Research On Antiknock Performance Of Unleaded Aviation Gasoline And Its Regulation

Aviation gasoline,known as aviation piston engine fuel,is one of the main fuels of general aviation nowadays.With the development of science and technology,in order to improve the combustion efficiency and reduce the consumption rate of fuel,the design-compression-ratio of aviation piston engine increases higher and higher.In order to avoid the detonation phenomenon,Aviation gasoline is also required with better anti-knock performance.By the more severe requirements of environmental protection,unleaded aviation gasoline has become an inevitable developed tendency.By the means of previous studies and relevant articles,this paper analyzed the reasons of detonation,and concluded the advanced spontaneous combustion of mixture gas is the fundamental cause of detonation combustion in aviation piston engine.Thus it speculated the following properties of antiknock agent should be contained.(1)Its thermodynamic properties were relatively stable.(2)It could effectively control or decompose the active peroxide produced by the oxidation of fuel before normal combustion.(3)It did not affect the other performances of gasoline,etc.At the same time,the requirements of avgas antiknock performance,the determination testing methods and common antiknock agents were investigated.The antiknock properties of avgas were usually determined by motor octane number(MON)and tested by ASTM-CFR single cylinder engine.Two common antiknock agents,metal ash and free organic ash,such as tetraethyl lead,methyl cyclopentadiene tricarbonyl manganese,aniline,tert-butyl acetate,methanol and methyl tert-butyl ether,were often blended to improve the antiknock properties.The high-octane number of alkylated gasoline(MON 93.1)was used as base oil,to optimize the high-octane number component and explosion-resistant agent.By blending high octane components and antiknock agents with alkylated gasoline,the anti-knock influences of aromatics,isomeric alkanes,metal ash and free organic ash antiknock agents were studied.The types and amounts of high-octane components and antiknock agents were optimized.Results showed that the recommended dosage of metal ash antiknock agent MMT was 200～300 ppm,and the octane number could improve by 4～5 units.For free organic ash antiknock agents,it is recommended to mix 4 vol%aniline and 10～15 vol%tert-butyl acetate,and the octane number could improve by 7～9 units.According to the regulation effect,combined with distillation range,vapor pressure and other performance requirements of aviation gasoline,two kinds of aviation gasoline were prepared by using metal ash antiknock agents and organic non-ash antiknock agents,and their physical and chemical properties and material compatibility were evaluated.Results show that the two kinds of optimizing the antiknock performance is acceptable.