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1、电大液压气动技术 试题1 一、填空题(每空2分，共20分) 1以大气压为基准计测压力，基准以上的正值叫（表压力），基准以下的负值叫 （真空度）. 2液体粘度有三种表示方法：动力粘度、（条件）粘度和（相对）粘度。 3液体在管道中流动时的压力损失可分为（沿程）压力损失和（局部）压力损失两种。 4在旁油路节流调速回路中，溢流阀作（安全）阀用，其调定压力应大于克服最大负载 所需要的压力，正常工作时，溢流阀处于（闭合）状态。 5为保证气动系统正常工作，需要在压缩机出口处安装（后冷却器）以析出水蒸 气，并在储气罐出口安装（干燥器），进一步消除空气中的水分。 二、判断题(正确的打，错误的打X，每题2分，共2
2、0分) 1重力作用下的静止液体的等压面是水平面。( ) 2流经薄壁小孑L的流量与液体的密度和粘度有关。(X ) 3双作用叶片泵既可作为定量泵使用，又可作为变量泵使用。(X ) 4液压缸差动连接可以提高活塞的运动速度，并可以得到很大的输出推力。(X ) 5在旁油路节流调速回路中，液压泵的压力随液压缸的负载变化而变化。( ) 6液压系统的工作压力取决于泵的额定压力。( X ) 7油水分离器是一种空气净化设备，它安装于储气罐的进口处。( ) 8将马赫数M1的气体流动，称为超音速流动。( X ) 9每lm3湿空气中，含有水蒸气的质量称为湿空气的绝对湿度。( ) 10缓冲气动缸是依靠缓冲柱塞、节流孑L使
3、活塞运动速度减慢，实现缓冲作用的。( ) 三、单选题(每题3分，共15分) 1一流通截面为长方形截面(长为d，宽为6)起水力直径DH是( B )。 2齿轮泵的泄漏有多条途径，其中最严重的是( A )。 A。轴向间隙 B径向间隙 C. 啮合处 D. 卸荷槽 3若某三位换向阀中位机能中，油缸两腔与回油连通，系统不卸荷，则此阀的滑阀机能 为( D )。 AH型 BP型 C. M型 DY型 4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 )。 A. 过载保护作用 B控制油缸运动速度 C令油缸稳定运动的作用 D控制油路通断的作用 5等容过程的特征是( C )。 A. 气体的内能保持不变 B
4、气体的压力保持不变C. 气体对外不作功 D气体与外界无热量交换 四、计算题(每题15分，共30分) 1某液压泵的额定流量Q。=100Lmin，额定压力Pn25MPa，当转速n1450rmin 时，机械效率09。该泵理论流量Q，106Lmin。 (1)求泵的容积效率和总效率； (2)当泵转速降至500rmin时，计算额定压力下泵的理论流量和实际流量。 实际流量3655X09443436Lmin (4分) 2图示回路中已知液压缸无杆腔面积A，100cm2，有杆腔面积A250cm2，调速阀最小 压差Ap05MPa，仅当负载由0变到30000N时，活塞向右运动速度稳定不变，试求：(1)溢 流阀的调定压
5、力Py；(2)当F0时，泵的出口压力Py、回油腔压力P2。2解：(1)列出液压缸的力平衡方程：1AlP2A2+F P1 X100X10405X106X50X104+30000，P1325Mpa 溢流阀的调定压力：PyP1325Mpa (5分)(2)泵的出口压力由溢流阀调定, (5分) 列出液压缸的力平衡方程： 液压气动技术 试题2一、填空题(每空2分，共，20分) 表(相对) 绝对 2液体粘度有三种表示方法（动力），粘度，运动粘度和（恩氏）粘度。 3液体的流动状态有两种即：（层流）和 （紊流）。 4按结构形式分，常用的液压泵有（齿轮泵）、（叶片泵）和柱塞泵三类. 5气源装置中，（后冷却器）安装
6、在空气压缩机的出口处，而干燥器应安装在（储气罐） 的出口处。 二、判断题(正确的打，错误的打，每题2分，共20分) 1液体真空度的数值接近于一个大气压时，液体的绝对压力接近于零。( ) 2双叶片摆动缸的转矩是单叶片摆动缸的2倍。( ) 3流经薄壁小孔的流量与液体的密度有关，而与液体的粘度无关。( )4调速阀由差压式减压阀与节流阀并联而组成。( )5采用调速阀的进油路节流调速回路，只有节流损失，没有溢流损失。( )6采用节流阀的进油路节流调速回路，其速度刚度与节流阀流通面积A及负载的大小有关，而与油泵出口压力无关。( )7湿空气是干空气和水蒸气的混合气体。( ) 8要使气体流动速度达到超音速流动
7、，管道截面形状必须先收缩后扩张。( ) 9气动缸的无负载工作特性要求气动缸带有规定的负载，在规定的压力下平稳运动无爬行现象。( ) 10油水分离器的作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。( )三、单选题(每题3分，共15分) 1单杆活塞式液压缸缸筒内径为D，活塞杆直径为d，其差动连接时作用力为( B )。 2下列三位换向阀中位机能中，能实现系统卸荷的是( A )。 AH型 B.P型 CO型 D.Y型 3( B )系统效率较高。 A节流调速 B容积调速 C容积节流调速 4湿空气的绝对湿度是指( D )。 A湿空气在一定压力和温度下的含湿量 B湿空气饱和时的含湿
8、量 C.lkg湿空气含有水蒸气的质量 D 湿空气含有水蒸气的质量 5 等温过程的特征是( A )。 A气体的内能保持不变 B气体的压力保持不变C.气体对外不作功 D气体与外界无热量交换 液压气动技术 试题3 一、判断题(每题2分，共20分) (判断下列所述是否正确，正确填人“+”，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。( 十 ) 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。(十 ) 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
9、蒸气的混合气体。( 十 ) 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。(十 ) 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。( 十 ) 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 ) 1o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 )值为具粘度等级标号。 A. 动力粘度 B运动粘度C. 条件粘度 2齿轮泵泄漏的途径中，( B )泄漏最严重。 A径向间隙 B轴向间隙 C. 啮合线处 D. 卸荷槽 3下列三位换向阀中位机能中，能实现系统卸荷的是
10、( A )。 AH型 BP型 CO刑 DY型 4液压泵或液压马达的排量( C )。 A随流量变化 B随转速变化 C. 决定于结构尺寸 5单杆活塞缸采用差动连接方式时，具有效工作面积为( C )。 A无杆腔面积 B有杆腔面积 C. 活塞杆面积 6凋速阀是川( D )组合而成的。 A节流阀与顺序阀并联 B节流阀与J顷序阀串联 C节流阀与差压式减压阀并联 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U并联溢流阀是为了使阀起到( A )。 A过载保护作用 B. 溢流定压作用 C令汕缸稳定运动的作用 D控制汕路通断的作用 8湿空气的绝对湿度足指( D )。 A. 湿空气在定压力和温度下的
