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).

Claims

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 (T1) of the pulses with respect to the duration (T2) 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Further characteristics and advantages of the present invention will, in any case, be evident from the description given below of its preferred embodiments, made by way of a non-limiting example with reference to the appended drawings, wherein:

[0048] FIGS. 1 and 2 show two voltage waveforms at fixed frequency for powering an electric pump for a heater, according to the prior art;

[0049] FIG. 1A shows a typical pressure-flow trend of an electric pump;

[0050] FIGS. 3, 4 and 5 show details of voltage supply trends for an electric pump for a heater, according to the present invention;

[0051] FIG. 6 shows a schematic view of a heater according to the invention;

[0052] FIG. 7 is a block diagram of the heater in FIG. 6.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS

[0053] With reference to the figures, reference numeral 100 globally denotes a liquid fuel portable heater according to the invention.

[0054] In this description, the pulse sequence of the pump power supply is also sequence of power intervals, or sequence of ON.

[0055] Consequently the duration of the pulse is the duration of the power interval and also the ON duration.

[0056] Similarly, the pause intervals are also called non-powered intervals or OFF intervals.

[0057] In addition, the interval in which the heater is switched on and thus the interval during which liquid fuel is dispensed from the nebulizer into the combustion chamber and in which combustion takes place will also be referred to as the heater operative interval,

[0058] In this description, the liquid fuel is sometimes referred to as fuel.

[0059] The heater 100 comprises a combustion chamber 101, for example of a substantially tubular shape, into which a liquid fuel, or fuel, such as diesel fuel, in the form of aerosol 15, in particular as a nebulised mixture of fuel and air, is conducted.

[0060] The heater 100 thus comprises a nebulizer 13 to form the fuel aerosol and to continuously nebulise it into the combustion chamber 101, in which a flame 16 is generated. Nebulisation is performed upon reaching a predefined fuel pressure upstream of a nebulizer nozzle.

[0061] Outside and around the combustion chamber a casing 102, or skirt, may be present forming an interspace 103 around the combustion chamber 101, suitable to be crossed by a flow of air 104 which thermally insulates the combustion chamber from the outer casing, and simultaneously heats and forcibly enters an environment to be heated.

[0062] To form such forced flow of air 104 a fan 105 placed upstream of the nebulizer 13 and interspace 103 may be used. Part of said flow may be diverted into the combustion chamber 101 to provide combustion air for combustion.

[0063] The fan 105 is driven by an electric motor 105.

[0064] According to one embodiment, the heater comprises a tank 6 placed on board the heater, in particular under the combustion chamber housing 101 or casing 102.

[0065] A frame, not shown in the drawings connects and joins all the components of the heater 100, so as to move it easily in one body.

[0066] The heater may comprise wheels 7 positioned to facilitate its movement.

[0067] The heater 100 further comprises an electric pump 10 having an inlet 11 for receiving the fuel from the tank 6, and an outlet 12 to send said liquid fuel to the nebulizer 13 in input to the combustion chamber 101.

[0068] As shown in FIG. 7, the heater comprises a supply duct 43 of the fuel which connects the tank 6 to the pump 10, to transfer to the pump 10 the fuel 44 contained in the tank 6.

[0069] A supply duct 45 fluidically connects the pump 10 to the nebulizer 13.

[0070] A compensation duct 46 fluidically connects the supply duct 45 to the expansion chamber 14.

[0071] According to one embodiment, the heater 100 further comprises an electricity source 24, in particular mounted on board and thus integrated in the heater. This electricity source is dimensioned to supply electricity to all the electrical components on board, such as the pump 12, a control unit, a motor 105 of the fan 105, circuit boards, solenoid valves.

[0072] According to one embodiment, the electricity source is an electric battery, or storage battery for example a rechargeable battery.

