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1、论 文 翻 译Loader engine principle of work1 two-stroke diesel engine principle of work Through the pistons two stroke to complete a work of diesel engine cycle called two-stroke diesel engine, the oil machine to complete a work cycle crankshaft only turn around, and four stroke than diesel engine, it im
2、proved doing work ability, in the concrete structure and working principle of differences. Two stroke diesel and four stroke diesel engine is the same basic structure, the main difference in with gas institutions. Two stroke diesel no intake valve, some even the exhaust valve also have no, but in th
3、e open air cylinder and and vent; Or a carbon monoxide and exhaust valve and institutions. And set a driven by moving parts and air pump and storage of the air pressure and gas box, using the piston and the body to cooperate to complete with gas, which can simplify the structure of diesel engine. Fi
4、gure is two stroke diesel working principle diagram. And in one side of the diesel engine with air pump, its rotor drive by diesel engine. Air from the pump suction inhaled, the compression back out, stored in with larger volume of the gas and in the box, and in it maintain a certain amount of press
5、ure. Now that two stroke diesel in the work Principle. A, burning inflation and exhaust stroke: Fuel burning in the combustion chamber, high temperature and high pressure gas generated. The pistons in the push of fuel gas, the BDC downward motion, foreign doing work. The piston down until the vent o
6、pen (right now crank in points, and gas inflation to do work at this time in the air over a large waste gas, on its own, high pressure free exhaust from vent queue of people to the exhaust. When in cylinder pressure drop to close to sweep gas pressure (general sweep gas box of the gas pressure and f
7、or 0-12, descending the piston engines and 3 open (right now in the position of the crank four points, and gas air into the cylinder, but at the same time, the waste gas cylinders by the vent out of the cylinder piston running to the next. The point, the stroke over, but he gas process continues unt
8、il the next stroke vent closed (right now in the position of crank yet). Two, and gas and compression strokes: The piston check point by next move upward, the piston engines in obscure before Saul, and Saul supply pump by stored in the air and gas, through the air and into the cylinder and the cylin
9、der is entered into the remaining waste gas cylinder air through the vent sweep out of the cylinder. The piston continue to uplink, gradually cover and exhaust, when he is fully closed at this time after engines (crank in points, and stop filling the air, exhaust still on the stage, called exhaust s
10、tage after. vent closed (right now crank in points, and the air cylinder began to be compressed. When compressed first check point when fuel injector balls, spray, high temperature and high pressure cylinder with people of air mix, and immediately, on the near the angry, themselves. This stroke on f
11、ire, and end with before one stroke formed a complete work cycle. Two stroke diesel damping-displacement figure figure, among them, for injection starting point for the pistons, BDC, to burning the end. Two stroke diesel and four stroke diesel engine has some obvious advantages compared, there are,
