RU2005254C1 - Method and device for reducing pressure pulsations in pipeline - Google Patents

Description

The invention relates to mechanical engineering and can be used in installations for various purposes, in particular in pipelines for transporting gas or oil products, in high pressure pipelines in power plants, in rocketry.

Known devices for smoothing the pulsations of the flow pressure in a pipeline are described (see auth. St. USSR No. 420849, class F 16 1.55 / 04 and apt.se. USSR No. 1262181, class F 16 L 55/04).

Of the known devices, the closest in technical essence is the device described in ed. St. USSR No. 420849. This device contains a bypass pipe, one end of which is equipped with a shut-off valve and is mounted with the possibility of movement in the cavity of the main pipeline. In this device, the pulsating flow from the pump enters the main and bypass pipelines, and then into the common collector,

The pulsating flow in the pipeline at low speeds can be represented by the equality

P (t) P0 + / ocV (t) + Јo (t) (1)

where P (t) is the total pressure in the pipeline at time t in front of the device;

P (o) is a constant pressure component; .

(t) is the variable pressure component of the laminar flow;

p is the density of the substance moving through the pipeline;

c is the speed of sound in the substance of the stream;

V (t) is the periodic β-function of the change in flow velocity;

T0 (t) is the variable component of the turbulent flow pressure.

According to (1), any periodic function satisfying the Dirichlet conditions (piecewise continuity, boundedness, and a finite number of extrema on a period) can be represented by the Fourier series in trigonometric functions

00

/ (t)) + / s 2 Ak cos x

if 1

x (2ttkf0t -Qk) for k 1.2.3 ....

(2)

Here, the periodic function of the change in the velocity of the substance of the flow is expressed as

by a reposition of harmonic vibrations of multiple frequencies: Uk 2 l kf0 with amplitudes Ak and initial phases Qk, S0 is a constant component of the velocity of the substance, and fo is the frequency of the fundamental harmonic.

At speeds close to the speed of sound in the flow material, the Doppler effect (2) must be taken into account. We assume that the fluctuations in the speed of matter propagate only along the flow, then we obtain

f f0c (c + v),

(3)

where f is the frequency of the fundamental harmonic of the oscillation of the velocity of the flow material, taking into account the influence of the Doppler effect;

and - time average flow velocity. Substituting the value (2) into equation (1) and the Doppler effect (3) is lost, we obtain

00 P (t) P0 + pcSo + / ocЈ Ak cosx

 .k 1

x (2arkf0ct / (c + v) -Qk) + Јo (t)

thirty

when k 1,2,3 ,,.

(4)

In the device described in ed. USSR No. 420849, the pressure amplitude of the turbulent component of the flow decreases by about a factor of approximately with equal diameters of the bypass and main pipelines. For simplicity of analysis of the change in the laminar component, we consider this device with an additional condition establishing the equality of the sum of the cross-sectional areas of the bypass and main pipelines with the cross-sectional area of the inlet pipeline. Then, in the bypass and main pipelines, the pressure amplitudes of the laminar component can be written as

with

Robb1 / Ak COS X OS

k 1

x (2 tf k f0 s t / (s + v) - Qk) - yn),

oo

Rmag. 1 pc Ј Ak COS X

k 1

x (2 Jtk f0c t / (c + v) - Qk)

at k-1,2.3 ... (5)

It should be noted that for the device under consideration, the maximum reduction in pulsations of the laminar component can be achieved only under the conditions that the diameters of the bypass and main pipelines are equal, and the length of the bypass pipe is longer than the length of the main pipeline by the value of Ah, equal to half the period or a multiple of it. e.g. 1.5 period, 2.5 period, etc. This is equivalent to the condition

(with n 1,3,5 ...,

(b)

where n is the phase shift of the fundamental harmonic during the passage of the flow along the first branch path. Wherein

LI n (c + v) / 2f0 for n - 1.3.5 ... (7)

As a result of the addition of the bypass and main flows, the odd harmonic components of the laminar flow are destroyed, all the even components with double amplitudes remain, i.e.

1

00

P2i (t) P0 + pcS0 + pc% 2A cos

k 2

(2 kf0ct / (c + v) .- Qi () + Јi. (T) for k 2,4.6 ... (8)

where Ј1 (t) is the turbulent component of the flow after the device described in Auth. USSR ISfe 420849. From this it can be seen that with this device it is impossible to destroy even harmonics in a pulsating flow.

The aim of the invention is to reduce the pulsations of the flow pressure in the pipeline, g

This goal is achieved by the fact that the initial flow of the working medium is divided into two flows of equal cross-sectional area, one of the flows is launched along a longer path, and then connected at a place where the oscillation amplitudes of the fundamental harmonic are opposite to each other, by the following actions, the resulting stream is again divided into two streams of equal cross-sectional area, one of the streams is launched along a longer path, and then the streams are connected at the place where the oscillation amplitudes of the second harmonic are out of phase with each other, before the first dawn leniem flows after the first and after the second working medium of a compound of the pipeline passes through the aerodynamic lattice.

A known device for implementing the method, the device comprises a section of the supply line with branching into two pipelines of equal diameter and different lengths, and then connecting them in the pipeline at a place where the amplitudes of the pressure fluctuations of the main harmonic of the working medium of the pipeline are out of phase with each other. To achieve the objectives of the invention, it is supplemented by a device containing a similar branching into two pipelines, but with their connection in a place where the amplitudes of the pressure fluctuations of the second harmonic are out of phase with each other, before the first branching of the pipelines, after the first and after their second connection, aerodynamic lattice.

