RU4568U1 - PNEUMATIC DYNAMIC CORRECTOR - Google Patents

Abstract

1. A pneumatic dynamic corrector comprising an inter-throttle chamber formed by a series-connected inlet throttle, a pneumatic capacity and an output throttle, characterized in that a thermal capacity is introduced into the inter-throttle chamber. 2. The corrector according to claim 1, characterized in that the thermal capacity is made in the form of a pipeline. The corrector according to claim 2, characterized in that the pipeline is made with a length of more than 10 calibres. The corrector according to claim 1, characterized in that the thermal capacity is made in the form of a package of pipelines, for example two, coaxially arranged. The corrector according to claims 2 to 4, characterized in that the inlet to the pipeline and the exit from the inlet throttle are made as a jet ejector. 6. The corrector according to claims 2 to 5, characterized in that the exit from the pipeline and the entrance to the output choke are made as a jet ejector. 7. The corrector according to claims 2 to 6, characterized in that an additional throttle, for example a diaphragm or a Laval nozzle, is installed in the pipeline. The corrector according to claims 1 to 7, characterized in that the input throttle is made in the form of a Laval nozzle with an output section area larger than the narrow section area of the output throttle. 9. The corrector according to claims 1 to 8, characterized in that the thermal capacity is insulated from the walls of the inter-throttle chamber.

Description

Pneumatic dynamic corrector

The claimed device relates to pneumatic automation, and can be used in automatic control systems (ATS) of a gas turbine engine for dynamic correction of a pneumatic signal.

Known pneumatic inkjet device for issuing a sequence of commands, see Copyright certificate N 263266, class. G 06g, 1970 G, which can be used for dynamic correction of the pneumatic signal. The device comprises a generator, a system of counting triggers, a digital-to-analog converter. The essence of the operation of such a device is that a system of serially connected triggers counts the periods of the pneumatic signal set by the jet generator, and issues a sequence of commands to the input of the digital-analogue converter, which provides the pneumatic signal correction in time. Such a device is difficult to constructively.

The closest in technical essence to the claimed one, is a device for providing the necessary dynamic qualities of the transient response, see patent SNM N3587602, class G15s1 / 14, containing inlet throttle, pneumatic capacity and output throttle in series. The disadvantage of such a device, while ensuring a constant delay time of several seconds, is either low reliability due to the use of a small-sized capacitance with small orifice inductors, or large capacitance dimensions.

The objective of the claimed device is the creation of a dynamic corrector for the ATS GTE simple in design and having small dimensions and mass, providing dynamic correction of the pneumatic signal with a time constant of several seconds.

The task is achieved by the fact that a thermal capacitance is introduced into the inter-throttle chamber of the pneumatic dynamic corrector (MPC) formed by the inlet throttle, pneumatic capacity, and output choke connected in series. The thermal capacity can be structurally performed in

MKL F15C1 / 14

inside a massive body, or in the form of a thin-walled shell.

The thermal capacity can be insulated from the walls of the inter-throttle chamber.

Thermal capacity can be made in the form of a pipeline, eg thin-walled.

The pipeline can be made with a length of 10 or more calibers.

The pipeline installed between the input and output chokes can be made in the form of a package of pipelines, for example two, coaxially arranged.

The entrance to the pipeline installed in the pneumatic container, and the exit from the input throttle can be made in the form of a jet ejector.

The output from the pipeline installed in the pneumatic tank, and the input of the input choke can be made in the form of a jet ejector.

A throttle type diaphragm or Laval nozzle can be installed in the pipeline.

The input choke of the ShchK can be made in the form of a Laval nozzle with an output cross-sectional area greater than the area of the narrow section of the output choke.

The proposed utility model is illustrated by drawings, where: in Fig.1 shows a pneumatic dynamic corrector; Fig.2-3 - options for its execution; Fig.4 presents the change in pressure in the inter-throttle chamber at maximum permissible pressure, "$ 1 | in | 1 pressure and temperature at the inlet to the device.

The dynamic corrector contains: a serially connected input choke 1, a pneumatic tank 2 and an output choke 3, forming an inter-throttle chamber (G), into which a thermal tank 4 is introduced, made thin-walled, for example, in the form of a pipeline located between the inlet choke 1 and the output choke 3 in the pneumatic container 2 (see figure 2). An additional choke 5 is installed in the pipeline of the heat capacity 4 and a channel 6 for selecting an information signal with

 %

the entrance to the inductor 3 (see Fig. 3). The optimum length of the pipeline is 4 10-30 calibres. Thermal tank 4 can be made in the form of a package of pipelines, for example, two, coaxially arranged. The exit from the throttle 1 and the entrance to the pipeline can be made in the form of a jet ejector. The exit from the pipeline and the entrance to the throttle 3 can also be performed as a jet ejector. The throttle 5 may be made in the form of a Laval nozzle or diaphragm. The output throttle 3 can also be made in the form of a Laval nozzle with an output cross-sectional area greater than the narrow sectional area of the output throttle.

