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 9 Inclusion angle 153 0 Sector Mesh at TDC
Heat Release Rate (kj/deg) Heat Release Rate (kj/deg) In-cylinder Pressure (Bars) In-cylinder Pressure (Bars) Validation of Computational Model x 10 6 Validation Cases Single Injection Multiple Injection 120 100 Experimental Computational 12 10 Experimental Computational Pilot Injection (SOI BTDC) - 30 Main Injection (SOI BTDC) 4 4 80 60 40 8 6 4 Injection Quantity (gm/cycle) 657.1 652 Total Lambda 1.98 2 Injection Pressure (Bars) 1200 bars 1200 bars Nozzle -hole Diameter (mm) 0.36 0.36 Combustion Model DARS-TIF DARS-TIF Gas at Exhaust Single Injection 20 Multiple Injection Experimental Simulation Experimental Simulation 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 300 350 400 450 Crank Angle 340 360 380 400 420 440 Crank Angle Single Injection Experimental Computational 2 300 350 400 450 Crank Angle 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 300 320 340 360 380 400 Crank Angle Multiple Injections Experimental Computational O2 (%-Vol) 10.9 8.9 11.2 9.3 CO2(%-Vol) 7.3 11.33 6.8 10.54
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. Total fuel injected=652gm/cycle Pilot injection=39% Total Lambda=2 SOMI =4 CAD BTDC CASES Injection Pressure (bars) Nozzle diameter(mm) Inc Angle SOPI (BTDC) PPC 30 1200 0.36 153 30 CASE 1A 2182 0.31 140 35 CASE 2A 2182 0.31 120 30
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 -25 Yfuel scale (0-0.05) SOPI -40 Spray visualization at SOPI 40 BTDC 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.
Normalized Emissions Percentage of fuel burnt Conclusions... 1,20 96 1,00 94 0,80 0,60 0,40 0,20 BASELINE Standard bowl (CASE 1A EGR20%) Deeper Bowl (CASE 2B) 92 90 88 86 84 82 BASELINE Standard Bowl (CASE1A EGR20%) Deeper Bowl (CASE 2B) 0,00 NOx CO Soot 80 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.
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