FI65500C - FOERFARANDE FOER REGLERING AV VOLYMSTROEMMEN AV ETT MEDIUM - Google Patents

Description

65500

METHOD OF ADJUSTING THE VOLUME FLOW OF THE MEDIUM

The invention relates to a method for adjusting the volume flow of a medium to blue in a flow channel, in which a valve S placed is adjusted on the basis of suitable quantities, such as, for example, the pressure prevailing in the channel and / or the temperature of the flowing medium.

Normally, the volume flow of the medium is adjusted by installing a suitable valve in the flow channel, which itself contains the means for the control.

It is already known e.g. devices in which the energy 15 required by the member used to stabilize the volume flow is obtained from the kinetic energy of the medium. The disadvantages are the relatively large pressure difference required and the difficulty of adjusting.

Finnish Patent Publication No. 60,069 discloses a method based on 20 cascade phenomena for stabilizing and / or controlling the volume flow of a gaseous medium. In this method, a cylindrical space is provided in the flow channel with end walls provided with openings, in which the area ratio of the openings is adjusted by suitable means and thus the flow of medium in the channel takes advantage of the pressure difference created by the medium's own flow.

The media volume flow control methods described above are directed to flow control. In the case of regulating the flow of hot and / or highly variable gas, for example, problems are encountered immediately. High temperatures affect the reliability, performance, and accuracy of conventional control valves. In this case, you have to resort to expensive special-35 solutions.

65500

The method according to the invention is not linked to any particular system or application. However, the invention is well illustrated in an application for controlling the combustion air flow, i.e. draft, in a central heating boiler.

5 In this application of the method, the butterfly valve located in the flue is adjusted e.g. by the pressure in the flue and / or the temperature of the heating water.

In the control systems of small and / or medium-sized central heating boilers, a coil spring made of bimetallists or other similar thermostat is usually used to control the burner. This closes the combustion air hatch via the chain when the water temperature reaches the set maximum value.

15

The described control system has several drawbacks. It only affects the supply of primary air. Continuous control of the secondary air has not been implemented in any way. The control system has a certain delay, which causes variations in the burning of the fuel. The system is also not sensitive to pressure changes in the flues caused by variations in wind direction and pressure as well as temperature variations in the flue gases.

25 In fact, that system is intended only to prevent the heating water from boiling. It does not actually seek to maintain a steady supply or draft of combustion air. However, such a system would be especially necessary in boilers that use and continuously supply 30 solid fuels.

The disadvantages of a control system using a bimetallic coil spring or the like can be avoided by installing a flap valve or the like in the flue, which is regulated on the basis of the pressure of the flue gases and the temperature of the heating water. The outdoor temperature 3 65500 can also be taken into account in the control. However, such a system requires a large number of electronic and electromechanical components, which are necessary for detecting and adjusting the position of the valve flap. In this way, when installing ra-3, the equipment becomes expensive and requires a lot of maintenance.

The object of the invention is, inter alia, to avoid the above-mentioned drawbacks and to implement a method for controlling the volume flow with a gap, which can be used at very low pressure differences and also at high temperatures of the flowing medium. This is achieved by the features of the invention as set out in claim 1.

13

It is a further object of the invention to provide a method for controlling draft and fuel combustion in a boiler which maintains a selected constant draft flue gas pressure between certain maximum and minimum values 20 and / or which is sensitive to variations in heating water temperature. This is achieved by the features of the invention as set out in claim 2.

23 The method according to the invention is well suited for keeping the draft constant, especially in boilers using solid fuel. The device even reacts to small changes in flue gas pressure due to variations in flue gas temperatures to variations in flue thermal height and wind pressure and direction. The indoor and outdoor temperature can also be used as a control variable for the system according to the method.

35 4 65500

The invention will now be described in detail with reference to the accompanying drawings.

Fig. 1 shows an embodiment of a method for adjusting the tensile strength of the invention in a sectional view; Fig. 2 shows the cascade flow principle applied in the traction control method;

Figure 3 shows an illustration of how the formula for the differential pressure ratio of a cascade flow is applied in a control method according to the invention; Fig. 4 illustrates how the control method is applied to the control of the draft of a central heating boiler;

Figure 5 shows a flap valve mounted on a flue; Figures 6-10 show diagrams by means of which the control cone can be dimensioned; Figure 11 shows an adjustment cone.

The draft control apparatus according to Figures 1 and 4, to which the method according to the invention has been applied, comprises an actuator 10 with control and setting means 23, a thermostat-20 valve 30, a filter 41 and a flue-mounted valve comprising a valve body 50, a butterfly valve 51 and connecting means 52.

