Showing papers on "Tip clearance published in 1978"
141 citations
TL;DR: In this article, a low-tip speed axial flow fan with eight equally spaced blades was tested in both free field and reverberant field environments and the fan backpressure and speed were varied during the tests.
101 citations
TL;DR: In this article, a row-by-row heat-transfer analysis of cylinders in a crossflow of air in a flat rectangular duct has been performed, where the cylinders were attached perpendicular to one of the principle walls of the duct, with a clearance space between the free ends of the cylinders and the other principle wall.
80 citations
01 Feb 1978
TL;DR: In this article, an in-place recalibration technique for rotor-blade-tip-tip clearance measurement systems was proposed to reduce the errors in a commercial system by more than 50 percent up to a temperature of 370 C (700 F).
Abstract: It is known that capacitance-sensing, rotor-blade-tip-clearance measurement systems suffer from a strong dependency on probe tip temperature and humidity. A novel in-place recalibration technique partly overcomes this problem through a simple modification of the electronics that permits a scale factor correction. The technique is used to reduce the errors in a commercial system by more than 50 percent up to a temperature of 370 C (700 F). A probe design is proposed to further raise the maximum temperature capability of the measurement system.
6 citations
01 Apr 1978
TL;DR: In this paper, the rotor blade tip clearance measurement system consists of a capacitance sensing probe with self contained tuning elements, a connecting coaxial cable, and remotely located electronics, and a novel inplace recalibration technique was presented which partly overcomes this problem through a simple modification of the electronics that permits a scale factor correction.
Abstract: The rotor blade tip clearance measurement system consists of a capacitance sensing probe with self contained tuning elements, a connecting coaxial cable, and remotely located electronics. Tests show that the accuracy of the system suffers from a strong dependence on probe tip temperature and humidity. A novel inplace recalibration technique was presented which partly overcomes this problem through a simple modification of the electronics that permits a scale factor correction. This technique, when applied to a commercial system significantly reduced errors under varying conditions of humidity and temperature. Equations were also found that characterize the important cable and probe design quantities.
4 citations
09 Apr 1978
TL;DR: In this paper, a technique for the detrmination of turbine rotor bade tip-to-stationary shroud clearance requirements utilizing fiber optics was presented for a 10,000-hp engine.
Abstract: In this paper, a technique is presented for the detrmination of turbine rotor bade tip-to-stationary shroud clearance requirements utilizing fiber optics. To accomplish these tip clearance determinations, special rub pins were installed in the turbine shrouds, or tip-shoes, of a 10,000-hp engine. A test procedure was created based upon a transient dimensional analysis, and a cooled borescope and camera were developed. The clearances are presented from a series of successive engine tests.Copyright © 1978 by ASME
2 citations
01 Jan 1978
TL;DR: In this article, a 0.4 linear scale version of the LF460 lift fan turbine with the rotor radial tip clearance reduced to about 2.5 percent of the rotor blade height was tested.
Abstract: Performance was obtained over a range of speeds and pressure ratios for a 0.4 linear scale version of the LF460 lift fan turbine with the rotor radial tip clearance reduced to about 2.5 percent of the rotor blade height. These tests covered a range of speeds from 60 to 140 percent of design equivalent speed and a range of scroll inlet total to diffuser exit static pressure ratios from 2.6 to 4.2. Results are presented in terms of equivalent mass flow, equivalent torque, equivalent specific work, and efficiency.
2 citations
09 Apr 1978
TL;DR: In this paper, the initial low temperature phase of a modest design and development exercise was described in which a 76mm-dia radial turbine rotor was operated at a speed of 1670 rev/sec (100,000 rpm).
Abstract: In sizes suitable for automotive gas turbines, the small radial turbine has component efficiency equal to that of the axial type, is less sensitive to the effects of tip clearance, and translates more readily into the ceramic medium with minimal aerodynamic compromise. The initial low temperature phase of a modest design and development exercise is described in which a 76-mm-dia radial turbine rotor was operated at a speed of 1670 rev/sec (100,000 rpm) and at temperature of 1000 K.Copyright © 1978 by ASME
2 citations
01 Mar 1978
TL;DR: In this paper, a laser-powered miniaturized turbine tip clearance device (MTCMD) was used to verify or improve the analytical techniques for turbine tip clearance design and prediction.
Abstract: : Turbine tip clearance design and prediction techniques have been limited to analytical methods for lack of an accurate direct measurement device. It was the purpose of this program to substantiate prediction correlations utilizing direct measurements from a laser-powered miniaturized turbine tip clearance device (MTCMD) previously developed under Applied Technology Laboratory support. The resultant comparisons of measured versus analytically determined clearances based on measured temperatures would be used to verify or to improve the analytical techniques.
2 citations
01 Jul 1978
TL;DR: In this article, an advanced electro-optical system was developed to measure single blade tip clearances and average blade tip clearance between a rotor and its gas path seal in an operating gas turbine engine.
Abstract: An advanced electro-optical system was developed to measure single blade tip clearances and average blade tip clearances between a rotor and its gas path seal in an operating gas turbine engine. This system is applicable to fan, compressor, and turbine blade tip clearance measurement requirements, and the system probe is particularly suitable for operation in the extreme turbine environment. A study of optical properties of blade tips was conducted to establish measurement system application limitations. A series of laboratory tests was conducted to determine the measurement system's operational performance characteristics and to demonstrate system capability under simulated operating gas turbine environmental conditions. Operational and environmental performance test data are presented.
1 citations
01 Feb 1978
TL;DR: In this paper, the advantages and limitations of each instrument and technique are discussed and the possibility of modifying them for use in developing various propulsion systems is suggested, as well as the possibility to use them for propulsion systems.
Abstract: Apparatus and techniques developed or used by NASA-Lewis to make steady state or dynamic measurements of gas temperature, pressure, and velocity and of the temperature, tip clearance, and vibration of the blades of high-speed fans or turbines are described. The advantages and limitations of each instrument and technique are discussed and the possibility of modifying them for use in developing various propulsion systems is suggested.