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Experimental investigations have indicated that electrode vapor can have a significant negative effect in thermal interruption speed for the gas-blast circuit breakers. This electrode vapor contamination can be minimized by the use of asymmetric dual-flow nozzle configuration. A computer program was developed to design the nozzle and electrode geometries of the asymmetric dual-flow interrupter and to calculate both the subsonic and supersonic cold flow fields. The Variational Principle of the finite element method, together with a Newton-Raphson iterative scheme, was used to solve the continuity equation for compressible flow. The supersonic flow field in the conical nozzle was calculated by the one-dimensional flow relationship. Two asymmetric dual-flow nozzle models were constructed to investigate the effects of orifice opening and nozzle divergent angle. The cold flow experiments were conducted in the Rensselaer Polytechnic Institute (RPI) Transonic and Supersonic Wind Tunnel Laboratory. Various upstream-to-downstream nozzle pressure ratios were used to obtain the subsonic and supersonic experimental flow-field data. The experimental flow measurements were correlated with the calculated values to validate the computer program.
Date of Publication: Aug. 1986