零碳/低碳燃料固体氧化物燃料电池-发动机联合动力系统热力学分析

Thermodynamic Analysis for Zero-Carbon and Low-Carbon Fuel on SOFC-Engine Hybrid Power System

为响应能源动力领域低碳节能的战略需求,促进固体氧化物燃料电池(SOFC)商业化应用,设计了一种SOFC-发动机联合动力系统,以NH_(3)、H_(2)、天然气为燃料,并结合尾气余热梯级利用技术。首先建立并验证了系统的数学模型,然后对系统模型进行了热力学分析,探究了不同零碳燃料、低碳燃料应用时关键参数对系统性能的影响。结果表明:燃料流率增大时系统效率无明显变化,H_(2)作燃料时SOFC与发动机子模块效率最佳,但使用NH3系统总效率最高,可达81.96%;当量比保持在1时可使系统整体效率达到最优;蒸汽燃料比从0.8降低到0.2时系统总效率随之升高,但其过低也会导致系统经济性变差;理想条件下,该系统应用在动力机械装置中时,考虑到SOFC装置与发动机模块的耦合性,SOFC工作温度维持在600℃~650℃为宜。

To respond to the current strategic demand for low-carbon and energy conservation in the energy power field and promote the commercialization of solid oxide fuel cell(SOFC), a SOFC-engine hybrid system is put forward by taking NH_(3), H_(2) and natural gas as fuels and using the cascade utilization technology of residual heat from tail gas. First, the mathematical model of the hybrid system is established and verified. Then, the thermodynamic analysis of the system model is carried out to explore and analyze the influence of key parameters on system performance in the application of different zero-carbon or low-carbon fuels. The results show that the increase of fuel flow rate has no obvious effect on system efficiency;the efficiency of both SOFC and engine modules reach the best when H_(2) is used as the fuel, and the overall system efficiency achieves the highest, up to 81.96%, when NH3is used as the fuel;the most optimal overall system efficiency can be achieved when the equivalent ratio is kept at 1;the overall system efficiency increases with the decrease of the steam-fuel ratio from 0.8 to 0.2, but the too low steam-fuel ratio will still lead to poor system economy. Under ideal conditions, considering the coupling between the SOFC device and engine module, the SOFC operating temperature should be maintained at 600-650 ℃ when the system is applied to power mechanical devices.