Real-Time Fuel to Air Mixing Ratio Measurement in Hypersonic Vehicles using Electrical Capacitance Volume Tomography

The proposed innovation is a two-phase volume fraction meter for monitoring the mixing ratio of air to jet fuel in a scramjet or ramjet using Electrical Capacitance Volume Tomography (ECVT). This innovation will leverage Tech4Imaging’s proprietary ECVT technology, an imaging modality originally developed for academic use, but later advanced by Tech4Imaging to operate in harsh environments and deliver real-time metrics such as volume fraction, velocity, and mass flow rate of multi-phase flows. Tech4Imaging has successfully applied ECVT to many industrial, commercial, space, and research applications including high temperature liquid-gas flows in geothermal fields, high pressure liquid-liquid and liquid-gas flows in oil and gas pipelines, and high temperature gas-solid flows in chemical reactors. ECVT is generally scalable to large and small applications. Previous applications included sizes ranging from 2.54 cm to 1 meter in diameter. Larger and smaller applications are possible. Sensors are made up of an array of capacitance electrodes surrounding the region of interest. These electrodes can be design in a variety of ways depending on the requirements for integration. Electrodes can be metallic plates embedded in refractory, polymer, or epoxy. They can be painted on, metallized, or thermal sprayed on to a surface. They can even be printed on 3D printers or flexible printed circuit boards. A variety of shapes can be designed as well such as flat, elbowed, and singled sided sensors depending on the required geometry from the application. Collection speed will be important for the hypersonic application. The current system runs on a 2MHz signal which is typically sampled over a number of capacitance plate pairs and averaged over time to improve the measurement. Recently, collection speed has been improved from hundreds of frames per second to speeds of up to 30,000 frames per second. Additional collection speed improvements will need to be made for this application, but past development shows these architecture changes are possible. Development has been performed by Tech4Imaging to create flight grade versions of the technology to survive harsh temperature swings and large shock and vibration events. The system has also been proven under a previous SBIR to be able to adequately distinguish between small differences in dielectric such as between gaseous and liquid nitrogen (dielectric constant of 1 and 1.7 respectively). This is important when working with air-jet fuel mixing or possibly liquid hydrogen mixing which has a dielectric constant of 1.28.