In the graph of FIG. Figure 4 shows the process of changing the pressure in the liquid crystal with a stepwise change in pressure 8 and the air temperature at the inlet to the MPC (pressure and air temperature behind the compressor).

The device operates as follows. In the steady state, air enters the MPC tank 2 through the inlet choke 1, exits through the output choke 3. The output signal can be taken through channel 5 (in the form of pressure), or through dross, 3 in the form of flow rate).

With a simultaneous change in pressure and temperature at the inlet of the MPC (which occurs when the air (gas) is compressed in the compressor), for the costs through the inlet and outlet chokes, with a small volume of pneumatic capacity, according to the law of conservation of mass, we have:

GBX bvy (1), where

GBX - air flow through the inlet throttle, kg / s; bvykh-air flow through the output choke, kg / s.

At critical flow regimes in throttles (when the pressure ratio on the throttles is more than critical), we have:

Pvkh GvkhM / | / TVh Rvyh Gvyh «gA / 1 / Thy (2), where

FBX - cross-sectional area of the input choke, m2;

A - coefficient taking into account the air flow through

throttle, as well as features of its geometry; Tvh - air temperature at the entrance to the MPC, K; Pv1yah - absolute air pressure at the outlet in the inter-throttle

chamber (MK) MPC, Pa;

Rvykh- sectional area of the output choke, m2; Tvikh is the temperature of the air at the inlet to the output throttle CCC, K,

From equation (2) it follows that the pressure in the MPC inter-throttle chamber, under other constant conditions, depends on the air temperature:

Throwing Yours. (3)

When changing the operation mode of a gas turbine engine, the degree of increase in air pressure behind the compressor and the temperature change:

Tk / (Pk ((K-1) / K) -1) const (4), where

Tk - temperature behind compressor K;

Pk-Rk / Rn - absolute pressure ratio on the compressor; Pk - absolute pressure behind the compressor. Pa; PH - absolute pressure at the inlet to the compressor. Pa; k is the adiabatic exponent.

Neglecting the loss of pressure and temperature in the air supply channel due to the injector to the unit, we have:

Rvh Rk;

Tvkh - Tk.

Thus, with an increase in the PC air compression ratio in the GTE compressor, for example, from 2 to 11, there is an increase in its heating from 323 ° to 673 K (from 50 ° to 400 ° C).

-f heat taken from the air passing through the inter-throttle chamber, then:

CJm Mm dTm / dt - (Thx - Thy) (5), where

Cm is the heat capacity of the material of thermal capacity, J / (); Ш - mass of heat capacity elements kg; d is the differentiation operator; Tm is the temperature of the thermal capacity, K; t is the time, s;

GB - air flow, kg / s; Cp - heat capacity of air at constant pressure,

J / (kgAgrad);

Tvh - air temperature at the inlet to SCHK, K; Tvikh - air temperature at the inlet to the output choke SCHK, K;

When heating the air in the MC ShchK to the temperature of the elements of the thermal capacity Tgo "Thy, the last equation will be:

Cpb Mr h Twx / dt “(Twx - Thy) (6).

The delay time constant caused by heat transfer processes is defined as

tT M MmvkCm / () (7).

Studies of the system of equations (1) - (7) show that for a heat capacity 4 with a mass of Mm 10 g, made of copper and at an air flow rate of 6 in 1 g / s, us), we have a constant delay time tT 3.5 from. (see the graph of Fig. 4).

For comparison, we note that in order to carry out the usual delay circuit with chokes that let through a flow rate of the order of 1 g / s, a time constant of Lt 3.5 s is achieved by using a tank of the order of 2.5 liters.

The implementation of the thermal capacity in the form of a pipeline allows you to increase the surface area of the exchange and get air at the inlet to the output choke with a temperature close to / temperature of the pipeline (thermal capacity), thereby increasing the sensitivity of the CCC.

When performing a pipeline with a length of 10 or more calibers, an increase in the sensitivity of the MPC is achieved. This is achieved by constructing a thermal tank 4, providing air (gas) inlet to the output choke 3 with a temperature equal to the temperature of the thermal tank. The influence of the length of the pipeline on the operation of the device for air will be determined by the formula of V.G.Shukhov:

(T (x) - T4) / (Tvx - T4) exp (-c6 "r d x / Cp / G) (8)

here:

о (- heat transfer coefficient from air to the pipeline wall, W / m2 / deg;

l 3.1416;

d is the inner diameter of the pipeline, m;

X is the length of the pipeline, m;

Cp is the heat capacity of air, kg / deg;

6 - mass air flow through the pipeline, kg / s;

T (x) Thy - the air temperature at the outlet of the pipeline, equal to the temperature of the air at the inlet to the output choke 3, ° K.

