Перспективы воздухоплавания: дирижабли будущего - часть 2

Аэромеханика дирижабля

Рассматриваются вопросы аэродинамики и динамики полета дирижабля. Расчеты аэродинамических воздействий на дирижабль проводятся методами вычислительной аэродинамики. Исследованы аэродинамические характеристики дирижабля с учетом влияния экрана, а... //  www.labirint.ru

 

big.jpg @ img2.labirint.ru [кеш]

Рассматриваются вопросы аэродинамики и динамики полета дирижабля. Расчеты аэродинамических воздействий на дирижабль проводятся методами вычислительной аэродинамики. Исследованы аэродинамические характеристики дирижабля с учетом влияния экрана, а также влияния винтовых движителей, аэродинамические характеристики в установившемся потоке с поперечным сдвигом вблизи экрана и при движении через области атмосферной неоднородности струйного типа, аэродинамические силы и моменты инерционной природы, действующие на дирижабль. Представлены общие пространственные математические модели движения, модели продольного и бокового движений дирижабля, математические модели установившихся движений. Рассмотрены вопросы анализа возмущенных движений, устойчивости и управляемости дирижабля. Представлены результаты решения задач динамики дирижабля, притягиваемого тросом к земле. Большая часть вопросов аэродинамики и динамики полета дирижабля, рассмотренных в монографии, представлены в научной литературе впервые.

 

Burney_Cross_section.JPG @ www.airshipsonline.com [кеш]

"My New Dirigible on Pontoons" by Sir Charles Dennistoun Burney the designer of the R-101. Sir Charles gives details on his new design for a Dirigible that could land on the water. Lots of graphics, and photos of:

New Dirigible Design

 

British Zeppelin Burney Dirigible w/Pontoons 1930 pictorial AIRSHIPS | eBay

"My New Dirigible on Pontoons" by Sir Charles Dennistoun Burney the designer of the R-101. Sir Charles gives details on his new design for a Dirigible that could land on the water. Lots of graphics, and photos of. //  www.ebay.com

 

s-l1600.jpg @ i.ebayimg.com [кеш]

s-l1600.jpg @ i.ebayimg.com [кеш]

Fundamentals of Aircraft and Airship Design, Volume 2 - Airship Design and Case Studies examines a modern conceptual design of both airships and hybrids and features nine behind-the-scenes case studies. It will benefit graduate and upper-level undergraduate students as well as practicing engineers. The authors address the conceptual design phase comprehensively, for both civil and military airships, from initial consideration of user needs, material selection, and structural arrangement to the decision to iterate the design one more time. The book is the only available source of design instruction on single-lobe airships, multiple-lobe hybrid airships, and balloon configurations; on solar- and gasoline-powered airship systems, human-powered aircraft, and no-power aircraft; and on estimates of airship/ hybrid aerodynamics, performance, propeller selection, S&C, and empty weight. The book features numerous examples, including designs for airships, hybrid airships, and a high-altitude balloon; nine case studies, including SR-71, X-35B, B-777, HondaJet, Hybrid Airship, Daedalus, Cessna 172, T-46A, and hang gliders; and full-color photographs of many airships and aircraft.

 

However, notice that there is a region of operation between land and air
that is uniquely filled in by airships and in particular hybrid airships. Even
though buoyant vehicles are very efficient, adding buoyancy does not always
result in a reasonable design. As a result, airplane designers, recognizing
that a buoyant lifting gas offers efficiencies far beyond those of winged aircraft, have many failed attempts to integrate a lifting gas into an airplane.
Why is this design road littered with failures such as in the examples of
Fig. 1.13? The problem is that most "would be" designers fail to recognize
that adding volume for buoyant lifting gases creates drag more rapidly than
it creates lift until at least 50% of the lift force is generated by buoyancy.
Most of the failed designs in Fig. 1.13 tried to add a modest amount of
volume for a lifting gas to increase lift but it was at the expense of weight and
drag. This is a losing proposition for modest volumes filled with a lifting gas.

 

Airships will provide excellent cost vs performance. However, airships
are only a realistic option when speed is relatively unimportant or not
important at all. Mission scenarios requiring long duration are best satis
fied by a buoyant vehicle such as an airship. Several studies over the last
decade have shown that hybrid airships show significant benefits when
delivering perishable payloads or operations involving austere sites .. Other
studies have also shown cost benefits for operations to and from mining
sites such as in northern Canada. Cost will be discussed in more detail in
Chapter 11, where it is shown that development costs for an airship program
are about 10% of an equivalent aircraft development program.

 

The airship has two possible cruise strategies. The first cruise strategy
is at constant CL that makes LaerolD a constant over the mission. Because
airships usually cruise at a constant altitude the speed must decrease as fuel
is burned to keep CL constant. The CL is usually selected to fly at maximum
LaeroiD = 1/[4(CD0)(J()]>i, which is also a minimum drag flight.
If we assume CL, rJp, and BSFC constant over the weight change (fuel
burned), Eq. (4.14b) can be integrated to give an exact solution for cruise
strategy #1
Range (nmt.1 es) = ------ 3261Jp Laero 0 r.n [ — WH0 ]
BSFC D WH
1
(4.15)
Equation (4.14a) can also be numerically integrated as follows:
Range= Lforums.airbase.ru/post.php?action=post&tid=60756V/(BSFCx Power)J(WHi+I - WHi) (4.16)
for i = 0 to n increments where V and Power ~e the average speed and
power over the weight increment. The quantity V/(BSFCx Power) is called
the range parameter or range factor.
8JfJ Cruise Strategy #2
The second cruise strategy is to fly at constant speed. For this strategy the
CL must decrease as fuel is burned to fly at constant altitude (constant q).
Returning to Eq. (4.14a) and substituting (cDo +KCL2 )qvot2/3 for the
drag term and c Lacro = wHIq Vof2/3 gives Laero
. f 17p dWH
Range(nmtles) = 326
BSFC 213 [( wA )[/url]
q Vol ' CDo + J( q2 Vof4/9
(4.17)
Equation (4.17) can be integrated from the initial WHo to the final W H1
for constant speed (q), BSFC, and rJp to give an exact solution for the cruise
strategy #2 range.
Range
= ~:F~ k [tan-{qVol::fi]-tan-1 [ qVo;:~ ]] {4.18)


The range for the two cruise strategies is compared on Fig. 4.5 using the
data of Sample Problem 4.1. For a given amount of fuel (WH 0 / WH,) constant
Cr flight [Eq. (4.15)] always gives an increased range over constant speed
strategy [Eq. (4.18)] but takes longer because the speed decreases. The cruise
strategy employed will depend upon the user requirements ... maximum
range or minimmn time. It is important to remember that for constant CL
cruise Eq. (4.15) must be used and for constant speed cruise Eq. (4.18) must
be used.
AJJI Cruise Strategy #3
Taking notice of Fig. 4.5 it might make sense to fly a combined cruise
strategy: start the mission at a high value of WH(/ WH, with a constant CL
cruise, then at a specified speed switch to a constant speed cruise for the
remainder of the flight. This combined strategy would yield more range than
a constant speed for the entire cruise distance and less cruise duration than
for a constant Cr for the entire cruise distance. The CargoStar exan1ple in
Sample Problem 6.1 will demonstrate this combined cruise strategy.