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单选题
A positive displacement pump is that where the volume of the pump chamber is alternately increased to （） and then decreased to （）.
A
draw the liquid in；force the liquid out
B
force the liquid out；draw the liquid in
C
suction；draw
D
deliver；outlet
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更多 “单选题A positive displacement pump is that where the volume of the pump chamber is alternately increased to （） and then decreased to （）.A draw the liquid in；force the liquid outB force the liquid out；draw the liquid inC suction；drawD deliver；outlet” 相关考题
考题
Which statement is NOT true?A.While displacement pump works, volume of the working chamber will increase and decrease alternatelyB.A gear pump always has two gearsC.Any vane pump will have a rotor within a ringD.A balanced vane pump has two outlet ports and they are positioned symmetrically
考题
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
考题
All of the following are attributes that can be specified when creating a logical volume EXCEPT:()
A.Number of logical partitionsB.Disk where logical volume will resideC.Size of the logical volume control blockD.Position of the logical volume on the disk
考题
The amount of fluid delivered by a positive displacement pump can be regulated by _____.A.throttling the pressure lineB.changing the speed of the driving rotorC.either A or BD.None of the above is tree
考题
The pressure of a liquid leaving the pump can be referred to as the ______.A.total headB.discharge headC.net positive suction headD.suction head
考题
The free surface corrections depend upon the dimensions of the surface of the free liquids and the ______．A.volume of liquid in the tankB.displacement of the vesselC.location of the tank in the vesselD.height of the center of gravity of the vessel
考题
The free surface effects of a partially full liquid tank decrease with increased ______．A.Density of the liquidB.Placement of the tank above the keelC.Displacement volume of the shipD.Size of the surface area in the tank
考题
All of the following are attributes that can be specified when creating a logical volume EXCEPT:（）A、Number of logical partitionsB、Disk where logical volume will resideC、Size of the logical volume control blockD、Position of the logical volume on the disk
考题
With a scalable volume group, where is the logical volume control information stored on the disk?（）A、In the ODMB、In the volume group descriptor areaC、In the first 512 bytes of the logical deviceD、In the first block of the user data within the LV
考题
Where can a system administrator find information regarding configured physical volumes， volume groups， and logical volumes besides the Volume Group Descriptor Area （VGDA）？（）A、/etc/filesystemsB、/etc/environmentC、Object Data Manager （ODM）D、Logical Volume Control Block （LVCB）
考题
单选题If you heard a ‘crackling’ noise in centrifugal pump, the most probable cause of the problem would be（）A
insufficient speedB
cavitationC
excess discharge pressureD
excessive net positive suction head B
考题
单选题Which of the following hydraulic systems is not one of the three sub-division of the Hydraulic drive system?（）A
Constant pressure systemB
Variable pressure systemC
Variable displacement systemD
Constant volume system
考题
单选题A screw pump belongs to （） according to its working principle.A
reciprocating pumpsB
positive displacement pumpsC
centrifugal pumpsD
centripetal pumps
考题
单选题Gear pumps are of positive displacement type pumps because they discharge a near constant amount of liquid （） pressure.A
depending onB
in relative toC
regardless ofD
because of
考题
单选题A variable displacement system of hydraulic drives consists of （）.A
a variable displacement axial piston pumpB
a constant displacement axial piston pumpC
a reciprocating piston pumpD
a centrifugal pump
考题
单选题Which of the listed pumps is NOT a positive displacement pump?（）A
CentrifugalB
ReciprocatingC
GearD
Rotary
考题
单选题With a scalable volume group, where is the logical volume control information stored on the disk?（）A
In the ODMB
In the volume group descriptor areaC
In the first 512 bytes of the logical deviceD
In the first block of the user data within the LV
考题
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.A
increased；decreasedB
decreased；increasedC
decreased；decreasedD
increased；increased
考题
单选题Lube oil pumps taking suction from the sump of most small marine engines are usually （）.A
of the diaphragm typeB
of the centrifugal typeC
of the positive displacement typeD
independently driven by electric motors
考题
单选题In a diesel engine, a positive displacement type blower is usually （）A
gear drive by the engineB
driven by an exhaust gas turbineC
driven by a camshaftD
driven by separate motor
考题
单选题The bore of a diesel engine cylinder describes the （）A
swept volume of the cylinderB
inside diameter of the cylinderC
piston displacement in the cylinderD
length of the piston stroke
考题
单选题The output volume of a positive fixed displacement pump can be changed only by （）.A
changing the angle of the tilting plateB
changing the speed of the pumpC
moving the slide block and rotorD
moving the shaft trunnion block
考题
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 displacementB
ejectorC
centrifugalD
air compressor
考题
单选题The pressure of a liquid leaving the pump can be referred to as the （）.A
total headB
discharge headC
net positive suction headD
suction head
考题
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.A
injectorB
positive displacementC
centrifugalD
centripetal
考题
单选题A vane pump belongs to （） according to its working principle.A
reciprocating pumpB
positive displacement pumpC
centrifugal pumpD
centripetal pump
考题
单选题The amount of fluid delivered by a positive displacement pump can be regulated by （）.A
throttling the pressure lineB
changing the speed of the driving rotorC
either A or BD
None of the above is tree
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