回火，是指发电机组燃烧室正在燃烧的气体火焰引燃了进气管中的可燃混合气的现象。回火发生在发电机组运行的各个时期，发生前没有明显征兆，造成发动机突然停机，严重影响机组的运行。严重的回火有时造成混合器膜片损坏，维修难度和工作量都很大。

　　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

　　沼气发电机组产生回火的原因有:①混合气过浓:②点火时问不正确: ③气门调整螺丝松动:④发动机缸盖裂缝，其中混合气过浓所造成的回火最为常见。

　　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、解决回火问题

　　2. Resolve tempering issues

　　(1)由于天然气发电机组回火具有偶然性、破坏性，容易造成发动机的混合器膜片损坏，机组突然停机，无法对回火现象进行控制和观察。分析膜片的损坏情况，发现片的定位方式有问题，仅靠6条螺丝紧固，至使膜片受力不均匀，容易松动和损坏。对此，提出将膜片用胶粘在混合器上的方法，让膜片边缘整体受力，这样就不易损坏。粘紧后的膜片很耐用，发现回火后，只要将压缩机卸载，回火就会减弱或消失。较强的回火可以直接停机，这样做可赢得观察和调整的时间。

　　(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)混合气浓度调整可以有效的避免回火现象的发生，在调整混合气浓度时，首先要将混合器的负载调节螺栓拧出5圈，待发动机加载后，逐步拧进两侧的负载调节螺丝，至发动机的混合器压力表指针向增加一方摆动时，再拧出半圈。

　　(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.

　　沼气发电机组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，是在内燃机中普遍存在的一种故障现象。爆震对应的英语是detonation，或者干脆的叫knocking。这个名字起的如此直白，是因为其表现出来的现象也很直观，就像有人用锤子敲打发动机传出的声音。

　　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.

　　爆震是气缸内的不规则燃烧。 引起爆震的原因非常多，也很复杂，但最终反映出来的一定是气缸内气流紊乱，燃烧异常。用最容易理解一种情况——多点点火来举例，正常情况下，气缸内由火花塞点火，燃烧产生的激波是从上至下，有规律的扩散，推动活塞向下运动。

　　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, 沼气发电机组的爆震原因及故障排除

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

　　但如果气缸内有异常的高温点（例如积碳），能够引燃气缸内的混合气，这时在热点处会产生不同于正常点火的另一股激波。两股能量在气缸里相遇时，会产生很高的温度、压力和振动，以及金属敲击的声音，爆震就这么出现了。

　　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, 沼气发电机组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现象的细节上会有所不同，但大体上都表现为燃烧不受控。

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

　　爆震的现象和后果

　　Phenomenon and consequences of detonation

　　前面说过，爆震是一种异常的燃烧，时常会伴随着提前点火。内燃机的点火时间非常重要，其目的之一是控制缸温和排放。爆燃和提前点火都会导致异常的高温、高压和振动，两者叠加时后果更为严重。

　　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.

　　以某一个机型来举例，正常运行时缸内最高温度约1500℃，压力约为90bar，而在提前点火加爆燃的情况下，温度可达约2500℃，压力可达约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, 沼气发电机组的爆震原因及故障排除

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

　　不同运行状态下的气缸内温度

　　Temperature inside the cylinder under different operating conditions

　　分布式能源, 沼气发电机组的爆震原因及故障排除

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

　　不同运行状态下的气缸内压力

　　Cylinder pressure under different operating conditions

　　出现爆震时，高温和高压会对气缸相关的零部件造成损坏，如活塞、气门、缸套等。在极端情况下，爆震导致的高温会使气缸无法及时散热，最终缸内平均温度超过铝的熔点660℃（正常的平均温度在300-400℃），使活塞熔毁。

　　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, 沼气发电机组的爆震原因及故障排除

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

　　因爆震熔毁的活塞

　　The piston melted down due to detonation

　　爆震是发动机里最为严重的故障类型之一，各个厂家对于爆震均如临大敌。以MWM为例，出现爆震的故障后，会给出一个罕见的故障信息：“严重故障！检查发动机！”。这种情况下要求用内窥镜检查气缸内部，并目视检查连杆和曲轴，确认全部没有异常才可以再次开机。如果在运行记录中发现没有做出足够的检查，又因为爆震导致机组损坏，那么即使在质保期内，也是有大概率被拒赔的。

　　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、燃气质量不合格

　　1. Unqualified gas quality

　　燃气的热值过高、甲烷值（MN）过低都会导致爆燃。

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

　　沼气发电机组都会根据现场使用的燃料进行调校，对于热值偏高、甲烷值偏低的燃气，一般采用降低功率、推迟点火角的方式来应对。

　　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.