The valve body 50 is mounted in the flue 43 of the central heating boiler 42 25. The heating boiler uses solid fuel and operates with natural draft. The thermostatic valve 3Π is connected by an inlet pipe 46 to the boiler heating water outlet pipe 44 and by an outlet pipe 47 to the boiler heating water return pipe 45, respectively.

30

The operation of the draft control device is based on the cascade differential pressure ratio formula schematically shown in Fig. 2 (see, for example, Kurt W. Geisler: Reqel-unq von Heiz- und Klima-Anlagen, 2nd edition, Marholz-Verlag, 35 Berlin 1969, p. 65). ). With reasonable pressure ^ differences and when n denotes the ratio of the pressure differences between the spaces 65500

n s (p2 - P3> / (P1 - P3) * (O

then 5 n = _1_ (2) (d2 / d- |) ^ + 1 is valid where p-ι, P2 and P3 represent pressures and Ρί> Ρ2> Ρ3 and and d2 denote the diameters of the gaps between spaces. 10 Thus, if d2 = d-j, then n s is 0.50 and the pressure difference P2 to P3 = 50% of the total pressure difference.

Figure 3 illustrates how the above cascade flow differential pressure formula is applied in a control system according to the invention. The space between the walls is made flexible. The wall against the inlet pressure p-j or the wall against the outlet pressure P3 or both can move axially so that the distance between the walls can change with the distance β <|. A control cone or a similar piston-like member acting as a control member 20 is placed in the opening d2 so as to form an annular equivalent opening d'2. Then d * 2 - f (si, y), where y is the radius of the cone. The control cone is fixedly connected to the wall against the inlet pressure pi. The opening d-j is also provided with a control device so that it can be replaced by an equivalent annular opening d '-j s f (s2), where s2 is the absolute distance in the flow direction in question. the plate or the like in front of the opening moves. This plate can, if necessary, be replaced by a second control cone forming a second equivalent opening d "i = f (e2, z), where z is the radius of said cone.

Aperture d-j or its equivalent aperture may be located outside the actuator 10 to assist the channel. However, the diameter of the channel 35 must be a multiple of the equivalent diameter of the opening d 1 or 6 65500 in order for Equation (2) to be correct and not to form a 2-stage cascade system.

The actuator 10 in Fig. 1 comprises a cylinder base 11 to which a control valve housing 12 is fixed by means of a nut 13 and further a piston 14 hermetically sealed to the cylinder base 11 by a flexible annular groove 13 connected in turn by a protective ring 16 ay 1 to the intermediate base 11.

The piston 14 is connected by means of a flange 17 and a sealing sleeve 1Θ to a hollow arm 19 which is axially movable on a linear rolling bearing 20. The rolling bearing 20 is of the type having endless rolling grooves. The rolling bearing is housed in a sleeve 13 which is part of the control valve housing 12.

The piston force and movement of the piston 14 of the actuator 10 are further transmitted by means of a spindle 21. The groove 21 is parallel to the sleeve 16 and fastened to it by a suitable sealing sleeve 22 or 20, respectively. The axially movable spindle 21 is part of the adjusting and setting means 23.

The control valve housing 12 of the actuator 10 is provided with radially openings 24, the total area of which is a multiple of the area of the opening 25 d'i. In this way, the control valve i1 has unobstructed access from the cylinder space. The control valve housing 12 has a seat ring which, together with the conical end 19 'of the shaft 19, forms an opening d * 2 * 30 of the control valve. The control valve housing 12 is provided with a support piece 25 against which a spring 26 rests at one end. A spring guide 27 is connected to the spindle 21, by means of which the spring force is further transmitted through the spindle to the adjusting and setting means 23. The adjusting knob 28 is provided with threads for axial adjustment / setting 35 and further with a rolling bearing 29 for moving the spindle 21.

7 65500

The thermostatic valve 30 is sensitive to the temperature of the heating water. The cross-sectional area of the connecting wire 30a is a multiple of the area d1i.

The filter 41 is threadedly connected to a nozzle 39, which in turn is bn fixed to the valve body 31 and sealed by an O-ring 38. The other end of the valve body 31 forms an actual thermostat part with a thermostat 40, a sealing ring 32, a connection piece 33. The connection piece 10 33 has inlets and outlets. connected to the heating water inlet pipe 46 and the outlet pipe 47, respectively.

The mandrel 34 is moved by means of a thermostat 40. The balancing force is generated by the return spring 36. The axially arms-adjustable control cone 37 together with the nozzle 39 forms an opening d'-j of the control valve.

The axial displacement of the spindle 21 associated with the adjusting and setting means 23 is transmitted by means of a rod 52 and two tip bearings 20 to a butterfly valve 51, which is also mounted on two tip bearings to minimize friction.

