Gas Ejector Research Articles

Pulsed holographic interferometry vs Schlieren photography.

A hologram, sometimes called a holographic interferogram, provides a fringe pattern revealing changes in optical path length that occur between exposures of a scene. The method is thus obviously applicable to gas flow analysis. Appearing to offer approximately the same sensitivity as schlieren techniques, it requires no tedious alignment. To afford a direct comparison of results obtainable with the two methods, the experiments described herein were conducted. Holographic as well as schlieren techniques were employed in measuring the density distribution of different twodimensional air flow patterns: one from a supersonic jet impinging on an inclined flat plate; the other from an ejector. Figure 1 diagrams the experimental setup used for making the interferograms. A ruby laser operating in a single axial and transverse mode served as the light source. Beamsplitter BS split the laser beam into a reference beam and an illumination beam that provided scene backlighting through diffusing glass D. Path length matching was not required since the laser operated in a single axial mode and had a coherence length greater than a meter. The test scene occupied an approximate 4X 4-in. area, whereas hologram plate dimensions were 4 X 5 in. The holographic interferogram of the supersonic jet (see photo, Fig. 2a) was made by first firing the laser under conditions of no air flow, then opening the flow control valve for the second laser shot. The holographic interferogram of the gas ejector, photographed in Fig. 3a, was obtained by taking the first laser shot with flow and the second with no flow. Because the fringe patterns of the interferogram are produced by air density changes that vary the optical path length in the test section between exposures, the effects of dirt, optically nonuniform windows, and other stationary distortions of optical path length tend to cancel out. Figure 3 shows the effect of dirt on test chamber windows. The dirt did not noticeably affect the hologram (Fig. 3a) but caused air flow boundaries in the schlieren photograph (Fig. 3b) to be obscured. Since the double-exposure technique is sensitive only to optical path length changes, there is no necessity

Design and Application of the Gas Jet Ejector On Marginal Gas Wells

Abstract This paper discusses the theory, design and application of gas jet ejectors for use on marginal gas wells. A high pressure gas well is used as a source of motive energy. Pressure energy is converted into kinetic energy through the special configurations of the nozzle and diffusor sections of the ejector. A method is given for the design of a gas jet ejector for natural gas applications. Thermal efficiency is inherently low due to the nature of the process; therefore, some kinetic energy is converted into heat which aids in the prevention of hydrates. The ejector offers a low-cost method of compression of natural gas in a field where motive energy is available. Proper design should prevent the formation of hydrates, without utilizing an additional source of heat, for moderate to high temperature flowing wells. Introduction An ejector is a device which converts pressure energy of a motive stream into kinetic energy, entrains a secondary stream and discharges the combined stream at an intermediate pressure. Ejectors have been in use for some time on other applications, particularly for steam and air service. Until the last few years, however, their use was limited for natural gas service-partially because of the limited amount of available thermodynamic data for natural gas. Gas wells with flowing pressures that approach the pipeline pressure have a tendency to load up with either the liquid condensate or water that they produce. By using an ejector, the wellhead flowing pressure can be effectively lowered, thereby increasing the velocity in the tubing and keeping the well unloaded. This critical velocity for entrainment of liquid in vertical tubing has been estimated to be between 5 and 10 ft/sec. A successful application of the ejector was made in offshore Louisiana with two gas wells on connecting platforms. One of the wells was marginal and would not flow continuously against separator pressure. With the aid of the ejector it was maintained on production without having to unload the well periodically to the atmosphere. In addition to providing a low pressure commingling header, the ejector discharged the combined stream at a lower temperature than would have been possible with an ordinary choke. Thus, the heat load on the glycol dehydration equipment was reduced. Principle of Operation The gas jet ejector works on the principle of entrainment. A high pressure motive gas stream is expanded through a converging-diverging nozzle into a suction chamber. The motive gas picks up a low pressure secondary stream by entrainment and compresses it to an intermediate discharge pressure. Two basic facts peculiar to gas behavior determine the operating principle of an ejector. In a converging section, gases entering at less than the speed of sound are accelerated in velocity and reduced in pressure. At entering velocities higher than the speed of sound, gases are reduced in velocity and increased in pressure. In a diverging section, gases entering at less than the speed of sound are reduced in velocity and increased in pressure. At entering velocities higher than the speed of sound, gases are increased in velocity and reduced in pressure. In Fig. 1, the velocity-pressure changes are depicted for a typical gas ejector. JPT P. 419ˆ

Gas Extractor and Ejector for Gas Chromatography Samuel Natelson (to Scientific Industries, Inc., Springfield, Mass.) U.S. Pat. 3,171,722 (March 2, 1965)

Gas Extractor and Ejector for Gas Chromatography Samuel Natelson (to Scientific Industries, Inc., Springfield, Mass.) U.S. Pat. 3,171,722 (March 2, 1965)

Some Problems in the Design and Operation of Jet Ejectors

The author presents some of the more recent ejector design theories and compares them with experimental data, and he describes the operation of a few different types of ejector used at present in industry. He also gives a short survey of the relevant literature. The design theory developed in the first part of the paper is based on the momentum exchange between motive and suction fluid and the assumption that entrainment occurs at constant pressure and mixing at constant area. The equations in which the use of experimental coefficients is kept to a minimum give the motive-to-suction mass-flow ratio in terms of the pressure ratio and certain velocity ratios, as well as the required entry and mixing tube lengths and profiles. Optimization of the ejector for fixed pressure levels enabled the best ejector geometry to be determined with regard to nozzle position, mixing tube entry profile, and mixing tube length. The nozzle was in its optimum position when it reached up to the mixing tube. For this condition the optimum mixing tube length was seven tube diameters and the entry profile did not affect the operation. Although the theory is developed in more detail for an ejector using liquids the methods necessary for calculating gas ejectors and multi-phase and multi-component ejectors are outlined. The operating characteristics given in the second part of the paper emphasize the limitations of the jet pump but it is pointed out that both efficiency and compression ratio can be improved by the use of multistage designs. A particular application for a turbine condenser is discussed.

Power from Geothermal Steam at the Geyser Power Plants

Geothermal steam power plant between Cloverdale and Calistoga in California will have 12,500 kw capacity; turbine generator will be installed at ground level; steam will be condensed in barometric condenser and noncondensable gases will be removed by steam jet gas ejectors; use of corrosion resistant alloy steels; plant will operate automatically unattended and with remote alarm.