Performance analysis and enhancement of the ballistic range
01 May 2007-Vol. 221, Iss: 5, pp 649-659
TL;DR: In this paper, a theoretical analysis has been carried out to investigate various unsteady processes involved in the operation of the ballistic range and to assess the performance of the two-stage light-gas gun.
Abstract: The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, and aeroballistics, since it can create an extremely high-pressure state in a very short time. Of many different types of ballistic ranges developed to date, a two-stage light-gas gun is being employed most extensively. Since the operation of the ballistic range involves many complicated gas dynamic processes, optimization of various design parameters of the ballistic range is important for the durability of its components. In the present study, a theoretical analysis has been carried out to investigate various unsteady processes involved in the operation of the ballistic range and to assess the performance of the ballistic range. The results obtained are validated with the available experimental data. A shock tube is added in between the pump tube and launch tube and its effect on the performance of the ballistic range is quantified using the present the...
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TL;DR: In this article, a computational study using a moving grid method is performed to analyze various fluid dynamic phenomena in the near field of a gun, such as the projectile-shock wave interactions and interactions between the flow structures and the aerodynamic characteristics of the projectile when it passes through various flow interfaces.
Abstract: The aerodynamics of projectiles launched from barrels of various devices is quite complicated due to their interactions with the unsteady flowfield around them. A computational study using a moving grid method is performed here to analyze various fluid dynamic phenomena in the near field of a gun, such as the projectile–shock wave interactions and interactions between the flow structures and the aerodynamic characteristics of the projectile when it passes through various flow interfaces. Cylindrical and conical projectiles have been employed to study such interactions and the fluid dynamics of the flowfields. The aerodynamic characteristics of the projectile are hardly affected by the projectile configuration during the process of the projectile overtaking the primary blast wave for small Mach numbers. However, it is noticed that the projectile configurations do affect the unsteady flow structures before overtaking and hence, the unsteady drag coefficient for the conical projectile shows considerable vari...
12 citations
01 Oct 2013
TL;DR: In this article, experimental studies were carried out to a closed end (downstream) micro shock tube with two different diameters were investigated to understand the flow characteristics and the results obtained show that with the increase in diameter the shock propagation velocity increases as well as the effect of reflected shock wave will be more significant under the same diaphragm rupture pressure.
Abstract: Micro shock tubes are now-a-days used for a variety engineering applications such as in the field of aerospace, combustion technology and drug delivery systems. But the flow characteristics of micro shock tube will be different from that of well established conventional macro shock tube under the influence of very low Reynolds number and high Knudsen number formed due to smaller diameter. In present study, experimental studies were carried out to a closed end (downstream) Micro Shock Tube with two different diameters were investigated to understand the flow characteristics. Pressure values were measured at different locations inside the driver and driven section. The results obtained show that with the increase in diameter the shock propagation velocity increases as well as the effect of reflected shock wave will be more significant under the same diaphragm rupture pressure.
11 citations
Additional excerpts
...Micro Shock Tube는 초기압력비나 파막과정 등이 충격파관 내부에서 발생하는 비정상 유동 장(충격파나 접촉면 전파 특성 등)에 큰 영향을 미치게 되며, 매우 작은 직경으로 인해 높은 Knudsen Number 및 낮은 Reynolds Number가 형성되며 부피에 비해 표면적의 비율이 높은 특 성을 가져 기존의 Macro Shock Tube 내부유동 과는 상이하게 나타난다[2-4]....
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TL;DR: In this article, the effects of the projectile overtaking amoving shock wave on the projectile aerodynamic characteristics were analyzed using a moving-grid method to analyze the effect of the collision on the aerodynamic properties.
Abstract: A projectile that passes through a moving shock wave experiences drastic changes in the aerodynamic forces as it moves from a high-pressure region to a low-pressure region. These sudden changes in the forces are attributed to the wave structures produced by the projectile–shock-wave interaction and are responsible for destabilizing the trajectory of the projectile, consequently leading to a loss of projectile stability and control efficiency. A computational study was performed here using a moving-grid method to analyze the effects of the projectile overtaking amoving shock wave on the projectile aerodynamic characteristics. A one-dimensional analysis was also carried out to identify the projectile overtaking criteria. The analytical results show that the projectile overtaking flowfields canbe in a subsonic or supersonicflowregime, based on the relative projectileMachnumber.However, it is found that the actual flowfields in the present computations cannot be distinguishedwith the relative projectileMach number only, because theblast-wave strength is diminishingwith time and space. The aerodynamic characteristics of the projectile are hardly affected by the overtaking process for smaller blast-waveMach numbers, as the blast wave will become weak by the time it is overtaken by the projectile. The projectile drag coefficient is more greatly affected by the unsteady flow structures through which the projectile travels in the near field than by the overtaking process.
