RU2820363C1 - Flat diffuser - Google Patents

Abstract

FIELD: pneumohydraulic systems of general purpose.

SUBSTANCE: invention relates to pneumatic-hydraulic systems of general purpose, in particular to methods and means of action on boundary layer of fluid medium flow in channels. Flat diffuser comprises four inner surfaces forming walls, two of which 1 and 2 are flat and parallel to each other, two other 3 and 4 are perpendicular to the first two and diverge in the direction from inlet 5 of the cross section to outlet 6, at least one hollow, dynamically balanced cylinder 7 with closed ends, located behind the inlet straight section 8 tangentially at the level of the inner surface of the wall and installed between parallel walls on central axis in supports 9 and 10 located in parallel walls 1 and 2, with possibility of rotation, and having length n of generatrix equal to distance N between inner surfaces of parallel walls 1 and 2 minus process gap s and diameter d, equal to not less than distance L between inner surfaces of outlet and inlet straight sections on corresponding of divergent walls 3 or 4.

EFFECT: reduced length of flat diffuser at acceptable losses of total pressure.

4 cl, 4 dwg

Description

The invention relates to general purpose pneumohydraulic systems, in particular to methods and means of influencing the boundary layer of fluid flow in channels.

A known diffuser of the exhaust tract of a gas pumping unit with a gas turbine unit contains a shell with flanges, a casing covering the shell and consisting of side panels, a roof and a tray, and sound insulation placed with a gap between the shell and the casing and secured to the shell using fasteners, for example pins , installed on the shell and passed through sound and thermal insulation, while the ends of the fastening elements, for example pins, do not have contact with the casing wall and are connected to each other by flexible elements (RU, No. 2313030, IPC F16L 59/00, F01D 25/30, publ. 20.12 .2007).

The known device refers to a rectilinear diffuser with a small expansion angle, which makes it quite long in length, which is a disadvantage, and is used in cases where there are no restrictions on overall dimensions.

A flat diffuser is known, chosen by the applicant as a prototype, containing four internal surfaces, two of which are flat and parallel to one another, the other two are perpendicular to the first two and diverge in the direction from the inlet section of the diffuser to the outlet, and the distance between the diverging ones increases along the diffuser according to the law, aimed at minimizing pressure losses (SU, No. 1695003, IPC F15D 1/04, published November 30, 1991). Other laws for changing the curvature of the diffuser profile generatrix are also known (Povkh I.L. Aerodynamic experiment in mechanical engineering, Leningrad, “Machine Building”, 1974, pp. 112-115).

The known diffuser is an isogradient diffuser, which is quite effective in terms of total pressure losses and provides a uniform velocity field at the outlet. However, despite the improvement in gas-dynamic characteristics, the known diffuser also has a significant length, which is a disadvantage.

The proposed invention solves the problem of reducing the length of a flat diffuser with acceptable total pressure losses.

To achieve this technical result, a flat diffuser containing four internal surfaces forming walls, two of which are flat and parallel to one another, the other two are perpendicular to the first two and diverge in the direction from the inlet cross-section to the outlet, is additionally equipped with at least one hollow, dynamic a balanced cylinder with closed ends, located behind the inlet straight section along a tangent at the level of the inner surface of the wall and installed between the parallel walls on the central axis in supports located in the parallel walls, with the possibility of rotation and having a generatrix length equal to the distance between the inner surfaces of the parallel walls behind minus the technological gap and a diameter equal to no less than the distance between the internal surfaces of the outlet and inlet straight sections on the corresponding of the diverging walls.

At the exit from the inlet section, a chamfer is made on the inner surface at an angle of 7...10°.

When located on opposite walls, the cylinders are mutually spaced along the length of the flow path along the flow at a distance of at least one quarter of the diameter.

The cylinder is made of composite materials.

In terms of features, the proposed flat diffuser differs from the prototype in that it is additionally equipped with at least one hollow, dynamically balanced cylinder with closed ends, located behind the inlet straight section tangentially at the level of the inner surface of the wall and installed between parallel walls on the central axis in supports located in parallel walls, with the possibility of rotation and having a generatrix length equal to the distance between the internal surfaces of the parallel walls minus the technological gap and a diameter equal to not less than the distance between the internal surfaces of the outlet and inlet straight sections on the corresponding of the diverging walls.

At the exit from the inlet section, a chamfer is made on the inner surface at an angle of 7...10°.

When located on opposite walls, the cylinders are mutually spaced along the length of the flow path along the flow at a distance of at least one quarter of the diameter.

The cylinder is made of composite materials.

Thanks to the presence of these features, it is possible to influence the boundary layer to continuously expand the flow over a short distance and thereby reduce the total length of the flat diffuser.

