Direct measurements of skin friction in a scramjet combustor

An experimental investigation was conducted to measure skin friction along the chamber walls of supersonic combustors. A direct force measurement device was used to simultaneously measure an axial and transverse component of the small tangential shear force passing over a non-intrusive floating element. This measurement was made possible with a sensitive piezoresistive deflection sensing unit. The floating head is mounted to a stiff cantilever beam arrangement with deflection due to the flow on the order of 0.00254 mm (0.0001 in). This allowed the instrument to be a non-nulling type. A second gauge was designed with active cooling of the floating sensor head to eliminate non-uniform temperature effects between the sensor head and the surrounding wall. The key to this device is the use of a quartz tube cantilever with piezoresistive strain gages bonded directly to its surface. A symmetric fluid flow was developed inside the quartz tube to provide cooling to the backside of the floating head. Tests showed that this flow did not influence the tangential force measurement. Measurements were made in three separate combustor test facilities. Tests at NASA Langley Research Center consisted of a Mach 3.0 vitiated air flow with hydrogen fuel injection at Pt = 500 psia (3446 kPa) and Tt = 3000 R (1667 K). Two separate sets of tests were conducted at the General Applied Science Laboratory (GASL) in a scramjet combustor model with hydrogen fuel injection in vitiated air at Mach = 3.3, Pt = 800 psia (5510 kPa), and Tt = 4000 R (2222 K). Skin friction coefficients between 0.001–0.005 were measured dependent on the facility and measurement location. Analysis of the measurement uncertainties indicate an accuracy to within ±10–15% of the streamwise component.

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Skin-Friction Measurements in Supersonic Combustion Flows of a Scramjet Combustor

44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit ◽

10.2514/6.2008-4578 ◽

2008 ◽

Cited By ~ 4

Author(s):

Taira Tsuru ◽

Sadatake Tomioka ◽

Kenji Kudo ◽

Atsuo Murakami ◽

Kanenori Kato ◽

...

Keyword(s):

Skin Friction ◽

Supersonic Combustion ◽

Scramjet Combustor ◽

Friction Measurements

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The measurement of skin friction in turbulent boundary layers with adverse pressure gradients

Journal of Fluid Mechanics ◽

10.1017/s0022112069001418 ◽

1969 ◽

Vol 35 (4) ◽

pp. 737-757 ◽

Cited By ~ 52

Author(s):

K. C. Brown ◽

P. N. Joubert

Keyword(s):

Shear Stress ◽

Skin Friction ◽

Boundary Layers ◽

Three Dimensional ◽

Turbulent Boundary Layers ◽

Pressure Gradients ◽

Two Dimensional ◽

Direct Measurements ◽

Floating Element ◽

Dimensional Boundary

This paper describes a floating-element skin friction meter which has been designed for use in adverse pressure gradients. The effects of secondary forces on the element, which arise from the pressure gradient, are examined in some detail. The limitations of various methods of measuring wall shear stress are discussed and the results from the floating element device are compared with measurements taken in a two-dimensional boundary layer using Preston tubes and velocity profiles. As it is planned to use the instrument later for direct measurements of the shear stress in three-dimensional boundary layers, the relevance of the instrument to this situation is also discussed.

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