Partially Premixed Combustion, PPC – Why all diesel engines

Partially Premixed Combustion, PPC – Why all diesel engines should be run on

gasoline

Bengt Johansson Lund University

First a little statement:

Dual fuel is not needed!

And 100.000 diesel cars per year are filled up with the wrong fuel in UK. Can we expect an average US car owner to

put two correct fuels in two tanks?

But I still think a single fuel is enough…

Scania diesel engine running on gasoline

4

0 2 4 6 8 10 12 1420

25

30

35

40

45

50

55

60

Gross IMEP [bar]

Gro

ss In

dic

ate

d E

ffic

ien

cy [%

]

Group 3, 1300 [rpm]

FR47333CVX

FR47334CVX

FR47336CVX

! ηi=57% 147 g/kWh (@43 MJ/kg heating value)

Outline

• Combustion concepts

• PPC – background

• PPC with diesel fuel

• PPC with gasoline

• Low dilution PPC with ethanol

• Too low load with too high octane number

• Summary

Outline







• Summary

Background Combustion concepts

Spark Ignition (SI)

engine (Gasoline, Otto)

Compression Ignition

(CI) engine (Diesel)

Homogeneous Charge


(HCCI)

Partially premixed

combustion (PPC)

Diesel HCCI

Spark Assisted


(SACI)

Gasoline HCCI

+ High efficiency

+ Ultra low NOx

-Combustion control

-Power density

+ Clean with 3-way

Catalyst

- Poor low & part load

efficiency

+ High efficiency

- Emissions of NOx and

soot

+ Injection controlled

- Less emissions

advantage

Outline







• Summary

Partially Premixed Combustion, PPC

9

-180 -160 -140 -120 -100 -80 -60 -40 -20

1000

2000

3000

4000

5000

6000Spridare 8x0.12x90 & 8x0.12x150, Iso-oktan, CR-tryck 750 bar, Duration 0,6 ms = 3.6 CAD

HC

[ppm

]

SOI [ATDC]-180 -160 -140 -120 -100 -80 -60 -40 -20

200

400

600

800

1000

1200

NO

x [

ppm

]

Def: region between truly homogeneous combustion, HCCI, and diffusion controlled combustion, diesel

HCCI

PPC

CI PCCI

SAE 2004-01-2990

Outline







• Summary

2006-01-3412

Characterization of Partially Premixed

Combustion (PPC)

Christof Noehre, Magnus Andersson, Bengt Johansson and

Anders Hultqvist

PPC with Diesel Fuel!

Experimental setup

Displacement Volume 1951 cm³

Swirl Ratio (standard) 1.7

Swirl Ratio (if modified) 2.9

Fuel Swedish MK 1 Diesel, CN51

Injector holes 8

Injector hole diameter 0.18 mm

Spray umbrella angle 120

12

Specifications of single cylinder engine:

Compression ratios A=12.4:1; B=14.3:1; C=17.1:1

SAE 2006-01-3412

13

Load 8 bar IMEP

Abs. Inlet Pressure 2.5 bar

Engine Speed 1090 rpm

Swirl Ratio 1.7

Compression Ratio 12.4:1 (Low)

Inlet temp without

EGR 25 C

Inlet temp max

EGR 55 C

Emissions at 8 bar IMEP

SAE 2006-01-3412

14

1

4 5

3

Injection virtually finished before start of combustion

15

- One reason: insufficient ignition delay

Why is PPC not possible at highest

compression ratio?

Load 8 bar IMEP



Swirl Ratio 1.7

Effect of EGR and compression ratio at 8 bar IMEP

EGR sweep and compression ratio variation

Increased EGR

• PPC possible at 8 bar IMEP on compression ratios 12.4:1 and 14.3:1.

• Narrower operating range with increased compression ratio.

SAE 2006-01-3412

17

Effect of EGR and compression ratio at 12 bar IMEP

Load 12 bar IMEP



Swirl Ratio 1.7

• PPC only possible at 12 bar IMEP with lowest compression ratio (12.4:1).

