问题：
[单选] Fuel injectors used in heavy fuel oil systems are usually provided with cooling to reduce（）.
cold corrosion of the nozzles。fuel viscosity for better atomization。carbon accumulation on the nozzles。fuel detonation in the cylinder。
问题：
[单选] A diesel engine cooling water system with a pH factor of 30 indicates a condition of （）.
slight acidity。slight alkalinity。excessive alkalinity。excessive acidity。
问题：
[单选] Which of the following statements concerning fire-tube boilers is correct?（）
Combustion gases flow through the tubes。Flames impinge on the tubes。Combustion occurs in the tubes。Water flows through the tube。
问题：
[单选] In a diesel engine cooling water system, a pH of 60 indicates a/an （）.
slightly acidic condition。slightly alkaline condition。overtreatment of water。neutral condition of water。
问题：
[单选] Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily by （）.
heat conduction into the injected fuel oil。heat conduction into the water jacket wall。water circulation through passages in the holder。fuel oil circulation through passages in the holder。
问题：
[单选] The pH value of water in a diesel engine closed cooling water system should be maintained between （）.
60 to75。80 to 95。100 to 115。120 to 135。
问题：
[单选] The purpose of the safety relief valves installed on an auxiliary boiler is to （）.
relieve excess fuel oil pressure during the “off” fire cycle。admit water to the dry pipe。throttle the forced draft fan output for proper combustion。reduce excess steam pressure in the boiler。
问题：
[单选] The most common contaminate of governor hydraulic fluid is （）.
moisture。dirt。acid。air。
问题：
[单选] Which of the substances listed is satisfactorily removed from the fuel by a centrifugal oil purifier?（）
Impurities。Lube oil。Gasoline。Diesel fuel。
问题：
[单选] A magnetic strainer is used in the diesel engine reduction gear oil system to remove small particles of（）.
water。babbitt。iron or steel。acid。
