电大液压与气动技术期末试卷及答案小抄参考

1、系部_班级_姓名_学号_班内序号_密封线*职业技术学院2011/2012学年第二学期10大专机械专业液压与气动技术期末试卷（试卷编号：22020032-01）题号一二三四五总分得分一、填空题（24分，每空1分 ）1、液压传动系统的压力主要取决于 负载，执行元件的速度取决于进入它的液体的 流量。2、液压泵的效率主要包括 容积 效率和 机械 效率，前者反映了泄漏的大小，影响实际流量，后者反映了摩擦损失，影响驱动泵所需的转速。3、压力继电器是将 压力 信号转换为 电 信号的转换装置。4、液压控制阀是液压系统的_控制 元件。根据用途和工作特点不同，控制阀主要可分为 压力阀、方向阀、和 流量阀 三大类。

2、5、对同一定量泵，如果输出压力小于额定压力且不为零，转速不变，试比较(a)实际流量，(b)理论流量，(c)额定流量三者存在数值上的关系：a b，b c。6、液压系统由动力元件 、执行元件、控制元件、辅助元件和工作介质五个部分组成。7、为了消除齿轮泵的困油现象，通常在两侧盖板上开 卸荷槽 ，使闭死容积由大变少时与 压油 腔相通，闭死容积由小变大时与 吸油 腔相通。 8、液体在管道中存在两种流动状态， 层流 时粘性力起主导作用， 紊流 时惯性力起主导作用，液体的流动状态可用 雷诺数 来判断。9、变量泵中，叶片式但作用叶片泵是通过改变 偏心距 实现排量的改变，轴向柱塞泵是通过改变 斜盘倾角 实现排量

3、改变。二、判断题（10分，每题1分）1、齿轮泵可以通过改变转速改变流量，故属于变量泵。 （ f ）2、节流阀和调速阀都是用来调节流量及稳定流量的流量控制阀。 （ f ）3、滑阀为间隙密封，锥阀为线密封，后者密封性能好。 （ t ）4、因液控单向阀关闭时密封性能好，故常用在保压回路和锁紧回路中。 （ t ）5、溢流阀是通过阀口的溢流量来实现调压、稳压的一种压力控制阀。 （ t ）6、减压阀输入端压力小于其调定压力时，输出端压力为调定压力。 （ f ）7、先导式溢流阀因为其结构复杂，调节系统压力时不稳定。 （ f ）8、液压马达是将机械能转化为液压能的元件。 （ f ）9、由于橡胶管容易老化，故液

4、压系统中管路不得采用。 （ f ）10、相同的制造精度下，柱塞泵的容积效率最差。 （ f ）三、选择题（20分，每空2分 ）1、溢流阀作安全阀使用时，系统正常工作时其阀芯处于（ b ）状态a 全开 b 全关 c 半开半关 d 不一定2、高压系统宜采用( b )泵。a外啮合齿轮 b轴向柱塞 c叶片 d内啮合齿轮3、选择液压油时，主要考虑油液的（ c ）。a密度 b成分 c 黏度 d 颜色4、如下绝对压力关系表达式是正确的（ c ）。a.大气压-相对压力 b.大气压-表压力c.大气压+相对压力 d.相对压力-大气压5、液压系统为防止液压冲击需设置( a )回路。 a泄压 b增压 c减压 d锁紧6、

5、调速阀由（ b ）与节流阀串联组成。a减压阀 b定差减压阀 c溢流阀 d差压式溢流阀 7、液压系统中泵输出压力3mp，阀门调定压力：溢流阀调5mp,减压阀4mp,减压阀输出端压力为（ a ） a 3mp b 4mp c 5mp d 0mp8、伯努利方程为（ b ）在流体力学中的应用。 a 体积不变定理 b能量守恒定律 c质量守恒定律 d动量守恒定律9、下列选项那个不属于油箱的功能（ b ）。a 储存工作介质 b储存压力能 c分离油液中的空气 d散热10、单杆式液压缸有杆腔进油一般用于（ c ）。 a 快进 b 工进 c 快退 d 停止运动四、分析题（16分，每题8分 ）1、右图中abcd各元件

