内燃机冷却液缓蚀剂

内燃机冷却液一般由缓蚀剂、水和冰点抑制剂组成,用作内燃机冷却系统的携热载体。随着内燃机强载度的提高,内燃机冷却系统的管路、水泵、特别是湿式气缸套,常常存在穴蚀(又称空泡腐蚀和气蚀)现象。理论计算表明,穴蚀过程中气泡破裂产生的微射流能产生数百个大气压的压力和上千度的高温,机件受到机械和电化学腐蚀作用,二者协同作用时,对于铸铁机件所受到的破坏比单一作用时大得多,所以缓蚀剂不仅应有减缓机件腐蚀的性能,而且应有良好的减缓机件穴蚀的作用。 经研究世界主要国家关于内燃机冷却液的规范,本文提出的内燃机冷却液规范除了国内已经有的SH 0521-1999及JT 225-1996所列性能指标以外,针对冷却液使用中可能存在的隐患,提出还应该包含:冷却液的粘度要求;与橡胶制件的相容性;抑制穴蚀性能;贮存稳定性等。 以铸铁试件为研究对象,借助于磁致伸缩模拟试验装置,研究了冷却液的性能参数对穴蚀的影响,包括温度、pH值、腐蚀性离子的浓度以及不同化学试剂等影响因素,深入研究了典型化学试剂抑制穴蚀性能的效果。研究结果表明:在腐蚀水中的最大失重温度是60℃,在蒸馏水中的最大失重温度是70℃;随着腐蚀水浓度的提高,穴蚀失重也逐渐提高;随着pH值由小到大,即水溶液由酸性到碱性,穴蚀失重逐渐减少,当pH值为13时,穴蚀的失重很少;冷却液中随着乙二醇或丙二醇浓度的增加,穴蚀失重逐渐减少;化学试剂对于铸铁的穴蚀有重要的影响,传统的无机盐如亚硝酸钠、钼酸钠减缓铸铁穴蚀的能力不如有机羧酸盐如葵二酸钠和庚酸钠等有效。 本研究采用复配一元和二元羧酸技术所研制的冷却液缓蚀剂具有较好的性能,有效抑制了冷却液系统的腐蚀和穴蚀,其机理在电化学方面是抑制金属的阴极和阳极反应,在抑制机械破坏方面一方面是加入有机羧酸后,穴蚀产生的气泡溃灭强度下降,另外一方面是铸铁机件表面与有机羧酸形成了有机膜,该有机膜可有效抑制微射流的破坏。 所研制的冷却液防蚀剂在通过实验室试验的基础上,在实际的铝制机体
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The coolant of internal combustion engine (ICE), as a fluid that draws off heat by circulating through an engine, generally consists of inhibitors, water and antifreeze. With the increase of ICE output power, cavitation usually occurs in the pipe, water pump, and wet cylinder liner. Theoretic calculation has indicated that the micro-jet effect caused by air bubble cracking in the cavitation process results in the high pressure up to hundreds of standard atmospheric pressure and the high temperature up to thousand-Celsius degree. Accordingly, the work piece is destroyed by mechanical and electrochemical effect. For the cast-iron work piece, the synergistic effect of cavitation and corrosion causes much severer degradation of the work piece than the either independent effect. Therefore, the inhibitors in coolant can prevent not only corrosion but also cavitation.Through the study of specifications about internal combustion engine coolant overseas, combined with the national specifications of internal combustion engine coolant such as SH 0521—1999 and JT 225—1996, besides the general indexes listed in the international and national specifications, some extra indexes need to be included to develop the inhibitors in coloant in order to get ride of the potential hidden troubles during the use of the coolant. The extra indexes of the coolant inhibitor mainly include the viscosity, the compatibility to rubber, the capability of anti-cavitation and the store stability.In this paper, magnetostriction vibratory equipment was used to simulate the cavitation occurred in the internal combustion engine in wihch the cylinder liner was made of cast iron. The influence of the main coolant performance parameter, that is, temperature, pH, the concentration of corrosive ion and different chemical agents, were studied. The results showed that the temperature of the coolant had a great impact on the cavitation. The maximum loss of test piece occured at 60℃ in corrosive water, and at 70℃ in distilled water. With the increase of the concentration of the corrosive ion, the weight loss of the test piece increased. With the increase of the pH value of water solution, the weight loss of the test piecedecreased. The weight loss of test piece caused by cavitation was very slight when pH was up to 13. When the concentration of ethylene glycol or propylene glycol increased, there was a declining trend on the degree of the occurance of cavitation. Chemical agents in coolant had a very important impact on the iron cavitation. The anti-cavitation ability of traditional chemical agents such as sodium nitrite and sodium molybdenum was less than that of carboxylic salts such as sodium sebacic and enanthic.The coolant inhibitor developed in this study based on mono/di carboxylic acid had excellent performance to restrain the occurance of corrosion and cavitation in cooling system. In point of electrochemistry, the mechanism was that the catholic and anodic reaction was inhibited. From the point view of mechanical mechanism, the air bubble cracking intensity by cavitation decreased at the same vibrating amplitude. Moreover, the organic film formed on iron surface weakened effectively the action of the micro-jet stream.The experiments in laboratory were employed to evlaute the coolant inhibitor developed in this study. The coolant inhibitor was tested in the 12V150 diesel engine whose engine block was made of cast aluminum, MWM TBD 234 diesel engine with high thermal load and the diesel engine whose water jacket was made of cast aluminum respectively. The test results showed that the coolant inhibitor met the requirements and had a good performance in preventing corrosion and cavitation.Through a completed analysis of the coolant, the monitoring program and content of the coolant were presented in the paper. In the program, firstly, the spectrography and ferrography were used to gain the information on corrosion and cavitation in coolant. Subsequently, the analysis of concentration, pH, reserve alkalinity and components of ash in the coolant revealed the attenuation of coolant inhibitors. These methods provided the scientific measurement approaches for monitoring cooling system, refilling inhibitors and replacing the coolant.