DE3010147A1 - Industrial gas-fired burner digital control - controls air feed in dependence on variable gas feed responsive to output demand - Google Patents

Abstract

The control delivers a defined amount of air to the gas feed adjusted in turn by a setting motor control in dependence on the required energy output of the burner. The received gas vol. and the corresp. air vol. are held as digital words in respective binary stores. The stored gas vol. is compared with a digital word defining the required gas vol. and the result of this comparison is used to control read-out of the corresponding air vol. from the second binary store. The read-out value is then fed by a D/A converter to the setting control for the air feed. A digital processor may be used to obtain the setting for the latter setting control by interpolation of specific stored values, to provide greater flexibility.

Description

Digital arrangement for controlling a gas burner

Technical Field - The invention relates to a digital arrangement for controlling a gas burner, in which one is specified via a gas actuator A defined amount of air is assigned to the amount of gas by means of an air actuator and the adjustment of the gas actuator by means of a depending on the energy requirement of the burner operated servomotor.

State of the art There are gas-fired industrial burner systems with a gas actuator for the gas supply to the burner and an air actuator known for supplying air to the burner. The steep members can be used as valves or Throttle valves be formed. The gas actuator is operated by a servomotor, which is controlled by pulses from a temperature controller; the air actuator is connected to a cam via a flexible shaft, which in turn is connected to the shaft of the gas servomotor is connected and which changes when the gas servomotor is changed turns. The curve is made by a movable one arranged on the disk Support scanned and transferred to the flexible shaft. The realization of what is required The gas-air ratio takes place by means of a curved belt arranged on the disc, which can be adjusted in its position via a number of adjusting spindles. The gas actuator with servomotor and the cam disc form a structural unit.

The air actuator is therefore controlled depending on the gas throughput, whereby the air flow rate is adjusted via the cam.

Due to the wide variety of operating conditions in the burner systems is a general adjustment of the curved belt after the manufacture of the above named dismantling unit not possible; the setting for the air volume can only be done on site, i.e. in the respective burner systems, and requires a considerable amount of time Adjustment work by operating the adjusting spindles, with the burner in the most varied Positions and the mixing ratios must be checked.

Different weather conditions that cause the combustion process influence, and therefore have to be taken into account, are costly because of this Adjustment work ignored.

The object of the invention is to provide an arrangement for To create control of a gas burner, in which a simple adjustment of the Gas-air ratio with the elimination of the cam and the associated time-consuming adjustment work on the curve belt is possible.

Solution This object is achieved in that the digital words associated with the gas quantities occurring and the required air quantities assigned digital words of comparable order are each contained in a binary memory are and that a digital word derived from the predetermined amount of gas with the stored digital words assigned to the gas quantities by means of a comparison device is compared and that, taking this comparison into account, the amount of air is assigned te digital words by means of a readout and converter device from the air quantities assigned I3inary memory read out and converted into analog electrical signals affecting the air actuator.

Expedient further developments of the invention are the contradictions refer to.

Advantages The advantages achieved by the invention are particular in that the air supply is mechanically decoupled from the gas supply, so that a greater flexibility in determining the assignment curves is achieved that the Previous curve characteristics for the air supply as digital words in a binary memory are enrolled, thereby considerably reducing the workload on site is; this also results in greater accuracy in setting the gas-air ratio and any curve characteristics for the gas supply can easily be used stored in memory.

DESCRIPTION OF THE INVENTION The invention is illustrated below with reference to FIG In the drawing schematically illustrated embodiments explained in more detail. 1 shows a basic embodiment of the invention, and FIG. 2 shows another basic design of the invention, Fig. 3 is a diagram with a gas-air characteristic, FIG. 4 shows an embodiment of a digital interpolator used, FIG. 5 shows an embodiment for writing characteristic curve data into the memory used, FIG. 6 shows a control arrangement using a microprocessor, Fig. 7 shows an embodiment for enrollment of characteristic data into the memories using a microprocessor.

