Diesel Engine Components Lecture 7

Diesel Engine Components Main parts structural parts (stationary p.) running parts Systems

Structural parts PURPOSE: to support running parts to keep them in position and line to provide jackets and passages for cooling water, sumps, for lube oil to form protective casing for running parts to support auxiliaries (valves, camshaft, turbo blowers)

Running parts PURPOSE - to convert the power of combustion in the cylinders to mechanical work

Systems PURPOSE Supply of air Removal of exhaust Turbocharging Supply and injection of fuel Lubrication Cooling

Structural parts bedplate frame or column engine or cylinder block cylinder liners cylinder head or cover

Bedplate foundation on which the engine is built must be rigid enough to support the rest of the engine and hold the crankshaft which sits on the bearing housing in alignment with transverse girders at the same time, the bedplate has to be flexible enough to hog and sag with the foundation plate to which it is attached and which forms part of the ship structure

Bedplate

Bedplate

Frame load-carrying part of an engine it may include parts as the cylinder block,base, sump and end plates in two-stroke engines, frames are sometimes known as A-frames

Frame

Cylinder Block =engine block part of the engine frame that supports the engine cylinder liners, heads and crankshafts cylinder blocks for most large engines are made of castings and plates that are welded horizontally and vertically for strength and rigidity (stiffener) entablature = cylinder block which incorporates the scavenge air spaces in two-stroke engines

Cylinder block

The Sump The sump is the engine oil reservoir and it may also have a strainer fitted through which the oil must pass before entering the oil pump. The sump will be fitted with an oil drain attachment either for bottom discharge or out through the side for greater accessibility. The fitting of the gaskets between the sump and the block must be done with great care.

The Sump

The Sump

The Sump

Cylinder liner a bore in which an engine piston moves back and forth replaceable the material of the liner must withstand extreme heat and pressure developed within the combustion space at the top of the cylinder, and at the same time must permit the piston and its sealing rings to move with a minimum of friction

Cylinder liner Dry liner Wet liner

Cylinder liner

Cylinder liner

Cylinder liner

Cylinder liner

Cylinder head = cylinder cover the space at the combustion chamber top is formed and sealed by a cylinder head the cylinder head of a four-stroke engine houses intake and exhaust valves, the fuel injection valve, air starting vale, safety valve (the two-stroke engine lacks the intake valve)

Cylinder head

Vibration Isolator Vibration isolators are designed to absorb the forces of relatively minor vibrations that are common to operating diesel engines. Such vibrations are referred to as high frequency, low-amplitude vibrations, and they result from an unbalanced condition created by the motion of operating engine parts. Isolators can be equipped with coil springs or flexible pads to absorb the energy of engine vibrations.

Vibration Isolator

Gaskets Gaskets are used to provide a seal between two surfaces. The type of duty may vary greatly from the somewhat rough surfaces of water pipe flanges to the carefully ground faces of high pressure superheated steam pipes; from the valve cover on a cylinder head to the highly polished surfaces of hydraulic pump components. Each duty requires the correct type and thickness of material so it is important to understand the properties of the various gasket materials and the exact nature of the duty.

Major running parts piston piston rod crosshead connecting rod crankshaft & its bearings

Piston one of the major moving parts crown skirt must be designed to withstand extreme heat and combustion pressure made of cast iron or aluminium (to reduce weight)

Piston

Piston rod connects the piston with the crosshead

Piston rod

Piston rod

Crosshead the crosshead pin connects the piston rod to the connecting rod crosshead slippers are mounted on either side of the crosshead pin the slippers run up and down in the crosshead guides and prevent the connecting rod from moving sideways as the piston and rod reciprocate

Connecting rod it is fitted between the crosshead and the crankshaft it transmits the firing force, and together with the crankshaft converts the reciprocating motion to a rotary motion

Connecting rod

Crankshaft & its bearings one of the largest moving parts it consists of a series of cranks formed in a shaft converts reciprocating motion of the piston into rotary motion counterweights for balancing purposes

Crankshaft

Bearings

Crosshead Piston

Trunk Piston

Piston Ring Piston rings are manufactured and classified on the basis of function and usability. The primary usage of the piston ring is to seal the chamber (where the piston is moving), which can be a combustion chamber of a 2 stroke or a 4 stroke engine. Marine engines have three or more types of rings fitted on the circumference of the piston. The piston ring is an essential piston part, and its numbers and functionality differ depending on the type and capacity of the engine. In 2-stroke large engines, compression type piston rings are used to seal the combustion chamber and wiper rings are installed below them to wipe the deposits from the liner and distribute oil on the liner surface.

Piston Ring

Compression and Pressure Ring The compression rings provide sealing above the piston and prevent the gas leakage from the combustion side. The compression rings are located in the first grooves of the piston. However, this may differ according to the design of the engine. The primary function of these rings is to seal the combustion gases and transfer heat from the piston to the piston walls. The oil is controlled by shearing the layer of the oil left by oil ring, thus providing the top compression rings enough lubrication. Moreover, it also provides help to the top compression ring in sealing and heat transfer.

Wiper Ring The wiper ring, also called as Napier ring, or backup compression ring, are installed below the compression ring. Their main function is to clean the liner surface off the excess oil and to act as support back up ring on stopping any gas leakage further down which escaped the top compression ring. Most of the wiper rings have a taper angle face which is positioned toward the bottom to provide a wiping action as the piston moves toward the crankshaft.

Oil Control Ring The oil control rings control the amount of lubricating oil passing up or down the cylinder walls. These rings are also used to spread the oil evenly around the circumference of the liner. The oil is splashed onto the cylinder walls. These rings are also called scraper rings as they scrap the oil off the cylinder walls and send back to the crankcase. These rings do not allow oil to pass from the space between the face of the ring and the cylinder.

Oil Control Ring In the oil ring, holes or slots are cut into the radial center of the ring which allows the excess oil to flow back to the reservoir. Oil rings can be one piece or two pieces. To increase the contact pressure between the ring and the liner surface, the rings can have chamfered edges on either the outer sides of the lands or facing the combustion chamber to reduce the oil consumption through improved oil scraping from the bore. Two-piece oil control rings consist of a cast iron or profiled steel ring and a coil spring which is made from heat-resistant spring steel to act around the whole ring circumference for maintaining the pressure and contact.

Piston Ring

Piston Ring

Major running parts