12、of course, itself inherent disadvantages. 2 four stroke diesel engine principle of work Diesel engine work by air, compression, burning inflation and exhaust the four process to complete the four process constitute a work cycle. The piston walk four process to complete a work of diesel engine cycle
13、called four stroke diesel engine. Now controls the above animation that its the job of the reason for the original. A. Intake stroke The first stroke-intake, it is to make the task in the air filled with fresh air. When air intake stroke began, the piston located on the check point, cylinders in the
14、 combustion chamber there were some waste gas. When the crankshaft cubits, driving the piston connecting rod on the gear mobile, and at the same time, the use and the crankshaft connecting transmission mechanism make intake valve open. As the pistons downward motion, in cylinder piston top volume in
15、crease gradually: cause cylinder the air pressure inside the lower than the pressure inside the inlet pipe, so the outside air is constantly filled with cylinder. In the process of inlet gas pressure in the air cylinder with the volume of change such as animation as shown. Figure y-coordinate said g
16、as pressure P, said the abscissa denotes the cylinder volume Vh (or the piston of blunt S), the graphics called the damping-displacement figure. In the chart the pressure curve said work diesel, gas pressure in the cylinder of the change rule. From the earth we can see that intake began, and because
17、 it has residual waste gas, so just above the atmospheric pressure P0. In the intake process because of the air through the intake pipe and into the air valve produced when resistance to flow, so inlet length of the gas pressure below the atmospheric pressure, and the value of 0.085 0.095 MPa, in th
18、e whole process of air, gas pressure in the cylinder roughly remain unchanged. When the pistons downward motion under close to the point and rushed into the air cylinder is still has the very high speed, the inertia is very big, in order to use the moment of inertia of the airflow to improve ChongQi
19、Liang, intake valve on the piston out the next check point later just shut down. Though the piston uplink, but because the air of inertia, gas can still filling one cylinder. 2. Compression stroke The second stroke-compression. When the piston check from compressed between point BDC movement, the le
20、ngth of the function has two, one is to raise the temperature of the air, and to prepare for fuel combustion, 2 it is to do work for the gas expand creates the condition. As the piston uplink, into the air valve closed after the air in cylinder by compression, with the volume of the tiny constantly,
21、 air pressure and temperature is rising, the end of the compression of air humidity and pressure and compression levels, namely compression ratio and relevant, general compression of the pressure and temperature for: Pc = 4 8 MPa, Tc = 750 950 K. Biodiesel is about 543 spontaneous combustion tempera
22、ture-563 K, compressed the end of temperature than diesel combustion temperature high many, enough to make the injected fuel to the cylinder combustion angry. Spray into the cylinder of diesel, and not immediately gets angry, and pass through the physical chemical change after the angry, this time a
