液击是指制冷剂因未能或未充分吸热蒸发，制冷剂液体或湿蒸汽被压缩机吸入到压缩机内的情况，叫液击。
Liquid blow means that the refrigerant liquid or wet steam is sucked into the compressor by the compressor due to failure or insufficient absorption of heat, which is called liquid blow.

一、引起的原因主要有：
First, the main reasons are as follows:
1、回液：即冷媒蒸发不完全、回液与膨胀阀选型和使用不当密切相关。膨胀阀选型过大、过热度设定太小、感温包安装方法不正确或绝热包扎破损、膨胀阀失灵都可能造成回液。
1, return liquid: that is, the refrigerant evaporation is incomplete, and the return liquid is closely related to the selection and improper use of expansion valve. Too large selection of expansion valve, too small setting of superheat, improper installation of temperature sensing package or failure of insulation and failure of expansion valve may result in liquid return.
2、带液启动时的泡沫过多：回气冷却型压缩机在启动时，曲轴箱内的润滑油剧烈起泡的现象叫带液启动。带液启动的根本原因是润滑油中溶解的以及沉在润滑油下面了大量的制冷剂，在压力突然降低时突然沸腾，并引起润滑油的起泡现象，带液启动引起的液击只发生在启动过程。
2. Excessive foam when the liquid is started. When the return air compressor is started, the phenomenon of oil bubbles in the crankcase is called liquid starting. The fundamental reason for the starting of the fluid is the dissolution of the lubricating oil and the large number of refrigerants sinking under the lubricating oil, which suddenly boil when the pressure is suddenly reduced, and cause the bubbling of the lubricating oil. The liquid strike caused by the starting of the liquid is only in the starting process.
3、压缩机内的润滑油太多：油位太高，高速旋转的曲轴和连杆大头就可能频繁撞击油面，引起润滑油大量飞溅。飞溅的润滑油一旦窜入进气道，带入气缸，就可能引起液击。
3. There are too many lubricants in the compressor: the oil level is too high, and the large crankshaft and connecting rod with high speed can hit the oil surface frequently, causing a lot of spatter of the lubricating oil. Once the splashing lubricant enters the intake port, it will lead to liquid blow.
4、制冷剂追加过多：制冷剂充注过多不仅会造成压缩机回气带液，还有可能会导致压缩机回气管冷媒流速过低，蒸发器内润滑油无法返回压缩机，造成压缩机缺油烧坏。
4, the refrigerant added too much: the refrigerant filling too much will not only cause the compressor back gas belt fluid, but also may lead to the compressor back gas flow velocity too low, the evaporator can not return to the compressor, causing the compressor to burn out.
5、蒸发器故障：在蒸发器内未经过蒸发就进入压缩机回气管，易造成压缩机液击。若有蒸发器故障导致盘管结霜严重，冷媒蒸发不完全也是引起压缩机回气带液的主要原因。
5, evaporator fault: in evaporator without evaporation into the compressor return pipe, easy to create a compressor liquid blow. If the evaporator failure causes the coil frosting is serious, the evaporation of refrigerant is not complete, which is also the main reason causing the compressor to return to the gas.
6、气液分离器容积设计选型不合理：系统增加气液分离器是防止压缩机缺油和液击的最有效的方法，气液分离器可将多余的冷媒可以暂时储存在气液分离器中，在热泵系统中，热气融霜制冷、制热切换工作时可以将冷凝器中积聚的制冷剂液体进行气液分离器，大大降低了液击的风险。
6. The design and selection of the volume design of the gas liquid separator is unreasonable: the air liquid separator is the most effective method to prevent the compressor from oil and liquid shock. The gas liquid separator can temporarily store the superfluous refrigerants in the gas liquid separator. In the heat pump system, the condensers can be deposited in the condensers when the heat gas thawing refrigeration and the heat transfer work are made. The refrigerant liquid which is gathered is used for gas-liquid separator, which greatly reduces the risk of liquid blow.
7、制冷剂迁移：制冷剂迁移是指压缩机停止运行时，蒸发器中的制冷剂以气体形式，通过回气管路进入压缩机并被润滑油吸收，或在压缩机内冷凝后与润滑油混合的过程或现象。
7, refrigerant migration: refrigerant migration refers to the process or phenomenon of the refrigerant in the evaporator in the form of gas in the form of gas in the form of gas in the evaporator to enter the compressor and be absorbed by the lubricating oil, or after condensing in the compressor, and mixing with the lubricating oil.
