On small, low pressure, air compressors, the cylinders are usually lubricated by the （）.

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• The purpose of the low pressure cut-out switch is to （）.

  A . maintain liquid refrigerant at the suction of the compressor B . maintain a preset suction pressure to the compressor C . start and stop the compressor at preset operating pressures D . operate at minimum efficiency

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• If a refrigeration compressor were short cycling on the low pressure cutout switch, the probable cause for this might be the （）.

  A . system was overcharged with refrigerant B . high pressure switch was improperly adjusted C . expansion valve strainers were fouled D . suction valves were leaking slightly

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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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• In general, （） is suitable for delivering small quantities at high pressure.

  A . reciprocating pump B . gear pump C . centrifugal pump D . vane pum

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• The refrigeration system low pressure cutout switch is actuated by （）.

  A . an electric system manager B . a sensing bulb at the tail coil of the evaporator C . pressure changes in the suction line D . failure of the king solenoid valve

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• （） are more suitable for large quantities at low pressure.

  A . Reciprocating pumps B . Rotary pumps C . Centrifugal pumps D . Gear pum

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• P5板上FLT CONTROL LOW PRESSURE表明（）

  A . 仅说明相应液压系统到副翼、升降舵、方向舵相应的液压出现低压 B . 仅说明相应液压系统到方向舵的油路出现低压。将电门放置在STAND BY RUD位时，当备用方向舵关断活门打开时灯灭 C . 相应液压系统到副翼、升降舵、方向舵相应的液压出现低压。将电门放置在STAND BY RUD位时，当备用方向舵关断活门打开时灯灭 D . 相应液压系统到副翼、升降舵、方向舵相应的液压出现低压。将电门放置在STAND BY RUD位时，当备用方向舵关断活门打开时灯亮

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• APU工作期间，“APU LOW OIL PRESSURE”灯亮：（）.

  A . A、要求机组关掉APU B . B、可以继续使用APU，但不能使用APU引气 C . C、要求机组将APU电门放到”OFF”位后，再放到”START”位1-2秒松手 D . D、APU自动关车

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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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• APU LOW OIL PRESSURE”灯何时亮是正常的（）？

  A . A、APU电门放在”ON”位而APU还没有工作时 B . B、APU关车后 C . C、APU起动期间滑油压力上升到正常之前 D . D、任何时候亮都是不正常的

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• Low compression pressure in a diesel engine is caused by（）

  A . low water in the expansion tank B . improperly seated valves C . low fuel oil pressure D . worn or broken cylinder liner sealing ring

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• In general, （） is suitable for delivering small quantifies at high pressure.

  A . reciprocating pump B . gear pump C . centrifugal pump D . vane pum

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• Low compressor head pressure in a refrigeration system can be caused by（）.

  A . insufficient condenser cooling water B . excessive condenser cooling water C . air in the refrigeration system D . excessive refrigerant in the system

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• Leaky exhaust valve will result in which of the following?（） (1) high exhaust temperature; (2) low compression pressure; (3) low firing pressure.

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

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• Broken valve strips in an operating low pressure, air compressor will cause （）.

  A、an immediate crankcase explosion B、oil contamination in the compressed air C、a decrease in compressor capacity D、no immediate loss of the compressed air capacity

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• Low compression pressure in a diesel engine can be caused by（）

  A . improperly seating intake valves B . leaking cylinder liner seal rings C . late fuel injection timing D . carbon deposits on the pisto

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• If a refrigeration crankcase compressor were short cycling on the low pressure cutout switch, the cause might be that the （）.

  A . system was overcharged with refrigerant B . system was low on refrigerant C . suction valves were leaking slightly D . relief valve was leaking slightly

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• The purpose of the refrigeration system low pressure cutout switch is to （）

  A . protect the compressor from liquid flood back B . protect the compressor from low discharge pressure C . start and stop the compressor upon system demand D . start the compressor after a drop in the evaporator pressure

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• High cylinder firing pressure, accompanied by low exhaust temperature, can result from （）

  A . improper fuel rack positing B . lengthy exhaust valve duration C . extend operation at light load D . excessively early injection timing

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

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• Leaky exhaust valve will result in which of the following？①high exhausttemperature ②low compression ③low firing pressure

  A.① and ② B.② and ③ C.① ② and ③

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• When the pressure gets low, the boiling-point becomes low. 气压变低，沸点就变低。

  A．omission B．combination C．addition D．obverse

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• （APS2000)“APU LOW OIL PRESSURE”灯何时亮是正常的？APU电门放在"ON"位而APU还没有工作时

  APU关车后 APU起动期间滑油压力上升到正常之前 任何时候亮都是不正常的

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• 气体的粘度随压力增高而增高。在低压时，气体粘度随温度升高而增加，随着压力的增加，温度升高对粘度增大的影响越来越小，当压力很高时（100×105Pa以上），气体粘度随温度升高而降低，明显表现出类似于液体的性质。Table 1-13 shows the dynamic viscosity of methane at different pressures and temperatures. It can be seen from the table that the viscosity of gas increases with the increase of pressure. At low pressure, the gas viscosity increases with the increase of temperature. With the increase of pressure, the influence of temperature increase on the inc

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