等离子体附身:未来飞机将插上“隐形的翅膀”

N7J7

等离子机翼有着结构简单、无机械部件、响应速度快等优点,比传统的机翼舵面更轻便和高效。来自曼彻斯特城市大学(Manchester Metropolitan University)和格拉斯哥大学(University of Glasgow)的研究者们在这方面上取得了新的进展,让该技术离走出实验室、装备到大型飞机上更近一步。
等离子体与飞行器有什么关系?
出于对等离子隐身技术的探索,美国和俄罗斯军方在等离子与飞行器的研究已有数十年的历史,并在本世纪初将研究专向了其它空气动力方面的应用。中国首个等离子体动力学国家级重点实验室在2011年成立,专注于使用等离子改进飞行器发动机设计,但研究内容也包括减阻增升,提高战机的失速攻角和机动性。各国非军方机构也陆续将等离子体作动器(plasma actuator)技术应用在小型无人机上:
2009年,德国达姆施塔特工业大学的无人机首次将等离子体作动器用于控制边界层气流分离。
2010年,斯坦福大学学生首次实现用等离子体作动器代替舵面。
2014年,中国南京航空航天大学的“紫电”无人机获得10万元奖金。
等离子机翼好在哪里?
Dr. Rasool Erfani向媒体介绍道,等离子体机翼是最近10年才出现明显进步的新技术,前景光明。这种机翼有着等离子体作动器,使用的是单介质阻挡放电(single dielectric barrier discharge, SDBD)技术。绝缘的机翼表面上下方布置上位置不同的电极,电极之间的高压交流电将在空气中生成不断运动着的低温等离子。启用时,翼面上方覆盖上一层散发着紫色光芒的电离场,带动临近空气分子的移动。此时,飞机像是有了一双持续扇动着的隐形翅膀,产生看不见的微风,改善了空气动力结构。
相比普通机翼,在同样攻角和速度的情况下,施加了等离子体激励的机翼上方的气流将被加速,导致压强减小、升力增加。让飞行器能以更低的速度与更短的距离起飞与着陆。这种机翼省去了活动的机械部件,能将电能直接转化为动能。是压电作动器、零质量射流和涡流发生器之外,又一种理想的主动流动控制(active flow control)技术。
这样的作动器通过改变电流强度来控制升力大小,达到代替液压舵面、控制飞行姿态的目的。可以安装在机翼上的不同部位。安装在机翼尾部时则起出众的整流作用,大大减少乱流带来的阻力。美国的一家公司正在计划把等离子体作动器安装在货车车厢尾部,声称能将油耗降低12%。
将来的等离子飞机是什么样的?
Dr. Erfani等人使用的是一种新型的等离子体,叫做标准大气压均匀辉光放电等离子体</a>(OAUGDP)。这种技术可用于大面积的机翼,能改变阻力大小和调节推力方向。在常温常压下使用,并且噪音和功耗极低。在小型无人机上只需要消耗几瓦的能量。很快他们就能在更大的飞行器和更高的速度上进行测试。
等离子体作动器十分轻薄。按照需求,装置厚度可从几微米到几厘米不等,可应用到现有的机翼上,提升飞机的机动性和燃油效率。传统飞机机翼上的舵面需要沉重的机械进行操控。这份累赘在轻量化的新型飞机上被彻底去掉后,带来的效率提升会更加明显。在机翼前缘的等离子装置还能改善超音速飞行。待等离子推进技术成熟之后,未来的飞机或许会像法国工程师与无人机专家Jean-Louis Naudin设计的那样,使用覆盖机身的等离子层提供升力与推力,以至于不需要化石燃料,完全代替喷气式发动机。

https://www.theengineer.co.uk/waiting-in-the-wings-how-plasma-could-help-revolutionise-aircraft-design/

Waiting in the wings: How plasma could help revolutionise aircraft design

Last year, researchers from Manchester Metropolitan University and the University of Glasgow released details of a new system that uses electrically charged plasma in place of mechanical flaps on aircraft.

When the plasma is switched on, an electrical current passes through electrodes to generate an ionised field along the wing, known as the single dielectric barrier discharge (SDBD) plasma actuator. This field acts in a similar way to hydraulic flaps, increasing lift and drag and allowing planes to fly at lower speeds without stalling.

A typical SDBD plasma actuator system consists of two electrodes separated by a dielectric layer, typically Kapton, glass, quartz or ceramics. When activated, a purplish glow is emitted and spreads out across the dielectric surface.

According to its creators, the technology has the potential to be cheaper, lighter and greener than traditional flaps. Although the plasma wings are currently only suitable for smaller aircraft such as UAVs (Unmanned Aerial Vehicles), it is hoped that further development could make the technology viable on larger planes.

The Engineer caught up with lead researcher Dr Rasool Erfani, from Manchester Met’s School of Engineering to find out more about the research and its potential applications in the future.

Where did the idea for the plasma wings originate?

In the past 10 years single dielectric barrier discharge (SDBD) actuators have shown remarkable promise for various flow control applications. The benefit of converting electrical energy into kinetic energy without the need for any moving parts, having near instantaneous response, consuming relatively low power, and a wide range of operational frequencies have made these devices an attractive alternative to other active flow control methods such as piezoelectric actuators, synthetic jets, and vortex generators.

A new kind of surface plasma called OAUGDP was introduced by Roth et al. Their investigations showed the ability of the new configuration of plasma actuator in changing drag and varying the thrust direction of flat panels and re-attachment of flow in a NACA 0015 aerofoil. Furthermore, the actuator can be operated at atmospheric pressures and does not require a sophisticated power supply.

However, to date, they have only been used at micro air vehicle Reynolds numbers (e.g. on small unmanned aircraft). Their benefits have not been fully utilised on large scales since the effectiveness of plasma actuators is limited by the maximum induced velocity they can achieve.

Are the dimensions of the device similar to current pneumatic flaps?

The dimension of the plasma actuator depends on the material and configuration of the electrodes and their thickness is in a range of micrometres to centimetres. So they are really thin and can be retrofitted on different surfaces.

How do you project plasma reliability to stack up against current flap technology?

Currently they are strong enough to be used on MAVs and UAVs. They show their effectiveness on the boundary layer manipulation, film cooling and delaying separation on turbine blades and aerofoils, and the transition point manipulation, control separation on stationary and oscillating aerofoils leading to reduced noise levels. Considering the fact that it is only recently that people are working on this, the future of glowing plasma wings is promising.

How much cheaper and more efficient might the plasma actuator prove to be?

They are cheap in power consumption which is in a range of couple of watts. Again, it is under subject of my research to optimise their efficiency in terms of electrical power consumption and their mechanical power production. The new configuration of DBDs which uses multiple encapsulated electrodes (MEE) has been shown to produce a superior and more desirable performance over the standard actuator design.

Also, through development and employment of this innovative flow control mechanisms the need for heavy and bulky devices along the wing would be eliminated, leading to lighter aircraft and the lower consumption of fuel and hence, lower emissions.


Comments are closed.



无觅相关文章插件