二、液击时改如何处置：
Two, how to deal with the change of liquid strike:
发生液击时，应马上关小压缩机的吸气截止阀，并关闭节流阀停止供液。如果吸气温度继续降低，要继续关小甚至关闭吸气阀。利用曲轴旋转时与轴瓦的摩擦热使曲轴箱内的制冷剂蒸发，直至曲轴箱内制冷剂完全蒸发。之后，稍微打开吸气截止阀，缓慢增载。发生液击时，应注意观察并调整油压，如没有油压或油压过低，应马上停机，将曲轴箱中的润滑油及制冷剂放出，重新加油再开机操作。
When the liquid blow occurs, turn off the suction stop valve of the compressor immediately, and close the throttle valve to stop the liquid supply. If the suction temperature continues to decrease, continue to turn off or even close the suction valve. When the crankshaft is rotated, the friction heat between the crankshaft and the bearing bush evaporates the refrigerant in the crankcase until the refrigerant evaporates completely in the crankcase. After that, turn on the suction valve slightly and increase the load slowly. When the liquid strike occurs, attention should be paid to the observation and adjustment of oil pressure. If no oil pressure or oil pressure is too low, the lubricating oil and refrigerant in the crankcase should be released, refuel and restart the machine.
三、如何防止压缩机液击：：
Three, how to prevent the liquid shock of the compressor::
1、减少制冷剂充注量：保护压缩机免受液态制冷剂引起的故障最好的方法是把制冷剂充注量限制在压缩机允许范围之内。若不可能做到这一点，则应在保证制冷效果的条件下，尽可能减少充注量，要对视液镜中因液体管径太细和压头太低产生的气泡引起警觉，合理充注制冷剂至关重要。
1, reduce the amount of refrigerant filling: the best way to protect the compressor from a liquid refrigerant is to limit the amount of refrigerant filling to the permissible range of the compressor. If it is not possible to do this, the amount of filling should be reduced as much as possible under the condition of ensuring the effect of refrigeration. It is very important to arouse the vigilance of the bubbles caused by too thin liquid pipe diameter and too low pressure head in the lens, and it is very important to fill the refrigerant reasonably.
2、曲轴箱加热器：曲轴箱加热器的功能是保持曲轴箱内冷冻油的温度高于系统中压缩机吸气入口的温度。曲轴箱加热器在使用中一般是连续加热的，曲轴箱加热器用于防止迁移是十分有效的，但是曲轴箱加热器不能够保护液体回流对压缩机造成的伤害，且加热器必须在压缩机开机前很长一段时间预热，对于实际应用可操作性不强。
2. Crankcase heater: the function of the crankcase heater is to keep the temperature of the refrigerating oil in the crankcase higher than the temperature at the inlet of the compressor in the system. Crankcase heaters are generally heated in use, and crankcase heaters are very effective in preventing migration, but the crankcase heater can not protect the liquid reflux from the compressor, and the heater must be preheated for a long time before the compressor is opened, and the operation is not strong for the practical application.
3、回气管过热加热器：在寒冷季节，压缩机运行时仍然有回气带液的可能，这样可以在压缩机回气管段增加电加热器或热气辅助提高压缩机回气过热度，这种方法简单有效，可增加过热检测装置使控制更加精确，从而保护压缩机，防止液击。
3, return air heater heater: in the cold season, the compressor is still able to return gas when running, which can increase the electric heater or heat to assist the compressor to increase the overheat of the compressor. This method is simple and effective. It can increase the overheat detection and install to make the control more accurate, thus protecting compression. Machine, prevent liquid strike.
4、吸气管气液分离器：在吸气管上安装气液分离器，用来临时存放系统中溢流的液态制冷剂，并且以压缩机能够承受的速率向压缩机返回液体制冷剂。由于不同制冷系统总体充注量要求不同，制冷剂控制方法各不相同，是否需要气液分离器以及需要多大尺寸的气液分离器在很大程度上取决于具体系统的要求。
4. Air and liquid separator of suction tube: a gas liquid separator is installed on the suction pipe to temporarily store the overflow liquid refrigerant in the system, and the liquid refrigerant is returned to the compressor at the rate that the compressor can bear. Due to the different requirements for the overall filling of different refrigeration systems, the refrigerant control methods are different. The need for gas and liquid separators and the large size of the gas and liquid separators depends on the requirements of the specific system to a large extent.
另外，在制冷系统设计阶段控制节流元件开度和增大蒸发器的换热面积，可以有效的提高回气过热度，减少在系统运行中压缩机液击现象发生。充注制冷剂时避免从低压侧液态充注，防止压缩机带液启动。
In addition, in the design stage of the refrigeration system, controlling the opening of the throttle element and increasing the heat transfer area of the evaporator can effectively improve the overheat of the gas, and reduce the phenomenon of the compressor liquid strike in the operation of the system. When filling refrigerant, avoid filling liquid at low pressure side and prevent compressor from starting with liquid.

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