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人类第一台真空能发动机即将在中国攻关成功 (转载)
[版面:北京航空航天大学][首篇作者:Communipig] , 2011年05月15日00:52:50 ,597次阅读,1次回复
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发信人: Communipig (共产猪), 信区: BUAA
标  题: 人类第一台真空能发动机即将在中国攻关成功 (转载)
发信站: BBS 未名空间站 (Sun May 15 00:52:51 2011, 美东)

【 以下文字转载自 Military 讨论区 】
发信人: wayofflying (小破熊), 信区: Military
标  题: 人类第一台真空能发动机即将在中国攻关成功
发信站: BBS 未名空间站 (Sat May 14 22:28:25 2011, 美东)

高歌,现任北京航空航天大学能源动力学院动力工程及工程热物理学科一级责任教授,
航空发动机气动热力国防重点实验室副主任,长期从事动力工程、工程热物理及流体力
学领域的教学与科研工作,并在基础科研和多学科的应用技术领域取得了一系列国际领
先水平的创新性科研成果。

他在1984年发明的"沙丘驻涡火焰稳定器",获国家发明一等奖,钱学森同志称之为"一
项长中国人志气的重要发明"。该成果广泛应用于我国多种军用航空发动机中,取得了
数以亿元计的经济效益,至今仍保有先进水平。本刊记者于今年10月采访了高歌教授,
了解到了他近期从事的一些前沿科研工作的最新进展,尤其是他对龙卷风的研究及其工
程应用价值,让人耳目一新。

  高歌教授在采访中提到,传统的航空发动机技术虽然还在不停地改进提高之中,但
受到原理和材料工艺上的限制,已经逐渐逼近了性能发展的极限。目前虽然涌现出一些
新型航空发动机技术,但仍然没有走出依靠压力膨胀过程来实现热功转换的思路。他强
调,人们应该另辟蹊径,寻找其他可用的工作原理。为此,他研究了自然界龙卷风的形
成与强化机制,发明了一项称为"余热增推"的技术,直接利用龙卷旋涡实现热功转换并
提取能量,用以提高航空发动机的推力和工作效率,这是具有独创性的重大科研成果,
是人们未曾涉足过的一片新天地。


  传统航空发动机技术需要新的突破高歌首先提到,航空发动机经历了两个大的历史
阶段,第一阶段就是在1950年以前,主要是活塞发动机的使用。第二阶段在二次世界大
战以后,涡轮发动机迅猛发展,一直占据着霸主地位,它有很多的变种,如涡扇发动机
、涡桨发动机、涡轴发动机等,但其核心技术都是压气机-涡轮组合,即燃气轮机。


  很早就有人提出,涡轮发动机过了巅峰期以后有没有后续机种。为什么会提出这个
问题呢?因为人类所发明的热机到目前为止,绝大多数都是依靠压力膨胀过程来实现热
功转换的,活塞发动机、涡轮发动机都是如此。而要提高涡轮发动机的性能主要有两条
途径,一个是提高压比,另一个是提高涡轮前温度,这是它的工作原理决定的。但提高
压比、提高涡轮前温度是有一定限制的,设想压比达到40左右,压气机的转速会很大;
同时压比提高,叶片的强度也成问题。所以无论从压比还是从温度来说,涡轮发动机基
本上快要接近其性能极限了。


  当然,所有发动机在其发展的历程中,性能都有从低到高的发展过程。但如果原理
上不出现重大变化的话,就不会有本质的改变。如涡轮发动机压气机本身的效率,四十
年前是81%~82%,而今天,最好的压气机的效率是86%~87%。可以看出,大约每十年只
提高1%多一点。人们不得不考虑未来航空发动机的出路问题。


  脉冲爆震发动机和旋转冲压发动机航空涡轮发动机目前出现了很多新的机种,如脉
冲爆震发动机、冲压发动机等,这是主要的几个研究方向,也是试图找到大幅提高航空
发动机性能的技术尝试。但这些发动机还处于摸索阶段,高歌一一对其技术难点和缺陷
进行了分析。


  高歌提到,脉冲爆震发动机噪声巨大,工作频率跟不上去。工作频率就是指爆震燃
烧频率,要100赫兹左右才能够产生足够的比冲,如果到不了这个频率,比冲不够,与
涡轮机相比就没有竞争力。设想在一个空腔里面,排气、进气一秒钟来回一百多次,而
且还没有一个活塞把气体推出去,只靠自己的膨胀过程来填充、爆炸,再填充、再爆炸
,这本身是非常困难的。


