Ejectors in the ventilation of the paint chamber. Experience in the design of natural-mechanical ventilation in residential buildings with warm attacks for what you need an ejector in ventilation

Mechanical consumer ventilation can be a supply, exhaust and supply-exhaust, with recycling and without recycling. With this ventilation system, centrifugal (Fig. 5, a), axial fans (Fig. 5,6) or ejector installations (Fig. 5, c), roof fans (Fig. 5, g, d) move air through aircraft with branches having nozzles and dampers to regulate the influx or air removal.

Fans are used in supply, exhaust and supply and exhaust systems, ejector installations - mainly in exhaust ventilation systems.

Ejector installations are used in industrial premises, in which explosive pairs and gases are enshrined and where the installation of the conventional type fan, causing the sparking and explosion when damaged by the parts of the fan and explosion, is not allowed, for example, when removing contaminants from the batteries charging, from painting cabins in the absence of hydrotreaty.

Encuting air movement is that one or more nozzles are inserted into the pipe, air from the compressor or fan, steam or water, which carries polluted air under pressure. The ECD ECTECTory will depend on its design features.

Appointment of ventilation supply systems - reimburse air, removed by local suction and pneumatic transport in workshops and departments (machinery, finishing, assembly, chipboard, etc.) and speakers for technological needs.

When the ventilation consumption is a consistent consuming system (Fig. 6, a), the air receiver for the fence of clean air, which is supplied to the room with a fan, is installed outside the building. The air is taken at height from the ground at least 2.5 m. The air purified and warmed to the required temperature is distributed through the channel system - air ducts.

The air is fed to the working area (into the space from the floor level to the breathing level of 1.8 ... 2 m) with possible low speeds. It is impossible to supply air through the zones in which it is dirty.

The exhaust consumer ventilation system (Fig. 6, b) is characterized by the fact that through the network of air ducts 13 and 12 polluted air is removed by a fan 11. Clean air in this case is suitable naturally through the lootability of doors, windows, lanterns, cracks, pores of building structures. The exhaust holes of the air ducts are located at different heights, which is established depending on the purpose of the premises and the density of the removed pollution. For example, if contamination is removed, which are heavier than air (pairs of phenol, gasoline), steam or gas receivers have a floor, and if the ceiling is easier. In accordance with CH 245-71, SNIP P-33-75, GOST 12.4.021-75 and fire standards are not allowed to combine into one common exhaust setting of outpass of lightly condensible vapors and gases, as well as compounds that, when mixed, can create a poisonous flammable or explosive mechanical mixture or chemical compounds. For example, it is not allowed to combine outs from pneumatic conveying plants with suction from painting and drying chambers; From painting cabins, when nitrocellulosic is used in one of the cabins, and in another polyester varnishes. The air stuck or contaminated with poisonous pairs or gases before throwing into the atmosphere is purified and neutralized in special installations.

The supply and exhaust ventilation system without recycling (Fig. 6, B) consists of a supply and exhaust system, simultaneously supplying clean air and removing contaminated (pre-purified) into the atmosphere. Such a ventilation system is considered the best under the condition that air removed by exhaust general and local ventilation systems will be compensated by the supply system of ventilation.

The supply and exhaust ventilation system in the reporting rooms should be arranged in such a way as to be excluded the possibility of air from premises with a large excretion of the hazards or with the presence of explosive gases, vapors and dust in rooms where these harm is less or not.

Ventilation with recycling (Fig. 6, d) is a closed supply and exhaust ventilation. The air, sucking with an exhaust system, is secondally fed to the room with a supply ventilation. Recycled air is partially replenished with fresh. It is not allowed to apply recycling in rooms with toxic fire and explosive air pollution.

In all ventilation systems, the air intake unit is set to the wind roses (from the windward side to the ejected mines), but not closer to 10 ... 20 m from the emitting holes. The pipe through which the air used is released into the atmosphere must be located at least 1 m above the roof skate.