[0073] According to one embodiment, the heater 100 comprises at least one direct conversion cell of a temperature differential into electric energy (not shown) mounted on the heater 100 to receive a temperature differential between the inside of the combustion chamber and the outside environment, in which said electricity produced by said at least one conversion cell is suitable to electrically power said electric pump and said control unit 20.

[0074] For example, the at least one direct conversion cell is a Seebeck cell.

[0075] According to one embodiment the heater comprises a Stirling motor positioned to take the temperature differential between the combustion chamber and the environment and convert it into mechanical energy, for example to drive an electricity generator.

[0076] The heater 100 comprises a control unit 20 configured to power the electric pump, or control an electricity supply of the pump, with the heater 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. In particular, such average durations are evaluated for the same operative interval of the heater.

[0077] According to an embodiment, the average duration of the pulses 115, 115 is preferably less than of the average duration of the pause intervals 116, or, even more preferably less than half the average duration of the pause intervals 116.

[0078] In this context, the average duration of the pulses is understood as the quotient of the sum of the durations of all the pulses and the total number of pulses in the operative interval of the heater.

[0079] Similarly, the average duration of the pause intervals is understood as the quotient of the sum of the durations of all the pause intervals and the total number of pauses in the operative interval of the heater.

[0080] In other words, the control unit 20 is configured to control an electricity supply of the electric pump 10, with the heater on, in a sequence of power intervals 115 having an ON duration of T1, and non-powered intervals 116 having an OFF duration of T2, wherein the sum of the durations of the ON intervals T1 is less than the sum of the durations of the OFF intervals T2 in the operative interval of the heater.

[0081] Some possible examples of voltage trends V as a function of time t to power the pump 10, according to the invention, are shown in FIGS. 3, 4 and 5, while FIGS. 1 and 2 show possible electric voltage trends as a function of time using a traditional power supply. Along the x-axis 121 is the time, and along the y-axis 122 the electrical voltage is shown.

[0082] In particular, the prior trend shown in FIGS. 1 and 2, with a sinusoidal waveform in FIG. 1 and with a square waveform in FIG. 2, is at fixed frequency and maximum constant voltage, for example at 50 Hz and has a duty cycle of approximately 50%.

[0083] The provision of reducing the on duration compared to the OFF time reduces the duty cycle and thus the electricity absorbed by the pump compared to that traditionally used.

[0084] In other words, according to an embodiment, the control unit 20 is configured to adjust, or modulate, the ON duration compared to the OFF duration to obtain a duty cycle of less than 50%.

[0085] In other words again the duty cycle value, or percentage value of the integral of a voltage/time curve of said sequence of pulses in an operative interval of the heater with respect to the integral of a 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 in the same operative interval of the heater, is less than 50%.

[0086] According to an embodiment, the control unit 20 is configured to adjust, or modulate, the ON duration compared to the OFF duration, or, in other words, the duration T1 of the pulses compared to the duration T2 of the pause intervals, to obtain a duty cycle, with a value of less than 40%, in particular less than 30%, for example less than 20%. Experimental tests have shown particularly favourable behaviour of the pump at such values of the duty cycle.

[0087] According to an embodiment, the control unit 20 is configured to adjust, or modulate, the ON duration compared to the OFF duration to obtain a duty cycle, with a value between 10% and 40%, for example between 20% and 30%.

[0088] According to a preferred embodiment, the control unit 20 is configured to perform a duty cycle of about 12%. At this value of duty cycle, it has been found that the power absorbed by the pump, although advantageously greatly reduced in value, allows the supply of an adequate fuel flow and pressure for nebulisation through the nebulizer 13.

[0089] According to an embodiment, the control unit 20 is configured to adjust the frequency of the sequence of actuation intervals of the pump 210, 211, 212 in the operative interval of the heater, especially at frequency values below 50 Hz.

