(4) The figure below is a sketch diagram of a diesel engine.
- Identify the:
- type of diesel engine;
- number of its cylinders.
- Name the parts labelled U, V and W.
- (i) State one function of the part labelled U.
(ii) State two functions of the part labelled V.
- State two merits of the engine.
A high percentage of the candidates who attempted this question did not perform well. The required responses to the various parts of the question are:
(a) (i) it is a two-stroke diesel engine or a horizontally-opposed engine.
(ii) it has one cylinder.
(b) U - injector
V - piston
W - cylinder
(c) (i) One function of the part labelled U is to introduce fuel
under pressure into the highly compressed, heated and
turbulent charge of air in the combustion chamber.
(ii) The functions of the part labelled V are
- accommodates the rings;
- form a moveable gas light plunger in the cylinder;
- forms a guide and a bearing for the small end of the connecting rod;
- takes the side thrust caused by the angularity of the crankpin and connecting rod assembly;
- transmits the force caused by the expansion of gases in the cylinder through the connecting rod
to the crankshaft during the power stroke.
(iii) Merits of the engine are:
- it is very compact;
- it has very little vibration;
- it has better power-to-weight ratio.