26-02-2013, 04:55 PM
Cooling Systems
Cooling.pdf (Size: 459.69 KB / Downloads: 89)
Consequence of engine running to hot:
• Pre-ignition
• Detonation
• Knock
– All result in very high pressure rise and possible damage to
engine
• Heat Fatigue of components
– Burnt Pistons
– Burnt Valves
• Failure of lubrication system
– Oil breakdown
– Oil film at cylinder destroyed at 200C
• Scoring of piston & sleeves
• Warping & fracture of components
Consequence of engine running to cold:
• Unnecessary Wear
• Poor Fuel Economy
– Incomplete Combustion
– Lower coolant Temperature
• More energy transferred out of cylinder
• Energy from is wasted & not available for work (Power)
• Promotes corrosive conditions in engine
– Water of combustion reacts with sulfur oxides in exhaust
• Forms acids
– Allows water & sludge to accumulate in crankcase
– Over time, fuel diluting the oil will accumulate
• Normally lighter volatile fuel will evaporate as temp. rises
Radiators
• RADIATOR
– Cellular type core
– Tubular, Tube and Fin type
• Pressurization
– Increase boiling pinot temperature
– 1oC for each 4 kPa increase in pressure
• Operation of Pressure control Radiator Cap
– Prevent coolant loss under normal temperatures
– Pressure relief into overflow chamber at high temp & pressure
– Vacuum valve when liquid cools, allow air into radiator
• Suck in liquid from overflow chamber
– Check cap for excessive pressure and vacuum
• WARNING: OPEN CAP ON HOT ENGINE OPEN SLOWLY, CARFULLY WITH LARGE THICK CLOTH
• FANS
– Suction Type
• Smaller, high speed vehicles
– Blower Type
• Slow moving, dirty environment
– Shrouds
• Improve airflow