US3863678A

US3863678A - Pipe grating structure

Info

Publication number: US3863678A
Application number: US372022A
Authority: US
Inventors: Birger Pettersson; Bo Sangfors
Original assignee: Svenska Rotor Maskiner AB
Current assignee: Svenska Rotor Maskiner AB
Priority date: 1972-08-11
Filing date: 1973-06-21
Publication date: 1975-02-04
Anticipated expiration: 1992-02-04
Also published as: JPS4985619A; GB1442329A; IT989440B; DE2340483A1

Abstract

Grating structure disposed within a gas flow channel and comprising a disc-like member provided with passages therethrough. The passages are arranged in parallel rows and the outlets of the passages in adjacent rows are inclined in opposite directions relative to the main direction of the gas flow.

Description

[ Feb.4, 1975 United States Patent 1191 Pettersson et al.

[ PIPE GRATING STRUCTURE 1,113,041 10/1914 138/37 x [75] Inventors: Birger Pettersson, Alta; Bo Sangiors, 3682'443 8/1972 Upme'er [38/37 x Ektorp, both of Sweden FOREIGN PATENTS OR APPLICATIONS [73] Assignee: Svenska Rotor Maskiner Aktiebolag, 883 989 2/1961 Great Bmain [38/37 Nacka Sweden June 21, I973 [22] Filed:

Primary Examiner-Jerry W. Myracle 211 App]. No.: 372,022

Attorney, Agent, or Firm-Flynn & Frishauf [30] Foreign Application Priority Data ABSTRACT Aug. l l, I972 Great Britain 37557/72 [52] U.S. 138/37 Grating tructure disposed within a gas flow channel Int. and cgmprising a discJike member provided with pas. Field of 3/ 8 sages therethrough. The passages are arranged in par- 239/461; 259/DlG- l allel rows and the outlets of the passages in adjacent rows are inclined in opposite directions relative to the main direction of the gas flow.

References Cited UNITED STATES PATENTS 1,012,380 Loose....WM.................... 48/180 M 6 Claims, 4 Drawing Figures PATENTEU FEB 4|975 SHEET 2 0F 2 1 PIPE GRATING STRUCTURE The invention relates to a grating structure intended to be inserted in a conduit in order to homogenize a fluid flow passing through the conduit.

It is a known fact that, particularly in a conduit having a large cross-sectional area, the flow may be very non-uniform in several respects such as its velocity, temperature and composition. These irregularities may cause trouble and problems as, for instance, in rotary regenerative air preheaters where the uneven velocity distribution of the hot gas flow may result in uneven heating of the matrix of the preheater. It has also been determined that uniform velocity distribution over the cross-sectional area of the gas duct results in minimum pressure drop across the matrix. Further, a certain amount of flue gases normally escapes into the air flow and this gas may sometimes form a separate stream within the air flow and disturb the combination in one or more burners when reaching the boiler. Also within other technical fields it is desirable to maintain a homogeneous state of a gas or liquid flow.

SUMMARY OF THE INVENTION According to the invention a grating structure for the above mentioned purpose comprises a disc-like member traversed by passages extending between opposite faces of the disc and being arranged in parallel rows, the outlets of the passages of adjacent rows being inclined in opposite directions relative to the main direction of fluid flow through the disc. Such a grating subdivides the fluid flow in a conduit into a plurality of jets which cross one another so that whirls are created over the entire cross-sectional area of the conduit downstream of the grating.

These whirls break up the separate streams, if any, and cause fluid particles to move also in transverse directions resulting in a thorough stirring and homogenizing of the fluid flow within a region downstream of the grating.

The invention will be described more in detail with reference to the accompanying drawings in which:

FIG. I is a part-sectional side view of part of a rotary regenerative air preheater;

FIG. 2 is a section along line Il-ll of FIG. I drawn on a somewhat larger scale;

FIG. 3 is a perspective exploded view illustrating the manner of assembling the components of a grating structure shown in FIGS. I and 2; and

FIG. 4 is a perspective view of a part of the grating structure.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS The air preheater diagrammatically illustrated in FIG. 1 may be of the conventional Ljungstrom type comprising a rotatable matrix surrounded by a substantially cylindrical housing which is provided with connections I2 for inlet and outlet conduits for the heat exchanging fluids. In FIG. 1 only one such conduit is shown which is indicated by numeral I4 and will be assumed to be the hot gas supply conduit. As shown in FIG. 2 the conduit I4 is segment-shaped in cross section.

