【摘要】：熱電材料作為一種綠色環(huán)保的新型能源材料,近年來受到廣泛關(guān)注,但是熱電材料較低的能量轉(zhuǎn)換效率限制了它的應(yīng)用和商業(yè)推廣。由于數(shù)學(xué)上的困難,目前的研究大部分都是關(guān)于熱電材料穩(wěn)態(tài)問題的研究,而關(guān)于非穩(wěn)態(tài)問題的研究少之又少。本文利用積分變換方法求解了一維和二維的含時非穩(wěn)態(tài)問題,研究了特定尺寸特定邊界條件下,電流密度與能量轉(zhuǎn)換效率的關(guān)系,并對非穩(wěn)態(tài)問題的電流密度進(jìn)行了優(yōu)化。對于一維非穩(wěn)態(tài)問題,本文對比了非穩(wěn)態(tài)和穩(wěn)態(tài)效率的差異,分析了造成非穩(wěn)態(tài)效率低于穩(wěn)態(tài)效率的主要原因,之后求解了一維熱電材料中的熱應(yīng)力隨時間的變化。對于二維問題,本文研究了含單邊裂紋熱電材料板在非穩(wěn)態(tài)溫度場下的熱應(yīng)力問題,進(jìn)而還研究了裂紋尖端的應(yīng)力強(qiáng)度因子在非穩(wěn)態(tài)溫度場下隨時間的變化。結(jié)果表明,通過調(diào)節(jié)電流的形式可以調(diào)節(jié)熱電材料在非穩(wěn)態(tài)期間各個時刻的能量轉(zhuǎn)換效率,在本文中,得到了一種效果較好的電流密度形式,使得熱電材料的能量轉(zhuǎn)換效率得到了提高。一維材料的熱應(yīng)力以及二維材料裂紋尖端的應(yīng)力強(qiáng)度因子均隨著時間變化,直到最后趨于穩(wěn)定。這些解析解答和結(jié)論為提高熱電材料在非穩(wěn)態(tài)情況下的可靠性及能量轉(zhuǎn)換效率提供了有力的工具。
[Abstract]:Thermoelectric materials, as a new kind of green energy materials, have been paid more and more attention in recent years. However, the low energy conversion efficiency of thermoelectric materials limits its application and commercial promotion. Due to the difficulty in mathematics, most of the current studies are on the steady state of thermoelectric materials, but there are few researches on the unsteady state problems. In this paper, the integral transformation method is used to solve the time-dependent unsteady problems of one and two dimensions. The relationship between the current density and the energy conversion efficiency is studied under the condition of specific size and specific boundary, and the current density of the unsteady problem is optimized. For one dimensional unsteady state problem, the differences between unsteady and steady state efficiency are compared, and the main reasons for the unsteady efficiency being lower than steady state efficiency are analyzed, and then the variation of thermal stress with time in one dimensional thermoelectric material is solved. For the two-dimensional problem, the thermal stress of a thermoelectric plate with a single crack under the unsteady temperature field is studied, and the variation of the stress intensity factor at the crack tip with time under the unsteady temperature field is also studied. The results show that the energy conversion efficiency of thermoelectric materials can be adjusted by adjusting the current form at various times during the unsteady state. In this paper, a better current density form is obtained. The energy conversion efficiency of thermoelectric materials is improved. The thermal stress of one dimensional material and the stress intensity factor at the crack tip of two dimensional materials all change with time until they tend to stabilize at last. These analytical solutions and conclusions provide a powerful tool for improving the reliability and energy conversion efficiency of thermoelectric materials under unsteady conditions.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB34

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