Method for calculating the ejector air distributor for livestock ventilation systems

M.M. Achapkin, Candidate of Technical Sciences

It is well known that from the point of view of technical and economic indicators to ensure optimal microclumatic conditions in livestock buildings, ventilation systems with adjustable, depending on the change in external meteorological conditions by air exchange, are the most acceptable. However, the process of regulating the air exchange, taking into account the constructive features of traditional ventilation systems is the most complex engineering task.

The solution to this problem is greatly simplified when using ventilation systems for supplying air-based air concentrated jets into the upper area of \u200b\u200bthe room. At the same time, an ejector air distributor (eV) is used as a regulator, which is the simplest ejector of low pressure bundled with a supply mine (Fig. 1). The driving force of the supply air regulation process is

P and s. 1. Schematic diagram of the work of the ejector air distributor: 1 - nozzle; 2 - a hole for the air; 3 - mixing camera; 4 - inlet shaft;

5 - throttle valve

the energy of the air flow coming out of the nozzle.

The essence of the calculation of any engineering and technical means, including eV, is known to be in determining its geometric characteristics to ensure the required parameters of the medium being processed depending on the specified. In our case, in accordance with the theory of jet development in the closed space, the parameters of the supply air at the output from the mixing chamber are set. Thus, knowing the required air flow rate at the exit of the eV and the cross-sectional area of \u200b\u200bthe livestock room, according to the formula represented in, you can determine the diameter of the mixing chamber (supply nozzle eV) ¿3:

where r ^ r about - the maximum allowable

reverse air flow rate, m / s;

LC - second air flow, m3 / s;

cross section area, m2.

It is known that in ejectors of the mocked flow, moving streams in a mixing chamber, as well as their stirring occur due to the kinetic energy of the flow of the working jet, arising from the nozzle. Consequently, for normal operation, EV should be created at the outlet of the nozzle such high-speed pressure P \\ U 12/2, the value of which was

equal to (or exceeded) the sum of the required high-speed pressure of the sucked flow, high-speed pressure on

outlet of the mixing chamber, pressure loss in suction air ducts DR2 and in the mixing chamber DR3,

P3u3 2/2 + AR2 + AR3,

where U2, UZ - air velocity in the characteristic sections of EV, M / C;

Ya2\u003e r h - air density in

characteristic sections, kg / m3.

Setting the condition for the equality of air densities in the characteristic sections of EV (P \\ - P2 - RZ) and considering that the amount of air at the outlet of the mixing chamber should be equal

the amount of air at the outlet of the nozzle l \\ and on the plane of the suction 1 ^ 2 z \u003d a + ^ 2)\u003e by simple transformations, you can get an approximate value of air velocity at the output of izopol:

Taking a living section of the suction flow of air / 2 \u003d ^ s ~ and expressing costs in the characteristic sections through the corresponding speeds and their square, we will find:

In accordance with the obtained data on the theory of streaming, the speed of air is specified in the characteristic sections and, according to the well-known formulas, the aerodynamic characteristics of EV are calculated, including the pressure loss in suction wagers of the DR2 and in the mixing chamber DR3.

It should be noted that the value of the optimal length of the mixing chamber for engineering calculations is more convenient to determine the graphics of the degree of constraint of the jet and the mixing chamber length of the mixing camera obtained on the basis of experimental studies.

personal values \u200b\u200bof the stitching coefficient (3 shown in Fig. 2.

0,5 1,01,5 2,0 2,53,03,54,04,5 5,0 5,5

Fig. 2. Graph of natural values \u200b\u200bx \\ and * 2 at different values \u200b\u200bof the coefficient

mix

If the results of the calculations are confirmed, taking into account the reserves of the pressure of about 10 ... 15% expression (2), then the calculation of the EV can be considered completed.

The process of regulating the air exchange is carried out by changing the amount of the flexible flow in per ~ of probability from the outdoor temperature values \u200b\u200busing the throttle valve of the supply mine.

