Reducing greenhouse gases, saving energy resources and mass optimization require technological changes towards increasingly electric vehicles. At the same time, performance improvement of semiconductor and dielectric ...Reducing greenhouse gases, saving energy resources and mass optimization require technological changes towards increasingly electric vehicles. At the same time, performance improvement of semiconductor and dielectric materials further promotes electronic components confinement, resulting in a significant increase of embedded power densities. In the particular case of future hybrid propulsion aircrafts, electrical power that intended to supply reactors would be converted through power electronics components mounted on power busbars and insulated by solid dielectrics materials. These dielectrics materials have to respond to various electrical constraints of use (HVDC), in spite of environment change of aircraft parameters such as low pressure, temperature and thermal cycles, humidity... Unfortunately, partial discharges phenomenon is the most problem within electrical insulation system (EIS). Based on a topological model of power busbars designed for power converters dedicated to hybrid aircraft, partial discharge studies were conducted by simulation in various charging conditions of a PTFE insulator. Simulation results, which focus on electric field thresholds criteria of partial discharge inception voltage in air, reveal a net sensitivity of a space charge accumulation and distribution on dielectrics behaviour even for low space charge density, depending on their location in dielectrics. Compared to the behaviour observed with implanted homocharges, when by increasing homocharges density from 0.5 C/m3 to 2 C/m3 we observe a decrease of electric field by 450%, simulation results show a highest risk of partial discharge inception when heterocharges are accumulated inside dielectrics. Their accumulation increases the electric field in triple points beyond electric field thresholds of partial discharge inception in air. The simulated electric field reaching 22 kV/mm with only 2 C/m3 of heterocharges density accumulated in dielectric/busbars interfaces.展开更多
以分布式混合电推进飞行器技术研究为背景,针对分布式动力翼在前飞状态下动力/气动耦合特性开展数值模拟及分析。首先,通过对分布式动力翼各部件进行合理拆解,结合超椭圆方程、四阶Bezier曲线、CST (Class Function/Shape Function Tran...以分布式混合电推进飞行器技术研究为背景,针对分布式动力翼在前飞状态下动力/气动耦合特性开展数值模拟及分析。首先,通过对分布式动力翼各部件进行合理拆解,结合超椭圆方程、四阶Bezier曲线、CST (Class Function/Shape Function Transformation)参数化方法等构建了分布式动力翼复杂对象的参数化模型。然后,依次对动力翼二维剖面翼型、动力翼单元翼段、分布式动力翼整体动力/气动耦合特性进行了数值研究,并与常规翼型-机翼进行了对比分析。最后,梳理了分布式动力翼内外流耦合与其二维-单元-整体特性之间的内在联系,提出了关于分布式动力翼动力/气动耦合设计思路的建议。展开更多
针对串联混电飞机,首先在给定任务需求的飞行剖面内,结合动力学特性对整机的飞行性能进行分析,将总体设计参数与各飞行段的功率能耗需求相关联,进而开展各部分组件和全机的设计选型;然后对串联混电系统中的计算逻辑和各条工作路径进行...针对串联混电飞机,首先在给定任务需求的飞行剖面内,结合动力学特性对整机的飞行性能进行分析,将总体设计参数与各飞行段的功率能耗需求相关联,进而开展各部分组件和全机的设计选型;然后对串联混电系统中的计算逻辑和各条工作路径进行梳理和总结,讨论分析能源管理策略对方案设计的潜在影响。基于搭建的设计系统,首先针对Dornier Do 228NG飞机构型,从3个设计方面,将该方法与国外两个团队各自开发的设计方法进行对比分析,结果表明,对设计点评估的相对误差均在1.5%以内,对传统动力方案设计的各项相对误差在6%以内,而串联混电方案设计中最大起飞质量的相对误差在4%以内,验证了本文方法的可行性和有效性。其次,分析讨论了4种能源管理策略的特点和优劣势,并基于一款国外现有的串联混电飞机Panthera Hybrid,研究了不同策略下的动力系统工作特征和各项设计参数差异。其中,Light策略下的飞机起飞总质量最小,收益来源主要是起飞阶段的最大需求功率由燃油和电池动力系统同时承担,直接优化了动力系统的总质量。展开更多
文摘Reducing greenhouse gases, saving energy resources and mass optimization require technological changes towards increasingly electric vehicles. At the same time, performance improvement of semiconductor and dielectric materials further promotes electronic components confinement, resulting in a significant increase of embedded power densities. In the particular case of future hybrid propulsion aircrafts, electrical power that intended to supply reactors would be converted through power electronics components mounted on power busbars and insulated by solid dielectrics materials. These dielectrics materials have to respond to various electrical constraints of use (HVDC), in spite of environment change of aircraft parameters such as low pressure, temperature and thermal cycles, humidity... Unfortunately, partial discharges phenomenon is the most problem within electrical insulation system (EIS). Based on a topological model of power busbars designed for power converters dedicated to hybrid aircraft, partial discharge studies were conducted by simulation in various charging conditions of a PTFE insulator. Simulation results, which focus on electric field thresholds criteria of partial discharge inception voltage in air, reveal a net sensitivity of a space charge accumulation and distribution on dielectrics behaviour even for low space charge density, depending on their location in dielectrics. Compared to the behaviour observed with implanted homocharges, when by increasing homocharges density from 0.5 C/m3 to 2 C/m3 we observe a decrease of electric field by 450%, simulation results show a highest risk of partial discharge inception when heterocharges are accumulated inside dielectrics. Their accumulation increases the electric field in triple points beyond electric field thresholds of partial discharge inception in air. The simulated electric field reaching 22 kV/mm with only 2 C/m3 of heterocharges density accumulated in dielectric/busbars interfaces.
文摘以分布式混合电推进飞行器技术研究为背景,针对分布式动力翼在前飞状态下动力/气动耦合特性开展数值模拟及分析。首先,通过对分布式动力翼各部件进行合理拆解,结合超椭圆方程、四阶Bezier曲线、CST (Class Function/Shape Function Transformation)参数化方法等构建了分布式动力翼复杂对象的参数化模型。然后,依次对动力翼二维剖面翼型、动力翼单元翼段、分布式动力翼整体动力/气动耦合特性进行了数值研究,并与常规翼型-机翼进行了对比分析。最后,梳理了分布式动力翼内外流耦合与其二维-单元-整体特性之间的内在联系,提出了关于分布式动力翼动力/气动耦合设计思路的建议。
文摘针对串联混电飞机,首先在给定任务需求的飞行剖面内,结合动力学特性对整机的飞行性能进行分析,将总体设计参数与各飞行段的功率能耗需求相关联,进而开展各部分组件和全机的设计选型;然后对串联混电系统中的计算逻辑和各条工作路径进行梳理和总结,讨论分析能源管理策略对方案设计的潜在影响。基于搭建的设计系统,首先针对Dornier Do 228NG飞机构型,从3个设计方面,将该方法与国外两个团队各自开发的设计方法进行对比分析,结果表明,对设计点评估的相对误差均在1.5%以内,对传统动力方案设计的各项相对误差在6%以内,而串联混电方案设计中最大起飞质量的相对误差在4%以内,验证了本文方法的可行性和有效性。其次,分析讨论了4种能源管理策略的特点和优劣势,并基于一款国外现有的串联混电飞机Panthera Hybrid,研究了不同策略下的动力系统工作特征和各项设计参数差异。其中,Light策略下的飞机起飞总质量最小,收益来源主要是起飞阶段的最大需求功率由燃油和电池动力系统同时承担,直接优化了动力系统的总质量。
