回火，是指發(fā)電機(jī)組燃燒室正在燃燒的氣體火焰引燃了進(jìn)氣管中的可燃混合氣的現(xiàn)象。回火發(fā)生在發(fā)電機(jī)組運行的各個時期，發(fā)生前沒有明顯征兆，造成發(fā)動機(jī)突然停機(jī)，嚴(yán)重影響機(jī)組的運行。嚴(yán)重的回火有時造成混合器膜片損壞，維修難度和工作量都很大。

　　Backfire refers to the phenomenon where the gas flame burning in the combustion chamber of a generator set ignites the combustible mixture in the intake pipe. Backfire occurs at various stages of the operation of the generator set without obvious signs, causing the engine to suddenly shut down and seriously affecting the operation of the unit. Severe tempering sometimes causes damage to the mixer membrane, making maintenance difficult and labor-intensive.

　　1、回火原因

　　1. Reason for tempering

　　沼氣發(fā)電機(jī)組產(chǎn)生回火的原因有:①混合氣過濃:②點火時問不正確: ③氣門調(diào)整螺絲松動:④發(fā)動機(jī)缸蓋裂縫，其中混合氣過濃所造成的回火最為常見。

　　The reasons for backfire in biogas generator sets include: ① excessive mixture; ② incorrect ignition; ③ loose valve adjustment screws; ④ engine cylinder head cracks, among which backfire caused by excessive mixture is the most common.

　　2、解決回火問題

　　2. Resolve tempering issues

　　(1)由于天然氣發(fā)電機(jī)組回火具有偶然性、破壞性，容易造成發(fā)動機(jī)的混合器膜片損壞，機(jī)組突然停機(jī)，無法對回火現(xiàn)象進(jìn)行控制和觀察。分析膜片的損壞情況，發(fā)現(xiàn)片的定位方式有問題，僅靠6條螺絲緊固，至使膜片受力不均勻，容易松動和損壞。對此，提出將膜片用膠粘在混合器上的方法，讓膜片邊緣整體受力，這樣就不易損壞。粘緊后的膜片很耐用，發(fā)現(xiàn)回火后，只要將壓縮機(jī)卸載，回火就會減弱或消失。較強(qiáng)的回火可以直接停機(jī)，這樣做可贏得觀察和調(diào)整的時間。

　　(1) Due to the accidental and destructive nature of tempering in natural gas generator sets, it is easy to cause damage to the mixer diaphragm of the engine, resulting in sudden shutdown of the unit and inability to control and observe the tempering phenomenon. Analyzing the damage situation of the membrane, it was found that there was a problem with the positioning method of the membrane. Only six screws were used to tighten it, which resulted in uneven force on the membrane, making it easy to loosen and damage. In this regard, it is proposed to use adhesive to attach the membrane to the mixer, so that the edges of the membrane are subjected to overall force, which makes it less likely to be damaged. The tightly adhered membrane is very durable, but after tempering, as long as the compressor is unloaded, the tempering will weaken or disappear. Strong tempering can be stopped directly, which can buy time for observation and adjustment.

　　(2)混合氣濃度調(diào)整可以有效的避免回火現(xiàn)象的發(fā)生，在調(diào)整混合氣濃度時，首先要將混合器的負(fù)載調(diào)節(jié)螺栓擰出5圈，待發(fā)動機(jī)加載后，逐步擰進(jìn)兩側(cè)的負(fù)載調(diào)節(jié)螺絲，至發(fā)動機(jī)的混合器壓力表指針向增加一方擺動時，再擰出半圈。

　　(2) Adjusting the concentration of the mixed gas can effectively avoid the occurrence of backfire. When adjusting the concentration of the mixed gas, first unscrew the load adjustment bolt of the mixer by 5 turns. After the engine is loaded, gradually tighten the load adjustment screws on both sides until the pressure gauge pointer of the mixer of the engine swings in one direction, and then unscrew half a turn.

　　沼氣發(fā)電機(jī)組的爆震原因及故障排除

　　Reasons for detonation and troubleshooting of biogas generator sets

　　什么是爆震

　　What is detonation

　　爆震，也叫爆燃，或者敲缸，是在內(nèi)燃機(jī)中普遍存在的一種故障現(xiàn)象。爆震對應(yīng)的英語是detonation，或者干脆的叫knocking。這個名字起的如此直白，是因為其表現(xiàn)出來的現(xiàn)象也很直觀，就像有人用錘子敲打發(fā)動機(jī)傳出的聲音。

　　Detonation, also known as detonation or knocking, is a common fault phenomenon in internal combustion engines. The corresponding English for detonation is dissociation, or simply knocking. The name is so straightforward because the phenomenon it represents is also very intuitive, just like the sound of someone hitting an engine with a hammer.

