EP3121516B1 - Method for controlling a condensation boiler and boiler for performing the method - Google Patents

Description

Field of the invention

The present invention relates to a method of controlling a condensing boiler whose radiator is fed with a fuel mixture (air / gas) by a fan which is controlled in dependence on the power demand by the load circuit, according to the method after establishing the relationship for the boiler was linked to the flow rate of the fuel mixture to be supplied in dependence on the power that must supply the radiator, this relationship is recorded in the control circuit of the boiler.

The invention also relates to a boiler for carrying out this method.

State of the art

Currently, the power delivered by the condensing boilers is controlled by the blower, depending on the power requirement, which feeds the burner with the air / gas fuel mixture. The gas is automatically added to the air depending on the air flow rate. The relationship linking the flow rate Q of the fan to its speed VR is a linear relationship ( Fig. 2A ), which is set up for the single blower and recorded in the control circuit of the boiler. Such a method of controlling a condensation boiler is known, for example, from US Pat WO 2014/029721 known. This regulation of the rotational speed does not take into account pressure losses encountered by the exhaust gases forced into the exhaust duct by the fan. These pressure losses are now rarely fixed. They vary depending on from the use or overload of the exhaust pipe, especially if the exhaust pipe is common to several consumers.

Object of the invention

The present invention aims to develop a method of controlling a condensation boiler in order to optimize its operation, that is to say the power it delivers, in order to respond as quickly as possible to the demand, whether this boiler individually on an exhaust pipe is installed or is part of a shared system that is connected to one and the same line.

In particular, the invention has the aim of solving the problem of more or less accidental operation of Kondensationsheizkessel, which are connected to one and the same exhaust pipe in a common system, and in particular a renewal boiler.

Presentation and advantages of the invention

To this end, the invention relates to a method of the type defined above, wherein the blower is controlled by regulating its measured real flow rate to the target flow rate given by the defined relationship which determines the flow rate requested by the radiator with the power it must supply; connected.

This method makes it possible to take into account variable pressure losses and the backpressure (this is conventionally included in the variable pressure losses) at the outlet of the boiler in order to precisely match the instantaneous actual flow rate of the fuel mixture to be supplied to the burner and to obtain the requested heating power. and whichever the Variations of the pressure loss imposed on the flow of the fuel mixture in and out of the radiator, including in the exhaust duct, without having to know the pressure losses. This precise regulation of the power to be supplied allows even more economical operation of the condensation boiler.

According to an advantageous feature, the flow rate of the fuel mixture is measured by the pressure difference provided by two pressure sensors installed in the mixture flow on both sides of an obstacle. This measurement of the flow rate of the fuel mixture by the pressure sensors forms a particularly economical solution, since these pressure sensors, at least one of them, can already equip the boiler or are necessary for other functions, such as safety functions imposed on the boiler. In addition, the sensor installed downstream of the check valve may also provide the back pressure prevailing in the boiler when stopped in the portion upstream of the valve.

Under these conditions, and in accordance with an advantageous feature of the method, at the start (restart) of the boiler, the back pressure applied to the boiler is measured and the fan is given a speed that provides the requested flow rate and takes into account the back pressure that is applied to the boiler Current of the fuel mixture is applied and measured before starting the boiler.

Starting the boiler with a power that is practically instantaneous to the power to be delivered makes it possible to have a more efficient boiler operating time to govern the power demand almost immediately, especially when hot sanitary water is heated by the heating circuit of the boiler. This very much Quick reaction of the boiler at the moment of start also reduces the consumption or conversely increases the efficiency of the boiler.

According to an advantageous feature, the method according to the invention is recorded in the form of a program in the memory of the control circuit, which manages the operation of the boiler.

The invention also has as subject matter a condensation boiler for the implementation of this method. Thus, the invention relates to a condensation boiler which consists of a radiator which supplies the heat to a consumer circuit by the combustion of a stream of fuel mixture supplied by a controlled blower which receives the fuel mixture from a metering device containing the metered mixture of the fuel gas and the combustion air, this boiler comprising a control circuit which brings the operation of the boiler and it to safety, and manages and is connected to a device for measuring the flow rate of the stream of the fuel mixture, which is supplied by the blower to the radiator to regulate the motor of the blower so that the blower supplies the flow rate of the fuel mixture required for the radiator.