10 citations
Cites background from "Performance analysis and enhancemen..."
...This is a quite reasonable assumption, as it refers to a condition of the compression explosion in a ballistic range facility [6]....
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...Meanwhile, the high-pressure gas that, in general, is obtained by the combustion explosion in the ballistic range [6] and used to drive the projectile initially is discharged immediately after the projectile is ejected from the launch tube....
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Posted Content•
TL;DR: In this article, a computational study using moving grid method is performed to analyze the effect of the projectile-shock wave interaction, where both cylindrical and conical projectiles have been employed to study such interactions and the fluid dynamics of such flow fields.
Abstract: The aerodynamics of a projectile launched from barrels of various devices is quite complicated due to its interactions with the unsteady flow field around it. A computational study using moving grid method is performed here to analyze the effect of the projectile-shock wave interaction. Cylindrical and conical projectiles have been employed to study such interactions and the fluid dynamics of such flow fields. It is found that the overall effect of projectile overtaking a blast wave on the unsteady aerodynamic characteristics of the projectile is hardly affected by the projectile configurations. However, it is noticed that the projectile configurations do affect the unsteady flow structures and hence the drag coefficient for the conical projectile shows considerable variation from that of the cylindrical projectile. The projectile aerodynamic characteristics, when it interacts with the secondary shock wave, are analyzed in detail. It is also observed that the change in the characteristics of the secondary shock wave during the interaction is different for different projectile configurations. Both inviscid and viscous simulations were done to study the projectile aerodynamics. It is found that the effect of the viscosity on the projectile aerodynamics is negligible but the viscosity does affect the unsteady flow structures around the projectile.
8 citations
01 Oct 2012
TL;DR: In this paper, experimental studies were carried out on micro shock tubes of two diameters to investigate flow characteristics and shock propagation, and the experimental values other parameters like shock veloci ty, shock strength were found and shock wave diagram was constructed.
Abstract: Past few years have seen the growing importance of micro shoc k tubes in various engineering applications like micro combution, micro propulsion, particle d elivery systems. But in order to efficiently apply Micro Shock Tube to such areas require the de tailed knowledge of shock characteristics and flow field inside a micro shock tube. Due t o many factors such as boundary layer, low Reynolds number and high Knudsen number shock propagation i nside micro shock tubes will be quite different from that of the well established macro shock t ubes. In the present study, experimental studies were carried out on micro shock tubes of two diameters to investigate flow characteristics and shock propagation. Pressure values were measured at different l ocations inside the driven section. From the experimental values other parameters like shock veloci ty, shock strength were found and shock wave diagram was constructed. 초 록 최근 Micro Combution, Micro Propulsion, Particle Delivery Systems 등 다양한 공학 응용 분야에서 Micro Shock Tube의 중요성이 커지고 있다. 그러나 여러 분야에 Micro Shock Tube를 효율적으로 적용하기 위해서는 관내유동과 충격특성에 대한 상세한 지식을 필요로 한다. 경계층과 같은 많은 요소들 때문에 Micro Shock Tube 내부의 낮은 Reynolds Number와 높은 Knudsen Number가 형성되며, 이 때의 충격파 전파는 기존의 Macro Shock Tube와 상이하게 나타난다. 본 연구에서는 Micro Shock Tube에서의 충격파 전파와 유동특성을 조사하기 위해 직경 3 mm와 6 mm의 두 가지 Micro Shock Tube를 이용하여 실험을 수행하였으며, 압력은 고압관의 파막압력과 저압관의 세 지점에서 측정되었다. 충격파 속도와 같은 다른 변수들의 실험값으로부터 충격파 강도를 찾고 충격파 선도를 나타내었다.Key Words: Shock Wave(충격파), Micro Shock Tube(미소충격파관), Diaphragm(격막), Shock Wave Propagation(충격파 전파), Rupture Pressure(파막압력)
5 citations
References
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TL;DR: The Ram Accelerator as discussed by the authors is based on gas-dynamic principles similar to those of an air-breathing ramjet but operates in a different manner, where the center body of a ramjet travels through a tube filled with a premixed gaseous fuel and oxidizer mixture, and the tube becomes the outer cowling of the ramjet.
