發(fā)布時(shí)間：2018-07-17 01:13

【摘要】：目前,火力發(fā)電仍占我國電源結(jié)構(gòu)的大部分,地位舉足輕重。提高火電機(jī)組能源利用效率,對(duì)于提高國民經(jīng)濟(jì)的意義重大。火電機(jī)組運(yùn)行的經(jīng)濟(jì)性取決于很多方面,本文的研究方向就是如何提高電能生產(chǎn)過程中能量利用的效率。為了提高熱能的利用率,降低冷源損失,火電機(jī)組普遍采用再熱循環(huán)和回?zé)峒訜嵯到y(tǒng),來提高蒸汽循環(huán)的熱效率。本文的研究目標(biāo)就是如何分析或評(píng)價(jià)再熱循環(huán)和回?zé)峒訜嵯到y(tǒng)對(duì)機(jī)組循環(huán)熱效率的影響,包括在各種變工況條件下,再熱循環(huán)和回?zé)峒訜嵯到y(tǒng)運(yùn)行狀態(tài)的分析。由于工質(zhì)循環(huán)流動(dòng)的通道,結(jié)構(gòu)復(fù)雜,構(gòu)成了一個(gè)復(fù)雜的熱力系統(tǒng),各分支之間互相影響,要研究回?zé)嵯到y(tǒng)或再熱系統(tǒng),無法將它們孤立出來,必須將它們放入大的熱力系統(tǒng)中進(jìn)行研究。因此,本文以某真實(shí)火電機(jī)組的熱力系統(tǒng)為對(duì)象,研究熱力系統(tǒng)的分析方法及回?zé)嵯到y(tǒng)和再熱系統(tǒng)對(duì)工質(zhì)循環(huán)熱效率的影響。熱力系統(tǒng)的計(jì)算和分析方法較多,本文根據(jù)自身的研究目的,將熱力系統(tǒng)的分析計(jì)算方法簡化,分解為熱力系統(tǒng)流網(wǎng)計(jì)算和基于流網(wǎng)計(jì)算結(jié)果的焓值分布計(jì)算。將流體網(wǎng)絡(luò)理論思想引入熱力系統(tǒng)流網(wǎng)計(jì)算,通過合理假設(shè),將熱力系統(tǒng)流網(wǎng)的工質(zhì)流動(dòng)簡化為不考慮工質(zhì)換熱對(duì)工質(zhì)物性參數(shù)影響的一維、穩(wěn)態(tài)流動(dòng)問題,從而建立了熱力系統(tǒng)流網(wǎng)的等值電路模型,將復(fù)雜流網(wǎng)的質(zhì)量流量和壓力分布求解,轉(zhuǎn)化為直流電路的電流、電壓分布求解,再應(yīng)用基爾霍夫電壓、電流定律建立等值電路的數(shù)學(xué)模型,通過求解該模型獲得熱力系統(tǒng)流網(wǎng)的質(zhì)量流量和壓力分布。再根據(jù)機(jī)組設(shè)計(jì)參數(shù),建立熱力系統(tǒng)焓值分布模型,在熱力系統(tǒng)流網(wǎng)計(jì)算結(jié)果的基礎(chǔ)上,得到熱力系統(tǒng)焓值分布,進(jìn)而得到機(jī)組循環(huán)熱效率模型。通過研究,本文應(yīng)用流體網(wǎng)絡(luò)理論思想建立了熱力系統(tǒng)流體網(wǎng)絡(luò)計(jì)算模型,并建立了熱力系統(tǒng)焓值分布模型,通過將100%負(fù)荷、75%負(fù)荷、50%負(fù)荷、40%負(fù)荷和30%負(fù)荷5個(gè)工況的流網(wǎng)計(jì)算結(jié)果和焓值分布計(jì)算結(jié)果與該機(jī)組汽輪機(jī)熱力特性數(shù)據(jù)進(jìn)行比對(duì),驗(yàn)證了模型的準(zhǔn)確性。在此基礎(chǔ)上,本文給出了,應(yīng)用該模型求解機(jī)組運(yùn)行中典型問題的方法,包括熱力系統(tǒng)流網(wǎng)支路流阻變化、給水泵或凝結(jié)水泵揚(yáng)程變化、凝汽器壓力變化、加熱器水側(cè)管路泄漏等。在分析再熱蒸汽系統(tǒng)和回?zé)峒訜嵯到y(tǒng)對(duì)蒸汽循環(huán)熱效率的影響時(shí),本文定義了再熱蒸汽系統(tǒng)和回?zé)峒訜嵯到y(tǒng)有效度的概念。該定義可以反映再熱蒸汽系統(tǒng)和回?zé)峒訜嵯到y(tǒng)對(duì)蒸汽循環(huán)熱效率的影響方向,以及影響程度的相對(duì)大小。通過應(yīng)用本文建立的熱力系統(tǒng)分析方法,對(duì)目前部分機(jī)組提出增加0號(hào)高加的改造方案,進(jìn)行了分析計(jì)算。在計(jì)算結(jié)果中發(fā)現(xiàn),增加0號(hào)高加,在5個(gè)不同負(fù)荷工況,都可以提高蒸汽循環(huán)熱效率,但0段抽汽的循環(huán)有效度低于其他段抽汽。同時(shí)發(fā)現(xiàn),本文研究機(jī)組的回?zé)嵯到y(tǒng)并未工作在最佳狀態(tài),在不增加0號(hào)高加,而單純改變回?zé)嵯到y(tǒng)工作狀態(tài)的情況下,仍有提高機(jī)組循環(huán)熱效率的余地,這為我們提出了基于本文熱力系統(tǒng)分析方法的熱力系統(tǒng)優(yōu)化計(jì)算的新方向。
[Abstract]:At present, thermal power generation still accounts for most of the power supply structure in China. It is of great importance to improve the energy utilization efficiency of thermal power units. The economy of the thermal power unit depends on many aspects. The research direction of this paper is how to improve the efficiency of energy utilization in the process of electric energy production. In order to improve the thermal efficiency of steam cycle, the aim of this paper is to analyze and evaluate the effect of reheat cycle and reheating system on the thermal efficiency of the unit cycle, including reheat cycle and return under various condition conditions. The analysis of the running state of the thermal heating system. Because of the complex structure of the circulating flow of the working fluid, the complex structure is made up of a complex thermodynamic system, which affects each other. It is necessary to study the regenerative system or reheat system. It is impossible to isolate them. They must be put into a large thermodynamic system. Therefore, this paper is based on a real fire. The analysis method of thermal system and the influence of the heat system and reheat system on the thermal efficiency of the working fluid are studied. There are many methods of calculation and analysis of the thermodynamic