Direct Injection System for a Two Stroke Engine
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Direct injection system for a two stroke engine Master’s Thesis in the Automotive Engineering Master's programme JOSE RODOLFO I. CERVANTES TREJO Department of Applied Mechanics Division of Combustion CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2011 Master’s Thesis 2011:42 MASTER’S THESIS 2011:42 Direct injection system for a two stroke engine Master’s Thesis in the Automotive Engineering Master's programme JOSE RODOLFO I. CERVANTES TREJO Department of Applied Mechanics Division of Combustion CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2011 Direct injection system for a two stroke engine Master’s Thesis in the Automotive Engineering Master's programme JOSE RODOLFO I. CERVANTES TREJO © JOSE RODOLFO I. CERVANTES TREJO, 2011 Master’s Thesis 2011:42 ISSN 1652-8557 Department of Applied Mechanics Division of Combustion Chalmers University of Technology SE-412 96 Göteborg Sweden Telephone: + 46 (0)31-772 1000 Cover: Figure text for the cover picture (if applicable), possibly with reference to more extensive information in the report. Name of the printers / Department of Applied Mechanics Göteborg, Sweden 2011 Direct injection system for a two stroke engine Master’s Thesis in the Automotive Engineering Master's programme JOSE RODOLFO I. CERVANTES TREJO Department of Applied Mechanics Division of Combustion Chalmers University of Technology ABSTRACT Direct injection is becoming an important option to further optimize internal combustion engines. In the case of two stroke engines, the opportunity of dramatically reducing the HC emissions by almost eliminating short circuit while scavenging, makes this system even more attractive. For small two stroke engines, like the ones used to power chain saw tools, the need of a high pressure fuel pump (its size and electricity needs) makes that the use of direct injection becomes not feasible. By using a self pressurized (boosted) direct injector, the opportunity of using direct injection opens for these small engines since a high pressure pump is not needed. The Evinrude E-TEC™ outboard engine uses a direct injection system which makes use of this kind of injectors. The Evinrude E-TEC™ outboard engine is analyzed in a test rig to find out the characteristics of the injector and the combustion modes the engine runs at different speeds and loads. The emissions of the engine are measured, along with the power, speed, combustion chamber pressure trace, bsfc, and voltage and current developed by the injector. Key words: Direct injection, boosted injector, self pressurized injector, E-TEC, Evinrude, test rig. I Contents 1 INTRODUCTION 1 1.1 Purpose 1 1.2 Background 1 1.3 Objectives 1 1.4 Approach 2 2 TWO STROKE ENGINES 3 2.1 Two and Four Stroke Engines 3 2.2 Two-stroke scavenging process 5 3 DIRECT INJECTION 10 3.1 Injection types 10 3.2 Fuel Injectors 12 4 THE EVINRUDE E-TEC™ OUTBOARD ENGINE AND ITS INJECTOR'S CHARACTERISTICS 13 5 METHODOLOGY 15 5.1 Parameters selection 15 5.2 Test Rig Set Up 17 5.3 Experimental Setup 20 5.4 Data Structure 25 6 RESULTS 30 6.1 Torque-Speed curve 30 6.2 Injector parameters 33 6.3 Injection Timing 36 6.4 Specific Fuel Consumption and Emissions 46 6.5 Spray Characterization 50 7 DISCUSSIONS AND CONCLUSIONS 54 7.1 Injection mode 54 7.1.1 Conclusion 1 60 7.2 Influence of Back Pressures 60 7.2.1 Conclusion 2 61 8 APPENDIXES 63 9 REFERENCES 67 10 ACKNOWLEDGEMENTS 68 Figure Index Figure 2-1 The two stroke engine .................................................................................. 4 Figure 2-2 The four stroke engine ................................................................................. 5 Figure 2-3 Scavenging process in the two stroke engine ............................................... 6 Figure 2-4 Mixing process during scavenging ............................................................... 7 Figure 2-5 Short circuit during scavenging ................................................................... 8 Figure 2-6. Different arrangements of scavenging ports. a) Cross scavenge. b) Loop scavenge. c) Uniflow. .................................................................................................... 9 Figure 3-1. Indirect injection, or port injection. ........................................................... 10 Figure 3-2. Direct injection. ......................................................................................... 11 Figure 4-1 The Evinrude E-TEC™ Engine ............................................................... 13 Figure 4-2 Injector size ................................................................................................ 14 Figure 4-3 Injector Construction .................................................................................. 14 Figure 5-1 Engine on rig .............................................................................................. 17 Figure 5-2 Gearbox and brake ..................................................................................... 18 Figure 5-3 Cooling and exhaust separation ................................................................. 18 Figure 5-4 Cooling of gearbox ..................................................................................... 19 Figure 5-5 Exhaust container ....................................................................................... 19 Figure 5-6 Pressure sensor setup .................................................................................. 20 Figure 5-7 Torque curve approximation ...................................................................... 21 Figure 5-8 Measurement points ................................................................................... 21 Figure 5-9 Throttle opening points .............................................................................. 22 Figure 5-10 Propeller's torque curve ............................................................................ 23 Figure 5-11 Full set of measurement points ................................................................ 24 Figure 6-1 Torque-Speed curve ................................................................................... 30 Figure 6-2 Real set of measurement points .................................................................. 31 Figure 6-3 Power-Speed curve ..................................................................................... 32 Figure 6-4 Electrical measurements at 5 Nm and 3000 rpm ....................................... 33 Figure 6-5 Electrical measurements at 46Nm and 3000 rpm ...................................... 34 II Figure 6-6 Injector electrical measurements at 3000 rpm ........................................... 35 Figure 6-7 Injector electrical measurements at 20 Nm ................................................ 36 Figure 6-8 Ignition and Injection timing at 3000 rpm ................................................. 37 Figure 6-9 Time between injection and ignition at a constant speed of 3000 rpm ...... 37 Figure 6-10 Injection time in mSec at 3000 rpm ......................................................... 38 Figure 6-11 Injection time in CAD at 3000 rpm .......................................................... 38 Figure 6-12 Ignition and Injection timing at 30 Nm .................................................... 39 Figure 6-13 Time between injection and ignition at a constant load of 30 Nm ........... 40 Figure 6-14 Injection time in mSec at 30 Nm .............................................................. 40 Figure 6-15 Injection time in CAD at 30 Nm .............................................................. 41 Figure 6-16 Ignition and Injection timing along propeller curve ................................ 41 Figure 6-17 Time between injection and ignition along the propeller curve ............... 42 Figure 6-18 Injection time in mSec along propeller curve .......................................... 42 Figure 6-19 Injection time in CAD along propeller curve ........................................... 43 Figure 6-20 Injection timing map. The values in each area of the contour plot show the range in CAD the injector is injecting at when the engine is operating inside such area. .............................................................................................................................. 44 Figure 6-21 Ignition timing map. The values in each area of the contour plot show the range in CAD the spark plug is igniting at when the engine is operating inside such area. .............................................................................................................................. 45 Figure 6-22 Throttle angle map. The values in each area of the contour plot show the range in degrees the throttle is positioned at when the engine is operating inside such area. .............................................................................................................................. 45 Figure 6-23 bsfc map ................................................................................................... 46 Figure 6-24 HC map .................................................................................................... 47 Figure 6-25 NO map .................................................................................................... 47 Figure 6-26 NO2 map .................................................................................................. 48 Figure 6-27 NOx map .................................................................................................. 48 Figure 6-28 CO map ...................................................................................................