Design, fabrication and high velocity oxy-fuel torch tests of a Cf-ZrB2- fiber nozzle to evaluate its potential in rocket motors

• A segmented nozzle composed of divergent and convergent graphite parts and of a ceramic throat was designed.
• The ceramic throat with composition 50 vol% Carbon fiber - 50 vol% ZrB2 was machined by EDM from a sintered pellet.
• The nozzle was tested in a high velocity oxy-fuel torch (HVOF) in conditions simulating typical exhaust engine flows.
• No appreciable erosion of the throat was observed after test at 2.5 Mach supersonic flow and 2730 K flame temperature.

The resistance to ablation of a ceramic nozzle made of a 50 vol% Carbon fiber-50 vol% ZrB2 composite was evaluated in a high velocity oxy-fuel torch (HVOF) in conditions simulating typical exhaust engine flows. The composite was prepared by hot pressing a mixture of ZrB2 powders and C chopped fibers and characterized in terms of microstructural features, strength and toughness. Then, the sintered pellet was machined by electro-discharge machining to obtain a ceramic throat. The throat was assembled to convergent and divergent graphite parts to compose a segmented nozzle and tested in HVOF torch under a heat flux of 2.5 MW/m2 and flame temperature of 2730 K. Fluid dynamic simulations enabled to rebuild the heat field temperatures of the jet flow and of the solid nozzle. The throat well survived 30 s undergoing little oxidation of the frontal zone without dimension or shape variation. No appreciable ablation of the throat was measured.

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