In Fig. 1, only those necessary for understanding the invention are necessary Components of an industrial cleaning system shown, in which an automatic Control of the air supply takes place.

The voltage UT of a temperature sensor 1 is a temperature controller 2 supplied, which controls a servomotor 3, which via a gear 4 on for example designed as a throttle valve acts gas actuator 5, of which Gas is passed to the burner, not shown; furthermore is a controllable, For example, an air actuator 6 also designed as a throttle valve is present, which air is sent to the burner.

The system-side training described so far is fundamental known.

The gas servomotor 3 is driven by it and connected to a direct voltage assigned position potentioineter 7, on whose wiper 8 an electrical Voltage uG occurs, which corresponds to the angular position of the gas throttle valve 5.

The air actuator 6 is via a gear 9 of another Adjusted servomotor 10, which also has a position potentiometer connected to a direct voltage 11 is assigned, the grinder 12 of which is connected to a servo control device known per se 13, which controls the air servomotor 10. The voltage u1 on the grinder 12 of the potentiometer 11 corresponds to the angular position of the air throttle valve 6.

The voltage uG at the wiper 8, which is generated by the gas actuator 5 corresponds to a predetermined amount of gas is fed to an analog-iiital converter 14, at the output of the voltage corresponding to the magnitude of this voltage digital Words PG occur.

There is also a binary memory 15 with, for example, sixteen memory spaces provided, in the certain Gasmcngexl or certain defective positions of the gas actuator 5 associated digital words X. are included, which one of the respective Represent the gas volume range adapted to the burner system. In another binary memory i6, which also has sixteen memory locations, are stored in these specific air volumes or specific angular positions of the air actuator 6 associated digital words Yi, which has an air volume range tailored to the gas volume range represent.

The digital words PG des corresponding to the predetermined amount of gas Analog-to-digital converter 14 are located in memory 15 with the digital Words X. compared by means of a digital comparison device 17, which one digital value is determined as the digital word VD of a further digital comparison device i8 is supplied, which this digital word VD with those in memory 16 is supplied digital words Y. compares and based on this comparison a digital Word YS outputs which by means of a digital-to-analog converter 19 into an electrical analog signal uS is implemented, which the servo control device 13 in the sense of a Setpoint influenced, so that if there is a discrepancy between this setpoint voltage uS and the actual voltage uI, which also acts on the servo control device 13 of the position potentiometer 11, the servomotor 10 and thus the air actuator 6 is adjusted.

The digital words Xi, located in the binary memories 15, 16, Y are therefore burner characteristic points; don't need these digital words already according to the course of the desired characteristic in successive memory locations to be filed if the comparison facilities 17, 18 such are designed that a very fast interrogation of the stored in the memory 15, the digital words X. assigned to the gas quantities if one of the predetermined ones is present Gas amount assigned digital word PG takes place, which is also for the query of the located in the memory 16, the air quantities associated digital words Yi bei Presence of a digital one determined from the comparison of the digital words PG and Xi Word VD applies.

The digital word VD is used as the address of the second comparison device 18 supplied, which from the memory 16 the assigned air value as a digital Word Y. reads out and supplies the digital-to-analog converter 19 as a digital word YS.

In Fig. 2 are for setting the gas / air ratio, respectively two digital words Xo, Xu and Yo assigned to the gas quantities and the air quantities, Yu used.

The arrangement again consists of the binary memories 15, 16 with sixteen Digital words assigned to gas and air positions, one of the binary memory 15 associated with the word selection circuit 20, a word selection circuit E associated with the binary memory 16 21, a digital comparator 22 and an interpolator 23.

In the memory 15, the digital words Xmax to Xmin are in a row stored with decreasing values and the words Y to Y in the memory 16 in the same Episode.

inax min Xo, Xu and Yo, Yu are each a pair of words.

