請問引擎震動(Engine surge) 的起因?
請問飛機引擎震動(Engine surge) 的起因是什麼?
- MasonLv 71 decade agoFavorite Answer
Surge and stall are closely related phenomena and apply to compressors. In simple terms:
An axial compressor generates a flow and pressure increase down the engine. It achieves this through the flow of air over successive rows of rotor blades and stator vanes. Both the blades and the vanes are similar to aircraft wing airfoils. If the flow separates over the airfoils badly the airfoil can be said to stall.
Once stalled, the airfoil looses the ability to pump gas down the engine. There is then nothing to prevent the high pressure gas at the rear of the engine from flowing forwards to the lower pressure stages. This reverse flow is called a surge. It lasts for 10-50 milliseconds.
What causes stalls? Strong cross-flows into the engine inlet during 'unusual' aircraft manouvres, bird injestion, maybe a few others.
Stalling (breakaway of airflow from the convex side of the compressor blade, just behind the leading edge) can also be caused by improper angle position of fixed blades, or more usually by a transient condition during run-up to full compressor load. The surge phenomenon, as gwolf explains, is a momentary flowback from high-pressure (aft end) to low-pressure (forward end) lasting only a few milliseconds, disappearing and returning some milliseconds later, creating a vibration which puts extreme load on blades and shaft. Surge during transient conditions can be avoided by modifying inlet guide vane angle, compressor blow-off valves set to open to atmosphere above a certain pressure, or even (as North American Sabre pilots did during the Korean war) cutting off the fuel flow for a split second allowing the compressor to 'jump' from one speed/pressure characteristic curve to another.
以上為原文照貼，主要的內容在說，噴射引擎靠大量的氣流吸進引擎內部燃燒產生推力，若有氣流不平順經過引擎葉片時有如飛機的仰角過大，氣流與機翼面產生分離造成STALL(失速)，ENGINE SURGE 又稱COMPRESSEROR STALL，所以只要氣流不順，都有可能造成ENGINE SURGE，照講噴射引擎的氣流是無間斷的，只有氣流大小的區別，如果氣流不順造成間斷後方的高增壓氣體免不了會往前方壓力小的部份噴，造成巨大聲響與瞬間動力喪失，持續時間通常極短，但是若不加以處置會一直持續"胖！胖！胖！胖！"作響，激烈的震動會造成引擎受損，不可不慎。