单选题Sludge may form in the crankcase of an air conditioning compressor as a result of ().Abubbling refrigerantBoverheating and oxidationClowered operating temperaturesDreducing the cloud or flash point

单选题
Sludge may form in the crankcase of an air conditioning compressor as a result of ().
A

bubbling refrigerant

B

overheating and oxidation

C

lowered operating temperatures

D

reducing the cloud or flash point


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Crankcase explosions in propulsion diesel engines result from ____.A.the splashing of lubrication oil by the crankshaftB.the dilution of crankcase oil with particles of combustionC.broken fuel lines spraying oil on the crankcaseD.the ignition of unburned fuel and air in the crankcase

第二组Under normal operation, some lubrication oil mist may be discharged from the air compressor to the air start system. This oil may be from excess compressor cylinder lubrication, from faulty oil scraper rings, or may even be suspended oil vapor contaminating the engine room atmosphere and drawn in at the compressor suction. Oil discharge is kept to a minimum by draining the after cooler, air receiver and starting system. If small quantities of lubrication oil do get passed into the starting air system, they will deposit as thin moist film over internal pipe surfaces but are not readily combustible. If a cylinder non-return valve leak while the engine is in operation, some hot gas, possibly with unburned fuel and cylinder lubrication oil, may be blown through the valve to the adjacent air manifold. With further heating from the leaky valve, this, together with the already deposited oil film, will carbonize and form. incandescent carbon. If starting air is applied to the system while still hot, the high pressure air coming into contact with the burning carbon may cause an explosion. Such an explosion will cause a flame to pass back through the air start pipe system, evaporating the deposited oil film and igniting it in the presence of air. Very high velocities and shockwaves are generated which may rupture pipes and fittings.Alternatively, if excessive oil has entered the air start system, a mixture of air and oil droplets may be discharged through the open cylinder non-return valve during starting. This spray may ignite due to high temperatures in the cylinder, causing a flame through the still open valve to the air manifold.To prevent an explosion, air start valves must be correctly maintained and lubricated to ensure correct timing and free movement with positive closing. Oil in the system must be kept to a minimum, pipe lines must be drained and cleaned internally when necessary and oil discharge from air compressors must be kept to a minimum by good maintenance.The passage is mainly aboutA.crankcase explosionB.scavenge box fireC.starting air pipeD.the danger of explosion in the starting air system

Sludge may be formed in the oil in the crankcase of a reciprocating air conditioning compressor as a result of ______.A.refrigerant bubbles in the lube oilB.refrigerant reducing the lube oil viscosityC.oxidation(氧化) of the lube oil from overheatingD.reducing the floc or cloud point of the oil

In an air conditioning system, moisture is removed from the air by ______.A.filtersB.separatorsC.ducted trapsD.dehumidifiers

Sludge may form in the crankcase of an air conditioning compressor as a result of ______.A.bubbling refrigerantB.overheating and oxidationC.lowered operating temperaturesD.reducing the cloud or floc point

According to this passage, which of the following statements is true?A.In boiler and machinery spaces, there is the air conditioning.B.In the boiler rooms the requirement of air volume should meet 25-50% of combustion requirement.C.To maintain the comfort zone in the separate control room the air conditioning plant should be fitted.D.The comfort conditions can be maintained in the engine room all the time.

Due to the large amount of heat picked up by the air in boiler and engine rooms, it would be impracticable to maintain ambient conditions within the comfort zone by air conditioning or any other means. The normal practice is to provide copious mechanical ventilation; in boiler rooms, the quantity is equated to the combustion requirements, while in a motor ship engine room the supply may be 25-50% in excess of the requirements of the engines.The axial flow fan is particularly suited to handle these large air volumes at the moderate pressures required, while of course the “straight-through” flow feature places it at an advantage over the centrifugal fan.The increasing adoption of automation, with the provision of a separate control room makes less significant the fact that comfort conditions cannot be maintained in the engine room all the time. Which of the following devices should be taken to maintain ambient conditions of the boiler and machinery space?A.air compressorB.air coolerC.air-conditioning plantD.mechanical ventilation plant

Would you like the air-conditioning on?的意思是:()?

