FR2515314A1 - Control for gas boiler - has circuit based on pressure detectors gas pipe and of air feed rate - Google Patents

Abstract

The circuit controls the working of a gas boiler. There is a gas feed (1) having a load regulating valve (2) with a drive (5). An air feed (3,6) also has a control valve (7) and a drive (8). There is a regulator (20) for gas-air ratio formed by two groups of separate chambers (23,24,26,27) divided by a moving partition (22,25). The first two chambers (23,24) are associated with a load detector having two pressure detectors (14,15) and an obturator (13) in the gas pipe (1). The other chambers (26,27) are similarly associated with an air load detector.

Description

 The present invention relates to a method and an installation for regulating the operation of a gas boiler, in particular a gas oliaudiere equipped with a washer for the combustion air.

 There is a device for adjusting the gas / air proportion by measuring the air flow to adjust the addition of the appropriate quantity or flow of gas.

 This regulation is done using air pressure at the burner, gas pressure and pressure in the fireplace. These three pressures are applied to two chambers located on either side of two deformable membranes integral in movement, the intermediate chamber between these two membranes receiving pressure from the hearth.

 Using the integral displacement of the two membranes, the servo motor is controlled, which acts on the valve regulating the gas flow.

 In this installation, the air flow is adjusted using a thermostat detecting the ambient temperature or the outside temperature, or any other system determining the operating power, depending on the boiler control systems, to act on the servo motor controlling the throttle position.

 This regulation system has a certain number of drawbacks and, in particular, it does not take into account, for the air flow, pressure drops which occur in the pipe, in the burner, etc. However, these pressure drops are very variable for the same dry air flow rate depending on the installations, in particular when the combustion air must pass through a washer in the case of condensing boilers.

 The object of the present invention is to create a method and an installation for regulating the oxidizing gas / air ratio of the fuel mixture supplying a gas boiler, and in particular a gas boiler comprising a washer.

 To this end, the invention relates to a method for regulating the operation of a gas boiler, comprising a combustion air supply, provided with an air flow adjustment valve, this valve being positioned by a means of drive, a gas supply provided with a flow control valve, this valve being provided with a drive means; - ment, process characterized in that the air flow rate is measured before the entry of the air in the boiler, the gas flow rate is measured before entering the burner and the drive means of the flow control valves for the air supply and the gas supply are controlled to obtain at the burner, a gas / air mixture corresponding to optimal operating conditions.

 Thanks to the measurement of the air flow before entering the boiler, the gas / air ratio can be precisely adjusted to obtain optimal combustion.

 Indeed, the adjustment of the gas / air ratio depends on a certain number of known parameters, such as the physico-chemical parameters of the combustion air, those of the gas, etc.

 Thanks to the invention, we ignore the pressure losses at the burner and in the piping.

 This situation is particularly critical in the case of so-called condensing gas boilers ", that is to say of boilers in which the stream of combustion air passes through a washer before being mixed with the combustible gas in the burner.

Indeed, a washer has pressure drops which are very difficult to determine and, above all, pressure drops which are not constant over time. These pressure drops depend on the arrangement of the elements constituting the lining, the preferred paths of the quantity of washing liquid (water), on the shape of the lining elements conditioning the flow state of the washing liquid, etc.

 By measuring the air flow upstream of the washer, these various parameters are disregarded, and the gas / air ratio can be adjusted precisely.

 The invention also relates to an installation for implementing the above method, this installation being characterized in that it comprises a device for regulating the gas / air ratio, this device being constituted by two groups of chambers separated respectively by a movable partition, the first two chambers being associated with a gas flow detection-device comprising two pressure taps placed on either side of an obstacle in the gas line, the other two chambers being associated with a air flow detector, comprising an obstacle and two air intakes respectively upstream and downstream (or over) the obstacle, the two movable partitions being integral in movement to control a signal generator supplying the control signals to flow valve drive means for adjusting the gas / air ratio.

