Loh, Jian Haur
(2011)
Design And Performance Analysis Of A Small Two-Stroke Direct Injection Diesel Engine.
Masters thesis, Universiti Sains Malaysia.
Abstract
As oil resources are rapidly being depleted, vehicle fuel efficiency is
becoming more important for consumers. Due to the large number of motorcycles,
improving fuel consumption of motorcycles would greatly reduce fuel demand in
many developing countries. Diesel engines offer the advantages of improved thermal
efficiency, lower pumping losses, lean operation and potentially low friction from
low speed operation with the major disadvantages being a high specific weight and
low power density. Two-stroke engines have the advantage of high power,
lightweight and low friction while premixed two-strokes have the major
disadvantages of high fuel consumption and emissions from fuel short-circuiting.
When combining the diesel cycle with two-stroke cycle, the problematic fuel shortcircuiting
is eliminated through direct fuel injection while the low power density of
diesel cycle is improved. In this research, the performance in terms of power output
and fuel consumption of a 118cc two-stroke direct injection diesel engine was
evaluated. Dynamometer testing and simulation of a prototype engine were
conducted for that purpose. The prototype engine was built by converting an existing
two-stroke gasoline engine while simulation was done using a one dimensional
engine modeling software. The influence of injection timing, exhaust system tuning,
compression ratio and combustion chamber geometry on engine performance was
investigated. Experimental results show that the engine is capable of propelling a
small motorcycle to a cruising speed of 60km/h with fuel consumption of 65km/l,
while the ideal performance of the engine which was simulated by the engine model
gives maximum cruising speed of 70km/h with mileage of 77km/l.
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