In accordance with the foregoing, the essence of the method of calculating the evidence is as follows:

The required air exchange is determined with the characteristic values \u200b\u200bof the outdoor temperature from ¿"AH to

t1P and by formula / 3 \u003d b \\ calculated

the required installation mixing factor;

According to the formula (1), the diameter of the mixing chamber (inlet nozzle) is determined for the case of maximum installation of the installation on the WHO Spirit;

The geometric and aerodynamic characteristics of the flows in the characteristic sections of the EV are determined. In this case, air flow at the outlet of the nozzle is taken to be equal to the required air exchange when

The process of regulating the air exchange is calculated depending on the values \u200b\u200bof the outdoor temperature ranging from ¿"AH to

equipment for cooking

air and its filing is selected to ensure the required air exchange

generally accepted technique from the condition when

Bibliographic list

1. Bakharev V. A., Trojanovsky V.N. Basics 2. Kamenev P. N. Heating and ventilation:

design and calculating heating and valve - in 2 hours. 4. 2. Ventilation. M.: Stroyzdat, 1966.

with focused air release. M.: 480 p. ProfiSdat, 1958. 216 p.

Received 25.12.2000.

Selection of modes of operation of machine-tractor units using computer equipment

A. M. Karpov, Candidate of Technical Sciences,

T. V. Vasilkin, Candidate of Mathematical Sciences,

D. A. Karpov, Engineer,

A. V. Kozin, Engineer

It is known that all agricultural operations are performed by machine-tractor units (MTA), representing a combination of the energy part transmitting the mechanism and the working machine.

Each engineer knows how difficult it is to properly choose the energy tool and working (or working) machine to get high quality, maximum performance, the smallest specific consumption and the highest value of the use of the thrust force on the hook, that is, the maximum use of traction and coupling properties of a particular energy.

For a long time, such calculations were performed manually, which required good engineering knowledge and considerable time.

Specialists had to complete MTA, based on the experience of the preceding generation or using reference data. And if calculations were made, then on simplified

the scheme that can be represented in the following form:

A range of a possible high-speed mode is set (for this working machine);

The value of the traction force at the selected speeds for these conditions is determined;

The maximum width of the capture of the unit on the selected gears is calculated;

The number of machines (or plows) is determined, based on the width of the capture of the machine (or the plow housing);

Is impedance;

The degree of loading of the tractor in the tractor will be calculated.

It should be noted that the magnitude of the maximum hourly performance is not determined and the more it is not carried out in production conditions. Such a calculation could not but lead to an erroneous solution. The task is to choose the optimal energy in the smallest energy intensity. At the Department of Mo-

To select centrifugal fans, in addition to productivity and pressure, you must select their constructive execution.

The total pressure of the RP, developed by the fan, is spent on overcoming resistance in suction and injection ducts arising from air movement:

RP \u003d ΔРВС + ΔРН \u003d ΔP,

Where ΔРВС and ΔРН - pressure loss in suction and injection ducts; ΔР - Total pressure loss.

These pressure losses consist of a loss of friction pressure (due to the roughness of the air ducts) and in local resistances (turns, changes in section, filters, calorifers, etc.).

The losses of DR (kgf / m2) are determined by summing the loss of pressure Δp, on the individual settlement areas:

where Δrts and ΔРMSI, respectively, the loss of friction pressure and in local resistances on the calculated area of \u200b\u200bthe air duct; Δrud - loss of friction pressure on 1 p. m. length; L is the length of the calculated area of \u200b\u200bthe air duct, m; Σζ - the sum of the coefficients of local resistances at the settlement site; v - air speed in the air duct, m / s; P - air density, kg / m3.

The values \u200b\u200bof Δrud and ζ are given in reference books.

The procedure for calculating the ventilation network is as follows.

1. Select the network configuration depending on the placement of rooms, installations, equipment that should serve the ventilation system.

