Design and development of a Low Pressure Turbine

Design and development of a Low Pressure
Turbine (LPT) for turbocompounding
applications using RICARDO WAVE
Authors:
Dr. Alessandro Romagnoli (Imperial College London)
Dr. Aman Bin-Mamat (Universiti Teknologi Mara)
Prof. Ricardo Martinez-Botas (Imperial College London)
Contents
• Energy
Recovery
• HyBoost project
• Steady State Performance of the LPT
• Engine Implication using RICARDO WAVE
• Current Progress
• Benefits associated with the Low Pressure
Turbine
Comparison Energy Recovery Systems
Bottoming
Rankine
Cycle
Thermoelectric
Generator
Turbocompounding
Advantage
• Not increase
pumping loss
• Higher BSFC
reduction
Disadvantage
• Installation
problem
• Hazardous liquid
• Cost ineffective
• Lightweight
• Not increase
pumping loss
• Large exhaust
surface area
• Cost ineffective
• Easily Bolt-on
• Lower mass
flow capacity
• Low pressure
turbine design
• Increase pumping
loss
• Lower pressure
• Electric generator
limitation
Family of Turbocompounding
John
Deere
Electric
Turbocompound
Electric Assisted
Turbocharger
Bowman
Radial Turbine
Company: Caterpillar
Separate Turbine
Radial Turbine
Turbocompounding
Mechanical
Turbocompound
CPT
Lower Power ICE
Axial Turbine
Company: Cummins
Radial Turbine
Company: Voith
Potential: Ford/Family Car
Radial Turbine
Contents
•
Energy Recovery
•
HyBoost project
•
Steady State Performance of the LPT
•
Engine Implication using RICARDO WAVE
Current Progress
Benefits associated with the Low Pressure Turbine
•
•
HyBoost - Hybridised Boosted Optimised
System with Turbocompound
Belt starter
generator
“12+X”
energy
storage &
controller
Downsized, DI,
turbocharged engine
Electric
turbo-compound
Targets (C-segment car):
<100g/km NEDC CO2; cost below Diesel
Target Assumptions:
169g/km
Base vehicle (2.0 Litre Gasoline):
+
-
Conventional
turbocharger
Electric
supercharger
Aggressively downsized DI, low loss engine
-25%
Add cooled EGR and Miller cycle operation
-6%
Add stop-start and 6kW re-generation
-10%
Taller gear ratios + gearshift indicator light
-7%
HyBoost vehicle (1.0 litre Gasoline)
Design, implementation and
assessment of a high
efficiency TURBINE for
electric turbo compounding
99.7g/km
Electric machine
limitations:
• Const. speed: 50000 rpm
• Power output: 1kW
Preliminary analysis – RICARDO WAVE
• A validated WAVE model of a 1.0 litre three cylinder gasoline engine was
provided by RICARDO plc.
The model was modified and the turbocompound unit was included
in the model in two different locations (PRE/POST CATALYST)
Given the very early stage of the analysis, the turbocompound
unit was modelled as a “mapless” turbine.
This element corresponds to an adiabatic nozzle where
the input is the nozzle diameter, the isentropic
efficiency, choking pressure ratio
A set of different diameters and efficiencies
was assessed and the boundary
conditions for the LPT could be evaluated
Preliminary analysis – RICARDO WAVE
Turbocompound
position
Engine speed (full
load)
Pre-Catalyst position
Post-Catalyst position
Downstream the HP
turbocharger
At the end of the muffler
1000 to 6000 rpm
1000 to 6000 rpm
70%, 40%
70%, 40%
Isentropic efficiency
Turbine type
Effective throat diameter [= diameter corresponding to the effective
geometrical area of the turbine → the inlet to the nozzles for the case
under study]
Nozzle
42 mm, 49 mm (18mm, 25mm small turbine)
Engine speed: 3000 rpm
Ø18 mm – η≈70%
η≈40%
Ø25 mm – η≈70%
η≈40%
Ø42 mm – η≈70%
η≈40%
Ø49 mm – η≈70%
η≈40%
0.0058 / 0.0086
0.0098 / 0.0164
0.0391 / 0.0542
0.0551/ 0.0563
T inlet [K]
1167 / 1093
1094 / 1128
1156 / 1165
1164 / 1164
T exit [K]
1102 / 1068
1064 / 1107
1147 / 1159
1159 / 1161
P inlet [bar]
1.226 / 1.215
1.231 / 1.242
1.189 / 1.211
1.181 / 1.18
P outlet [bar]
1.149 / 1.128
1.143 / 1.144
1.144 / 1.151
1.152 / 1.150
PRESSURE RATIO
1.067 / 1.078
1.075 / 1.081
1.039 / 1.052
1.025 / 1.024
Turbine
MASS FLOW [Kg/sec]
Requirements for Low Pressure Turbine
RICARDO WAVE
Total inlet
temperature
≈ 1.1
70%
1100 K
60%
Commercially available
turbines provide
efficiencies below 40%
Total-to-static Efficiency, ηt-s
Turbine
expansion ratio
80%
50%
40%
30%
20%
For PR≈1.1 the turbine
efficiency is below 40%
10%
A bespoke turbine
