New Ceramic Thermal Barrier Coatings Development in a Spark-Ignition Engine – Experimental Investigation

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Submitted on 12 Dec 2019

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New Ceramic Thermal Barrier Coatings Development in

a Spark-Ignition Engine – Experimental Investigation

Bernard Bouteiller, Alain Allimant, Jean-Marc Zaccardi, Jerome Cherel

To cite this version:

EFFICIENT ADDITIVATED GASOLINE LEAN ENGINE

New Ceramic Thermal Barrier Coatings Development in a Spark-Ignition

Engine – Experimental Investigation

Bernard Bouteiller

1

_{, Alain Allimant}

1

_{, Jean-Marc Zaccardi}

2

_{and Jérôme Cherel}

2

1) Saint-Gobain Research Provence, Cavaillon, France

Contact: bernard.bouteiller@saint-gobain.com

2) IFP Energies nouvelles, Institut Carnot IFPEN TE, Solaize, France

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EFFICIENT ADDITIVATED GASOLINE LEAN ENGINE

This project has received funding from the European Union’s Horizon 2020 research and innovation programme

Funding ≈ 6M€

October 2016 - March 2020

EAGLE project objectives

Long term fleet target of 50 gCO

₂

/km (WLTC)

50% peak thermal efficiency

Ultra-lean mixtures (high air/fuel ratio)

H

₂

boosting

Pre-chamber ignition system

Optimized intake ports

Smart coatings

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CONTENT

Concept

Specifications

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CONCEPT

How can we reduce those cooling losses ?

Adiabatic engine (tested in 80s~90s)



NOT THE SOLUTION : Too much downgrade of the

combustion efficiency due to heat accumulation

Energy losses in internal combustion engine

>30% of fuel energy is lost through heat

energy transfer to cooling system



Heat transfer gas to wall

Φ = Area .

𝐻𝑒𝑎𝑡

𝐶𝑜𝑛𝑣𝑒𝑐𝑡𝑖𝑜𝑛

𝐶𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡

. 𝑇

𝐺𝑎𝑠

− 𝑇

𝑊𝑎𝑙𝑙

Smart coating / thermo-swing coating

SOLUTION ? : Close match between wall and gas

temperature during at every point of the combustion cycle

Gas temperature

Wall temp. Wo coating

Wall temp. W adiabatic engine coating

Source : Mazda, Fuels and

Lubricants Conference, 2015

-360

-180

0

180

360

Tem

per

atu

re

Crank Angle Degrees

TDC

BDC

TDC

BDC

TDC

-360

-180

0

180

360

Tem

per

atu

re

Crank Angle Degrees

TDC

BDC

TDC

BDC

TDC

Reduced T with coatings

-360

-180

0

180

360

Tem

per

atu

re

Crank Angle Degrees

TDC

BDC

TDC

BDC

TDC

Lower Charge Heating

Reduced T with coatings

Temperature swing

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COATING DEFINITION

Close match between wall and gas temperature during at every point of the combustion

cycle



Insulation without heat accumulation

Coating specifications

Low thermal conductivity

Low volumetric heat capacity

Density ; specific heat capacity ; porosity

Low volume => low thickness

Around 100µm

High mechanical strength at medium temperature

Thermal cycling = 10-40 Hz

Smart coating

Temperature

swing

Wall

Fresh

gas

Combustion

gas

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MATERIALS: SCREENING / SELECTION

Material screening from literature

Material selection

criteria : better than

materials which show

positive impact in

literature

(<1.5 W.m

-1

_.K

-1

_;

<3500 kJ.m

-3

_.K

-1

₎

Selection:



Ceramic oxide



Zirconate (MgZr, LaZr, GdZr)



Silicate (BSAS, YMS)



Quasicrystal



Cristome® BT1



Polymer



Ekonol®

0.01 0.1 1 10 100 1000 0 1000 2000 3000 4000 Condu ctiv ity (W/m .K) Heat capacitance (J/m3.K)

Bulk / dense / hot pressed

Al2O3 ZrO2 Steel Air SiO2 Aluminium MgZrO3 mullite Spinel Cordierite Sillimanite Ekonol TiO2 Si3N4 Zircon Y2SiO5 BaLa2Ti3O10 (BLT) LTA Gd2Zr2O7 HfO2 LaPO4 CePO4 NdPO4 SmPO4 EuPO4 GdPO4 Y2Si2O7 La2Zr2O7 BT1 YZr_20%w BSAS CaZrO3 0 0.5 1 1.5 2 2.5 0 1000 2000 3000 4000 Condu ctiv ity (W/m .K) Heat capacitance (J/m3.K)

Coating sprayed

Air SIRPA Ekonol BT1 MgZrO3 Y2SiO5 Gd2Zr2O7 BSAS La2Zr2O7 BaLa2Ti3O10 (BLT) SiO2 YSZ LaPO4 ZrO2 mullite Cordierite TiO2 Zircon LTA CePO4 NdPO4 SmPO4 EuPO4 GdPO4 Y2Si2O7 CaZrO3