  冲压发动机不能解决零速启动、低速情况下的低效率等问题。高歌向记者介绍到,
最近国内外都在进行旋转冲压发动机的研究,旋转冲压发动机就是想克服直流式冲压发
动机不能零速起飞的缺点。旋转冲压发动机内部有一个转子,启动时首先用电力驱动,
或是由其它起动机让转子高速旋转,气流进入转子后再发生冲波,产生高压,利用转子
本身的旋转制造一个超声速或者跨声速的入流,在旋转场里提高马赫数,最后达到冲压
的效果。美国一台一百千瓦级的旋转冲压发动机已经试运转成功了。


  但旋转冲压发动机运用到航空发动机上有很大的难度,首先要解决发动机直径问题
,飞机不可能安装直径太大的发动机。另外,转子旋转以后燃烧系统如何配置,高超声
速气流进来如何变成没有旋转,研制出来以后能不能在效率、尺寸、推重比等方面和现
有的涡轮发动机竞争,这都有待未来发展才能得出定论。本来冲压发动机就是一个空筒
子,现在有一个转子在发动机里面旋转,解决了低速启动的问题,但飞到高速以后,气
流冲进来遇到了转子这样一个大障碍物,如何解决,还面临一系列的问题。高歌认为旋
转冲压发动机的前途将取决于一系列关键技术能否得到妥善解决。


  脉冲爆震发动机、冲压发动机等这些新技术,依然没有摆脱传统的热机工作原理,
只是改进而已,真正的突破还要在其他方向上寻找。


  有关龙卷风原理在航空发动机上的应用,高歌谈到:航空发动机最近显示了一些很
有前途的研究方向,就是有没有可能不利用压力膨胀过程来实现热功转换,而以往所有
热机都是压力膨胀实现热功转换的。他把研究方向瞄向了自然界的龙卷风。龙卷风不是
利用压力过程而是利用旋涡,依靠龙卷风式的特殊旋涡的旋转把热能变成机械能。高歌
带领的研究人员已经在这方面做了大量试验和应用研究。


  高歌指出,龙卷风的旋转能量来源对于研究大气流体力学的人来说,他们肯定可以
明白无误地说,这是龙卷风外围的热气流的热能提供的旋转能量,但有一些教条的人会
说,"热力学上没有这一说法,热能变成机械能必须要有压力膨胀过程!"实际上龙卷风
在旋转过程中遵守着流体力学的一个定理,称为克罗科(Crocco)定理。这个定理通俗
地讲,就是在一个旋涡的外围,如果外边热里边冷,就产生了一个沿半径方向内指的焓
梯度,或是温度梯度,这个焓梯度越大,旋风的旋转强度就越大。如果在龙卷风外围有
热量加入的话,龙卷风就会得以强化。


  高歌利用龙卷风的原理开发了一项"余热增推"技术,在不改变核心机的前提下可以
轻而易举地获取发动机推力的增加,增推效果相当可观。这项原理和技术是高歌首创的
,并且在航空发动机上得到了验证,有重大的实用价值。通过"余热增推"技术,可以直
接利用龙卷旋涡将热能转换为旋转动能,进而提高发动机的推力和推重比、降低单位推
力的耗油率。龙卷风组合燃烧技术也可极大地改善燃烧性能,使燃烧效率从85%提高到
97.5%,阻力、贫富油、稳定性等性能指标也达到国际领先水平。可以断言,龙卷风原
理开辟了热机发展一个值得探索的新方向。


  克罗科定理在20世纪初就有了,是一个纯粹的理论工具,人们没有找到其工程技术
运用的途径。高歌首先在试验中发现龙卷风能够把热能变成机械能,然后想到了能利用
它来增加发动机推力,最后才找到了克罗科定理。并不是克罗科定理指导其开发出有关
技术,而是高歌做出来以后为了找理论解释才想到了克罗科定理。


  高歌强调,中国人应增强自信心,我们有能力在科技领域自主创新。"沙丘驻涡"技
术为我国的航空发动机技术做出了贡献,而这项"余热增推"技术比"沙丘驻涡"的价值要
大得多。


  物质观的改变和真空能发动机高歌还将研究方向扩展到高能物理方面。他说,21世
纪伊始,就传出了一些和20世纪科学观有着重大突变性质的观点,一个是物质观的改变
,另外一个就是关于真空概念的改变。所谓物质观的改变,就是宇宙的物质构成是4.4%
的显物质,95.6%的暗物质、暗能量。暗物质、暗能量是什么,怎么提取它、利用它,
将成为21世纪科技具有划时代变革意义的一个标志。如果能够提取和利用暗物质、暗能
量,人类的科学技术和文明就要进入一个崭新的新***。