2. Knowing the required air flow in separate areas of air ducts, determine their transverse dimensions, based on the permissible speeds of air movement (about 6-10 m / s).

3. According to the formula (3), the resistance of the network is calculated, and the most extended highway is taken for the calculation.

4. The catalogs choose a fan and electric motor.

5. If the resistance of the network turned out to be too large, the size of the air ducts increase and produce network recalculation.

Knowing what productivity and full pressure should develop a fan, make a choice of an edepentilator by its aerodynamic characteristic.

This characteristic of the fan graphically expresses the relationship between the main parameters - performance, pressure, power, and to. P. D. At certain speeds of rotation n, rpm. For example, it is required to select a fan with a productivity L \u003d 6.5 thousand m3 / h at p \u003d 44 kgf / m2. For the selected centrifugal fan C4-70 No. 6, the desired mode of operation will correspond to the point A (Fig. 8, a). At this point, the speed of rotation of the wheel P - 900 rpm and to. P. D. Η \u003d 0.8.

The most important relationship between pressure and productivity is the so-called pressure characteristic of the fan P - L. If it is imposed on this characteristic of the network characteristic (dependence of resistance from air flow) (Fig. 8, b), then the intersection point of these curves (operating point) will determine the pressure and fan performance when working in this network. With an increase in the resistance of the network, which may occur, for example, when clogged with filters, the operating point will shift up and the fan will supply the air less than it is necessary (L2< L1).

When choosing a type and number of centrifugal fans, it is necessary to be guided by the fact that the fan must have the highest to. P. D., A relatively small rotation speed (U \u003d πdn / 60), as well as thro One shaft.

Fig. 8. Diagrams of the calculation of the ventilation network: A - aerodynamic characteristics of the fan; b - fan work online

In cases where the operated fan does not provide the necessary performance, it is possible to increase it, remembering that the performance of the fan is directly proportional to the wheel rotation speed, the total pressure is the square of the rotational speed, and the power consumption - the speed of rotation speeds:

A variety of centrifugal fans are so-called diametrical fans (see Fig. 7, d). These fans have wide wheels and their performance is higher than that of centrifugal fans, but to. P. D. Below due to the occurrence of internal circulation flows.

The installation power of the electric motor for the fan (kW) is calculated by the formula

where L is the performance of the fan, m3 / h; P - full pressure of the fan, kgf / m2; ηv - k. p. d. fan (accepted by

fan characteristic); ηp - k. p. d. Drive, which is 0.9, with a flat transmission; with clinorem - 0.95; When the wheel is directly installed on the motor shaft - 1; When installing the wheel through the coupling - 0.98; K is the reserve coefficient (K \u003d 1.05 1.5).

Ejectors are used in exhaust systems in cases where it is necessary to remove a very aggressive medium, dust capable of explosion not only from impact, but also from friction or easily flammable and explosive gases (acetylene, ether, etc.).

The microclimate inside the box is very important for the paint chamber. In order for the specialist to work comfortably, and the paint fell into the surface without problems, it is necessary to install such a system that can remove the exhaust air flows from the room and direct them to the output channels. The essence of the ejector's work is that clean air supplied to the ventilation chamber is mixed with explosive pairs and harmful impurities. As a result, the change of exhaust air is performed much faster.

Device ejectors

To understand the device of ejectors, one should figure out how the removal of already exhaust air is removed in the paint box. For the maximum efficient removal of the spent air flow, ejector installations are used. The design is made of sheet steel, the thickness of the material is 1.2 mm. Installation is performed using welding, although detachable devices can be used.

As for individual elements, you can select the following:

There is nozzle that is intended to convert potential flow energy to kinetic. In practice, it is necessary to create a high-speed jet.
Passive air flow is sucked due to the creation of a vacuum. Exhaust air falls into the receiving chamber.
The ejector working chamber is needed to mix the active and passive stream, where there are harmful impurities and gases dangerous to humans. As a result of the energy exchange, one stream is obtained with the same pressure.
The flow enters the diffuser, where there is a simultaneous reduction in speed and an increase in pressure.

