Turbo chargers

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Turbo chargers

  1. 1. Turbo Chargers Class 2 Motor
  2. 2. Advantages Of Increased Scavenge Pressure:• Increased power for similar sized engines• Reduced SFOC : ‑ Mechanical, scavenge and thermal efficiencies are improved due to less cylinders, greater air supply and use of exhaust gases respectively.• Cheaper engine: ‑ Smaller for required output power.• Thermal load reduced: ‑ due to less exacting cylinder conditions Class 2 TurboChargers
  3. 3. Advantages Of Turbo-charger• Smaller and lighter than mechanical blower• Less moving parts• No drive required from engine• Can easily deliver the large quantities of air required• Increases thermal efficiency. Class 2 TurboChargers
  4. 4. Super-Charger Class 2 TurboChargers
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  11. 11. Radial ~ Axial TurbinesAdvantages Disadvantages• Larger pressure ratios • Difficult to cast with high obtainable temp materials• Greater blade tip velocity • If the turbine is damaged attainable then the whole rotor• Smaller requires replacement• Reduced mass of rotor produces better transient• Response to load changes Class 2 TurboChargers
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  26. 26. TURBO CHARGER BEARINGSOutside Bearing Location. Centrally Located Bearings.• Good accessibility to bearings for • With plain bearings on main engine lub oil system no FW overhaul cooling is required as bearings• Bearings in cooler region cooled by oil flow• Oil reservoirs can be in castings • Reduced shaft mass gives better• Greater overall turbine length transient response • Easier to manually clean turbine• Larger shaft diameter required to and impeller keep the longer shaft sufficiently • Larger diameter at bearing stiff, and this will increase rotor produces a larger friction loss mass • Shaft balance needs to be good as• Inlet passages of air/gas more whirl can be produced about restrictive. centre bearing unit • Bearing replacement a major job, requiring impeller and rotor removal Class 2 TurboChargers
  27. 27. TURBO CHARGER BEARINGSRolling contact bearings Plain bearings• Much lower friction than • Cheaper than roller bearings plain bearings • Less susceptible to dirt than• Need for dampening springs roller, main engine circ oil to reduce vibration damage often used of bearings, and to provide • Larger clearances required flexible mounts for bearings in turbine for axial thrust• Bearings can be damaged and radial tip clearances whilst static (brinelling) • Less prone to complete• Allows much smaller tip failure clearances to be used• Separate oil reservoir and pump usual. Class 2 TurboChargers
  28. 28. TURBO CHARGER VIBRATIONGradual increase in vibration Sudden increase in vibration could be due to: could be due to:• Worn damping springs in • Washing removing only part roller bearings of the rotor dirt• Ineffective mounting bolts • Blade damage from• Uneven fouling mechanical item striking• Failure of damping wire rotor blades • Bearing failureVibration after overhaul • Water striking rotor from could be due to: casing leak• Incomplete cleaning• Misalignment of rotating parts Class 2 TurboChargers
  29. 29. RUNNING WITH DAMAGE• Damaged Rotor Damaged Casing• lock rotor – pulse system lock both • Blank off cooling flow to affected ends as full gas flow must still pass casing through turbine • Remove covers and direct• Insert blanks – air side only for pulse scavenge air or air from vent fan system, both sides for constant into open casing to assist in pressure system. Blanks must have cooling orifice to allow air flow to • Monitor oil temperature and compressor for cooling and sealing, adjust load / rpm to ensure that to allow gas flow to prevent cold end temperature does not go above corrosion 90°C• Run at reduced load/revs using exhaust temps as load limiter (never above 500°C). The following is used as a guide by MAN B & W (constant pressure T/C)CUT OUT % POWER % M/E REVS1 of 1 T/C 15 531 of 2 T/C 50 701 of 3 T/C 66 87 Class 2 TurboChargers