单选题Due to the large amount of heat picked up by the air in boiler and engine rooms, it would be () to maintain ambient conditions within the comfort zone by air conditioning.ApossibleBnecessaryCpracticableDimpracticable

单选题If plastic film insulation becomes damaged in air conditioning system, () may form within the film.AevaporationBcondensationCliquefiesDvaporization

单选题In an air conditioning system, moisture is removed from the air by()AfilersBseparatorsCducted trapsDdehumidifiers

单选题A re-heater in an air conditioning system functions to ().Acontrol inlet air temperatureBcontrol inlet air volumeCmaintain relative humidity at 15%Drestore conditioned air temperature to a comfortable level

单选题A re-heater, as used in an air conditioning system, is designed to control the ()Achilled water temperatureBdew point temperatureCprimary air temperatureDdry bulb temperature

单选题What function is provided by the crankcase ventilation system on some diesel engines?()AIncreases the sludge forming tendency of lube oilBPrevents the accumulation of combustible gasesCImproves lube oil coolingDImproves cold weather starting

单选题Air conditioning is the process of treating air to control () its temperature, humidity, cleanliness and distribution to meet the comfort requirements of the occupants of the conditioned space.AinstantaneousBinstantaneouslyCsimultaneousDsimultaneously

单选题In reference to air conditioning, when air attains the maximum amount of moisture it can hold at a specific temperature, it is said to be ().AsuperheatedBsaturatedCcondensedDconvected

单选题Most air conditioning units have () for adjusting the ratio of recirculated fresh airCare must be taken not to reduce the fresh air so that stuffiness or smells arise.Acatch platesBdampersCregulating valvesDfans

单选题Crankcase explosions in propulsion diesel result from()Athe splashing of lubrication oil by the crankshaftBthe dilution of crankcase oil with particles of combustionCbroken fuel lines spraying oil on the crankcaseDthe ignition of unburned fuel and air in the crankcase

单选题With ducted air conditioning systems, the modern tendency is to use()Acentral air conditioning systemBhigh velocity systemClow velocity systemDsingle duct system

单选题If a crankcase explosion occurs in a diesel engine, you should stop the engine and()Aimmediately open all crankcase relief portsBincrease crankcase exhauster speed to draw cool air into the engineCallow the engine to cool naturallyDincrease crank case scavenge air to remove unburned gases

单选题Sludge may form in the lubricating oil crankcase of a reciprocating air conditioning compressor as a result of ().Awax precipitation in the lube oilBcontamination by dust, scale, or moistureCrefrigerant bubbles in the lube oilDrefrigerant reducing the lube oil viscosity

单选题To prevent the unnecessary loading of an air conditioning system while maintaining the designed dry bulb temperature and relative humidity in an air conditioning system, you should ()Aadmit only enough fresh outside air to provide proper ventilationBreduce the air reheating system loadClower the compressor head pressureDoperate the purge recovery unit continuously

单选题When fuel enters the crankcase of a diesel engine, it ()Adilutes the lube oil and reduces its viscosityBforms sulfuric acid in the lube oilCcauses pitting and failure of the bearingsDcauses sludge deposits on valve stems

单选题Sludge may be formed in the oil in the crankcase of a reciprocating air conditioning compressor as a result of ()Arefrigerant bubbles in the lube oilBrefrigerant reducing the lube oil viscosityCoxidation of the lube oil from overheatingDreducing the floc or cloud point of the oil

单选题Routine maintenance on a Central Control Room hermetically sealed air conditioning unit should include ()Achanging the air filterBrecharging the systemCchanging compressor lubricantDrenewing container vacuum

单选题The main distribution duct in an air conditioning system which contains the cooling coils and filters is called the()AmanifoldBcondenserCchamberDplenum

单选题The quantity of cooled air delivered by an air conditioning unit should () the sum of the quantity of air re-circulated to the unit and the quantity mechanically exhausted.AbalanceBnot balanceCbe more thanDbe less than