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The Potential of Hydrogen as Fuel for Aircraft
Published in G. Daniel Brewer, Hydrogen Aircraft Technology, 2017
The high specific heat of LH2, combined with its low temperature, permits the fuel to be used as a heat sink so that engine and vehicle hot parts can be cooled effectively and efficiently. For example, the high pressure turbine section in current modern, high-performance aircraft engines is conventionally cooled with air bled from the compressor. In addition to the fact bleed-air cooling has a very limited capability compared to hydrogen, the system has two disadvantages: (1) it requires the compressor to do more work than would otherwise be necessary, and (2) the air used to cool the vanes and stators of the turbine is discharged into the turbine working fluid, causing some disruption of flow and consequent loss in efficiency.
Fire and overheat protection
Published in David Wyatt, Mike Tooley, Aircraft Electrical and Electronic Systems, 2018
The fire protection technologies used on aircraft depend on these areas and specified fire risk. In addition to the fire risk in these areas, high temperatures resulting from engine bleed air leaks can also be hazardous. Bleed air is tapped from the compressor stage of a gas turbine engine, distributed in the pneumatic system for a number of purposes including thermal anti-icing. The consequences of hot air leaks are less severe than fire, but overheats can weaken structure and damage components. The pneumatic system takes air from the engines and distributes it throughout the aircraft; typical areas that are fitted with dedicated overheat detection systems are the wing leading edges, in the wheel wells and under the cabin floor.
Preliminary safety assessment of circular variable nacelle inlet concepts for aero engines in civil aviation
Published in Stein Haugen, Anne Barros, Coen van Gulijk, Trond Kongsvik, Jan Erik Vinnem, Safety and Reliability – Safe Societies in a Changing World, 2018
S. Kazula, D. Grasselt, M. Mischke, K. Höschler
An anti-icing system is installed in the inlet to ensure this. Most commonly, electrical or bleed air anti ice systems are used (Rolls-Royce Plc 2015). Bleed air anti ice systems transfer hot air from the compressor to the inlet lip to prevent icing. Aluminium is typically used for the inlet lip, due to its good heat conductivity. Furthermore, aluminium is light and resilient to foreign object damage, sand erosion, hail and bird strikes. It is to prove during certification that thrust can be maintained to a certain level to assure that the flight can be safely continued after a single bird strike (Hedayati & Sadighi 2016).
Simultaneous inboard and outboard, inflight measurements of ultrafine particle concentrations
Published in Aerosol Science and Technology, 2021
Paul I. Williams, Jamie Trembath
Early work on cabin air quality (CAQ) found that the predominant source of particles was from passengers in the years before the smoking ban on aircraft (for example, Dechow, Sohn, and Steinhanses 1997). More recent work on CAQ has been driven either by a need to understand the effects of particulates on an aircraft’s Environmental Control System (ECS; Cao et al. 2017, 2018) or concerns about aircrew health during so-called fume events (Winder, Fonteyn, and Balouet 2002). During flight, to compensate for the reduced pressure, compressed outside air is fed via the bleed air system to the cabin (see Cao et al. 2017 and reference therein), and concerns have been raised as to whether engine exhaust products, hydraulic fluids, and/or lubrication oil (present either as oil or a decomposed by-product) can contaminate the cabin air via the bleed air supply, causing a fume event (Howard et al. 2018).
Impact of stressors in the aviation environment on xenobiotic dosimetry in humans: physiologically based prediction of the effect of barometric pressure or altitude
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Maintaining the health and well-being of men and women who execute the mission of the military is a critical aspect of our Armed Forces’ readiness strategy. The special characteristics of the military aviation operational environment and their combined impact on aircrews constitute a challenge to the health risk assessment strategies used to identify situations where risk management action is needed (Gray et al. 2019; Nicol et al. 2019). Aircraft has been noted to be a “physiologically challenged environment” due to hypobaria, acceleration, low humidity, thermal variation, vibration, and other factors (Butler et al. 2018). Standard health risks from volatile organic compounds (VOCs) are generally interpreted at ambient environmental conditions. Therefore, traditionally derived occupational exposure limits (OELs) and other guidance values may not be adequate in such settings (Sweeney et al. 2020). During aircraft operation, pilots may breathe either cabin air or, in a high-performance environment, oxygen-enriched air. In either case, the breathing air is derived from bleed air from engine compressors (Duran et al. 2019). Under routine operations, total VOCs including 2-hexanone, methylene chloride, methyl ethyl ketone, propene, ethanol, 2-propenal, acetone, isopropyl alcohol, methyl isobutyl ketone, and toluene may briefly spike after the engine is started but remain below OELs and then decline (Duran et al. 2019). However, spills and leaks may result in cabin and cockpit contamination by aviation-related compounds at elevated levels (Solbu et al. 2011).