Marine diesel engines have a number of parts that require us to have a fully understanding of how they work to help us deal with failures and malfunctions.Air coolers are common engine parts in marine engines which will ensure an effective oil & air combustion inside the engine cylinders.
Why diesel engines need air coolers?
It is well known that for the happening of combustion there will need the oil and air mixture,air is drawn into the engine and will be mixed with the oil mist,diesel engine has very high compression ratio than gasoline engines thus much more air will be needed in order to keep the oil air ratio,which is why air coolers are employed in large marine diesel engines through which the air is cooled down to the operating temperature after it pass through turbo-charger.A diesel engine turbo-charger is a device fitted on the engine for the purpose of providing engine with compressed air by using the energy of exhaust gas.When the air is passing through the turbocharger,both temperature and its density will be growing up,the higher the density the much more mass the oxygen,it is absolutely what the engine needed,however,the higher the temperature of charged air is,the much higher temperature the exhaust gas will be,that is what we do not expect,which will be contributing to the reduce of engine longevity.In order to reduce the charged air temperature the charge air cooler is thus be introduced to the engines.
Normally,there has a higher ambient temperature in engine room than in other places of ship,the temperature of charged air would likely increase due to the higher ambient air temperature,so the charge air cooler is designed as close to the air intake manifold as possible,which will make sure that the temperature of charged air will not increase significantly.
The following pictures present you with a typical charge air cooler fitted on a marine diesel engine.
As the pictures show that this engine is installed with two charge air coolers (Bad photographing,not enough space for me to take full back view photo)on both side of the engine since there are two turbochargers,the pipes go through the charge air coolers are the low temperature fresh water,this is the low temperature part of cooling water system which is different than the jacket water cooling system.The fresh water-out side is fitted with a thermostat valve which is used to keep the temperature of feed water at the set point to ensure the charged air has the same temperature before it goes into the engine.
Charge air cooler is always used for the cooling of charged air?
That depends on the temperature of charged air the engine required,charged air cooler function to maintain a consistent charged air temperature,it will warm up the air if it is too cold whereas it will cool down the air when it is too hot,but in most cases,after the air has been compressed by the turbocharger,the temperature will always be higher than the preset value.
No comments:
Post a Comment