题目内容
（请给出正确答案）
A simple pumping system consists of a suction branch, a pump and _____.
A.a priming device
B.a discharge branch
C.a filter
D.a suction valve
简答题官方参考答案
（由简答题聘请的专业题库老师提供的解答）
更多“A simple pumping system consists of a suction branch, a pump and _____.A.a priming deviceB”相关的问题
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 impeller
B.from passage of impeller
C.from the periphery of the impeller
D.from the impeller
【英译汉必译题】
This week and next, governments, international agencies and nongovernmental organizations are gathering in Mexico City at the World Water Forum to discuss the legacy of global Mulhollandism in water - and to chart a new course.
They could hardly have chosen a better location. Water is being pumped out of the aquifer on which Mexico City stands at twice the rate of replenishment. The result: the city is subsiding at the rate of about half a meter every decade. You can see the consequences in the cracked cathedrals, the tilting Palace of Arts and the broken water and sewerage pipes.
Every region of the world has its own variant of the water crisis story. The mining of groundwaters for irrigation has lowered the water table in parts of India and Pakistan by 30 meters in the past three decades. As water goes down, the cost of pumping goes up, undermining the livelihoods of poor farmers.
What is driving the global water crisis？ Physical availability is part of the problem. Unlike oil or coal, water is an infinitely renewable resource, but it is available in a finite quantity. With water use increasing at twice the rate of population growth, the amount available per person is shrinking - especially in some of the poorest countries.
Challenging as physical scarcity may be in some countries, the real problems in water go deeper. The 20th-century model for water management was based on a simple idea: that water is an infinitely available free resource to be exploited, dammed or diverted without reference to scarcity or sustainability.
Across the world, water-based ecological systems - rivers, lakes and watersheds - have been taken beyond the frontiers of ecological sustainability by policy makers who have turned a blind eye to the consequences of over- exploitation.
We need a new model of water management for the 21st century. What does that mean？ For starters, we have to stop using water like there"s no tomorrow - and that means using it more efficiently at levels that do not destroy our environment. The buzz- phrase at the Mexico Water forum is "integrated water resource management." What it means is that governments need to manage the private demand of different users and manage this precious resource in the public interest.
A.dependent
B.independent
C.in series
D.in parallel
A mercurial barometer at sea is subject to rapid variations in height ("pumping") due to the pitch and roll of the vessel. To avoid this error，measurements of atmospheric pressure at sea are usually measured with a(n) ______.
A.syphon barometer
B.cistern barometer
C.aneroid barometer
D.fortin barometer
A.close the static leg filling valve
B.close the overflow tank falling valve
C.reduce the fuel oil pumping rate
D.stop the fuel oil pumping operation
A.Overloading
B.Over discharging
C.Overflow
D.Overtaking
A.notify the terminal superintendent
B.place a large drip pan under the leak and ping the scuppers
C.repair the hose with a patch
D.replace the hose
警告：系统检测到您的账号存在安全风险
为了保护您的账号安全，请在“简答题”公众号进行验证，点击“官网服务”-“账号验证”后输入验证码“”完成验证，验证成功后方可继续查看答案！
