Aerodynamic Performance of Propellers

In the wake of technological advancement, engineers behind the design and manufacture of propellers have had to revisit their drawing boards in a bid to come up with more efficient but less noisy propellers. Unmanned aircraft systems (UAS) and modern aircraft propellers have had some modifications rendered on them in order to match stated requirements in regards to noise reduction and aerodynamic performance. In this paper, a report is written to highlight improvements that are being done on propellers to help reduce noise and improve aerodynamic performance in aircraft, their propellers, and UAS propellers as well.

Advances made on propellers

Due to an increased need for lighter and less noisy propellers, manufactures have resorted to the use of fiber reinforced multi-layer composite propeller. The carbon fiber reinforced plastic propeller blades are a replacement of the traditional Aluminum blades. To withstand static load distribution, find stresses and deflections, the propeller blades are designed in a favorable way compared to aluminum blades leading a stronger propeller that works efficiently (Hartzell Propeller, 2018). Carbon fiber reinforced plastic propeller blades also allow the use of separate and detachable blades, an advantage over the wooden propeller blades.

Since propeller blades can now be separate and detachable, prop planes can be made more efficient and less noisy by increasing the number of blades in a prop. By increasing the number of blades there is a reduction in the amount of load a single blade has to bear, hence leading to a slower spinning prop which in the end reduces the noise that would have produced immensely (Farokhi, 2014).

            An improvement in the design and manufacture of propellers is also evidenced by adjustments in the constant spend propellers. To achieve this, engineers use an advantage provided by separate and detachable blades together with a hydraulic system that can enable blades to change the angle or the blade pitch to maintain a chosen rotational speed while in the air using a counterweight system (Wang, Zhou, Zhu & Xu, 2018). The end result, for example, is an Unmanned Aircraft System (UAS) that can rise from the ground and move back or forward with much ease as compared to mechanical propeller governed systems.

Swept-tip propeller blade design is another improvement on propeller design and this is focused on of increasing takeoff and climb thrust without increasing noise produced by propellers (Hartzell Propeller, 2018). Swept-tip propellers are efficient because the propeller diameter can be increased to much the required standard for better performance in both aircraft and UAS. An increase in sweep close to the tip of the blade decelerates the formation of sudden onset shock wave resulting to more power being unleashed by the propeller accompanied by less noise due to reduced shock waves (Wang, Zhou, Zhu & Xu, 2018).

            Aluminum alloy blades are also a major improvement in propeller design having replaced the wooden propellers that were used in the past years. Aluminum being a lighter metal makes propellers much lighter hence making the propellers rotate at a higher speed to provide an advantage in aerodynamic performance (Hartzell Propeller, 2018). Power is easily converted to thrust by aluminum alloy propeller blades. The blades are durable due to the nature of fatigue resistant aluminum alloy material they are made of. In the event that the blades fail, repairs can be done easily.

Total noise reduction has proven a bit challenging to propeller manufactures but the aerodynamic performance of propellers in aircraft and UAS has been immensely improved by the above advances.

References

Farokhi, S. (2014). Aircraft Propulsion. Hoboken: Wiley.

Hartzell Propeller. (2018). 5 Innovations in Propeller Design - Hartzell Propeller. Retrieved from http://hartzellprop.com/5-innovations-in-propeller-design/

Hartzell Propeller. (2018). The Future of UAV Propeller Technology - Hartzell Propeller. Retrieved from http://hartzellprop.com/the-future-of-uav-propeller-technology/

Wang, K., Zhou, Z., Zhu, X., & Xu, X. (2018). Aerodynamic design of multi-propeller/wing integration at low Reynolds numbers. Aerospace Science And Technology, 84, 1-17. doi: 10.1016/j.ast.2018.07.023