PPC FOR LOW LOAD CONDITIONS IN MARINE
ENGINE USING COMPUTATIONAL AND
EXPERIMENTAL TECHNIQUES
Presented By:Kendra Shrestha
Authors: K.Shrestha, O.Kaario, M. Imperato, T.
Sarjovaara, M. Larmi
Internal Combusion Engine Research Group
Aalto University of Technology
18.04.2013
Contents
 Partially Premixed Combustion (PPC)
 The Research Engine EVE
 Validation of the computational model
 Current injection system of EVE
 Combustion and Emission Analysis
 Conclusions
Partially Premixed Combustion
 PPC
•
•
•
A compression ignited combustion process in which fraction of fuel is
injected early so called the pilot injection followed by main injection close to
TDC.
Ignition delay is controlled to enhance better homogeinity of air-fuel
mixture.
PPC intend to endow better combustion with low NOx and Soot emissions.
 Problems with PPC
•
•
Spray-Wall impingement
Lubrication oil dilution resulting to the formation of unburnt HCs
 Objective of the study
•
To Investigate the optimal conditions for the existing single cylinder EVE
engine accompanying the PPC mode of combustion.
Research Engine EVE
Number of Cylinder
1
Stoke (mm)
280
Bore (mm)
200
Connecting Rod length (mm)
614
Number of valves
4
Engine Speed (rpm)
900
Nozzle orifice diameter (mm)
0.36
Number of nozzle holes
Inclusion angle
9
1530
Sector Mesh at TDC
Validation of Computational Model
6
x 10
Experimental
Computational
Single
Injection
Multiple Injection
Pilot Injection (SOI BTDC)
-
30
Main Injection (SOI BTDC)
4
4
100
80
60
40
Experimental
Computational
12
In-cylinder Pressure (Bars)
Validation Cases
In-cylinder Pressure (Bars)
120
10
8
6
4
20
Injection Quantity (gm/cycle)
657.1
2
652
300
350
400
Crank Angle
450
300
350
400
450
Crank Angle
Total Lambda
1.98
2
Injection Pressure (Bars)
1200 bars
1200 bars
4.5
Experimental
Computational
4
Experimental
Computational
4.5
4
Combustion Model
0.36
0.36
DARS-TIF
DARS-TIF
Heat Release Rate (kJ/deg)
Nozzle -hole Diameter (mm)
Heat Release Rate (kJ/deg)
3.5
3
2.5
2
1.5
1
3.5
3
2.5
2
1.5
1
0.5
0.5
0
340
Gas at
Single Injection
Multiple Injection
Exhaust
Experimental
Simulation
Experimental
Simulation
O2 (%-Vol)
10.9
8.9
11.2
9.3
CO2(%-Vol)
7.3
11.33
6.8
10.54
360
380
400
Crank Angle
420
Single Injection
440
0
300
320
340
360
Crank Angle
380
Multiple Injections
400
Current Injection System
SOI30
SOI35
SOI40
SOI45
Injection Pressure=1200bars
Injection system:153x9x0.36
Combustion and Emission Analysis
 Standard Piston Top
 Deeper Bowl Piston Top
Implementation of Real EGR
•
Basic Idea: EGR calculation is based on replacing the fresh charge by EGR
gases.
EGR Gases
O2
CO2
H2O
CO
H2
N2
EGR fraction 0.199493 2.59E-02 1.23E-02 6.00E-04 2.60E-05 0.761708
20% EGR level
Combustion and Emission Analysis ...
Effect in soot formation due to piston bowl shape
Standard Piston Top

2 different injection settings are
implemented keeping the case with
current injection system (PPC 30) as
baseline case.
CASES
Injection
Pressure (bars)

Total fuel injected=652gm/cycle
PPC 30
1200
0.36
153
30

Pilot injection=39%
CASE 1A
2182
0.31
140
35

Total Lambda=2

CASE 2A
2182
0.31
120
30
SOMI =4 CAD BTDC
Nozzle
Inc
diameter(mm) Angle
SOPI
(BTDC)
Standard Piston Top ...
INC 153
INC 140
Standard Piston Top ...
9x153x0.36 SOP-30 SOMI=-4
9x140x0.26 d=0.26 SOPI -30 SOMI-4
Deeper Bowl Piston Top
Injection Details
9 holes cases
10 holes cases
Inc
Angle
SOPI
d=0.26
IMEP
360
% of fuel
burnt
d=0.22
IMEP
360
% of fuel
burnt
140
40
CASE 1B
17.90
87.23
CASE 1C
14.95
71.061
140
30
CASE 2B
19.37
94.5
CASE 2C
17.5
85.84
135
40
CASE 3B
15.37
76.18
CASE 3C
17.57
70.97
135
30
CASE 4B
19.19
93.95
CASE 4C
16.61
82.17
SOPI -40 Yfuel scale (0-0.05)
SOPI -40 Spray visualization at SOPI 40 BTDC
SOPI -25 Yfuel scale (0-0.05)
SOPI -25Spray visualization at SOPI 25 BTDC
Effect of SOPI in mixture formation and spray wall impingement
9 holes vs 10 holes
Conclusions
Difficult to maintain the condition accompanying the PPC with the conventional
injection system.
 Piston position and the start of injection is the crucial parameter in determining good
fuel-air mixture prior to combustion.
 Air fuel homogeneity is dependent on sweep of inclusion angle and increased injection
pressure.
 140 Inclusion angle was figured out to be an optimal inclusion angle favoring the PPC
mode of combustion in the EVE.
 Piston bowl plays an essential role in determining good air-fuel mixture prior to
combustion thus reducing soot emission.
9 holes injectors showed the better results as compared to the 10 holes injectors due to
the increased momentum of single spray of 9 holes than that of 10 holes.

Conclusions...
96
1,00
0,80
BASELINE
0,60
Standard bowl (CASE 1A
EGR20%)
0,40
Deeper Bowl (CASE 2B)
0,20
0,00
Percentage of fuel burnt
Normalized Emissions
1,20
94
92
90
BASELINE
88
Standard Bowl (CASE1A
EGR20%)
86
Deeper Bowl (CASE 2B)
84
82
80
NOx
CO
Soot
With the injection optimization and implementation of EGR, NOx has been
reduced by around 44%, CO by 60% and Soot by 66% in the standard piston top.
 The piston optimization resulted in more promising result with 58% reduction in
NOx, 55% reduction in CO and 67% reduction in Soot.
Thank you for your attention !!!!