【作者】 肖春华；

【导师】 桂业伟；

【作者基本信息】 中国空气动力研究与发展中心 ， 流体力学， 2010， 博士

【摘要】 飞机结冰是导致飞行安全事故的主要隐患之一,飞机的防/除冰系统是提高飞机的安全性能、减少结冰事故的重要装置。由于高效率、低能耗、易控制的优势,电热除冰已成为目前重要的除冰方法之一。针对国内在电热除冰领域的研究才刚刚开始、研究水平远远落后于发达国家的现状,开展飞机电热除冰机理和规律的研究,对于冰防护理论的完善、相关技术的发展和防/除冰系统的研制,从而保障飞机的飞行安全有着至关重要的作用。本文采用理论分析、数值计算和实验方法相结合的手段,围绕飞机电热除冰过程中涉及到的相变传热特性、冰壳现象及其影响、热力耦合特性和冰脊形成特征等问题展开研究,以期揭示电热除冰过程的原理和机制、掌握影响电热除冰效率的规律,为现行电热除冰系统的改进和完善,以及新型电热除冰技术的开发提供理论基础和技术支撑。全文分六章,各章内容概况如下:第一章是引言。阐述了飞机电热除冰研究的重要性,论述了国内外电热除冰研究的概况,分析了存在的问题和国内研究的差距,最后扼要介绍了本文的工作。第二章是电热除冰过程中的传热特性研究。采用有限体积法和热焓方法,将传统相变模型应用到飞机电热除冰计算中,系统研究了冰层在电热除冰过程中的相变传热特性,重点研究了加热模式、冷却时间、加热功率、单元间隔对相变传热特性的影响,研究了冰脱落对传热特性的影响。并通过结冰风洞实验验证了电热除冰过程的一些重要的传热规律和特性。研究表明,高功率周期性加热方式比低功率连续性加热方式更经济有效。第三章是电热除冰过程中的冰壳及其影响研究。针对机翼前缘结冰的冰壳现象,采用理论分析的方法,建立了前缘冰壳在外力作用下的融化模型,计算研究了外部流场压力和冰自重对冰壳融化特性的影响。采用实验的方法,在结冰风洞中印证了前缘冰壳现象,并对冰壳的滑动现象进行了分析,获得了冰壳对电热除冰的影响规律。研究表明,外部气动力加速了前缘冰壳的融化,但同时却大大延长了冰壳脱落的时间,冰壳将对气动性能造成了恶劣的影响。第四章是电热除冰过程中的热力耦合效应研究。采用有限元方法和非结构网格技术,研究了气动力载荷作用下的冰层内部应力分布特性,并在此基础上研究了电加热条件下冰层内部的应力分布特性。研究发现,在低速条件下,气动力对冰脱落的贡献不大。但在电热除冰条件下,热力耦合效应将造成冰层内部应力的显著增加,从而造成冰层内部的破裂,加速冰层的破坏。最后采用实验方法,在结冰风洞中验证了热力耦合特性对除冰过程的影响。第五章是电热除冰过程中的冰脊形成机理研究。采用实验方法,在结冰风洞中模拟了电热除冰过程中的冰脊形成过程,研究了结冰环境温度、来流速度和加热功率对冰脊形成和特征的影响。基于实验得到的冰脊形状,计算分析了冰脊的生长规律。研究发现,冰脊是从冰防护区外下游某位置开始产生,逐渐往冰防护区发展。第六章是结束语。总结了论文的主要工作、研究成果和创新,指出了下一步的研究内容和方向。更多还原

【Abstract】 Ice accretion is one of primary hazards to flight safety. Aircraft anti/de-icer is important equipment which can improve airplane safety performance and can reduce flight icing accident. Due to high efficiency, low energy consumption and easy to control, electrothermal deicing is becoming one of the most widely applied techniques of aircraft deicing. The development of ice protection theory and deicing technique is important for flight safety. It is vital to carry out the study of aircraft electrothermal deicing mechanism and law, especially because domestic study of aircraft electrothermal deicing just begins and level of study lags far behind developed countries.By means of theoretical analysis, numerical simulation and experiment, phase-change heat transfer characteristic, ice shell phenomenon and its effect, coupled thermo-mechanical characteristic and ice ridge formation characteristic are studied in this thesis. The study focuses on revealing electrothermal deicing mechanism and understanding the influence on deicing efficiency. The research results will not only provide the theoretical basis for the improvement of present electrothermal deicing system, but also provide the technical support for the development of new deicing technique.This thesis is divided into six chapters as follows:The first chapter is the introduction. The significance and status of the investigation for aircraft electrothermal deicing, the problems and gaps between home and abroad investigation are reviewed. The present research work of this thesis is also described briefly in this chapter.In the second chapter, the study of heat transfer characteristics during aircraft electrothermal deicing process is presented. The traditional phase-change model is applied to the simulation of aircraft electrothermal deicing by using finite volume method based on enthalpy model. The ice phase-change heat transfer characteristics during electrothermal deicing process are studied systemically. The research emphasis is on the effects of heating manner, cooling time, heater power density and heater gap width on phase-change heat transfer characteristics, as well as the effects of ice shedding on heat transfer characteristics. Finally, some important heat transfer characteristics during electrothermal deicing process are confirmed in icing wind tunnel. The study shows that periodic heating manner under high power is superior to continuous heating under low power when reasonable cooling time and heating power density are adopted. Chapter 3 presents ice shell phenomenon and its effects on electrothermal deicing on the leading edge of aerofoil. Combined with the effect of external forces, melting model is established by theoretical analysis. Effects on ice shell melting characteristics of aerodynamic pressure and gravity are investigated. Furthermore, Ice shell phenomenon is confirmed in icing wind tunnel. Ice sliding is analyzed theoretically. Ice shell and its effects are obtained in this chapter. The research result shows that aerodynamics pressure increases the melting speed of ice shell and delays the ice shell shedding simultaneously. Ice shell results in severe aerodynamics performance.The study of coupled thermo-mechanical characteristics is presented in chapter 4. The effect of aerodynamics on stress distribution characteristics in the ice layer is studied by finite element method based on unstructured mesh. Furthermore, the effect on stress distribution characteristics of electrical heating is studied. The study shows that stresses in the ice layer caused directly from aerodynamic loading are not significant when the flight velocity is low. While coupled thermo-mechanical characteristic leads to remarkable increasing of stresses in the ice under the condition of electrothermal deicing. Consequently, it results in crack in the ice and speeds up ice shedding. Finally, the effects on deicing of coupled thermo-mechanical characteristics are validated in icing wind tunnel.Chapter 5 is the investigation of ice ridge formation mechanism during electrothermal deicing process. The ice ridge formation is tested in icing wind tunnel. The effects on ice ridge formation of icing temperature, inflow velocity and heater power density are investigated. Combined with ice ridge formation obtained by experiment, the mechanism and growth of ice ridge formation are further analyzed. The study shows that ice ridge is formed far apart from the ice protection region and grows forward gradually.The concluding remarks are given in chapter 6. The summary of current work is presented and expectation for future work is pointed out as well.更多还原