Aircraft Clean Air Requirements Using Bleed Air Systems

There are certification and airworthiness requirements relevant to the provision of clean breathing air in the crew and passenger compartments. There have been continuing reports and studies over the years regarding oil fumes in aircraft, including impaired crew performance. Oil fumes are viewed in varying ways ranging from rare seal bearing failures, to low level leakage in normal flight. A Masters of Science (MSc) research degree was undertaken to assess whether there is any gap between the certification requirements for the provision of clean air in crew and passenger compartments, and the theoretical and practical implementation of the requirements using the bleed air system. A comprehensive literature search reviewed applicable certification standards, documented and theoretical understanding of oil leakage. Two types of interviews were conducted to address the research questions. Key aviation regulators were questioned about the process by which they certify and ensure compliance with the clean air requirements. Aerospace engineers and sealing professionals were interviewed about their understanding of how oil may leak past compressor oil bearing seals, and into the air supply under various flight conditions. The outcome of the research showed that there is a gap between the clean air certification requirements, and the theoretical and practical implementation of the requirements using the bleed air system. Low level oil leakage into the aircraft cabin in normal flight operations is a function of the design of the engine lubricating system and bleed air systems, both utilising pressurised air. The use of the bleed air system to supply the regulatory required air quality standards is not being met or being enforced as required.

TA-6发动机的引气特性

在TA-6发动机的压气机出口处引气,得到了发动机转速不变条件件下压气机增压比、引气阀压力损失系数、引气管内气流总压和引气气流温度与引气量之间的关系。研究表明,相对引气量在9～22％范围内变化时,TA-6发动机流量几乎不变,压气机增压比变化仅5％,引气压力为1.27×10~2～2.45×10~5Pa,引气温度约473K。所得结果可为燃气涡轮装置引气设计提供参考。

Using morphological analysis to tackle uncertainty at the design phase for a safety critical application

The gas turbine engine internal air system provides cooling and sealing air to a series of critical subsystems and components such as high pressure gas turbine blades,as well as controlling the thrust load on the turbine and compressor spool assembly.Many potential variations for the internal air system are possible,depending on the requirement,expertise and command of intellectual property.Some subsystems,such as rim seals,pre-swirl systems,and rotating cavities have been the subject of extensive development and analysis leading to robust design solutions.Nevertheless there remains scope for further consideration of the overall system design,and this paper explores the use of a decision analysis tool called morphological analysis applied to the internal air system.Morphological analysis provides an effective means for tackling issues where there is uncertainty,as is the case with many design scenarios,including the internal air system,with some specific parameters and information not available until later in the design phase,after the key geometry has been defined.The problem space comprising seven principal parameters,and a cross consistency matrix which allows identification of compatible and incompatible states are presented.