【作者】 刘爱虢；

【导师】 翁一武；

【作者基本信息】 上海交通大学 ， 动力工程与工程热物理， 2010， 博士

【摘要】 从上个世纪末开始,各国科研人员就开始了对熔融碳酸盐燃料电池/微型燃气轮机(MCFC/MGT)混合动力系统的研究。通过对这种新型的混合动力系统的研究,人们发现燃料电池/燃气轮机混合动力系统具有传统动力系统所不具有的优点,其能量转化效率和污染物的排放水平都达到了令人满意的水平。因此,目前这种混合动力系统已成为各国重点发展的新能源技术。在本文中,首先应用数学手段建立了燃料电池及混合动力系统的仿真模型,对电池和系统在设计工况、非设计工况的稳态和动态特性进行了详细的分析。燃料电池的尾气中有部分没有完全反应的燃料,这部分燃料具有可燃成分含量少、流动速度快等特点,这些特点使得在混合动力系统中需要应用催化燃烧。催化燃烧室可以将这部分能量继续转化,从而可以提高系统效率、改善系统性能、降低系统污染物排放,因此在混合动力系统中必需采用催化燃烧室。同时,催化燃烧室的应用还为混合动力系统的燃料多样化提供了必要的基础。在对催化燃烧室进行了详细的理论分析的基础上,设计搭建了催化燃烧实验平台,对催化燃烧进行了深入的实验研究。本文所做的工作为MCFC/MGT混合动力系统的实际开发和应用提供了必要的理论指导和实验基础。本文主要在以下几个方面取得了一定的进展。(1)燃料电池数学模型的建立基于质量、能量、动量守恒原理和热力学特性,考虑各种极化损失、传热形式及详细的气体特性,建立了熔融碳酸盐燃料电池的数学模型。在模型的建立过程中考虑了热力学和电化学两个方面,考虑了电流密度场与温度场之间的偶合关系。考虑了反应气体的温度、流量、组分及相应的热力学特性沿流动方向的变化,合理的处理温度场和电流密度场、反应气体组分场的耦合关系。在热力学模型的建立过程中不仅考虑了各种传热形式导致的热量传递,同时也考虑了由传质所引起的能量转移。在电化学模型的建立过程中,计算极化特性时使用的是由实验回归拟合数据。在对混合动力系统的研究中,建立考虑了如此多参数详细的燃料电池模型并不多见。详细的燃料电池模型可以为系统特性变化时分析燃料电池的具体反应特性提供必要的条件。所建立的数学模型中包括非线性的偏微分方程,温度和流量之间存在耦合关系。为了提高数学模型的求解速度实现模型的快速求解,引入了容阻特性建模和分布-集总参数法将复杂的偏微分方程进行了转换,建立了适用于快速动态仿真的电池模型。利用该模型分析了某一工况下熔融碳酸盐燃料电池的性能,通过与实验数据的对比表明,该模型可以反映熔融碳酸盐燃料电池的特性。(2)混合动力系统模型建立及变负荷特性分析在系统设计过程中考虑采用增压型MCFC。由MCFC对工作压力的要求及模块化设计的特点,在本文中突破了传统的基于MCFC的混合动力系统的设计,而是采用了基于现有燃气轮机的混合动力系统的设计。建立了系统的稳态、动态模型,对混合动力系统大范围工况变动情况下的热力系统特性、控制对象调节等特性进行了研究,揭示出混合动力系统特性变化的机理和规律。对系统采用不同的运行方式时的非设计工况特性进行了比较,分析了不同运行方式对系统的影响。对系统在启动、关机、负荷变化等的动态特性进行了研究。针对所研究系统的特点,对系统启动关机过程中可能出现的问题及对系统产生的影响进行了分析,并提出了相应的解决策略。为将系统从冷态启动到正常运行及从正常运行到关机,在系统中加入了一系列的辅助设备,以保证系统安全正常的启动关机。针对所研究的系统,提出了详细的启动关机步骤,并应用数学模型对系统启停过程中的特性进行了研究,为实验系统的控制与管理提供借鉴。(3) MCFC/MGT混合动力系统催化燃烧特性研究应用数学的手段建立了催化燃烧室的数学模型,所建立的数学模型是基于详细的化学反应动力学的分布参数的微通道模型,并将模型计算结果与实验结果进行了对比,确认了模型的准确性。应用数学模型,分析了混合动力系统在启动、设计工况及非设计工况运行时催化燃烧室的反应特性及不同运行参数和燃料成分对燃烧室特性的影响。在数值模拟的基础上搭建了催化燃烧实验平台,对催化燃烧室的特性进行了实验分析。在所搭建的催化燃烧实验平台上,对混合动力系统在不同工况时燃烧室的工作特性进行了研究。应用了七种不同的金属氧化物催化剂,针对混合动力系统在启动和正常运行时催化燃烧的反应特性进行了实验研究。分析了不同的运行参数(如入口温度、流速等)对燃料转化率的影响,研究了不同燃料及混合气在应用不同的催化剂时的反应特性。所获得的实验结果,对于催化燃烧室的应用及混合动力系统的建立都具有重要意义。更多还原