The value of the heat transfer coefficient a will be found from the equation:

t 0.021 .8 .45 (9)

here:

NU - (10)

Re, (11)

C, is the coefficient of dynamic viscosity of air;

p is the density of air;

W 4 G / p / Jt / d2 - average air flow rate in the pipeline.

Equation (8), taking into account (9) - (IS) and taking into account (for air) .2, can be brought to the form;

(Thy-T4) / (Thy-T4) "exp (-0.) (13)

Consequently, at x / d 10, the flow gives off more than 63% of the available heat to the pipeline ((TWX-T4) / (TBX-T4) "0..63),

Taking into account the increase in the heat transfer coefficient in the initial section of the pipeline gives 70%.

A further increase in the length of the pipeline to 30 calibers will increase this figure to 95%, which will give a corresponding increase in the sensitivity of the device with a slight increase in its weight and gabsrits. Therefore, the implementation of the pipeline with a length of 10 or more calibres provides the device with sufficient (when used in the ATS GTD) sensitivity of the device.

If the pipeline is made in the form of two coaxially arranged pipelines, then it becomes possible to insulate the flow from environmental influences and thereby increase the stability of the VDK.

Exiting the throttle 1 and entering the pipeline as a jet ejector allows directing the air flowing out of the throttle 1 to the pipeline, forming a flow at a sufficiently high speed inside the pipeline, which intensifies the heat exchange process between the air and the elements of the thermal capacity, increases the sensitivity of the device, allows you to reduce the size.

The exit from the pipeline and the entrance to the throttle 3 by the type of jet ejector allows you to direct the entire air flow from the pipeline to the throttle 3, avoiding leaks into the cavity of the inter-throttle chamber, which reduces the effect of heat transfer with

-to. . . . ,. : .- ..,. ..- ...-: - L. ..-- i

the walls of the inter-throttle chamber, and therefore the influence of the temperature of the environment on the operation of 1SC.

In order to prevent air leakage from the cavity of the inter-throttle chamber and thereby do not form air circulation in the inter-throttle chamber, leading to the intensification of heat exchange with the external environment, a throttle 5 is installed in the pipeline, the selection of which can achieve minimal (zero) suction. The throttle 5 may be made in the form of a Laval nozzle or diaphragm.

The inlet throttle 1 can also be made in the form of a Laval nozzle with an outlet cross section larger than the narrow section of the outlet throttle 2, which allows gas-dynamic losses to be reduced to pressure losses in the system of shock waves in the Laval nozzle, i.e., to local losses, which will reduce the impact of friction losses in the pipeline and will increase the accuracy of the device.

If we heat-insulate the thermal capacity from the walls of the inter-chamber. Ш) Ной chamber, then, reducing heat exchange with the external environment, we obtain a more stable MPC time constant.

Thus, the proposed device with a relatively small size and weight allows you to get a significant constant delay time, which extends the range of application of this type of alkali.

Head ONTSH U) (Z r.v. Yauk

Claims (9)

1. A pneumatic dynamic corrector comprising an inter-throttle chamber formed by a series-connected inlet throttle, a pneumatic tank and an output throttle, characterized in that a thermal capacity is introduced into the inter-throttle chamber.  2. The corrector according to claim 1, characterized in that the thermal capacity is made in the form of a pipeline.  3. The corrector according to claim 2, characterized in that the pipeline is made with a length of more than 10 calibers.  4. The corrector according to claim 1, characterized in that the thermal capacity is made in the form of a package of pipelines, for example two, coaxially arranged.  5. The corrector according to claims 2 to 4, characterized in that the inlet to the pipeline and the exit from the inlet choke are made as a jet ejector.  6. The corrector according to claims 2 to 5, characterized in that the exit from the pipeline and the entrance to the output choke are made by the type of jet ejector.  7. The corrector according to claims 2 to 6, characterized in that an additional throttle, for example a diaphragm or a Laval nozzle, is installed in the pipeline.  8. The corrector according to claims 1 to 7, characterized in that the input throttle is made in the form of a Laval nozzle with an output section area greater than the narrow section area of the output throttle. 9. The corrector according to claims 1 to 8, characterized in that the thermal capacity is insulated from the walls of the inter-throttle chamber.