This boiler distinguishes itself by the effectiveness of its operation and its efficiency and by the possibility of installing such renewal boilers, whatever the characteristics of the variable pressure loss of the exhaust pipes downstream of the boiler, and without having to make special arrangements that would depend on the installation site ,

According to an advantageous feature of the boiler comprises a device for measuring the flow rate of the stream of the fuel mixture, which is formed of two pressure sensors installed in a mixing chamber which receives the metered mixture of gas and combustion air and comprises a check valve, which in the The flow direction of the stream of the combustion mixture in the direction of the blower opens and closes in the reverse direction, the two pressure sensors are installed on both sides of the valve to measure a pressure difference, which makes it possible to calculate the flow rate of the stream of fuel mixture.

This version of the boiler is very simple, since it uses only two pressure sensors, at least one of which is also required for the safety control of the boiler.

According to another advantageous feature, the heating boiler comprises a device for measuring the flow rate of the stream of the fuel mixture, which is formed from a hot-film flow meter, which is installed in the passage of the fuel flow, in particular upstream of the blower.

This embodiment also has the advantage of simplicity since the hot-film mass flowmeters are widely available on the market and have been developed especially in automotive engineering.

According to another advantageous feature, the boiler comprises a pressure sensor which measures the back pressure imposed on the boiler when stopped by the flow of the fuel mixture and the exhaust gases.

The pressure sensor that measures the back pressure is advantageously one of the two pressure sensors that provide the pressure difference that is used to calculate the flow rate of the fuel mixture stream.

drawings

• Fig. 1 ein Diagramm einer Heizanlage mit einem Kondensationsheizkessel gemäß der Erfindung ist,
• Fig. 2A die Beziehung zwischen der Durchflussmenge eines Gebläses und seiner Drehzahl zeigt,
• Fig. 2B ein Diagramm zeigt, das die Drehzahl des Gebläses in Abhängigkeit von der angeforderten Leistung für verschiedene variable Druckverluste angibt, die dem Strom des Brennstoffgemischs im Heizkessel auferlegt werden,
• Fig. 2C ein Diagramm analog zu jenem von Fig. 2B, aber auf den Betrieb eines Heizkessels gemäß dem Stand der Technik angewendet, ist.

The present invention will be described in more detail below with the aid of an embodiment of the method and the boiler which carries out the method, which is illustrated in the accompanying drawings, in which:

• Fig. 1 is a diagram of a heating system with a Kondensationsheizkessel according to the invention,
• Fig. 2A shows the relationship between the flow rate of a fan and its speed,
• Fig. 2B a diagram showing the speed of the fan as a function of the requested power for various variable pressure losses, which are imposed on the flow of the fuel mixture in the boiler,
• Fig. 2C a diagram analogous to that of Fig. 2B but applied to the operation of a boiler according to the prior art, is.

Description of embodiments of the invention

According to Fig. 1 the invention applies to a Kondensationsheizkessel 100, which is shown schematically for its main sections. This boiler is connected to a gas supply AG and to an air inlet AA for forming the fuel mixture. At the exit, the exhaust gases F arrive in an exhaust pipe CF. This exhaust pipe CF may be reserved for the single boiler 100 or several boilers 100A in common. The boiler 100 feeds a load circuit 200, which is a heating circuit, which is optionally combined with a circuit for the treatment of hot sanitary water or only one of the two functions (heating / hot sanitary water) ensures.

The boiler 100 consists at the entrance of a metering device 110, which feeds a mixing chamber 120, which receives the gas and the air, which are dosed in a suitable manner by the metering device, which is regulated in a fixed manner under conditions of use of the boiler. The mixing chamber 120 is provided with a check valve 121 which opens only in the passage direction of the flow forming the mixture (arrow VM). The mixing chamber 120 feeds a fan 130 which is driven by a motor 131 which supplies the flow rate of the fuel mixture to the heater 140 formed by a burner 141 which heats a heat exchanger 142 connected to the load circuit 200. The output 143 of the radiator is connected through an output line 144 to the exhaust pipe CF.

The mixing chamber 120 is divided by the valve 121 into an entrance or front section 120A and an exit or rear section 120B. The front portion 120A is equipped with a pressure sensor 122 and the rear portion with another pressure sensor 123.