• Soot emissions relatively high (compared to 8 bar IMEP).

SAE 2006-01-3412

18

The effect of EGR (and swirl) at 15 bar IMEP

Increased EGR Increased EGR

• Low soot/low NOx combustion possible. • Increased swirl lowers soot emissions, but

primarily before soot hump.

SAE 2006-01-3412

19

6

4 3

Gasoline instead of diesel fuel

Lic. Thesis by Henrik Nordgren 2005 and presented at DEER2005 20

Gasoline instead of diesel fuel

Lic. Thesis by Henrik Nordgren 2005 21

Outline







• Summary

23

Gasoline tests in Scania D12

Bosch Common Rail

Prailmax 1600 [bar]

Orifices 8 [-]

Orifice Diameter 0.18 [mm]

Umbrella Angle 120 [deg]

Engine / Dyno Spec

BMEPmax 15 [bar]

Vd 1951 [cm3]

Swirl ratio 2.9 [-]

Dilution

Lambda 1.5

EGR 50 %

Fuel: Gasoline or Ethanol

SAE 2009-01-2668

24

Emissions – different fuels

2 4 6 8 10 12 14 16 18 200

0.5

1

1.5

2

2.5

Gross IMEP [bar]

So

ot [F

SN

]

Ethanol

FR47330CVX

FR47331CVX

FR47333CVX

FR47334CVX

FR47335CVX

FR47336CVX

FR47338CVX

2 4 6 8 10 12 14 16 18 200

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Gross IMEP [bar]

NO

x [g

/kW

h]

Ethanol

FR47330CVX

FR47331CVX

FR47333CVX

FR47334CVX

FR47335CVX

FR47336CVX

FR47338CVX

2 4 6 8 10 12 14 16 18 200

2

4

6

8

10

12

Gross IMEP [bar]

CO

[g

/kW

h]

Ethanol

FR47330CVX

FR47331CVX

FR47333CVX

FR47334CVX

FR47335CVX

FR47336CVX

FR47338CVX

2 4 6 8 10 12 14 16 18 200

1

2

3

4

5

6

7

8

9

10

Gross IMEP [bar]

HC

[g

/kW

h]

Ethanol

FR47330CVX

FR47331CVX

FR47333CVX

FR47334CVX

FR47335CVX

FR47336CVX

FR47338CVX

SAE 2010-01-0871

Energy flow in an IC engine

FuelMEP

QhrMEP

IMEPgross

lMEPnet

BMEP

QemisMEP

QlossMEP

QhtMEP

QexhMEP

PMEP

FMEP

Combustion efficiency

Thermodynamic efficiency

Gas exchange efficiency

Mechanical efficiency

Net Indicated efficiency

Brake efficiency

Gross Indicated efficiency

FuelMEP

QhrMEP

IMEPgross

lMEPnet

BMEP

QemisMEP

QlossMEP

QhtMEP

QexhMEP

PMEP

FMEP

Combustion efficiency

Thermodynamic efficiency

Gas exchange efficiency

Mechanical efficiency

Net Indicated efficiency

Brake efficiency

Gross Indicated efficiency

MechanicaleGasExchangmicThermodynaCombustionBrake***

25

26 26

Efficiencies 17.1:1

4 5 6 7 8 9 10 11 12 1350

55

60

65

70

75

80

85

90

95

100

Gross IMEP [bar]

[%] Combustion Efficiency

Thermal Efficiency

Gas Exchange Efficiency

Mechanical Efficiency

SAE 2009-01-2668

27 27

4 6 8 10 12 14 16 18 50

55

60

65

70

75

80

85

90

95

100

Gross IMEP [bar]

[%] Combustion Efficiency

Thermal Efficiency

Gas Exchange Efficiency

Mechanical Efficiency

Efficiencies 14.3:1

SAE 2010-01-0871

28 28

Experimental Apparatus, Scania D13

XPI Common Rail

Orifices 8 [-]