The word selection circuits 20, 21 synchronously query the memory locations the memory 15, 16 from the higher to the lower values and take over two adjacent superimposed digital words XO, X and Y, Y and the like u same atomic number. The digital word assigned to the lower value X of the word pairs is fed to the comparator 22, which also contains the from the previous benen gas amount derived digital word PG receives; the digital words Xo, Xu and the digital words Yo, Yu are fed to the interpolator 23, which also the digital word PG derived from the specified amount of gas and the one at the output of the comparator 22 occurring digital signal is supplied.

The operation of the arrangement in connection with the diagram of FIG. 3 explained in more detail.

That is the specified amount of gas or the angular position of the gas actuator 5 representing digital word PG is pending at the comparator 22 and may in its Valence between the digital word pair Xol Xu of the memory 15 lie.

The memory locations of the memories 15, 16 are starting from X max interrogated by means of the word selection circuits 20, 21 and the digital words arrive to the comparator 22; there is a digital word Xu facing one another at this one the digital word PG has a smaller value, the comparator 22 outputs via the line 24 a signal to the word selection circuits 20, 21 and the further interrogation of the memory locations is stopped. At the output a of the word selection circuit 20 there is thus a value Digital word X u located below the digital word PG and a above at output b the digital word X lying next to the digital word PG. The synchronous hb-0 also ask the memory locations of the memory 16 by means of the word selection circuit 21 at the end of the query at its output a is the digital word Yu and at its output b the digital word Yo.

As can be seen from the diagram according to FIG. 3, this is the default Gas amount (angular position of the gas actuator 5) representing digital word PG within the digital stored words Xo, Xu; are also available the stored digital words Yo, Yu.

The digital words Xo, Xu and Yo, Yu determined by comparison are fed to the interpolator 23, to which the digital word PG is also fed and which of these input digital words the digital setpoint value YS determined for the setting of the air actuator 6. The interpolation takes place after the equation: Yo - Yu YS = Yu + (PG - Xu) Xo - Xu According to FIG. 4, there is the digital Interpolator 23 from a subtracter 40 and a downstream fraction generator 41, which form the term 1 / (Xo - Xu) from the applied digital words Xo and Xu, which is fed to a multiplier 42, which also has the value Y -0 of another Subtracter 43 is supplied to which the digital words y and Y are placed are; the result (Yo - Yu) / (Xo - Xu) of the multiplier 42 is another Multiplier 44 supplied, which also from a subtracter 45 the value PG - Xu receives and which his result [(Yo-Yu) / Xo-Xu)] (PG-Xu) an adder 46, which also receives the value of the digital word Y, at its output the u setpoint YS for the required, by means of the servomotor 10 and air actuator 6 adjustable air volume occurs.

The invention is not restricted to linear interpolation For example, a parabolic interpolation can also be used of four curves points are made.

As can be seen from FIG. 3, those in memory 16 are digital words Ymax to Yo, Yu to Ymin Function values of the stored digital Words Xmax to X @, Xu to Xmin. In the memory 15 is a curve for gas point by point stored and in memory 16 accordingly a curve for air. The intermediate points are determined by means of interpolation.

The input of the digital words will now be described with reference to FIG in the memory 15, 16 explained in more detail.

For charging the accumulators 151 16 with a desired gas-air ratio corresponding digital words Xì, Yj are the servomotors 3, 10 with their potentiometers 7, 111 the air servo control 13 and the two analog-to-digital converters 14 1 19 used.

A device that detects the state of combustion is also provided 51, which via line 52 receives a signal from an exhaust gas measuring device, not shown in detail receives, through which it is reported that a perfect combustion is present; the device 51 sends control signals to the air servomotor via a connection 53 10. There is also provided a manually adjustable potentiometer 54, which is connected to a DC voltage; the DC voltage tapped by the grinder 55 uL is fed to a servo control 13 ′ assigned to the gas servomotor 3. Further is provided a controllable switch he 56 for the analog-Digi tal converters 14, 19 occurring digital words Xi, Yi, 1 a binary counter 57, whose count is represented by means of a display 60 and that by its change in count Memory space switches 58, 59 of memory space assigned to the memories 15, 16 switches to memory space, these switches 58, 59 the outputs G and L of the switch 56 lead to the memory locations of the memories 15, 16 and the. digital words Xi, Y present at these outputs G, L have been read.

