Applied Research On Inhibitor Of Internal Combustion Engine Coolant

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.