Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods were investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which works by increasing the turbulent flow of the deflagration wave, thus increasing its speed and pressure. This approach increased the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increased the peak pressure from 1.17 MPa to 2.25 MPa. Using a 103 mm driving section increased peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, resulted in a peak pressure increase to 1.70 MPa.

No abstract

A potato cannon was designed to accommodate several different experimental propellants and have a transparent barrel so the movement of the projectile could be recorded on high-speed video (at 2000 frames per second). Both combustion chamber and barrel were made of polyvinyl chloride (PVC). Five experimental propellants were tested: propane (C 3 H 8 ), acetylene (C 2 H 2 ), ethanol (C 2 H 6 O), methanol (CH 4 O), and butane (C 4 H 10 ). The amount of each experimental propellant was calculated to approximate a stoichometric mixture and considering the Upper Flammability Limit (UFL) and the Lower Flammability Limit (LFL), which in turn were affected by the volume of the combustion chamber. Cylindrical projectiles were cut from raw potatoes so that there was an airtight fit, and each weighed 50 (± 0.5) grams. For each trial, position as a function of time was determined via frame by frame analysis. Five trials were taken for each experimental propellant and the results analyzed to compute velocity and acceleration as functions of time. Additional quantities including force on the potato and the pressure applied to the potato were also computed. For each experimental propellant, average velocity vs. barrel position curves were plotted. The most effective experimental propellant was defined as the one which accelerated the potato to the highest muzzle velocity. The experimental propellant acetylene performed the best on average (138.1 m/s), followed by methanol (48.2 m/s), butane (34.6 m/s), ethanol (33.3 m/s), and propane (27.9 m/s), respectively.Propellant Acetylene 10894 513 4.71 Propane 9302 21 0.23 Ethanol 9078 29 0.32 Methanol 10140 66 0.65 Butane 9273 33 0.35 Combustion Energy (J) Projectile Muzzle Energy (J) Efficiency (%)

No abstract

No abstract