Using the potentiometer 54, the setpoint for the gas quantity is set, whereupon a corresponding amount of air is set by means of the device 51. After this the adjustment (both motors 3, where at standstill) has been set, is carried out by means of Pressing the key 63 activates the through switch 56, thereby saving the digital words at the output G, L via the memory switch 58, 59 in the memory locations specified by the counter 57. Afterward the count of the counter 57 increases by one, whereby the memory location switch 58, 59 access the next memory space, as indicated by the arrows is.

A new setpoint is then set using the Potentiometer 54.

The counter 57 can be increased by one counting step via a manual switch 61 been reset and by means of a further ren IIandschalters 62 can be a count are skipped1 whereby the position of the memory space switches 58, 59 is changed accordingly.

Instead of the device 51 which detects the state of combustion to adjust the air volume also a DC-powered potentiometer similar the potentiometer 54 may be provided, the wiper of which is connected to a 1 the servo control 13 'is connected to the equivalent servo control. In this case the potentiometer 54 is operated first and the appearance of the burner flame is observed and then the further potentiometer is set to the optimum flame; thereon This is followed by a storage of the two standing at the analog-to-digital converters 14, 19 digital words in the memories 15, 16. Then another takes place again Adjustment of the "gas" potentiometer 54 and then under observation the Drenner flame a graduation on the further "air" potentiometer, whereupon the The two new digital words are saved, etc.

In the arrangement according to FIG. 6, a microprocessor is provided, which is an essential part of the arrangements according to the preceding figures used functional elements combined.

There is again a temperature sensor 1 provided, which the burner measures generated temperature; the temperature proportional signal from sensor 1 is fed to a temperature controller 2, which controls the gas servomotor 3, which acts via the gear 4 on the actuator 5 to adjust the gas supply. The air servomotor 10 acts via the gear 9 on the actuator 6 for the air supply.

The positions of both servomotors 3, 10 are determined by the position potentiometer 7, 11 determined, represented as digital words by means of an analog-to-digital converter 14 ', which are fed to a microprocessor 70.

This essentially consists of a control unit 71, a data memory 72 (RAM) and a program memory 73 (ROM); the data memory 72 consists of the Storage locations 15 'assigned to gas quantities, storage locations assigned to the air quantities 16 'and an auxiliary memory 74, while the program memory 73 is a servo program 13 ', a comparator program 22', an interpolation program 23 'and a selection program 75 contains. The microprocessor 70 removes by means of the control unit 71 and the im Program memory 73 contains selection program 75 to the data memory 72 of the series according to the digital words assigned to the gas quantities occurring and stored in the memory locations 15 'and compares them using the comparator program 22' with the im Auxiliary memory 74 stored, corresponding to the current gas supply digital word; are those adjacent to this digital word in the memory part 15 ' the digital words located in the data memory 72 are found, they are combined with the two associated, located in the memory part 16 'of the data memory 72 digital words for the air supply to the interpolation program 23 'supplied, which by means of the control unit 71 determines the setpoint for the air supply therefrom. The servo program 13t compares the determined in this way by means of the control unit 71 Setpoint with the means of the potentiometer 11 of the air servomotor 10 and the analog-digital converter 14 'in position b of a switch 76 controlled by the microprocessor 70 is determined current value of the air supply and derives a control signal for the air servomotor from it 10 from, which arrives at this motor 10 via an amplifier 77, which supplies the air to the setpoint value, the allocation between gas volume and air volume is restored stored digitally by pressing a button, as explained in more detail with reference to FIG. 7 will.

