RU2653867C1 - Test stand for aggregates of lubrication systems on oil-air mixture - Google Patents

Abstract

FIELD: test equipment.

SUBSTANCE: invention relates to the field of test equipment, namely, to test stands for lubrication systems on an air-oil mixture, and can be used for dispersing mixed phases in the testing of lubrication systems for aircraft engines. Essence of the invention consists in that the oil dispenser is made in the form of a flat perforated splitter installed in the air cavity of the tank parallel to the oil surface, and the air circuit is communicated with the oil circuit and the air cavity of the tank.

EFFECT: technical result consists in the realization of the air entrainment effect in the formation of an air-oil mixture with a uniform distribution of gas bubbles.

1 cl, 1 dwg

Description

The invention relates to the field of testing equipment, and in particular, to stands for testing units of lubrication systems on an oil-air mixture, and can be used to disperse mixed phases during testing of aircraft engines.

In the lubrication systems of aircraft engines, the air-oil mixture from the supports of the rotors enters the venting path, and the air-oil (liquid-gas) mixture in which air bubbles are suspended in the oil enters the pumping path, which contains a pump, filter, pipelines and other units. To determine the characteristics of the units of lubrication systems when working on an air-oil mixture, another principle is needed to obtain a dispersed mixture and, therefore, other stand schemes. To obtain a two-phase mixture and determine the characteristics of the units when working on it, the effect of air entrainment in a closed test loop can be used. This allows us to solve the problem of testing the units on a liquid-gas mixture with the required volumetric gas content, in which air bubbles are suspended in the liquid.

A device for mixing gas and liquid, including a liquid circuit containing a cylindrical body with liquid and air cavities, a line for input and output of liquid and gas, and a flat perforated liquid divider installed in the lower liquid cavity of the body (patent RU 2035983, 1995).

In a known technical solution, the mixing of the liquid and gas phases is carried out in a mixer, made in the form of a vertical pipe installed in the housing. In this case, the liquid phase under pressure is supplied to the atomizer located in the upper part of the housing and is sprayed, creating high-speed fluid flows, which allow the gas phase to be sucked from the air cavity into the mixer. At the outlet of the mixer, the gas-liquid mixture is dispersed (crushed) as a result of a dynamic impact on a perforated divider (dispersant). When gas is supplied to the lower part of the housing under the divider (dispersant), a gas cushion is formed, gas jets enter through the holes of the divider (dispersant) and interact with the gas-liquid mixture.

A significant disadvantage of the known technical solution is the complexity of the design of the device, which does not provide the possibility of using it for testing units of lubrication systems of aircraft engines using an air-oil mixture.

A well-known bench for testing lubrication systems, containing a closed working circuit, including a tank, the lower volume of which is an oil source, an air source and a mixer, interconnected by pipelines with executive bodies ("Friction and lubrication in machines and mechanisms", 2015 city, No. 10, pp. 36-37, Fig. 2).

In a known technical solution, the air source is made in the form of a compressor, and the mixer is made in the form of an oil cavity with nozzles for supplying oil placed in it. Oil is supplied to the inlet of the injection pump from the lower volume of the tank without gas inclusions and is supplied to a sprayer made in the form of nozzles located in the oil cavity of the mixer. The cavity is pressurized by air through the air circuit, made open and in communication with the atmosphere. In bearings, the oil is crushed into small droplets and, mixed with the incoming air, forms a two-component mixture. In this case, the air-oil component of the mixture enters the upper part of the oil cavity of the mixer and then into the venting system, and the air-oil component enters the lower part and then through a closed working circuit to the tank.

A significant drawback of the known technical solution is the uncontrollability of the distribution process of the components of the mixture along the height of the oil cavity of the mixer, depending on random factors, which makes it difficult to obtain the volumetric gas content of the mixture required for testing.

The closest set of essential features to the claimed technical solution is a stand for testing units of lubrication systems (breathers), including a closed working circuit containing a mixer, with sources of oil and air, and a housing for placing the test unit, communicated with each other via a pipeline with executive bodies (Tryanov A.E. et al. “Designing systems for venting oil cavities of aircraft engines”, ed. SGAU, Samara, 2006, pp. 21-22, Fig. 15).

