Propeller operation
A method of and apparatus for operating a propeller, the propeller moving through a fluid, the method including: measuring a value of a property of the fluid (e.g. a parameter related to the density of the fluid); measuring a value of a parameter, the parameter related to one or more forces applied to the propeller (e.g. a torque applied to the propeller) or derived at least in part from the action of the propeller (e.g. a thrust produced by the action of the propeller, a drag produced by the action of the propeller, or a velocity produced by the action of the propeller); and controlling the propeller depending on a function of the measured value of the property of the fluid and the measured value of parameter. The propeller may be a propeller on an aircraft.
1. A method of operating a propeller, the propeller moving through a fluid, the method comprising:
measuring a value of a property of the fluid;
measuring a value of a parameter, the parameter being related to one or more forces applied to the propeller or derived at least in part from action of the propeller;
using the measured value of the property of the fluid and the measured value of the parameter, determining a desired rotational speed for the propeller; and
controlling the propeller such that the rotational speed of the propeller is equal to the determined rotational speed.
2. The method according to claim 1 , wherein measuring the value of the parameter comprises:
measuring a value for thrust produced at least in part by the action of the propeller.
3. The method according to claim 1 , wherein measuring the value of the parameter comprises:
measuring a value of a parameter related to drag produced at least in part by the action of the propeller.
4. The method according to claim 1 , wherein measuring the value of the parameter comprises:
measuring a value for a torque applied to the propeller; and
measuring a value for a velocity produced at least in part by the action of the propeller.
5. The method according to claim 2 , wherein determining a rotational speed for the propeller comprises calculating:
n
2
=
T
3
a
0
ρ
D
4
where:
n is the rotational speed for the propeller;
T is the measured thrust produced by the action of the propeller;
ρ is a density of the fluid;
D is a diameter of the propeller; and
a 0 is a constant.
6. The method according to claim 3 , wherein determining a rotational speed for the propeller comprises calculating:
n
2
=
F
D
3
a
0
ρη
i
N
D
4
where:
n is the rotational speed for the propeller;
F D is a drag force;
η i is an installation efficiency factor;
N is a total number of propellers;
ρ is a density of the fluid;
D is a diameter of the propeller; and
a 0 is a constant.
7. The method according to claim 4 , wherein determining a rotational speed of the propeller comprises calculating:
n
=
-
(
b
1
V
D
)
+
(
b
1
V
D
)
2
-
4
b
0
(
b
2
V
2
D
2
-
2
π
Q
ρ
D
5
)
2
b
0
where:
n is the rotational speed for the propeller;
V is the measured value for the velocity produced by the action of the propeller;
Q is the measured value for the torque applied to the propeller;
p is property density of the fluid;
D is a diameter of the propeller;
b o is a constant;
b 1 is a constant; and
b 2 is a constant.
8. The method according to claim 5 , wherein a constant is determined by approximating an optimum propeller efficiency using a polynomial, the constant being a coefficient of a term of the polynomial.
9. The method according to claim 6 , wherein a constant is determined by approximating an optimum propeller efficiency using a polynomial, the constant being a coefficient of a term of the polynomial.
10. The method according to claim 7 , wherein a constant is determined by approximating an optimum propeller efficiency using a polynomial, the constant being a coefficient of a term of the polynomial.
11. The method according to claim 1 , wherein the propeller is a propeller of an unmanned aircraft.
12. The method according to claim 1 , wherein the propeller is driven by a gas turbine engine.
13. The method according to claim 12 , wherein the propeller is a free turbine turboprop.
14. A non-transitory program or plurality of programs arranged such that when executed by a computer system or one or more processors it/they cause the computer system or the one or more processors to operate in accordance with the method of claim 1 .
15. A non-transitory machine readable storage medium storing a program or at least one of the plurality of programs according to claim 14 .
16. Apparatus for operating a propeller, the propeller moving through a fluid, the apparatus comprising:
one or more sensors arranged to:
measure a value of a property of the fluid; and
measure a value of a parameter, the parameter being related to one or more forces applied to the propeller or derived at least in part from the action of the propeller;
one or more processors configured to determine a rotational speed for the propeller using the measured value of the property of the fluid and the measured value of the parameter; and
means for controlling the propeller such that the rotational speed of the propeller is equal to the determined rotational speed.