Central Nozzle Research Articles

Bent Jets in Radio Quasars

How is energy transported out from the central engine in quasars and radio galaxies to the distant radio lobes? This problem has been around since the early discovery of classical double radio sources, and is still not answered in detail. The idea of relativistic beams was first suggested by Martin Rees as a means of transporting plasma out of the nucleus (Rees, 1971, Blandford and Rees, 1974). This idea gained support first from the discovery of hot spots in the radio lobes of these large classical double sources, and later by observations of the beams themselves in radio galaxies. As more jets were observed, it became obvious that they were often curved, serpentine, or even sharply bent. This behavior has been modeled as precession of the central nozzle (Bridle et al., 1976, Ekers et al., 1978), as nuclear refraction (Henriksen et al., 1981), as a growing plasma instability (Hardee, 1981) and as various combinations of the above. At the present time, it seems safest to conclude that there are some examples of each of these processes known.

Background of New Code Rules for Integral Flat Heads with a Large, Central Nozzle

Paragraph UG-39 (c) of ASME Section VIII, Division 1, 1980 Edition states: “Flat heads that have an opening with a diameter that exceeds one-half of the head diameter or shortest span, as defined in UG-34, shall be designed as a flange in accordance with the Rules for Bolted Flange Connections given in Appendix 2.” The application of Appendix 2 to such configurations is subject to various interpretations, accordingly, rules have been written for the specific case of a single, large central opening (nozzle) in integral flat heads. The new rules will appear in the Winter 1980 Addenda; for configurations not provided for the designer is referred to U-2 (g).

On the formation of shock waves in laval nozzles

Inviscid gas flows are investigated in the case when in plane and axisymmetric Laval nozzles a weak discontinuity propagates along the characteristic which reaches the nozzle center. Sufficient conditions of shock wave formation at the nozzle center, disclosed by the first correction of the continuous self-similar solution, are obtained.

Experimental Studies of a Radial Turbulent Jet : 5th Report, Attaching Jet Flow from an Inclined Nozzle on an Adjacent Offset Disc Plate

A study has been made of the attachment of a radial jet flow discharged from an inclined nozzle on an adjacent offset disc plate. Mean velocity, turbulent velocity and static pressure distributions were measured. The effects of the angle of inclined nozzle to the disc plate, and also of the distance of nozzle center from the offset plate on flow pattern were investigated. Length and average negative pressure in the region of recirculating flow were examined. The results were compared with those obtained for a two-dimensional attaching jet flow to an inclined flat plate. Changes of maximum jet center velocity and jet half width of the flows before and after an attaching point along the flow were measured, and the results were compared with those obtained for a radial free jet flow or a radial wall jet flow, respectively.

Asymptotic theory of the flow around an obstacle by a sonic flow

The first investigation of the problem of the flow around an obstacle by a gas flow whose velocity is equal to the speed of sound at infinity was carried out in [1, 2], where it is shown in particular that the principal term of the appropriate asymptotic expansion is a self-similar solution of Tricomi's equation, to which the problem reduces in the first approximation upon a hodographic investigation. The requirement that the stream function be analytic as a function of the hodographic variables on the limiting characteristic was an important condition determining the selection of the self-similarity exponent n (xy−n is an invariant of the self-similar solution). The analytic nature of the velocity field everywhere in the flow above the shock waves, which arise from necessity upon flow around an obstacle, follows from this condition. The latter was found in [3], where one of the branches of the solution obtained in [1] was used in the region behind the shock waves. The principal and subsequent terms of the asymptotic expansion describing a sonic flow far from an obstacle were discussed in [4], where the author restricted himself to Tricomi's equation. Each term of the series constructed in [4] contains an arbitrary coefficient (we will call it a shape parameter) which is not determined within the framework of a local investigation, and consideration of the problem of flow around a given obstacle as a whole is necessary in order to determine these shape parameters. It follows from the results of [4] that the problem of higher approximations to the solution of [1] coincides with the problem, of constructing a flow in the neighborhood of the center of a Laval nozzle with an analytic velocity distribution along the longitudinal axis (a Meyer-type flow). Along with the Meyer-type flow in the vicinity of the nozzle center, which corresponds to a self-similarity exponent n=2, two other types of flow are asymptotically possible with n=3 and 11, given in [5]. The appropriate solutions are written out in algebraic functions in [6]. The results of [5] show that the condition that the velocity vector be analytic on the limiting characteristic in the flow plane is broader than the condition that the stream function be analytic as a function of the hodographic variables, which is employed in [1, 2, 4]. Therefore, the necessity has arisen of reconsidering the problem of higher approximations for the obstacle solution of F. I. Frankl'. It has proved possible for the region in front of the shock waves to use a series which is more general than in [4], which implies the inclusion of an additional set of shape parameters. The solution is given in the hodograph plane in the form of the sum of two terms; the series discussed in [4] corresponds to the first one, and the series generated by the self-similar solution with n=3 or with n=11 corresponds to the second one.