In the known technical solution, the air circuit is made open, oil from the tank through the pipeline of the closed working circuit and air from the pressure source are supplied to two-component gas-liquid nozzles of the mixer, in which the components are divided into smaller droplets both due to the directed movement of the jets and beyond account of the vortex movement, and then into the housing on the test unit. After that, oil from the housing is pumped into the tank through the trunk of a closed working circuit, and air is discharged through the open air circuit into the atmosphere.

The main disadvantage of the known technical solution is the complexity of the stand design due to the need to have parallel oil and air circuits, an air pressure source (compressor or air ramp) with communications for forming an air-oil mixture with suspended drops of oil in the air, a mixer with two-component gas-liquid nozzles.

The technical problem, the solution of which is provided by the implementation of the claimed invention, is to simplify the design of the stand.

The technical result achieved by the implementation of the present invention is to realize the effect of air entrainment in the formation of an air-oil mixture in which air bubbles are suspended in oil.

The effect of air entrainment in the formation of an air-oil mixture is as follows. In a closed tank-pump-tank circulation loop, when the medium is returned to the free volume of the tank (in its upper part with air), due to the action of gravitational forces, the flow breaks up into jets and droplets. When they collide with the surface of the liquid volume of the tank at the point of contact, the effect of air entrainment is realized. In this case, concavity is formed at the place of incidence, and during the process of air entrainment into the liquid, the phenomenon of pinching of air bubbles between the stream (drop) and concavity walls predominates, and when the walls are destroyed, involvement occurs due to the formation of air cavities and pinching of air near each individual drop of falling liquid.

The claimed technical result is achieved due to the fact that in the test bench for assembling lubrication systems on an oil-air mixture, including a closed working circuit containing a mixer with sources of oil and air, and a housing for placing the test unit, communicated with each other via a pipeline with the executive bodies , the mixer is made in the form of a tank, the lower volume of which is a source of oil, and the upper volume is a source of air, and a flat perforated divider installed tank parallel to the oil surface, and the stand has an additional contour preparing oil-air mixture formed in a pipe line, which input through a corresponding actuator communicates with the working circuit at the inlet into the housing, and an output - to the upper tank volume.

These essential features provide a solution to the technical problem posed with the achievement of the claimed technical result, since:

- the implementation of the mixer in the form of a tank, the lower volume of which is a source of oil, and the upper volume is a source of air, and a flat perforated divider installed in the tank parallel to the surface of the oil, simplifies the design of the stand by eliminating the air circuit, pressure source and two-component gas-air nozzles;

- supplying the stand with an additional circuit for the preparation of the air-oil mixture, made in the form of a pipeline main, the entrance of which through the corresponding executive body is connected to the working circuit at the inlet to the chamber, and the outlet - with the upper volume of the tank, provides the air-oil mixture using simple technical means.

The present invention is illustrated by the following description and drawing, which shows a diagram of the proposed stand. In the drawing, the following notation:

1 - tank;

2 - the volume of the lower part of the tank 1;

3 - the volume of the upper part of the tank 1;

4 - perforated divider;

5 - housing for placement of the test unit;

6 - sections of the pipeline main of the closed working circuit;

7 - the executive body of the pipelines of the working circuit;

8 - pipeline main circuit;

9 - the executive body of the pipelines of the additional circuit;

10 - circulation pump;

11 - electric drive of the pump;

12 - oil volumetric flow sensor;

13 - input tap;

14 - controller.

