Method of driving a turbine in rotation by means of a jet device

A turbine device and a method of driving the turbine device are disclosed. The turbine device includes an admission channel, a turbine, and an injection channel. The turbine device may also include a regulator. The turbine is driven by injecting a primary fluid into the admission channel at a given velocity and simultaneously causing a secondary fluid to flow into the admission channel at a lower velocity. The primary fluid and the secondary fluid form a mixture in the admission channel, which flows toward the turbine. The velocity of the mixture is less than that of the primary fluid, while the mass flow of the mixture is approximately equal to the sum of the mass flows of the primary and secondary fluids. The regulator compares the rotational speed of the turbine to a target speed and regulates parameters associated with the turbine device if the rotational speed of the turbine and the target speed differ by more than a predetermined amount.

The present invention relates to a method of driving a turbine in rotation 
and to a corresponding turbine device. 
Turbines have been known for a long time and are essentially constituted by 
a hub bearing blades, driven in rotation by a fluid (gas, liquid) passing 
therethrough. 
In known manner, drive of a turbine by a fluid makes it possible to 
transfer the energy of the fluid to the rotation shaft of the turbine. For 
example, rotation of this shaft serves to drive an alternator to produce 
electric current, or to drive various tools (drilling, sawing , . . . ). 
Up to the present time, the problems of the known devices reside in high 
flow velocities necessary for obtaining the highest powers possible. 
However, such high flow velocities lead to considerable disturbances; for 
example, when the fluid is a gas, there is creation: 
of shock waves, 
of expansion or compression beams appearing on the various components of 
the device. 
The consequences of such disturbances are, inter alia, that: 
the components of these devices must present particular, precise, optimum 
shapes (which involves a limited, and even very limited domain of use), 
said components must mechanically withstand the efforts induced by the 
vibratory phenomena accompanying these disturbances, 
said disturbances create acoustic phenomena which are often very violent. 
Another aspect limiting the use of the prior turbine devices resides in the 
high, even very high speeds of rotation of these devices. 
It is an object of the present invention to overcome all these drawbacks 
and in particular to create a turbine of which the nominal working point 
is not associated with a transonic flow velocity in order to avoid all the 
problems associated with the disturbances induced by such a flow. 
It will be recalled that a working point is characterized by a torque of 
value (speed of rotation, power) or (speed of rotation, torque). In the 
present description, nominal working point will mean a working point 
corresponding to a maximum power. Nominal torque working point will mean 
the working point corresponding to a maximum torque. 
One of the purposes of the invention is to obtain powers comparable to 
those obtained on conventional turbines, but with flow velocities 
compatible with flows which are not or only slightly disturbed. 
To that end, the present invention concerns a method of driving a turbine 
in rotation, said turbine being connected to an upstream fluid admission 
channel and to a downstream ejection channel, said process being 
characterized in that it consists in: 
injecting a primary fluid in the fluid admission channel, said primary 
fluid presenting a determined pressure Pp, velocity Vp and mass flow dmp, 
simultaneously admitting a secondary fluid in the fluid admission channel, 
this fluid presenting a pressure ps and a velocity vs less than those of 
the primary fluid, and a mass flow Dms, 
mixing the primary and secondary fluids in the admission channel and 
directing the mixture of the fluids towards the turbine, this mixture 
presenting a mass flow equal to the sum of the mass flows of the primary 
and secondary fluids (dmp+Dms), 
driving the turbine in rotation by the passage of the mixture of fluid over 
blades of this turbine and 
ejecting the mixture of fluid by means of the fluid ejection channel. 
Advantageously, the method according to the invention is a method of 
driving a turbine in rotation at a variable reference speed of rotation 
and consists in addition in: 
continuously measuring a magnitude representative of the real speed of 
rotation of the turbine, 
comparing this real speed of rotation with the reference speed of rotation, 
continuously modifying one or more parameters of the flow for the nominal 
working point of the turbine to correspond to the reference working point. 
Thus, the fact of injecting a primary fluid at pressure and velocity higher 
than the secondary fluid entrains the latter towards the turbine. This 
effect is known under the name of Venturi effect or jet pump effect. 
