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Drive System Design Principles
Transcript of Drive System Design Principles
2. Concept Design and drive selection stage
3. Boundary Conditions
4. 2 Stroke Reversible Direct Coupled Diesel Engine
5. 4 Stroke Diesel, with Gear and CPP
6. Diesel Electric Propulsion
7. Linear Electric Propulsion
8. Azipod Electric Drive
9. Nuclear Propulsion
10.Choice of Drive, MCA
Containers have been most efficient, fast, safer and popular way of cargo transport. Though highest TEU is 18000 as Mearsk Lines is coming up with Triple E sires, average size dominates the industry. Main reason being average size containers don't face loss of operating cost due cargo deficit. Also It can be operated in panamax or suez and in European River Channels, making it possible to move it to different business route.
Containers of world consume more Fuel compared to any other vessel, reason being high speed requirement and increasing numbers everyday. Therefore improvement in drive system of containers have been a major concern.
Team : Manish Shrivastava(4321227)
Farzaneh Zahiri Esfahani (4048237)
This presentation seeks to look into Drive system possibilities for average size container ship which dominate the shipping trade.
Boundary Conditions and Regulations
Crash Stop : 15 L (L-length of ship)
Turning Ability: Distance traveled before 10 degree course Change Should be less than 2.5 L.
Start Up Time: Time required to put drive into operation is very essential wrt safety and commerce.
Pollution Control Requirement:
NOx: 9.8-17 g/kWh
SOx: Sulphur level 4.5% Worldwide, and 1.5% in Emission Control Zone.
Specific Criterias of Marpol Annex VI should be complied during Design and Operation of Drive
Marine Propulsion drive should have very high reliability for average 20 year age.
Should be moderate
Noise: Moderate Noise allowed.
Response to Load Variation: A better drive should allow quick load changes.
Vibration should be minimum.
Downtime: Should be very less in event of any problem It should allow operators to put system back within short time.
Minimum Weight and size preferable. Should not occupy too much space as it will Reduce Cargo Capacity. Location allocated for Drive components inside hull is also important before considering drive.
Failure of a part of system should not hamper complete ability of ship to maneuver and control.
Drive System should put minimum hazard to operators and crew on board.
Fuel should be available at Every Port. Adaptability to Cheap High Viscosity HFO: VVI for commerce. Should be able to adapt Future Market & Industry Conditions and Regulations of IMO.
Drive should be able to be maintained at mid sea w/o shore assistance. Critical Spares should be available in short time when required. Industry Experience is important. Those Drives which have been used widely, have much better information about their working life and also give better insight into safety and maintainability.
2 Stroke Reversible Direct Coupled Diesel Engine
: This Drive gets Powered by 2 stroke Crosshead Type Compression Ignition Reversible Diesel Engine, Thrust is Transferred from Propeller shaft to Hull By means of Thrust Block. Engine completes one combustion cycle in 1 Revolution of Crank Shaft. There is no gear box in between, so propeller rpm is same as Engine RPM. For 30000 KW thrust, Power Developed by Engine should be around 55000 Kw. For RPM of 90-100 Torque developed would be about 5000 KNm. Slow speed of Large Crosshead Engines Minimizes sleep loss.
Also It can burn Heaviest Fuel available
in market. Load is controlled by Governor.
4 Stroke Diesel, with Gear and CPP
Efficiency of 2 stroke Engine is normally
40% in sea going conditions,
Specific Fuel consumption 200 gm/kWh.
4 Stroke Marine Diesel too follows Dual Thermodynamic Cycle (During Combustion both Pressure and Volume increase). 2 Revolutions of Engine crank shaft completes 1 power cycle.
Compared to 2 stroke Engines, size of 4 stroke engine is relatively small, Trunk design of Crankcase and cylinder limits swept volume and hence to produce More energy RPM has to be increased (Power=K*P*L*A*N).
Higher RPMs which are possible with 4 stroke make gearing necessary. Propeller slip increases at high RPM, So gears are used to control propeller shaft rpm to low values. CPP pitch control system enables Engine to run at constant RPM, while by changing blade direction with respect to flow (by means of hydraulic control) propeller thrust can be changed.