Orifice Diameter 0.19 [mm]

Umbrella Angle 148 [deg]

Engine / Dyno Spec

BMEPmax 25 [bar]

Vd 2124 [cm3]

Swirl ratio 2.095 [-]

Standard piston bowl, rc: 17.3:1 SAE 2010-01-2198

29 29 29

20 30 40 50 60 70 80 90 1000

5

10

15

20

25

RON [-]

IME

P g

ross [b

ar]

Stable operational load vs. fuel type

Tested Load Area

30

D13 Running on Diesel & Gasoline

5 10 15 20 25 3034

36

38

40

42

44

46

48

50

52

Gross IMEP [bar]

Bra

ke

Effic

ien

cy [%

]

D13 Gasoline

D13 Diesel

D13 Diesel was calibrated by Scania and the calibration was done to meet EU V legislation.

Average improvement of 16.6% points @ high load!!!

Outline







• Summary

Close to Stoichiometric Partially

Premixed Combustion

- the Benefit of Ethanol in

Comparison to Conventional Fuels

Mengqin Shen, Martin Tuner and Bengt Johansson Lund University

2013-01-0277

Experimental System, Scania D13

Engine Piston Model

33

Scania D13 engine

Fuel Properties

Fuel RON MON CN H/C O/C LHV [MJ/kg]

Stoichiometric A/F Ratio

MK 1 - - 54 1.83 0 43.15 14.49

Gasoline 69 66 - 1.98 0 43.80 14.68

99.5% Ethanol 108 89 - 3 0.5 26.64 9

34

0 1 2 3 4 5 6 752

53

54

55

56

57

CA50 [CAD ATDC]

Gro

ss Indic

ate

d E

ffic

iency[%

]

O

Gross indicated efficiency as a function of combustion phasing (gasoline fuel, IMEP gross 11bar, FuelMEP 20.5 bar, λ=1.85,EGR=38%).

Optimized Combustion phasing

1 1.2 1.4 1.6 1.82

2.5

3

3.5

4

4.5

5

5.5

6

CA

50 [C

AD

AT

DC

]

[-]

MK1

Gasoline

Ethanol

Combustion phasing (CA50) as a function of λ (Fuel MEP 20.5 bar).

35

PPC-RoHR-diesel

-20 -10 0 10 20

0

50

100

150

200

Crank Angle [CAD ATDC]

Ro

HR

/10

[J/C

AD

] / In

jecto

r C

urr

en

t

=1.74

=1.58

=1.16

=1.05

36

PPC-RoHR-gasoline

-20 -10 0 10 20

0

50

100

150

200


Ro

HR

/10

[J/C

AD

] / In

jecto

r C

urr

en

t

=1.74

=1.58

=1.16

=1.05

37

PPC-RoHR-ethanol

-20 -10 0 10 20

0

50

100

150

200


Ro

HR

/10

[J/C

AD

] / In

jecto

r C

urr

en

t

=1.74

=1.58

=1.16

=1.05

38

FuelMEP ~20.5 bar EGR~38%

PPC-Efficiency

1 1.2 1.4 1.6 1.897.5

98

98.5

99

99.5

100

[-]

Com

bustion E

ffic

iency [%

]

MK1

Gasoline

Ethanol

1 1.2 1.4 1.6 1.835

40

45

50

55

[-]

Gro

ss Indic

ate

d E

ffic

iency [%

]

MK1

Gasoline

Ethanol

6% 9% 18%

39

1 1.2 1.4 1.6 1.80

0.5

1

1.5

2

[-]

Com

bustion L

oss [%

]

MK1

Gasoline

Ethanol

Efficiency & Losses

1 1.2 1.4 1.6 1.810

12

14

16

18

20

22

[-]

Exhaust Loss [%

]

MK1

Gasoline

Ethanol

• Relative combustion loss is between 0.2% and 1.7% in all cases.