　　爆震是氣缸內(nèi)的不規(guī)則燃燒。 引起爆震的原因非常多，也很復(fù)雜，但最終反映出來的一定是氣缸內(nèi)氣流紊亂，燃燒異常。用最容易理解一種情況——多點點火來舉例，正常情況下，氣缸內(nèi)由火花塞點火，燃燒產(chǎn)生的激波是從上至下，有規(guī)律的擴(kuò)散，推動活塞向下運動。

　　Detonation is irregular combustion inside the cylinder. There are many reasons that can cause detonation, and they are also complex. However, what ultimately reflects is the turbulent airflow and abnormal combustion in the cylinder. Using the easiest to understand scenario - multiple ignitions - as an example, under normal circumstances, the cylinder is ignited by a spark plug, and the shock wave generated by combustion spreads regularly from top to bottom, pushing the piston downward.

　　分布式能源, 沼氣發(fā)電機(jī)組的爆震原因及故障排除

　　Reasons and troubleshooting of detonation in distributed energy and biogas generator sets

　　但如果氣缸內(nèi)有異常的高溫點（例如積碳），能夠引燃?xì)飧變?nèi)的混合氣，這時在熱點處會產(chǎn)生不同于正常點火的另一股激波。兩股能量在氣缸里相遇時，會產(chǎn)生很高的溫度、壓力和振動，以及金屬敲擊的聲音，爆震就這么出現(xiàn)了。

　　But if there is an abnormal high temperature point (such as carbon deposition) inside the cylinder, it can ignite the mixture inside the cylinder, and at this point, another shock wave different from normal ignition will be generated. When two energy sources meet in a cylinder, they generate high temperatures, pressures, vibrations, and the sound of metal striking, resulting in detonation.

　　分布式能源, 沼氣發(fā)電機(jī)組的爆震原因及故障排除

　　Reasons and troubleshooting of detonation in distributed energy and biogas generator sets

　　其他原因引起的爆震在現(xiàn)象的細(xì)節(jié)上會有所不同，但大體上都表現(xiàn)為燃燒不受控。

　　Knocking caused by other reasons may vary in the details of the phenomenon, but generally manifests as uncontrolled combustion.

　　爆震的現(xiàn)象和后果

　　Phenomenon and consequences of detonation

　　前面說過，爆震是一種異常的燃燒，時常會伴隨著提前點火。內(nèi)燃機(jī)的點火時間非常重要，其目的之一是控制缸溫和排放。爆燃和提前點火都會導(dǎo)致異常的高溫、高壓和振動，兩者疊加時后果更為嚴(yán)重。

　　As mentioned earlier, detonation is an abnormal combustion that often accompanies pre ignition. The ignition time of internal combustion engines is very important, and one of their purposes is to control cylinder temperature and emissions. Both detonation and premature ignition can cause abnormal high temperature, high pressure, and vibration, and the consequences are more severe when the two are combined.

　　以某一個機(jī)型來舉例，正常運行時缸內(nèi)最高溫度約1500℃，壓力約為90bar，而在提前點火加爆燃的情況下，溫度可達(dá)約2500℃，壓力可達(dá)約200bar。

　　Taking a certain model as an example, during normal operation, the maximum temperature inside the cylinder is about 1500 ℃ and the pressure is about 90 bar. However, in the case of pre ignition and detonation, the temperature can reach about 2500 ℃ and the pressure can reach about 200 bar.