[0090] This makes it possible to further reduce the power absorbed by the pump 10. In fact, reducing the frequency of the supply portions, or sequence of pulses, means further reducing the area under the curve in the operative interval of the heater and thus reducing the energy absorbed by the pump. Said reduction of the frequency, in conjunction with the reduction in the average duration of the pulses compared to the average duration of pause intervals, allows very high energy savings to be achieved.

[0091] According to an aspect of the invention, the control unit is configured to adjust, or reduce the frequency of the pulse sequence, to values between 10 Hz and 40 Hz, for example between 10 Hz and 30 Hz, preferably to about 10 Hz. Experimental tests have shown particularly advantageous results in terms of energy saving by reducing the frequency of the pulse sequence to the above values. In fact in said pulse frequency ranges, in conjunction with the reduction in the average duration of the pulses compared to the average duration of the pause intervals, there is an evident reduction of electricity consumption while continuing to provide a fuel flow and pressure suitable for proper operation of the heater.

[0092] The optimum operating conditions occur at a supply frequency of approximately 10 Hz. In such conditions the power absorbed by the pump is minimal but still permits the supply of a fuel pressure to the nebulizer, above the minimum nebulisation pressure, thus permitting an optimal nebulisation.

[0093] Such duty cycle and frequency values can be modulated jointly or separately, this way it is possible to achieve the best performance balance in relation to the type of pump used, with the least consumption of electricity.

[0094] However, the combination thereof permits the maximum energy saving.

[0095] In fact, a pump suitable to be powered at a frequency of 50 Hz with a duty cycle of 50% resulting in a power consumption of 24 W, is still able to provide sufficient flow and pressure of the fuel to the nebulizer if powered at a frequency of 10 Hz with a duty cycle of 12%, leading to the optimal result of a consumption of just 5.7 W. This is an energy saving so high that it doubles the power reserve of the heater if running on battery, or halves the size if powered by a Seebeck cell.

[0096] According to an embodiment, the control unit 20 is configured to modulate the ON duration T1 compared to the OFF duration T2 of each period T so as to provide sufficient liquid fuel to the nebulizer 13 at a pressure not lower than a predefined minimum threshold of nebulisation pressure.

[0097] In particular, said minimum threshold is about 8 bar.

[0098] According to an embodiment, the control unit 20 is configured to modulate the frequency of said sequence 210, 211, 213 in the time unit so as to supply the liquid fuel to the nebulizer 13 at a pressure not lower than said predefined minimum threshold of nebulisation pressure.

[0099] According to an embodiment, the control unit 20 is configured to vary over time the duration of the individual power intervals having an ON duration T1, and the ratio between the duration of each power interval and an OFF duration T2 of the interval that precedes and/or follows the power interval, and/or to vary the frequency of said sequence 210, 211, 213 over time, for example in a differentiated manner from one period to another, for example to compensate for any variations in the flow demand by the nebulizer and any variations in the flow, in order to ensure a uniform and constant flame over time.

[0100] According to an embodiment, the control unit 20 comprises a closed loop control with feed-back on the fuel pressure measured upstream of the nebulizer. In this case the control unit is configured to automatically modulate the ON duration T1 and OFF duration T2 of each period T, and to modulate the frequency of the actuation intervals in the unit of time, so that the pressure measured upstream of the nebulizer is substantially equal to a predefined set-point value, for example not less than the predefined minimum threshold of nebulisation pressure.

[0101] Furthermore, according to an embodiment, the heater 100 may comprise pressure sensors, or pressure gauges 39 arranged to detect the pressure value of the fuel upstream of the nebulizer, and, for example, to send the corresponding information to the closed loop control.

[0102] Alternatively, the control unit 20 comprises an open control in which the minimum nebulisation threshold value is mechanically set by the characteristics of the nebulizer. In this case the nebuliser permits nebulisation only above said minimum threshold and does not permit nebulisation below said minimum threshold.

[0103] According to an embodiment the nebulizer 13 comprises a calibrated pressure non-return valve 17, for example at the minimum threshold value for nebulisation, and a calibrated nozzle 18.