The drawing shows the construction of a device for reducing pressure pulsations in a pipeline.

A method of reducing pressure pulsations in a pipeline is implemented in a device containing a section of the supply line 1, de-pipeline 2 and 3 of the same diameter but different lengths, a section of the intermediate line 4, two pipelines 5 and 6 of the same diameter but different length, the section of the discharge line 7, while pipelines 2 and 3 are connected at a place where the amplitudes of the pressure fluctuations of the main harmonic of the working medium of the pipeline are out of phase with each other, and pipelines 5 and b are connected at a place where the second harmonics are out of phase with each other. In addition, the device contains aerodynamic lattices 8, 9 and 10.

In the proposed device, using the first flow separation, the destruction of the odd harmonic components of the laminar flow (as described by formulas 1 to 9) is achieved, and with the help of the second, the even harmonic components are destroyed. For this, the length of the second bypass stream is chosen to be greater than the length of the main by an amount E) 2 equal to or a multiple of the period of the second harmonic. This is equivalent to the condition

yn-n for n 1,3,5 ...

(9)

where yn is the phase shift of the second harmonic by passing the stream along the second bypass path. Wherein

D12 p (s + K) / 4f% npH p 1,3.5 .... (10)

With the right choice of the length of each branch, the amplitude of the pressure fluctuations of the laminar component at the output of the device decreases to zero. Therefore, pressure pulsations in the discharge pipe can be written as

PZ (t) Po + pcS0 + | 2 (t), (11)

where | a (t) is the turbulent component of the stream after the proposed device.

In practice, pressure pulsations from a synchronous motor pump also propagate upstream. In this regard, the proposed device must be placed on both sides of the pump.

For pressure fluctuations propagating upstream, the Doppler effect is written as

G-foc / (c - v)

(12)

The change in the pressure of the laminar flow propagating against the flow will be equal to

00

P (t) PO + p C So + p C 2 Afc COS X

k - 1

x (2jrkf0ct / (c -u) -Qk) - + Јo (O

at k-1,2,3, ... (13)

The length of the first bypass stream will be greater than the length of the main one by the value of All, equal to half the period of the fundamental harmonic or a multiple thereof. This is equivalent to the condition

(fi pl for n 1,3,5, .., Moreover

(14)

L (T - n (s - r $ / 2f0 for n = 1,3,5, ... (15) In the intermediate flow, pressure fluctuations propagating against the flow are written in the form

oo

x (2jrkf0ct / (c -u) -Qk) + Јr (t) for k 2,4,6 .... (16)

The length of the second bypass stream will be greater than the length of the main one by the value of L12. equal to half the second harmonic period or a multiple of it. This is equivalent to the condition

UP PLG at p 1,3,5, ... (17)

Moreover, Al2 n (c-f) / 4f0npHn 1,3.5, ... (18)

The amplitude of the pressure fluctuations in the laminar component of the flow at the inlet of the device decreases to zero. The pulsation of the pressure at the inlet of the device can be written as follows:

PZ; (T) P0 + / 9cS0-fЈ2 (O where & (t) is the turbulent flow component at the input of the device.

The pressure amplitude of the turbulent component in the device as a result of a phase shift between flows decreases

about four times ..

the turbulent component decreases as it passes through the aerodynamic grilles.

When using the invention in rocket engines, the low-frequency fluctuations of the combustion of the fuel supplied to the combustion chamber are substantially reduced, and consequently the low-frequency instability of the combustion of the fuel is reduced, there is no need to significantly increase the pressure drop across the nozzles and to increase the combustion chamber, due to this type of instability. Due to the application of the invention in rocket engines, the likelihood of destruction of the combustion chamber due to the low frequency instability of fuel combustion is reduced.

P2i (t) Po -4- / os So + pc% 2Ak.cosx

k 2

(56) Copyright certificate of the USSR 50 4208049, cl. F 16K 55/04, 1970.

92005254 10

Claims (2)

The claims are influenced by aerodi; 1. A method of reducing pulsations of pressure grids, laziness in the pipeline, in which 2. A device for reducing pulsating. the total flow of the working pressure mediation in the pipeline, which is divided into two flows, equal in plane plane to the supply pipeline with branching of the cross section and different sections, two sections of the pipeline of equal diameter, followed by their connection to each other and of different lengths connected in a place corresponding to an antiphase amp-place corresponding to an antiphase of an amplitude of pressure fluctuations of a main rap lithium of a pressure harmonic of a laminar flow, monics of a laminar flow, characterized in that, for the purpose, above, characterized in that it is provided with friction reducing effectiveness th pulse aerodynamic gratings and secondary tions. after connection, the total flow by repeated branching into two sections is divided into two flows, equal along a flat pipe of equal diameter and a difference in cross-section and different lengths, connected in place, corresponding to the length, followed by their repeated joint antiphase amplitude amplitude in the place corresponding to the second-harmonic pressure oscillations of the second-harmonic phase of the amplitudes of the oscillations of the pressure of the single flow, while the aerodynamics of the second harmonic of the laminar flow, 2Q lattices are placed in front of each and before each by dividing and branching and after the second connection reconnecting the general flow of the pipeline.