High power microwave system for fluid injection applications

Summary form only given. Resin injection is an essential step in fabrication of carbon fibre reinforced plastic (CFRP) parts for infusion technologies. To increase the flow rate of a resin and to speed up the infiltration, the viscosity of a resin is decreased by heating. Microwaves (MW) offer a volumetric, selective and very fast heating, which leads to a homogeneous resin infiltration and to a shorter injection cycle. Using these advantages of MW heating, the developed MW injector provides also an efficient and safe energy transfer from the MW source to the resin. The new MW injector is a compact, low-cost and automated system that consists of a waveguide section, a cylindrical holder of a teflon hose for resin injection, a 2.45 GHz industrial magnetron source with adjustable power level up to 2 kW and a control unit. The magnetron is directly coupled to a launching waveguide, without any circulator or tuner. The developed system provides a temperature monitoring and a completely automatized MW power adjustment, by controlling the temperature of the flowing resin at the outlet of the MW device. The control is a crucial issue in the development of the system that ensures an immediate answer of the MW generator to rapid changes in the temperature for high flow rates of the resin. Our design approach is based on experimental optimizations, leading to a reliable industrial device. In low power measurements with a vector network analyzer, the length of the waveguide cavity has been adjusted to provide the lowest reflections and a good efficiency of the system. In high power experiments, the MW injector has been tested and optimized for specific resin infiltration under both, laboratory and industrial conditions. The results have shown that the novel MW injector can be reliably used for the defined high ranges of working temperatures and flowing rates, providing high system dynamics that is required for industrial applications. The MW injector will be fully integrated t- - o the HEPHAISTOS systems for the advanced processing of CFRP large parts.