The test bench for assembling lubrication systems on an air-oil mixture includes a closed working circuit containing a mixer made in the form of a tank 1 with an oil source representing the volume 2 of the lower part of the tank 1 and an air source representing the volume 3 of the upper part of the tank 1 and perforated a divider 4 installed in the volume 3 of the upper part of the tank 1 parallel to the surface of the volume 2 of the tank 1, and a housing 5 for accommodating the test unit (not shown in the drawing). The volume 2 of the lower part of the tank 1 and the housing 5 are communicated with each other by means of sections 6 of the pipeline with the executive body 7 installed on it. The stand is equipped with an additional circuit for the preparation of the air-oil mixture, which is made in the form of a pipeline 8, the input of which is connected via the executive body 9 to the working circuit at the entrance to the housing 5, and the output with a volume of 3 the upper part of the tank 1. The intake of air-oil mixture to the housing 5 is carried out using the installed pipeline ca 10 circulation. An additional circuit through the pipe line 8 and the actuator 9 provides the mixture from the circulation pump 10 to the volume 3 of the upper part of the tank 1 and to the perforated divider 4. A contour is formed of the formation of the air-oil mixture in the volume 3 of the upper part of the tank 1. The circulation pump 10 is rotated by the electric drive 11, the volumetric flow rate in the working and additional circulation circuits is measured by the sensor 12. To fill the volume 2 with oil of the lower part of the tank 1 from an external source (not shown in the drawing) at the pipeline inlet of the main line of the working circuit, a crane 13 is installed. The frequency of rotation of the electric drive 11 and the state of the actuators 7 and 9 are controlled from the controller 14. The actuators 7 and 9 can be made in the form of solenoid valves or in the form of adjustable inductors having the state “open” and “ closed". An air separator can be installed in the pipeline line 8 of the additional circuit, from which the liquid phase enters the volume 2 of the lower part of the tank 1, and the released air flows into the volume 3 of the upper part of the tank 1 (these connections are not shown in the drawing).

The test bench for units of lubrication systems for air-oil mixture works as follows.

The stand operates in two modes of pumping the mixture:

mode 1 - the formation in the circulating tank volume of the air-oil mixture with the desired value of the volumetric gas content;

mode 2 - testing the unit on the resulting air-oil mixture.

When the valve 13 is open and the organs 7 and 9 are closed, the volume 2 of the lower part of the tank 1 is filled with oil and the air-oil mixture is formed with the required value of the volumetric gas content (mode 1).

At the command of the controller 14, the actuator 7 of the working circuit is in the "closed" position, and the actuator 9 of the additional circuit is switched to the "open" position. In this case, a circulation loop is formed: “volume 2 of the lower part of the tank 1 — sections 6 of the pipelines of the working circuit — circulation pump 10 — open actuator 7 — pipe line 8 of the additional circuit — volume 3 of the upper part of the tank 1”. The controller 14 sets the required speed of the actuator 11, the pump 10 is displayed on the desired mode of pumping oil, and the oil flow is controlled by the sensor 12.

In the tank-pump-tank circulation loop, when oil is returned due to the action of gravitational forces in volume 3 of the upper part of the tank 1, the incident stream decays into jets and drops. When they collide with the surface of the volume 2 of the lower part of the tank 1 at the place of incidence, concavity is formed. In this case, the process of involving air into the liquid is realized, and the phenomenon of pinching of air bubbles between the stream (drop) and concavity walls predominates, and when the walls are destroyed, involvement occurs due to the formation of air cavities and pinching of air near each individual drop of falling liquid. As a result, the effect of air intake is realized and an oil-air mixture is formed. After a certain time, the mixture enters from the volume 2 of the lower part of the tank 1 to the inlet of the circulation pump 10, which returns it to the volume 3 of the upper part of the tank 1, where the mixture is again split into jets and additionally saturated with air. Thus, tank 1 is used as the mixer, while the mixer does not require air from a separate high pressure source, because its role is played by volume 3 of the upper part of tank 1. As a result of the implementation of the air entrainment effect, an air-oil mixture is formed on the surface of volume 2 of the lower part of tank 1. The process of preparing the air-oil mixture is accompanied by the movement of air from the volume 3 of the upper part of the tank 1 to the volume 2 of the lower part of the tank 1, gradually increasing its volume. The mixture fills the volume 2 of the tank 1, the volume of sections 6 of the pipeline of the working circuit and the volume of the pipe line 8 of the additional circuit.

To ensure testing with a given volumetric gas content α _{cm of the} mixture in the range typical for lubrication systems α _cm = 0.2 ... 0.5, the initial volume V _3.n between the _divider and the oil surface in tank 1 is determined from the following ratio:

where V ₂ - the volume of the lower part of the tank, filled with oil.

