Metering and injection timing controlled by individual pumps Nozzles contain a delivery valve which is actuated by the fuel oil pressure.
3. Distributor system In this system, the fuel is metered at a central point. A pump pressurizes, meters the fuel and times the injection. The fuel is then distributed to cylinders in correct firing order by cam operated poppet valves which open to admit fuel to the nozzles.
•It includes the oil pumps, oil tanks, filters, coolers and connecting pipes. •The purpose of the lubrication system is to reduce the wear of the engine moving parts •The various parts that require lubrication are piston , shafts , valves, cylinder walls and pistons, crank pins, big end and small end bearings etc. •The lubricant is cooled before recirculation. •Nearly 2.5% of heat of fuel is dissipated as heat, which is removed by the lubricating oil Lubrication system
The following are the important functions of a lubrication system •LUBRICATION: To keep parts sliding freely past each other, reducing friction and wear. •COOLING: To keep surfaces cool by taking away part of the heat caused by friction. •CLEANING: To keep the bearings and piston rings clean. •SEALING: To form a good seal B/W the piston rings and cylinder walls. •REDUCING NOISE: to reduce the noise of the engine by absorbing shocks.
The various lubricants used in engines are of three types: 1. Liquid Lubricants or Wet sump lubrication system. 2. Solid Lubricants or Dry sump lubrication system. 3. Semi-solid Lubricants or Mist lubrication system. Liquid oils lubricants are most commonly used
LIQUID LUBRICANTS OR WET SUMP LUBRICATION SYSTEM These systems employ a large capacity oil sump at the base of crank chamber, from which the oil is drawn by a low-pressure oil pump and delivered to various parts. Oil then gradually returns back to the sump after serving the purpose