　　分布式能源, 沼氣發(fā)電機(jī)組的爆震原因及故障排除

　　Reasons and troubleshooting of detonation in distributed energy and biogas generator sets

　　不同運行狀態(tài)下的氣缸內(nèi)溫度

　　Temperature inside the cylinder under different operating conditions

　　分布式能源, 沼氣發(fā)電機(jī)組的爆震原因及故障排除

　　Reasons and troubleshooting of detonation in distributed energy and biogas generator sets

　　不同運行狀態(tài)下的氣缸內(nèi)壓力

　　Cylinder pressure under different operating conditions

　　出現(xiàn)爆震時，高溫和高壓會對氣缸相關(guān)的零部件造成損壞，如活塞、氣門、缸套等。在極端情況下，爆震導(dǎo)致的高溫會使氣缸無法及時散熱，最終缸內(nèi)平均溫度超過鋁的熔點660℃（正常的平均溫度在300-400℃），使活塞熔毀。

　　When detonation occurs, high temperature and high pressure can cause damage to cylinder related components such as pistons, valves, cylinder liners, etc. In extreme cases, the high temperature caused by detonation can prevent the cylinder from dissipating heat in a timely manner, resulting in an average temperature inside the cylinder exceeding the melting point of aluminum by 660 ℃ (the normal average temperature is 300-400 ℃), causing the piston to melt.

　　分布式能源, 沼氣發(fā)電機(jī)組的爆震原因及故障排除

　　Reasons and troubleshooting of detonation in distributed energy and biogas generator sets

　　因爆震熔毀的活塞

　　The piston melted down due to detonation

　　爆震是發(fā)動機(jī)里最為嚴(yán)重的故障類型之一，各個廠家對于爆震均如臨大敵。以MWM為例，出現(xiàn)爆震的故障后，會給出一個罕見的故障信息：“嚴(yán)重故障！檢查發(fā)動機(jī)！”。這種情況下要求用內(nèi)窺鏡檢查氣缸內(nèi)部，并目視檢查連桿和曲軸，確認(rèn)全部沒有異常才可以再次開機(jī)。如果在運行記錄中發(fā)現(xiàn)沒有做出足夠的檢查，又因為爆震導(dǎo)致機(jī)組損壞，那么即使在質(zhì)保期內(nèi)，也是有大概率被拒賠的。

　　Knocking is one of the most serious types of engine malfunctions, and various manufacturers treat knocking as a major enemy. Taking MWM as an example, when a detonation fault occurs, a rare fault message will be given: "Serious fault! Check the engine!". In this case, it is required to use an endoscope to inspect the inside of the cylinder and visually check the connecting rod and crankshaft to confirm that there are no abnormalities before restarting. If it is found in the operation records that insufficient inspection has been carried out and the unit has been damaged due to detonation, there is a high probability of being refused compensation even within the warranty period.

　　爆震的原因

　　Reasons for detonation

　　1、燃?xì)赓|(zhì)量不合格

　　1. Unqualified gas quality

　　燃?xì)獾臒嶂颠^高、甲烷值（MN）過低都會導(dǎo)致爆燃。

　　Excessive calorific value and low methane value (MN) of gas can both lead to detonation.

　　沼氣發(fā)電機(jī)組都會根據(jù)現(xiàn)場使用的燃料進(jìn)行調(diào)校，對于熱值偏高、甲烷值偏低的燃?xì)?，一般采用降低功率、推遲點火角的方式來應(yīng)對。

　　Biogas generator sets are calibrated according to the fuel used on site. For gas with high calorific value and low methane value, the method of reducing power and delaying ignition angle is generally adopted.

　　如果是運行過程中燃?xì)獬煞殖霈F(xiàn)變化，機(jī)組本身會有一定的適應(yīng)能力，但超出范圍后，就會出現(xiàn)爆震，直至保護(hù)停機(jī)。

　　If there is a change in gas composition during operation, the unit itself will have a certain degree of adaptability, but if it exceeds the range, detonation will occur until the protection shutdown.

　　關(guān)于燃?xì)獾臒嶂岛图淄橹?，請看這里： 燃?xì)赓|(zhì)量之甲烷值

　　Regarding the calorific value and methane value of gas, please refer to here: Methane value of gas quality

　　2、點火異常

　　2. Abnormal ignition

　　點火角設(shè)置不合理，導(dǎo)致了提前點火，這種情況相對好處理，機(jī)組本身會進(jìn)行一部分調(diào)整，或者手動調(diào)整到合理值即可。

　　The unreasonable ignition angle setting resulted in premature ignition, which is relatively easy to handle. The unit itself will make some adjustments or manually adjust it to a reasonable value.

　　火花塞或點火變壓器等部件異常也有可能導(dǎo)致爆震。

　　Abnormal components such as spark plugs or ignition transformers may also cause detonation.