Use of Hashin–Shtrikman model to

estimate properties as porous

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0.00

0.50

1.00

1.50

2.00

2.50

0

1000

2000

3000

Conduct

iv

ity

(W

/m

.K)

Heat Capacitance (kJ/m3.K)

Measured at 300 C

BT1 / YMS BT1 / YSZ BT1 / BSAS BT1 / Ekonol 8YZ / Ekonol YMS / Ekonol BSAS / Ekonol

COATING SYSTEM

High mechanical strength at medium temperature

Avoid brittle behavior

Avoid CTE mismatch



Composite of different nature of materials

Ceramic oxide / Polymer

Quasicrystal / Ceramic oxide

Polymer /Quasicrystal

Thermal properties

Inside our target <1.5 W.m

-1

_.K

-1

_{; <3500 kJ.m}

-3

_.K

-1

Selection of two coating materials

• Ceramic oxide (YMS) + Quasicrystal (BT1®)

• Assumption good matching with substrate

• Ceramic oxide (BSAS) + Polymer (Ekonol®)

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APPLICATION TEST / OUTCOMES

Test of insulation coatings on single cylinder engines

Metal single cylinder engine

Optical single cylinder engine

Thermodynamic performance

Temperature swing measurements using LIP

_{(Laser Induced Phosphorescence)}



Fuel consumption



Combustion behavior



Gas emissions



Piston surface temperature

Similar properties

Stroke, bore, CR, …

Lean gasoline engine



= ratio between the actual air-fuel ratio and

the stoichiometric air-fuel ratio

La2O2S:Eu coating

Aluminum piston

Operating condition:

3000rpm-7bar IMEP

Aluminum & steel piston

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BASE LINE : SINGLE LAYER

2 first coatings tested : Coating #A & #C

Main drawback measured

Unburned hydrocarbon emissions increase by 15~20%

Assumption impact of

roughness and/or open

porosity

Name

Coating #A

Coating #C

Nature

Single layer

- Quasi crystal /

ceramic oxide

composite

Single layer

- Polymer /

ceramic oxide

composite

Thickness [µm]

Piston: 126 +/- 7 Piston: 104 +/- 7

Porosity [%]

10

26

Roughness - Ra

[µm]

8

10

Unburned hydrocarbon emissions to be reduced



Fuel trapped in



Roughness ?

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IMPROVE COATING SYSTEM : TOP LAYER

Discriminate effect of porosity and

roughness

Uncoated piston with equivalent roughness

as coating designed and tested

Double layer with

dense top layer

:

Polymer / Ceramic oxide + dense Ceramic

oxide layer (results not shown)

Quasicrystal /Ceramic oxide + sealing layer

Name

Coating #A

Coating #B

Coating #C

Rough piston

Nature

Single layer

- Quasi crystal

/ ceramic oxide

composite

Double layer

- Quasi crystal /

ceramic oxide

composite

- Sealing layer on top

Single layer

- Polymer /

ceramic oxide

composite

Un-coated

Thickness [µm]

Piston: 126

Piston: 160

Piston: 104

-

Porosity [%]

10

10 (bottom layer)

0 (top layer)

26

“0”

Roughness – Ra

[µm]

8

1

10

9

No increase of Unburned HC with dense

layer and rough uncoated piston

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THERMODYNAMIC PERFORMANCE AND TEMPERATURE SWING

Properties of coating tested on single cylinder engines

Name

Coating #A

Coating #B

Coating #C

Coating #D

Coating #E

Nature

Single layer

- Quasi crystal

/

ceramic oxide

composite

Double layer

-

Quasi crystal

/

ceramic oxide

composite

-

Sealing layer

on

top

Single layer

-

Polymer

/

ceramic oxide

composite

Double layer

-

Polymer

/

ceramic

oxide

composite

-

Dense ceramic

oxide

on top

Triple layer

-

Quasi crystal

/

ceramic oxide

composite

-

Dense ceramic

oxide

layer

-

Sealing layer

on top

Schematic

Thickness on parts for

metal engine [µm]

Piston: 126+/- 7 Piston: 160+/- N.A. Piston: 104+/- 7

-

Piston: 207+/- 20

Cyl. head: 154+/- 20

Thickness on parts for

optical engine [µm]

Piston: 158 +/- 8

-

Piston: 126 +/- 10 Piston: 130 +/- N.A.

