Propeller Research Tunnel

Propeller Research Tunnel
	A test fuselage in the Propeller Research Tunnel at Langley Research Center with Cowl No. 10, a prototype cowl designed to reduce drag caused by the exposed radial engine. (NASA,1926)
Acronym	PRT
Other names	Wind Tunnel No. 3
Uses	Wind tunnel for full-scale aircraft used primarily in reducing drag caused by propellers and exposed engines
Notable experiments	Engine Cowling, The NACA Cowl, Retractable Landing Gear
Related items	NACA, Langley Research Center

Last updated June 01, 2019

The Propeller Research Tunnel (PRT) was the first full-scale wind tunnel at the National Advisory Committee for Aeronautics (NACA) Langley Research Center, and the third at the facility. It was in use between 1927 and 1950 and was instrumental in the drag reduction research of early American aeronautics. In 1929, NACA was awarded its first Collier Trophy for the NACA cowling which was tested and developed using the Propeller Research Tunnel.^[1]

Wind tunnel tool used in aerodynamic research to study the effects of air moving past solid objects

Wind tunnels are large tubes with air moving inside. The tunnels are used to copy the actions of an object in flight. Researchers use wind tunnels to learn more about how an aircraft will fly. NASA uses wind tunnels to test scale models of aircraft and spacecraft. Some wind tunnels are big enough to hold full-size versions of vehicles. The wind tunnel moves air around an object, making it seem like the object is really flying.

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Aeronautics is the science or art involved with the study, design, and manufacturing of air flight capable machines, and the techniques of operating aircraft and rockets within the atmosphere. The British Royal Aeronautical Society identifies the aspects of "aeronautical Art, Science and Engineering" and "the profession of Aeronautics ."

Purpose

The main purpose of the Propeller Research Tunnel was researching the aerodynamic efficiency of propellers on radial engine aircraft. In 1917, William F. Durand published NACA Technical Report 17 on his work with isolated propellers in Stanford University's wind tunnel, however these results did not match with the data NACA had collected for propellers connected to fuselages.^[2] Additionally, little was known about the limitations of propellers. Propellers had efficiency issues caused by loss of compression at the tips at high speeds.^[3] In 1923, Langley engineer Fred Weick, suggested NACA build a wind tunnel with a 20 foot diameter throat, capable of speeds up to 100 miles per hour in order to perform full-scale propeller tests.^[4] According to Weick, British engineers were running tests on scale propellers at the time, but were unable to obtain accurate results due to a scaling issue related to the Reynolds number in the smaller wind tunnels. NACA had been using the Variable Density Tunnel in order to increase the density of air to keep the Reynolds number in testing similar to the Reynolds number experienced by full-scale aircraft. However, the Variable Density Tunnel was not able to provide consistent data for propellers, so NACA built the Propeller Research Tunnel.^[5]

Leland Stanford Junior University is a private research university in Stanford, California. Stanford is known for its academic strength, wealth, proximity to Silicon Valley, and ranking as one of the world's top universities.

Fred Ernest Weick was one of the United States' earliest aviation pioneers, working as an airmail pilot, research engineer, and aircraft designer. A contemporary of aviation legends Charles Lindbergh and Amelia Earhart, he did not receive the same attention as his more glamorous colleagues, yet his contribution to the United States' struggling aircraft industry was "in the league of the Wright Brothers".

The Reynolds number is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow. These eddy currents begin to churn the flow, using up energy in the process, which for liquids increases the chances of cavitation. The Reynolds number has wide applications, ranging from liquid flow in a pipe to the passage of air over an aircraft wing. It is used to predict the transition from laminar to turbulent flow, and is used in the scaling of similar but different-sized flow situations, such as between an aircraft model in a wind tunnel and the full size version. The predictions of the onset of turbulence and the ability to calculate scaling effects can be used to help predict fluid behaviour on a larger scale, such as in local or global air or water movement and thereby the associated meteorological and climatological effects..

History

NACA began work on the Propeller Research Tunnel under direction of Director of Aeronautical Research George W. Lewis in 1925 and completed its construction in 1927. Built using two 1000-horsepower diesel submarine engines, and an 8-blade, 27-foot diameter fan, the Propeller Research Tunnel was capable of pushing air in a 20-foot stream at 110 miles per hour.^[2] The PRT remained operational until it was demolished in 1950 when NACA needed a place to build their 8-foot Transonic Pressure Tunnel.^[6]

George William Lewis was the Director of Aeronautical Research at the National Advisory Committee for Aeronautics (NACA) until he retired in 1947. He taught at Swarthmore College from 1910 to 1917.