design is required to fill
the gap existing in
current technology
0%
1.0
1.2
1.4
Pressure Ratio, PR
50% Speed
60% Speed
1.6
70% Speed
1.8
2.0
80% Speed
2.2
90% Speed
2.4
2.6
100% Speed
Low Pressure Turbine Geometry
A mixed flow turbine was designed:
•
•
•
•
•
Initial design started with 0-D analysis (in house meanline model)
3-D CAD model of the wheel was developed
Single passage/Full passage CFD (ASME Articles 2011/2012)
Prototype for cold testing at Imperial College London
Prototype for hot testing at Ricardo plc
Low pressure turbine
Number of Blades
9
Leading Edge Root Mean Square Radius
42.2 mm
Trailing Edge Tip Radius
22.7 mm
Cone angle
20°
Inlet Blade Angle
varied
Rotor blade length
33.5 mm
Comparative study
A4/A3
ηt-s,design
Speed
[rpm]
PR
Low pressure turbine (LPT)
0.35
>70%
50000
1.1
ABB – medium capacity
1.1
80%
60000
2.0
CAT – medium capacity
0.9
84%
98000
1.6
HONDA - small capacity
0.8
72%
160000
2.0
Contents
•
•
Energy Recovery
HyBoost project
•
Steady State Performance of the LPT
•
Engine Implication using RICARDO WAVE
Current Progress
Benefits associated with the Low Pressure Turbine
•
•
Cold-Flow Testing Low Pressure Turbine
• Low pressure turbine in the
Imperial College test facility
• Rapid prototyping technique for
volute and ducts manufacturing
Cold-Flow Testing Low Pressure Turbine
Normalised Total-to-static Efficiency, ηt-s
1.15
Experimental results
1.10
1.05
≈70% design
efficiency
level
1.00
0.95
0.90
0.85
0.80
0.75
0.70
Very Low PR
0.65
0.60
1.00
1.05
1.10
1.15
1.20
1.25
1.30
1.35
Pressure Ratio, PR
80%
30000
• Low pressure turbine in the
Imperial College test facility
• Rapid prototyping technique for
volute and ducts manufacturing
90%
40000
100%
50000
110%
60000
120%
70000
• Maximum efficiency occurring in a very
low pressure ratio region
• Total-to-static efficiency at design
value is higher than 70%
Contents
•
Energy Recovery
• HyBoost project
• Steady State Performance
• Engine Implication using RICARDO WAVE
• Current Progress
• Benefits associated with the Low Pressure Turbine
Engine implications
Type of engine:
 Gasoline
engine: 1.0L Turbocharged (mild-hybrid)
Analysis using RICARDO WAVE:
 The
analysis, preliminary in nature, looked at the impact of the
addition of a turbocompund unit on engine performance (BSFC)
at Full and Part load conditions
 Three
different locations for the turbocompounding have been
assessed

The turbocompound unit has been modelled using real
turbine maps generated at Imperial College replacing the
Mapless Turbine element initially used in RICARDO WAVE
HyBoost Engine Layout + LPT
To understand the implication of the LPT on engine performance, different
simulations were ran for LPT: 1kW power output, 50000rpm for the LPT were
considered.
LPT evaluation at Full Load – RICARDO WAVE
Engine rpm
1000rpm to 6000rpm
(steps 500rpm)
Locations
Different locations for LPT
Power target - LPT
1.0 kW
Important: the additional
power generated by the LPT
was fed back into the engine
crankshaft (100% efficiency of
the EG)
Intake Manifold
C
1.0L Engine
Engine
WG
LPT
LPT
EG
Catalyst
Converter
T
WG
Exhaust Manifold
RICARDO WAVE:
HyBoost Engine Layout + LPT
Turbocharger +
External Wastegate
Turbocompound
RICARDO WAVE:
Turbocompounding LPT
SIMULATION
TURBOCOMPOUND
•Compressor used as
loading device (no power
consumed)
•Constant shaft speed
•Bypass to control the target
output power
•Temperature, Pressure,
Mass flow, Power, Torque
mapped through sensors
Engine Architecture Study
Full Load Engine Implication: BSFC
1.02
7%
BSFC values normalized for the
baseline engine at 1500 rpm
6%
0.98
5%
0.96
4%
0.94
3%
0.92
2%
0.9
1%
0.88
0.86
0%
Baseline Engine
0.84
-1%
0.82
-2%
0.8
-3%
0
1000
2000
3000
4000
5000
6000
7000
Engine speed [rpm]
Baseline Engine
LPT - Post Catalyst
LPT - Pre Catalyst
LPT - On WG
ΔBSFC [%]
Normalised BSFC [kg/kg/hr]
1
Potential power recovered
4.5
LPT - Post Catalyst
4
LPT - Pre Catalyst
LPT - Power [kW]
3.5
LPT - On WG
LPT - No WG - Post Catalyst
3
LPT - No WG - Pre Catalyst
2.5
Potentially available
power output for the
Low Pressure
Turbine
2
1.5
1kW power output target
1
0.5
0
0
1000
2000
3000
4000
5000
-0.5
Engine speed [rpm]
• Potential benefit when no power restriction applied.
