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柴油发电机组排气烟色故障分析

文字:[大][中][小] 手机页面二维码 2016/10/21     浏览次数:    

转载自2016-10-04 中国发电机组协会

 

柴油机工作温度正常情况下,所排出的烟色应该是无色或淡灰色,所谓无色不是完全无色,不能像汽油机那样无色,而是在无色中伴有淡淡的灰色,这是正常排气烟色。柴油机在怠速时排气烟色可能重一些,在高速、高负荷时也可能重一些,要留意观察正常排气烟色,才能对非正常的排气烟色进行判定和分析。柴油机燃料完全燃烧后,正常颜色一般为淡灰色,负荷略重时为深灰色。柴油机在工作中,会经常出现冒烟现象,柴油机排烟有黑烟、蓝烟、白烟和灰色四种,它们是判定柴油机故障的条件之一,具体分析如下:

一、排气冒黑烟(碳烟)

黑烟又痴辜烟,柴油机排气冒黑烟最主要原因是燃料混合气过浓,可燃混合气形成不良或燃烧不完善等原因造成的。柴油机在高温、高压燃烧条件下,局部缺氧、裂解并脱氢而形成的以碳为主要成分的固体微小颗粒,是燃烧室内燃料燃烧不完全的表现。由于柴油机是非均质燃烧,燃烧室内各区域的化学反应条件是不一致的,而且随着时间而变化的,所以黑烟很可能是由很多不同途径天生的。柴油是复杂的碳氢化合物,喷进燃烧室内未燃烧的柴油受高温分解,形成炭黑,排气时随同废气一起排出形成玄色烟雾。黑烟是不完全燃烧产物,是烃燃烧在高温缺氧情况下裂解过程释出并聚合而成的。某些情况下燃油喷射在燃烧室壁面上,形成液态油膜,油膜是最后蒸发的一部分,它的燃烧取决于其蒸发速度和燃料蒸气与氧的混合速度。假如四周气体中氧的浓度太低,或混合的速度不够时,从油膜蒸发的燃料气体将被分解,并产生未燃烃、不完全氧化产物和黑烟。

柴油机燃烧过程中黑烟的产生可以概括为三个阶段——成核阶段、单粒阶段、单粒的燃烧消失或附聚成更大絮团。影响其天生的主要原由于:

1、活塞环、气缸套等磨损 气门、活塞环、气缸套磨损后,引起压缩压力不足以及机油上窜燃烧试冬负气缸在压缩行程结束时,混合气混合的正常比例改变,使燃油在无氧条件下燃烧,燃烧过程轻易产生积炭,排出的废气形成大量玄色烟雾。

2、燃烧室外形改变燃烧室外形因制造质量及长期使用导致技术状况下降,使压缩余缝过大、过小以及活塞位置装错,都会使燃烧室外形和容积改变,从而影响燃油与空气混合质量,使燃油燃烧条件变坏。

3、喷油器工作不良,柴油机排气烟度与燃油雾化品质的关系密切,在柴油机喷油过程中,每次喷油临结束时,喷油压力下降,雾化质量差,使液滴直径比主要喷射阶段的油滴大5倍(体积约增大100倍),这些油滴蒸发与燃烧的时间短,四周氧的浓度低,轻易产生碳烟。喷油器不雾化、雾化不良或滴油,使燃料不能充分地与气缸内的空气混合,也不能完全燃烧。由喷油器工作不良引起的排黑烟现象在柴油机低速运转时较为明显,由于低速运转时气缸内进气涡流较弱,油滴或油束被气流冲散的可能性减少并且停留的时间较长,更轻易形成碳黑排出。)