11、含湿量 B. 湿空气饱和时的含湿量 C. lkg湿空气含有水蒸气的质量 D. 1m3湿空气含有水蒸气的质量 9打湿空气的压力为o106MPa，于空气分压为o082MPa，若同温度厂饱和水蒸气分压为0.062MPa，则此湿空气的相对湿度为( B )。 A226 B387 C58.5 D75.6 10等容过程的特征是( C )。 A. 气体的内能保持不变 B气体的压力保持不变C气体对外不什功 D，气体与外界无热量交换三、画出下列元件的职能符号(每题3分，共15分) 1双向变量马达 2先导式溢流阀 3普通节流阀 4中位“P”型三位四通液动换向阀 5液控单向阀四、计算题(每题l；分，共30分) 1定量
12、叶片泵转速n1500 rmin，空载卸荷运行时，输出流量Qr56Lmin；当输出压力为Pp6.3MPa时，输出流量Q53Lmin，实测泵籼消耗功率。试求该泵的容积效率及总效率。2如图所示，流量为5Lmin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100cm2，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。 三、画图题(每题3分，共15分) 1. 2. 3. 4. 5. 四、计算题(30分) 1(15分)解： 取空载卸荷输出流量为理论流量，可得容积效率： 该泵输出的液压功率： 2(15分)解
13、： 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B的工作压力 故两活塞不会同时运动。 (D活塞B动，A不动。液压泵流量全部进入液压缸B，此时 (2)活塞B运动到顶端后系统压力升至PA时，活塞A运动，液压泵流量伞部进入液压缸A,此时 (3)活塞A运动到顶端后系统压力PP继续升高，直至溢流阀开启液压泵流量全部通过溢流阀回油箱。液压泵压力稳定在溢流阀的调定压力，即： Visa-free policy brings Chengdu biz, tourism boost. Making national headlines several times, Ch
14、engdus 72-hour visa-free policy has attracted wide attention from both Chinese and foreign experts and businessmen since it took effect on Sept 1 last year. The program permits citizens from 51 countries and regions including the United States, Australia, Canada and Japan who have valid visas and fl
15、ight tickets to a third country to spend three days in the city. The capital of Sichuan province is the first city in the western region of China to offer foreign tourists a three-day visa and the fourth nationwide to adopt the policy following Shanghai, Beijing and Guangzhou. Li Zhiyong, deputy dea
16、n of the tourism institute at Sichuan University, said the move contributes to a large increase in the number of overseas tourists and raises the citys level of internationalization. The policy will also bring direct economic revenue, Li said. Chengdu has many cultural legacies and is also a paradis
17、e for panda lovers with the worlds largest breeding and research center. Three days are long enough for foreign visitors to visit those iconic tourist spots, he noted. The city is home to the remains of the Jin sha civilization that dates back more than 3,000 years as well as the Qing cheng Mountain
18、s and the Du jiang yan irrigation system. Qing cheng has long been recognized as the birthplace of Taoism, Chinas ancient indigenous religion, while Du jiang yan is considered to be the oldest functioning water-control project in the world. Chengdu ranked third in tourist facilities, management and
19、services among 60 Chinese cities in a customer satisfaction survey released last year. But, Li added that efforts are still needed to develop more tourism products, improve English services and provide accurate translation of traffic signs and scenic billboards. Zhao Yun, chairwoman of British Chamb
20、er of Commerce Southwest China, told China Daily that his colleagues found the policy very convenient. A British client once flew here and stayed for just one day to check her ordered goods, she said. Zhao was born in Shanxi province, but she has lived in Chengdu for more than 10 years. My life was