• Possible application for Mechanical Turbocompounding.
6000
7000
Part Load Engine Implication:
Compressor map
4
3.5
The gray circles represent
the full load points
Pressure ratio, PR
3
2.5
2
1.5
Compressor maximum
efficiency region
1
0.5
Extreme Part Load
0
0
0.02
0.04
0.06
0.08
0.1
0.12
Air flow rate [kg/s]
Eng. Speed: 1500 rpm
Eng. Speed: 2000 rpm
Eng. Speed: 2500 rpm
Eng. Speed: 4000 rpm
Part Load
Full Load
Eng. Speed: 3000 rpm
Full Load Engine Implication:
variation BSFC
1.0%
0.5%
Part Load Ratio
0.0%
0
0.2
0.4
0.6
0.8
1
1.2
ΔBSFC [%]
-0.5%
Full Load
-1.0%
-1.5%
-2.0%
-2.5%
-3.0%
1500 rpm- Crankshaft
1500 rpm - No Crankshaft
2000 rpm - Crankshaft
2000 rpm-No Crank
4000 rpm - Crankshaft
4000 rpm - No Crankshaft
Contents
•
•
Energy Recovery
Geometry and Requirements
Steady State Performance
Engine Implication
•
Current Progress
•
Benefits associated with the Low Pressure Turbine
•
•
Real Engine Testing
In Collaboration with Ricardo plc (Shoreham-By-Sea)
• A prototype for the LPT has been manufactured by Imperial College London
• On-engine testing has been completed and results will be published soon
HOT-WIRE
COMPRESSOR
LOW
PRESSURE
TURBINE
BY-PASS
VALVE
BY-PASS
VALVE
Main
Turbocharger
3
2
4
Turbocompound
1
6
5
7
Contents
•
•
•
•
•
•
Energy Recovery
Geometry and Requirements
Steady State Performance
Engine Implication
Current Progress
Benefits associated with the Low
Pressure Turbine
Benefits associated with Low Pressure Turbine
1. Capability to extract a significant amount of power out from low
energy content exhaust gases;
2. BSFC reduction
3. Compact design
Benefits associated with Low Pressure Turbine
1.
2.
3.
1.
Capability to extract a significant amount of power out from low energy
content exhaust gases;
BSFC reduction
Compact design
It is possible to integrate our concept into a “more electric” power
train (mild-hybrid applications) where the excess energy
recovered is transformed into electrical energy which is then
available for other systems (auxiliaries, supercharging etc);
Benefits associated with Low Pressure Turbine
1.
2.
3.
Capability to extract a significant amount of power out from low energy
content exhaust gases;
BSFC reduction
Compact design
1. It is possible to integrate our concept into a “more electric” power
train (mild-hybrid applications) where the excess energy
recovered is transformed into electrical energy which is then
available for other systems (auxiliaries, supercharging etc);
2. Readiness of the technology
Benefits associated with Low Pressure Turbine
1.
2.
3.
Capability to extract a significant amount of power out from low energy
content exhaust gases;
BSFC reduction
Compact design
1. It is possible to integrate our concept into a “more electric” power
train (mild-hybrid applications) where the excess energy
recovered is transformed into electrical energy which is then
available for other systems (auxiliaries, supercharging etc);
2. Readiness of the technology
3. Possibility of up-scaling to higher power rating as required by
the application as shown by the preliminary data obtained for
the 10L engine
Benefits associated with Low Pressure Turbine
1.
2.
3.
1.
2.
3.
Capability to extract a significant amount of power out from low energy
content exhaust gases;
BSFC reduction
Compact design
It is possible to integrate our concept into a “more electric” power
train (mild-hybrid applications) where the excess energy
recovered is transformed into electrical energy which is then
available for other systems (auxiliaries, supercharging etc);
Readiness of the technology
Possibility of up-scaling to higher power rating as required by the
application as shown by the preliminary data obtained for 10L
engine
4. Adaptability to different applications: including power
generation and marine systems.
Benefits associated with Low Pressure Turbine
1.
2.
3.
Capability to extract a significant amount of power out from low energy
content exhaust gases;
BSFC reduction
Compact design
1. It is possible to integrate our concept into a “more electric”
power train (mild-hybrid applications) where the excess
energy recovered is transformed into electrical energy which is
then available for other systems (auxiliaries, supercharging
etc);
2. Readiness of the technology
3. Possibility of up-scaling to higher power rating as required
by the application as shown by the preliminary data obtained
for 10L engine
4. Adaptability to different applications: including power
generation and marine systems.
5. Possibility to exploit a retrofit solution to current technology as
it is possible to “bolt-on” our concept. Ideally this system can
also be contemplated at the early stages of an engine
program;
Additional activity
• Patent application filed on February 2011
• Continuing development of the LPT for different engine capacity
and applications
• Engage with OEMs to establish collaboration for bring the
implementation of the LPT at next level (integration with
engines, optimization, control system, etc.)
Thank you for
your attention!