 It is particularly advantageous to measure the flow of gas or of combustion air using a flow detector constituted by an obstacle placed in the pipe, and two pressure taps respectively upstream and downstream (or on) the obstacle. This obstacle can advantageously be constituted by a venturi. In the case of a venturi, a pressure tap is provided at the neck and the other is either upstream or downstream of the venturi.

 In general, the combustion adjustment according to the invention makes it possible to adjust the power of the boiler by simply acting on the flow rate of a fluid (air or gas) since, necessarily, the flow rate of the other fluid (gas or air) is adjusted to the optimum ratio. This is a particularly effective control of a boiler because this process and this regulation installation exhibit very flexible operation, without great operating inertia.

 The figure shows an example-installation in which the gas flow is controlled as a function of the air flow.

 According to FIG. 1, the installation for implementing the process for regulating the operation of a gas boiler generally consists of a gas supply 1, provided with a valve 2 for adjusting the flow rate. The gas supply line 1 opens into line 3 of the combustion air supply, at the inlet to the boiler 4. The flow control valve 2 is controlled by a drive means 5 such that 'a motor.

 The combustion air supply consists for example of a fan 6, which supplies the combustion air to the combustion air supply pipe 3. This pipe 3 is equipped with an adjustable valve 7 controlled by a means of drive 8 such as a motor.

 -Generally, the gas line 2 opens into the air supply line 3, at the inlet of the boiler, that is to say shortly before the burner, not shown.

 The combustion gases from the boiler 4 pass through a heat exchanger 9, the heat transfer fluid circuit 10 of which feeds the user 11.

 A gas boiler such as the one above is used for example for heating buildings.

 According to the invention, the gas supply pipe 1 comprises a pressure difference sensor 12 constituted for example by an obstacle 13 and pressure taps 14, 15 respectively upstream and downstream of the obstacle 13. The obstacle can be: a usual obstacle creating a pressure drop. I1 can also be a venturi in which case the pressure tap 14 opens upstream of the venturi while the pressure tap 15 opens into the neck of the venturi.

 In the same way, the pipe 3 for supplying combustion air cpmporte before entering the boiler 4, a pressure difference detector 16 formed of an obstacle 17 creating a pressure drop as well as two pressure taps 18, 19 who. are upstream and downstream of the obstacle 17. In FIG. 1, the obstacle consists of a venturi so that the pressure tap 18 is provided upstream of the venturi 17 while the pressure tap 19 is at the neck venturi 17.

 The pressure detectors 12, 16 cooperate with a flow regulator 20 having two interior volumes separated by a partition 21. One of the volumes associated with the gas flow detector is subdivided by the partition 22 into two chambers 23, 24 while the other volume associated with the air flow detector 16 is subdivided by the partition 25 into two chambers 26, 27.

 The pressure tap. 14 is connected by a pipe 28 to the chamber 23, the pressure tap 15 is connected by a pipe 29 to the chamber 24. Likewise, the pressure tap 18 is connected by a pipe 30 to the chamber 26 and the pressure tap pressure 19 is connected by a pipe 31 to the chamber 27.

 The deformable walls 22, 25 which are, for example, constituted by pistons connected by a waterproof membrane at the periphery of the regulator 20, are connected by a rod 32, rigid, passing through the waterproof seal 33 the partition 21. This rod 32 is itself connected to a rod 34 which is associated with a signal generator 35 which controls the motors 5 and 8 by the lines 36, 37 according to the gas / air ratio, detected by the flow detectors 12, 16 and the regulating device 20, for controlling the opening or closing of the valves 2, 7 and adjusting the optimum ratio.

 Figure 2 shows the same installation regulating the operation of a gas boiler, however applied to a boiler equipped with a washer.

 The elements of this figure identical to those of Figure 1, have the same references and their description will not be repeated.

 According to FIG. 2, the boiler 4 is preceded by a washer 40 containing a lining 41 and comprising a circuit 42 for circulating the washing liquid (water) by a pump 43.

 The air supply pipe 3 opens at the base 44 into the washer 40 and exits from above, via a pipe 45 which opens, for example, in the upper part of the boiler 4. The gas pipe 1 opens in the combustion air line 45 after the washer 4.