• Less relative exhaust loss with lower λ . • More heat transfer in stoichiometric PPC due

to higher combustion temperature .High heat transfer loss is the main reason for low efficiency of diesel.

40

1 1.2 1.4 1.6 1.825

30

35

40

45

50

[-]

Heat T

ransfe

r Loss [%

]

MK1

Gasoline

Ethanol

PPC-Emissions

1 1.2 1.4 1.6 1.80

0.2

0.4

0.6

0.8

1

1.2

1.4

UH

C/N

Ox [g/k

Wh]

1 1.2 1.4 1.6 1.80

1

2

3

4

5

6

7

CO

[g/k

Wh]

[-]

CO[g/kWh]

NOx[g/kWh]

UHC[g/kWh]

UHC, CO and NOx emissions as a function of λ (FuelMEP 20.5 bar, EGR 38%, gasoline fuel).

1 1.2 1.4 1.6 1.8 20

2

4

6

8

10

[-]

Soot [F

SN

]

MK1

Gasoline

Ethanol

Soot emission as a function of λ (FuelMEP 20.5 bar, EGR 38%).

41

It is possible to operate PPC from lean conditions to close to stoichiometric conditions.

Gross indicated efficiency decreased for all the fuels in close to stoichiometric operation:

– Ethanol showed higher efficiency and less efficiency reduction than gasoline

and diesel fuel.

Pronounced soot emission increase for diesel and gasoline. Ethanol showed very low soot in all conditions.

Ethanol - Clean Stoichiometric PPC (with TWC).

Observations

42

Outline







• Summary

PPC- LD

Comparison of Negative Valve Overlap (NVO) and Rebreathing Valve Strategies on a Gasoline

PPC Engine at Low Load and Idle Operating Conditions

44

SAE Paper 2013-01-0902

Patrick Borgqvist, Per Tunestål, Bengt Johansson Lund University

Introduction Partially Premixed Combustion – Light Duty Engine

20 30 40 50 60 70 80 90 1000

5

10

15

20

25

RON [-]

IME

P g

ross [b

ar]

PPC Operating Region from Heavy Duty Experiments [1]

•Goal: Increase attainable operating region

45

- Means to reduce minimum load: Injection strategies

- Advanced pilot strategies - Split main Trapping hot residuals - Temperature increase - Dilution - Stratification Glow plug

[1] Manente, V., et al. “An Advanced Internal Combustion Engine Concept for Low Emissions and High Efficiency from Idle to Max Load Using Gasoline Partially Premixed Combustion”, SAE 2010.01-2198

Experimental Setup – Volvo D5

Displacement 480 cm3 (1 cyl)

Number of

cylinders

5 (1 used)

Bore 81 mm

Stroke 93.2 mm

Compression

ratio

16.5:1

Valve timings Fully flexible

46

Nozzle Holes 5

Umbrella Angle 140 deg

Hole Size 0.159 mm

Fuel Injector Standard D5 piston

Engine

Fuel Specification

Fuel RON MON LHV [Mj/kg]

A/F stoich

Gasoline 87 81 43.50 14.60

47

20 30 40 50 60 70 80 90 1000

5

10

15

20

25

RON [-]

IME

P g

ross [b

ar]

Negative Valve Overlap (NVO)

48

-200 -100 0 100 200 300 400 5000

5

10

15

20

25

30

35

40

45

50

55

Crank Angle [CAD]

Pre

ssure

[bar]

/ V

alv

e L

ift [a

.u.]

NVO

Pressure

Intake Valve

Exhaust Valve

NVO

Trap hot residual gas to elevate the initial temperature of the fresh charge of the subsequent cycle Disadvantage Gas-exchange efficiency penalty

Rebreathing

49

-200 -100 0 100 200 300 400 5000

5

10

15

20

25

30

35

40

45

50

55

Crank Angle [CAD]

Pressure [bar]

Intake Valve [a.u.]