　　如果是运行过程中燃气成分出现变化，机组本身会有一定的适应能力，但超出范围后，就会出现爆震，直至保护停机。

　　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.

　　关于燃气的热值和甲烷值，请看这里： 燃气质量之甲烷值

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

　　2、点火异常

　　2. Abnormal ignition

　　点火角设置不合理，导致了提前点火，这种情况相对好处理，机组本身会进行一部分调整，或者手动调整到合理值即可。

　　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.

　　火花塞或点火变压器等部件异常也有可能导致爆震。

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

　　3、混合气浓度、温度、压力异常

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

　　混合气温度高一般可归结为进气温度高和中冷器温度高，也就是缸套水、中冷水入口温度高。

　　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.

　　混合气浓度过高，一般是空燃比调节系统设置不合理或出现故障，另外还有一种可能是燃气成分发生了变化。

　　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、气缸内有局部热点

　　4. There is a local hot spot inside the cylinder

　　活塞、缸套、气门均有可能出现局部热点，最常见的一种情况是积碳，最终会导致多点点火，也就是前面举例的那种情况。这种热点并不是太容易找出来，有时需要解体后仔细检查才能发现。

　　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、传感器或线路导致的假信号

　　5. False signals caused by sensors or circuits

　　有时会因为传感器和线路的原因出现假信号，这种情况不难排除。但需要注意的是，即使预判是假故障，在处理时也必须按照真爆燃的流程处理，否则一旦判断失误，后果可能很严重。

　　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、另外如果发动机设计不合理，也会导致爆震的趋势加大，但如果是成熟的机型，这些情况基本可以忽略。这几种情况有涡轮增压压力过高、压缩比过大、输出功率过大等。

　　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.

　　爆震的检测

　　Detection of detonation

　　爆震传感器通过检测气缸的压力和振动进行判断。检测到异常信号后，根据信号的强度，评估出爆震等级，然后给出相应的应对措施（自动调整、报警、停机）。

　　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).

　　早期的爆震检测系统不够完善，在发动机运行期间，如果真的用一个锤子去敲一下传感器附近，甚至机组本身运行产生的一些振动，都是有可能导致误报爆震停机的。由于在四个冲程中，爆震只会发生在点火冲程，现在的爆震检测一般都做了优化，只检测点火冲程那几十毫秒，大大减少了误报的可能性。

　　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.

　　有些机型每个缸配置一个爆震传感器，也有一些机型每相邻的两个缸共用一个传感器。由于点火顺序的存在，相邻的两个缸永远不会同时处在点火冲程，所以共用也不会有什么问题。

　　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、 推迟点火角

　　1. Delay ignition angle

　　推迟点火角可以在一定程度上降低爆震的烈度。出现爆震后，发动机的控制系统一般会自动推迟点火角，但调整到一定限度后，如果爆震依旧存在，就会给出报警。这时人工还可以再次尝试调整点火角，但一般都不会有多明显的效果了。

　　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

　　输出功率越高，气缸内压力越大，爆震程度也相对越高，因此降低功率也会减轻爆震的程度。对于一些质量不好的气，发电机组会有功率折损，锁住最大输出功率，其实就是因为爆震的关系。

　　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、 替换爆震传感器，如果爆震现象跟着传感器走，则有可能是假信号。检查/调整/替换传感器本体、接线、爆震控制模块等。

　　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、 如果爆震不跟着传感器走，则有可能是真爆震，检查/调整/替换火花塞、点火变压器、气门间隙等。

　　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，检查/调整/替换气门摇臂、挺杆等一系列和点火相关的部件。

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

　　6、 下杀手，检查/替换缸套、活塞、连杆等。

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

　　第7条并不完全是开玩笑，在处理内燃机故障的时候，爆燃相关的事情是最容易出现灵异事件的，所谓灵异，就是查了半天哪都没问题但就是有故障，或者好了也不知道为什么就好了。

　　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.

　　小编亲身经历过一次，新机，第一次开机就出现爆震，而且程度不轻，把能查的查了个遍，然后呼叫援军该拆的拆该换的换，一直解决不了。最后真的没辙了，扔下这台机器先做别的事。放了一周，再回来开机，无故障一次通过，直到负载测试，交付运行，都没再出现过爆震。那次的事情虽然算是解决了，但小编从此落下一个后遗症，一听到爆震俩字就头疼。

　　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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