4、供油量过大供油量过大,使进进汽缸内的油量增多,造成油多气少燃油燃烧不完全。另外,工作负荷过重、燃油质量低劣、工作温度过低也会引起排气冒黑烟,柴油机中燃料的高温裂解反应是不可避免的,特别是在空间混合燃烧的柴油机中,由于高温气体包围着液态的油滴,造成了有利于裂解反应的条件,因此在燃烧初期产生了大量的碳粒,这一点已为燃烧过程的高速摄影所证实。柴油机在正常燃烧时,在排气门打开以前,燃烧初期所形成的大量碳粒可以基本烧完,排气基本上是无烟的。只是在某些不利工况下,碳粒不能及时燃烧反而团圆吸附,在气缸中和排气过程中形成更大的碳烟粒子或絮团,使排气冒黑烟。

5、供油提前角调整不当

(1)供油提前角过大,燃油过早喷进燃烧室内,由于此时气缸内压力温度较低,燃料不能着火燃烧,当活塞上行,气缸内达到一定压力和温度,可燃混合气燃烧。在直喷式柴油机中,当其它参数不变时,加大喷油提前角可以降低排气烟度。由于加大喷油提前角会使滞燃期加长,使着火前喷进气缸的油量增加,预混合量增加,预混合气增多,加快了燃烧速度,燃烧可较早结束,从而使主燃期的形成碳粒具有较高的温度和高温下停留较多的时间,有利于碳粒氧化消失。然而过早的喷油增加了预混燃料量,使柴油机工作粗暴,燃烧噪音增大,并引起较大的机械负荷,以及较多的黑烟(COX)排放。

(2)供油提前角过小,喷进汽缸内的燃油过迟,一部分燃料来不及形成可燃混合气就被分离或排出,致使部分在排气管中随废气排出的燃油料受高温分解、燃烧,形成黑烟随废气一同排出。

二、排气冒蓝烟

排气冒蓝烟,一般情况下是柴油机使用日久,慢慢开始烧机油引起的,随着蓝色烟雾的加重,烧机油越来越多,就应考虑维修柴油机了。有时燃油中混有水分,或有水分漏进燃烧室中,引起燃烧的改变,柴油机会冒浅蓝色烟。影响其天生的主要因素为:

1、空气滤清器阻塞,进气不畅或油盆内油面过高(油浴式空气滤清器),使进进汽缸内的气量减少,燃油混合气正常比例改变,造成油多气少燃油燃烧不完全,也会引起排气冒蓝烟。

2、油底壳内润滑油加进过多,柴油机运行中润滑油易窜进燃烧室。

3、长期低负荷(标定功率的40%以下)运转,活塞与缸套之间的间隙过大,使油底壳内润滑油轻易窜进燃烧试冬与气缸中的燃料混合气混合,改变混合气正常比例,燃烧不完全,引起排气冒蓝烟。

4、活塞环卡住或磨损过多,弹性不足,安装时活塞环倒角方向装反,使机油进进燃烧试冬润滑油燃烧后产生蓝色水气烟雾排出。

5、在机体通向气缸盖油道四周的气缸垫烧毁,活塞、气缸套磨损以及活塞环对口等状况将致使润滑油上窜燃烧试冬并与燃油混合气一同燃烧。

三、排气冒白烟

白烟是指排气烟色为白色,它与无色不同,白色是水蒸气的白色,表示排烟中含有水分或含未燃烧的燃油成分。白烟呈液珠状态,和蓝烟相比较直径稍大,一般大于1μm。在光的折射下呈白色,柴油机的白烟是未燃烃(含燃油和润滑油)、水蒸气以及不完全燃烧的中间产物(如含氧碳氢),除水蒸气外,它们也都属于微粒范畴。柴油机在刚起动时或冷机状态时,排气管冒白烟,是由于柴油机气缸内温度低油气蒸发而形成,冬季尤为明显。柴油机在严冷天气运行时,柴油机温度低,排气管温度也低,有水蒸气排气凝聚成水气形成白色排烟,是正常现象。若当柴油机温度正常,排气管温度也正常时,仍然排出白色烟雾,说明柴油机工作不正常,可判定为柴油机故障。影响其天生的主要因素为:

6、柴油机刚启动时,个别气缸内不燃烧(特别是冬天),未燃烧的燃油混合气随其它工作缸的废气排出形成水气烟雾。

7、活塞、气缸套等磨损严重引起压缩力不足,造成燃烧不完全。

8、燃油中有水份和空气。水和空气随着燃油喷射进气缸形成不均匀燃油混合气,燃烧不完全,产生大量的未燃烃排出机外。

9、气缸套有裂纹或气缸垫损坏,随着冷却水温度和压力的升高,冷却水进进气缸。排气时形成轻易形成水雾或水蒸气

10、供油提前角过小。活塞上行至气缸顶前喷进气缸的燃油过少,形成较稀的可燃混合气,过迟的喷油减少了预混燃料量,预混合量减少。预混合气减少,降低了燃烧速度,燃烧结束较晚,燃烧形成大量的水气烟雾。

四、排气冒灰烟

排气冒淡灰色烟,柴油机工作还算正常,但烟雾颜色加重呈灰色或接近于玄色就不正常了,除了上述排烟玄色的原因外,还可能有进气不畅即空气供给不好的原因。当取下进气空气滤清器后,排气烟色由深变浅甚至变为无色时,就是空气滤清器堵塞了,应检查引起进气不畅的原因。

喷油器雾化不良,喷油压力过低,有滴油现象。在气缸中燃油混合气不均匀,燃烧不完全,产生大量的未燃烃,排气时轻易形成水雾或水蒸气。

Failure Analysis of diesel generator set exhaust smokecolor

Diesel engine operating temperature under normalcircumstances, the color of the exhaust fumes should be colorless or pale gray,the so-called colorless is not completely colorless, not like the gasolineengine as colorless, but accompanied by a touch of gray in colorless, which isnormal exhaust smoke color. Diesel engine at idle, the exhaust smoke color maybe heavier, high-speed, high load may be heavier, to observe and normal exhaustsmoke color can conducted to determine and analyze non-normal exhaust smokecolor. Complete combustion of diesel fuel, the normal color is generally lightgray, the load is slightly heavier than dark gray. Diesel engine at work, oftensmoke in diesel engine exhaust smoke, blue smoke, white smoke and gray four,they are one of the conditions that determine the diesel engine failure,specific analysis is as follows:

An exhaust black smoke (soot)

Another crazy black smoke the Gu smoke, diesel exhaustblack smoke most important reason is the fuel mixture is too thick, combustiblemixture formation causes bad or burning imperfect. The diesel engine in thehigh-temperature, high pressure combustion conditions, local hypoxia, crackingand dehydrogenation and the formation of tiny carbon as the main ingredient ofsolid particles, the combustion chamber fuel incomplete combustion performance.Diesel non-homogeneous combustion, chemical reaction conditions of each regionof the combustion chamber is inconsistent, and change over time, so the blacksmoke is likely to by many different ways natural. Diesel is a complexhydrocarbons, sprayed into the combustion chamber unburned diesel fuel bypyrolysis, the formation of carbon black, along with the exhaust gas when theexhaust discharge to the formation of black smoke. Black smoke is a product ofincomplete combustion of hydrocarbon combustion under anoxic conditions in thehigh-temperature pyrolysis process of release and polymerization. Fuelinjection in the combustion chamber wall, under certain circumstances, theformation of a liquid film, the film is part of the final evaporation,combustion depends on the evaporation rate of fuel vapor and oxygen mixturevelocity. Four weeks the concentration of oxygen in the gas is too low, or amixture of speed is not enough, the film evaporation from thefuel gas will decompose and produce unburned hydrocarbons, incomplete oxidationproducts and smoke.

