柴油機(jī)余熱回收溫差發(fā)電—有機(jī)朗肯聯(lián)合循環(huán)變工況性能研究
發(fā)布時(shí)間：2018-08-18 13:26
【摘要】：節(jié)能和環(huán)保是汽車工業(yè)發(fā)展的兩大主題。有關(guān)研究表明,發(fā)動(dòng)機(jī)燃料燃燒所發(fā)出的能量只有三分之一左右被有效利用�；厥绽眠@部分能量已經(jīng)成為了提高內(nèi)燃機(jī)效率重要的方式之一。其中,溫差發(fā)電(TEG)技術(shù)具有可耐高溫、無運(yùn)動(dòng)部件等優(yōu)點(diǎn),是適合柴油機(jī)排氣余熱這種中高溫品位余熱回收的技術(shù)手段;有機(jī)朗肯循環(huán)(ORC)具有運(yùn)行穩(wěn)定、效率高等特點(diǎn),但是受限于工質(zhì)的高溫分解問題,適合于內(nèi)燃機(jī)余熱的回收中低溫品位余熱回收。柴油機(jī)變工況下排氣溫度較高且變化范圍較大,可使用TEG系統(tǒng)預(yù)先對(duì)高溫的排氣進(jìn)行回收,將排氣溫度降到有機(jī)工質(zhì)適宜工作的范圍,為ORC系統(tǒng)回收余熱創(chuàng)造有利條件。因此,TEG和ORC的聯(lián)合循環(huán)對(duì)柴油機(jī)變工況下的余熱能進(jìn)行回收是本文的研究重點(diǎn)。本文基于MATLAB建立了TEG與ORC聯(lián)合系統(tǒng)的熱力學(xué)模型,對(duì)某型柴油機(jī)開展了變工況余熱回收的模擬研究。根據(jù)柴油機(jī)排氣余熱溫度特性,TEG系統(tǒng)材料選擇工作溫度在300~600攝氏度范圍的p型TAGS(碲銻鍺銀)/n型PbTe材料。ORC系統(tǒng)為帶回?zé)嵯到y(tǒng),可以進(jìn)一步提升回收效率,系統(tǒng)有機(jī)工質(zhì)為R123,其分解溫度為600K。鑒于工況點(diǎn)較多,為使ORC系統(tǒng)在不同排氣溫度工況點(diǎn)下都可以穩(wěn)定工作,且蒸發(fā)壓力過大對(duì)系統(tǒng)穩(wěn)定性有影響,所以選用較低蒸發(fā)壓力以保證系統(tǒng)安全正常運(yùn)行,故ORC系統(tǒng)朗肯循環(huán)狀態(tài)為亞臨界,工質(zhì)蒸發(fā)壓力為2MPa,冷凝溫度為308K。分析結(jié)果表明,此聯(lián)合系統(tǒng)基本可在柴油機(jī)全工況下運(yùn)行。柴油機(jī)中高負(fù)荷時(shí)排氣溫度和流量相對(duì)較大,聯(lián)合回收系統(tǒng)的輸出功較高。聯(lián)合系統(tǒng)在不同工況下的輸出功最高可達(dá)30.36kW。其中TEG系統(tǒng)輸出功為2.24kW,ORC系統(tǒng)輸出功為28.12kW。發(fā)動(dòng)機(jī)指示熱效率最高可以提高5.52%,其指示熱效率最高值為47.1%。聯(lián)合系統(tǒng)在1700-1900r/min轉(zhuǎn)速,70%-90%負(fù)荷這一工況范圍下性能表現(xiàn)更好,若柴油機(jī)常在中高轉(zhuǎn)速大負(fù)荷工況下運(yùn)行,則使用此系統(tǒng)回收余熱具有較大的經(jīng)濟(jì)價(jià)值。本文還設(shè)計(jì)并制作多模塊串聯(lián)的溫差發(fā)電裝置進(jìn)行實(shí)驗(yàn)研究,探究了溫差發(fā)電系統(tǒng)不同的冷熱端溫度下的伏安特性規(guī)律以及電流、輸出功率關(guān)系。實(shí)驗(yàn)結(jié)果表明,冷端溫度293K,熱端溫度473K時(shí)溫差發(fā)電裝置有最大輸出功率39.648W。并使用此實(shí)驗(yàn)結(jié)果對(duì)TEG-ORC聯(lián)合系統(tǒng)中TEG系統(tǒng)的理論模型進(jìn)行了針對(duì)多模塊串聯(lián)后的修正,使其更能真實(shí)反映多模塊串聯(lián)后的溫差發(fā)電系統(tǒng)回收余熱的能力。此實(shí)驗(yàn)可以為聯(lián)合系統(tǒng)模型修正優(yōu)化以及TEG-ORC聯(lián)合循環(huán)的實(shí)驗(yàn)研究進(jìn)行前期的鋪墊,有助于今后聯(lián)合系統(tǒng)實(shí)驗(yàn)工作的開展。
[Abstract]:Energy saving and environmental protection are the two main themes of automobile industry development. Studies have shown that only about 1/3 of the energy emitted by engine fuel combustion is effectively utilized. Recycling this part of energy has become one of the most important ways to improve the efficiency of internal combustion engine. Among them, thermoelectric (TEG) technology has the advantages of high temperature resistance, no moving parts and so on. It is suitable for diesel engine exhaust heat recovery of medium and high temperature grade waste heat, organic Rankine cycle (ORC) has the characteristics of stable operation, high efficiency, etc. However, due to the high temperature decomposition of working fluid, it is suitable for the recovery of internal combustion engine waste heat. The exhaust temperature of diesel engine under different working conditions is higher and the range of variation is large. The exhaust temperature of high temperature can be recovered by using TEG system in advance, and the exhaust temperature can be reduced to the suitable working range of organic working medium, which will create favorable conditions for the recovery of residual heat in ORC system. Therefore, the combined cycle of TEG and ORC is the focus of this paper. In this paper, the thermodynamic model of TEG and ORC combined system is established based on MATLAB, and the simulation study of waste heat recovery in a diesel engine is carried out. According to the waste heat temperature characteristics of diesel engine exhaust gas, the material of TEG system can be selected as the back heat system of p type TAGS (Ag Te / n type PbTe system) with working temperature in the range of 600C, and the recovery efficiency can be further improved. The organic working fluid of the system is R123 and its decomposition temperature is 600K. In view of the large number of operating conditions, in order to make the ORC system work stably under different exhaust temperature conditions, and the excessive evaporation pressure has an effect on the stability of the system, the lower evaporation pressure is selected to ensure the safe and normal operation of the system. Therefore, the Rankine cycle state of ORC system is subcritical, the evaporation pressure of the working medium is 2 MPA, and the condensation temperature is 308 K. The analysis results show that the combined system can be operated in the whole working condition of diesel engine. The exhaust temperature and flow rate of the diesel engine are relatively large at medium and high loads, and the output power of the combined recovery system is higher. The output power of the combined system can reach 30.36 kW under different working conditions. The output power of TEG system is 2.24kW and 28.12kW. The maximum indicated thermal efficiency of the engine can be increased by 5.52 and the maximum indicated thermal efficiency is 47.1. The performance of the combined system is better in the range of 70% to 90% 1700-1900r/min speed. If the diesel engine is often operated under the conditions of medium and high speed and high load, it is of great economic value to use the system to recover the waste heat. This paper also designs and makes a multi-module thermoelectricity generator in series for experimental study, and probes into