Wings with improved aerodynamic characteristics.
Scurtu, Dan ; Ciobanu, Bogdan
1. INTRODUCTION
The paper aims at establishing, in a theoretical and experimental
manner, the influence of a q controlled debit jet on its aerodynamic
features. The jet is launched through the trailing edge of the lift
wing.
The issue was already approached at a theoretical level at the half
of the 20th century. (Davidson I.M. 1956) theoretically studies the
jet-flaps lift wing. In 1955, Kadasch M. sets a theoretical form of a
complex function that describes the fluid movement around a fluid
emission lift wing through the trailing edge. (Malavard L. 1956) sets a
linear form of functions for the disturbing potential determined by the
jet. (Nagy A.B. 1969) extends the theory Kutta-Jukovsky to jet air
foils. (Roy M. 1956) sets an expression for the disturbing potential
generated by the jet from the trailing edge. (Dumitrescu L. 1957 and
Patraulea N. 1961) theoretically set the effect of fluid emission on the
lift force. All this research aimed at the plane wing and became less
effective along with the development of engines used in aviation
engines.
In the context of present energy deficit, we believe it is useful
to continue the research applying to the singular wing and the network
working wing that applies to axial aeraulic generators.
2. GENERAL CONSIDERATIONS
The lift wing put in a real current fluid generates a lift force
[F.sub.L] = [rho]/2 x b x c x [C.sub.L] x [W.sup.2.sub.[infinity]] and a
drag force [F.sub.D] = [rho]/2 x b x c x [C.sub.D] x
[W.sup.2.sub.[infinity]] in which: [rho]--the density of the fluid
current moving around the wing, [C.sub.L]--lift coefficient, CD--the
draft coefficient, [W.sub.[infinity]] is the speed of the general
current, b the span and c the air foil cord. In practical applications,
the lift force [F.sub.L] must be as big as possible, and the drag force
[F.sub.D], as small as possible.
In order to achieve this, the lift coefficient values [C.sub.L]
must be as big as possible and the values of the drag coefficient [C.sub.D] must be as small as possible.
The paper has in view a physical method that allows the increase of
the lift coefficient, at the same time with the decrease of the drag
coefficient.
The method consists of the creation of a controlled emission of
fluid in the trailing edge of an aerodynamic air foil.
The fluid emission is assimilated to an equally distributed source
on the span, figure 1.
[FIGURE 1 OMITTED]
3. MATHEMATICAL MODELLING OF THE MOVEMENT
The study of fluid flow around the solid bodies is based on the
theory of potential movements and the use of the custom transformation
theory.
The general movement of the fluid around the circle of custom
transformation with fluid jet is described by the global complex
potential function:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1)
The lift theoretical coefficient CLT is given by the relation:
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (2)
The theoretical modelling of the flow was made in the following
conditions:
--The chosen aerodynamic air foil is type Go593.
--The values of the incidence angle [alpha] [deg] = -6[degrees],
-1[degrees], 2[degrees], 4[degrees], 6[degrees], 8[degrees],
10[degrees], 12[degrees], 14[degrees], 16[degrees].
--The q debit [[m.sup.3]/s] of the jet [q.sub.0] = 0; [q.sub.1] =
0.001; [q.sub.2] = 0.002; [q.sub.3] = 0.003; [q.sub.4] = 0.004;
[q.sub.5] = 0.005; [q.sub.6] = 0.006.
--[q.sub.0] = 0 stands for the classic aerodynamic air foil (no jet
in the trailing edge).
--The speed of the general current [W.sub.[infinity]] = 20 [m/s];
cord c = 0.1 [m]; span b = 0.5 [m].
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
Figure 3 present the lift and drag coefficients for Go593 airfoil,
without fluid emission, as given in catalogues.
In figure 4, the variations of the theoretical coefficient
[C.sub.L] are presented for all the values of q, taking into
consideration all the values of the incidence angle [alpha].
4. THE EXPERIMENTAL STUDY OF THE PHENOMENA
We aimed at assessing the lift coefficient [C.sub.L] and the drag
coefficient [C.sub.D] for a controlled fluid jet lift wing emitted by
the trailing edge, as compared to the classic wing in the same
conditions as in theoretical modelling.
The tests were performed on an open circuit aerodynamic tunnel,
with continuous speed adjustment in the working chamber and a turbulence degree of 0.006; the aerodynamic balance used for measurements is made
up of type FUTEK FBB350 force transducers.
The results of experimental determinations referring to the
[C.sub.L] lift coefficient and the drag coefficient [C.sub.D] are shown
in figures 5 and 6.
5. CONCLUSIONS ON EXPERIMENTAL DETERMINATIONS
--The increase of the lift coefficient depends on the q debit jet
evacuated through the trailing edge.
--The values of lift coefficient for the wing with jets emitted
through the trailing edge are bigger than those for the classic wing up
to 40%.
--The increase of the lift coefficient for the jet wing is
determined by circulation [??] growth.
--The values of drag coefficient for the fluid jet wing are smaller
than the values determined for the classic wing.
--For values of the incidence angle a from 0[degrees] to
14[degrees], the drag coefficient values are negative. In this area of
incidence angles, the lift wing incidence shows a propulsive character.
[FIGURE 5 OMITTED]
[FIGURE 6 OMITTED]
The look forward of presented studies refers at:
--Theoretical and experimental studies about flow in laminar layer.
--Establish of a method to draw an air foil for an imposed pressure
(velocity) distribution.
--Experimental studies of an air foils network with fluid emission
through trailing edge.
6. REFERENCES
Davidson, I.M. (1956). The Jet-Flap, Journal of the Royal
Aerodynamic Society, London
Dumitrescu, L. (1957). Determinarea efectului de ejectie la
profilele cu volet fluid (Determination of emission effect for airfoils
with fluid volet), Revista studii si Cercetari de Mecanica aplicata, tom
VIII
Kadasch, M. (1955). Theorie des profiles avec soufflage au bord de
fuitte (Theory of airfoils with fluid emission through trailing edge),
Bul. De la Soc. Francaise des Mecaniciens, nr. 18
Malavard, L. (1956). Sur une theorie lineare du soufflage au bord
de fuitte d'un profile d'aille (About a lineare theory of
emission through the trailing edge of an airfoil), Comptes Rendus nr.
242, Paris
Nagy, A.B. (1969). Asupra teoriei Kutta-Jukowski la profilele cu
jet (About Kutta-Jukowski theory of airfoils with jet), Studii
matematice, Ed. Acad. Romane
Patraulea, N. (1961). Aripi cu jet in bordul de fuga (Wings with
jets through trailing edge), Studii si cercetari de mecanica aplicata
nr. 5
Roy, M. (1956). Theorie d'un profil d'aille a jet (Theory
of a jet-wing), Comptes Rendus nr. 244, Paris