Black smoke diesel engine combustion process inherentlycan be summarized into three stages - nucleation stage, single grain stage,single grain of burning disappears or agglomeration into larger floc. Affectits natural original due to:

    1, piston rings, cylinder linerwear of valve, piston rings, cylinder liner wear, caused by compressionpressure is insufficient, and the channeling of the oil burning test winternegative cylinder at the end of the compression stroke, the normal change inratio of the mixture is mixed, so that the fuel in the absence of oxygen underthe conditions of combustion, the combustion process is easily produce coke,the exhaust air from the formation of a large number of black smoke.

    2, the shape of the combustionchamber to change the combustion chamber shape because of manufacturing qualityand long-term use of the technical conditions of the compression I sew toolarge, too small, and the piston position is wrong, will cause the combustionchamber shape and volume changes, thus affecting the fuel and air mixture thequality of fuel combustion conditions deteriorate.

    Bad injector diesel engine exhaustsmoke and fuel atomization quality is closely related to diesel fuel injectionprocess, the end of each injector Pro, injection pressure decreased, the poorquality of atomization, so that the droplets diameter 4-5 times larger than themain injection phase of the oil droplets (volume about 100 times larger), thesedroplets evaporate burning time is short and the surrounding oxygenconcentration is low, and easily produce soot. Injector atomization,atomization, poor or drop of oil, fuel and air mixture within the cylinder cannot be fully nor complete combustion. Injector bad work caused by the emissionof black smoke phenomenon is more obvious when the diesel engine at low speed, low speed cylinder intakeswirl is weak, reducing the possibility of oil droplets or oil beam by air tobreak up and stay longer than long, the more easily the formation of carbonblack discharge. )

    4, oil overload oil overload, the increase in theamount of fuel into the cylinder, resulting in incomplete combustion of fueloil and more gas less. In addition, work overload, poor fuel quality, operatingtemperature is too low will cause the exhaust black smoke, diesel fuel in hightemperature pyrolysis reaction is inevitable, especially in the spacecombustion of diesel, due to the high temperature gas surrounded liquiddroplets, resulting in the cracking reaction conditions, so early in thecombustion generated a lot of carbon particles, this has been confirmed byhigh-speed photography of the combustion process. The diesel engine in thenormal combustion, before the exhaust valve opens, burning the early formationof carbon particles can basically burn the exhaust is basically a smoke-free.Only in certain adverse conditions, carbon can not be timely burning butreunion adsorption www.zfdjz.com larger soot particles or floc formed in thecylinder and exhaust process, so that the exhaust black smoke.

    5, the fuel supply advance angle adjustment improper

(1) fuel supply advance angle is too large, fuel premature sprayed into the combustionchamber, low pressure and temperature within the cylinder, the fuel is notignited, reaches a certain pressure and temperature within the cylinder whenthe piston upward, combustible mixture combustion. In direct injection dieselengine, when the other parameters constant, increase the fuel injection advanceangle can reduce exhaust smoke. Increase the fuel injection advance angle willmake longer ignition delay period, the increase in fuel sprayed into thecylinder before ignition, premixed increased pre-mixed gas increased to speedup the combustion speed, combustion may end earlier, so that the main theformation of the combustion of carbon particles has to stay more time underhigh temperature and high temperature, carbon particle oxidation disappears.However, the increase in premature fuel injection amount of premixed fuel,diesel crude, combustion noise increased, and caused a large mechanical load,and more smoke emissions (COX).

(2) The fuel supply advance angle is too small, fuel sprayed into the cylinderlate part of the fuel is too late to formation of the combustible mixture to beseparated or discharged, causing part of exhaust gas in the exhaust pipe withthe fuel material by pyrolysis, combustion, the formation of black smoke alongwith the exhaust discharge.