23、bout 0.001 0.005 seconds, called angry delay period. Therefore, in turn first to crank the top 10 35 point when the crank corner will start atomization of the fuel spray into the cylinder, and make the crank in after BDC 5 10 , in the combustion chamber to achieve maximum combustion pressure, forcin
24、g the pistons downward motion. 3. Burning inflation stroke The third stroke-burning inflation. In this stroke began, most of the spray into the combustion chamber are burning fuel. When burning give off a lot of heat, so the gas pressure and temperature will increase sharply, the pistons in high tem
25、perature and high pressure gas under the role of downward motion, and through even the stem make crankshaft, foreign doing work. So this one stroke is called work or working stroke. As the piston downline, air cylinder of the volume increased, and the gas pressure drop, working stroke on the piston
26、step to the next point, exhaust valve open end. In animation, the length of the work pressure changes that line up part of the said in cylinders when fuel combustion of pressure grew sharply, highest maximum combustion pressure Pz said, this point pressure and temperature for: Pz = 6 15 MPa, Tz = 18
27、00 2200 K, maximum combustion pressure and compression of the pressure than (Pz/Pc), called combustion pressure increase than, with said. According to different types of diesel engines, in the most off when the scope of the prison value as follows: = Pz/Pc = 1.2 2.5.Four. Exhaust stroke The fourth s
28、troke-exhaust. The function of the exhaust stroke is the expansion of the waste gas row after go out, so that filling the fresh air, for the next cycle of inlet make preparation. When work stroke, the piston moves to the next point near the exhaust valve open, the pistons in the crankshaft and conne
29、cting rod drive, the next check point by point up the sport, and put out the waste gas cylinder. Because there is resistance exhaust system, so in exhaust stroke began, in the air and gas pressure than the atmospheric pressure is high 0.025-0.035 MPa, its temperature Tb = 1000 1200 K. In order to re
30、duce exhaust the piston moves when the resistance, exhaust valve check before the next point opened. Exhaust valve is opened, with certain pressure gas cylinder immediately rushed out of the cylinder pressure to drop quickly, so that when the piston to move up, the waste gas cylinders on the piston
31、uplink row out. In order to use the air exhaust gas discharge inertia make clean, exhaust valve in BDC later just shut down. In animation, the exhaust stroke curve said in process of exhaust, and the gas pressure in cylinder is almost constant, but a slightly higher than the atmospheric pressure. Th
32、e end of the exhaust stroke Pr pressure about 0.105 0.115 MPa, residual gas temperature Pr is about 850 K. Because, the exhaust valve is in early open late shut, So in the end and air exhaust stroke at the beginning of the stroke, the pistons in near BDC one time into, exhaust valve and open, this t
33、ime with the crankshaft corner to say, called the valve overlapping Angle. After the exhaust stroke and began to air intake stroke, so the whole work cycle is in accordance with the above process is repeated. Because the diesel engine work cycle by four piston stroke that two of the crankshaft turn