However, this effect is used in the present invention as energy 
transformer and speed reducer. In fact, the Venturi effect, in the present 
case, transforms the energy of the primary fluid injected via a nozzle 
with low mass flow and high velocity and pressure, into the energy of a 
fluid (resulting from the mixture of said primary fluid with the secondary 
fluid sucked by Venturi effect), characterized by a high mass flow and a 
low flow velocity. 
Now, in known manner, the power available on the rotation shaft of the 
turbine is: P=C. .omega. . where C is the torque delivered and .omega. the 
speed of rotation of the turbine. The torque is expressed by: C=F.d where 
F is the overall radial force resulting from the flow of the fluid in 
inter-blade channels of the turbine and where d is the distance from the 
point of application of this force to the shaft of the turbine. 
Moreover, if it is question of a gaseous flow, in first approximation, the 
force F is expressed by the following formula: 
EQU F=Dmm (We sin (.beta.e)-Ws sin (.beta.s)) 
where 
Dmm is the mass flow of the fluid traversing the turbine (i.e. of the 
mixture of fluid), 
.beta.e is the leading angle of the blades of the turbine, 
.beta.s is the trailing edge angle of the blades of the turbine, 
We is the module of the relative velocity (reference rotating with the 
turbine) of admission of the fluid in the turbine, 
Ws is the module of the relative outlet velocity of the fluid in the 
turbine. 
For a given nominal working point, therefore characterized by a given power 
and speed of rotation (.omega.), a torque (C), and therefore a force (F), 
is sought. This force F is obtained by producing a high mass flow Dmm 
equal to the sum of the mass flows dmp+Dms whilst having fluid flow 
velocities We and Ws sufficiently low to be compatible with a slightly 
disturbed flow. 
In addition, the method according to the invention makes it possible, by 
continuously acting on the pressure and/or the velocity of the primary 
fluid and/or on any other dimensional or functional parameter of the 
turbine device, to be able to adapt the nominal working point of the 
device to the reference working point. 
The real speed of rotation is continuously measured then compared with a 
reference speed of rotation. This reference speed of rotation is 
determined for a given application. For example, if the turbine drives a 
milling tool, this speed may be of 36000 rpm. 
Further to this comparison, one or more dimensional or functional 
parameters are continuously modified so that the speed of rotation 
measured is equal to the reference speed of rotation. 
Advantageously, in order to modify the dimensional parameters, the 
secondary fluid admission, primary fluid injection and fluid ejection 
channel outlet sections are continuously modified so as to render equal, 
as much as possible, the reference working point and the nominal working 
point. 
Advantageously, in order to modify the functional parameters, in addition 
to the variation in pressure of the primary fluid, the injection of the 
primary fluid may be effected along a helicoidal path inducing a 
self-limitation and self-adaptation of the working conditions of the 
turbine. Such a mode of injection is called helicoidal. 
Similarly, the injection of the primary fluid is advantageously effected in 
zones close to the walls of said admission channel. Such a mode of 
injection is called peripheral. 
The present invention also relates to a turbine device employing the method 
described hereinabove, said device comprising, within a body presenting 
overall a symmetry of revolution, an upstream fluid admission channel, a 
turbine and a downstream fluid ejection channel, said device being 
characterized in that it further comprises: 
means for injecting a primary fluid in the fluid admission channel, said 
primary fluid presenting determined pressure, velocity and mass flow, 
means for admitting a secondary fluid in the fluid admission channel, this 
secondary fluid presenting pressure and velocity less than those of the 
primary fluid and a mass flow, 
means for mixing the primary and secondary fluids adapted to give the mixed 
fluids a mass flow equal to the sum of the mass flows of the primary and 
secondary fluids and to direct this mixture towards the turbine and thus 
drive this turbine in rotation. 
The device is advantageously adapted to drive a turbine in rotation at a 
variable reference speed and comprises to that end control and regulation 
means (50) comprising: 
means for measuring a magnitude representative of the speed of rotation of 
the turbine, 
means for acquiring the measured speed of rotation, 
processing means adapted to compare the measured speed of rotation with a 
reference speed of rotation, 
actuators adapted to regulate functional and/or dimensional parameters of 
the flow to cause the measured value of the speed of rotation to coincide 
with the reference value of this speed, and 
a stop valve. 