Principle of operation

Depends on many components - from the tightness of the chamber as a whole, from filters, for the purity of which you need to follow, from the fans. But all the listed elements will be useless if the ejector does not work as it is necessary. Everything keeps on the flow of the working environment, which enters the receiving chamber at high speed. Due to such a high flow rate, a vacuum is created, tightening the spent air.

The further effect of the mechanism was described in the analysis of the components of the ejector. In the mixing chamber, two streams face, one of which contains harmful impurities. After that, the flow falls into the diffuser and goes on the exhaust channels.

Installation features

The main problem when installing the ventilation system, and ejectors in particular, not in the process of installation, but in competent calculations. The paint chamber needs to competently design that the installed ventilation system coped with the load. The sign of proper design is the excess of the income air in comparison with flows leaving through the exhaust holes.

In the process, the design must be understood what aircraft will be. This indicator also affects the size of the paint box, and the number of simultaneously working personnel. According to the result, the specialist will output the value of the instance of the exchange, that is, the amount of full change of air volumes during a certain time. When performing painting large products, as the same car, you need to adhere to the rate of multiplicity a hundred times.

It will also be necessary to competently carry out the calculations of the cross sections of the air ducts. Given the need to work with air flows having explosive impurities, you need to install air-resistant air ducts.

Specificity of service

The service of ejectors is performed in the complex, along with the service of the entire ventilation system as a whole. Under service it is customary to understand the regular inspection of filters that are clogged by dust particles and paint residues. Cleaning filters is performed every 250 hours of operation, but only once. After 500 working hours, the filter is replaced with a new one.

As for ejectors, they are also subject to clean. It is most susceptible to pollution that is the diffuser. To clean it, it is customary to use a small plastic rod. When servicing the ejector, it is impossible to use items with sharp edges. They can damage the surface of the diffuser, disturbing its tightness.

About the need to choose a high-quality ejector installation you need to know that the quality of the color of the surfaces is completely dependent on its work. The shortcomings of the system will affect the quality of the work performed. If there is no possibility to independently monitor the quality of the elements and the correctness of their installation, then you should contact certified companies that specialize in this area - in this way you can get a guarantee that all work will be made correctly.

Use: in the mining industry when carrying out underground workings. SUMMARY OF THE INVENTION: Fan installation includes placed in the ejector channel of mining fan. The installation is equipped with an installed along the longitudinal axis of the mining machine, placed between the walls of the shell and the walls of the mountain, with a jumper and an additional fan. The main fan is set at the opposite end of the shell. Both fans are installed with a gap with respect to the walls of the hand-up output channels towards each other with the possibility of moving along the longitudinal axis of the shell. 1 il.

