单选题Through a （） pump, the liquid is transferred from the suction to the discharge by the mechanical variation of the volume of a chamber or chambers.Apositive displacementBejectorCcentrifugalDair compressor
单选题
Through a （） pump, the liquid is transferred from the suction to the discharge by the mechanical variation of the volume of a chamber or chambers.
A
positive displacement
B
ejector
C
centrifugal
D
air compressor
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相关考题：
Which of the following terms is used to identify the pressure of the liquid entering a pump?A.Suction headB.Pump headC.Discharge headD.Total head
第二组Displacement pumps are those where the volume of the pump chamber is alternately increased to draw the liquid in from the suction pipe and then decreased to force the liquid out into the delivery pipe. Centrifugal pumps are those wherein an impeller rotating at high speed throws the liquid by centrifugal force from the center to the periphery of the impeller where the liquid is discharged through the delivery outlet.Gear pump consists of two or more meshing gears (spur, single or double helical teeth) enclosed m a close-fitted housing. These are used extensively for pumping fuel oil, lubricating oil and hydraulic oil. When gears are unmeshed on the inlet side, a pressure drop occurs that helps the atmospheric pressure acting on the surface of the oil in the reservoir to force it up the pipe to fill the void, the oil is then transferred around the periphery of the pump housing. As the gear teeth mesh again on the outlet side, they form. a seal that prevents oil from backing up to the inlet, the oil in the void is then be forced out into the discharge line.All vane pumps have a rotor driven within a ring (cam ring) by a drive shaft coupled to a prime mover. A cylindrical rotor with sliding vanes, generally in radial slots, rotates within the ring. The center of the rotor is offset from the center of the ring. In a simple vane pump, as the rotor turns, the vanes are forced outward against the inner surface of the cam ring by centrifugal force. This outward radial movement of the vanes and turning of the rotor causes the chamber between the vanes to increase as the vanes pass further away from the inlet port. This increase in volume results in a lowering of pressure until the atmospheric pressure is sufficient to force oil from the reservoir into the inlet chamber. Oil from the inlet is swept away by the vanes toward the outlet port through a decreasing series of chambers until it is forced through the outlet port. A vane pump of balanced design has an elliptical cam ring so that two pumping chambers are formed. This pump is in hydraulically balance, since the two intake and two outlet ports are diametrically opposed to each other. Therefore the side loads exerted on the rotor cancel out, thereby increasing bearing lift and permitting high operating pressure.According to the last sentence of paragraph 1, from where the liquid is discharged through the delivery outlet?A.from the eye of the impellerB.from passage of impellerC.from the periphery of the impellerD.from the impeller
Which statement is NOT true?A.In a simple vane pump, the rotor and cam ring are exactly concentricB.Balanced vane pump has an elliptical cam ringC.Liquid in both gear pump and vane pump are forced out to the outlet.D.Balanced vane pumps can work at a higher pressure than the simple vane pump
单选题A positive displacement pump is that where the volume of the pump chamber is alternately increased to （） and then decreased to （）.Adraw the liquid in；force the liquid outBforce the liquid out；draw the liquid inCsuction；drawDdeliver；outlet
单选题The heat generated by a fire will be transferred through a bulkhead or dock, as a result of （）.AconductionBradiationCconvectionDadvection
单选题Which of the following statements is correct with regards to the operation of a centrifugal cargo pump?（）AOil is discharged from the impeller through the outletBGravity causes the oil to flow toward the dischargeCThe self-priming feature of the centrifugal pump enables it to draw its own suction as it startsDThe discharge capacity varies directly with the speed of the impeller
单选题While flowing through the volute in a centrifugal pump, part of the （） energy of the liquid is converted to （） energy.Akinetic；pressureBkinetic；essentialCpressure；kineticDpressure；height
单选题The function of a centrifugal pump double volute casing is to （）.Areduce radial thrust to the impellerBdouble the liquid velocity through the pump when compared to a single voluteCreduce hydraulic end thrustDprovide the effect of multi-staging
