Shock tube
|
|
A shock tube is a device used primarily to study gas phase combustion reactions. A simple shock tube is just a metal tube in which a gas at low pressure and a gas at high pressure are separated using a diaphragm. This diaphragm suddenly bursts open under predetermined conditions to produce a shock wave. The low-pressure gas, referred to as the driven gas is subjected to the shock wave while the high pressure gas is known as the driver gas. The bursting of the diaphragm creates a compression wave in the driven gas, which then rapidly steepens to form a shock front, known as the incident shock wave. Simultaneously, a rarefaction wave, often referred to as a fan, travels back in to the driver gas. The experimental gas and the driver gas make contact at the contact surface, which moves rapidly along the tube behind the shock front.
Once the incident shock wave reaches the end of the shock tube, it is reflected back in to the already heated gas, resulting in a further rise in the temperature, pressure and density of the gas. This effectively creates a high temperature and high pressure reaction zone to which the driver gas is subjected. This reaction can be quenched by using a 'dump tank' which swallows the reflected shock wave. The gas samples are then collected from the tube and analysed.