  有关真空概念,过去的课本上都说真空是什么也没有,现在真空观发生了重大变化
,认为"真空是物质的凝聚态"(李政道语),真空是能量海,蕴藏着极大的能量。有人
说1立方厘米真空里面含有1095克的能量,通过质能互换定理(E=MC2),可以把真空中
的能量看成无穷大。


  高歌进一步解释到,暗能量充斥于远离星系的宇宙深空之中,具有单纯磁性斥力而
导致宇宙加速膨胀;在地球周围真空中则凝聚着暗物质,具有单纯吸力。暗物质粒子的
尺度和电子相同,可以自由穿透显物质实体,实际上人们都"浸泡"在这样一个暗物质的
海洋里,因为各个地方的密度都一样,就不易感觉到它的存在。如何才能"感觉"到它呢
?就是在容器中用旋涡或者是电磁、冷核聚变等方法,把一个局部空间变成真空,即所
谓的显物质真空,这样暗物质的浓度就要进一步地提高,与有显物质的外围就不一样了
。暗物质有了密度梯度以后,它就会对显物质发生作用,真空对显物质的作用称为"界
变"。


  "界变"和物质的"相变"是完全不同的,和"质变"也有区别,真空就是一个界变点,
物质和真空相互作用会发生能量形态和物理属性上的突变。可以说,真空的重大作用就
是使物质能够发生界变,而界变能够使正熵过程变成负熵过程,正物质变成反物质。真
空中的暗物质具有吸聚作用,可增强旋涡的旋转,这就是旋涡真空能动力系统的基础原
理。"真空能"在国外称为"Zero Point Energy"。以这个理论为指导,应用在工程上,
例如:磁流体真空能系统能够制造出反重力系统,而真空能技术也可与航空涡轮发动机
组合起来。


  高歌认为,以上两种观念的改变要引起人类科技的一个天翻地覆的变化,对航空发
动机而言,今后一个确凿无疑的发展方向,第一步就是发展涡轮和真空能组合发动机。
这是一种混合式动力系统,是一种真空能发动机的初级应用形式,但对于现有的航空发
动机技术已经是高级形式了,它将是现有航空涡轮发动机的后续机种。2001年在英国伦
敦召开了一次场推进会议,有个美国专家提出来,20世纪是核能世纪,21世纪是真空能
世纪。还有人认为,5年之内有可能造出真空能发动机。高歌在真空能发动机方面也做
了大量的研究,证明了真空能的存在和提取的可能性,也证实了在航空发动机上应用的
可能性。


  第二步就是制造纯粹的真空能发动机。真空能发动机既包括水平动力式,也包括垂
直动力式。垂直动力的单极磁流体真空能发动机就是做成一个圆盘形,它具有几十吨到
上百吨的提升力,可以使飞行器悬浮在空中,也能高速升降。这种发动机在今后的几十
年内一定能够造出来,高歌希望能亲自参与我国真空能发动机的研制工作,并亲眼看到
它实用化的到来.高歌还称,中国一旦率先研发出真空能发动机,那么美国空军的战斗力
将在中国空军面前后退五十年。


  除了真空能发动机,下一代航空航天动力系统就是反质子发动机,研究的序幕已经
拉开。2003年7月,美国NASA把反质子发动机列为今后十年的三大绝密项目之一。反质
子发动机制成以后,将会为航空航天飞行器提供非常强劲的动力,因为它可实现全部的
质能互换。高歌说:"美国人能不能成功,我不做评论,美国人走的方向和技术细节我
们也不清楚。但我们也不必一天到晚跟着他们后面走,我们可以走出中国人自己的路。
以中国人的智慧,完全可以自主创新做出这些东西来。
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Wikipedia

Vacuum energyFrom Wikipedia, the free encyclopediaJump to: navigation,
search
This article needs attention from an expert on the subject. See the talk
page for details. WikiProject Physics or the Physics Portal may be able to
help recruit an expert. (November 2010)