 As indicated generally above, to have an accurate measurement of the air flow and, consequently, to be able to optimally adjust the gas / combustion air ratio in the burner of the boiler 4, the detection of the air flow is done upstream of the washer 40.

 FIG. 3 shows a variant of a regulation device according to the invention. In this variant, the same references have been used as above to designate the same elements, the description of which will not be repeated. This variant of the regulation device differs from the previous embodiment according to FIGS. 1 and 2 by the splitting of the partition 21 which is replaced by the partition 21 'and the partition 21 "forming between them a chamber 50 which is either connected to - the free air, either fitted with a pressure gauge or a safety pressure switch 51 to detect overpressures, it is advisable to avoid the passage of gas in the air, or the effect of leaks, risking form an explosive mixture.

 In the case of a gas at low pressure (for example 20 millibars) it is necessary to detect the flow of gas such as flow above while for a supply of gas at high pressure (for example 300 millibars) the variations of pressure losses on the gas line and the flame attachment of the burner are relatively less sensitive; in this case, it may be sufficient to detect the gas pressure and the pressure of the hearth (or atmospheric pressure) to significantly represent the flow rate. In the latter, the gas pressure tap must be located downstream of the gas control valve.

 Generally, the scrubbers used in the heating installation can be scrubbers such as those described in French patent applications NO 79 00 901 and 81 12 770. They can also be exchangers.

Claims (8)

 1) Method for regulating the operation of a gas boiler, comprising a combustion air supply, provided with an air flow control valve, this valve being positioned by a drive means, a gas supply provided a flow control valve, this valve being provided with a drive means, as well as at least one device with random pressure drops and which is traversed by one of the fluids upstream of the boiler, process characterized in that the flow rate of the fluid upstream of the device with random pressure drops is measured and the flow rate of the other fluid is controlled, in order to obtain a gas / air mixture at the burner level corresponding to optimal operating conditions  2) Method according to claim 1, characterized in that the first fluid is air and the second fluid is gas.  3) Method according to claim 1, characterized in that the random pressure drop device is a washer.  4) Installation for adjusting the operation of a gas boiler comprising a gas supply (1) with a flow control valve (2) and a drive means (5) for the control valve, a supply (3 , 6) in oxidant, provided with an adjustment valve (7) and a drive means (8) of the adjustment valve (7), for implementing the method according to any one of Claims 1 to 3, installation characterized in that it comprises a device for regulating (20) the gas / air ratio, this device being constituted by two groups of chambers (23, 24, 26, 27) separated respectively by a partition mobile (22, 25) the two first chambers (23, 24) being associated with a flow detection device (12) comprising two pressure taps (14, 15) associated with an obstacle (13) in the gas line ( 1), the two other chambers (26, 27) being associated with an air flow detector (16), comprising an obstacle (17) and two air intakes (18, 19), the two x movable partitions (22, 25) being mechanically associated (32) for controlling (34) a signal generator (35) supplying the control signals (36, 37) to the drive means (5, 8) of the flow valves (2, 7) to adjust the gas / air ratio.  5) Installation according to claim 4, applied to a gas boiler comprising a washer traversed by the combustion air upstream of the burner, installation characterized in that the air flow detector (16) is upstream of the washer (40) .  6) Installation according to any one of claims 4 and 5, characterized in that the flow detector (15, 16) is constituted by an obstacle (13) placed in the pipe, the pressure taps (14, 15) opening into the pipe respectively upstream and downstream of the obstacle (13).  7) Installation according to any one of claims 4 and 5, characterized in that the flow detector (15, 16) is constituted by a venturi, one of the pressure taps (18) opening into the pipe (3) upstream or downstream of the venturi and the other pressure tap (19) opening into the neck of the venturi (17).  8) Installation according to claim 4, characterized in that the pressure regulation device comprises a safety chamber (50) separating the chambers (23, 24) of the gas from the chambers (26, 26) of the air, to collect possible gas or air leaks through the passages (33) of the connecting rod (32), this safety chamber (50) being if necessary connected to the open air or connected to a pressure gauge (51) , or a safety pressure switch.