【Abstract】 Many researchers have begun the research on the molten carbonate fuel cell/micro-gas turbine (MCFC/MGT) since the end of last century. People found the MCFC/MGT hybrid system has the advantages different from traditional power system, in which the energy conversation rate and level of pollution emission all reached a satisfactory level according to the research on this new kind of hybrid system. Nowadays many countries have focused on the development of this new kind of energy technologies. In this paper, the simulation modeling of MCFC/MGT hybrid system has been built up firstly. And then the performance of MCFC and hybrid system on design and off-design conditions have been analyzed carefully using the mathematic modeling. There is some fuel in the exhaust of fuel cell with the characteristics of low heat value and higher flowing speed. These characteristics make the catalytic combustor is necessary to the hybrid system. The whole efficiency can be higher, the properties can be improved and the contamination outlet can be decreased when the catalytic combustion techinique is connected with the hybrid system. At the same time the catalytic combustor can provide the base for the use of different fuel. Based on the theoretical analysis in detail, a experimental platform has been built up for the the purpose of deeply understanding of the catalytic combustion. Some experiments have been performed on the experimental platform. The work performed in this paper can provided the necessary theoretical guide and experimental base for the development and use of MCFC/MGT hybrid system. Some developments have been achieved as follows.(1) Numerical model of fuel cellA one-dimensional mathematical model for molten carbonate fuel cell has been built. The mass, monument, energy, specifies mass balance equations and thermodynamic properties have been included, at the same time the different polarization loss, heat conversation ways and detailed gas characteristics have been considered in the modeling. During the building of modeling the thermodynamic and electrochemical characteristics have been considered, the coincidence between the current density field and temperature field were also included. The temperature, flux, compositions and related thermal characteristics will change along the flowing direction which should be considered. And the solution of coupling relation between temperature field, current density field and gas compositions is very important. The energy transfer methods considered include not only different heat transfer methods but the energy transfer connected with the mass transfer during the foundation of the thermodynamic mdel. The data for the polarization properties are from the experiment for the electrochemical model. The fuel cell model with so detailed parameters is rare for the study of hybrid system. The detailed fuel cell model can provide the detailed information about the fuel cell when the properties of the hybrid system changed. In the mathematic modeling there exists non-linear partial differential equations and the temperature and flow exits coupling relationship which cause the difficulties to solve the modeling quickly. Using the V-R (volume-resistance) modeling and distributed and lumped parameter method the partial differential equations for cell mass and momentum balance can be changed to ordinary differential equations which met the demand for real-time dynamic simulation. Steady state and dynamic characteristics of MCFC have been analyzed using the model. The results indicate that the V-R characteristic modeling method is valuable and viable in the MCFC system, and the model can be used for the simulation of MCFC.(2) Foundation of hybrid system and variable load performance analysisThe pressurized MCFC has been considered during the system design. The traditional design method based on MCFC has been broken through instead of using a more meaningful hybrid system design method based on a commercial available micro-gas turbine according to the MCFC working pressure requirement and modular design feature. Establishing the steady-state and dynamic model of the hybrid system, the thermal characteristic, regulation of controlled object and other characteristics have been studied for the hybrid system under wide range working condition changes. The mechanism and laws of hybrid system characteristics changes has been revealed. The non-design operation characteristics of hybrid system have been compared under different operation methods. The effects of different operation methods on the system characteristics were analyzed. The dynamic characteristics of hybrid system at starup, shutdown and load change have been studied. The problems and impact on the system occurred during the startup and shutdown have been analyzed according to the characteristics of the system. The corresponding solution strategies have also been mentioned. A series of auxiliary equipment have been added into the system for the system startup and shutdown, which can ensure the system security. The detailed steps for the system startup and shutdown have been presented for the studied system, and the system statup and shutdown characteristics have been calculated using the mathmatics model. This work can become a reference to the system control and management for the experimental system.(3) Research on the characteristics of catalytic combustion in the MCFC/MGT hybrid systemThe concept has ever been mentioned for the research of MCFC/MGT hybrid system, but the associated experiments have never been done. In this paper, a mathematical model of catalytic combustion chamber has been built. The mathematical model is a micro-channel model of one-dimensional distributed parameters based on a detailed chemical kinetic parameters. The accuracy of mathematic model was confirmed according to the comparison between the calculations and experimental results. The operations of catalytic combustion chamber including startup, design point and off-design point have been analyzed, at the same time the effects of different fuel compositions and operation parameters on the operations of catalutic combustion chamber have also been studied based on the model. The catalytic combustion experimental platform has been built for the experimental analysis to the catalytic combustion based on the results from calculations. The working characteristics of catalytic combustion burner of hybrid system under different working conditions have been analyzed on the experimental platform. The catalytic combustion reaction characteristics for the system starup and normal operation are studied experimentally for 7 different kinds of mental oxide catalysts. The effects of different operation parameters, such as inlet temperature, flow rate and so on, on the fuel conversion rate are analyzed; the reaction characteristics of different fuels and synthetic gas are studied when using different catalyst. The experimental results are important to the use of catalytic combustor and the foundation of the hybrid system.更多还原