柴油機工作原理(雙語教學(xué))

1、第二講 船舶柴油機的工作原理Lesson 2 How Does a Marine Engine Work Review：1.船舶柴油機的基本特征往復(fù)式 reciprocating 壓縮發(fā)火 ignition by compression 內(nèi)燃機 internal-combustion engine2.船舶柴油機的分類根據(jù)工作循環(huán)(working cycle)：二沖程 two stroke（what is a stroke?）四沖程 four stroke根據(jù)結(jié)構(gòu)特征：筒形活塞式 trunk piston diesel十字頭式 Crosshead dieselExhaust valveInlet

2、 valveFuel injectorCylinderPistonPiston ringConnecting rodFour-stroke/trunk piston diesel engineCombustion chamberPiston pincrankshaftNew lesson: The working principle of marine diesel engine vContent:v1.四沖程柴油機工作原理v2.兩沖程柴油機工作原理v3.兩沖程柴油機的換氣形式(scavenge form) 工作循環(huán)：柴油機做一次功，或者兩次噴油間的工作循環(huán)：柴油機做一次功，或者兩次噴油間的運

3、轉(zhuǎn)過程叫一個工作循環(huán)，它由一些程序固定的運轉(zhuǎn)過程叫一個工作循環(huán)，它由一些程序固定的過程組成。過程組成。The process that a engine do a complete work, or process between two fuel injections is called a working cycle, which consists of a fixed sequence of events. 進(jìn)氣進(jìn)氣膨脹膨脹排氣排氣壓縮壓縮燃燒燃燒工作循環(huán)工作循環(huán)This cycle may be achieved（達(dá)到，（達(dá)到，完成）完成） either in four strokes

4、(沖程、行沖程、行程程) or two.四沖程柴油機：用活塞的四個行程完成一個工作四沖程柴油機：用活塞的四個行程完成一個工作循環(huán)的柴油機循環(huán)的柴油機二沖程柴油機：用活塞的兩個行程完成一個工作二沖程柴油機：用活塞的兩個行程完成一個工作循環(huán)的柴油機循環(huán)的柴油機Four stroke working cyclesuction吸氣行程expansion膨脹作功行程Compression壓縮行程Exhaust排氣行程1.The working principle of four stroke diesel enginesuction吸氣行程Compression壓縮行程1.1.吸氣沖程吸氣沖程進(jìn)氣閥上止

5、點前開，下止點后關(guān)進(jìn)氣閥上止點前開，下止點后關(guān)進(jìn)氣持續(xù)角進(jìn)氣持續(xù)角220220250250度度CACA。2.2.壓縮沖程壓縮沖程壓縮終點溫度壓縮終點溫度tctc達(dá)達(dá)600600700700C C 壓縮后期噴油器在上止點前一定壓縮后期噴油器在上止點前一定角度噴油，上止點附近壓縮發(fā)火角度噴油，上止點附近壓縮發(fā)火燃燒，壓縮過程持續(xù)燃燒，壓縮過程持續(xù)140140160 160 度度CACA。四沖程柴油機具體工作過程（1）（2） expansion 膨脹作功行程 Exhaust 排氣行程3.3.燃燒和膨脹行程燃燒和膨脹行程 p pz:5-8MPa, 10z:5-8MPa, 101515CA after

6、TDC CA after TDC tz:1400 tz:14001800 1800 C， 高溫高壓燃?xì)馔苿踊钊滦凶鞲邷馗邏喝細(xì)馔苿踊钊滦凶鞴Γ现裹c后約功，上止點后約4040CACA燃燒基本完燃燒基本完成成. .4.4.第四行程排氣行程第四行程排氣行程 排氣初期靠內(nèi)外壓差，當(dāng)活塞排氣初期靠內(nèi)外壓差，當(dāng)活塞由下止點上行時靠活塞推擠作用由下止點上行時靠活塞推擠作用（耗功），排氣閥延遲到上止點后（耗功），排氣閥延遲到上止點后關(guān)。排氣持續(xù)角關(guān)。排氣持續(xù)角230230260 260 度度CACA（3）（4）pz動畫動畫氣閥正時圓圖氣閥正時圓圖（valve timing diagram ）intake

7、 advance angle intake lag angle exhaust advance angle exhaust lag angle Valve overlap angle:+:Four-stroke cycle and timing diagrams2-Inlet valve closes2-Inlet valve closes1-Inlet valve opens1-Inlet valve opens7 78 85-Exhaust valve opens5-Exhaust valve opens 6-Exhaust value closes6-Exhaust value clos