At some distance above the housing 10 a grating structure 16 is disposed in the conduit I4. This grating structure has the form of a disc traversed by passages I8 extending between the opposite faces of the disc and being arranged in parallel rows. the outlets of the passages of adjacent rows being inclined in opposite directions relative to the main direction of fluid flow through the disc. The two different directions of the fluid jets leaving the outlets of the passages I8 are indicated by arrows below the disc I6 in FIG. I.

It is evident that the differently directed fluid jets will interfere with each other, thereby causing a strong tur bulence in the gas flow which promotes homogenization of the flow. The disc 16 is located at such a distance above the housing II) that the turbulence has substantially subsided before the gas flow reaches the matrix. Thus. when entering the matrix the gas flow is substantially perpendicular to the end surface of the matrix at all points.

The disc I6 is somewhat smaller but similar in shape to the cross-section of the conduit I4 so as to leave a gap 20 between the periphery of the disc and the conduit wall. This gap prevents blocking of passages 18 located at the periphery.

The grating or disc I6 may be supported in the conduit I4 in any suitable manner, for instance by means of brackets, transverse rods or the like.

The grating I6 may be designed and produced in several different ways. In FIGS. 3 and 4 is illustrated one form of grating which is simple and inexpensive.

According to FIG. 3 the grating is composed of

bars

22 and 24 made from sheet material. The bars 22 are flat and provided with slits 26 extending from one edge at right angles to the length of the bar substantially over half the width thereof so that tongues 28 are formed be tween the slits.

The bars 24 are preferably produced by using bars similar to bars 22 and bending adjacent tongues 28A in different directions. The outlet angle of the passages relative to the main direction of fluid flow is of the order of l0 to 40.

When the two sets of

bars

22 and 24 are assembled there is obtained a grating structure as shown in FIG. 4.

If desired or necessary two or more gratings may be provided mutually longitudinally displaced in the conduit, each grating deflecting the fluid in directions other than those produced by the other.

We claim:

I. A grating structure adapted to be inserted in a conduit in order to homogenize a fluid flow passing therethrough, comprising a disc-like member traversed by passages which are arranged in parallel rows and which extend between the opposite major surfaces of the disc, the passages being curved and having inlet portions extending in a direction substantially parallel with the main direction of fluid flow over a distance which is substantial relative to the overall thickness of the disclike member and having outlet portions communicating with respective inlet portions, the outlet portions of the passages of adjacent rows being inclined in opposite directions relative to the main direction of fluid flow through the disc.

2. A grating structure as defined in claim I in which the passages are of substantially rectangular crosssection.

3. A grating structure as defined in claim 2, in which the passages are of substantially square cross-section.

6. A grating structure as defined in claim I wherein said disc-like member is smaller but similar in shape to the cross-section of the conduit in which it is adapted to be inserted so as to provide a gap between the periphery of the disc-like member and the conduit wall. t i l

Claims

1. A grating structure adapted to be inserted in a conduit in order to homogenize a fluid flow passing therethrough, comprising a disc-like member traversed by passages which are arranged in parallel rows and which extend between the opposite major surfaces of the disc, the passages being curved and having inlet portions extending in a direction substantially parallel with the main direction of fluid flow over a distance which is substantial relative to the overall thickness of the disc-like member and having outlet portions communicating with respective inlet portions, the outlet portions of the passages of adjacent rows being inclined in opposite directions relative to the main direction of fluid flow through the disc.

2. A grating structure as defined in claim 1 in which the passages are of substantially rectangular cross-section.

4. A grating structure as defined in claim 1 in which the outlet angle of the passages relative to the main direction of fluid flow is of the order of 10* to 40*.

5. A grating structure as defined in claim 1 wherein said respective inlet and oulet portions of said passages are contiguous.

6. A grating structure as defined in claim 1 wherein said disc-like member is smaller but similar in shape to the cross-section of the conduit in which it is adapted to be inserted so as to provide a gap between the periphery of the disc-like member and the conduit wall.