An Experimental Investigation of an Underexpanded Rectangular Jet Ejector PDF Download
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Author: Yeu-Chuan Hsia
Publisher:
ISBN:
Category : Air ducts
Languages : en
Pages : 216
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Book Description
An experimental investigation was carried out on a rectangular ejector (constant area mixing duct) with an underexpanded rectangular jet as primary flow. This study investigated the mixing behavior of the ejector flow in general and attempted to identify the effects of the screech tones on the mixing and performance of the ejector. The quantities measured include frequency and amplitude of the screech tone, surface pressure on the ejector duct wall, and the mean flow velocity at the ejector exit in the two central planes of the primary jet. Schlieren flow visualization was made in the plane containing the short dimension of the primary nozzle. The screech tone frequency of the ejector depends not only on the primary jet pressure ratio but also on the ejector duct width. Variations of the screech tone frequency with both the pressure ratio and the duct width show staging behavior. For a given duct width, each screech tone stage matches with one of the transverse modes of the duct. The ejector performance, as determined from the static pressure distribution on the walls, shows irregular variation with pressure ratio, and is found to be related to the screech tone stages.
Author: Yeu-Chuan Hsia
Publisher:
ISBN:
Category : Air ducts
Languages : en
Pages : 216
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Book Description
An experimental investigation was carried out on a rectangular ejector (constant area mixing duct) with an underexpanded rectangular jet as primary flow. This study investigated the mixing behavior of the ejector flow in general and attempted to identify the effects of the screech tones on the mixing and performance of the ejector. The quantities measured include frequency and amplitude of the screech tone, surface pressure on the ejector duct wall, and the mean flow velocity at the ejector exit in the two central planes of the primary jet. Schlieren flow visualization was made in the plane containing the short dimension of the primary nozzle. The screech tone frequency of the ejector depends not only on the primary jet pressure ratio but also on the ejector duct width. Variations of the screech tone frequency with both the pressure ratio and the duct width show staging behavior. For a given duct width, each screech tone stage matches with one of the transverse modes of the duct. The ejector performance, as determined from the static pressure distribution on the walls, shows irregular variation with pressure ratio, and is found to be related to the screech tone stages.
Author: Hidayat Wiradimadja
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
An ejector is basically a jet pump in which the kinetic energy of the jet is made to impart motion to the fluid surrounding it. During this process, in a well design system, the ejector as a whole experiences a thrust much higher than that of the jet alone. In principle, an ejector is nothing but a jet surrounded by a shroud. This investigation concerns the performance of a two- dimensional ejector with its primary jet excited by a novel method. A constant area duct was used in this experiment. The velocity of the jet at the exit was subsonic. Maximum thrust was obtained when the ejector to jet exit area ratio was about 35. Under this condition a thrust augmentation ratio of 1.65 was achieved, with the jet excited at 20 Hz, whereas without excitation it was only 1.40. The mixing characteristics of the jet under excitation was examined using flow visualization techniques. Smoke filaments illuminated by a sheet of powerful light and schlieren optics with the jet heated were used. Excitation of the jet was found to generate large vortex-like flow structures which might be responsible for enhanced mixing. These vortices extended to considerable distances on both sides of the jet.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1134
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Author: Eugene J. Manganiello
Publisher:
ISBN:
Category : Jet engines
Languages : en
Pages : 19
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Book Description
An experimental investigation of rectangular exhaust-gas ejector pumps was conducted to provide data that would serve as a guide to the design of ejector applications for aircraft engines with marginal cooling. The pumping characteristics of rectangular ejectors actuated by the exhaust of a single-cylinder aircraft engine were determined for a range of mixing-section area from 20 to 50 square inches, over-all length from 12 to 42 inches, aspect ration from 1 to 5, diffusing exit area from 20 to 81 square inches, and aspect ratio of exhaust nozzle from 1 to 42. A few tests were conducted with a multistage ejector, a divided ejector, and an ejector incorporating bends along its length.
Author: Shigeki Aoki
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: A. Krothapalli
Publisher:
ISBN:
Category :
Languages : en
Pages : 28
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Book Description
An experimental investigation was carried out to study the mixing characteristics of a moderate aspect ratio rectangular free and confined jet; and free and confined multiple jet. The main parameters were the primary jet pressure ratio (stagnation pressure/ambient pressure) and the ejector mixing duct to width ratio. The pressure ratio varied from 1.5 to 5; the mixing duct to width ratio varied from 8 to 24, which is equivalent to the cross sectional area ratio from 11 to 34. It is found that an underexpanded jet inside a duct generates intense discrete tones (screech tones) similar to a free underexpanded jet. For a given pressure ratio, the variation of the dominant tone with duct widths shows staging behavior, and the frequency varies continuously with duct width in each stage. Similarly, for a given duct width, the variation of the dominant discrete frequency with pressure ratio shows staging behavior. It is found that enhanced mixing and improved performance of the ejector was related to the strouhal number of the ejector screech tone. For all the duct widths tested, it is found that when the screech tone strouhal number lies within the range 0.1 0.15, the primary jet spreading is increased and the ejector flow is better mixed at the exit.
Author: Yu N. Vasilev
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
An experimental study was made of a three-jet gas ejector in an attempt to improve ejector efficiency. The three-jet ejector consists of a converging nozzle for the high pressure gas and an annular nozzle for the low-pressure gas, and is similar to a conventional ejector; it is, however, also equipped with a tube in the center of the converging nozzle through which part of the low-pressure gas is introduced. Plots were obtained for the dependence of the compression ratio on the pressure drop in the forechamber, at various positions of the central tube, and with the converging nozzles having diameter ratios of 0.55, 0.45, and 0.35. The results showed that a compression ratio of 31 and a pressure drop of 240 can be obtained in the three-jet ejector when the outlet of the central tube is located in the minimum pressure zone. This compares very favorably with the 5.6 and 42.5 values obtained in a conventional ejector. By using a start-up control in which the central tube outlet is gradually moved into the minimum pressure zone, a compression ratio of 44 and a pressure drop of 340 can be obtained. The overall results indicate that the operation of a conventional ejector can be substantially improved by installing a central tube for the low-pressure gas. (Author).
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 524
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Book Description
A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA).
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 654
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 554
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