The process of preparing the mixture is cyclic, with a period of Δt _{f.s. cm of} formation of the mixture, depending on the residence time of the mixture in the volume 2 of the lower part of the tank 1 and the pipelines of the working and additional circuits, and continues until the mixture in the circulating volume of the tank 1 with the required volumetric gas content, the mixture is formed in the form of a finely dispersed stable oil-air emulsion, without coalescence of air bubbles due to the action of surface tension forces at the interface. Characteristic indicators of the mixture formation process are:

- coefficient k _cc, air entrainment, which is determined experimentally for a specific tank configuration and indicates the amount of entrained oil _cc ΔQ a flow rate Q _n in an air circulating circuit;

- time Δt _{k.c of the} stay of the _oil -gas mixture in the oil circuit with a volume of V _c.c. circulation.

Number of draws air in one cycle equals the product of the coefficient k by the amount of air entrainment _cc volumetric flow rate Q _n Bleed mixture in the circulation circuit:

Taking the value of k _cv constant, for m cycles in oil the following amount of Q _{cv of} entrained air will accumulate:

The value α _see maslogazovoy fine void fraction is the ratio of mixture volume flow Q _cc of entrained air to the total volumetric flow rate Q _f air and liquid, i.e. to the value of Q _n pumped mixture:

Relation (3) shows that at a constant value of pumping the mixture to obtain the required value of α _cm volumetric gas content, it is necessary to provide m pumping cycles. Considering that the time Δt _{k.c of} one pumping cycle is equal to the ratio of the volumes V _{k.c of the} circulation circuit and the volume flow Q _{n of the} pumped mixture in the circulation circuit (the residence time of the jets in volume 3 of the upper part of tank 1 can be neglected), we obtain the following relation for determine the time T _{f.sm. the} formation of the mixture with the desired value of α _cm :

Substituting the expression for m from relation (3) into relation (4), we obtain:

Relation (5) allows us to determine the time of formation of the air-oil mixture with the desired volumetric gas content. It also allows you to select the pump mode of operation and the volume of the tank to minimize the time of formation of the mixture.

The obtained value of the formation time of the mixture should be considered as an approximate value, because the coefficient k _cc air entrainment may change during cyclic form a mixture of the decrease in volume of the liquid phase in the mixture, free of air bubbles and other factors.

For a more accurate estimate of the volumetric gas content of the resulting air-oil mixture, it is advisable to use devices for direct measurement of the volumetric gas content α _cm , for example ultrasonic ones.

The constancy of the volumetric gas content can be controlled by analyzing the constancy of pressure in the mixture pumping line - as the volumetric gas content increases, the pressure begins to decrease, and when the volumetric gas content decreases, it increases.

After receiving in the volume 2 of the lower part of the tank 1 the required value of the volumetric gas content, a transition is made to the test mode of the unit installed in the housing 4 of the stand (mode 2). For this, at the command of the controller 14, the executive body 7 is transferred to the "open" position, and the body 9 - to the "closed" position. As a result, a closed circulation loop is formed: “volume 2 of the lower part of the tank 1 — sections 6 of the pipeline of the working circuit — circulation pump 10 — casing 5 with the tested unit — closed actuator 9 — sections 6 of the pipeline of the working circuit — volume 2 of the lower part of the tank 1 ". The controller 14 sets the required speed of the actuator 11, and the circulation pump 10 is displayed on the specified mode of supply of the mixture to the test unit. Closing or opening the actuator 9 provides the required pressure at the outlet of the unit during testing.

To stop the tests, the electric drive 11 of the rotation of the pump 10 is turned off.

Thus, the implementation of the mixer in the form of a tank, the volumes of the upper and lower parts of which are sources of oil and air, respectively, installed in the upper part of the tank parallel to its lower part of a flat perforated divider, and supplying the stand with an additional circuit in communication with the working circuit and the upper part of the tank eliminates the need for a compressor to supply air and two-component gas-air nozzles in the mixer, which simplifies the design of the stand.

Claims (1)

Test bench for assembling lubrication systems on an oil-air mixture, including a closed working circuit containing a mixer with sources of oil and air, and a housing for placing the test unit, communicated with each other via a pipeline with executive bodies, characterized in that the mixer is made in the form of a tank , the lower volume of which is a source of oil, and the upper volume is a source of air, and a flat perforated divider installed in the tank parallel to the surface of the oil, and the stand equipped with an additional circuit for the preparation of the air-oil mixture, made in the form of a pipeline main, the entrance of which through the corresponding executive body is in communication with the working circuit at the entrance to the housing, and the output with the upper volume of the tank.

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