The present work discusses an experimental investigation of the flow into a MEMS-based vaporizing liquid microthruster equipped with sensing capabilities and low-power on-channel secondary heaters. The sensing capabilities (Resistance Temperature Detectors and capacitive void fraction sensors) are used to investigate the flow instability and for performance control. The device has a sandwich structure, composed of a silicon substrate and a glass substrate: this last one allows optical access into the device. The main heating of the propellant is provided by means of a Platinum resistive heater placed on the bottom of the silicon layer. Three flow regimes have been detected and investigated: fully liquid flow, two-phase flow and fully vaporized flow. Their dynamics has been captured by means of high-speed micro-flow visualizations under rough vacuum conditions (about 29 kPa). Furthermore, the expansion of the exhaust vapor plume exiting from the micronozzle has been analysed vis Schlieren visualizations. Results highlighted the cyclic behaviour of the liquid-vapor flow into the inlet chamber and the micronozzle regions during the two-phase flow regime, while at the micronozzle the flow is still two-phase. Once the fully vaporized flow regime is established, the two-phase flow dynamics into the inlet chamber becomes more stable with complete filling and a more uniform distribution of the flow between microchannels. Schlieren imaging captured the increase of the exhaust plume spreading half-angle when moving from external ambient condition towards rough vacuum.
International Astronautical Federation (IAF)
1 Jan 2020
AC 2020 PROCEEDINGS