Study On Cause And Mechanism Of Intial Velocity Deviation Of First Round

It is found on first round projectiles range deviation in some kinds of guns in our army. However the problem is not attached importance. Modern war requires artillery first round accurate and fire-for-effect. This paper is based on the problem about "coverage of first burst group" which is expected to reach for our artillery now. A series of experimental and theoretical studies focused on this problem have been presented. The main points of the paper are as follows:(1)According to the experimental data and parameter detection methods, mathematic expectation and variance are checked out on the range deviation of first round. Orientation about one gun in firing process is also detected. Using the detection results, we can draw the conclusion that system error is the main reason for the range deviation of the first round and subsequent round shooting test shows no orientation. Finally some suggestions are brought forward.The initial velocity deviation of first round in firing process is checked out. According to the detection results, it seems right that jump angle does not change between first round and others. We can get rid of possibility that the jump angle deviation factor will lead to first round deviation and confirm that the initial velocity deviation is the main reason for the range deviation of the first round.(2) Based on real initial velocity concept, the relationship of several velocities is given. A theory brought forward about method of initial velocity error modifying coefficients. Based on the Lagrange interior ballistics and the initial velocity parse result, each parameter coefficient expression and initial velocity error expression are suggested through theory deduction. According to the expression, several modifying coefficients are calculated. The solve results approximately accord with experimental results. The modifying method of initial velocity error including model, sensitive parameters and inferential formulas, will change the presently situation that initial velocity modifying coefficient simply depends on the experiments on shooting range. (3) For the sake of clarifying the influence of oil on interface to projectile velocity, this paper discusses the type of band entrance lubrication with oil on forcing cone, establishes the mathematical model of bands entrance and friction and estimates the thickness of oil film on the interface. According to the model and some main parameters of 130mm gun, the factors affecting the friction coefficient are analysed and a calculating formula is concluded through simulating this mathematical model. This paper discusses and establishes the mathematical model of melt-lubrication between band and gun tube with oil on the bore interface. The characteristics of band melt-liquid are simulated and influences of friction coefficient are calculated. The solve results approximately accord with experimental results. The solve results show that friction coefficient of first round projectile is the same as the latter rounds after a few distance, but the first one will be larger than the latter one when the projectile starts moving. It is an important factor that makes first round velocity higher and range further. The model contacts with interior ballistic model and gives stimulation result, which will provide theory references.(4) Bore temperature plays an important role in different firing conditions between first round projectile and later rounds. This paper gives quantitative analysis about the influence of bore heat loss and expanse to projectile muzzle velocity, establishes the mathematical model about bore heat loss and calculates the model. The deviations of initial velocity are forecast.(5) Mechanism of jump angle is analyzed and the model is established. The calculate result shows that the first round jump angle is the same as the later rounds.