【正文】 A. ① only B. ② only C. ① and ② D. ① ② and ③ l l 12 Shaft sealing in a centrifugal pump can be effected by _______ 離心泵的軸封可用機(jī)械密封，也可用填料箱。 A. the mechanical seal B. packed stuffing boxes C. either A or B D. neither A nor B l 113 A reciprocating pump belongs to _______ according to its working principle. 根據(jù)工作原理，往復(fù)泵屬于容積式泵。 A. injector pumps B. positive displacement pumps C. centrifugal pumps D. centripetal pumps 1114 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. 對(duì)于容積式泵，泵腔室體積增大時(shí)吸人液體，體積減少時(shí)則排出液體。 A. injector B. positive displacement C. centrifugal D. centripetal 1115 What is the purpose of a relief valve? 釋放閥可用來(lái)當(dāng)排出閥關(guān)閉時(shí)將液體回流到吸人側(cè)。 A. to fill 2 tanks at the same time B. to use pump at a higher pressure C. to return liquid to suction side if discharge valve is closed D. All of the above are true. 1111 A 1112 C 1113 B 1114 B 1115 C 1116 The pump discharge pressure will be considerably higher than the pressure at the _______泵的排出壓力比泵進(jìn)口支管的壓力要高得多。 A. pump entry branch B. outlet pipe C. impeller D. None of the above is tree. 1117 Which of the following pumps belongs to centrifugal pump? 擴(kuò)壓式泵屬于離心式泵。 A. Piston pump B. Screw pump C. Diffuser pump D. Waterring pump 1118 The volute pump is one in which the impeller ____對(duì)于旋渦泵，葉輪將液體排至漸漸變寬的流道。 A. discharges into a gradually widening channel B. has stationary diffuser vanes C. produces no kiic energy D. All of the above are true. 1119 In _______ pumps a closed discharge valve will cause bursting discharge pressure. 柱塞泵是容積式泵，排出閥關(guān)閉將會(huì)產(chǎn)生具有破壞性的壓力。 A. centrifugal B. plunger C. injector D. water 1120 Which of the following pumps are selfpriming, and can deal with liquid from a level below the pump。 ① ejector。 ② screw。 ③ centrifugal. 噴射泵和螺桿泵都具有干吸能力，而離心泵沒(méi)有。 A. ① only B. ① ② and ③ C. ① and ③ D. ① ② and ③ 1116 A 1117 C 1118 A 1119 B. 1120 B 1121 The amount of fluid delivered by a gear pump can be regulated by _______ 齒輪泵屬于容積式泵，排量只能通過(guò)改變轉(zhuǎn)子的速度來(lái)調(diào)節(jié)。 A. throttling the pressure line B. changing the speed of the rotor C. either A or B D. None of the above is true 1122 Attempts are made to eliminate axial thrust in centrifugal pump by _______ 消除離心泵的軸向力，可使用具有平衡孔的葉輪，也可使用對(duì)稱葉輪。 A. providing the impeller with balancing holes B. the use of symmetrical impeller C. neither A nor B D. either A or B 1123 Which of the following pumps will build up a bursting pressure or stall their motors if the discharge valves are closed? ① gear。 ② . centrifugal。 ③ . screw. 齒輪泵和螺桿泵都是容積式泵，排出閥關(guān)閉’將會(huì)產(chǎn)生具有破壞性的壓力，而離心泵不會(huì)。 A. ① and ② B. ① ② and ③ C. ① and ③ D. ② and ③ 1124 Which of the following operating features do displacement pumps bear if they are working under nocavitation condition? ① . output is almost directly proportional to speed。 ② . they are selfpriming。 ③ . they will develop a discharged pressure equal to the resistance to be overe, irrespective of speed. 容積式泵正常工作時(shí)具有以下特性：排量幾乎與轉(zhuǎn)速成正比；具有自吸能力；不管速 度如何，都能產(chǎn)生大小等于需克服阻力的排出壓力。 A. ① and ② B. ② and ③ C. ① and ③ D. ① ② and ③ 1125 The _______ pump discharges a nearly constant amount of liquid regardless of pressure. 不管壓力如何，容積式泵的排量幾乎恒定。 A. mixedflow B. axialflow C. centrifugal D. displacement 1121 B 1122 D 1123 C 1124 D 1125 D 1126 Which of the following pumps is used where a relatively high pressure and small capacity are required?往復(fù)泵一般用于高壓頭、小排量的場(chǎng)合。選項(xiàng) C應(yīng)是“ reciprocating pump”。 A. Volute pump B. Diffuser pump C. Regenerative pump D. All of the above 1127 Some pumps use packing as sealing gland. The gland should be ______ 一些泵使用填料作為密封格蘭，注意要少許松一點(diǎn)，讓液體稍微泄漏。 A. slack enough to allow slight leakage of fluid B. slightly clocked C. brought up tight so as not to allow any leakage D. fitted with a relief valve 1128 Air chambers are usually fitted to reciprocating pumps in order to ______ 往復(fù)泵中的空氣室用來(lái)保持流量穩(wěn)定。 A. increase discharge pressure B. increase suction vacuum C. develop pulsation flow D. keep a steady rate of flow 1129 The pipe friction and the resistance will ______ as a result of an increase in the amount of fluid flowing through the system. 系統(tǒng)流量增加時(shí)，管路摩擦和阻力將增大。注意“ rise”與“ raise”之區(qū)別。 A. reduce B. rise C. raise D. fall 1126 C 1127 A 1128 D 1129 B 1130 Which of the following will be the advantage of a centrifugal pump as pared with a reciprocating pump? ① Its discharge is continuous。 ② It has no internal valves。 ③ Upon accidental closing of discharge valve, excessive pressure will not build up. 離心泵與往復(fù)泵相比具有以下優(yōu)點(diǎn)：排量連續(xù)；無(wú)內(nèi)部閥件；如果排出閥關(guān)閉，不會(huì)產(chǎn)生過(guò)高的壓力。 A. ① ② B. ② ③ C. ① ② ③ D. ② only 1131 Which of the following pumps are selfpriming, and can deal with liquid from a level below the pump: ① reciprocating 。 ② vane。 ③ gear. ① ② ③ A. ① only B. ① and ② C. ② ③ and ③ D. ① ② and ③ 往復(fù)泵、齒輪泵和葉片泵都具有干吸能力。 1132 Centrifugal pumps can be designe