　　3、混合氣濃度、溫度、壓力異常

　　3. Abnormal concentration, temperature, and pressure of the mixed gas

　　混合氣溫度高一般可歸結(jié)為進(jìn)氣溫度高和中冷器溫度高，也就是缸套水、中冷水入口溫度高。

　　High mixture temperature can generally be attributed to high intake temperature and high intercooler temperature, that is, high inlet temperature of cylinder liner water and intercooler water.

　　混合氣濃度過高，一般是空燃比調(diào)節(jié)系統(tǒng)設(shè)置不合理或出現(xiàn)故障，另外還有一種可能是燃?xì)獬煞职l(fā)生了變化。

　　If the concentration of the mixture is too high, it is generally due to unreasonable or malfunctioning air-fuel ratio adjustment system settings, or another possibility is that the gas composition has changed.

　　4、氣缸內(nèi)有局部熱點

　　4. There is a local hot spot inside the cylinder

　　活塞、缸套、氣門均有可能出現(xiàn)局部熱點，最常見的一種情況是積碳，最終會導(dǎo)致多點點火，也就是前面舉例的那種情況。這種熱點并不是太容易找出來，有時需要解體后仔細(xì)檢查才能發(fā)現(xiàn)。

　　Pistons, cylinder liners, and valves may all experience local hot spots, the most common of which is carbon buildup, ultimately leading to multi-point ignition, as exemplified earlier. This kind of hotspot is not easy to find, sometimes it requires careful inspection after disassembly to discover.

　　5、傳感器或線路導(dǎo)致的假信號

　　5. False signals caused by sensors or circuits

　　有時會因為傳感器和線路的原因出現(xiàn)假信號，這種情況不難排除。但需要注意的是，即使預(yù)判是假故障，在處理時也必須按照真爆燃的流程處理，否則一旦判斷失誤，后果可能很嚴(yán)重。

　　Sometimes false signals may occur due to sensor and wiring issues, which can be easily ruled out. However, it should be noted that even if it is predicted to be a false fault, it must be handled according to the true explosion process, otherwise, if the judgment is wrong, the consequences may be very serious.

　　6、另外如果發(fā)動機(jī)設(shè)計不合理，也會導(dǎo)致爆震的趨勢加大，但如果是成熟的機(jī)型，這些情況基本可以忽略。這幾種情況有渦輪增壓壓力過高、壓縮比過大、輸出功率過大等。

　　6. In addition, if the engine design is unreasonable, it can also lead to an increased tendency for detonation, but if it is a mature model, these situations can be basically ignored. These situations include high turbocharging pressure, excessive compression ratio, and high output power.

　　爆震的檢測

　　Detection of detonation

　　爆震傳感器通過檢測氣缸的壓力和振動進(jìn)行判斷。檢測到異常信號后，根據(jù)信號的強(qiáng)度，評估出爆震等級，然后給出相應(yīng)的應(yīng)對措施（自動調(diào)整、報警、停機(jī)）。

　　The knock sensor determines by detecting the pressure and vibration of the cylinder. After detecting abnormal signals, the knock level is evaluated based on the strength of the signal, and corresponding measures are given (automatic adjustment, alarm, shutdown).

　　早期的爆震檢測系統(tǒng)不夠完善，在發(fā)動機(jī)運行期間，如果真的用一個錘子去敲一下傳感器附近，甚至機(jī)組本身運行產(chǎn)生的一些振動，都是有可能導(dǎo)致誤報爆震停機(jī)的。由于在四個沖程中，爆震只會發(fā)生在點火沖程，現(xiàn)在的爆震檢測一般都做了優(yōu)化，只檢測點火沖程那幾十毫秒，大大減少了誤報的可能性。

　　The early knock detection system was not perfect enough. During engine operation, if a hammer is really used to knock near the sensor, or even some vibrations generated by the operation of the unit itself, it may cause false alarms of knock shutdown. Due to the fact that detonation only occurs during the ignition stroke in the four strokes, current detonation detection has generally been optimized to only detect the few tens of milliseconds of the ignition stroke, greatly reducing the possibility of false alarms.

　　有些機(jī)型每個缸配置一個爆震傳感器，也有一些機(jī)型每相鄰的兩個缸共用一個傳感器。由于點火順序的存在，相鄰的兩個缸永遠(yuǎn)不會同時處在點火沖程，所以共用也不會有什么問題。

　　Some models are equipped with a knock sensor per cylinder, while others have a sensor shared between adjacent cylinders. Due to the existence of ignition sequence, adjacent cylinders will never be on the ignition stroke at the same time, so there will be no problem with sharing.

