Liquid fuel portable heater and control method of said heater

Abstract

A liquid fuel portable heater (100) comprises: a combustion chamber (101) having a fuel inlet with a nebuliser (13); an electric pump (10) having an inlet (11) for suctioning said liquid fuel from a tank (6), and an outlet (12) connected to said nebuliser (13); a control unit (20) configured so that, when the heater (100) is turned on, said control unit (20) supplies the electric pump with a sequence of pulses (115, 115′) with a non-zero voltage, and pause intervals (116) with a substantially zero voltage alternating with said pulses, wherein the average duration of the pulses (115, 115′) is less than the average duration of the pause intervals (116). In addition, a method for controlling an electric power supply of a fuel electric pump (10) of a liquid fuel portable heater by means of an electric control unit (20) configured to control said electric power supply, comprising a step of electrically supplying said pump, once the heater is turned on, with a sequence of pulses (115, 115′) with a non-zero voltage, and pause intervals (116) with a substantially zero voltage alternating with said pulses, wherein the average duration of the pulses (115, 115′) is less than the average duration of the pause intervals (116).

1 . A liquid fuel portable heater ( 100 ), comprising:
 a combustion chamber ( 101 ) having a fuel inlet with a nebulizer ( 13 );   an electric pump ( 10 ) having an inlet ( 11 ) for suctioning said liquid fuel from a tank ( 6 ), and an outlet ( 12 ) connected to said nebulizer ( 13 ) to bring the liquid fuel to the nebulizer ( 13 );   an electric control unit ( 20 ) configured so that, when the heater ( 100 ) is turned on, said control unit ( 20 ) actuates the electric pump by supplying it with a sequence of pulses ( 115 ,  115 ′) with a non-zero voltage, and pause intervals ( 116 ) with a substantially zero voltage alternating to said pulses, wherein the average duration of the pulses ( 115 ,  115 ′) is less than the average duration of the pause intervals ( 116 ).   
     
     
         2 . The portable heater according to  claim 1 , wherein the duty cycle value, or percentage value of the integral of a voltage/time curve of said sequence of pulses ( 115 ,  115 ′) in an operative interval of the heater ( 100 ), with respect to the integral of a hypothetical voltage/time curve with a direct, constant voltage, with a amplitude equal to the maximum amplitude of said voltage/time curve of said sequence of pulses ( 115 ′,  115 ) in the same operative interval of the heater, is less than 50%. 
     
     
         3 . The portable heater according to  claim 1 , wherein said control unit ( 20 ) is configured to adjust a frequency of said sequence of pulses ( 115 ,  115 ′), so that said frequency is less than 50 Hz. 
     
     
         4 . The heater according to  claim 1 , wherein said control unit ( 20 ) is configured so as to vary over time the duration (T 1 ) of the pulses with respect to the duration (T 2 ) of the pause intervals, so as to provide the liquid fuel to the nebulizer ( 13 ) at a pressure that is not less than a predetermined minimum threshold of nebulisation pressure. 
     
     
         5 . The heater according to  claim 1 , wherein said control unit ( 20 ) is configured to vary over time the frequency of the sequence of pulses ( 115 ,  115 ′) so as to provide the liquid fuel to the nebulizer ( 13 ) at a pressure that is not less than a predetermined minimum threshold of nebulisation pressure. 
     
     
         6 . The heater according to  claim 1 , wherein said sequence of pulses ( 115 ,  115 ′) comprises a plurality of electric pulses ( 115 ′) that are successive and close together, in particular to carry out a corresponding plurality of pumping cycles. 
     
     
         7 . The heater according to  claim 1 , comprising an expansion chamber ( 14 ) in flow communication with the liquid fuel, interposed between the outlet ( 12 ) of said pump ( 10 ) and said nebulizer ( 13 ), said expansion chamber ( 14 ) being configured to store an excess amount of liquid fuel with respect to a flow rate of liquid fuel passing through the nebulizer, said excess amount of liquid fuel being generated during an electric power supply of the pump at the electric pulses ( 115 ), and being configured to gradually release said excess amount of liquid fuel to the nebulizer ( 13 ) during the pause intervals ( 116 ), providing a continuous dispensing of liquid fuel through the nebulizer during an entire operative interval of the heater. 
     
     
         8 . The heater according to  claim 1 , comprising at least one conversion cell ( 95 ) for the direct conversion of a temperature differential into electric power, said at least one conversion cell ( 95 ) being mounted at the heater ( 100 ) to receive a temperature differential between the combustion chamber ( 101 ) and the outer environment, said at least one conversion cell ( 95 ) being connected to electrically supply said electric pump and said control unit ( 20 ). 
     
     
         9 . A method for controlling an electric power supply of a fuel electric pump ( 10 ) of a liquid fuel portable heater by an electric control unit ( 20 ) configured to control said electric power supply, said method comprising a step of electrically supplying said pump, once the heater is turned on, with a sequence of pulses ( 115 ,  115 ′) with a non-zero voltage, and pause intervals ( 116 ) with a substantially zero voltage alternating to said pulses, wherein the average duration of the pulses ( 115 ,  115 ′) is less than the average duration of the pause intervals ( 116 ). 
     
     
         10 . The method according to  claim 9 , comprising a step of adjusting the duty cycle value, defined as the percentage value of the integral of a voltage/time curve of said sequence of pulses ( 115 ,  115 ′) in an operative interval of the heater ( 100 ), with respect to the integral of an hypothetical voltage/time curve with a direct, constant voltage with an amplitude equal to the maximum amplitude of said voltage/time curve of said sequence of pulses ( 115 ,  115 ′) in the same operative interval of the heater, so that said duty cycle value is less than 50%. 
     
     
         11 . The method according to  claim 9 , comprising a step of adjusting the frequency of said sequence of pulses ( 115 ,  115 ′), so that said frequency of the sequence is less than 50 Hz. 
     
     
         12 . The method according to  claim 9 , comprising a step of varying over time the duration of the pulses ( 115 ,  115 ′) with respect to the duration of the pause intervals ( 116 ), and/or varying over time the frequency of the sequence of pulses ( 115 ,  115 ′) so as to provide the liquid fuel to the nebulizer ( 13 ) at a pressure  20  that is not less than a predetermined minimum threshold of nebulisation pressure.