Thanks to such arrangements, a nominal working point of the turbine is 
obtained for a high torque and a low speed of rotation compared to that 
obtained without using such arrangements on a comparable turbine. 
The device according to the invention is advantageously provided with 
actuators adapted to vary the section of admission of the primary and 
secondary fluids, as well as the section of the ejection channel. The 
nominal working point of the turbine may thus be modified as desired and 
continuously adapted to the reference working point.

As already indicated, the purpose of the present invention is to drive a 
turbine in rotation, and this at a relatively low speed of rotation 
.omega., of the order of 0 to 60000 rpm, but with a high torque C. Thus, 
the product C..omega. which gives the power P of the turbine remains high, 
without the speed of rotation .omega. being so. 
To that end, the method according to the invention of driving the turbine 
is described hereinafter. 
The turbine being placed between an upstream fluid admission channel and a 
downstream ejection channel, the method according to the invention 
consists in: 
injecting a primary fluid in the upstream fluid admission channel. Such 
injection is effected at determined pressure Pp, velocity Vp and mass flow 
dmp, 
admitting a secondary fluid in the upstream admission channel. The pressure 
ps and velocity vs of this secondary fluid are less than those of the 
primary fluid. The mass flow of this secondary fluid is dms, 
mixing in the admission channel the primary and secondary fluids. The 
mixture thus obtained presents a velocity Vm and a pressure Pm higher than 
those of the secondary fluid, and less than those of the primary fluid. 
The mass flow Dmm of this mixture of fluid is equal to the sum of the mass 
flows dmp+Dms of the primary and secondary fluids, 
directing the mixture of fluids towards the turbine, 
driving the turbine in rotation by the passage of the mixture of fluid, and 
ejecting the mixture of fluid having traversed the turbine, towards the 
outside. 
Advantageously, the method makes it possible to drive a turbine in rotation 
in accordance with a variable reference parameter and consists, in 
addition, in: 
continuously measuring a parameter as a function of the speed of rotation 
of the turbine, 
comparing this measured speed of rotation with a reference speed. This 
measured speed of rotation is a function, inter alia, of the dimensional 
and functional parameters of the flow, 
continuously modifying one or more parameters of the flow in order to adapt 
the nominal working point of the turbine to the reference working point. 
Advantageously, a modification is made of the dimensional parameters of the 
turbine device (variation of the inlet section of the secondary fluid, of 
the injection section of the primary fluid and of the ejection section of 
the ejection channel). Consequently, the nominal working point of the 
turbine is modified and the real speed of rotation is continuously 
regulated so that it corresponds to the reference speed of rotation. 
The turbine device according to the invention is described hereinafter. 
According to the embodiment shown in FIGS. 1 and 2, the device 10 according 
to the invention essentially comprises (FIG. 2): 
an upstream fluid admission channel 11, 
a turbine 12, 
a downstream fluid ejection channel 13, 
injection means 14, and 
control and regulation means 50 (FIG. 1). These means 50 are constituted 
by: 
a stop valve 22, 
measuring means 19, 
acquisition means 20, and 
regulation means 52 comprising: 
processing means 21, and 
actuators 51. 
The means 14 (FIG. 1) for injection of primary fluid Fp in the admission 
channel 11 is placed in the upstream part 11a of the admission channel 11. 
This means 14 comprises a nozzle 15. 
A secondary fluid Fs is sucked in the upstream admission channel by the 
depression created by the injection of the primary fluid. Once in the 
upstream admission channel, these two fluids are mixed in the downstream 
part 11b of the admission channel 11. The length of this admission channel 
determines in part the characteristics of the mixture of the fluids. 
If necessary, a convergent channel 16 is placed upstream of the turbine 12 
and has for its purpose to accelerate the mixture of fluids. 
A deflector means 17, called upstream distributor, constituted by a fixed 
turbine wheel, is placed upstream of the turbine 12 in order to direct the 
mixture of fluids in optimum manner over blades 18 of the turbine 12. 
The turbine 12 is thus driven in rotation. 
