Design of a Variable Compression Internal Combustion Engine A Major Qualifying Project Report Submitted to the faculty of Worcester Polytechnic Institute In partial fulfillment of the requirements for the Degree of Bachelor of Science In Mechanical Engineering By: Liam Finnegan Quinton Schimmel Submitted On: May 18, 2020 Project Advisor: Robert Daniello 2 Design of a Variable Compression Internal Combustion Engine Acknowledgements We would like to primarily thank Professor Daniello for advising us on this project. He was always well-informed regarding the topics and provided helpful feedback in a timely manner. We would also like to thank Ian Anderson, a member of the Washburn Shops Laboratory Staff for his help with understanding the manufacturability and tolerances of the components we were designing. 3 Design of a Variable Compression Internal Combustion Engine Abstract The purpose of this project is to design a single cylinder internal combustion engine to be used by the Mechanical Engineering Department at WPI to aid in class demonstrations. The engine must be reconfigurable for different operating parameters, and durable enough to withstand sub-optimal operating conditions. It must be able to function with a compression ratio and ignition timing that can be adjusted from 4:1 to 25:1 and able to operate using both gasoline and diesel fuels. The design focuses on the components that are unique to this engine: Acme threading around the cylinder that allows the compression ratio to be varied while the engine is running, a unique crankcase, and a valve train that maintains consistent valve timing as the compression ratio is varied. The engine is designed with the intent to be manufactured by WPI’s machine shop. The result of this project is detailed drawings of the parts, enabling a future team to manufacture the engine. 4 Design of a Variable Compression Internal Combustion Engine Table of Contents Acknowledgements ...................................................................................................................................... 2 Abstract ......................................................................................................................................................... 3 Table of Contents .......................................................................................................................................... 4 Table of Figures ............................................................................................................................................. 5 List of Tables ................................................................................................................................................. 5 Introduction .................................................................................................................................................. 6 Background ................................................................................................................................................... 8 Internal Combustion Engine Overview ..................................................................................................... 8 Ignition and Compression Ratio .............................................................................................................. 10 Engine Design .......................................................................................................................................... 12 Cooperative Fuel Research Engine ......................................................................................................... 15 Designs and Specifications .......................................................................................................................... 18 Crank Case .............................................................................................................................................. 21 Variable Compression Ratio and Cylinder Design ................................................................................... 23 Piston Assembly and Crank Shaft ........................................................................................................... 27 Timing Assembly ..................................................................................................................................... 29 Valve Train and Cylinder Head ................................................................................................................ 31 Conclusions and Recommendations ........................................................................................................... 33 Future Work ................................................................................................................................................ 34 Appendix A: Bill of Materials ...................................................................................................................... 35 Appendix B: Drawings ................................................................................................................................. 38 References .................................................................................................................................................. 56 5 Design of a Variable Compression Internal Combustion Engine Table of Figures Figure 1: Diesel Engine Four-Stroke Cycle .................................................................................................... 9 Figure 2: The Ideal Otto Cycle ..................................................................................................................... 10 Figure 3: Compression Ratio ....................................................................................................................... 11 Figure 4: V-Configuration Engine ................................................................................................................ 13 Figure 5: Piston Diagram ............................................................................................................................. 14 Figure 6: Overhead Valve Diagram ............................................................................................................. 15 Figure 7: Views of the Cooperative Fuel Research Engine ......................................................................... 16 Figure 8: Final Assembly ............................................................................................................................. 19 Figure 9: Final Assembly Cross Section ....................................................................................................... 20 Figure 10: Crankcase Front View ................................................................................................................ 22 Figure 11: Crankcase Rear View .................................................................................................................. 23 Figure 12: Cylinder Height Lowest Configuration ....................................................................................... 24 Figure 13: Cylinder Height Middle Configuration ....................................................................................... 25 Figure 14: Cylinder Height Highest Configuration ...................................................................................... 25 Figure 15: Vibration Reduction Springs ...................................................................................................... 26 Figure 16: Piston Assembly Front View ...................................................................................................... 28 Figure 17: Piston and Crankshaft Assembly................................................................................................ 28 Figure 18: Timing Assembly ........................................................................................................................ 30 Figure 19: Cylinder Head Top View ............................................................................................................. 31 Figure 20: Cylinder Head Bottom View ....................................................................................................... 32 Figure 21: Drawing of Entire Assembly ....................................................................................................... 38 Figure 22: Drawing of Crankcase ................................................................................................................ 39 Figure 23: Drawing of Cylinder Nut Brace .................................................................................................. 40 Figure 24: Drawing of Timing Rod Brace .................................................................................................... 41 Figure 25: Drawing of Cylinder ................................................................................................................... 42 Figure 26: Drawing of Crank Case Cover..................................................................................................... 43 Figure 27: Drawing of Timing Assembly Cover ........................................................................................... 44 Figure 28: Drawing of Crankshaft ............................................................................................................... 45 Figure 29: Drawing of Crankshaft Counterweight and Wrist Pin................................................................ 46 Figure 30: Drawing of