6、的名称？各起什么作用？答：a溢流阀 维持系统压力安全 b顺序阀 控制液压缸的运动顺序 c调速阀 调节左侧液压缸的速度 d单向阀 右侧液压缸前进时经过调速 阀，后退时经过单向阀，实现快退。2、分析右图压力分级调压回路；该回路能够实现多少压力级？每个压力级的压力值是多少？ 答：1）该回路有8个压力级 2）分别为：0 ，0.5 ,1.0 ,1.5， 2，2.5 , 3 ,3.5五、计算题（30分，每题10分 ）1液马达的排量为250ml/r，进口压力为10mpa,出口压力为0.5mpa,总效率=0.9,马达的容积效率为0.92,若输入流量为20l/min；试求：（1）实际输出扭矩；（2）实际输出转速

7、。 解：1）机械效率：机械=/容积输出扭矩：t=pv机械/2 =（10-0.5）mpa*250ml*(0.9/0.92)/(2*3.14) =370n*m 2)输出转速：n=q*容积/v =20 l/min*0.92/250ml/r. =74.6=75r/min 2、单杆液压缸采用差动连接，运动速度要求： 1） 2）分别求两种情况下活塞面积和活塞杆面积之比为多少？解：快进连接方式差动连接，速度：v快进 =4 q/d2 快退有杆腔进油，速度：v快退 = 4q/(d2-d2) 1)活塞面积和活塞杆面积之比为:5:2 2) 活塞面积和活塞杆面积之比为4:13、右图回路中，液压缸面积a=100cm2，

8、溢流阀调定压力4mpa，减压阀调定压力2mpa，不计管路压力损失，1）泵压力大于溢流阀调定压力，缸处于夹紧状态，求a、b、c三点的压力。2）泵压力为4.5 mpa，求活塞能够产生的推力。3）活塞做空载运动，求a、b、c三点的压力。解：1）a=2 mpa; b=4 mpa; c=2 mpa 2) f=pxa=4 mpa * 100 cm2 =40kn 3)a=b=c=0 mpawinger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final win over england, has been passed fit

9、after a lower-leg injury, while slater has been named at full-back but is still recovering from a knee injury aggravated against usa.both sides boast 100% records heading into the encounter but australia have not conceded a try since josh charnleys effort in their first pool match against england on

10、 the opening day.aussie winger jarryd hayne is the competitions top try scorer with nine, closely followed by tuivasa-sheck with eight.but it is recently named rugby league international federation player of the year sonny bill williams who has attracted the most interest in the tournament so far.th

11、e kiwi - with a tournament high 17 offloads - has the chance of becoming the first player to win the world cup in both rugby league and rugby union after triumphing with the all blacks in 2011.id give every award back in a heartbeat just to get across the line this weekend, said williams.the (lack o

12、f) air up there watch mcayman islands-based webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomorrow and i have asked to meet yaya to

13、ure, he told bbc sport.for me its about how he felt and i would like to speak to him first to find out what his experience was.uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of european footballs governing body

14、, has also ordered an immediate investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska. baumgartner the disappointing news: mission aborted.the supersonic descent

15、could happen as early as sunda.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of the

16、 atmosphere (the troposphere) where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundary

17、layer (called the tropopause),e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.they blew it in 2008 when they got caught cold in the final and they

18、will not make the same mistake against the kiwis in manchester.five years ago they cruised through to the final and so far history has repeated itself here - the last try they conceded was scored by englands josh charnley in the opening game of the tournament.that could be classed as a weakness, a t

19、eam under-cooked - but i have been impressed by the kangaroos focus in their games since then.they have been concentrating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line, completing sets and a good kick-chase. theyve been great at all the unglamorous stuff that often goes