Rémi DACCORD, C.T.O., EXOESexoes.com/site_v2/wp-content/uploads/2017/04/2013_ATZ_LUDWIG… · C a lc ula te d is e ntropic e ffe c tiv e ne s s v s . pre s s ure ra tio C ounte rflow

www.exoes.com 05/11/2013 1

Heavy-Duty, On- and Off-Highway Engines 2013, 8th International MTZ Conference

5 and 6 November 2013, Ludwigsburg, Germany

Heat recovery with piston expanders

Rémi DACCORD, C.T.O., EXOES


Why waste heat recovery?

WHR will help to cut fuel consumption on HD engines

Sources: Roland Berger, EPA, NHTSA (1) GVWR: Gross Vehicle Weight Rating

Heavy-vehicles standards for US model years 2017 Service Class

Weight

Rating (lbs)

EPA CO2 Standard

(g/ton-mile)

NHTSA Fuel

Consumption Standards

(gal/1,000 ton-mile)

Light - Heavy GVWR1 ≤ 19,500 373 36.7

Medium - Heavy19,500 < GVWR ≤

33,000225 22.1

Heavy - Heavy 33,000 < GVWR 222 21.8

Several global CO2 reduction plans (IEA Scenario 450…)

Euro VI and coming norms on pollutants

Source: Frost and Sullivan

Medium and heavy-duty commercial vehicle CO2

emission forecasts 900

650

540

-25 to -30%

-35 to -40%

950

800

620

Average CO2 emissions for new vehicle fleet Average CO2 emissions for vehicle stock


1. General layout of a WHR system

2. Expander technology comparison

3. Oil-free single cylinder development

4. 0D model results for performance assessment

5. 0D model results for expander design

6. Prototype and tests results

Content


Rankine cycle specifications

Main radiator ICE

Post-treatment

Condenser

Expander

Charge pump (variable speed) Tank + filters

EGR Evaporator

Exhaust bypass valve

Subcooler

Exhaust Evaporator

Bypass

Example of a WHR system: Torque re-injection Evaporator: EGR (300°C-600°C), Exhaust (300°C), both in series or parallel Condenser: existing cooling loop (90°C) or additional circuit (LT)


Compactness

Compactness

Expander technology overview

Piston expander

Scroll expander

Oil-free piston expander development

Screw expander

Impulse turbine

Droplets

Cost

Lubrication

Efficiency

Lubrication

Efficiency

Lubrication

Cost

Issues:


2kWelec piston expander Non lubricated piston/cylinder arrangement Performance test bench with static burner as hot source 9,000km travelled during endurance tests 0D and 1D models calibration

Single cylinder expander

Engine parameters

Displacement volume Vc in cm3 (in

3) 443 (27,03)

max. Engine speed (rpm) 1800

Nominal supply pressure in bar (psi) 30 (420)

Nominal exhaust pressure in bar (psi) 0,6 (8,4)

Nominal steam overheating in °C (°F) 100 (212)

Maximal electric power in kW 3

Ise

ntr

op

ic e

ffe

ctive

ne

ss x

me

ch

. e

ffic

ien

cy [

]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Pressure ratio [ ]

10 15 20 25 30 35 40

Calculated isentropic effectiveness vs. pressure ratio Counterflow testNrot=900 rpm, Overheating=100°C

Test datas Model


Exoès research is at the state-of-the-art in terms of unlubricated contacts in hot steam

High temperature tribology

Kv: wear rate [mm3/N.m]

10E-9

10E-8

10E-7

10E-6

10E-5

10E-4

Typ

ical

val

ue

s fo

r lu

bri

cate

d s

yste

ms

Typ

ical

val

ue

s fo

r o

il-fr

ee

sys

tem

s

Achieved Exoès 2010

Achieved Exoès Q3 2012

Achieved Exoès Q2 2013

Target Exoès 2015

Endurance test bench Unlubricated sliding contacts usually show high wear rates.


Carefully select appropriate materials which outperform classic solutions by several orders of magnitude

Average pressure: 6 bars Average rotating speed: 1,200 RPM Temperature: 180°C Average linear speed: 3.1 m/s

. wear rate <5.10-8 mm3/N.m

. Lifetime >3 years w/o maintenance on the piston rings for long haul trucks

Wear rate as a function of the sliding distance

High temperature tribology


Evaporator model:

Simple fixed pinch model

Design of an expander for trucks

0D Model assumptions

0 10 20 30 40 50 60 7050

100

150

200

250

300

350

400

450

500

550

Energy [kW]

Tem

pera

ture

[°C

]

EGR & exhaust evaporator temperature



0D Model assumptions

Source: Glavatskaya, Y.; Podevin, P.; Lemort, V.; Shonda, O.; Decombes, G.; Reciprocating Expander for an Exhaust Heat Recovery Rankine Cycle for a Passenger Car Application, Energies 2012, 5, 1751-1765, doi: 10.3390: en506175

Expander model:

Swept volume, speed and expansion ratio

Leaks model is a subsonic or sonic flow through a simple nozzle.