  30. 30. TURBOCHARGER REDUCED AIR DELIVERY• Drop in ambient pressure• Reduction in engine load• Change in fuel quality• Change in engine timing• Fouling of air intake filter• Fouling of inducer/diffuser• Fouling of air side of charger air cooler• Fouling of exhaust ports and pipework• Fouling of protection grid• Fouling of nozzle ring, turbine blades• Fouling of exhaust gas boiler• Fouling of silencer• Mechanical damage to rotor• Casing or piping leaks Class 2 TurboChargers
  31. 31. Reasons For Turbo Charger Surging• Rapid Change In Load – Fluctuations due to rough weather, will cause variations in air mass flow rate due to change in engine speed.• Insufficient Supply Of Fuel – This can cause the engine speed to vary due to fuel starvation. Produces similar result as above.• Fault In Fuel System – Due to incorrect settings, timing of fuel pumps, or sticking fuel pump barrels, etc, result in different combustion conditions for individual cylinders. This can lead to variation in turbocharger speeds and air mass flow rates (pulse system).• Restriction Of Scavenge Passages – Blockage of air filters, will cause pressure ratio across compressor to increase and reduce airflow rates. Operating line of turbocharger moves closer to the surge line.• Narrowed Exhaust Gas Passages (After Turbo) – An extreme increase in resistance of the exhaust gas discharge passage will result in the reduction of airflow through the compressor.• Engine Operation At Overload – If the engine speed is maintained constant after fouling of the hull or damage to the propeller turbocharger speed will increase without an increase in air mass flow. Reduction in surge margin.• Failure Of Turbine Blade, Nozzle Or Diffuser – Fouling or damage to the above will result in increased resistance to gas flow and reduce airflow into the engine. Class 2 TurboChargers
  32. 32. PULSE SYSTEM CONSTANT PRESSUREAdvantages: SYSTEM• T/C responds rapidly to load Advantages: changes • Higher turbine efficiencies at• No auxiliary blowers needed for steady loads low loads • Simple pipework• High energy input to turbine • Good performance at high loadsDisadvantages: Disadvantages:• Exhaust pipework more complex • Requires auxiliary blowers to• Turbine efficiency reduces at assist at low loads higher loads due to operating with • Poor turbine response to load fluctuating gas flow changes• Pressure pulses can influence • Large space taken up by exhaust blow down from adjacent receiver cylinders• Turbocharging dictates engine timing Class 2 TurboChargers
  33. 33. Fouling can be due to: This fouling is identified by:2. The high temperatures of • rising scavenge air the inlet air, which will temperatures (1, 2, & 3) cause the salts in the sea • rising SW differential water to come out of pressure (1, 2 & 3) solution, form a hard scale • falling sea water and reducing heat transfer temperature differential (1)3. Debris in the water causing • rising sea water temperature a blockage at the inlet to differential (2 & 3) the tubes, reducing sea water flow4. Organisms (molluscs) growing in the tubes restricting coolant flow. Class 2 TurboChargers
  34. 34. SCAVENGE FIRESContributing factors. Signs of scavenge fire.• Inadequate draining of the • High temperature of exhaust scavenge spaces. and scavenge system.• Poor combustion. • Rough running of engine• Faulty injectors or fuel and possible surging of timing. turbochargers.• Worn liners. • Smoky exhaust.• Worn or damaged piston • Flames, smoke and sparks at rings. scavenge drains.• Exhaust system back • Failing engine speed. pressure.• Defective piston rod glands.• Too little or too much cylinder lubrication. Class 2 TurboChargers
  35. 35. SCAVENGE FIRESAvoidance. Action if Fire Occurs.• Regular draining of the • Two different approaches. scavenge spaces. • Slow down, shut fuel off• Correct cylinder lubrication affected unit, increase (spaces just damp). cylinder lubrication,• Regular maintenance of continue until fire burns out. cylinders, fuel injection (Sulzer recommendation) equipment, etc. • Cut off fuel to affected unit and slow down, ask bridge for permission to stop. Apply extinguishing medium. Allow to cool down then open up, clean and inspect for damage. (B&W ‑ also check tie rods) Class 2 TurboChargers
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  52. 52. Bearing Housing Casing Support End Nut BushingGearPump Separator Bi-Directional Damping Thrust Race Springs Class 2 TurboChargers

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