Vacuum energy is an underlying background energy that exists in space even
when the space is devoid of matter (free space). The concept of vacuum
energy has been deduced from the concept of virtual particles, which is
itself derived from the energy-time uncertainty principle. The effects of
vacuum energy can be observed in various phenomena such as spontaneous
emission, the Casimir effect, the van der Waals bonds[citation needed] and
the Lamb shift, and are thought to influence the behavior of the Universe on
cosmological scales. Using the upper limit of the cosmological constant,
the vacuum energy in a cubic centimeter of free space has been estimated to
be 10−15 Joules.[1] However, in both Quantum Electrodynamics (QED) and
Stochastic Electrodynamics (SED), consistency with the principle of Lorentz
covariance and with the magnitude of the Planck Constant requires it to
have a much larger value of 10107 Joules per cubic centimeter.[2][3]

Contents [hide]
1 Origin
2 Implications
3 History
4 See also
5 External articles and references
6 Notes


[edit] OriginQuantum field theory states that all fundamental fields, such
as the electromagnetic field, must be quantized at each and every point in
space. A field in physics may be envisioned as if space were filled with
interconnected vibrating balls and springs, and the strength of the field
were like the displacement of a ball from its rest position. The theory
requires "vibrations" in, or more accurately changes in the strength of,
such a field to propagate as per the appropriate wave equation for the
particular field in question. The second quantization of quantum field
theory requires that each such ball-spring combination be quantized, that is
, that the strength of the field be quantized at each point in space.
Canonically, if the field at each point in space is a simple harmonic
oscillator, its quantization places a quantum harmonic oscillator at each
point. Excitations of the field correspond to the elementary particles of
particle physics. Thus, according to the theory, even the vacuum has a
vastly complex structure and all calculations of quantum field theory must
be made in relation to this model of the vacuum.

The theory considers vacuum to implicitly have the same properties as a
particle, such as spin or polarization in the case of light, energy, and so
on. According to the theory, most of these properties cancel out on average
leaving the vacuum empty in the literal sense of the word. One important
exception, however, is the vacuum energy or the vacuum expectation value of
the energy. The quantization of a simple harmonic oscillator requires the
lowest possible energy, or zero-point energy of such an oscillator to be:


Summing over all possible oscillators at all points in space gives an
infinite quantity. To remove this infinity, one may argue that only
differences in energy are physically measurable, much as the concept of
potential energy has been treated in classical mechanics for centuries. This
argument is the underpinning of the theory of renormalization. In all
practical calculations, this is how the infinity is handled.

Vacuum energy can also be thought of in terms of virtual particles (also
known as vacuum fluctuations) which are created and destroyed out of the
vacuum. These particles are always created out of the vacuum in particle-
antiparticle pairs, which shortly annihilate each other and disappear.
However, these particles and antiparticles may interact with others before
disappearing, a process which can be mapped using Feynman diagrams. Note
that this method of computing vacuum energy is mathematically equivalent to
having a quantum harmonic oscillator at each point and, therefore, suffers
the same renormalization problems.

Additional contributions to the vacuum energy come from spontaneous symmetry
breaking in quantum field theory.

[edit] ImplicationsVacuum energy has a number of consequences. In 1948,
Dutch physicists Hendrik B. G. Casimir and Dirk Polder predicted the
existence of a tiny attractive force between closely placed metal plates due
to resonances in the vacuum energy in the space between them. This is now
known as the Casimir effect and has since been extensively experimentally
verified. It is therefore believed that the vacuum energy is "real" in the
same sense that more familiar conceptual objects such as electrons, magnetic
fields, etc., are real. However, the Casimir effect is no certain proof for
Vacuum energy since it can also be explained without this theory.[4]

Other predictions are harder to verify. Vacuum fluctuations are always
created as particle/antiparticle pairs. The creation of these virtual
particles near the event horizon of a black hole has been hypothesized by
physicist Stephen Hawking to be a mechanism for the eventual "evaporation"
of black holes. The net energy of the Universe remains zero so long as the
particle pairs annihilate each other within Planck time. If one of the pair
is pulled into the black hole before this, then the other particle becomes "
real" and energy/mass is essentially radiated into space from the black hole
. This loss is cumulative and could result in the black hole's disappearance
over time. The time required is dependent on the mass of the black hole but
could be on the order of 10100 years for large solar-mass black holes.

The vacuum energy also has important consequences for physical cosmology.
Special relativity predicts that energy is equivalent to mass, and therefore
, if the vacuum energy is "really there", it should exert a gravitational
force. Essentially, a non-zero vacuum energy is expected to contribute to
the cosmological constant, which affects the expansion of the universe. In
the special case of vacuum energy, general relativity stipulates that the
gravitational field is proportional to ρ-3p (where ρ is the mass-energy
density, and p is the pressure). Quantum theory of the vacuum further
stipulates that the pressure of the zero-state vacuum energy is always
negative and equal to ρ. Thus, the total of ρ-3p becomes -2ρ: A negative
value. This calculation implies a repulsive gravitational field, giving rise
to expansion, if indeed the vacuum ground state has non-zero energy.
However, the vacuum energy is mathematically infinite without
renormalization, which is based on the assumption that we can only measure
energy in a relative sense, which is not true if we can observe it
indirectly via the cosmological constant.

