Direct Injection on Small Two-stroke Engines

Examensarbete för masterexamen

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Type: Examensarbete för masterexamen
Master Thesis
Title: Direct Injection on Small Two-stroke Engines
Authors: Ekelund, Martin
Ganelius, Max
Abstract: The purpose of this project was to find out how converting a small carburetted two stroke engine to direct Injection would affect relevant engine performance parameters such as emissions, power, fuel consumption, reliability etc. An engine based on a Husqvarna 3120 118cc chainsaw was selected for modifications, and an automotive piezo style direct injector from Bosch was picked for its precision and ability to inject small amounts of fuel. The engine was modified in order to accept the direct Injection system and required measurement and monitoring equipment. An Engine management system was designed from scratch based on an Arduino Micro, in order to time the injections and their durations. The carburetted engine was used as a baseline, with the intention of doing a complete map of the direct Injected engine. However, due to problems with wall wetting due to too wide a spray cone angle, no results could be obtained over 80 RPS [4800 RPM]. Results obtained at 80 RPS and at idle show a reduction in fuel consumption of around 40%, and a reduction in hydrocarbon emissions of around 75%. Additionally a literature study has been done regarding the topic of direct injection on two stroke engines, and three different families of injection systems have been found: High Pressure Direct Injection, Low Pressure Direct Injection, and Airassisted Stratified Direct Injection. Several commercially available systems exist both for the high pressure and air-assisted stratified systems, low pressure systems however only exist as proof of concept systems made for various papers. The reduction in emissions presented in said papers show similar numbers to what was found experimentally, showing a reduction in fuel consumption of around 40% and a reduction of hydrocarbon and carbon monoxide emissions of around 80-95%.
Keywords: Energiteknik;Hållbar utveckling;Transport;Energy Engineering;Sustainable Development;Transport
Issue Date: 2018
Publisher: Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper
Chalmers University of Technology / Department of Mechanics and Maritime Sciences
Series/Report no.: Examensarbete - Institutionen för mekanik och maritima vetenskaper : 2018:53
Collection:Examensarbeten för masterexamen // Master Theses

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