The Advantages of Non-Thermal Plasma for Detonation Initiation Compared with Spark Plug

In this paper,the characteristics of detonation combustion ignited by AC-driven non-thermal plasma and spark plug in air/acetylene mixture have been compared in a doubletube experiment system.The two tubes had the same structure,and their closed ends were installed with a plasma generator and a spark plug,respectively.The propagation characteristics of the flame were measured by pressure sensors and ion probes.The experiment results show that,compared with a spark plug,the non-thermal plasma obviously broadened the range of equivalence ratio when the detonation wave could develop successfully,it also heightened the pressure value of detonation wave.Meanwhile,the detonation wave development time and the entire flame propagation time were reduced by half.All of these advantages benefited from the larger ignition volume when a non-thermal plasma was applied.

Low-Temperature Reforming Products Coupling Spark Plug on Gasoline Compression Ignition and Combustion Characteristics under Low-Load Condition

Gasoline compression combustion engine has the advantages of low emission and high efficiency,which is very promising for research,but it is difficult to apply under low-load conditions.Gasoline has the characteristics of low reactivity;in the case of low thermodynamic state in the cylinder,the fire delay period of the fuel is longer,and the combustion phase is relatively lagging,which will lead to the increase of combustion cycle fluctuations,and even difficult to ignite and other adverse combustion phenomena.In order to improve the combustion stability of Gasoline Compression Ignition(GCI)engine under low-load condition and expand the limit of low-load combustion boundary,gasoline was reformed without catalyst under the boundary condition of reforming temperature of 488 K and reforming equivalent ratio of 8,and the concentration of reformed product was measured by a gas detection device.Subsequently,the coupling of the reformed product and spark plug with GCI engine under low-load condition was investigated to analyze the effect on engine combustion and emission.The results showed that the initial combustion timing of the low-load GCI engine was late,but the addition of reformed products could advance the combustion phase,shorten the combustion duration,reduce single-cycle NOx emission,and improve the small-load operation characteristics of GCI engine.Coupled spark plug ignition on the basis of adding reformed products could further improve the problem of combustion stability under low-load GCI engine.And the optimization effect became more obvious as the ignition position of the spark plug moves down.However,spark plug ignition would cause local high temperature areas,resulting in an increase in NOx,emission.

Impact Resistance of Spark Plug’s Ceramic Insulator During Ultra-high-Pressure Combustion Under Deto-Knock Conditions

The ceramic insulators of spark plugs in gasoline engines are especially prone to damage when deto-knock occurs.To under-stand the damage process and mechanism,the present work investigated the impact resistance of ceramic insulators using detonation waves as impact sources.A test device that generates detonation waves was developed,representing a novel means of evaluating the knock resistance of ceramic insulators.Various impact types and detonation intensities were employed,and detonation initiation and propagation at peak pressures greater than 100 MPa were assessed using synchronous high-speed direct photography and pressure measurements.The test results demonstrate that ceramic insulators tend to break at the base of the breathing chamber when damaged by a single high peak pressure detonation wave impact.In contrast,multiple low pressure impacts eventually break the insulator into multiple fragments.The data also show that the positioning of a ground electrode upstream of the ceramic insulator greatly increases the resistance of the ceramic to the detonation impact.A two-dimensional computational fluid dynamics simulation coupled with a chemical kinetics analysis demonstrated that this improved resistance can be ascribed to a reduced peak pressure that appears after the detonation wave diffracts from the electrode prior to contacting the ceramic insulator.

A Sector Worth Noting——Spark Plug

The establishment of Nanjing Electroceramics Factory in 1953 marks the inauguration of spark plug production in China. China now has built an independent system of spark plug sector with 12 enterprises, a research institute (Nanjing Spark Plug Research Institute), a testing center in charge of products supervision (Center for