单选题A multistage centrifugal pump can be BEST described as having （）.Atwo or more impellers housed together in one casing and mounted on a single shaftBa single stepped impeller mounted in a progressively staged casingCa large radial clearance between the impeller and casing to prevent overheating due toDan increase in the discharge velocity of the liquid with a corresponding decrease in pressure through the stages
单选题Which of the following statements about pump operations is NOT a correct statement?（）AIn order for a fluid to be pumped, a fluid must be made to flowBA substance must be cold in order for it to be pumpedCThe kinetic energy imparted by the pump can be used to force a liquid through a hydraulic systemDA pump must receive its energy from an external source
单选题Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? （） (1) reciprocating (2) rotary (3) centrifugalA（1）onlyB（1）and（2）C（1），（2）and（3）D（2）and（3）
单选题Before liquid can flow into a pump, the air in the suction line must be （） sufficiently to cause the liquid to flow into the suction chamber.AfilledBevacuatedCcompressedDcharged
单选题The static suction lift of a pump is the difference in elevation between the （）.Acenterline of the pump and the level of the liquid in the suction well when the source of liquid is below the pumpBcenterline of the pump and the suction liquid level when the source of liquid is above the pumpCcenterline of the pump and the level of the discharge liquidDliquid levels of the suction and discharge
单选题If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.Acapacity will increaseBcapacity will decreaseCsuction pressure will increaseDsuction pressure will decrease
单选题A pump is said to have "negative suction head" when the pump is located （）.Abetween the suction and dischargeBbelow the liquid supplyCabove the liquid supplyDany of the above
单选题A positive displacement pump is that where the volume of the pump chamber is alternately （） to draw the liquid in and then （） to force the liquid out.Aincreased；decreasedBdecreased；increasedCdecreased；decreasedDincreased；increased
单选题A pump is defined as device that（）Aproduces pressureBimparts energy to a fluid to move it from level ‘A’ to level ‘B’Ccreates a vacuum to move a liquid in all installationDis to develop a pressure differential
单选题To absorb the wear resulting from impeller rotation and abrasives in the liquid, a centrifugal pump is usually fitted with （）.Alantern ringsBbearingsCeasing volutesDwearing rings
单选题If an emergency pump control is used as the emergency shutdown on a tank vessel，it must（）.Astop the flow of oil at the main deck manifoldBprevent the oil from leaving the shore facilityCprevent the oil from siphoning through the pumpDNone of the above
单选题The fuel is supplied to the pump through ports or openings in the （） or cylinder of the pump.AbottleBinjectorCpistonDbarrel
单选题The basic function of the centrifugal pump impeller is to （）.Adirectly increase the pressure of the liquid being pumpedBdirectly increase the velocity of the liquid being pumpedCconvert the potential energy of the liquid to kinetic energyDseparate air from the liquid being pumped
单选题“Flooding back” is a condition where the liquid refrigerant （）.Avaporizes in the condenserBreaches the compressor through the suction lineCflashes in the liquid lineDcondenses in the receiver
单选题If an emergency pump control is used as the emergency shutdown on a tanker，it must（）.Astop the flow of oil at the main deck manifoldBprevent the oil from leaving the shore facilityCprevent the oil from siphoning through the pumpDNone of the above
单选题Through a （） pump, the liquid is transferred from the suction to the discharge by the mechanical variation of the volume of a chamber or chambers.Apositive displacementBejectorCcentrifugalDair compressor
单选题A （） pump is that where the volume of the pump chamber is alternately increased to draw the liquid in and then decreased to force the liquid out.AinjectorBpositive displacementCcentrifugalDcentripetal
单选题A centrifugal pump vibrates excessively during operationUpon disassembling the pump it is found that the impeller is out of balanceWithout an available spare, you should （）.Adrill holes through the heavy side of the impeller until it balancesBweld counterweights to the light side of the impellerCremove metal from the heavy side by machining in a latheDacid wash and serape the heavy side until it balances