Study Of Drag Reduction Characteristics For The Base Bleed Projectile

Based on the engineering background of base bleed extend range technology,in order to obtain the maximum extend range rate and the minimum range dispersion for the research object of the domestic 155 mm base bleed projectile,the interior ballistic model,drag reduction equation and exterior ballistic model for the base bleed projectile are established respectively.The influences of the burning rate regularity of base bleed propellant and the inconsistent working characteristics of base bleed unit on drag reduction characteristics are analyzed.In addition,the empirical and semi-empirical formulas are established through domestic and abroad flight and wind tunnel test data,the prediction and simulation of base drag coefficient,base pressure ratio and drag reduction rate are achieved quickly to provide reliable reference for the ballistic calculation and the overall design of new-type base bleed projectile.The main research contents and results are as follows:(1)Based on the ballistic calculation model of base bleed projectile,three burning models are established by introducing the burning rate change coefficient and dividing into two layer of base bleed propellant to research the influence of drag reduction characteristics with base bleed propellant with different burning rate,cladding propellant with variable burning rate and different cladding layer position of propellant.The new method is put forward which improves the drag reduction and extend range characteristics,and the method has universal applicability.(2)Based on the ballistic calculation model of base bleed projectile,the control variable method is adopted to study the influence of the ignition delay time,propellant mass deviation,base bleed working environment and initial propellant temperature on the drag reduction characteristics.The range dispersion is obtained in result of the four factors of average unit ignition delay time,propellant initial mass deviation,launch altitude location and initial propellant temperature to provide the theoretical basis for reducing range dispersion of base bleed projectile.(3)By sorting and analyzing the flight test and wind tunnel test results,the empirical or semi-empirical equations are summarized and the base drag coefficient,base pressure ratio and drag reduction rate are simulated.The engineering calculation results of base drag coefficient and the influence of attack angle are obtained.In order to reduce the range dispersion,various kinds of base drag coefficient calculation methods are analyzed.It is proved that the base pressure ratio calculation model has a definite accuracy and applicability after comparing the calculation result of base pressure ratio with the wind tunnel test data in the papers.According to the drag reduction rate calculation results,the applicable range,main consideration factor,and the adopted methods of the actual ballistic calculation and firing table are analyzed,which makes it convenient for the quick prediction and simulation computation in engineering.