Use in Research

Propeller Research

The Propeller Research Tunnel was used in the development of more efficient propellers that did not lose compression at the blade tips at high speeds. NACA was also able to test full scale propellers to find a blade shape that maximized efficiency and performance where previous designs had failed.^[7]

NACA cowling

The PRT was also used to develop a way to reduce the drag produced by the exposed pistons of radial turbine engines. By testing various cowlings on full-scale models in the PRT, NACA was able to produce the NACA cowl, which won the Collier Trophy in 1929 for its impact on aeronautics.^[1] It was predicted that the cowling, by reducing drag and increasing engine cooling, would save the American aircraft industry upwards of $5 million, and the cowling and its variants were quickly adopted by plane manufacturers.^[1]

The Collier Trophy is an annual aviation award administered by the U.S. National Aeronautic Association (NAA), presented to those who have made "the greatest achievement in aeronautics or astronautics in America, with respect to improving the performance, efficiency, and safety of air or space vehicles, the value of which has been thoroughly demonstrated by actual use during the preceding year."

Other

Similarly, the PRT found that engine placement and the fixed landing gear contributed greatly to drag. NACA engineers worked to create a retractable landing gear and found that multi-engine planes benefited from having their engines in-line with the leading edge of the wing. Both of these discoveries were also quickly adopted by airplane manufacturers.^[3] Data collected in the PRT was used heavily in the design of many World War II planes including the Boeing B-17 Flying Fortress, Boeing B-24 Liberator, and the Douglas DC-3.^[2]

World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. It included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, and the only use of nuclear weapons in war.

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Related Research Articles

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References

1 2 3 Hansen, James R. (1998). Mack, Pamela E. (ed.). From Engineering to Big Science The NACA and NASA Collier Trophy Research Project Winners. NASA. pp. 1–27.
1 2 3 Baals, D.D.; Corliss, W.R. (1981). The Wind Tunnels of NASA. NASA. p. 21.
1 2 Gray, George W. (1948). Frontier of Flight: The Story of NACA Research. Alfred A. Knopf, Inc. pp. 36–37.
↑ Hansen, James R. (1986). Engineer in Charge: A History of the Langley Aeronautical Laboratory, 1917-1958. NASA. p. 87.
↑ Taylor, D. Bryan; Kinney, Jeremy; Lee, J. Lawrence (2003). Hansen, James R. (ed.). The Wind and Beyond: A Documentary Journey into the History of Aerodynamics in America. NASA. pp. 556, 557.
↑ "Propeller Research Tunnel". NASA. NASA . Retrieved June 4, 2018.
↑ Ames, Joseph S.; et al. (November 20, 1928). Fourteenth Annual Report of the National Advisory Committee for Aeronautics (Report). pp. 27–30. Retrieved June 5, 2018.

External links

NASA - Propeller Research Tunnel

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[Engineering_Science-1] 1 2 3 Hansen, James R. (1998). Mack, Pamela E. (ed.). From Engineering to Big Science The NACA and NASA Collier Trophy Research Project Winners. NASA. pp. 1–27.

[WtoN,_Baals,_Corliss-2] 1 2 3 Baals, D.D.; Corliss, W.R. (1981). The Wind Tunnels of NASA. NASA. p. 21.

[FoF,_Gray-3] 1 2 Gray, George W. (1948). Frontier of Flight: The Story of NACA Research. Alfred A. Knopf, Inc. pp. 36–37.

[EiC,_Hansen_1986-4] Hansen, James R. (1986). Engineer in Charge: A History of the Langley Aeronautical Laboratory, 1917-1958. NASA. p. 87.

[WaB,_Hansen_2003-5] Taylor, D. Bryan; Kinney, Jeremy; Lee, J. Lawrence (2003). Hansen, James R. (ed.). The Wind and Beyond: A Documentary Journey into the History of Aerodynamics in America. NASA. pp. 556, 557.

[nasaprt-6] "Propeller Research Tunnel". NASA. NASA . Retrieved June 4, 2018.

[NACA_Annual_Report-7] Ames, Joseph S.; et al. (November 20, 1928). Fourteenth Annual Report of the National Advisory Committee for Aeronautics (Report). pp. 27–30. Retrieved June 5, 2018.