电大液压气动技术课程作业解答(四)小抄参考

1、液压气动技术课程作业解答（四）一、填空题1. 按工作原理不同，空气压缩机可分为_ _和_两种。2. 单位质量的气体体积称为气体的_。3. 在等容过程中，气体的压力与_成正比，气体对外作功等于_。4. 为保证气动系统正常工作，需要在_ _处安装后冷却器，以析出水蒸气，并在 _ _处安装油水分离器，进一步清除空气中的水分。5. 湿空气的水蒸汽分压为0.025mpa，干空气分压为0.08mpa，相对湿度为50%，则湿空气的压力为_，同温度下饱和水蒸气的压力为_。6. 气动缸所耗压缩气体量等于_ _、_ _和_ _的乘积，一般情况下，计算气动缸耗气量时，还应把耗压缩气体量换算为_ _。7. 在气动缸的

2、速度控制回路中，常使用由_和_并联组合而成的流量控制阀。对于双作用气动缸，为避免气动缸的爬行，应采用_方式进行调速。8.在气动系统中，按工作原理和使用范围不同，调压阀可分为_和_两种。1容积式 速度式2比容3绝对温度 零4压缩机出口 后冷却器出口50.105mpa 0.05mpa6活塞面积 行程长度 每分钟往复次数 耗自由气体量7单向阀 节流阀 排气节流8直动式调压阀 先导式调压阀二 、判断题1等温过程中，气体与外界无热量交换，故气体的内能保持不变。（）注：等温过程是指气体在温度保持不变的条件下从一个状态变化到另一个状态的过程，由于温度不变所以气体内能保持不变，而并非与外界无热量交换，气体与外

3、界无热量交换的过程是绝热过程。2. 气动缸的无负载工作特性要求气动缸空载时在限定压力下平稳运行无爬行现象。（）注：气动缸的无负载工作特性是指在无负载条件下进行实验时，使气动缸能产生动作的最低工作压力，这个压力是使活塞低速运动、不产生爬行的极限压力。3. 缓冲气动缸是依靠弹簧的平衡力使活塞运动速度减慢，实现缓冲作用的。（）注：从缓冲气动缸的结构可知，缓冲气动缸是利用空气被压缩、吸收运动部件的动能而实现缓冲作用的。4. 先导式安全阀用压缩空气的气压作为控制信号，其先导阀是一个调压阀。（）注：由先导阀调整后的压缩空气作为控制信号，通过控制口导入主阀内，以代替直动式弹簧控制安全阀。5. 油水分离器的作

4、用是分离润滑油中的水分杂质，再经油雾器使气动系统中的气动元件得到润滑。（）注：油水分类器的作用是分离压缩空气中凝结成水分和油分的杂质，使压缩空气得到初步净化。三 、计算题1. 绝对压力为0.5 mpa，温度为30c的空气，绝热膨胀到大气压时，求其膨胀后的空气温度。解：由气体状态方程 和可得 （1）再由绝热过程的气体状态方程 可得 （2）（2）代入（1）得 所以 式中：t127330303k p10.5mpa p20.1013mpa 绝热指数k1.4代入计算 即膨胀后气体温度为81。2设湿空气的压力为0.1013 mpa，温度为20c，相对湿度为50%，求：（1）绝对湿度；（2）含湿量；（3）气

5、温降低到多少度时开始结露（露点）。解：查表105，可得压力为0.1013 mpa、温度为20c条件下，湿空气中饱和水蒸气分压力为pb0.0023mpa，饱和水蒸气的密度为17.3g/m3。（1）绝对湿度湿空气中饱和水蒸气的密度即饱和湿空气的绝对湿度 xb17.3g/m3由相对湿度为50%可得湿空气的绝对湿度 xxb50%8.65 g/m3（2）含湿量由pb0.0023mpa得 湿空气分压 ps pb50%=0.00115 mpa干空气分压 pgpps0.10130.001150.10015 mpa空气的含湿量 （3）露点当湿空气饱和，即相对湿度为100时，由pspb=0.00115 mpa查表

6、可得露点为9。3. 如图所示汽缸吊（吊取重物的气动缸），气源压力为0.5 mpa，起吊物体重量为fw=900n，活塞返回由活塞、活塞杆自重返回，自重fz=100n，活塞杆直径为d=20mm，机械效率=0.8，安全系数n=1.5，试确定气动缸内径d。 解：气缸吊为拉力作功，其拉力为式中：f（fwfz）n(900100) 1.51500n p0.5 mpa0.5106pa =0.8d20mm0.02m代入计算 取标准值 d80mm。4. 一单出杆双作用气动缸，内径为50mm，活塞杆直径为20mm，行程为300mm，每分钟往复运动10次，使用压力为0.6 mpa，试求其耗气量。解：活塞面积 耗压缩空

7、气量 耗自由空气量 winger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final win over england, has been passed fit 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

8、 encounter but australia have not conceded a try since josh charnleys effort in their first pool match against england on 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 intern

9、ational federation player of the year sonny bill williams who has attracted the most interest in the tournament so far.the 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 b

10、lacks in 2011.id give every award back in a heartbeat just to get across the line this weekend, said williams.the (lack of) 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 atten

11、d citys premier league match at chelsea on sunday.i am going to be at the match tomorrow and i have asked to meet yaya toure, 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 cska

12、for the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of european footballs governing body, 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:

13、we found no racist insults from fans of cska. baumgartner the disappointing news: mission aborted.the supersonic descent 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 precip

14、itation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of the 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 cru

15、ising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundary 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 o

16、nto something resembling an olympic diving platform.they blew it in 2008 when they got caught cold in the final and they 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 con

17、ceded was scored by englands josh charnley in the opening game of the tournament.that could be classed as a weakness, a team 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

18、- 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 unnoticed in the stands but not by your team-mates.it is as though their entire tournament has been preparation for the final.in johnathan thurston, cooper cronk, cameron smith and either billy slater or greg inglis at full-back they have a spine that is unmatched in rugby league. they have played in so many high-pressure games - a priceles