Ducted Fan Air Data System

Abstract

An air data system and method for a ducted fan air-vehicle is described. The air data system includes a plurality of air pressure sensors placed around a lip of an air duct of the ducted fan air-vehicle. The air data system calculates the speed and direction of airflow surrounding the ducted fan air-vehicle based on pressure data measured across the lip of the air duct. Additionally, the air data system may estimate forces generated by airflow surrounding the air-vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Presently preferred embodiments are described below in conjunction with the appended drawing figures, wherein like reference numerals refer to like elements in the various figures, and wherein:

FIG. 1 is a pictorial representation of a ducted fan air-vehicle including an air data system, according to an example;

FIG. 2 is a cross section of a side of the air duct of FIG. 1, taken from point A to A, with a pressure sensor mounted in a lip of the air duct, according to an example;

FIG. 3 is a top view of an air data system, according to an example;

FIG. 4 is a pictorial side view representation of airflow surrounding the air duct, according to an example;

FIG. 5 is a flow chart depicting a method for air data generation, according to an example;

FIG. 6 is a flow diagram depicting computation data flow for applying a linear curve fit for generating air data of FIG. 5, according to an example; and

FIG. 7 is a graph illustrating a linear curve fit for velocity data against compensated and normalized pressure data, according to an example.

Claims

1. An air data system for an air-vehicle, comprising in combination: an air duct having a lip;a plurality of air pressure sensors placed around the lip of the air duct operable to measure pressure data; anda processor operable to receive the pressure data from the plurality of air pressure sensors and calculate speed and direction of airflow surrounding the air-vehicle based on the pressure data measured by the plurality of air pressure sensors.

2. The system of claim 1, wherein the plurality of air pressure sensors are flush mounted sensors.

3. The system of claim 2, wherein the flush mounted sensors are mounted at a high velocity low pressure region at the lip of the air duct.

4. The system of claim 1, wherein the plurality of air pressure sensors placed around the lip of the air duct are mounted within a duct lip port.

5. The system of claim 1, wherein the plurality of air pressure sensors includes at least one pair of pressure sensors placed around the lip substantially 180 degrees apart.

6. The system of claim 1, wherein the processor is operable to estimate the air-vehicle velocity based on the speed and direction of the airflow surrounding the air-vehicle.

7. The system of claim 1, wherein the processor is operable to estimate forces acting on the air-vehicle generated by airflow surrounding the air-vehicle.

8. The system of claim 7, wherein the force acting on the air-vehicle is sent to an avionics system of the ducted fan air-vehicle.

9. The system of claim 1, further comprising means for forcing air through the air duct.

10. The system of claim 9, wherein the means for forcing air through the air duct is a fan.

11. A method of measuring air data for a ducted fan air-vehicle, comprising in combination: placing a plurality of air pressure sensors within a lip of an air duct of the air-vehicle such that the plurality of air pressure sensors includes at least one pair of air pressure sensors that measure pressure at a first point on the lip of the air duct and at a second point on the lip of the air duct substantially 180 degrees away from the first point; andconnecting a processor to the plurality of air pressure sensors, wherein the processor is operable to calculate speed and direction of airflow surrounding the air-vehicle based on air that flows through the at least one pair of air pressure sensors.

12. The method of claim 11, wherein placing a plurality of air pressure sensors on the lip of the air duct of the air-vehicle includes flush mounting the plurality of air pressure sensors to the lip of the air duct.

13. The method of claim 12, wherein flush mounting the plurality of air pressure sensors to the lip of the air duct includes mounting the plurality of air pressure sensors at a high velocity low pressure region at the lip of the air duct of the air-vehicle.

14. The method of claim 12, wherein flush mounting the plurality of air pressure sensors to the lip of the air duct includes mounting at least one pair of air pressure sensors around the lip substantially 180 degrees apart from each other.

15. The method of claim 11, wherein the processor is operable to estimate forces acting on the air-vehicle generated by the airflow surrounding the air-vehicle.

16. The method of claim 11, wherein the processor is operable to estimate air-vehicle velocity based on the speed and direction of airflow surrounding the air-vehicle.

17. The method of claim 11, wherein the processor operable to calculate speed and direction of airflow calculates direction of airflow by: calculating a plurality of pressure differentials between the first point on the lip of the air duct and the second point on the lip of the air duct substantially 180 degrees apart from the first point;calculating a plurality of vectors from the plurality of pressure differentials;summing the plurality of vectors; andcalculating the direction of the airflow based on the sum of the plurality of vectors.

18. A method for calculating speed and direction of airflow surrounding a ducted fan air-vehicle, comprising in combination: obtaining a plurality of pressure measurements within a lip of an air duct of the air-vehicle;compensating the plurality of pressure measurements for vehicle attitude;calculating a plurality of pressure differentials across the lip of the air duct;compensating the plurality of pressure differentials for a fan speed of the fan of the air-vehicle and air density to arrive at a plurality of compensated pressure differentials;applying a linear velocity curve fit for the compensated pressure differentials;generating a plurality of individual velocity vectors across the lip of the air duct based on the linear velocity curve fit for the compensated pressure differentials; andgenerating a total velocity vector of the airflow based on the plurality of individual velocity vectors across the lip of the air duct.

19. The method of claim 18, wherein compensating the plurality of pressure measurements for vehicle attitude includes compensating for the ducted fan air-vehicle pitch attitude.

20. The method of claim 18, wherein compensating the plurality of pressure measurements for vehicle attitude includes compensating for the ducted fan air-vehicle roll attitude.