Derivation of higher approximations in the problem of special flows in plane laval nozzles: PMM vol. 42, n≗2, 1978, pp. 289–295

The method of expansion in series in self-similar components is used for deriving solutions of gasdynamic equations for some off-design modes of flow in a plane nozzle, particularly in the case when local supersonic zones interlock at the nozzle axis (the Taylor limit flow). Analysis of expansions in self-similar solutions is carried out simultaneously in the stream and the hodograph planes. The first three terms of expansion are determined for the Taylor limit flow in a plane Laval nozzle. In that case the correction terms retain the property of double symmetry about the horizontal and vertical axes that pass through the nozzle center.

Small-signal gain measurements in a CW chemical laser

Measurements of the small-signal gain of the laser medium produced by a combustion-driven CW chemical laser are presented. The laser characterized is a conventional supersonic flow chemical laser. A low-power CW chemical probe laser operating on a single line and single TEM 00q mode was used for the measurements. Scans of the cavity in the streamwise direction were made by directing the probe beam through the cavity with a set of translating mirrors. We present a description of the probe laser, scanning mechanism, and signal processing system which gave good repeatability and excellent signal-to-noise performance. Streamwise scans of the laser cavity at two nozzle heights are presented. One of the scans was made at the nozzle center, and the other near the nozzle edge where free-jet expansion affects the gain medium. The measured gain profiles obtained at these two heights are compared and analyzed for several laser lines and several flow conditions. Finally, we analyze these data in terms of measured laser performance parameters.

Experimental Studies of a Radial Turbulent Jet : 4th Report, Flow at and after an Attaching Point of Attaching Jet Flow

A study has been made of a flow at and after an attaching point of a radial attaching jet flow on an adjacent offset disc plate. Mean velocity, turbulent velocity and static pressure distributions were measured. The effects of the diameter and width of nozzles, and also of the distance of nozzle center from an offset plate on flow pattern were investigated. A flow field has been divided into three regions : recirculating flow region formed near a nozzle outlet, transitional region where jet center velocity increases downward, and wall jet flow region where jet center velocity decreases with distance. Changes of jet center velocity, thickness of inner layer and jet half width in the wall jet flow region along the flow were measured, and it was found that these results agreed well with those for the radial wall jet flow.

Experimental Studies of a Radial Turbulent Jet : 3rd Report, Flow before an Attachment Point of Attaching Jet Flow

A study has been made of the attachment of a radial turbulent jet flow to an adjacent offset disc plate. Mean velocity and turbulence together with pressure distributions were measured, and the effects of diameter and width of nozzles, and also of distance of nozzle center plane from offset plate on flow pattern were investigated. Length and average negative pressure in the region of recirculating flow were examined. The results were compared with those obtained for two-dimensional attaching jet flow. An oil film flow visualizing technique was also applied to determination of the flow pattern, and the results were compared with those assumed from measured velocity and pressure distributions. Position of maximum value of maximum jet center velocity, and also agrees well with the position of jet attachment point obtained by the flow visualization.

