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1、Chapter 5 The Principle of Gas Compressor,工程热力学的研究内容,1、能量转换的基本定律,2、工质的基本性质与热力过程,3、热功转换设备、工作原理,4、化学热力学基础,压气机的作用及分类,压气机的作用,生活中：自行车打气。,工业上：锅炉鼓风、出口引风、炼钢、燃气轮机、制冷空调等,工作原理结构,活塞式(往复式),叶轮式（离心式、轴流式）,引射式压缩器,压力范围,通风机,鼓风机,压缩机,Fan,Compressor,Fanner,矿井中：通风、动力。,5-1. The principle of reciprocating compressor,5-3. Mu
2、ltilevel compress with intercooler,内容提要,5-2. Effect of clearance,压缩过程,空气,V,p,1,2,大气压,压缩,风包压力,排气,膨胀,吸气,3,4,排气过程,膨胀过程,吸气过程,工作循环,余隙V0,5-1 The principle of reciprocating compressor,1.The principle,(1)、Very fast, Q=0。,(2)、Very slow, 热全散走。,(3)、实际压气过程是,压气机的理论工作过程,v,p,P1,1,P2,2T,2s,2n,s,T,P1,1,P2,2s,2n,2T,定
3、温压缩过程：,绝热压缩过程：,多变压缩过程：,5-1 The principle of reciprocating compressor,进气流动功：,排气流动功：,5-1 The principle of reciprocating compressor,v,p,P1,1,P2,2T,2s,2n,定温压缩过程：,绝热压缩过程：,多变压缩过程：,压气机所需的机械总功为压缩功、进气流动功、排气流动功的代数和。,定温压缩消耗的机械功最小，绝热压缩消耗的功最大，多变过程消耗的功介于两者之间。为了减少耗功量，压缩时要有效冷却压缩空气，使其尽量接近定温压缩。,技术功,5-1 The principle
4、of reciprocating compressor,举 例,自行车压力通常应维持在0.25MPa左右，用手动打气筒向轮胎充气时用湿毛巾包在打气筒外壁，会有什么后果？,v,p,P1,1,P2,2T,2s,2n,s,T,P1,1,P2,2s,2n,2T,5-1 The principle of reciprocating compressor,Notice that there will be a difference between the work necessary to compress the gas from states 1 to state 2 and the total wo
5、rk of process: WsWnWT,5-1 The principle of reciprocating compressor,5-1 The principle of reciprocating compressor,自行车压力通常应维持在0.25MPa左右，用手动打气筒向轮胎充气时用湿毛巾包在打气筒外壁，会有什么后果？,2.The work of compressorAdiabatic compressor,5-1 The principle of reciprocating compressor,Isothermal compressor,5-1 The principle of
6、 reciprocating compressor,Polytropic compressor,2.The work of compressor,5-1 The principle of reciprocating compressor,V,p,P1,1,P2,2,4,3,1.Clearance,f,g,5-2 Effect of clearance,V,p,P1,1,P2,2,4,3,1.Clearance,f,g,5-2 Effect of clearance,2.The work of compressorPolytropic compressor,5-2 Effect of clear
7、ance,5-2 Effect of clearance,1.System,Cooling water,Low pressure gas,1st-stage compression,2nd-stage compression,Intercooler,High pressure gas,1,2,2,3,5-3 Multilevel compress with intercooler,2.Diagram,V,p,P1,1,P2,2,3,e,g,f,2,3,Pm,3T,5-3 Multilevel compress with intercooler,3.The work of compressor,
8、5-3 Multilevel compress with intercooler,3.The work of compressor,5-3 Multilevel compress with intercooler,3.The work of compressor,5-3 Multilevel compress with intercooler,例：空气在某压气机中被压缩。压缩前空气的参数是p1 =0.1MPa, v1 =0.845m3/kg; 压缩后的参数是p2 =0.8MPa, v2 =0.175m3/kg。假定在压缩的过程中，1kg空气的热力学能增加146kJ, 同时向外放出热量50kJ,压气机每分钟生产压缩空气10kg。求： （1）压缩过程中对每公斤气体所作的功； （2）每生产1kg的压缩气体所需的功； （3）带动此压气机至少要多大功率的电动机？,压气机进、排气,压气机压气,Exercise,