The pressure sensors 122, 123 measure the pressure difference and thus the flow rate Q _R (t) of the fuel mixture. In general, however, the flow rate Q _R (t) can be obtained by measuring either air or air / gas mixture since the flow rate of the gas is pneumatically or electrically linked to that of the air.

The boiler 100 is managed by a control circuit 150 which is connected to a start / stop button 151 and also controls ordinary functions such as gas supply stop safety functions or the like, the rotational speed of the motor 131 of the blower 130 depending on the requested power taking into account the (variable) pressure loss imposed on the fuel mixture stream. The control circuit 150 receives at the input various safety information, which is not shown in detail, and the target temperature T _C and the temperature T of the load circuit 200, which make it possible to calculate the heating power P, which must provide the radiator 140. This temperature T can actually represent different temperatures, such as the temperature of the heating fluid circulating in the consumer circuit, or the temperature of the heating fluid used for the treatment of hot sanitary water. The control circuit 150 also receives information of the pressure and the difference of pressures supplied from the two sensors 122, 123 installed, for example, in the mixing chamber 120 on both sides of a pneumatic obstacle formed here by the check valve 121. The valve, which is open for the passage of the fuel flow, forms a pneumatic obstruction, which is arranged in the stream and which, by measuring the pressure difference between the two sensors, makes it possible to measure the real flow rate of the fuel mixture Q _R (t) Valve flows, that is, the flow rate of the fuel mixture, which is sucked by the blower 130 and is supplied at the output of the burner 141 to calculate. A pressure downstream of the valve can thus also be measured; the other pressure can be measured either in the air or at the air / gas mixture.

The power requested by the boiler depends on the setpoint temperature T _c , to which the load circuit 200 is regulated, and thus on the difference between the measured temperature T and the setpoint temperature T _c . The power P (t) supplied by the boiler is directly proportional to the flow rate of the fuel mixture Q _R (t) supplying the burner 141. The constant pressure drop flow rate from the blower 130 downstream of the blower is quite proportional to the speed of the blower. In reality, however, the pressure drop PCH downstream of the blower 130, in particular in the exit duct 144 of the radiator 140 and in the exhaust duct CF (which conventionally includes the counteracting pressure or back pressure), is a variable pressure loss PCH (t), since the geometry of the Exhaust pipe is fixed, but the flow rates of exhaust gases in the line CF in the time (t) are variable and they depend on the start-up and the operating conditions of other consumers 100A the exhaust pipe CF.

According to the invention, the curve of the conversion between the power supplied by the radiator and the required flow rate of the fuel mixture P (t) requested by it at the moment (t) is subsequently regulated to the real quantity Q _R (t). which supplies the boiler blower 100 when the boiler is installed in place, in response to the target flow rate Q _c (t).

This regulation is based on the difference $$\mathrm{.DELTA.Q}=\mathrm{Qc}\left(\mathrm{t}\right)-{\mathrm{Q}}_{\mathrm{R}}\left(\mathrm{t}\right),$$

The real flow rate Q _R (t) depends on the speed VR of the blower 130, which is accelerated or decelerated to cancel the difference between the real flow rate and the target flow rate, that is, to obtain δQ = 0.

This regulation can be explained by the diagram of Fig. 2A to make it possible to compare the method of the invention with the known operation represented by the curve of FIG Fig. 2C is shown.

As in Fig. 2A shown, the normal flow rate Q _{N of} a blower 100 is the one with a free output and is in total proportional to the speed VR, which is represented by the straight line C _N in Fig. 2A is shown. However, if the fan is feeding a downstream plant, that is, if its outlet is not free, the flow rate is subject to pressure losses, including counteracting pressure or back pressure in the conduit downstream of the fan; the real flow rate Q _R (t) always depends on the speed of the fan, but often on a curve C (PCH) different from the normal curve C _N. In fact, there are a number of different curves Ci (PCH) according to the pressure losses PCH to which the blower is exposed under real operating conditions. The curves C1 ... C2 are theoretical curves for a pressure loss that remains constant while the requested power varies.