The invention relates to fan-building and is intended to ensure the ventilation of the mining system and ventilation systems. A fan installation on a pipeline, for example, a mine ventilation network (Ushakov K.Z. Burchakov A.M. Puchkov LA Medvedev I. I. Aerology of mining enterprises, M. Nedra, 1987). Such fan sets include fans running through a jumper. The disadvantage of the known fan installation is the incomplete use of the power of the drive motor in order to significantly (2-3 times) an increase in air flow compared to the passport capacity of the fan installation, during the operation of the latter is not a pipeline. A closer analogue to the claimed invention is a fan installation consisting of a fan-ejector installed in mining (Medvedev I.I. Carrying potash mines, M. Nedra, 1970, p. 124 139), which allows you to increase air consumption several times Compared to passport performance. The disadvantage of the well-known technical solution is the possibility of working the ejector located in the mountain development of a large cross section in the "self-on" mode, i.e. With a closed movement of air flows in the area of \u200b\u200bthe fan installation of circulating streams, as well as the difficulty in the selection of the work out of the desired configuration and in the right place to achieve the maximum ejection effect and in the expansion of the working area of \u200b\u200bthe fan ejection unit. The purpose of the invention is the expansion of the working area (industrial use area) of the fan ejecting unit. The set goal is achieved by the location of the two identical fans of ejectors at the input sections and the shell is contemplated with each other with the possibility of moving from the fans along the axis (closer-on to the shell) and overlapping the rest of the cross section of the jumper mining. The cross-sectional dimensions of the shell are determined on the basis of the optimal ratio of the cross-sectional area in the zone of the full movement of the primary flow passing through the fan and the secondary ejected one by the section between the fan and the shell. Due to this, the constant air flow with the maximum ejection coefficient (with respect to the passport performance of the fan) is provided. Disclosure of the primary stream stream (to the full mixing zone of primary and secondary streams) should occur in the shell, which prevents the movement of air flows inside the shell towards the main stream. To reduce the ejection effect from the maximum value, the fan is moved along the axis moving it away from the shell or by moving it into the shell, as shown in the drawing. This is advisable to perform if necessary, reducing the amount of air supplied by the ejection setting exceeding the possibility of controlling the performance of the fan guide apparatus, i.e. There is an expansion of the working area towards reducing the productivity. It is especially valuable that even for fans without means of productivity control (guide vehicles), it is possible to obtain on a single characteristic, and the working area, which expands the possibilities of using the fan ejection setting of the proposed type. The jumper between the shell and walls of mining will prevent the movement of air flows in this section. The work contains one of the ejector fans and regardless of the size of the mining method, in which the fan installation is located, it will have a constant air flow. In reversing mode, the second Ejector fan is turned on, located on the other side of the shell, meeting the first. The performance of the fan installation both in direct and in reversing mode will be the same. The drawing presents a fan installation, where 1 mine working; 2, 3 Ejector fans; 4 - shelter; 5 jumper; 6 Air flow with direct operation of the fan installation; 7 Ejected flow in this installation mode; 8 Air flow with reversing fan installation operation; 9 Ejected flow with reversing installation operation. Fan installation works as follows. When the fan-ejector 2 is turned on, the air flow is passed through it, 6, and by section between the outer surface of the fan 2 and the inner surface of the shell 4 passes the stream of ejected air 7. The stream 6 and 7 moves along the length of the shell and enter the mining production 1. Such a scheme Allows you to increase in several times the air flow compared to the passport capacity of the fan. Between the walls of the production of 1 and shell 4 installed jumper 5, therefore, in this section, the air movement does not occur. The shelter 4 is selected in such a way that the maximum ejection effect of air is ensured. If you need to reduce the ejection effect of more regulatory capabilities, the fan 2 (3) is moved along the axis (closer further to the shell) shown by the dotted line in the drawing. On the other hand, the sir of a mirror fan-ejector 2 is installed fan-ejector 3, which is included in the operation in reversing mode, and the fan-ejector 2 stops. In reversing mode, everything happens when the ejector fan operation is operational 2. only in the opposite direction, namely through the fan-Ejector 3 passes the air flow, and in the section between the outer surface of the Ejector fan 3 and the inner surface of the shell 4 passes the flow of ejected air 9. Threads 8 and 9 are mixed along the length of the shell and enter the mining production 1, providing an inverse movement of air through the system of mining workings, i.e. Reversal of the air jet (regulation of similarly direct work). Such a fan installation can be located in any mining work out, where it is possible to place a shell, providing work at any point of the extended working area both in direct and in reversing mode of operation. At the mine of the first Bereznik production potash ore department of Uralkali JSC, experienced works are underway to test the proposed fan installation.

Claim

The fan ejector installation, which includes a fan located in the ejector channel of minerauls, characterized in that it is equipped with a latter-mounted rowing axis, located between the walls of the shell and the wall-geneing walls with a jumper and an additional fan, and the main fan is installed at the opposite end of the shell Both fans are installed with a gap with respect to the walls of the hand-up output channels towards each other with the possibility of moving along the longitudinal axis of the shell.