Browsing by Author "Chadwick, Kenneth Michael"
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- An actively cooled floating element skin friction balance for direct measurement in high enthalpy supersonic flowsChadwick, Kenneth Michael (Virginia Tech, 1992-12-14)An investigation was conducted to design instruments to directly measure skin friction along the chamber walls of supersonic combustor models. Measurements were made in a combustor at the General Applied Science Laboratory (GASL) and in the Direct Connect Arcjet Facility (DCAF) supersonic combustor at the NASA AMES Research Center. Flow conditions in the high enthalpy combustor models ranged from total pressures of 275-800 psia (1900-5550 kPa) and total temperatures from 5800-8400 R (3222-4667 K). This gives enthalpies in the range of 1700-3300 BTU/Ibm (3950-7660 KJ/kg) and simulated flight Mach number from 9 to 13. A direct force measurement device was used to measure the small tangential shear force resulting from the flow passing over a non-intrusive floating element. The floating head is mounted to a stiff cantilever beam arrangement with deflection due to the shear force on the order of 0.0005 in (0.0125 mm). This small deflection allows the balance to be a non-nulling type. Several measurements were conducted in cold supersonic flows to verify the concept and establish accuracy and repeatability. This balance design includes actively controlled cooling of the floating sensor head temperature through an internal cooling system to eliminate nonuniform temperature effects between the head and the surrounding chamber wall. This enabled the device to be suitable for shear force measurement in very hot flows. The key to this device is the use of a quartz tube cantilever with strain gages bonded at orthogonal positions directly on the surface at the base. A symmetric fluid flow was developed inside the quartz tube to provide cooling to the backside of the floating head. Bench tests showed that this did not influence the force measurement. Numerical heat transfer calculations were conducted for design feasibility and analysis, and to determine the effectiveness of the active cooling of the floating head. Analysis of the measurement uncertainty in cold supersonic flow tests show that uncertainty under 8% is achievable, but variations in the balance cooling during a particular test raised uncertainty up to 20% in these very hot flows during the early tests. Improvements to the strain gages and balance cooling reduced uncertainty for the later tests to under 15%.
- An experimental investigation of the breakup of a viscoelastic non-newtonian fluid in a supersonic streamChadwick, Kenneth Michael (Virginia Tech, 1990-10-04)A basic experimental study of the aerodynamic breakup of a viscoelastic non-Newtonian liquid injected into a supersonic stream was conducted. All test runs were made either at a free stream Mach number of 2.4 and a total pressure of 4.1 atm or a Mach number of 4.0 and a total pressure of 10.9 atm. The air flow had a total temperature of 300 K, and the injectant was always at room temperature. The injectant used for the majority of the test runs was diethylmalonate thickened with polymethyl-methacrylate, which has the characteristics of being viscoelastic. A limited number of test runs were made with glycerin in order to make a comparison between the behavior of Newtonian and viscoelastic non-Newtonian fluids. Several areas concerning the disintegration of the viscoelastic non-Newtonian fluid were investigated, including the effects of free stream Mach number, injection velocity, jet diameter, twin in-line jets, injection angle, and injector shape. Spark Shadowgraphs of 1.2 microsecond duration and high speed movies were obtained to qualitatively appraise the breakup behavior. The breakup of the jet was found to be a function of free stream Mach number and jet diameter, injection angle, and frontal area. It also was observed that the breakup behavior of the viscoelastic non-Newtonian fluid is remarkably different from that of (Newtonian) glycerin. The time scales for breakup are substantially increased regarding the dissemination of the viscoelastic liquid as compared to the Newtonian glycerin. Furthermore, penetration of the viscoelastic non-Newtonian fluid was observed to be on the order of 50% less than that measured for glycerin at comparable injection conditions.