According to the invention, for the boiler 100, the relationship is used which links the pneumatic properties of the various components of the circuit used by the flow of the fuel mixture VM and the variable pressure losses PCH (t) imposed on the exhaust gases F at the outlet 144 of the radiator 140 , And also the back pressure, which is found by the exhaust gases in the exhaust pipe CF. This relationship gives the flow rate of the fuel mixture Q as a function of the rotational speed VR of the blower 130 for various pressure drops PCH imposed on the flow of the fuel mixture VM supplied by the blower 130. It is basically a function with three Variables f (Q, VR, PCH) = 0 represented by a surface in a 3-axis reference system. In practice, however, this function can be represented in a plane having as variables of the flow rate Q and the rotational speed VR and as a parameter of a pressure loss PCH, which gives the family of curves in the coordinate system with axes representing Q and VR, like the diagram from Fig. 2B shows, depending on examples of different pressure drops PCHi (i = 1, 2, 3, ...) downstream of the blower 130.

In this diagram, the horizontal axis represents equally the requested power P or the target flow rate Qc, since these two quantities are linked since they are directly connected to the operation of the boiler.

For a requested power (flow rate) P (Q1) depending on the pressure loss PCH1, PCH2, ..., there is a different operating point PF1 ... PF4, that is, a different speed VR11 ... VR14 of the blower 130, as shown in FIG According to the invention, the speed of the fan VR is controlled by regulating its real flow rate Q _R (t) to the target flow rate Q _C (t), which is that for which the boiler supplies the requested power called power P ^(t) .

As an example and assuming that the curves of the diagram of Fig. 2B are known, if in an operating period the requested power (in any way) varies between the powers P1 (Qc1) and P2 (Qc2) and if in the same period the pressure loss PCH varies between the values PCH1 and PCH2, then the operating point PF shifts of the blower (and its speed) in the quadrant PF11, PF21, PF22, PF12 bounded by the flow rate curves C1, C2 and the abscissa lines P1 / Q1 and P1 / Q2 parallel to the axis Oy. This representation must enable the Difference between this method of control of the boiler according to the invention and the known method according to the diagram of Fig. 2C close. The known control method orders by application of the operating curve C _N ( Fig. 2A ) To a target speed V _RC a requested flow rate. But the fan works in reality according to the curves C1 ... C4, which link its flow rate Qx with its speed V _RX , taking into account the pressure losses encountered.

In practice, this means according to the prior art that, in order to have a flow rate, a speed V _{RC is} set for the fan and according to the pressure drop ( Fig. 2C ) This speed generates a flow rate Q11 ... Q14.

Thus, according to the illustrated example, the speed remains constant, but the flow rate varies between the flow rate Q11 ... Q14, so that each time the boiler delivers a power equal to its real flow rates Q11 ... Q14. But these real flow rates and the services provided are not the requested ones.

In other words, according to the prior art, the fan is regulated to a speed, while according to the invention ( Fig. 2B ) the fan is regulated to a desired flow rate.

As explained above, according to the prior art, the target speed VRC may vary depending on the requested power; the same applies to the target power Q _c according to the invention, but this only emphasizes the fundamental difference between the two methods, since in the case of the prior art method pressure losses and back pressures are not taken into account and false real flow rates are brought about, while according to the invention, pressure losses and counter pressures are taken into account without having to calculate them, but it is always obtained the desired flow rate, since the flow rate of the blower is regulated to this desired flow rate (target flow rate Qc (t) ).

The method of the invention carried out by the boiler 100 functions under the following conditions:
The pressure difference measured by the sensors 122, 123 makes it possible to calculate the instantaneous real flow rate Q _R (t). According to the power P (t) demanded by the load circuit 200, which is linked, for example, with the set temperature T _c and the temperature T measured by the temperature sensor 201 of the load circuit, the control circuit 150 calculates the flow rate Q _C (t) required for the radiator 140. which is the target flow rate to which the motor 131 of the blower 130 is regulated in order for the heater to receive, under these conditions, the real flow rate Q (t) corresponding to the target flow rate Q _c (t), that is, the power requested for the boiler.

In order to reduce the reaction time of the boiler at start-up and to speed up the performance increase as much as possible, account is taken of the back pressure imposed by the exhaust pipe CF and prevailing in the mixing chamber 120 downstream of the valve 121 (section 120B), the blower 130 is started immediately to the target speed, which corresponds to this back pressure, so that the flow rate Q practically from this moment is the required flow rate for the radiator 140, taking into account the back pressure of the exhaust gases F from that moment that arrive in the exhaust pipe CF.