Exhaust Valve [a.u.]

Minimum possible NVO

Second exhaust valve opening

Advantage: Improved gas-exchange efficiency Disadvantage: Lower temperature of re-inducted residual gases compared to trapped residuals???

Combustion stability

50

Similar improvement on combustion stability with Rebreathing compared to NVO

NVO [CAD]IM

EP

gro

ss [bar]

NVO: std IMEPnet [bar]

60 80 100 120 140 160 180 200 2201.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

0.15

0.2

0.25

0.3

0.35

0.4

Rebreathing [CAD]

IME

Pgro

ss [bar]

Rebreathing: std IMEPnet [bar]

0 20 40 60 80 1001.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

0.15

0.2

0.25

0.3

0.35

0.4

Unburned Hydrocarbons

51

Similar improvement in hydro-carbon emissions reduction with Rebreathing compared to NVO

NVO [CAD]IM

EP

gro

ss [bar]

NVO: Unburned Hydro-Carbon Emissions [ppm]

60 80 100 120 140 160 180 200 2201.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

100

150

200

250

300

350

400

450

500

Rebreathing [CAD]

IME

Pgro

ss [bar]

Rebreathing: Unburned Hydro-Carbon Emissions [ppm]

0 20 40 60 80 1001.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

100

150

200

250

300

350

400

450

500

Gas exchange Efficiency

52

Gas-exchange efficiency is significantly higher with the Rebreathing strategy compared to NVO

NVO [CAD]IM

EP

gro

ss [bar]

NVO: Gas-Exchange Efficiency [%]

60 80 100 120 140 160 180 200 2201.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

84

86

88

90

92

94

96

Rebreathing [CAD]

IME

Pgro

ss [bar]

Rebreathing: Gas-Exchange Efficiency [%]

0 20 40 60 80 1001.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

84

86

88

90

92

94

96

Net Indicated Efficiency

53

The net indicated efficiency is higher with the Rebreathing case. Note, shown against IMEPnet

NVO [CAD]IM

EP

net [b

ar]

NVO: Net Indicated Efficiency [%]

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

2.8

3

3.2

25

30

35

40

Rebreathing [CAD]

IME

Pnet [b

ar]

Rebreathing: Net Indicated Efficiency [%]

0 20 40 60 80 100

1.6

1.8

2

2.2

2.4

2.6

2.8

3

3.2

25

30

35

40

NVO Injection

54

-200 -100 0 100 200 300 400 5000

5

10

15

20

25

30

35

40

45

50

Crank Angle [CAD]

Pressure [bar]

Valve Lift [a.u.]

Fuel Indicator [a.u.]

NVO Injection

Glow plug: ON Engine speed: 800 rpm Fuel: 87 RON Gasoline

Idea: Fuel reformation to improve the main combustion event

Effect of NVO Injection Timing

55

-40 -30 -20 -10 0 10 20 30 40-5

0

5

10

15

20

25NVO: 220 CAD

Fuel DistributionNVO/Main: 50/50 %

Lambda: 1.08 - 1.42

Crank Angle (Gas-Exchange TDC) [CAD]

Rate

of H

eat R

ele

ase [J/C

AD

]

Effect of NVO-Pilot Injection Timing

-22 CAD

-15 CAD

-10 CAD

-5 CAD

0 CAD

-40 -30 -20 -10 0 10 20 30 40-5

0

5

10

15

20

25NVO: 220 CAD

Fuel DistributionNVO/Main: 50/50 %

Lambda: 1.08-1.42

Crank Angle [CAD]R

ate

of H

eat R

ele

ase [J/C

AD

]

Effect of NVO-Pilot Injection Timing

-22 CAD

-15 CAD

-10 CAD

-5 CAD

0 CAD

NVO Injection – Ignition Delay

56

NVO [CAD]

IME

Pgro

ss [bar]

Ignition Delay (CA10-SOI) [CAD] (NVO Injection)

