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 delivering a combustible gaseous mixture (M).

What is claimed is: 
     
         1 . A device for delivering a combustible gaseous mixture (M) comprising:
 a first and second duct 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 (λ) before they are sent to a burner;   a ventilation device configured for feeding the air (A) and the gaseous fuel (G);   a gas flow regulator configured to regulate the flow of the gaseous fuel (G);   a first sensor configured for measuring the air (A) flow rate connected to said first duct;   at least one second sensor configured for measuring an air/fuel pressure ratio connected to said first and second ducts;   a speed sensor configured for measuring an actual rotation speed of said ventilation device; and   a control unit configured to process data supplied by said first and second sensors and said speed sensor, and to control said ventilation device and said regulation device in order to keep said lambda coefficient (λ) within predefined intervals (I1, I2) and a parameter (K), given by the ratio between said air (A) flow rate and said actual rotation speed, substantially constant around a certain initial value (K0).   
     
     
         2 . The device as in  claim 1 , characterized in that said first sensor is a thermomassic sensor. 
     
     
         3 . The device as in  claim 1 , characterized in that said first sensor is a differential pressure sensor. 
     
     
         4 . The device as in  claim 1 , characterized in that said first sensor is located between two terminals which are disposed in correspondence with said first duct between an inlet for the air (A) and a narrowing of said mixing zone. 
     
     
         5 . The device as in  claim 1 , characterized in that said at least one second sensor is a flow sensor of the thermomassic type comprising two terminals disposed in said first and second duct, respectively. 
     
     
         6 . The device as in  claim 1 , characterized in that said speed sensor is a Hall effect sensor connected to said ventilation device. 
     
     
         7 . A method of delivering a combustible gaseous mixture (M), the method comprising:
 feeding air (A) in a first duct and feeding 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, by means of a ventilation device and a regulation device, respectively;   wherein the method further comprises:
 measuring an air (A) flow rate along said first duct with a first sensor; 
 measuring an air/fuel pressure ratio between said first and second ducts by at least one second sensor connected to said first and second ducts; and 
 measuring an actual rotation speed of a ventilation device by a speed sensor; 
   processing the data of said air (A) flow rate, said air/fuel pressure ratio and said rotation speed; and
 controlling said ventilation device and said regulation device in order to keep said lambda coefficient (λ) within intervals (I1, I2) of predefined values and a parameter (K), given by the ratio between said air (A) flow rate and said actual rotation speed, substantially constant approximately equal to a certain initial value (K0). 
   
     
     
         8 . The method of  claim 7 , further comprising causing said regulation device to regulate the gas (G) flow rate in such a way that the following relationship is satisfied:
 S1−S2=(Qair/(λ*R)){circumflex over ( )}2/Kg{circumflex over ( )}2 where S1, S2 are the pressure differences measured by said first and second sensors, Qair is the air (A) flow rate, R is a stoichiometric ratio relative to the gaseous fuel (G) used, and Kg is a constant dependent on said regulation means.   
     
     
         9 . The method of  claim 7 , further comprising measuring an initial value of the flow rate (Qair0) of air (A) and an initial value of the rotation speed (RPM0) of said ventilation device, and calculating said certain initial value (K0) given by the ratio between said initial value of the flow rate (Qair0) of air (A) and said initial value of the rotation speed (RPM0). 
     
     
         10 . The method of  claim 9 , further comprising:
 subsequently measuring other values of the flow rate (Q1) of air (A) and of the rotation speed (RPM) of said ventilation device;   calculating said steady state parameter (K) given by the ratio between said other values of the flow rate (Q1) of air (A) and of the speed (RPM); and   verifying that said parameter (K) deviates from the certain initial value (K0) by a quantity lower than a pre-established limit (L).   
     
     
         11 . The method of  claim 8 , further comprising controlling said regulation device in such a way that, in a step of ignition of a flame (F) of said burner, said lambda coefficient (λ) assumes a first value (λ1) within a first interval (I1) and, in a step of normal operation of said burner subsequent to said ignition step, said lambda coefficient (λ) assumes a second value (λ2) within a second interval (I2), wherein said first interval (I1) is approximately between 2 and 5 and said second interval (I2) is approximately between 1.2 and 2. 
     
     
         12 . The method of  claim 8 , further comprising a step of preparing to ignite a flame (F), said step of preparing to ignite the flame (F) comprising:
 receiving a value of a quantity of heat (QC) required, correlated to a temperature set by a user;   determining an air (A) flow rate value that is suitable to achieve said value of quantity of heat (QC) required;   causing said ventilation device to achieve said determined air (A) flow rate value; and   comparing the air (A) flow rate detected by said first sensor with said determined air (A) flow rate value and, if these values match, proceeding with igniting said flame (F).   
     
     
         13 . The method of  claim 12 , further comprising, in the event that said detected air flow rate deviates from said determined air flow rate beyond a certain predefined threshold value, retrying the ignition procedure in a subsequent moment. 
     
     
         14 . The method of  claim 12 , further comprising, in the event that said air (A) flow rate detected by said first sensor does not correspond to the determined air (A) flow rate:
 verifying whether a pre-established time (Ttimeout) for the step of preparing for the ignition has already elapsed;   if Ttimeout has not elapsed, readjusting the number of revolutions of said ventilation device in increments or reductions, and once again determining the air (A) flow rate; and   if Ttimeout has elapsed, switching off said ventilation device and returning to receiving a value of quantity of heat (QC) required.   
     
     
         15 . The method of  claim 9 , further comprising analyzing said data of air (A) flow rate and said rotation speed of the ventilation device and their ratio in order to detect possible anomalies of said burner, or of a pneumatic system associated therewith, during its operation.