复合翼eVTOL电池需求及对动力总成安全性的影响

Compound wing eVTOL battery requirements and implications for powertrain safety

关键词:  复合翼eVTOL  电池  全电动力总成  故障树分析  安全性

Key words:  Compound wing eVTOL  Battery  All electric powertrain  Fault tree analysis  Safety

摘要:

动力电池是电动化飞行得以实现的重要组成部分，其技术层次和安全水准对电动垂直起降飞行器（Electric Vertical Take off and Landing aircraft，eVTOL）的商业化推广尤为重要。本文在典型飞行任务下，研究电池性能对eVTOL飞行器的运营性能、适航性能和安全性能的影响。利用开源软件SUAVE（Stanford University Aerospace Vehicle Environment，SUAVE）对复合翼eVTOL进行了整机与动力总成的建模，利用故障树分析（Fault Tree analysis，FTA）方法对动力总成进行了安全性分析。通过仿真，发现在现有电池技术水平下，电池的放电倍率约束是决定电池性能需求的关键限制条件，针对本文设计的eVTOL，372 Wh/kg是满足所有安全约束的最低能量密度，在使用过程中电池容量的衰退是设计者选择电池能量密度的重要参考指标。单独改善电池的可靠性对动力总成可靠性的提升是有限的，但电池性能的衰退将使电池成为动力总成失效的主要因素。通过FTA发现本文搭建的典型动力总成失效率为1.524×10^-7，接近SC-VTOL-01中单座飞行器的基础级灾难性故障率要求。

Abstract:

Power battery is an important component for the realization of electrified flight， its technology level and safety level are particularly important for the commercialization of electric vertical take-off and landing aircraft （eVTOL）. In this paper， the impact of battery performance on the operational performance， airworthiness and safety of eVTOL aircraft was investigated under typical flight missions. The whole aircraft and powertrain of the compound wing eVTOL were modeled using software SUAVE （Stanford University Aerospace Vehicle Environment， SUAVE）， and the safety analysis of the powertrain was conducted using the Fault Tree analysis （FTA） method. Through simulation， it is found that under the current battery technology level， the discharge C-rate constraint of the battery is the key limiting condition that determines the battery performance demand. For the eVTOL designed in this paper， 372 Wh/kg is the minimum energy density to satisfy all the safety constraints， and the degradation of the battery capacity during use is an important reference index for the designer to select the minimum energy density of the battery. Improving the reliability of the battery alone will have a limited effect on the powertrain reliability， but the decline of the battery performance will make the battery the main factor of the powertrain failure. The typical powertrain failure rate built in this paper is found to be 1.524×10^-7 by FTA method， which is close to the base-level catastrophic failure rate requirement for single-seat vehicles in SC-VTOL-01.