标题: Fortune, June 16, 2014 (II) [打印本页] 作者: choi 时间: 6-10-2014 11:49 标题: Fortune, June 16, 2014 (II) Shawn Tully, How United Technologies Became a Top Gun. The ultra-profitable giant has made a bundle outfitting skyscrapers in China. Now it’s shaking up the world of aviation.
fortune.com/2014/06/02/fortune-500-united-technologies/
(a) Quote:
(i) “United Technologies [through its Otis division] had $4.8 billion in saLES IN cHINA LAST YEAR, PROVIDING EKLEVATORS AND HVAC [heating, ventilation, and air conditioning] systems for the gleaming new skyscrapers popping up in each Chinese megacity.
(ii) “If you’re not an aerospace engineer, the details of how the [Pratt and Whitney PW1100G] Geared Turbofan [GTF] engine works will make your head spin. But here is a short version: The GTF is the first engine specifically designed to use gears that makes it such a breakthrough. In conventional jet engines a single ‘direct drive’ shaft runs from the fan you see in the front to the turbine that turns the fan. The turbine gets its power from fuel that is mixed with compressed air, then ignited in the combustion chamber to create a controlled explosion of expanding gas. The fan and turbine are directly connected. Hence, they both rotate at exactly the same speed.
“But there’s a problem with that arrangement. The fan is more efficient turning at a far slower pace, especially when it’s larger. And the turbine operates best at higher speeds. The reason is that a bigger fan, at slower rotation, raises the engine’s crucial “bypass ratio” by greatly increasing the volume of air that swooshes around the outside of the engine. That bypass air is what gives the plane 90% of its ‘thrust,’ or propulsive power. Pratt’s innovation is to place a gearbox between the fan and turbine. The gearbox allows the fan to turn at one-third the speed of the turbine. The result is a much quieter, more fuel-efficient engine, which jetmakers are clamoring to buy.
(iii) “There was still plenty of skepticism in the industry about Pratt’s new technology. * * * CFM, the GE consortium, is not sitting idly by. It has developed its own advanced engine, the CFM LEAP [GTF’s major competitor], that delivers fuel savings and noise reduction on the scale of the GTF and competes for orders on the A320neo. The LEAP technology is different: It doesn’t use gears but compresses oxygen at far higher pressure so that less fuel is needed to generate the same thrust, running the engine at much higher temperatures.
(b) My comment:
(i) There is no need to read the rest. The report is kind of an advertisement for United Technologies.
(ii) “That bypass air is what gives the plane 90% of its ‘thrust,’ or propulsive power.” Now I comprehend the mechanics of jet engine. The thrust does not, in most part, come from internal combustion--but from the bypass.
(iii) aircraft engine starting
en.wikipedia.org/wiki/Aircraft_engine_starting
(auxiliary power unit (APU))