combustion Engines Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Technology for friction measurement
Shutdown experiment ! no thrust load variation ! ventilation losses ! rotor inertia needed
Motor test bench ! specific setup / complex ! unrealistic rotordynamics
Thermodynamic balance ! T4 measurement necessary ! adiabatic conditions necessary ! still not validated
020000400006000080000
100000120000140000160000180000
0 5 10 15 20
Sha
ft sp
eed
[1/m
in]
Time[s]
Run out experiment
Messreihe 1Messreihe 1Messreihe 3
88 Department of Internal Combustion Engines 88 Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Thermodynamic measurement
! Friction calculated by PT = PV + PFriction using T4
! Plausible values
! Same order of magnitude as friction polynomial
! Still poor understanding of friction mechanisms
89 FG Verbrennungskraftmaschinen Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016
Summary
! Different advanced boosting technologies mainly focussing on transient response
! Comparison difficult due to different level of maturity ! Potential for reduction of emissions and fuel
consumption unclear, advanced powertrain simulation necessary, issues:
! complexity of powertrain model due to different details in time and space of sub-models
! advanced turbocharger models necessary
90 Department of Internal Combustion Engines
Kontakt: Prof. Dr.-Ing. Roland Baar TECHNISCHE UNIVERSITÄT BERLIN Fachgebiet Verbrennungskraftmaschinen Carnotstr. 1A D-10587 Berlin Telefon: +49 30 314 26946 Fax: +49 30 314 26105 email: [email protected] Internet: www.vkm.tu-berlin.de
Potentials and limits of turbochargers | Prof. Dr.-Ing. Roland Baar | 04-2016