As a high pressure system approaches，the barometer reading（）.

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  A . water level B . water flow C . temperature D . pressure

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• As the plunger moves up, the ports are closed and the fuel （） and delivered to the injector nozzle at very high pressure.

  A . being compressed B . to be pumped up C . is pressurized D . are built u

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• （）uses one or two high pressure pumps for all the cylinders with one more standby, while（）have a separate high-pressure pump for each cylinder.

  A . A common rail engine；conventional engines B . A conventional engine；common rail engines C . A marine diesel engine；most other engines D . A two-stroke engine；four-stroke engine

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• When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.

  A . increase the amount of cooling water to the condenser B . decrease the amount of cooling water to the condenser C . add more refrigerant to the system D . remove some refrigerant from the system

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• The weather is often（）in a high-pressure area.

  A . fine B . cloudy C . rainy D . windy

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• One cause of high head pressure occurring in a refrigeration system can be （）.

  A . insufficient cooling water flow to the condenser B . a low refrigerant charge in the system C . the liquid valve is open too much D . high evaporator superheat

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• The atmosphere in the vicinity of a high pressure area is called a(n)（）.

  A . anticyclone B . cold front C . occluded front D . cyclone

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• The device used for low-pressure control and high-pressure cutout on a compressor is called （）.

  A . cutout B . controller switch C . pressure controller D . cutout switch

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• Which of the following may cause that the compressor cuts off on high pressure cutout in a refrigeration plant? （） (1) faulty condensing (2) too few refrigerant (3) high discharge pressure

  A . any of (1) and (3) B . any of (1) and (2) C . any of (2) and (3) D . any of (1), (2) and (3)

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• The compressor in an air-cooled condensing refrigeration system is short cycling on the high pressure cutout switch（）

  A . system is overcharged with refrigerant B . system is low on refrigerant C . discharge valves are leaking excessively D . discharge valves are leaking slightly

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• Compared to a low pressure system，generally the air in a high is（）.

  A . warmer，less dense，and less stable B . cool，more dense，and drier C . muggy and cloudy D . extremely moist with high relative humidity

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• The high-pressure fuel opens the fuel valve and is sprayed into the cylinder in tiny droplets known as （）.

  A . injection B . penetration C . atomization D . compressio

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• Two well-developed high pressure areas may be separated by a（）.

  A . Hill of low pressure B . Trough of low pressure C . Valley of low pressure D . Ridge of low pressure

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• 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 tank B . the tank cooling system has malfunctioned C . the pilot cylinder discharge valve is leaking D . an excessive amount of insulation has been installed on the tank and piping

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• In a compression refrigeration plant the refrigerant is under low pressure in the （） and under high pressure in the （）.

  A . compressor；condenser B . condenser；evaporator C . throttle valve；evaporator D . evaporator；condenser

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• A tropical cyclone has recurved and entered temperate latitudes. In the Northern Hemisphere when a large high pressure system lies north of the storm，what situation may occur?（）

  A . The low may suddenly deepen，and the cyclone intensify and pick up speed B . The left semicircle may become the dangerous semicircle C . The low and the high may merge and cancel out the weather characteristics of each D . The high may force the cyclone to reverse its track

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• When normal operating pressure is applied to the hydraulic oil used in a high-pressure system, the oil （）.

  A . viscosity will decrease B . volume will increase C . volume will decrease D . pour point will be reduced

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• The replacement piping for diesel engine high pressure fuel systems must be the same length and diameter as the original piping to （）.

  A . avoid unnecessary pints inventory B . keep torsional vibration constant C . use existing supports and braces D . maintain specified injection characteristic

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• One remedy for a high firing pressure, in addition to a high exhaust temperature in one cylinder of a diesel engine, is to （）

  A . increase scavenge air pressure B . reduce fuel booster pump pressure C . adjust the fuel rack D . retard fuel injector timing

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• 207. The greater the pressure difference between a high and a low pressure center, the ______ .

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• such as_______ and high blood pressure.

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• You blood pressure is a little high. 译成：

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• When the relief valve is used as a constant pressure valve, it is connected to the outlet of the hydraulic pump to ensure that the outlet pressure of the hydraulic system (pump) is constant.

  A:正确; B:错误

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• The pressure range between the system cut in and cut out pressures in a refrigeration unit is known as_______.

  A.opposing operational drag B.pressure distribution C.differential D.system purge

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