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中国战机矢量喷管技术 '弃俄投美'

发表于 11-3-2018 12:45:45 | 显示全部楼层 |阅读模式
本帖最后由 choi 于 11-3-2018 12:47 编辑

刘新宇, 中国战机矢量喷管技术 '弃俄投美.' RFA, Nov 2, 2018.
https://www.rfa.org/mandarin/yat ... 11022018084025.html


"2018第十二届中国国际航空航天博览会将从11月6日到11日在珠海举行。 * * * 据中国军事网站引述消息人士报道,在今年的珠海航展上,俄罗斯将不会派飞行表演队参加,而且此前一直在珠海航展上非常吸引眼球的展示了惊人高机动性的俄罗斯苏-35战斗机也不会前来 * * *

"从2017年就一直被军迷们关注的歼-10B将换装矢量控制发动机的消息近日被一张杂志图片证实。但令人惊讶的是,从外观上就可以明显看出来,歼-10B上安装的矢量发动机的喷口并不是俄罗斯苏-30和苏-35等俄罗斯战机发动机上的喷口,而是同美军战斗机矢量发动机类似。  俄美矢量发动机喷口从外观上差别很大,也代表了不同的发展理念。俄罗斯的可动喷管特别长,而歼-10B新安装的这款喷口非常短。中方这种“弃俄投美”的技术发展可谓非常明智。因为俄制矢量发动机可旋转部位非常长,结构笨重,不但会带来很大的重量和阻力负担,而且使用寿命也会大大缩短。美式设计的短喷口才是王道,结构简单、重量轻、寿命长、容易换装。  不过,也有评论指出,只模仿外观并不代表已经获得了关键技术和整套先进设计理念。

(a) The report us based entirely on the nozzles (of American, Russian and Chinese fighter jets), specifically the outer appearance of the nozzles. As the report says, the Chinese nozzle is based entirely on a magazine photo (see (d) below), because China has not unviled J-10B to the public yet.
(b) thrust vectoring
(section 4        List of vectored thrust aircraft: section 4.1 For VTOL ability,
section 4.2 For higher maneuverability -- Vectoring in two dimensions: Lockheed Martin F-22 Raptor (pitch and roll only) + Vectoring in three dimensions: Chengdu J-20 (experimental), Sukhoi Su-35S and Sukhoi Su-57 (Sukhoil's int4ernal name is T-50) )

Quote (introduction):

For "ballistic missiles that fly outside the atmosphere, aerodynamic control surfaces are ineffective [for lack of air in space] * * * For aircraft, the method was originally envisaged to provide upward vertical thrust as a means to give aircraft vertical (VTOL) or short (STOL) takeoff and landing ability. Subsequently, it was realized that using vectored thrust in combat situations enabled aircraft to perform various maneuvers not available to conventional-engined planes. To perform turns, aircraft that use no thrust vectoring must rely on aerodynamic control surfaces only, such as ailerons"

On this Wiki page: Take notice
(i) that F-35 does not use thrust vectoring.
(ii) of the first photo (in this Wiki page) whose caption is "3D thrust vectoring nozzle on a Sukhoi Su-35S" (Su-35S officially entered service in Russia in 2014, and in China in "April 2018." en.wikipedia.org for "su-35")

(c) The preceding item -- (b)(ii) -- shows the nozzle with a back view. (Note the smooth rim of the nozzle.)

Ike, Su-35S Ready for Production. Robotpig.net, May 16, 2011
https://robotpig.net/aerospace-n ... or-production-_2063
displayed an illustration (not photo) of the pair of nozzles viewed from the top. Note its length (ie, it is long compared with nozzles of American jet fighters).

Incidentally, the twin-engine SU-35S is equipped with Saturn AL-41F1S engine.

(i) Mike Yeo, China May Be Making Its Fighters More Stealthy. Defense News, Apr 4, 2018
https://www.defensenews.com/glob ... ters-more-stealthy/
("A photo has emerged of China's J-10 fighter fitted with what is believed to be a thrust vectoring nozzle with stealthy features.  The photo, published by an unknown Chinese-language defense magazine, shows a Chengdu J-10C fighter flying with a modified exhaust nozzle for its indigenous Shenyang-Liming WS-10 Taihang turbofan engine.  The modifications to the aircraft, which is one of a small number of J-10s being used by the Chengdu Aerospace Corporation as flying testbeds, include sawtooth edges on the exhaust nozzles similar to that used by other low-observable aircraft to improve their rear aspect stealth characteristics.  The aircraft also has part of the bottom of its brake parachute housing, located on the base of its vertical fin, removed. This would allow its thrust vectoring nozzle to be rotated upwards and would allow thrust vectoring to be applied on both the vertical and horizontal planes")

