Gas velocity and temperature were measured probing the discharge holes of a gas generator with high temporal resolution (sub-ms). The pressure history was additionally recorded at a further discharge hole, in order to derive mass and energy efflux needed for the numerical simulation of airbag-inflation behaviour. Also the discharge of the gases was visualized using a high-speed camera to provide view on its temporal evolution. Time resolved temperature measurements were carried out by means of the well known method of emission-absorption spectroscopic method. Gas temperature could only be measured spectroscopically 5 ms after ignition for values above 550 K, due to the low emission intensity and low absorptance of the gases, especially at the selected observation wavelength (2.7 um). The temperature rises to a maximum after about 30 ms attaining values above 800 K and then decays. For times t > 50 ms it cannot be measured any more, because the temperature drops down below the measurement limit of 650 K. The velocity of flow-borne particles were obtained by means of a laser-Doppler velocimeter invented by SMEETS. The observed steep fall and rise of the gas velocity (maximum 1000 m/s) was explained by the motion of an inner shock font - the so called Mach-disc - when it passes the point of measurement. Further research plans to extend the spectral range of the emission-absorption method to the far IR at observation wavelengths of 8 - 14 um. Then temperature measurements down to 200 K (room temperature or even below) with high temporal resolution (> 1 us) becomes feasible. For the covering abstract see ITRD E126782.
Abstract