8/18/2019 Deer10 Baines
1/13
© 2010 Concepts ETI, Inc. All rights reserved.
ORGANIC RANKINE CYCLE TURBINEFOR EXHAUST ENERGY RECOVERY IN AHEAVY TRUCK ENGINE
Nick SharpCummins Turbo
Technologies Ltd.
Derek Cooper,Nick Baines
Concepts NREC
8/18/2019 Deer10 Baines
2/13
© 2010 Concepts ETI, Inc. All rights reserved. 2
Outline
Context Development program• Organic Rankine cycle uses a
refrigerant working fluid that:Is heated by engine exhaust gasExpands through a turbineconnected (through gearing) to
the engine shaft• A novel turbine design is
required because: The operating conditions (speed,flow, pressure ratio, etc) are quitedifferent from those of
conventional turbochargerturbines The fluid properties of therefrigerant are different fromthose of air, exhaust gas, etc
• Investigate a range of turbinearchitectures to determinesuitability, i.e.
PerformanceSize / packaging
Manufacturability• Down-select to the most
promising solution• Detail design, manufacture, and
prototype test
8/18/2019 Deer10 Baines
3/13
3© 2010 Concepts ETI, Inc. All rights reserved.
Design specifications
Turbine RotationalSpeed Gear Ratio
40k rpm 26.7:1
50k rpm 33.3:1
60k rpm 40.0:1
84k rpm 56.0:1
Turbine shaft speeds and gear ratios at B100 condition
Maximum efficiencySmall footprintMinimum shaft speed
Ideal Solution
• Turbine design point rotational speed is set by typical engineoperating speed and consideration of mechanical couplingbetween turbine and engine
8/18/2019 Deer10 Baines
4/13
© 2010 Concepts ETI, Inc. All rights reserved. 4
• Specific speed is auseful way tocharacterizeturbines
• There are good,experience-based,
rules• Design conditions
demand specificspeeds that are wellbelow those oftypical automotive
turbochargers
Turbine selection
Single stageturbine, 84k rpm
Single stageturbine, 40k rpm
Two stage turbine,84k rpm
Automotive turbo-charger typical
( )3 4Speed Volume flow rate
Specific speedSpecific work output
×=
8/18/2019 Deer10 Baines
5/13
© 2010 Concepts ETI, Inc. All rights reserved. 5
• Single stage radial turbine• Two stage axial turbine• Single stage axial turbine
• In each case, consider a range of speeds from 40,000-84,000 rpm
Conceptual designs
8/18/2019 Deer10 Baines
6/13
6© 2010 Concepts ETI, Inc. All rights reserved.
• Efficiency increases withspeed of rotation
• Size decreases with speed
of rotation• Even at the highest speed,
the ratio of passage heightto rotor radius is very small
Single stage radial turbine
8/18/2019 Deer10 Baines
7/13
© 2010 Concepts ETI, Inc. All rights reserved. 7
• Blade height decreasesand tip radius increasesas turbine speed isreduced to maintainsimilar tip speeds
• Efficiency increases withspeed of rotation
• Significant change inwheel speed across bladespan: variable sectionblades are required for all
two-stage designs• Possible to design blades
to be flank-millable withsmall impact on efficiency
Two-stage axial turbine
84k rpm 60k rpm
50k rpm 40k rpm
8/18/2019 Deer10 Baines
8/13
© 2010 Concepts ETI, Inc. All rights reserved. 8
• Tip radius decreases andblade height increases withspeed
• Efficiency increases with
speed• Stator blades are transonic:
exit Mach number = 1.5 – 1.7• Constant section blades are
acceptable (reducesmanufacturing costs)
Single stage axial turbine
8/18/2019 Deer10 Baines
9/13
© 2010 Concepts ETI, Inc. All rights reserved. 9
0
5
10
15
20
25
30
35
40
40000 50000 60000 70000 80000 90000
T i p r a
d i u s
( m m
)
Turbine design speed (rpm)
Two-Stage Axial
Single-Stage Axial
Radial
0.6
0.65
0.7
0.75
0.8
0.85
0.9
40000 50000 60000 70000 80000 90000
A e r o
d y n a m i c e
f f i c i e n c y
Turbine design speed (rpm)
Two-Stage Axial
Single-Stage Axial
Radial
• Two-stage turbine has potential performance, but too complicated• Down-select to single stage axial turbine
Performance summary
Axial turbine architecture
is more competitive atlower turbine speeds
8/18/2019 Deer10 Baines
10/13
10© 2010 Concepts ETI, Inc. All rights reserved.
• Bladed, con-di nozzle • Drilled and reamed conicalnozzle
Supersonic nozzle options
8/18/2019 Deer10 Baines
11/13
11© 2010 Concepts ETI, Inc. All rights reserved.
• Better performance (+5 ptefficiency at maximum loadconditions)
• More expensive tomanufacture. EDM/ECM isrequired
• Throat width ≅ 1 mmDesign and performance isvery sensitive to manufacturingtolerancesTesting will be required toestablish final design
• Circumferentially non-uniformflow entering rotor makesperformance prediction difficult.
Some experience required• Cheaper to manufacture and
easier to hold throat areatolerances
• Design is compromised by size
envelope, and requires adifferent inlet duct arrangement
Supersonic nozzle options
Bladed, con-di nozzle Drilled, conical nozzle
8/18/2019 Deer10 Baines
12/13
© 2010 Concepts ETI, Inc. All rights reserved. 12
• Single stage architecture demands veryhigh flow turning, but this can bemanaged with proper aero design
• Shrouded rotor is required to reduce tipleakage losses, which have a largeimpact on efficiency in a small turbine
Rotor design
8/18/2019 Deer10 Baines
13/13
© 2010 Concepts ETI, Inc. All rights reserved. 13
• The ORC demands a unique turbine solution, and conventionalturbocharger turbine design has little relevance
• The turbine is highly loaded, with a supersonic nozzle• Two nozzle variants were developed to function with a common
shrouded rotor Full admission arc airfoil nozzlePartial admission drilled nozzle
• The turbine performance is very sensitive to rotor leakage flow andproper treatment of this flow is critical
• The airfoil nozzle turbine is predicted to achieve satisfactoryefficiency with proper sealing solutions
Conclusions
Top Related