Propeller blade beta twist
A propeller blade comprises a blade root coupled to a rotor hub and a blade tip. The propeller blade is composed of airfoil cross-sections, each cross-section a distance away from the rotor hub. Each airfoil is designed with particular structural characteristics that improve the overall amount of thrust generated on the quadcopter. Namely, each airfoil possesses a β angle and chord length whose values depend on the distance of that airfoil from the rotor hub. For example, the relationship between an airfoil's β angle and its distance from the rotor hub is described by a power law. Additionally, the relationship between an airfoil's chord length and its distance from the rotor hub is described using a polynomial regression. Compared to current, off the shelf propeller blades, the current propeller blade embodiment achieves the same thrust at a lower RPM, thereby yielding benefits in reduced acoustic noise and improved response time.
1. A propeller blade comprising:
a root, a tip, and a plurality of airfoil cross-sections extending from the root to the tip, each airfoil cross-section having a β angle and located at a distance, X, from the root, wherein the airfoil cross-section with a maximum β angle is located at X/R=0.1 and the airfoil cross-section with a minimum β angle is located at X/R=1.0 where R is the radius of the blade, wherein the β angle of each airfoil cross-section is governed by the equation: β=B 1 (X/R) −B 2 for 0.1≤X/R≤1.0, where B 1 and B 2 are constants based on a curve fit between β and X/R.
2. The propeller blade of claim 1 , wherein B 1 is between 5 and 7 and B 2 is between −0.75 and −1.05.
3. The propeller blade of claim 1 , wherein the maximum β angle located at X/R=0.1 is between 40 and 55 degrees.
4. The propeller blade of claim 1 , wherein the minimum β angle located at X/R=1.0 is between 2 and 10 degrees.
5. The propeller blade of claim 1 , wherein the radius of the blade is 3 to 7 inches in length.
6. The propeller blade of claim 1 , wherein the root of the propeller blade is coupled to a rotor hub at distances of 0<X/R≤0.1.
7. A propeller blade comprising:
a root, a tip, and a plurality of airfoil cross-sections extending from the root to the tip, each airfoil cross-section having a chord length, C, and located at a distance, X, from the root, wherein the airfoil cross-section with a maximum chord length is located between 0.5≤X/R≤0.75, where R is the radius of the blade, wherein the chord length of each airfoil cross-section is governed by the polynomial equation: C/R=A 1 (X/R) 3 +A 2 (X/R) 2 +A 3 (X/R)+A 4 for 0.1≤X/R≤1.0, where A 1 , A 2 , A 3 , and A 4 are constants based on a curve fit between C/R and X/R.
8. The propeller blade of claim 7 , wherein A 1 is between −0.7 and −0.5, A 2 is between 0.3 and 0.4, A 3 is between 0.2 and 0.3, and A 4 is between 0.04 and 0.06.
9. The propeller blade of claim 7 , wherein the cross section further comprises:
a maximum camber, MC, governed by the equation: MC/C=D 1 (X/R)+D 2 , where D 1 and D 2 are constants based on a linear curve fit between MC/C and X/R.
10. The propeller blade of claim 9 , wherein D 1 is between −4.5 and −9.0 and D 2 is between 9 and 12.
11. The propeller blade of claim 7 , wherein the cross section further comprises:
a maximum thickness, MT, governed by the equation: MT/C=E 1 (X/R) −E 2 , where E 1 and E 2 are constants based on a power law between MT/C and X/R.
12. The propeller blade of claim 11 , wherein E 1 is between 5 and 7 and E 2 is between 0.5 and 1.0.
13. A propeller assembly comprising:
a rotor hub; and
at least two propeller blades, each propeller blade further comprising:
a root and a tip, wherein the root of the propeller blade is connected to the rotor hub and the tip of the propeller blade is located a length of the propeller blade, R, from the rotor hub; and
a plurality of airfoil cross-sections extending from the root to the tip, each airfoil cross-section located at a distance, X, from the rotor hub, wherein airfoil cross-sections located between 0.5≤X/R≤1.0 each have a β angle that is smaller than 25% of the maximum β angle in the plurality of airfoil cross-sections, wherein the β angle has a maximum value between 40 and 55 degrees.
14. The propeller blade of claim 13 , wherein β angle is maximized at X/R=0.1.
15. The propeller blade of claim 13 wherein the β angle is minimized at X/R=1.0.
16. The propeller blade of claim 13 wherein the β angle has a minimum value between 2 and 7 degrees.
17. The propeller assembly of claim 13 , wherein the airfoil cross-section of the propeller blade that possesses a maximum chord length is located between 0.5≤X/R≤1.0.