The mixture of fluids is then ejected via the ejection channel 13 out of 
the turbine device. The purpose of such a channel is to adapt in 
particular the pressure of the fluid leaving the turbine to that of the 
fluid present around the ejection section. 
The rotation of the turbine is employed for any application, for example 
for driving tools, etc., as will be detailed with reference to FIG. 3. 
The turbine device is in addition associated with control and regulation 
means 50. These means 50 comprise: 
means 19 for measuring a magnitude representative of the speed of rotation 
of the turbine 12. These measuring means are constituted by two 
piezoelectric sensors (only one is shown in FIG. 1) measuring the static 
pressures upstream and downstream of the turbine in non-disturbed flow 
zones. The purpose of the presence of these two sensors is to multiply the 
points of measurement in order to compare their value and to activate, if 
necessary, a stop valve 22 installed on the primary fluid supply pipe. 
These means must be reliable and give repetitive and significant 
measurements. 
acquisition means 20 receiving and adapting the electrical magnitudes 
measured by means 19, 
processing means 21 adapted to define the instantaneous speed of rotation 
of the turbine (measured speed), and to compare this measured speed of 
rotation with a reference speed of rotation. If the measured and reference 
speeds differ, the processing means sends a command order, 
actuators 51 here constituted by a pressure regulator receiving the command 
order from the processing means and adapted to modify the pressure of 
injection of the primary fluid and to render the measured and reference 
speeds of rotation equal, and 
a safety stop valve 22 placed upstream of the primary fluid injection 
device in order to stop functioning of the device if necessary. This stop 
valve is also controlled by the processing means 21. 
In this way, the device according to the invention is continuously 
regulated by the control and regulation assembly 50. 
In a variant of this device, the convergent channel 16 may be integrated in 
the upstream distributor 17. 
As shown in FIGS. 3 and 4, the injection means 14 may take different 
shapes. 
In the examples shown in FIGS. 3 and 4, the means corresponding to those 
described in FIG. 2 are referenced as in FIG. 2, but increased by a unit 
of one hundred. 
FIGS. 3 and 4 present a first variant of the device according to the 
invention. 
The injection means 114 are constituted by two conduits 130 opening in the 
lateral wall of the upstream admission channel 111. Advantageously, these 
conduits are inclined by an angle .varies. (FIG. 3) determined with 
respect to axis A of the device, and an angle .beta. (FIG. 4) between the 
axis of the conduit 130 and a diametral plane F passing through the axis 
of the turbine and the centre of the injection section at the level of the 
wall of the channel 111. 
Thus, the primary fluid Fp entrains the secondary fluid Fs in a helicoidal 
path (helicoidal injection) along the walls (peripheral injection) of the 
upstream admission channel 111. This type of injection is called 
peripheral-helicoidal injection. 
This mode of injection presents the advantage of being self-adapting. In 
fact, when the speed of rotation of the turbine increases, the mass flow 
Dms of the secondary fluid also increases. The speed of the secondary 
fluid in the plane of injection of the primary fluid in the admission 
channel, has a modulus which increases and a direction which tends to 
approach the turbine shaft. Consequently, the flow of the mixture presents 
a general incidence which decreases in the admission plane of the turbine. 
Consequently, the available power tends to decrease if the increase off 
the secondary mass flow is not taken into account and vice versa if the 
speed of rotation of the turbine decreases. This then results in a turbine 
device of which the free rotation conditions (i.e. without resistant 
torque generated by the outside medium on the shaft of the turbine) are 
self-limited, and which present a high power peak for a low speed of 
rotation, characterizing the phenomenon of self-adaptation of the flow. 
By way of example, the speed of rotation corresponding to such a power peak 
is 12000 rpm for a turbine with a diameter of 30 mm and a primary fluid 
supply of peripheral-helicoidal type with three admission ways equally 
distributed along the circumference of the admission channel (angles 
.varies. and .beta. of inclination of the admission conduits being 
45.degree.). 
It should be noted that the number of primary fluid injection conduits 130 
may vary. For a better homogeneity of the primary fluid/secondary fluid 
mixture, it is advantageous to have available a plurality of injection 
conduits distributed on the circumference of the admission channel. 