    Second, the exhaust take Lanyan

Exhaust take Lanyan general diesel engine after prolonged use, and slowly beganto burn the oil caused, with the blue smoke worsens, more and more burning oil,you should consider the maintenance of diesel engines. Sometimes fuel mixedwith water, or water to leak into the combustion chamber, causing the change ofcombustion, the diesel engine will take the light blue smoke. Affect thenatural main factors:

An air filter, intake poor or oil basin oil is too high (oil bath air filter),so that the gas into the cylinder to reduce the normal change in ratio of thefuel mixture, resulting in more oil gas less incomplete combustion of fuel,will cause the exhaust to take Lanyan.

2, the lubricating oil sump added too much lubricant easy coming into thecombustion chamber diesel engine running.

3, less than 40% of long-term, low-load (rated power) operation, the gapbetween the piston and cylinder is too large, so that the lubricating oil sumpeasily flee in the fuel mixture in the combustion test of winter and thecylinder gas mixture and change the Blend gas the normal proportion ofincomplete combustion, causing the exhaust to take Lanyan.

4, the piston ring stuck or excessive wear and tear, lack of flexibility wheninstalling the direction of the piston ring chamfer hold against the oil feedinto the blue water gas smoke emissions after combustion in the trial of winteroil combustion.

5, in the body leading to the cylinder head oil passages around the cylinderpad burned piston, cylinder liner wear and piston ring counterparts conditionsresulting in lubricants Upward combustion test in winter, and with burning andfuel mixture.

    Third, the exhaust white smoke

White smoke is the exhaust smoke color white and colorless, white water vaporwhite, said exhaust contains water or containing unburned fuel components.White smoke was the state of the droplet, and blue smoke compared with thediameter slightly larger, typically greater than 1μm. Refraction of light iswhite, the white smoke of the diesel engine is unburned hydrocarbons (includingfuel and lubricant), water vapor and incomplete combustion intermediates (suchas oxygen-containing hydrocarbon), in addition to water vapor, they also belongto particle areas. The diesel engine is just starting or cooler state, theexhaust pipe white smoke is due to the low evaporative emission of dieselengine cylinder temperature formation, especially in winter. Diesel engines incold weather to run in strict diesel engine temperature is low, the exhausttemperature is low, water vapor exhaust is condensed into water vapor to form awhite smoke is normal. When the diesel engine to normal temperature, exhausttemperature is normal, still emit white smoke, indicating that the dieselengine is not working properly, can be judged to be the diesel engine fault.Affect the natural main factors:

6 diesel engine has just started within the individual cylinder combustion(especially in winter), unburned fuel mixture with the other cylinder exhaustdischarge to form water vapor smoke.

7, piston, cylinder liner wear serious cause compression force, resulting inincomplete combustion.

8, fuel, water and air. Water and air with the fuel injection into the cylinderto the formation of uneven fuel mixture, combustion is incomplete, resulting ina lot of unburned hydrocarbons discharged outside the machine.

9, the cylinder liner crack or cylinder head gasket is damaged, with thecooling water temperature, pressure, cooling water feed into the cylinder.Venting the formation of easily formation of mist or vapor

10, the fuel supply advance angle is too small. The piston up to the fuel sprayinto the cylinder before the cylinder top is too small, the formation of themore dilute the combustible mixture, the late injection to reduce the premixedfuel consumption, pre-mixed reduced. Pre-mixture is reduced, reducing thecombustion speed, combustion end of the late burning the formation of a largenumber of water vapor of smoke.

    Fourth, the exhaust take Misty

Exhaust to take light gray smoke, diesel engines work is fairly normal, but thesmoke color heavier gray or close to the xuan is not normal, in addition to thesmoke xuan of reasons, may also have poor intake air supply does not goodreason. Remove the intake air filter, exhaust smoke color deep shallow or evenbecome colorless, that is, air filter blockage, should check the cause of thereasons for poor intake.

Poor injector spray, the injection pressure is too low, drip phenomenon. Fuelmixture in the cylinder, uneven, incomplete combustion and produce largeamounts of unburned hydrocarbon exhaust easily the formation of mist or vapor.


 

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