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

8

10

12

14

16

18

Significant effect on the ignition delay when NVO is sufficiently high, from 200 CAD NVO

NVO Injection – Combustion stability

57

NVO [CAD]

IME

Pgro

ss [bar]

std IMEPnet [bar] (NVO Injection)

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

0.1

0.15

0.2

0.25

0.3

Significant improvement on combustion stability with NVO injection and a high setting of NVO

NVO Injection - HC

58

NVO [CAD]

IME

Pgro

ss [bar]

Unburned Hydro-Carbon Emissions [ppm] (NVO Injection)

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

350

400

450

500

550

600

650

700

Significant reduction of unburned hydrocarbon emissions with NVO injection and a high setting of NVO

NVO Injection - NOx

59

NVO [CAD]

IME

Pgro

ss [bar]

NOx [ppm] (NVO Injection)

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

20

40

60

80

100

120

High NOx emissions in the intermediate region between too low and too high NVO settings Low NOx emissions when engine load is low and NVO is sufficiently high

NVO Injection -Soot

60

NVO [CAD]

IME

Pgro

ss [bar]

soot [FSN] (NVO Injection)

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Soot emissions are much higher when NVO injection is used

NVO Injection -Lambda

61

NVO [CAD]

IME

Pgro

ss [bar]

soot [FSN] (NVO Injection)

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

NVO [CAD]

IME

Pgro

ss [bar]

Lambda [-] (NVO Injection)

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

NVO [CAD]

IME

Pgro

ss [bar]

NOx [ppm] (NVO Injection)

60 80 100 120 140 160 180 200 220

1.6

1.8

2

2.2

2.4

2.6

20

40

60

80

100

120

Putting it all Together

62

1. NVO, single injection 2. NVO with NVO injection, 200 CAD NVO 3. NVO with NVO injection, 220 CAD NVO 4. Rebreathing, single injection

Comparison of different valve strategies and fuel injection strategies, with optimized settings, at low engine speed and load operating conditions


63

Highest combustion stability with the NVO injection strategy

1 1.5 2 2.5 3 3.50.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

IMEPgross [bar]

std

IM

EP

net [b

ar]

NVO, sing. inj.

NVO, NVO inj. 200 NVO


Reb, sing. inj.


64

Soot emissions are significantly higher with the NVO injection strategy depending on NVO setting Higher NVO gives a lower global air-fuel ratio

1 1.5 2 2.5 3 3.50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

IMEPgross [bar]

soot [F

SN

]

NVO, sing. inj.



Reb, sing. inj.


65

Net indicated efficiency is highest with the Rebreathing strategies

1 1.5 2 2.5 3 3.524

26

28

30

32

34

36

38

40

42

IMEPgross [bar]

Net In

dic

ate

d E

ffic

iency [%

]

NVO, sing. inj.



Reb, sing. inj.

Low Load Operating Strategy Summary

66

IMEPgross [bar]

2.0

NVO NVO injection

+ Lowest std of IMEP - soot emissions

Rebreathing

+ highest indicated efficiency - Low load limitation • Tradeoff between Nox and UHC emissions

3.0

Gradually replace hot residuals with EGR to suppress NOx emissions

2.5

Outline







• Summary

Partially Premixed Combustion, PPC

• Compression Ignition should use gasoline not diesel

• PPC is the most efficient of all processes known (using one fuel)! – Combustion Efficiency >99.8%

– Thermodynamic Efficiency= 55-57%

– Gas exchange efficiency reasonable

– Mechanical efficiency high as load can be high

• Load range 1.5-26 (30) bar IMEP

• Low enough emissions – NOx, HC and CO below legal limits without catalytic aftertreatment

– PM low enough using ethanol and low with gasoline

68

The End

Thank you

69

Partially Premixed Combustion, PPC – Why all diesel engines should be run on

gasoline

Bengt Johansson Lund University

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Partially Premixed Combustion, PPC – Why all diesel engines