It will be noted that, in the embodiment presented in FIGS. 3 and 4, the 
ejection channel 113 presents an axial direction. It will also be noted 
that, with such a mode of injection (peripheral-helicoidal), it is not 
necessary to place a deflector device upstream of the turbine 112. 
According to a variant embodiment (not shown) (angle .varies. fixing the 
initial slope of the injection helix, angle .beta. defining the nominal 
diameter of the injection of this helix), the following are continuously 
varied: 
angle .varies., which has for its purpose to vary the nominal speed of the 
nominal working point and/or 
angle .beta., which has for its purpose to modify the working 
characteristics, with priority in secondary mass flow, therefore the 
maximum power at the nominal working point. 
It will be noted that the rotation shaft of the turbine may be directly 
constituted by a mandrel rod 160 of a tool 180. 
Transmission of the motive force from a turbine to a tool raises problems 
of technical implementation such as: 
efforts proportional to the inertia of the transmission members and to the 
square of the speed of rotation and 
the necessity of employing a transmission whose geometry may vary by the 
relative mobility of a certain number of constituent parts in order in 
particular to be able to fix the tool on the transmission. 
However, in the case of the tool-turbine assembly shown in FIG. 3 and, 
taking into account the moderate speeds of rotation of the device, it is 
possible to use simple bearings for guiding in rotation and translation, 
which are rustic and inexpensive, currently used at the present time in 
the industry. 
In the example of such an embodiment, the turbine 112 is force-fitted on 
the rear part 160 (mandrel rod) of the cylindrical tool 180 which may be a 
mill. 
The tool may present, to that end, at the level of its mandrel rod, an 
assembly of small rectilinear edges oriented along the axis of rotation of 
said tool. 
In a variant, the tool may be associated with an intermediate fixation 
piece (not shown). 
In the example shown, the suspension bearing of the tool-turbine assembly 
is constituted by roller bearings 183 and 184. Roller bearing 183 abuts on 
the hub of the turbine. A spacer 185, suitably mounted to slide on said 
tool, maintains the spaced apart relationship with roller bearing 184 so 
as to ensure the necessary functional clearance along the axis of rotation 
at the level of the bearing body 186. 
A ring 187, made of a material whose coefficient of heat expansion is less 
than that of the material constituting said tool, is mounted tightened on 
said tool and immobilizes rollers 183 and 184 and the spacer 185 in 
translation (along the axis of rotation of the tool). 
The assembly thus produced is constituted by a small number of parts which 
are simple, inexpensive and of low inertia around the axis of rotation. 
According to the embodiment shown in FIG. 5 (second variant), the mode of 
injection of the primary fluid is different again. 
As before, the references of FIG. 2 have been employed in this Figure, 
increased by two units of hundred. 
The injection means 214 is here constituted by four conduits 230 (three are 
shown) opening inside the admission channel 211, so that the primary fluid 
Fp is injected parallel to the axis A of the device and along the walls. 
Such a mode of injection is called peripheral. 
As in the example of FIG. 2, the primary fluid entrains the secondary fluid 
towards the turbine. 
It will be noted that the number of primary fluid introduction conduits 230 
may vary and that the plurality of conduits is preferably distributed 
along the circumference of the admission channel 211. 
In a variant, each conduit 230 may pivot about its horizontal axis to 
generate a flow which is no longer axial but helicoidal. In this case, a 
helicoidal-peripheral flow is obtained with the advantages mentioned with 
reference to FIGS. 3 and 4, and associated with an upstream distributor 
217. 
FIGS. 6 and 7 show a third variant embodiment of the turbine device 
according to the invention. As before, the references of FIG. 2 are 
employed, increased by three units of hundred for the equivalent means 
shown in FIGS. 2 and 6. 
The device 310 according to FIG. 6 presents the particularity of having: 
a primary air injection of annular type and at the level of the walls 
(peripheral-annular injection), 
actuators adapted to vary the inlet section of the secondary fluid, the 
injection section of the primary fluid and the ejection section of the 
ejection channel. 
In fact, the secondary fluid is introduced in the admission channel via an 
inlet device 350 presenting an opening 351 of variable section. The inlet 
device is screwed and unscrewed on the body of the admission channel 311 
via a thread 352. 
