Influence Of Space Barrier On Electrical Performance Of Thermionic Energy Converter

Thermionic energy converter(TEC)is a static thermal-to-electricity conversion technology with broad application potential for advantages of compact structure,no moving parts and high power density.The low efficiency of practical TEC is a major obstacle toward widely application.Adjusting and controlling the space barrier is one of the key approaches to improve the TEC performance.However,traditional theoretical models couldn't be used for optimized design of the device because they ignored effects of the current from collector.Considering factors such as space barrier and the current from collector,more consummated theoretical calculation models of electrical performance were established based on traditional theoretical models.Furthermore,the electrical performance analysis and optimization design of the device were carried out using the matrix calculation function of the MATLAB software.The main research contents were as follows:(1)For the vacuum TEC,the current density correction coefficient ?i and the space voltage drop correction coefficient ?v were further introduced in Langmuir's model to evaluate the effect of the current from collector on electrical performance.And the influence of electrode temperature,work function and electrode spacing on the vacuum TEC energy conversion performance analysis was carried out.It showed that the electrode spacing of the vacuum TEC should be 1?10 ?m.Under the condition of fixed emitter's work function and temperature,the best design values of collector's work function and temperature were given based on the principle of maximizing power density.(2)For the cesium vapor TEC operating in Knudsen mode,the calculations of the current from collector and internal energy of electrons were further introduced in traditional Kuznetsov's model.The influence of electrode temperature and work function on the cesium vapor TEC electrical performance analysis was carried out.It showed that the best design values of collector's work function and temperature were given based on the principle of maximizing power density under the condition of fixed emitter's work function and temperature.(3)For the cesium vapor TEC operating in ignited mode,based on the empirical formula of plasma arc drop proposed by Kitrilakis,a theoretical calculation model of electrical performance analysis based on multiple parameters optimization design(including electrode temperature,work function,spacing,cesium temperature and cesium pressure,etc.)was constructed.The optimized design of the molybdenum-nickel electrode cesium vapor TEC operating in ignited mode at the emitter temperature of 1800 K was carried out.The results showed that when the electrode spacing was 0.20 mm,the cesium reservoir temperature was 589.6 K,and the collector temperature was 1126.1 K,the energy conversion efficiency reached maximum of 11.18%.More consummated theoretical calculation models of electrical performance were established considering factors such as space barrier and the current from collector,which could be used to optimize the design of the collector temperature and work function.Furthermore,the optimal design schemes of the TEC in different modes were given.The results of this work would provide a certain reference for the development of high-efficiency TEC.