Piston: 133 +/- 8

Porosity

[%]

10

10 (bottom layer)

0 (top layer)

26

26 (bottom layer)

4 (top layer)

10 (bottom layer)

4 (middle layer)

0 (top layer)

Roughness – Ra [µm]

8

1

10

5

2

Conductivity

[W.m-1.K-1]

0.79

0.88

0.38

0.46

0.85

Heat capacitance

[kJ.m-3.K-1]

1600

2500

1200

1700

2600

Density

4.2

4.1

1.8

2.3

4.2

Several compositions

(QC, CO, P) and structures

(# layer and composite)

From 100 to 200µm

w/ & w/o open porosity

on top layer

Low conductivity

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Crankshaft angle (CAD) Reference Coating #A Coating #C Coating #D Coating #E

TEMPERATURE SWING

Temperature swing (LIP) on

Aluminum

and

Steel

piston

Aluminum piston

Steel piston



Temperature swing measured



Similar temperature swing with Steel and Aluminum piston

2000 rpm – 4 bar IMEP

Aluminum

Steel

Reference: uncoated piston

20-30°C

35-40°C

Reference + coating #A

40-55°C

Not measured

Reference + coating #C

55-65°C

Not measured

Reference + coating #D

60-65°C

Not measured

Reference + coating #E

100-120°C

70-100°C

2000rpm-4bar IMEP

150 175 200 225 250 275 300 325 350 270 315 360 405 450 Pis ton su rf ace temp er atur e (° C)

Crankshaft angle (CAD) Reference

Coating #E

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0.04

0.05

0.06

0.07

0.08

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

Ma

x. h

e

at

re

le

ase

r

at

e

(1/C

AD

)



(-)

Reference

Coating #E - Piston & Cyl. Head (1)

Coating #E - Piston & Cyl. Head (2)

0

5

10

15

20

25

30

35

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

NO

x e

miss

ion

s

(g

/kW

.h)



(-)

Reference

Coating #E - Piston & Cyl. Head (1)

Coating #E - Piston & Cyl. Head (2)

THERMODYNAMIC PERFORMANCE

Combustion behavior : 2 criteria

Max of Heat release rate

NOx emission



Higher combustion temperature

• RoHR shows the combustion (burning rate) speed

• NOx thermal formation process

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38%

39%

40%

41%

42%

43%

44%

45%

46%

47%

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

In

d

ica

te

d

eff

ic

ie

n

cy

(%)



(-)

Reference

Coating #E - Piston & Cyl. Head (1)

Coating #E - Piston & Cyl. Head (2)

94%

95%

96%

97%

98%

99%

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

Comb

u

stion

ef

ficie

n

cy

(%)



(-)

Reference

Coating #E - Piston & Cyl. Head (1)

Coating #E - Piston & Cyl. Head (2)

THERMODYNAMIC PERFORMANCE

Volumetric efficiency

Indicated efficiency

Combustion efficiency

74%

75%

76%

77%

78%

79%

80%

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

V

olu

met

ric

e

ff

ici

e

n

cy

(%)



(-)

Reference

Coating #E - Piston & Cyl. Head (1)

Coating #E - Piston & Cyl. Head (2)



Slightly better intake efficiency : No increase of the fresh air

temperature during the intake

• Consistent with surface temperature measurement

• Drawback of the adiabatic solve with smart coating

90

100

110

120

130

140

150

160

170

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

Coo

lin

g

lo

sse

s

(J

)



(-)

Reference

Coating #E - Piston & Cyl. Head (1)

Coating #E - Piston & Cyl. Head (2)

Cooling losses

3000rpm-7bar IMEP

3000rpm-7bar IMEP

Global efficiency



No gain using coating on

efficiency / fuel

consumption



Small increase (<1%

increase) of cooling losses

𝑉𝑜𝑙. 𝐸𝑓𝑓. =

𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑎𝑐𝑡𝑢𝑎𝑙 𝑎𝑖𝑟 𝑓𝑢𝑒𝑙 𝑚𝑖𝑥𝑡𝑢𝑟𝑒

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EXPERIMENTAL TEST RESULTS SUM-UP

Porosity

Open porosity lead to unburned HC

Roughness

Piston surface roughness has no impact on unburned hydrocarbon emissions and on efficiency

without any temperature swing (uncoated piston)

Coating

Highest temperature swing (center piston) measured with coating #E

Measured on aluminum and results also obtained on steel piston

Higher combustion temperature with coating #E

Combustion speed increase and NOx emissions increase

No decrease of fuel consumption

Cooling losses inside the combustion chamber increased with coating #E

No increase of the fresh air temperature during the intake

Coating qualitatively reach the temperature swing objective



Positive impact on combustion behavior seems showing insulation effect during combustion

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PERSPECTIVE

Coating properties adjustment

Better understanding of the heat transfer physics

Thermal boundary layer investigation

Roughness

Radiative properties

Thermo-mechanical improvement

Combination of the EAGLE breakthrough elements in the same engine

Combustion chamber design & Coating integration using alternative combustion systems

Refine

coating location

to avoid potential coating negative impact

Diffusion-like versus propagation flames

Combustion strategy

www.h2020-eagle.eu

Find us on:

Efficient Additivated Gasoline Lean Engine

Contact: bernard.bouteiller@saint-gobain.com