The existence of vacuum energy is also sometimes used as theoretical
justification for the possibility of free energy machines. It has been
argued that due to the broken symmetry (in QED), free energy does not
violate conservation of energy, since the laws of thermodynamics only apply
to equilibrium systems. However, consensus amongst physicists is that this
is incorrect and that vacuum energy cannot be harnessed to generate free
energy.[5] In particular, the second law of thermodynamics is unaffected by
the existence of vacuum energy. Moreover, in Stochastic Electrodynamics, the
energy density is taken to be a classical random noise wave field which
consists of real electromagnetic waves propagating isotropically in all
directions. The energy in such a wave field would seem to be accessible e.g.
with nothing more complicated than a directional coupler. The most obvious
difficulty appears to be the spectral distribution of the energy, which
compatibility with Lorentz invariance requires to take the form Kf3, where K
is a constant and f denotes frequency.[6][7] It follows that the energy and
momentum flux in this wave field only becomes significant at extremely
short wavelengths where directional coupler technology is currently lacking.

[edit] HistoryIn 1934, Georges Lemaître used an unusual perfect-fluid
equation of state to interpret the cosmological constant as due to vacuum
energy. In 1948, the Casimir effect provided the first experimental
verification of the existence of vacuum energy. In 1957, Lee and Yang proved
the concepts of broken symmetry and parity violation, for which they won
the Nobel prize. In 1973, Edward Tryon proposed that the Universe may be a
large-scale quantum-mechanical vacuum fluctuation where positive mass-energy
is balanced by negative gravitational potential energy. During the 1980s,
there were many attempts to relate the fields that generate the vacuum
energy to specific fields that were predicted by Grand unification theory
and to use observations of the Universe to confirm that theory. However, the
exact nature of the particles or fields that generate vacuum energy, with a
density such as that required by inflation theory, remains a mystery.

[edit] See alsoCasimir effect
Cosmological constant
Dark energy
False vacuum
Heisenberg's Uncertainty principle
Lambdavacuum solution
Quantum electrodynamics
Stochastic electrodynamics
Vacuum state
Virtual particles
Zero-point energy
Zero-point field
Zero-energy Universe
[edit] External articles and referencesFree pdf copy of The Structured
Vacuum - thinking about nothing by Johann Rafelski and Berndt Muller (1985)
ISBN 3-87144-889-3.
Saunders, S., & Brown, H. R. (1991). The Philosophy of Vacuum. Oxford [
England]: Clarendon Press.
Poincaré Seminar, Duplantier, B., & Rivasseau, V. (2003). "Poincaré
Seminar 2002: vacuum energy-renormalization". Progress in mathematical
physics, v. 30. Basel: Birkhäuser Verlag.
Futamase & Yoshida Possible measurement of vacuum energy
YAN Kun (2006), Vacuum energy and superluminal velocity
G. Jordan Maclay, (et al.): Study of Vacuum Energy Physics for Breakthrough
Propulsion. 2004, NASA Glenn Technical Reports Server, (pdf, 57 pages,
Retrieved 2009-10-22)
[edit] Notes This article needs additional citations for verification.
Please help improve this article by adding reliable references. Unsourced
material may be challenged and removed. (November 2010)

1.^ Sean Carroll, Sr Research Associate - Physics, California Institute of
Technology, June 22, 2006C-SPAN broadcast of Cosmology at Yearly Kos Science
Panel, Part 1
2.^ Peter G. Millonni - "The Quantum Vacuum"
3.^ de la Pena and Cetto "The Quantum Dice: An Introduction to Stochastic
Electrodynamics"
4.^ R. L. Jaffe: The Casimir Effect and the Quantum Vacuum. In: Physical
Review D. Band 72, 2005 [1]
5.^ IEEE Trans. Ed., 1996, p.7
6.^ Peter G. Millonni - "The Quantum Vacuum"
7.^ de la Pena and Cetto "The Quantum Dice: An Introduction to Stochastic
Electrodynamics"
Retrieved from "http://en.wikipedia.org/wiki/Vacuum_energy"
Categories: Quantum field theory | Energy in physics
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