Device for the delivery of a combustible gaseous mixture and procedure

Abstract

The present invention describes a device for delivering a combustible gaseous mixture (M) comprising a first duct for feeding air (A) and a second duct for feeding a gaseous fuel (G), which join in a mixing zone, in which the gaseous fuel (G) and air (A) mix according to a lambda coefficient (λ) before being sent to a burner, a ventilation device for feeding the air (A) and at the same time suctioning gaseous fuel (G) along said ducts, and means for regulating the flow rate of gaseous fuel (G). The invention also concerns a method to use a device for controlling the delivering of a combustible gaseous mixture (M).

What is claimed is: 
     
         1 : A device for delivering a combustible gaseous mixture (M) comprising:
 first and a second ducts configured for feeding air (A) and a gaseous fuel (G) respectively, which join in a mixing zone, mixing said gaseous fuel (G) and air (A) according to a predefined lambda coefficient (k) before they are sent to a burner;   a ventilation device configured for feeding the air (A) and the gaseous fuel (G);   a gaseous fuel regulator configured for regulating a flow rate of the gaseous fuel (G);   a first sensor configured for measuring a flow rate of the air (A) along said first duct;   at least two second sensors configured for measuring an air/fuel pressure ratio, the at least two second sensors being connected between said first and second ducts; and   a control unit configured to implement a procedure for the automatically recalibrating said sensors and for processing data supplied by said first and second sensors;   the controller being further configured to control said ventilation device and said gaseous fuel regulator at least in order to keep said lambda coefficient (λ) within predefined intervals (I 1 , I 2 ).   
     
     
         2 : The device of  claim 1 , characterized in that said first sensor is a flow sensor selected from a differential pressure sensor and a thermomassic sensor, located between two terminals disposed in correspondence with said first duct respectively before and after a reduced cross section thereof, and in that said at least two second sensors are flow sensors of the thermomassic type each comprising two terminals disposed respectively in correspondence with the first and second ducts. 
     
     
         3 : The device of  claim 1 , wherein the device further comprises a speed sensor configured for measuring an actual rotation speed of said ventilation device, and said control unit is configured to process data supplied at least by said first sensor and said speed sensor in order to control in real time a quantity of the air (A) that is fed to the burner and to keep a parameter (K), given by a ratio between said flow rate of the air (A) and said actual rotation speed, approximately equal to an initial value (K 0 ). 
     
     
         4 : The device of  claim 1 , characterized in that said speed sensor is a Hall effect sensor connected to said ventilation device. 
     
     
         5 : A method of delivering a combustible gaseous mixture (M), the method comprising:
 feeding, by a gaseous fuel regulator and a ventilation device respectively, air (A) in a first duct and a gaseous fuel (G) in a second duct which joins said first duct in a mixing zone which is able to mix the gaseous fuel (G) and air (A) according to a predefined lambda coefficient (λ) before they are sent to a burner;   measuring a flow rate of the air (A) along said first duct by a first sensor;   measuring an air/fuel pressure ratio between said first and second ducts by at least two second sensors connected between said first and second ducts;   executing a recalibration procedure that automatically recalibrates said first and second sensors;   detecting data by said first and second sensors; and   processing said data in order to control said ventilation device and said gaseous fuel regulator at least in order to keep said lambda coefficient (λ) within predefined intervals (I 1 , I 2 ).   
     
     
         6 : The method of  claim 5 , wherein said calibration procedure is performed on a basis of measurements of all of said first and second sensors measuring flow rates of air that passes through said first and second sensors. 
     
     
         7 : The method of  claim 5 , wherein said recalibration procedure includes:
 keeping a valve device closed in order to stop a flow of the gaseous fuel (G), and   performing said measurements of all of said first and second sensors substantially simultaneously;   performing a verification that verifies whether at least one of said first and second sensors is an uncalibrated sensor that returns a measurement that differs, as a percentage difference, by more than a predefined percentage difference (D 1 ) with respect to the others of the first and second sensors; and
 if only one of the calculated percentage differences is greater than said predefined percentage difference (D 1 ); 
 setting a rotation speed of the ventilation device to a first value and repeating, substantially simultaneously, the measurements of all of said first and second sensors; and 
 performing a recalibration procedure that recalibrates the uncalibrated sensor, said recalibration procedure comprising changing a scale factor of the uncalibrated sensor in such a way that the uncalibrated sensor becomes a calibrated sensor that returns an intermediate value between the others of the first and second sensors. 
   
     
     
         8 : The method of  claim 7 , wherein said recalibration procedure further comprises setting the rotation speed of the ventilation device to a second value and repeating the verification so as to verify that the measurements of all said first and second sensors do not differ from each other by more than said predefined percentage difference (D 1 ). 
     
     
         9 : The method of  claim 8 , wherein said recalibration procedure further comprises setting the rotation speed of the ventilation device to a third value and repeating the verification so as to verify that the measurements of all the first and second sensors do not differ from each other by more than said predefined percentage difference (D 1 ). 
     
     
         10 : The method of  claim 8 , further comprising:
 if any one of the verifications indicates that at least one of said measurements of all the first and second sensors, as a percentage difference, differs from the others of the measurements of all of the first and second sensors by more than said predefined percentage difference (D 1 ), activating a safety shut-off mode; or   if none of the verifications indicates that at least one of said measurements of all the first and second sensors, as a percentage difference, differs from the others of the measurements of all of the first and second sensors by more than said predefined percentage difference (D 1 ), concluding the recalibration procedure with a positive outcome.   
     
     
         11 : The method of  claim 8 , wherein the method comprises, if said percentage differences calculated for the measurements of all of said first and second sensors are all lower than said predefined percentage difference (D 1 ), exiting said recalibration procedure; while if at least two of said calculated percentage differences are greater than said predefined percentage difference (D 1 ), activating a safety shut-off mode. 
     
     
         12 : The method of  claim 5 , wherein said predefined percentage difference (D 1 ) is between 4% and 6%. 
     
     
         13 : The method of  claim 5 , wherein the method comprises activating said recalibration procedure automatically, in a step of preparing to ignite a flame (F) in said burner. 
     
     
         14 : The method of  claim 5 , comprising:
 comparing data values detected by said second sensors;   and   if any difference between the data values detected by said second sensors is higher than a predetermined percentage difference (D 2 ), causing a valve device to stop a flow of the gaseous fuel (G) and performing said recalibration procedure.   
     
     
         15 : The method of  claim 14 , comprising carrying out said comparing of said data values detected by said second sensors at least one of in a step of igniting said flame (F), and periodically or continuously, in an operating step of said burner.