MARPOW

Diesel Engine

Diesel Engine

• an engine that uses compression ignition.

• To some it may be an engine that uses heavy fuel oil.

• To others an engine that does not use spark ignition.

Rudolf Diesel

However the original cycle proposed by ________________ in 1892 was a constant temperature cycle (a cycle based on the Carnot theory) that would require much higher compression than what is needed for compression ignition.

compress

Diesel's idea was to __________________ the air so tightly that the temperature of the air would exceed that of combustion.

Four-stroke diesel engine

• This engine has four strokes in one combustion cycle.

• Almost all automobiles and large motorcycles use_________________.

Intake-stroke

_______________ where the air/fuel mixture is taken into the combustion chamber.

Compression stroke

_____________________where the gases are squeezed by the momentum of the piston

Power-stroke

____________________ where the spark plug fires and the gases are ignited.

Exhaust stroke

____________________ where the piston comes back up, pushing the spent gases out of the combustion chamber.

Two-stroke diesel engine

• combines the intake and exhaust strokes into the power stroke from the four-stroke engine which requires only one stroke each of up and down to complete the cycle.

• have fewer moving parts and shorter cycle which make them cheaper and able to run at high RPM.

• Unfortunately, they also provide a  lot more pollution because the lubricating oil gets mixed in with the fuel and air and gets burned and expelled.

Cylinder Block

• is a part of an engine in which combustion of an oil takes place

Cylinder Head

•  is fitted on top of a cylinder block and its function is to seal the working end of a cylinder  and not to permit entry and exit of gases on cover head valves of an engine.

Crankshaft

• it is a shaft which transmits the power developed by an engine to the various parts of the vehicle.

Connecting Rod

• connects piston to the cannon shaft and transmits the motion and thrust of piston to crank shaft

Camshaft

• controls the opening and closing of valve at proper timimg.

• It is placed at the top of bottom cylinder

Valve

• are used to control the inlet and exhaust of the internal combustion cylinder

Piston

• is placed in the cylinder and transmits thrust to the connecting rod

• It transmits power to the crankshaft

Gudgeon Pins

• these are hardened steel parallel spindles fitted through the piston bosses and the end bushes or eyes to allow the connecting rods to swivel it

Piston Ring

• it provides the good sealing fit and less friction resistance between piston and cylinder

Spark Plug

• it is used in spark ignition engine, It is fitted on the cylinder head and used to ignite the air fuel mixture inside the cylinder at the end of each compression stroke

Injector

• usually used in compression ignition engine, It sprays the fuel into combustion chamber at the end of compression stroke

Manifold

• its main function is to supply the air fuel mixture and collects the exhaust gases equally from all cylinders.

Crank Case

• it serves as the lubricating system.

Gas Turbines

• also called combustion turbine is a type of continuous combustion engine.

• are used to power aircraft, trains ships, electrical generators, pumps gas compressors and tanks.

Bryton cycle

• The basic operation of the gas turbine is the ______________ with air as the working fluid. Fresh atmospheric air flows through the compressor that brings it to a higher pressure. Energy is then added by spraying fuel into the air and igniting it so the combustion generates a higher temperature flow. This enters a turbine where it expands down to the exhaust pressure producing a shaft work output in the process. The turbine shaft work is used to drive the compressor.

petrol, natural gas, propane, diesel, kerosene, E85 biodiesel, and biogas

• Gas turbines accept most commercial fuel such as petrol, natural gas, propane, diesel and kerosene as well as renewable fuel such as E85 biodiesel and biogas

Steam Turbine

•  is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft.

Sir Charles Patron

• Its modern manifestation (Steam turbine) was invented by _________________ in 1884.

Blades and Nozzles

2 types of Turbine Blase

Blades

• move entirely due to the impact of steam on them and their profiles do not converge.

• This results in a steam velocity drop and essentially no pressure drop as steam moves through the _____________.

• A turbine composed of ___________ alternating with fixed nozzles is called an impulse turbine, Curtis turbine, Rateau turbine or Brown-Curtis turbine.

Nozzles

• appear similar to blades but their profiles converge near the exit.

• This results in a steam pressure drop and velocity increases as steam moves through ______________.

• ____________ move due to both the impact of steam on them and the reaction due to the high velocity steam at the exit.

• A turbine composed of moving ________ is called a reaction turbine or Parson’s turbine.

Propeller

• a type of fan that transmits power by converting rotational motion into thrust.

air foil- shaped blade

• A pressure difference is produced between the forward and the rear surfaces of the___________________ and a fluid (such as air or water) is accelerated behind the blade.

Propeller Shaft

• also known as a drive shaft or Cardan shaft is a mechanical component for transmitting torque and rotation usually used to connect other components of a drive train that cannot the connected directly because of distance or the need to allow for relative movement between them.

• It carries the power from the engine, clutch and transmission unit to the driving wheels of vehicle through the fixed drive and different unit.

Fixed Pitch Propeller (FPP)

• consists of fixed blades. This means that the position of blades cannot be changed.

• the power generated  by the engine and the propulsive forces produced by the propeller cannot be controlled.

• This leads to  high amount of power wastage and increased stresses on the propeller.

Controllable or Variable Pitch Propeller (CPP)

• can move its blades in the desired position by changing the pitch of the blade.

• the propeller rotates in only one direction unlike FPP.

• there is no need of a reverse clutch, which is an integral part of FPP for producing reverse thrust, in case the ship needs braking or reversing.  

Advantages of CPP

• A CPP can operate with minimum or negligible loss in power.

• This helps to improve the maneuverability of the vessel.

• The direction from ahead to astern can be changed in a matter of few minutes or even seconds depending on the condition of the load of the ship.

• This not only helps to absorb all the power generated by the engine but also helps to prevent wastage of fuel.

• In some CPP the direction of the thrusts can be seconds.

• A CPP can also be connected to a shaft generator and can be used for a wide range of rotational speed.

• A shaft generator can supply power on ship till the main engine is running. CPP can be used to maintain the frequency of the generator as the engine moves in a constant rpm. In case during the navigation time additional energy is needed, an auxiliary generator can be used to provide additional power to the shaft generator. This is mainly used during maneuvering.

Disadvantages of CPP

• CPP is that it is highly complex system. It is vulnerable due to numerous hydraulic components and sealing rings. As the sealing rings are outside the ship, damage of a single sealing ring can result in oil pollution. As the system is complex, repair and maintenance is difficult.