Abstract: A new method for accelerating projectiles from velocities of ~0.7 km/s up to -12 km/s using chemical energy is presented in this paper. The concept, called the "ram accelerator," is based on gasdynamic principles similar to those of an airbreathing ramjet but operates in a different manner. The projectile, which resembles the center body of a ramjet, travels through a tube filled with a premixed gaseous fuel and oxidizer mixture. The tube becomes the outer cowling of the ramjet, and the energy release process travels with the projectile. By tailoring the propellant mixture along the tube, a nearly constant acceleration can be achieved. In principle, the ram accelerator can be scaled for projectile masses ranging from grams to hundreds of kilograms and is capable of ballistic efficiencies as high as 30%. A straightforwar d, quasisteady, one-dimensional approach is used to model the acceleration process. The experimental facility developed to investigate the concept is described, and the results of recent experiments are presented. The velocity range of 690-1500 m/s has been explored in a 4.88-m long, 38-mm bore accelerator tube. Using methane, oxygen, and various diluents, accelerations of up to 16,000 g have been achieved with 75 gm projectiles and gas fill pressures of 20 atm. Proof of concept has been demonstrated, and agreement between theory and experiment has been found to be very good.
334 citations
202 citations
Book•
01 Jan 1994
TL;DR: In this paper, a simple spherical and cylindrical shock-tube analogues and flow simulation are presented, along with real-gas effects on shock tube flows and their applications.
Abstract: 1. Introduction 2. Shock waves on earth and in space 3. Transition fronts 4. One-dimensional flows in a simple shock tube 5. Shock tubes with area change 6. Boundary-layer effects 7. Two-dimensional studies of oblique shock-wave reflection and diffraction 8. Spherical and cylindrical shock-tube analogues and flow simulation 10. Dusty-gas shock tube 11. Real-gas effects on shock-tube flows 12. Implosion waves and applications 13. Shock-tube construction and instrumentation 14. Closing comments Index
94 citations
TL;DR: In this article, the Sandia hypervelocity launcher achieved velocities up to 15.8 km/s by using a graded-density assembly to impact a stationary flier-plate.
Abstract: A systematic study is described which has led to the successful launch of thin flier plates to velocities of 16 km/s. The energy required to launch a flier plate to 16 km/s is approximately 10 to 15 times the energy required to melt and vaporize the plate. The energy must, therefore, be deposited in a well-controlled manner to prevent melt or vaporization. This is achieved by using a graded-density assembly to impact a stationary flier-plate. Upon impact, time-dependent, structured, high pressure pulses are generated and used to propel the plates to hypervelocities without melt or fracture. In previous studies, a graded-density impact of 7.3 km/s was used to launch a 0.5 mm thick plate to a velocity of over 12 km/s. If impact techniques alone were to be used to achieve flier-plate velocities approaching 16 km/s, this would require that the graded-density impact occur at - 10 km/s. In this paper, we describe a new technique that has been implemented to enhance the performance of the Sandia hypervelocity launcher. This technique of creating an impact-generated acceleration reservoir, has allowed the launch of 0.5 mm to 1.0 mm thick plates to record velocities up to 15.8 km/s. In these experiments, both titanium (Ti-6A1-4V) and aluminum (6061-T6) alloy were used for the flier-plate material. These are the highest metallic projectile plate velocities ever achieved for masses in the range of 0.1 g to 1 g.
77 citations
TL;DR: The results show that a two-stage free-piston driver is capable of driving hypervelocity expansion tubes and therefore new facilities of increased size but reduced cost are now possible.
Abstract: The overall cost of free-piston driven facilities can be substantially reduced if the contraction between the compression and shock tubes is replaced with a constant area section. However, with such an implementation, a new driver concept is required in order to achieve a realistic facility length. This paper describes a new free-piston driver type for expansion tubes which satisfies the above criteria. The technique is known as the two-stage free-piston driver where the driver gas is compressed in two distinct stages with a unique compound piston design. A new facility has been constructed (X-2) which is described in some detail. A quasi-one-dimensional numerical model of the compression process is also developed which agrees well with driver tube experimental results. This new driver is coupled to an expansion tube arrangement where super-orbital test flows are generated. The results show that a two-stage free-piston driver is capable of driving hypervelocity expansion tubes and therefore new facilities of increased size but reduced cost are now possible.
33 citations