The draft control system according to the invention presented above is based on the pressure control between different spaces, in particular according to the principle of 25 cascade flow.

The control air cleaned by the filter 41 passes through the opening d '-j to the thermoacetate valve 30, from where it further flows through the conduit 30a and the actuator 10 through the openings 24 to the control housing 30. From here the control air travels through the opening d * 2 to the flue 43 and mixes with flue gases. When the equivalent diameters of the openings d'-j and d '2 are only a few millimeters, the volume flow of the control air is small, but it cools the equipment sufficiently. On the other hand, the air volume flow is also sufficient for the system 65500 to react quickly to changes in the flue pressure. The position control of the butterfly valve takes advantage of the direct connection of the control device to the flue so as not to cause unnecessary friction with vague sealing sleeves and bearings.

5

A certain position of the stem 21 corresponds to a certain opening angle of the flap valve 51. The forces exerted by the spring 26 and the butterfly valve system are in balance with the piston forces exerted by the actuator 10 and Equation (2) is valid.

10

The decrease in flue gas pressure causes the piston 14 to move to the left (Fig. 1) together with the adjustment and setting means 23 until the area of the orifice d * 2 is reduced enough to restore the uniformity of Equation (2) and required the balance of the entire control system. When the cone 19 'of the shaft 19 is suitably dimensioned, the butterfly valve 51 always reaches a position in which the flue gas flow rate, i.e. the draft, remains unchanged.

The increase in flue gas pressure causes a decrease in the piston forces exerted by the actuator 10 and the force caused by the spring 26 causes the cone 19 'to move to a new position where the area of the opening d * 2 is large enough and equation (2) is again in balance.

25

At a certain maximum temperature of the heating water of the central heating boiler, the thermostat 40 reacts and raises the spindle 34 until the control cone 37 has finally completely closed the opening d'-j. Then d-j = 0, n = 1 and the pressure difference p-j - P2 30, i.e. the full pressure difference, acts on one side of the piston 14. The tail 14 now moves to its leftmost position (Fig. 1) and thus reduces the flue gas flow accordingly. The reduced draft in turn has a depressing effect on the heating water temperature. After a suitable drop in temperature, a spring 36 pa-35 trays the thermostat towards the initial state.

9 65500

The figures and curves in Figures 5-11 show how e.g. the desired shape of the adjustment cone can be determined.

Figure 5 shows the flap valve 51 5 mounted on the flue in the closed position. The flow direction of the flue gases is upwards in the valve body 50 of the figure. When the valve 51 is opened at an angle 0 <, the result is a counterclockwise torque caused by aerodynamic forces, which is balanced to some extent by a counterweight 53. The resultant force produced by the torques 10 transmitted to the stem 21 by the rod 52 is denoted by P53 and plotted in Figure 6. function.

In Fig. 7, the force P53 together with the force F15 caused by the spring 26 is plotted as a function of the percentage opening of the valve 51. The opening is dimensioned as the axial displacement of the mandrel 21. The sum of the forces P53 and F is denoted by FP53. The piston forces M produced by the piston 14 are denoted by the same shaft arrangement when d '1 = 0. These forces are denoted by - M9 and correspond to constant pressures of 1 to 9 units per unit area.

In Fig. 8, the vertical flow of the diagram shows the volume flow V ^ -V9 as a percentage and for the horizontal axis the 25% opening of the valve, which corresponds to constant pressures of 1-9 units per unit area, respectively.

Looking at Figures 7-8 for a given volume of air, which is, for example, 50% of the maximum value, a vertical AC passing through the intersection of the curve V1 and the horizontal V = 50% can be drawn. Corresponding verticals can also be drawn from other intersections of the horizontal V = 50% and the curve V2 -V9.

35 10 65500

In the above figures, the distance AB represents the piston force required to maintain the balance of the control system compared to the maximum piston force available at this pressure of 1 unit per unit area. The ratio of the sections is AB: AC 5 = n, ie the ratio of the pressure differences.

In Fig. 9, the values of n for the pressure differences for the percentage values of V from 25 to 100 are plotted against the percentage value of the opening. Each curve n has a corresponding position of the adjustment knob 28.

It can be seen from Fig. 9 that at a certain position e of the flap valve 51 different flue gas flow rates can be realized with different differential pressure values f, g, h. Thus, it is possible to change the flue gas flow rate by changing only the size of the opening d'i. This can be done with certain limitations related to the pressure range. This possibility is exploited in the thermostatic valve 30. It is particularly advantageous in Fig. 9 to move horizontally along the constant differential pressure line a-b-c-d 20, which takes place by means of control and setting means 23.