8、es7-Injection commences7-Injection commences 8-Fuel valve closed8-Fuel valve closed圖1-7 四沖程柴油機定時圓圖圖1-7 四沖程柴油機定時圓圖1 12 25 56 6TDCBDC氣閥重疊角氣閥重疊角(Valve overlap angle) ：在換氣上止點附近，進(jìn)排氣閥同在換氣上止點附近，進(jìn)排氣閥同時開啟所持續(xù)的曲軸轉(zhuǎn)角時開啟所持續(xù)的曲軸轉(zhuǎn)角目的：目的：提高換氣效果，實現(xiàn)燃燒提高換氣效果，實現(xiàn)燃燒室掃氣；降低循環(huán)溫度。室掃氣；降低循環(huán)溫度。氣閥重疊角的大?。簹忾y重疊角的大?。悍窃鰤核臎_程機（非增壓四沖程機（25

9、50CA） 增壓四沖程機（增壓四沖程機（80130CA ）summary :1. For a four stroke engine, a recycle takes 2 revolution (720 CA) of crankshaft and 1 revolution of camshaft. The speed ratio of camshaft to crankshaft is 1 to 2. the working cycle is the third one. 總結(jié)：四沖程機一個工作循環(huán)曲軸轉(zhuǎn)兩轉(zhuǎn)（總結(jié)：四沖程機一個工作循環(huán)曲軸轉(zhuǎn)兩轉(zhuǎn)（720 CA），），凸輪軸轉(zhuǎn)一轉(zhuǎn)，凸輪軸與曲軸轉(zhuǎn)

10、速比為凸輪軸轉(zhuǎn)一轉(zhuǎn)，凸輪軸與曲軸轉(zhuǎn)速比為1：2，做功行程為第三，做功行程為第三行程。多缸機其余三行程能量由其他正在作功的氣缸供給，單行程。多缸機其余三行程能量由其他正在作功的氣缸供給，單缸機由飛輪供給缸機由飛輪供給二、二沖程柴油機工作原理two stroke engine working principle1 1結(jié)構(gòu)特點結(jié)構(gòu)特點曲軸一轉(zhuǎn)完成一個工作循環(huán)，故沒有單獨曲軸一轉(zhuǎn)完成一個工作循環(huán)，故沒有單獨的進(jìn)氣與排氣（換氣）過程，進(jìn)、排氣幾乎的進(jìn)氣與排氣（換氣）過程，進(jìn)、排氣幾乎同時進(jìn)行。同時進(jìn)行。If we combine the suction and exhaust operations wi

11、th the compression and expansion strokes, the four-stroke engine will be turned into a two-stroke one2、二沖程機二沖程機掃氣、掃氣、壓縮壓縮作功、作功、掃氣掃氣彎流掃氣The two-stroke cycle begins with the piston coming up from the bottom of its stroke, i.e. bottom dead center (BDC), with the air inlet ports or scavenge ports(掃氣口掃氣口

12、) in the sides of the cylinder being openedAs the piston moves about one fifth of the way up, it closes the inlet ports and the exhaust ports. The air is then compressed as the piston moves up. When the piston reaches the top of its stroke, i.e. the top dead center (TDC), both the pressure and the t

13、emperature of the air rise to very high values. vThe fuel injector injects a fine spray of fuel into the hot air and combustion take place, producing much higher pressure in the gases. The piston is forced(迫使迫使) downward as the high pressure gases expand until it uncovers the exhaust ports. The burn

14、ing gases begin to exhaust and the piston continues down until it opens the inlet ports. Then another cycle begins.In the two-stroke engine, each revolution of the crankshaft(曲軸曲軸) makes one power or working stroke, while in the four-stroke engine, it takes two revolutions to make one power stroke.

15、That is why a two-stroke cycle engine will theoretically（理論上）（理論上） develop twice (two times) the power of a four-stroke engine of the same size.3二沖程機工作循環(huán)的表示方法二沖程機工作循環(huán)的表示方法1）p-v示功圖示功圖2 2）定時圓圖）定時圓圖 無氣閥重疊角無氣閥重疊角2-Inlet opens2-Inlet opens1-Exhaust opens1-Exhaust opens3-Inlet closes3-Inlet closes4-Exhaust closes4-Exhaust closes5-Injectio