A potentiometer 78 is used to manually set the target value for the gas supply corresponding voltage is set, which by means of an analog-to-digital converter 14X ' converted into a corresponding digital word and fed to the microprocessor 70 will. This digital word is associated with the one corresponding to the actual value of the gas supply digital word 1 which by means of the potentiometer 7 of the gas servomotor 3 and the Analog-to-digital converter l4 "is determined with the help of the servo program 13 'des Control unit 71 compared. The control signals are derived from the result of this comparison formed for the gas servomotor 3, which act on this via an amplifier 79, so that the setpoint for the gas supply set on potentiometer 78 results.

The air servomotor 10 receives again from the device 51, which the Combustion state detected, control signals.

If the combustion is correct, 90 can be done by working the key 63 "save" a save program located in the program memory 73 80 are activated, which by means of the control unit 71 through the potentiometer 7, 11 and the analog-to-digital converter 14 ″ provided digital words of the actual values of the two servomotors 3, 10 to DEU by a counting register contained in the data memory 72 he 57 'indicated place of the gas storage part 15' or the air storage part 16 ' passes on: and stores there. The index is then increased by one, so that the next time the key 63 is pressed, the next memory location is occupied. The key 62 is actuated with the aid of a in the program memory 73 located operating program 81 a reduction of what is visible in the display 60 Counting reading by one, while pressing key 61 increases the counting reading by one will.

Claims (5)

Claims 1. Digital arrangement for controlling a gas burner, at which a gas quantity predetermined by a gas actuator by means of an air actuator a defined amount of air is assigned and the adjustment of the gas actuator by means of a servomotor operated depending on the energy requirement of the burner takes place, characterized in that the gas quantities occurring associated digital Words (Xi) and digital words (Y.) assigned to the required air volumes are more comparable Order in each of a binary memory (15, 16) are contained and that one of the specified Gas quantity derived digital word (PG) with the stored, assigned to the gas quantities digital words (Xi) is compared by means of a comparison device (17) and that, taking into account the comparison of the air volume, associated digital Words (Yi) by means of a readout and converter device (18) from the air quantities assigned binary memory (16) read out and converted into analog electrical signals which affect the air actuator (Fig. 1). 2. Arrangement according to claim i, characterized in that means Word selection circuits (20, 21) as a function of the amount assigned to the predetermined amount of gas digital word (PG) several stored in the vicinity of this word (PG) lying digital, den Words associated with gas quantities (Xo, Xu) and correspond to the stored digital words assigned to the air volumes (Yo, Yu) of comparable order and that these selected words (XO, X; Yo, Y) are used for interpolation by means of a digital arithmetic unit (23) are1 whose result (YS) is the setpoint (us) for the air actuator (6) (Fig. 2). 3. Arrangement according to claim 2, characterized in that a microprocessor (70) is provided in whose data memory (72) the information (Xi, Yi) for the gas-air mixture is stored and a program is stored in its program memory (73) (23 ') for the interpolation of each selected from the data memory (72) digital words (XO, Xu; Yo, Yu), a programni (75) for the word selection of the im Data memory (72) standing digital words (Xi, Yi) and a program (22 ') for the comparison of the digital word (PG) assigned to the specified gas quantity with the selected digital words (Xo, Xu) assigned to the gas quantities are (Fig. 6). 4. Arrangement according to claim 1 to 3, characterized in that for Writing the digital words (Xi, Yi) in the binary memories (i5, 16) using them the combustion state of the burner flame changes the amount of gas, digitally implemented and accordingly the amount of air is adjusted and converted digitally and that the both converted, corresponding to the gas and air volume set in each case written digital words in the binary memory (15, 16). be and that this The process is repeated several times over the operating range of the burner (Fig. 5). 5. Arrangement according to claim 4, characterized in that the servomotors (3, 10) of the actuators (5, 6) for gas and air manually (55) and / or by means of a Control device (51) can be set, and that their position by means of analog-to-digital converters (14,19) can be converted into digital words (Xi, Yi), which the binary memories (15, 16) for the gas and air quantities.