| Traditional heat engine plays an important role in the development of human society,but exhaust emissions also cause serious pollution to the environment.In this paper,the pyroelectric effect of PZT ceramics was used to design a solid state thermoelectric conversion device,which can realize the collection of low-grade heat in the environment,and convert it into electrical energy.The operation process of the heat engine is clean and zero emission,and the collection of waste heat is conducive to the restoration of the ecological environment.In the experiment,a quantized heat field was constructed on the surface of the heat engine by changing its surface absorption rate.The influence of non-uniform thermal field on the efficiency of thermoelectric conversion was investigated by control experiment,and the non-uniform heat field of different structures was designed to seek maximum optimization.Firstly,the theoretical model of pyroelectric effect was constructed and the theoretical surface temperature and output voltage of PZT solid state heat engine were deduced when the input light source was frequency modulated.Secondly,based on the theory of pyroelectric effect,three kinds of thermal engine samples with different absorption distributions of surface were designed: The electrode surface of no.1 heat engine has not been treated;the electrode surface of no.2 heat engine is completely covered with carbon ink layer;the electrode surface of no.3 heat engine is partially covered with carbon ink layer.Three kinds of heat engines were excited by constant light source and FM light source respectively.The results show that the larger the carbon ink layer coverage area,the higher temperature of the engine,the greater the temperature change rate,and the voltage is non-continuous output when the focused spot temperature of the light source is 125 and the light source is constant.Under the condition that the temperature of the input light source remains unchanged and the frequency is 0.1Hz,the third pyroelectric effect of no.3 heat engine is strengthened due to the non-uniform distribution of thermal field on the surface,and the output voltage is-0.84~0.96 V,80% higher than that of no.2 and 271% higher than that of no.1.Photo-thermal conversion efficiency of No.2 heat engine is enhanced because of covering with high absorptivity carbon ink layer in the surface,and voltage output is 108.3% higher than that of no.1.In order to explore the influence of the structure of non-uniform thermal field on the thermoelectric characteristics,other types of carbon ink layer structures were designed on the surface of the engine,and different non-uniform thermal fields were constructed under the excitation of FM light source.The thermal distribution and output voltage of the heat engine covered by different carbon ink layer structures were measured by experiments.The experimental results show that the ratio of the area of the carbon ink layer to the whole electrode surface affects the voltage output of the thermal engine when the pattern of the carbon ink layer is unchanged.When the carbon ink layer area is relatively large,the overall temperature difference of the engine is small,the expansion of material decreases,the third pyroelectric effect is weakened and the voltage output is reduced.When the carbon ink layer area is relatively small,the overall temperature of the engine decreases,the first and second pyroelectric effect is weakened and the output voltage decreases.Carbon ink layer area ratio of 77.8% of the generator has maximum voltage output.Increasing the number of discrete carbon ink layers make the output voltage increase and then decrease,in which the output voltage of the heat engine covered by four carbon ink layers is the largest when the area of carbon ink layer is unchanged and the number of discrete carbon ink layer changes. |
