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单选题
The pressure of pilot air is usually （） than that of starting air.
A
higher
B
lower
C
low
D
high
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Forces other than damaging winds are also at work inside tornadoes (龙卷风) . Sometimes,as the wind passes a house, the walls and ceiling burst apart as if a bomb had gone off inside. This explosion is caused by the low air pressure at the center of a tornado.The pressure at the center of a tornado is usually 13 pounds per square inch. However,inside the house the air pressure is normal, about 15 pounds per square inch.The difference of 2 pounds per square inch between the inside and outside pressure may not seem like much. But suppose a tornado passes over a small building that measures 20 by 10 by feet. On each square inch of the building, there is 2 pounds of pressure from the insidethat is not balanced by air pressure outside the building. On the ceiling, that adds up to an unbalanced pressure of 57600 pounds. The pressure of the four walls adds up to 172800 pounds.If windows are open in the building, some of the inside air will rush out through them.This will balance the pressure inside and outside the building.But if the windows are shut tightly, the huge inside pressure may cause the building to burst.Unfortunately, heavy rain often occurs in the storms that later produce tornadoes,so people often shut their windows. This may cause far worse damage later.21、 What did the paragraph before this passage most probably discuss?A、 Measuring rainfall from a stormB、 The kinds of damage caused by explosionsC、 The powerful winds of tornadoes22、 Which of the following is the main topic of the passage?A、 How tornadoes can be preventedB、 When tornadoes usually occurC、 Why tornadoes cause so much damage23、 Tornadoes can destroy buildings because the()A、 force of a tornado increases the air pressure in a buildingB、 air pressure inside a tornado is less than the air pressure inside a buildingC、 air pressure at the center of a tornado is over 172000 pounds24、 What is the difference per square inch between the air pressure inside a building and the air pressure inside a tornado?A、 2 poundsB、 13 poundsC、 15 pounds25、 What would happen if the windows are shut tightly in the stormy weather?A、 Tornadoes may be formedB、 The house may be apartC、 There may not be any pressure inside the building
考题
When using a fuel with a higher than normal sulfur content in an auxiliary four stroke diesel engine, you mayA.maintain higher than normal jacket water temperatureB.change the lube oil more frequently than normalC.maintain a higher air-box temperature than normalD.maintain a higher air-box pressure than normal
考题
_______is usually driven by the engine camshaft and supplies pilot air to the cylinder air start valve.A.An air receiverB.An operating valveC.An automatic valveD.An air distributor
考题
The relative air pressure in the inlet manifold of a turbocharged diesel engine is usually______.A.greater than the average exhaust manifold pressureB.less than the average exhaust manifold pressureC.greater at the turbine wheel than at the impellerD.greater at reduced engine speed
考题
A low in a marine weather report is an air pressure system the pressure at the center of which is ______.A.the highest over the areaB.the lowest over the areaC.higher than 1013 HPAD.lower than 1013 HPA
考题
In international air cargo transportation， Specific Commodity Rates are usually lower than General Cargo Rates.