the law of volt-ampere characteristic and the relationship between current and output power of thermoelectric power generation system under different temperature of cold and hot end. The experimental results show that the maximum output power is 39.648W when the cold end temperature is 293K and the hot end temperature is 473K. Using the experimental results, the theoretical model of the TEG system in the TEG-ORC joint system is modified for the multi-module series-connected system, so that it can more truly reflect the ability of recovering the residual heat of the thermoelectric power generation system after the multi-module series-connected system. This experiment can pave the way for the experimental research of the joint system model modification and optimization and the TEG-ORC joint cycle, which is helpful to the joint system experiment in the future.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM913;TK115
本文編號(hào)：2189608
[Abstract]:Energy saving and environmental protection are the two main themes of automobile industry development. Studies have shown that only about 1/3 of the energy emitted by engine fuel combustion is effectively utilized. Recycling this part of energy has become one of the most important ways to improve the efficiency of internal combustion engine. Among them, thermoelectric (TEG) technology has the advantages of high temperature resistance, no moving parts and so on. It is suitable for diesel engine exhaust heat recovery of medium and high temperature grade waste heat, organic Rankine cycle (ORC) has the characteristics of stable operation, high efficiency, etc. However, due to the high temperature decomposition of working fluid, it is suitable for the recovery of internal combustion engine waste heat. The exhaust temperature of diesel engine under different working conditions is higher and the range of variation is large. The exhaust temperature of high temperature can be recovered by using TEG system in advance, and the exhaust temperature can be reduced to the suitable working range of organic working medium, which will create favorable conditions for the recovery of residual heat in ORC system. Therefore, the combined cycle of TEG and ORC is the focus of this paper. In this paper, the thermodynamic model of TEG and ORC combined system is established based on MATLAB, and the simulation study of waste heat recovery in a diesel engine is carried out. According to the waste heat temperature characteristics of diesel engine exhaust gas, the material of TEG system can be selected as the back heat system of p type TAGS (Ag Te / n type PbTe system) with working temperature in the range of 600C, and the recovery efficiency can be further improved. The organic working fluid of the system is R123 and its decomposition temperature is 600K. In view of the large number of operating conditions, in order to make the ORC system work stably under different exhaust temperature conditions, and the excessive evaporation pressure has an effect on the stability of the system, the lower evaporation pressure is selected to ensure the safe and normal operation of the system. Therefore, the Rankine cycle state of ORC system is subcritical, the evaporation pressure of the working medium is 2 MPA, and the condensation temperature is 308 K. The analysis results show that the combined system can be operated in the whole working condition of diesel engine. The exhaust temperature and flow rate of the diesel engine are relatively large at medium and high loads, and the output power of the combined recovery system is higher. The output power of the combined system can reach 30.36 kW under different working conditions. The output power of TEG system is 2.24kW and 28.12kW. The maximum indicated thermal efficiency of the engine can be increased by 5.52 and the maximum indicated thermal efficiency is 47.1. The performance of the combined system is better in the range of 70% to 90% 1700-1900r/min speed. If the diesel engine is often operated under the conditions of medium and high speed and high load, it is of great economic value to use the system to recover the waste heat. This paper also designs and makes a multi-module thermoelectricity generator in series for experimental study, and probes into the law of volt-ampere characteristic and the relationship between current and output power of thermoelectric power generation system under different temperature of cold and hot end. The experimental results show that the maximum output power is 39.648W when the cold end temperature is 293K and the hot end temperature is 473K. Using the experimental results, the theoretical model of the TEG system in the TEG-ORC joint system is modified for the multi-module series-connected system, so that it can more truly reflect the ability of recovering the residual heat of the thermoelectric power generation system after the multi-module series-connected system. This experiment can pave the way for the experimental research of the joint system model modification and optimization and the TEG-ORC joint cycle, which is helpful to the joint system experiment in the future.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM913;TK115
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