　　爆震故障排除

　　Troubleshooting of detonation faults

　　1、 推遲點火角

　　1. Delay ignition angle

　　推遲點火角可以在一定程度上降低爆震的烈度。出現(xiàn)爆震后，發(fā)動機(jī)的控制系統(tǒng)一般會自動推遲點火角，但調(diào)整到一定限度后，如果爆震依舊存在，就會給出報警。這時人工還可以再次嘗試調(diào)整點火角，但一般都不會有多明顯的效果了。

　　Delaying the ignition angle can reduce the intensity of detonation to a certain extent. After detonation occurs, the engine control system usually automatically delays the ignition angle, but if detonation still exists after adjusting to a certain limit, an alarm will be given. At this point, manual adjustment of the ignition angle can be attempted again, but generally it will not have a significant effect.

　　2、 降低功率

　　2. Reduce power

　　輸出功率越高，氣缸內(nèi)壓力越大，爆震程度也相對越高，因此降低功率也會減輕爆震的程度。對于一些質(zhì)量不好的氣，發(fā)電機(jī)組會有功率折損，鎖住最大輸出功率，其實就是因為爆震的關(guān)系。

　　The higher the output power, the greater the pressure inside the cylinder, and the relatively higher the degree of detonation. Therefore, reducing power will also alleviate the degree of detonation. For some low-quality gases, the generator set may experience power loss and lock in the maximum output power, which is actually due to detonation.

　　3、 替換爆震傳感器，如果爆震現(xiàn)象跟著傳感器走，則有可能是假信號。檢查/調(diào)整/替換傳感器本體、接線、爆震控制模塊等。

　　3. Replace the knock sensor. If the knock phenomenon follows the sensor, it may be a false signal. Check/adjust/replace sensor body, wiring, knock control module, etc.

　　4、 如果爆震不跟著傳感器走，則有可能是真爆震，檢查/調(diào)整/替換火花塞、點火變壓器、氣門間隙等。

　　4. If the detonation does not follow the sensor, it may be true detonation. Check/adjust/replace spark plugs, ignition transformers, valve clearances, etc.

　　5、 下狠手，檢查/調(diào)整/替換氣門搖臂、挺桿等一系列和點火相關(guān)的部件。

　　5. Use brute force to inspect/adjust/replace a series of ignition related components such as valve rocker arms and lifters.

　　6、 下殺手，檢查/替換缸套、活塞、連桿等。

　　6. Kill someone and inspect/replace cylinder liners, pistons, connecting rods, etc.

　　第7條并不完全是開玩笑，在處理內(nèi)燃機(jī)故障的時候，爆燃相關(guān)的事情是最容易出現(xiàn)靈異事件的，所謂靈異，就是查了半天哪都沒問題但就是有故障，或者好了也不知道為什么就好了。

　　Article 7 is not entirely a joke. When dealing with internal combustion engine failures, incidents related to explosions are the most prone to paranormal events. The so-called paranormal events refer to situations where after searching for a long time without any problems, there is still a malfunction, or when it is resolved, it is not clear why.

　　小編親身經(jīng)歷過一次，新機(jī)，第一次開機(jī)就出現(xiàn)爆震，而且程度不輕，把能查的查了個遍，然后呼叫援軍該拆的拆該換的換，一直解決不了。最后真的沒轍了，扔下這臺機(jī)器先做別的事。放了一周，再回來開機(jī)，無故障一次通過，直到負(fù)載測試，交付運行，都沒再出現(xiàn)過爆震。那次的事情雖然算是解決了，但小編從此落下一個后遺癥，一聽到爆震倆字就頭疼。

　　I have personally experienced once that a new machine experienced a detonation upon first startup, and the degree of detonation was not mild. I searched everything that could be checked and then called for reinforcements to dismantle and replace what needed to be dismantled, but I couldn't solve the problem. In the end, there was really no other choice but to abandon this machine and do something else first. After leaving it for a week, I returned to start it up and passed it without any faults. Until the load test and delivery for operation, there were no more explosions. Although that incident was considered resolved, the editor has had a lingering effect since then. Whenever he hears the word 'explosion', he gets a headache.

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