When the spring constant of the spring 26 and the torque of the flap valve 51 are suitably dimensioned, the differential pressure ratio curves can be combined with sufficient accuracy into a common curve, as shown in Fig. 10. In this case, at certain aperture d'- | values and the seat diameter values of the control valve opening d * 2, the shape of the control cone 19 'of the shaft 19 according to Fig. 11 can be easily determined by utilizing one to 30 (2). However, certain experimental corrections are necessary. These are mainly due to the different air flow coefficients of the circular and annular orifices.

The control method according to the invention has been described above with reference to only one preferred embodiment thereof.

11 65500

Thus, the method can be used to control the volume flow of a medium in general, even in the range of very low pressure differences and even at high temperatures, by cooling the medium used for control. The method is, of course, also suitable for ventilation systems in buildings.

In the embodiment of the invention described above, the device applying the method can also be constructed to act e.g. as a boiler flue gas scrubber bypass valve 10 opening from the closed position when the pressure difference between the flue gas filter and the flue gas blower has reached the limit and clogging causes energy loss. This is based on the fact that the control function of the method, i.e. in this case the thrust of the spindle 21 as a function of its displacement, can be freely selected by means of the shape of the conical end 19 'of the shaft 19. Since several operating ranges are available according to Fig. 9, it is also possible with the same valve to open the path 20 for natural draft, e.g. in the event that the flue gas fan stops due to an electrical disturbance, causing an explosion hazard in addition to psla. In this case, the control opening d-j is reduced by means of a spring-return magnet so that the flap valve 51 already opens with a pressure difference corresponding to the grate resistance.

It should also be noted that the actuator 10 represents a solution in which the operating range can be selected by the setting means 23. For the bypass valve described above, this is not necessary, but the stem 21 and the hollow stem 19 can be one substance.

Said control also facilitates remote control using magnetic, hydraulic or pneumatic components known per se, with or without a timer 35 and controlled, if necessary, by means of a radio signal.

Claims (3)

A method for controlling the volume flow of a medium in a flow channel, wherein a valve 5 located in this flow is regulated on the basis of suitable ether units, such as, for example, the pressure prevailing in the channel and / or the temperature of the flowing medium by utilizing a cascade flow a grounding method, in which an advantageous cylindrical space is provided in conjunction with the evacuation channel, which provides gable walls, at least one of which is arranged movable and which space is joined through a preliminary opening (dj) with the input pressure (p aida and through a second opening (d2) with the side of the output pressure (P3) and whereby the regulation of the pressure (P2) in the cylindrical space is effected by changing the relative content of the openings (dj, d2) by movable wall fixed, as piston actuators (14, 19) or the like and / or by regulating the surface content of the openings from the outside of the cylindrical tube a space sl, that the piston force required in regulating the flow, which throttles the one-discharge opening and that required for the regulation at each time and pressure difference, is equal to the sum of the forces acting against it, characterized in that with the flow channel, a control flow channel from a suitable comparison space is combined, wherein the current control volume stream of medium is controlled by means of said p1 cascade flow, which is a basic process, in which the said flow channel has been arranged as said cylindrical or equivalent. the provided opening (dj) is joined to the side of the comparison space (p ·)) and through the second opening (d2) to the side of the flow channel and the displacement of the movable wall and at the same time the coif is transferred to a control movement for the position of the the duct installed the valve or the like. 15 65500 Method according to claim 1 for controlling the combustion air flow or draft of a central heating boiler, in which method a valve located in the flue duct is controlled by means of suitable devices, such as, for example, the flue duct determining pressure and or the temperature of the heating water, characterized therein. in the vicinity of the central heating boiler, an air flow duct is provided to the flue duct, wherein the air flow or the volume flow of the control duct regulated in the flow duct is regulated by a method known per se in the cascade flow, which, in conjunction with said flow device, provides a has end walls provided with openings (dj, d2), of which the etminatone one is arranged movable and wherein the control of the control air flow is effected by changing the relative surface contents of the openings by means of a piston attached to one movable wall (14, 19). and for the shooting of them The moving wall and at the same time the coil are further transferred to a control relay for the position of a flap (51) in the valve installed in the flue. Method according to claim 2, characterized in that the surface content of the first opening (d 2) in the cylindrical space is controlled by means of a spindle or a similar means, which is offset by a thermostat (40). , which has been arranged to react sensitively to the temperature of the heating water. A method according to claim 2 or 3, characterized in that, at the movable wall, the cow (14, 19) acting as a regulating means (14, 19) is attached a suitable control cone (19 '), by means of which the second opening (d2) ) equivalent opening (d'2) is determined and further together with the counter forces the control system's equilibrium state Snd.