考题
单选题A marine diesel engine is started by（）A
supplying high pressure oil into a hydraulic motorB
supplying high temperature air into the cylinderC
supplying high pressure air into the cylinderD
electrical igniting
考题
单选题A more sophisticated pressure reducing valve incorporates a pilot valve which controls the fluid above the valve operating piston in response to downstream pressureThe bold and italic word “which” means （）.A
a pressure reducing valveB
a pilot valveC
an operating pistonD
downstream pressure
考题
单选题Which of the following statements is true concerning the overall efficiency of air compressors?（）A
High pressure compressors are more efficient than low pressure compressorsB
Mechanical efficiency divided by compressor efficiency will equal the overall efficiency of the compressor unitC
Two stage compressors are generally more efficient than single stage compressorsD
The volumetric efficiency is decreased in multistage compressors
考题
单选题On small, low pressure, air compressors, the cylinders are usually lubricated by the （）.A
splash methodB
mechanical force feed lubricatorsC
detached sump methodD
internal cooling passages in the crankshafts and connecting rods
考题
单选题An air mass is termed warm if（）.A
it is above 70°FB
the ground over which it moves is cooler than the airC
it originated in a high pressure areaD
it originated in a low pressure area
考题
单选题The relative air pressure in the inlet manifold of a turbocharged diesel engine is usually（）A
greater than the average exhaust manifold pressureB
less than the average exhaust manifold pressureC
greater at the turbine wheel than at the impellerD
greater at reduced engine speed
考题
单选题In the starting system, the automatic valve is controlled by（）, and the cylinder start valves are controlled by（）A
pilot air；pilot airB
handle；solenoidC
handle；pilot air coming through the distributorD
solenoid；pilot air coming through the distributor
考题
单选题Each cylinder has one starting valve which is usually opened by air pressure and closed by （）A
nuts and boltsB
new jointsC
spring forceD
sealing rings
考题
单选题The pressure of pilot air is usually （） than that of starting air.A
higherB
lowerC
lowD
high
考题
单选题An excessive charge of refrigerant in an air-cooled refrigeration system can cause （）.A
oil foaming in the compressorB
higher than normal suction and discharge pressures with a higher box temperatureC
higher than normal discharge pressure with a normal box temperatureD
the compressor to run continuously
考题
单选题（） is usually driven by the engine camshaft and supplies pilot air to the cylinder air start valve.A
An air receiverB
An operating valveC
An automatic valveD
An air distributor
考题
单选题Low pressure air is usually taken through （） or pressure regulators to a low pressure reservoir supplying a ring main through driers.A
globe valvesB
butterfly valvesC
gate valvesD
reducing valves
考题
单选题Cyclones that have warm sectors usually move（）.A
westerlyB
parallel to the isobars in the warm sectorC
toward the nearest high pressure areaD
faster than the accompanying cold front
考题
单选题（） supplies pilot air to control the cylinder air start valves.A
An air compressorB
An indicator cockC
An air distributorD
A safety valve
考题
判断题In international air cargo transportation， Specific Commodity Rates are usually lower than General Cargo Rates.A
对B
错
考题
单选题Which of the following statements concerning frontal movements is TRUE（）.A
The temperature rises after a cold front passesB
The barometric pressure rises when a warm front passesC
A cold front generally passes faster than a warm frontD
A warm front usually has more violent weather associated with it than a cold front
考题
单选题A crew member reports that the high-pressure alarm light of a low-pressure CO2 fixed fire extinguishing system is illuminated. The most probable cause of this condition would be that（）.A
an air leak has developed in the tankB
the tank cooling system has malfunctionedC
the pilot cylinder discharge valve is leakingD
an excessive amount of insulation has been installed on the tank and piping
考题
单选题The process of supplying a diesel engine cylinder with air at a pressure greater than atmospheric is called（）.A
engine displacementB
super-aspiratingC
air injectionD
supercharging
考题
单选题The pilot of the plane which flies faster than sound travels does not hear the thunderclaps because______.A
the sound of plane engine travels slower than the planeB
the frequency of the sound altersC
the passage does not mention itD
the pressure decreased when the plane flies in the air
考题
单选题When one cylinder has a lower compression pressure and higher exhaust gas temperature than any of the other engine cylinders, which of the conditions listed will indicated?（）A
Advanced ignitionB
Clogged air intakeC
Leaky exhaust valveD
High exhaust pressure
考题
单选题Excessively low air pressure occurring in the intercooler of a reciprocating air compressor is caused by（）.A
leaky discharge valves on the LP cylinderB
leaky discharge valves on the HP cylinderC
insufficient intercooler coolingD
low ambient air pressure
考题
单选题When using a fuel with a higher than normal sulfur content in an auxiliary diesel engine, you should（）A
maintain higher than normal jacket water temperatureB
change the lube oil more frequently than normalC
maintain a higher air-box temperature than normalD
maintain a higher air-box pressure than normal
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