Effect of oxygen on performance and mass transport in a single-cell thermionic fuel element

The introduction of tracer amounts of oxygen into the interelectrode gap of a thermionic converter has been shown to improve converter performance. Excess oxygen, however, increases the loss rate of emitter material, reducing the converter performance and shortening its lifetime, owing to the increase in the effective emissivity of the electrodes, the change in the collector work function, and the deposition of emitter material oxides on spacers and insulators. In this paper, a model was developed which calculated the emitter material loss rate, composition of the emitter material deposits on the collector surface and investigated the effect of performance of a single-cell thermionic fuel element (TFE) in the presence of oxygen and cesium oxides in the interelectrode gap. The amount of oxygen and the cesium pressure in the interelectrode gap were varied parametrically and the TFE volt-ampere characteristics, and axial distributions of current density and emitter material loss rate along the TFE were calculated