The triple jet: A new method for measurement of extensional viscosity

Apparatus for the measurement of extensional viscosity of polymer solutions is described. The range of extensional strain rates is 100–800 sec−1. Two converging liquid jets of high velocity impinge on a central low-velocity jet, causing the liquid in the central jet to be rapidly stretched. The force causing extension of this jet is measured from the change in reaction on the central capillary nozzle, whilst the initial and final velocities are obtained by jet thrust and photographic methods respectively. The Instron system provides accurately-controlled liquid flowrates and continuous recording of the various forces involved. Tests are reported on polyacrylamide solutions of concentration 0.10% and 0.07%, and on poly (ethylene oxide) solutions of concentration 0.10%. The extensional viscosity of the more concentrated polyacrylamide solution is over 30 poise at an extensional strain rate of 600 sec−1, exceeding the shear viscosity by a factor of 400 (the “Trouton” ratio). For the poly (ethylene oxide) solution, theTrouton ratio reaches 1400 at an extensional strain rate of only 200 sec−1. The results are shown to be consistent with orifice jet thrust data for similar solutions at higher strain rates. The axial stress rises rapidly with increasing extensional strain rate, but there is no evidence of an abrupt increase of stress in the range of strain rates between 102 and 104 sec−1. The triple jet method is of value in giving data for intermediate extensional strain rates and being dependent on fewer assumptions than the orifice jet thrust experiment.

Temperature distribution of magnesium flames

Methods used in the past for calculating the radiation properties of flames with diffusing particles were employed in the investigation of oxygen/city gas flames containing magnesium oxide particles. In the first case oxygen was injected through the central nozzle, whereas in the second case the gas introduced through this nozzle was city gas. A common feature to all experiments was that magnesium has been supplied simultaneously through the central nozzle. Both types of flame differ with respect to their temperatures. These temperatures have been determined starting from measurements of both the colour temperature and luminance temperature. It was surprising to see that the temperature of the first type of flame showed a minimum at the centre of the flame. This minimum was not observed in the flame of the second type. The results are discussed, and information about the combustion process is offered.

Three-dimensional sub- and supersonic flows in nozzles and channels of varying cross section: PMM vol. 36, n≗2, 1972, pp.239–247

Three-dimensional sub- and supersonic flows of gas in nozzles and channels of varying cross section are analyzed. The inverse problem of the theory of Laval nozzles is formulated and extended to three-dimensional flows. An implicit threepoint difference scheme with varying pitch along a layer is proposed. In the neighborhood of the surface for which the Cauchy data are specified an asymptotic series expansion in terms of the stream-function is derived and the method of solving related equations is indicated. Examples of calculations of three-dimensional flows in nozzles are presented. Papers [1–3] dealing with three-dimensional supersonic flows in nozzles and paper [4] in which an analytical solution is derived for the flow in the neighborhood of the nozzle center should be noted among recent publications.

2次燃焼をともなうロケット噴炎の電波減衰特性について

This paper presents theoretical and experimental results for estimating electromagnetic wave attenuations caused by the presence of rocket exhaust plumes with afterburning in the propaga- tion medium between a ground station and a rocket-powered vehicle.The approximate distributions of the velocity, temperature and concentration of the rocketplume are obtained in the analytical forms by solving the boundary layer equations under some assumptions.The distributions of the rocket composite propellant are presented in graphical form. Wave propagation characteristics passing through a flame with the high collision frequency compared to the frequency used for flame diagnostics are discussed.The predicted and experimental wave attenuations along the nozzle center axis are compared with qualitatively good agseement.

Study of burning rate and nature of combustion in diesel engines

In the present investigation the burning rates in diesel engines have been studied in some detail and the rate-controlling factors examined. Chemical kinetics based on activated collision could not play a part because otherwise the whole process would be very temperature sensitive, and this is not consistent with results from experimental investigation. The temperature drop during the expansion stroke would demand a drop in burning rate far greater than is shown by experiment, while the proportional increase in burning rate with engine speed could not be accounted for by the small increase in cycle temperature. Indeed the major factors affecting the burning rate are injection rate, engine speed, and combustion chamber design, all of which directly affect mixing. For a D.I. engine with central multihole nozzle, it is found that a relationship exists between the rate of injection and rate of burning. This relationship is independent of operating condition and therefore can be used to predict the rate of burning, and hence the cylinder pressure diagram from the rate of injection diagram.