Advanced Materials Development for Thrust Vector Control and Testing in an Abrasive Jet Wash Facility

Kurzfassung

For the development of advanced materials and structures with improved abrasion resistance a better understanding of the complex multiphase flow / structure interaction is necessary. Fibre reinforced ceramic matrix composites (CMC) combine the general properties of ceramic materials (abrasion and high temperature resistance as well as high temperature strength and hardness) with favourable properties of fibre reinforced composites (high damage tolerance in case of overloading). Due to their extreme thermal shock resistance and stability under high temperature load beyond 2000 °C they are ideal candidates for hot gas applications in rocket motor propulsion for aerospace. Liquid silicon infiltration (LSI) developed by DLR provides ideal requirements in order to manufacture cost-effective CMC components based on C/C-SiC, which are not feasible by other CMC manufacturing techniques (e.g. CVI) owing to complex component geometry, especially wall thickness. In order to be able to test erosion and high temperature stability of materials and components with respect to combustor and nozzle relevant conditions, a test facility was developed and erected at DLR M11 test complex: Abrasive Hot Gas Facility (HotGaF). This facility is able to produce particle and droplet laden hot gas flows with temperatures and area specific impulse densities of the condensed phase, similar to distinct smaller solid rocket motors. The hot abrasive jet wash is produced by the combustion of Al particle containing solid fuel tubes with a preheated and oxygen enriched air flow in a primary and a subsequent secondary combustion chamber. The production of the oxygen enriched hot vitiated air flow is conducted by making use of hydrogen/oxygen burners. Due to the design of this facility similar to a connected pipe ramjet combustor test facility, the time period, in which the abrasive jet wash attacks the samples, can be varied by the quick shut-down of the “air” heater at pre-selected times and the opening of a bypass valve. Thus “load” pulses of pre-selected time can be generated for the determination of abrasion histories. Here a solid fuel composition of HTPB/IPDI with 40 wt.-% Al particles was used. No chlorine containing additives were used in these test runs, because the primary goal of the conducted investigations was to show the direct influence of the condensed phase (Al2O3, Al, etc.) in a jet wash on the abrasion of the ceramic jet vane samples based on C/C-SiC. In order to measure pressure and temperature at various positions in the C/C-SiC nozzle, which is a prerequisite for the time-resolved erosion history of jet-vane samples, nine pressure and temperature ports were implemented. A 6 degree-of-freedom (6 DOF) thrust balance can be connected to the test facility for the determination of the changes of the forces and moments acting on the test specimen. Figure 1 shows as example two images from a typical test run at the abrasive hot gas facility. A C/C-SiC test specimen is positioned in the expansion part of the C/C-SiC nozzle. Tests under these conditions shall give information of contour erosion, which is relevant for material development of jet vanes. The left image shows the glowing of the upstream part of the sample and the nozzle wall during the test run. The right image presents a view into the nozzle after the test run, which shows the erosion of the test specimen. The proposed publication will give both a detailed overview of the material and component development based on C/C-SiC and an overview of HotGaF as well as its capabilities for testing of materials and components. In addition, some typical results of tested C/C-SiC materials (inlay in secondary combustor, nozzle as well as jet-vane samples) are presented.