2018年电大液压气动技术试题及答案全参考(3) - 图文

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一、判断题(每题2分，共20分)

(判断下列所述是否正确，正确填入“+”，错误则填“一”)

1．液体的体积模量越大，表明该液体抵抗压缩的能力越强。( + )

2．相同流量、压力下，双叶片摆动缸的角速度是单叶片摆动缸的2倍。( 一 ) 3．液压系统的工作压力取决于泵的额定压力。( 一 ) 4．高压系统中宜采用柱塞泵。(+ )

5．溢流阀的开启比越小，控制系统的压力越稳定。(一 ) ． 6．湿空气是干空气和水蒸气的混合气体。(+ )

7．要使气体流动速度达到超声速流动，管道截面形状必须先收缩后扩张．。(+ ) 8．后冷却器是一种空气净化设备，安装于空气压缩机的出口处。( + )

9．等温过程中气体的内能保持不变，是由于气体与外界无热量交换。( 一 )

10．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。(一 ) 二、选择题(每题2分，共20分)

1．我国采用40℃时液压油的( B．运动粘度

2．齿轮泵泄漏的途径中，( )泄漏最严重。B．轴向间隙

3．下列三位换向阀中位机能中，能实现系统卸荷的是( )。A．H型 4．液压泵或液压马达的排量( )。C．决定于结构尺寸

5．单杆活塞缸采用差动连接方式时，其有效工作面积为( )。C．活塞杆面积 6．调速阀是用( )组合而成的。D．节流阀与差压式减压阀串联

7．以变量泵为油源时，在泵的出口并联溢流阀是为了使阀起到( )。A．过载保护作用 8．湿空气的绝对湿度是指( )。D．1m3湿空气含有水蒸气的质量

9．有湿空气的压力为0．106MPa，干空气分压为0．082MPa，若同温度下饱和水蒸气分压 为0．062MPa，则此湿空气的相对湿度为( )。B．38．7％ 10．等容过程的特征是( )。 C．气体对外不作功

2．如图所示，流量为5 L／rain的液压泵驱动两个并联液压缸，已知活塞A重10000N，活塞B重5000N，两个液压缸活塞工作面积均为lOOcm2，溢流阀的调整压力为2MPa，设初始两活塞都处于缸体下端，试求两活塞的运动速度和液压泵的工作压力。

2．)解：

根据液压系统的压力决定于外负载这一结论，由于活塞A、B重量不同，可知活塞A的工作压力：

活塞8的工作压力

故两活塞不会同时运动。

(1)活塞8动，A不动，液压泵流量全部进人液压缸B，此时

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(2)活塞8运动到顶端后，系统压力升至Pn时，活塞A运动，液压泵流量全部进入液压缸A，此时

(3)活塞A运动到顶端后，系统压力P。继续升高，直至溢流阀开启，液压泵流量全部通过浠流阀回油箱．滴乐泵压力稳定存浠流阀的调宗压力．即：

五、综合题(15分)

附图所示系统可实现“快进一中速进给一慢速进给一快退一停止’’的工作循环，试填写电磁铁动作表。(电磁铁通电为“+”号)

电磁铁的动作顺序表如下：

2．

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专业好文档 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 encounter but Australia have not conceded a try since Josh Charnley's effort in their first pool match against England on the opening day. Aussie winger Jarryd Hayne is the competition's 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. 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 Blacks in 2011. \The (lack of) air up there Watch mCayman Islands-based Webb, the head of Fifa's anti-racism taskforce, is in London for the Football Association's 150th anniversary celebrations and will attend City's Premier League match at Chelsea on Sunday. \\Uefa has opened disciplinary proceedings against CSKA for the \ City's 2-1 win. Michel Platini, president of European football's governing body, has also ordered an immediate investigation into the referee's actions. CSKA said they were \ 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 precipitation 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 cruising 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 onto 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 conceded was scored by England's 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 - strong defence, especially on their own goal-line, completing sets and a good kick-chase. They've 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 priceless asset going into Saturday. The Kiwis are a lot less experienced but winning a dramatic match like their semi-final against England will do wonders for their confidence.

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