34、finished, it is called four stroke diesel engine. In the four stroke diesel engine four stroke, only the third stroke that strong to generate power at foreign energy, and the rest of the three stroke is the preparation process power consumption. Therefore in single-cylinder diesel engine must be ins
35、talled the flywheel, use the flywheel rotation inertia, and the crankshaft four stroke in continuous and even ground operation. 装载机发动机的工作原理1 二冲程柴油机的工作原理 通过活塞的两个冲程完成一个工作循环的柴油机称为二冲程柴油机，油机完成一个工作循环曲轴只转一圈，与四冲程柴油机相比，它提高了作功能力，在具体结构及工作原理方面也存在较大差异。 二冲程柴油机与四冲程柴油机基本结构相同，主要差异在配气机构方面。二冲程柴油机没有进气阀，有的连排气阀也没有，而是在气缸下
36、部开设扫气口及排气口； 或设扫气口与排气阀机构。并专门设置一个由运动件带动的扫气泵及贮存压力空气 的扫气箱，利用活塞与气口的配合完成配气，从而简化了柴油机结构。图是二冲程柴油机工作原理图。扫气泵附设在柴油机的一侧，它的转子由柴油机带动。空气从泵的吸入吸入，经压缩后排出，储存在具有较大容积的扫气箱中，并在其中保持一定的压力。现以图说明二冲程柴油机的工作 原理。 一，燃烧膨胀及排气冲程： 燃油在燃烧室内着火燃烧，生成高温高压燃气。活塞在燃气的推动下，由上止点 向下运动，对外作功。活塞下行直至排气口打开（此时曲柄在点位置，此时燃气 膨胀作功结束，气缸内大量废气靠自身高压自由排气，从排气口排人到排气管
37、。 当气缸内压力降至接近扫气压力时（一般扫气箱中的扫气压力为0-12，下行活塞把扫气口3打开（此时曲柄在点4的位置，扫气空气进入气缸，同时把气缸内的废气经排气口赶出气缸。活塞运行到下止点，本冲程结束，但扫气过程一直持续到下一个冲程排气口关闭（此时曲柄在点位置为止）。二，扫气及压缩冲程： 活塞由下止点向上移动，活塞在遮住扫气口之前，由扫气泵供给储存在扫气箱内的空气，通过扫气口进入气缸，气缸中的残存废气被进入气缸的空气通过排气口扫出气缸。活塞继续上行，逐渐遮住扫气口，当扫气口完全关闭后（此时曲柄在点位置，空气停止充人，排气还在进行，这阶段称为“过后排气阶段”。排气口关闭时（此时曲柄在点位置，气缸中
38、的空气就开始被压缩。当压缩至上止点前点时，喷油器将燃油喷人气缸，与高温高压的空气相混合，随即在上止点附近发火，自行着火燃烧。本冲程结束，并与前一冲程形成一个完整的工作循环。 二冲程柴油机示功图见图，其中，为喷油始点，为活塞上止点，为 燃烧终点。 二冲程柴油机与四冲程柴油机相比具有一些明显优点，当然也存在本身固有的缺点。 2 四冲程柴油机的工作原理 柴油机的工作是由进气、压缩、燃烧膨胀和排气这四个过程来完成的，这四个过程构成了一个工作循环。活塞走四个过程才能完成一个工作循环的柴油机称为四冲程柴油机。现对照上面的动画了说明它的工作理原。 一. 进气冲程 第一冲程进气，它的任务是使气缸内充满新鲜空气
39、。当进气冲程开始时，活塞位于上止点，气缸内的燃烧室中还留有一些废气。当曲轴旋转肘，连杆使活塞由上止点向下止点移动，同时，利用与曲轴相联的传动机构使进气阀打开。 随着活塞的向下运动，气缸内活塞上面的容积逐渐增大：造成气缸内的空气压力低于进气管内的压力，因此外面空气就不断地充入气缸。进气过程中气缸内气体压力随着气缸的容积变化的情况如动画所示。图中纵坐标表示气体压力P，横坐标表示气缸容积Vh(或活塞的冲S)，这个图形称为示功图。图中的压力曲线表示柴油机工作时，气缸内气体压力的变化规律。从土中我们可以看出进气开始，由于存在残余废气，所以稍高于大气压力P0。在进气过程中由于空气通过进气管和进气阀时产生流
40、动阻力，所以进气冲程的气体压力低于大气压力，其值为0.0850.095MPa，在整个进气过程中，气缸内气体压力大致保持不变。当活塞向下运动接近下止点时，冲进气缸的气流仍具有很高的速度，惯性很大，为了利用气流的惯性来提高充气量，进气阀在活塞过了下止点以后才关闭。虽然此时活塞上行，但由于气流的惯性，气体仍能充人气缸。 二. 压缩冲程 第二冲程压缩。压缩时活塞从下止点间上止点运动，这个冲程的功用有二，一是提高空气的温度，为燃料自行发火作准备：二是为气体膨胀作功创造条件。当活塞上行，进气阀关闭以后，气缸内的空气受到压缩，随着容积的不断细小，空气的压力和温度也就不断升高，压缩终点的压力和湿度与空气的压缩
41、程度有关，即与压缩比有关，一般压缩终点的压力和温度为：Pc48MPa,Tc750950K。柴油的自燃温度约为543563K，压缩终点的温度要比柴油自燃的温度高很多，足以保证喷入气缸的燃油自行发火燃烧。喷入气缸的柴油，并不是立即发火的，而且经过物理化学变化之后才发火，这段时间大约有0.0010.005秒，称为发火延迟期。因此，要在曲柄转至上止点前1035曲柄转角时开始将雾化的燃料喷入气缸，并使曲柄在上止点后510时，在燃烧室内达到最高燃烧压力，迫使活塞向下运动。 三. 燃烧膨胀冲程 第三冲程燃烧膨胀。在这个冲程开始时，大部分喷入燃烧室内的燃料都燃烧了。燃烧时放出大量的热量，因此气体的压力和温度便
42、急剧升高，活塞在高温高压气体作用下向下运动，并通过连秆使曲轴转动，对外作功。所以这一冲程又叫作功或工作冲程。随着活塞的下行，气缸的容积增大，气体的压力下降，工作冲程在活塞行至下止点，排气阀打开时结束。在动画中，工作冲程的压力变化这条线上升部分表示燃料在气缸内燃烧时压力的急剧升高，最高点表示最高燃烧压力Pz，此点的压力和温度为：Pz615MPa， Tz18002200K ，最高燃烧压力与压缩终点压力之比(PzPc)，称为燃烧时的压力升高比， 用表示。根据柴油机类型的不同，在最大功牢时值的范围如下：PzPc1.22.5。 四. 排气冲程 第四冲程排气。排气冲程的功用是把膨胀后的废气排出去，以便充填
43、新鲜空气，为下一个循环的进气作准备。当工作冲程活塞运动到下止点附近时，排气阀开起，活塞在曲轴和连杆的带动下，由下止点向上止点运动，并把废气排出气缸外。由于排气系统存在着阻力，所以在排气冲程开始时，气缸内的气体压力加比大气压力高0.0250.035MPa，其温度Tb10001200K。为了减少排气时活塞运动的阻力，排气阀在下止点前就打开了。排气阀一打开，具有一定压力的气体就立即冲出缸外，缸内压力迅速下降，这样当活塞向上运动时，气缸内的废气依靠活塞上行排出去。为了利用排气时的气流惯性使废气排出得干净，排气阀在上止点以后才关闭。在动画中，排气冲程曲线表示在排气过程中，缸内的气体压力几乎是不变的，但比
44、大气压力稍高一些。排气冲程终点的压力Pr约为0.1050.115MPa,残余废气的温度Pr约为850960K。由于进、排气阀都是早开晚关的；所以在排气冲程之末和进气冲程之初，活塞处于上止点附近时，有一段时间进、排气阀同时开起，这段时间用曲轴转角来表示，称为气阀重迭角。排气冲程结束之后，又开始了进气冲程，于是整个工作循环就依照上述过程重复进行。由于这种柴油机的工作循环由四个活塞冲程即曲轴旋转两转完成的，故称四冲程柴油机。在四冲程柴油机的四个冲程中，只有第三冲程即工作冲强才产生动力对外作功，而其余三个冲程都是消耗功的准备过程。为此在单缸柴油机上必须安装飞轮，利用飞轮的转动惯性，使曲轴在四个冲程中连续而均匀地运转。