[0104] This way the nebulizer valve 17 opens only when it reaches the minimum nebulisation threshold. Such a nebulizer prevents the involuntary leakage of fuel when the pressure at the nebulizer is less than the minimum threshold for nebulisation. This makes for considerable safety in use.

[0105] According to an embodiment, the power interval 115 is formed of a single pulse to perform a pumping cycle, or the power interval 115 is formed of plurality of successive electrical pulses close together to perform a corresponding plurality of pumping cycles. In particular, FIG. 3 shows an example of a power interval 115 consisting of a single electrical pulse 115, while FIGS. 4 and 5 show examples of a power interval 115 consisting of 3 pulses 115.

[0106] In other words, the sequence of pulses to power the pump may comprise a plurality of successive electrical pulses 115 close together, for example, to perform a corresponding plurality of pumping cycles.

[0107] In general a number of pulses may be used such as to generate a flow rate and fuel pressure such as to permit a continuous and uniform nebulisation to the nebulizer.

[0108] According to an embodiment, said or each pulse of said power interval 115 may be in the form of a sinusoidal waveform or a square waveform.

[0109] According to an embodiment, the pump 20 is a reciprocating pump such as a piston.

[0110] According to an embodiment, such piston pump comprises a cylinder and a piston sliding inside the cylinder so as to push out the fuel in a pulsed manner towards the nebulizer. Outside the cylinder a solenoid is wound which, when crossed by electric current, generates an electromagnetic field which moves the piston between a first and a second end stroke position. In the movement from the first end stroke position to the second end stroke position the piston pump sucks the fuel from the tank, while in the opposite stroke, from the second end stroke position to the first end stroke position it pushes the fuel to the nebulizer 13.

[0111] In a preferred embodiment, the piston pump comprises a spring configured to return the piston from the first end stroke position to the second end stroke position at the end of the dispensing phase.

[0112] In other words, such a piston pump provides for an active phase in which the solenoid is electrically powered, in which the piston moves from the second end stroke position to the first end stroke position, pushing the fuel to the nebulizer under pressure, and a passive return phase in which the piston moves backwards from the first end stroke position to the second end stroke position, in which the solenoid is not powered and the spring returns the piston to the second end stroke position performing the suction phase of the fuel.

[0113] With reference to FIGS. 3 and 4 showing the voltage trend applied to the pump, in this case to the solenoid, the active phase is represented by the portion of the pulse 115 ranging from the minimum value of the potential, or voltage, to the maximum value of the potential, or voltage, and by the portion, while the passive phase corresponds to the pulse portion 115 which goes from the maximum value to the minimum value of the potential.

[0114] According to an alternative embodiment, the pump 10 may be a reciprocating pump diaphragm, so as to compensate abrupt pressure variations.

[0115] Again in an alternative embodiment, the pump 10 may for example be a gear or vane rotary pump. In this case, an example of a power supply voltage trend of the pump is shown in FIG. 5.

[0116] In general, the pump 10 may comprise an electrical actuator 10 and a mechanical pumping apparatus 10 mechanically connected to the actuator 10 so that said actuator 10 operates the mechanical pumping apparatus 10 to pump the fuel.

[0117] The electric actuator 10 transforms the incoming electricity into motion which is provided to the pumping apparatus.

[0118] The pumping apparatus 10 is selected from the normal existing types of devices such as piston, diaphragm, gear, vane.

[0119] The control unit 20, according to an embodiment of the invention, comprises a current controller 31 and a timer 32, wherein said current controller 31 is configured to generate in output said power interval 115 having an ON duration T1, for example having a square or sinusoidal waveform, for example said power interval comprising a single pulse 115 or a plurality of pulses 115 side by side and close to each other, and wherein said timer 32 adjusts said pause interval 116, or OFF interval, having an OFF duration T2.

