【Question 092】Boiler Foundation Questions (March 30)

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This post was last edited by zgj2405 on 2010-3-30 21:44. Please hide your replies; think carefully before posting, as edits are invalid! Those with different views on the provided answer keys can post discussions the next day. For multiple accounts under the same IP, only the first response indicating participation is valid. All participants receive 2 points as a reward. This round consists of multiple-choice questions, with 2 points for each question; an additional 5 points are given for getting all answers correct. In principle, answers are graded within 48 hours. For the specific method of hiding, see: http://bbs.hcbbs.com/viewthread.php?tid=492556&highlight=%D2%FE%B2% 1. The top clearance of a cylindrical bearing is ( ) that of an elliptical bearing. A、2 times B、1.5 times C、1 time D、1/2 time 2. A sharp increase in exhaust gas temperature and a decrease in the temperature of the hot air are clear signs of （ ） failure. A. Exhaust fan B. Supply fan C. Heater D. Air preheater 3. In the automatic three-element control for feedwater, （ 　） is a feedforward signal; it helps to prevent incorrect operation of the regulator due to \"false water levels\" and improves flow regulation under disturbances in steam flow. A. Drum water level B. Feedwater flow rate C. Steam flow rate D. Feedwater flow rate and steam flow rate 4. The circulation ratio using large-diameter downcomers is (　) compared to that using small-diameter downcomers. A. Low B. The same C. High D. Not necessarily 5. To prevent spontaneous combustion of coal powder in the powder bin after the furnace is shut down, it is necessary to (　). A. Open the powder bin baffle for ventilation　　　 B. Open the desiccant valve to maintain negative pressure in the powder bin　　　 C. Close the powder bin baffle　　　 D. Close all baffles and the desiccant valve