21、like a running race moving from place to place. I also lived in Beijing and Shanghai before, she said. But Chengdu is a place that you never want to leave once settling down. It is now my second hometown, she said. If the environment is further improved, the city will attract more people to visit an
22、d live, with the 72-hour visa-free policy and compelling conditions in transportation, culture, climate and cuisine, he said. Foreigners also gave positive feedback on the policy. A spokesman from Dell Inc said the company has a global hub of operation in Chengdu, so the three-day visa has an immedi
23、ate and positive influence on the companys business development. Rudy Buttignol, president of the public broadcasting company in British Columbia, Canada, said his work requires frequent travel to Chengdu and the policy makes the trips easier. Data from the citys public security bureau shows some 10
24、0 foreign visitors enjoyed the 72-hour policy by the end of March, most of them from the United States, the United Kingdom and Germany. Chengdu also reported robust growth in its overall tourist industry last year. Official statistics show that it received some 150 million tourists last year, an inc
25、rease of 28 percent from 2012. Around 1.7 million came from abroad, an increase of 12 percent. Total revenue from tourism surpassed 133 billion yuan ($21.7billion). During his visit to Kazakhstan in September, Chinese President Xi Jinping proposed that China and Central Asia join hands to build a Si
26、lk Road economic belt to boost cooperation. The idea has been widely echoed in Central Asian countries, becoming an encouraging blueprint for Chinese areas along the Silk Road that has linked Asia and Europe for more than 2,000 years. In the next three weeks, China Daily reporters will travel throug
27、h the belt in China and in Kazakhstan, Uzbekistan and Turkey. They will show the progress and expectations of the countries, businesses and peoples on the route. Shaanxi - the start of the ancient Silk Road - has positioned itself as the new starting point for the development of the Silk Road Econom
28、ic Belt, which will strengthen Chinas cooperation with Central Asian countries, a senior official said. Shaanxi Governor Lou Qinjian said the province is fresh, rich and unique, as it was when it anchored one end of the ancient Silk Road. It is the best option for accommodating industrial transfers
29、from East China or the world at large, he said on Wednesday in Xian.Lou held a joint interview with 27 media, including China Daily, the first in a series of interviews entitled Chinese Media Along the Silk Road. The interviews will be in Shaanxi and Gansu provinces and the Xinjiang Uygur autonomous region, as well as Kazakhstan, Uzbekistan and Turkey. The media group held the first interview on Wednesday morning in Xian, the starting point of the ancient Silk Road, a trade channel established more than 2,000 years ago linking China, Central Asia and Europe.