Defense News calls it J-10C.
(ii) 于宝辰, 美媒关注中国矢量喷管技术,将让歼20更隐身. 观察者网, Apr 6, 2018
("美国《防务新闻》网站4月4日报道称,一张出现在中国 '不知名杂志'(其实是 '三大知识' 中的《航空知识》[2018年第5期 --5月刊)上的照片展示了安装在 '歼10C战斗机'(其实照片上就标着歼-10B)上的矢量喷管,带有明显的隐形设计。  这张出现在《航空知识》上的照片是一篇文章的配图,标题为《中国矢量喷管突然现身》")

(e) The (d)(i) mentioned "sawtooth edges on the exhaust nozzles."
(i) "The sawtooth edges around the nozzle are similar to those used by other stealth aircraft like the F-35 and F-22. Russia's Sukhoi Su-30/35 Flanker series of fighters also utilize the same edges."  from the Web.
(A) NASA invented it to lower noise. See Ji, Banke, NASA Helps Create a More Silent Night/ NASA, Dec 13, 2010 (last updated on Aug 7, 2017)
https://www.nasa.gov/topics/aero ... chevron_events.html
("One of the most recent noise-reducing technologies shepherded through the research process by NASA and now making a difference on commercial jet engines is chevrons.  Chevrons are the sawtooth pattern seen on the trailing edges of some jet engine nozzles. As hot air from the engine core mixes with cooler air blowing through the engine fan, the shaped edges serve to smooth the mixing, which reduces turbulence that creates noise. * * * The new Boeing 787 is among the most modern jets relying on chevrons to reduce engine noise levels. It sports chevrons on the nacelles, or fan housings. The Boeing 747-8 has chevrons on both the nacelles and inner core engine nozzles")
(B) However, the sawtooth edges also reduce "radar cross section" (RCS) when radar emits electromagnetic radiation from the back of the jet fighter, See How to Become Stealthy. F-22 Raptor, undated (in the section "Gallery: Get Stealthy")
(section 2.1 Echo scattering)
(iii) Fpr the problem with Russian design of vectoring nozzle, see Is T-50 as stealthy as F-22 Raptor?
(an illustration in Nadia Nongzai's answer on Nov 26, 2017 + Abhirup Sengupta's answer on Nov 27, 2016: "those 3D thrust vectoring nozzles at back severely increases it's RCS [radar cross section]. It also has comparatively much higher IR (Infrared) signature. The PAK FA can be quite easily detected from sides & rear aspect by any advanced 4th gen. aircraft")

(f) bonuses:
(i) Jeff Scott, Axisymmetric & Thrust Vectoring Nozzles.
("The vast majority of jet-powered aircraft have used what are known as axisymmetric nozles [sic; should be nozzles]. These nozzles, like those illustrated below, direct thrust purely along the axis of the engine, hence the name axisymmetric. * * * This type of nozzle is at the heart of what is known as thrust vectoring. The nozzles depicted above are capable of vectoring the thrust up or down * * * I suppose a nozzle that deflected thrust left or right would also be considered a 2D nozzle, so long as it was not capable of deflecting up and down as well. However, I've never heard of any aircraft employing such a nozzle, which could be used to improve maneuverability in yaw. A nozzle capable of deflecting both up and down as well as right and left is a 3D nozzle.  To date, only a handful of aircraft have made use of 2D or 3D thrust vectoring nozzles * * * Only research aircraft are known to have tested 3D nozzle technology so far")
(ii) Advantages of Square over Circular Engine Nozzle?  The F-22 has square nozzles, while the Russian Sukhoi PAK FA has circular nozzles. There are both 5th generation planes, but with different nozzles, why?
https://aviation.stackexchange.c ... cular-engine-nozzle
("Circular nozzles have these advantages: They can be swiveled in any direction, so both pitch and yaw moments can be produced. Square nozzles only allow to create pitch forces, because their panels can only be moved around one axis * * * Actually, square thrust vectoring nozzles have just one advantage: They can be made to reflect radar waves in a few well-defined directions, while round nozzles will scatter them all around. This makes square nozzles the preferred choice for stealth aircraft, regardless of thrust vectoring")
(III) How Do Stealth Aircraft Reduce the Heat Signature?
https://aviation.stackexchange.c ... -the-heat-signature


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