system. In this paper, the analysis and calculation method of the thermodynamic system is simplified and decomposed into a flow net calculation and a flow net based on the thermodynamic system. The calculation of the enthalpy distribution of the calculated results is introduced. The fluid network theory is introduced into the flow network calculation of the thermodynamic system. Through the reasonable assumption, the working fluid flow in the flow network of the thermodynamic system is simplified as one dimension without considering the effect of the heat transfer on the physical property parameters of the working material and the steady flow problem, thus the equivalent circuit model of the flow net of the thermodynamic system is established, which will be complex. The mass flow and pressure distribution of the flow net are solved, converted into the current of the DC circuit, the solution of the voltage distribution, and then the mathematical model of the equivalent circuit by using the Kirchhoff voltage and the current law. By solving the model, the mass flow and pressure distribution of the flow net of the thermodynamic system are obtained. Then the enthalpy points of the thermodynamic system are established according to the design parameters of the unit. On the basis of the calculation results of the thermodynamic system flow net, the distribution of enthalpy distribution of the thermodynamic system is obtained, and the heat efficiency model of the unit cycle is obtained. Through the study, the fluid network calculation model of the thermodynamic system is established by using the theory of fluid network, and the enthalpy distribution model of the thermodynamic system is established, through which the 100% load, the 75% load, and 50% are used. The calculation results of flow net calculation and enthalpy distribution of the load, 40% load and 30% load are compared with the steam turbine thermodynamic characteristics data, and the accuracy of the model is verified. On this basis, this paper gives the method to solve the typical problems in the operation of the unit, including the flow resistance change of the flow net branch of the thermodynamic system, In the analysis of the effect of reheat steam system and reheating system on the thermal efficiency of steam cycle, the concept of the reheat steam system and reheating system is defined. This definition can reflect the reheat steam system and the reheat addition. The influence of the thermal system on the thermal efficiency of the steam cycle and the relative size of the influence degree. Through the application of the thermal system analysis method established in this paper, an analysis and calculation for the increase of the 0 number of units at present is put forward. It is found that the increase of number 0 increases in the calculation results and can be improved in 5 different load conditions. The steam cycle heat efficiency, but the cycle efficiency of the 0 section extraction is lower than that of the other sections. It is found that the regenerative system of the unit does not work in the best state, and there is still a room for improving the thermal efficiency of the unit under the condition that the regenerative system is not increased and the working state of the regenerative system is simply changed. A new direction for optimization of thermodynamic system in text thermal system analysis.
【學(xué)位授予單位】：華北電力大學(xué)(北京)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM621.4

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