Such screwing (or unscrewing) is controlled by a means for modifying the 
inlet section, namely the actuator 353. This actuator 353 is itself 
controlled by the processing means 321. As shown by arrow B, the action of 
this actuator 353 enables the inlet section of the secondary fluid to be 
varied. 
Correspondingly, an actuator 354 for varying the ejection section of the 
device allows screwing or unscrewing of an outlet device 356 via a thread 
357. As shown by arrow C, the action of this actuator 354 enables the 
ejection section to be varied. 
In the same manner as before, the actuator 354 is controlled by the 
processing means 321. 
An actuator 355 making it possible to vary the primary fluid injection 
section in the admission channel 311 is also provided. 
The primary fluid Fp is introduced in the admission channel 311, passing 
through a minimum section 358 called neck section of the flow, this 
section varying by means of the actuator 355. 
This neck is created (FIG. 7), on the one hand, by an annular swell 359 of 
the wall of the admission channel 311 and, on the other hand, by a 
displaceable element 360 placed in the upstream part 311a of the admission 
channel 311 and opposite the annular swell 359. 
By sliding element 360 in the direction of arrow D, the section of the 
primary fluid supply neck 358 is variable. Slide is effected by screwing 
and unscrewing the displaceable element 360 in the admission channel 311 
by means of the thread 361. 
It will be noted that introduction of the primacy fluid Fp in the admission 
channel 311 is effected in manner parallel to the longitudinal axis A of 
the device. Such injection is effected over the whole periphery of the 
admission channel and in the vicinity of the walls. Such injection is 
called peripheral-annular injection. 
As shown in FIG. 7, the respective shapes of the body 370 of the admission 
channel 311 and of the displaceable element 360 which faces it constitute 
an annular convergent-divergent nozzle. Said annular convergent-divergent 
nozzle, supplied with primary fluid by an annular section 371, therefore 
has a neck 358 and an outlet section 372 of which the respective surfaces 
may vary when the actuator 355 drives element 360 in translation. In the 
convergent part of said nozzle, the primary fluid undergoes a subsonic 
acceleration until it reaches sonic velocity at said neck 358. In the 
divergent part of said nozzle, the primary fluid undergoes a supersonic 
acceleration. In operation, the primary fluid supply pressure must be 
sufficient in order that, taking into account the value of the surface of 
the injection section 372, the ejection of said primary fluid in the 
admission channel be supersonic and at a static pressure higher than that 
of said secondary fluid in section 373 of element 360. In fact, there is 
then created on outlet lips 374 of element 360 an expansion beam and a 
turbulent slipstream adapted to promote exchange of energy between said 
primary and secondary fluids. Moreover, the peripheral injection in an 
annular convergent-divergent nozzle makes it possible, on the one hand, to 
increase the energetic exchange surface between said primary and secondary 
fluids and, on the other hand, to obtain in the inlet plane 375 (FIG. 6) 
of said distributor 317 an optimum velocity profile characterized in that 
the local mean velocity is all the greater as it is located near the head 
of the blades 18 of said distributor 317. 
Such a dimensional and functional arrangement of a convergent-divergent 
nozzle at the level of the injection of the primary fluid may be 
generalized for all primary fluid injections, whatever the variant 
embodiment considered. 
Such a device makes it possible, by acting on the dimensions of the primary 
and secondary fluid admission channels and on the dimension of the 
ejection channel, to vary the nominal working point of the turbine. 
Of course, the assembly of actuators 353, 354, 355 is controlled by the 
processing means 321. 
Another variant embodiment of the ejection device consists in producing an 
ejection channel from the conduit conducting the fluid from the outlet 
plane of the turbine towards the level of the admission of the secondary 
fluid and thus making it possible to recycle in the device itself part of 
the ejected fluid. 
The interest of the device according to the invention, whatever the variant 
embodiment chosen, resides in the fact that the torque delivered is high 
for low speeds of rotation and that the power delivered is comparable to 
that of existing turbines. 
Blades which may be used in each of the variant embodiments described 
hereinabove will now be described. 