Diesel Electric Propulsion
With 4 stroke Engines It is possible to gear 2 or More Engines to produce same power as Large Bore 2 Stroke main Engine, Advantage is that It occupies much less space and provides redundancy in case one of them is under some maintenance. Or Two Engines can be coupled to two twin screw cpp propellers. With present technology it is possible to run it on heavy fuel all the time, when in stop mode hot fuel circulates to Injection system and back to header chamber. Also when CPP and gear system is used, it is possible to run engine on 75% RPM always, while controlling the load by CPP and gear, I helps avoiding slow steaming which leads to incomplete combustion and several problems to engine and system. A Typical Wartsila Medium speed Engine which produces 50,000 Kw, will have RPM of around 800 RPM, Torque developed at this RPM would be maximum 600 k Nm. which requires much thinner diameter propeller shaft.
AZIPOD electric propulsion
Marine Diesel Engines By C C Pounders
Practical Marine Electrical Technology By D T Hall
Reeds Marine Engineering Series
Marine Diesel Engines, D.K.Sanyal
Drive and Propulsion Efficiency
Electric Propulsion of Ship requires Electric Motors to drive propeller and Generator sets to supply the electric power, It eliminates the need for need for long Propeller shaft and positioning of Diesel Engines at Aft, Diesels can be located conveniently and with help of convertors and High Voltage transformers electric power can be provided to motor located near stern tube. Same set of powergens can be used for both ship service and propulsion.
Linear Electric Propulsion
Basic concept behind this propulsion is application of direct electromagnetic force on water to produce thrust. With advancement in superconductivity large currents can be carried in thin conductors which can create very large magnetic fields, These magnetic fields will ionize the water and induce current, These currents of ionized water will feel large force due to High magnetic field. F= K x Magnetic Field Flux x Current. Direct force applies on the water which gives thrust for ship propulsion.
A large DC current is driven between metal plates mounted in an open tube below the hull, Sea water acts as conductor for this current. Coils of wire at superconducting temperature are (-269 Degree C cooled by helium) are fitted around propulsion tube to create a magnetic field 90 Degree to the current flow. Combination of current and magnetic field produces a direct mechanical force on the conductor (water) to create a linear thrust without need for rotating propeller. By diverting port and starboard thrust tubes into short sections along the hull, the size and location of thrust can be distributed so that conventional steering and side thrusters are not required.
Multi Criteria Analysis
A sustained nuclear reaction in the reactor produces heat that is used to boil water. The resulting steam spins a turbine. The turbine shaft may be coupled through a gearbox speed reducer to the ship's propeller, or in a turbo-electric drive system may run a generator that supplies electric power to motors connected to the propellers. Nuclear power plant operate a vessel for several years without refuelling. Although the cost of manufacturing nuclear fuel elements is high, the overall cost of operations can be lower than the costs of operating a similar fossil fuel powered ship. Like sailing ships, nuclear vessels are independent of the vagaries of procurement of fuel at every port. The laborious and costly process of loading and burning fuel is largely eliminated for most of the vessel's operating life.
Because of its high power density and the elimination of the need for large fuel bunkers
: System uses a pair of High Voltage, High Efficiency synchronous motors, with fixed pitch propellers driven at variable speed by frequency control from electronic convertors. Prime movers are constant speed diesel engines driving ac generators to give fixed output frequency and voltage.
E=Constant x RPM x Flux of Magnetic Field
Frequency=N*Number of Poles on Rotor
When Flux of magnetic field passing a circuit Changes an EMF is induced in it.
Working Principle of AC Alternator
When 3 Phase Electric current is supplied to startor it produces rotating magnetic field with Ns=F/p
The rotor has a set of d.c. excitation magnetic poles which locks in with stator rotating flux. Torque = Force* radius
Nuclear propulsion uses energy liberated from fission of Uranium to propel the ship.
When EMF is applied to 3 phase stator coils, it Produces magnetic field whose magnitude is given by
Biot Savart Law
of Electromagnetic Induction: When a wire loop has changes in magnetic field flux, EMF is induced whose magintude is proportional to rate of change of flux.
This induced EMF makes current flow in wire loop whose direction is determined by Lenz law,
A current carrying conductor in magnetic field experiences force (
). Direction of force is perpendicular to current and magnetic field and is given by Fleming Right Hand Rule.
Basic Theory behind Motor Working
In azipod propulsion complete set of synchronous motor is put inside a rotating pod, this works for both propulsion and eliminates need for steering and stern thrusters and gives extra cargo space. Reduced noise inside hull and minimal vibration as structure is outside hull.
Synchronous motor gives much better speed control and lesser losses compared to Induction motor.
Power Drive Selection Flowpath
Azipod Propulsion Electric Drive
We Recommend 2 Stroke Direct Coupled Diesel Engine Drive