In fig. 1 shows a longitudinal section of a flat diffuser with one cylinder; in fig. 2 - longitudinal section of a flat diffuser with two cylinders; in fig. 3 - section along section A-A of Fig. 2; in fig. Figure 4 shows a longitudinal section of a flat diffuser with one cylinder of increased diameter.

In fig. The following notations are accepted:

d - cylinder diameter;

L is the distance between the internal surfaces of the outlet and inlet straight sections on the corresponding of the diverging walls;

n is the length of the cylinder generatrix;

N is the distance between the inner surfaces of parallel walls;

s - technological gap;

k is the distance of mutual placement of the cylinders along the length of the flow path.

The flat diffuser contains four internal surfaces forming walls, two of which 1 and 2 are flat and parallel to one another, the other two 3 and 4 are perpendicular to the first two and diverge in the direction from the inlet 5 cross-section to the outlet 6, at least one is hollow, dynamically balanced cylinder 7 with closed ends, located behind the inlet straight section 8 tangentially at the level of the inner surface of the wall and installed between parallel walls on the central axis in supports 9 and 10 located in parallel walls 1 and 2, with the possibility of rotation and having a length n a generatrix equal to the distance N between the internal surfaces of parallel walls 1 and 2 minus the technological gap s and a diameter d equal to at least the distance L between the internal surfaces of the outlet and inlet straight sections on the corresponding of the diverging walls 3 or 4.

At the exit from the inlet section 8, a chamfer is made on the inner surface at an angle of 7...10°.

When located on opposite walls 3 and 4, the cylinders are mutually spaced along the length of the flow path along the flow by a distance k, which is at least one quarter of the diameter d.

Cylinder 7 is made of composite materials.

A flat diffuser works as follows.

The working fluid through the inlet section 5 enters the flow part of the diffuser and, as it moves towards the outlet section 6, the kinetic energy of the flow is converted into potential energy of pressure. Flowing around cylinder 7, due to continuity, the active flow entrains (“tows”) the boundary layer, as well as the film of the working fluid, which is motionless relative to the surface of the cylinder, imparting a linear speed at the point of contact, which leads to the angular velocity of rotation of the cylinder. In turn, due to the Coanda effect, the rotating cylinder 7 attracts the flow to its outer surface, ensuring continuous expansion of the working fluid. Making the cylinder 7 hollow facilitates the design, which, together with dynamic balancing in addition to conventional static balancing, ensures ease of rotation and improves the operating conditions of the diffuser when the flow speed in the flow part of the inlet section 8 changes.

At the exit from the inlet section on the inner surface of the wall 3 in the chamfer zone at an angle of 7...10°, a decrease in speed occurs, respectively, a local increase in pressure, followed by an acceleration of the flow when flowing around the cylinder 7, which together improves the conditions for the spin-up of the latter.

To improve the conditions for expansion of the working fluid, it is advisable for the cylinders 7 located on opposite walls to be mutually spaced along the length of the flow path along the flow by a distance k, which is at least one quarter of the diameter d.

The manufacture of cylinder 7 from composite materials also facilitates the design and, as a result, improves the conditions for responding to changes in flow velocity under variable operating conditions of the system, which includes a flat diffuser.

In the absence of restrictions on the width (height) of the diffuser, it is possible to increase the diameter d (Fig. 4), which ensures a more uniform flow of the working fluid through the outlet section 6.

The implementation of the set of features described in the proposed device makes it possible to reduce the length of the flat diffuser with acceptable total pressure losses. The invention can find application in flat inlet devices of aircraft, in exhaust ducts of stationary gas turbine units, in exhaust energy recovery systems at test stations of aircraft gas turbine engines and in other systems that convert the kinetic energy of gas into pressure energy.

Claims (4)

1. A flat diffuser containing four internal surfaces forming walls, two of which are flat and parallel to one another, the other two are perpendicular to the first two and diverge in the direction from the inlet cross-section to the outlet, characterized in that it is additionally equipped with at least one hollow, a dynamically balanced cylinder with closed ends, located behind the inlet straight section tangentially at the level of the inner surface of the wall and installed between the parallel walls on the central axis in supports located in the parallel walls, with the possibility of rotation, and having a generatrix length equal to the distance between the inner surfaces of the parallel walls minus the technological gap and a diameter equal to not less than the distance between the internal surfaces of the outlet and inlet straight sections on the corresponding of the diverging walls. 2. A flat diffuser according to claim 1, characterized in that at the exit from the inlet section, a chamfer is made on the inner surface at an angle of 7...10°. 3. A flat diffuser according to claim 1 or 2, characterized in that when located on opposite walls, the cylinders are mutually spaced along the length of the flow path along the flow by a distance of at least one quarter of the diameter. 4. Flat diffuser according to claim 1, characterized in that the cylinder is made of composite materials.