However, to facilitate understanding of this description, the definitions 
of the principal terms used will be recalled: 
The leading edge of a blade is the portion of curve located at the upstream 
end of said blade and which receives the flow. 
The trailing edge of a blade is the portion of curve located at the 
downstream end of said blade and from which the flow escapes. 
A blade is constituted by a so-called undersurface and a so-called upper 
surface; these two surfaces are secant along the trailing edge and leading 
edge lines. 
An airfoil of a blade is the closed curve resulting from the intersection 
of the under- and upper surfaces with a cylindrical surface having for 
axis that of the hub bearing the blade. 
The chord of an airfoil is the segment of straight line joining on a blade 
airfoil the points of the trailing edge and of the leading edge. 
A leading edge angle is the angle made by a straight line tangential to the 
airfoil at the point of the leading edge with the direction of the axis of 
said hub. 
A trailing edge angle is the angle made by a straight line tangential to 
the airfoil at the point of the trailing edge with the direction of the 
axis of the hub. 
The thickness of an airfoil at a given point of the undersurface is the 
length of the segment of straight line defined by said point of the 
undersurface and the point of the upper surface defined by the 
intersection of the upper surface with a straight line perpendicular to 
the undersurface at said point of the undersurface. 
The root of a blade is the part off the blade adjacent the hub. 
The head of a blade is the Dart of the blade most remote from the hub. 
The blades are described with reference to FIG. 2, but may equally well be 
used with the variant embodiments shown in FIGS. 3 to 6. 
The turbine 12 (FIG. 8) is constituted by a cylindrical hub on which are 
radially disposed blades 18 equally distributed in a circle. These blades 
are identical for the same turbine. The leading edge angles are constant 
all along the leading edge for all the blades of the same turbine, in the 
same way as for the trailing edge angles. The chord of the airfoils is 
constant for all the airfoils of all the blades of the same turbine. The 
thickness of an airfoil is constant, apart from in the immediate vicinity 
of the trailing edge and of the leading edge. 
In a variant, the thickness of the airfoils of a blade increases from the 
head to the root of the blade in order to take into account the mechanical 
stresses increasing from the head to the root of the blade. 
It will thus be noted that the blades present a constant chord, a constant 
thickness along a cylindrical section having for axis that of said 
turbine, constant leading edge angles, and constant trailing edge angles. 
It will also be noted that the curved under- and upper surfaces of the 
blades are generated by a conical surface whose apex is the point of 
intersection of the axis of said turbine with the planes, perpendicular to 
the axis of said turbine, inlet for the upstream part and outlet for the 
downstream part, and whose apex angle is a function of the leading edge 
angle for the upstream part and of the trailing edge angle for the 
downstream part. 
Such blades are simple to produce (machining, moulding, etc. . . . ) and 
are inexpensive. 
in addition, such blades present the advantage, when the speed of the 
turbine increases, of likewise increasing the velocity of the flow in the 
inter-blade channel. From a certain value of said flow velocity, 
expansions and recompressions substantially degrade the flow in the 
inter-blade channel. This results in a phenomenon of self-limitation of 
the free operating speed. 
It will be noted that, thanks to the relatively low speeds of rotation 
(from 0 to 60000 rpm) simple, current turbine suspension bearings may be 
used. 
One of the advantages of the present invention is its lightness, its 
silence in operation, its reliability. In addition, simple, inexpensive 
transmissions existing on the market may easily be adapted on such a 
turbine to drive tools between 0 and 60000 rpm. 
The present invention is, of course, not limited to the embodiments chosen 
and covers any variant within the scope of the man skilled in the art. In 
particular, it is possible, in a variant, to produce, at the level of the 
ejection planes of the device, a pressure lower than the general level of 
pressure prevailing in the environment outside the device. In that case, 
the nominal power level of the device does not vary substantially; on the 
contrary, the mass flow injected decreases substantially, this phenomenon 
characterizing the introduction of a second source of energy materialized 
by the depression at the outlet of the ejection channel, to the detriment 
of the source of energy defined by the primary fluid under pressure; 
however, the precision of the control of the speed of rotation of the 
turbine by acting on the primary fluid injection pressure Pp decreases.