The method according to the invention can be executed in the form of a program which is recorded in the memory 152 of the control circuit 150.

According to a variant, not shown, the flow rate of the fuel flow is measured by means of a flow meter, in particular a hot-film flow meter, which is preferably installed upstream of the blower 130.

Claims (10)

1. Method for controlling a condensing boiler, the heating body of which is fed with a fuel mixture (air/gas) by a fan which is controlled on the basis of the output requirement of the consumer circuit, according to which, after the relationship f(Q, P) for the boiler (100), which links the flow rate of the fuel mixture (Q) to be supplied to the heating body (140) with the output which the heating body must supply, has been set up, this relationship f(Q, P) is recorded in the control circuit (150) of the boiler,
   wherein the fan (100) is controlled by regulating its measured real flow rate (Q_R(t)) to the target flow rate (Qc(t)), which is given by the defined relationship which links the flow rate required for the heating body (140) as a function of the output (P(t)) which it must supply.
2. Method according to Claim 1,
   wherein the real flow rate of the fuel mixture (Q_R(t)) is measured by the pressure difference (ΔP), which is supplied by to pressure sensors (122, 123) which are installed in the flow of the mixture (VM), on the two sides of an obstruction (121) .
3. Method according to Claim 1,
   wherein the real flow rate of the fuel mixture (Q_R(t)) is measured with the aid of a hot-film mass flow meter.
4. Method according to Claim 1,
   wherein, during the starting (restarting) of the boiler, the back- pressure which is applied to the boiler (100) is measured, and a rotational speed (VR) which supplies the required flow rate (Q_R(t)) is imposed on the fan (130) whilst taking into account the back-pressure which is applied to the flow of the fuel mixture (VM) and is measured before the boiler (100) is started.
5. Method according to Claim 1,
   wherein it is implemented in the form of a program which is recorded in the memory (152) of the control circuit (150) which controls the operation of the boiler (100).
6. Condensing boiler which comprises a heating body (140) which supplies the heat to a consumer circuit (200) by burning a flow of a fuel mixture which is supplied by a controlled fan (130), which receives the fuel mixture from a metering device (110) which ensures the metered mixing of the fuel gas and the combustion air,
   wherein the boiler comprises a control circuit (150) which manages the operation of the boiler (100) and, in order that it is brought to safety, is connected to a device for measuring the flow rate (122, 123) of the flow of the fuel mixture (VM) which is supplied by the fan (130) to the heating body (140), in order to regulate the motor (131) of the fan (130) in order to supply the flow rate (Q_R(t)) of the fuel mixture equal to the target flow rate (Qc(t)) which is required for the heating body (140), whatever the variations in the pressure loss which are imposed on the flow of the fuel mixture (VM).
7. Boiler according to Claim 6,
   wherein it comprises a device for measuring the instantaneous flow rate of the flow of the fuel mixture (VM), which is formed by two pressure sensors (122, 123) which are installed in a mixing chamber (120) which receives the metered mixture of gas and combustion air, and comprises a non-return valve (121) which opens in the direction of the passage of the flow of the fuel mixture in the direction of the fan (130) and closes for the converse direction, wherein the two pressure sensors (122, 123) are installed on the two sides of the valve (121) in order to measure a pressure difference, which makes it possible to calculate the flow rate (Q_R ^(H)) of the flow of the fuel mixture.
8. Boiler according to Claim 6,
   wherein it comprises a device for measuring the instantaneous flow rate (Q_R(t)) of the flow of the fuel mixture, which is formed by a hot-film flowmeter which is installed in the passage of the fuel flow, in particular upstream of the fan (130) .
9. Boiler according to Claim 6,
   wherein it comprises a pressure sensor (123) which, as the boiler is stopped, measures the back-pressure which is imposed on the latter by the circuit of the flow of the fuel mixture and the waste gases.
10. Boiler according to Claim 9, wherein the pressure sensor (123) which is installed in the mixing chamber (120) downstream (120B) of the non-return valve (121) forms a pressure sensor which supplies the measurement of the back-pressure.

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