【正文】 et 1109 Throttling in the ______ line of a centrifugal pump involves the risk of the pump ，節(jié)流吸人管路，會產(chǎn)生氣蝕危險。 A. circular B. elliptical C. rectangular D. hexagon 1106 B 1107 B 1108 A 1109 A 1110 A l111 As for a hydraulic vane pump, which of the following is in contact with the vanes during working: ① the rotor。 ③ the external surface of the housing. 對于液壓葉片泵，工作時，轉(zhuǎn)子與葉片接觸。 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，往復泵屬于容積式泵。 A. injector B. positive displacement C. centrifugal D. centripetal 1115 What is the purpose of a relief valve? 釋放閥可用來當排出閥關(guān)閉時將液體回流到吸人側(cè)。 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? 擴壓式泵屬于離心式泵。 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)閉將會產(chǎn)生具有破壞性的壓力。 ① ejector。 ③ centrifugal. 噴射泵和螺桿泵都具有干吸能力，而離心泵沒有。 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，也可使用對稱葉輪。 ② . centrifugal。 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。 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. 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?往復泵一般用于高壓頭、小排量的場合。 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，讓液體稍微泄漏。 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，管路摩擦和阻力將增大。 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。 ③ Upon accidental closing of discharge valve, excessive pressure will not build up. 離心泵與往復泵相比具有以下優(yōu)點：排量連續(xù)；無內(nèi)部閥件；如果排出閥關(guān)閉，不會產(chǎn)生過高的壓力。 ② vane。 1132 Centrifugal pumps can be designed with a number of impellers _____ to attain a high final delivery ，可提高其排出壓頭。 A. deformed B. rusted C. cracked D. scaled 1135 The internal part of boiler should be welded by yard if found _____ 鍋爐內(nèi)側(cè)發(fā)現(xiàn)裂紋，應(yīng)電焊修理。 A. sealed B. informed C. leaky D. deformed 1137 In a _____ boiler the water flows through the inside of the tubes while the hot gases pass around the ，水在管子內(nèi)流動，而高溫氣體在管子外流動。 A. watertube B. firetube C. exhaust gas D. None of the above is tree. 1139 _____ are mounted in pairs to protect the boiler against overpressure. 鍋爐安裝安全閥以防鍋爐超壓。“ purge”意“驅(qū)氣”；而“ clear of air“清除空氣”。 A. drop as the boiler warms up B. rise as the boiler warms up C. remain unchanged until the boiler is hot enough D. rise and fall with the steam demand 1142 The donkey boiler may be given a bottom blow _____鍋爐熄火后，可進行下排污。 A. rise when the steam pressure is increased B. remain constant as long as the feed pump operates C. fall when the steam pressure is decreased D. vary as the steam demand changes 1144 The boiler feed water check valves are located on the _____鍋爐給水單向閥門位于給水管路中。 A. take no measures B. extinguish the fire as soon as possible C. feed water to the boiler D. open the blow down valve 1141 B 1142 D 1143 D 1144 D 1145 B 1146 The boiler feed pump discharge pressure is higher than the steam dnnn pressure to _____ A. ensure feed water flow into the boiler B. keep the steam drum pressure high C. prevent water hammer in the feed line D. help the feed water flash to steam 鍋爐給水泵排出壓力比蒸汽筒壓力要高，才能確保給水進人到鍋爐。 A. fuel tank B. bilge C. atmosphere D. auxiliary exhaust hne 1148 A donkey boiler is _____輔鍋爐即輔助性鍋爐。 A. pleted B. carried out C. cleaned D. steamed 1150 You should frequently pare drammounted and remotereading water level indicators. _____ between these have contributed to failures because of overheating through shortage of water, when a boiler was being oilfired. 鍋筒旁的水位指示器與遙控水位指示器的讀數(shù)要經(jīng)常進行比較，兩者的偏差會成為鍋爐運行故障 (因缺水而過熱 )的原因。 A. safety valve B. blow down valve C. sc