Fishing Craft Technology

Unit 5 - Marine Engine and propulsion system

5.4. Systems of diesel Engines
The desired result, i.e., the development of useful power by the engine is achieved only when these parts function as a group only. Some parts have similar functions to perform or some parts assist other parts in carrying out their respective functions. In other words a diesel engine’s performance or operation can be easily understood if the different functions are grouped together into “Systems of operation”. These operating systems of a diesel engine can be broadly classified as:

• Frame System
• Energy Generating System
• Power Transmission System
• Intake Exhaust System
• Valve Mechanism System
• Fuel System
• Lubrication System
• Cooling System
• Starting System

Frame System:
The heaviest system of the diesel engine which supports all the vulnerable part is the frame system. Cylinder, crankcase, bed plate, main bearing etc., are some fo the important parts of this system. One of the main function of the frame system is to hold the dead load of all the components, the inertia load of the moving parts, the forces arising due to the combustion pressure etc., So utmost care has to be taken not only in designing but also in the material used for manufacturing these components which should have sufficient strength and stiffness to bear all the above said loads.

Energy generating system:
This system develops the energy. In a diesel energy is developed by the burning of fuel inside the combustion chamber. The lower part of the cylinder head, top part of the piston and the cylinder liner form parts of this system.

Power Transmission System:
The generated energy has to be transmitted outside the engine where it can be utilized. The power transmission system consists of piston pin, connecting rod, crankshaft, flywheel which performs this task. The parts of this system are all movable and also subjected to torsional and transverse forces. Hence they have to be abrasive resistant and able to withstand high torsional forces.

Intake and Exhaust System:
Suction and exhaust ports, manifolds, silencers etc., form the main parts of this system which is responsible for giving oxygen for combustion inside the cylinder as well as scavenge the unwanted gases outside the cylinder.

Valve Mechanism System:
Valve mechanism system works in conjunction with the intake and exhaust system. Controlling the timing, quantity of air admitted and expelling burnt gases out are performed by the intel and exhaust valves, cam, push rod, rocker arms and these parts constitutes this system.

Fuel system:
Like the heart of a human being fuel system can be termed as the heart of S for combustion. It has various parts which are explained in the detailed study.
Lubricating and Cooling and Starting System: These are auxiliary systems but for which the smooth starting and operation of the engine cannot be affected. Like the fuel system all these systems have a series of accessories as well as various methods of operation which are elaborately explained in the specific chapters.