Studyon The Jet Flow Characteristics Of Gas And Liquid Under High Back Pressure

In recent years, the third generation Shell coal gasification and clean coal technology is widely applied, due to its advantages of stable performance, wide adaptability of coal.But the key quench process uses the output of the gasifier chilling syngas,the replacement of equipment and operation maintenance cost is extremely high. Based on Shell powder coal gasification water quenching,this paper studied the influence of the nozzle structure parameters,back pressure and the operation condition on the discharge coefficient,sprayangle, atomized particle size, atomization evenness and so onunder the condition of high back pressure,pure water and gas-liquid two-phase mixture,whichcan provide important theoretical and technical supportto industrial applications.Nozzle discharge coefficient is an important design parameter which determines nozzle performance.This paper selects 5 kinds of same conical inlet,different length to diameter ratio and exit diameter plain nozzle to carry out experiment,study the relationship between discharge coefficient and back pressure,the length to diameter ratio,and Re number under pure water,and the relationship between discharge coefficient and gas-liquid mass ratio,back pressure under gas-liquid two phase.The results show that the back pressure has an important influence on nozzle inner flow state. The greater the length to diameter ratio,the less prone cavitation occurs.For gas-liquid two phase nozzles,under the same back pressure,the discharge coefficient decreases rapidly with the increase of the gas liquid mass ratio first,then decreasing trend becomes slow until stable last;The discharge coefficient has the same change law under different back pressure,the back pressure has an great influence on the discharge coefficient,the higher the back pressure,the greater the discharge coefficient;the relationshipformula between discharge coefficient and the back pressure,gas liquid mass ratio is obtained by fitting.The spray cone is one of the importantparameter reflecting the jet atomization performanceintuitively.The Images of the sprayangle is obtained by flash photography method,then it is imported into AutoCAD to get the sprayangle value.The results show that the spray cone of pure water is in the range of 2-18°under the experiment condition.The nozzle length to diameter ratioaffects the spray cone significantly,the spray cone is notalwaysdecrease with the increase of length to diameter ratio.During the gas-liquid two phase,the spray cone is mutually influenced by the inside and outsidepressure differential and the back pressure.The Atomized particle sizeand dispersion is the most direct ebodiment of atomization performance. This paper selects4 different structure nozzles to carry out experiment to study the influence of structure parameters and gas-liquid mass ratio on atomization performance,using Winner318 laser particle size analyzer to measure. the following conclusion is concluded: when the back pressure is atmospheric pressure,working condition is pure water, sauter mean diameter linear decrease with the increase of injection pressure;the nozzle length to diameter ratio and outlet diameter affects the atomization,the greater the length to diameter ratio,the larger the atomized particle size,the less conducive to atomization; when it is gas-liquid twophase mixture,the addition of gas can not only greatly strengthen the atomization,but also increase the atomization evenness.