Mechanical efficiency is a polynomial law on inlet pressure and speed


Effective isentropic efficiency

Expander power to ICE power ratio on ESC B75 point

ICEICE

ppmechai

T

WWR

.

exp,.Exp/ICE

mhh measinwfisexwfinwf

mecha

is

W

,,,,,).(

Indicators definitions

32.7 39.0

2.7

36.0 54.0

3.9

38.4

65.3

4.7

44.2

92.6

6.7

Pin [bar] Rvap/waste [%] Rexp/ICE [%]

EGR

Exhaust

Exhaust EGR series

Exhaust EGR parrallel


Results: expander 800cm3 / expansion ratio 20 / drive ratio 3 / condensing temperature 80°C / fluid: ethanol

Considering side effects, fuel cuts may range from 2 to 6 %


7.5

33.4

3.4 1

38.4

4.7 0.43

32.3

4.8 1

48.3

4.1

Pex [bar] Pin [bar] Rexp/ICE [%]

R245fa Ethanol Water Water

12.6

32.7

2.2 2.2

58.2

3.7 1

48.3

4.1

Pex [bar] Pin [bar] Rexp/ICE [%]

Additional cooling load in case of exhaust heat recovery

Front space already saturated

Considering high condensing temperatures to use the existing cooling circuit

Condensing temperature sensitivity analysis: 80°C 100°C

Cooling the Rankine cycle is the mean issue

Results: evaporators in series / expander 800cm3 / expansion ratio 15 (6 for R245fa) / drive ratio 3



Radial piston expander on a swashplate architecture

Swept volume: 800cm3

Expansion ratio: as high as possible

800cm3 (EGR only) Expansion ratio 20

To choose the best compromise for expander sizing

Results: B75 / evaporators in series / fluid: ethanol / Condensing temperature 80°C / drive ratio 3


0

2

4

6

8

0

20

40

60

80

0 200 400 600 800 1000 1200 1400

[%]

[ba

r]

Swept volume [cc]

Pin_parallel Pin_EGR

Rexp/ICE_parallel Rexp/ICE EGR

0

1

2

3

0

5

10

15

20

25

30

35

0 5 10 15 20 25

[%]

[ba

r]

RE

Pin Rexp/ICE


Decisive internal leaks 1D model including piston leakage: an optimum expansion ratio

level arises for prototyping, it is important to be able to adjust the expansion

ratio the find the optimum according to the real leaks

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2.5 5 7.5 10 12.5 15

Ise

ntr

op

ic e

ffic

ien

cy [

-]

Expansion Ratio [ -]

Isentropic efficiency as a function of the piston annular radial clearance

and the expander expansion ratio

δ= 0.000 mm

δ= 0.010 mm

δ= 0.015 mm

δ= 0.020 mm

Assumptions: Ethanol, 30bar, 230°C No friction losses 3600RPM


1:3-scale prototype

Data Value / Description

Engine architecture Swashplate

Cylinder(s) 5 cylinders

Capacity 183cc

Maximum speed 6,000rpm

Expansion ratio 5-12 ; adjustable

Prototype weight 18kg

Projected weight in mass production

12kg

Size L280mmxD160mm

Working fluid Water / Ethanol

Peak shaft power 6kW

Performance tests in progress Endurance tests to be done in 2014

Oil-free hot end Lubricated crankcase Separation device with low leakage Lubricant maintenance after 1500h


Test results with water

Early test done at very low expansion ratio, set to 5.3, which limits the maximal isentropic effectiveness to 55% for a pressure ratio of 30. Speed sensitivity

0%

10%

20%

30%

40%

50%

60%

3000 RPM 3500 RPM 4000 RPM Ideal

Friction

Others

Leakage

Net isentropic effeciency


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2.5 5 7.5 10 12.5 15

Ise

ntr

op

ic e

ffic

ien

cy [

-]

Expansion Ratio [-]

Isentropic efficiency as a function of the piston annular radial clearance

and the expander expansion ratio

δ= 0.00000 mm

δ= 0.01000 mm

δ= 0.01500 mm

δ= 0.02000 mm

Test results with water

Last test result 18/10/2013

Tests with ethanol are in progress, better results expected

Assumptions: Water, 30bar, 330°C No friction losses 3500RPM

To be tested in December 2013

To be tested in 2014

Leakage sensitivity


1. Calibrated tools for expander desing

2. Demonstrated oil-free running is feasible

3. Manufactured a compact expander prototype

4. We are engaged in a race for efficiency by reducing the internal leakage

5. We will launch wear tests soon with latest design and materials

Summuary


Thank you for your attention !

[email protected]

Single cylinder

EVE-C-200 6kW

Test in progress Available on March 2013

EVE-T 15kW

Design in progress Available on Sept. 2014

Documents

Rémi DACCORD, C.T.O., EXOESexoes.com/site_v2/wp-content/uploads/2017/04/2013_ATZ_LUDWIG… · C a lc ula te d is e ntropic e ffe c tiv e ne s s v s . pre s s ure ra tio C ounte rflow