[0120] According to an embodiment, the heater 100 comprises a switch 33 electrically interposed between the electricity source 24 and the electric pump 10, and in addition or alternatively, between the electricity source 24 and the control unit 20. For example the switch 33 is arranged to allow/prevent the power supply of the pump 10 and the control unit 20 simultaneously.

[0121] According to an embodiment, the control unit 20 and the switch 33 are integrated on the same circuit board 37.

[0122] According to an embodiment, the heater 100 further comprises electronic control devices 34, 35 to control further electrical devices 36, 36, 36 placed on board the heater, such as fans 105 to generate a forced flow of air, or solenoid valves for the fuel.

[0123] According to an embodiment, said electronic control devices 34, 35 are integrated on said circuit board 37.

[0124] According to an embodiment, the heater comprises an expansion chamber 14 in fluidic communication with the fuel between the outlet 12 of the pump 10 and the nebulizer 13. Said expansion chamber 14 is suitable to store excess fuel gradually with respect to a fuel flow actually passing through the nebulizer during the powering of the pump at the electrical pulses 115. Likewise, the expansion chamber is suitable to gradually release the excess fuel to the nebulizer 13 during the pause intervals, providing a continuous delivery of fuel through the nebulizer during an entire operative interval of the heater.

[0125] The predefined minimum threshold of nebulisation is for example about 8 bar.

[0126] According to an embodiment, the expansion chamber 14 is a closed chamber of variable internal volume in fluidic connection with the pressurised fuel upstream of the nebulizer 13, suitable to expand containing a larger amount of fuel when the fuel pressure increases, and suitable to be compressed to release said fuel when the pressure decreases.

[0127] According to an embodiment, the heater comprises a rigid container 51 divided into two variable volume chambers, of which a first chamber 52 is formed of said expansion chamber 14, and a second chamber 53 contains a compressible material, such as a gas, so that when the expansion chamber 14 expands, said second chamber 53 is compressed accordingly, in particular exerting an additional pressure against the expansion chamber 14.

[0128] In other words the expansion chamber 14 serves as a temporal volumetric reserve of pressurised fuel performing two tasks together.

[0129] In fact, said expansion chamber 14 performs a first task acting as a flow equalizer, i.e. as a deposit and reserve of the excess flow of fuel dispensed by the pump in the active ON phase, enabling the continuous dispensing of fuel towards the nebulizer during the OFF phase of the pump.

[0130] In addition, said expansion chamber 14 performs a second task by acting as a pressure equalizer, i.e. damping the pressure peaks in the fuel circuit downstream of the pump.

[0131] The presence of said expansion chamber 14 compensates a possible fluctuating trend of peaks and dips of the fuel pressure downstream of the pump, due to the alternate operation of the pump, for example of the piston pump. This way, moreover, the risk of non-nebulisation and consequent involuntary extinguishing of the heater is avoided. The presence of the expansion chamber also makes it possible to avoid the phenomenon known as pipe hammer inside the fuel ducts in the portion between the pump and the nebulizer, caused by the rapid pressure drop occurring at the end of the active phase of powering the pump.

[0132] When the pump 10 is started, the fuel fills the expandable container up to a minimum nebulisation threshold value at which the nebulizer works, after which the fuel begins to flow from the nebuliser. At each pulse of the pump, a first part of the volume of fuel contained in the expandable container flows through the nebulizer, and a second part of said volume is stored in the expandable container in order to ensure the flow in the OFF phase.

[0133] According to another aspect of the present invention, the aforesaid purposes and advantages are achieved by a method for controlling the power supply of an electric pump for a liquid fuel portable heater.

[0134] The method for controlling an electric power supply of an electric fuel pump 10 for a liquid fuel portable heater by means of an electric control unit 20 configured to power the pump, comprises a step of controlling said power supply, with the heater 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.

[0135] According to an embodiment, the method comprises a step of adjusting the duty cycle value, or percentage value of the integral of a voltage/time curve of said sequence of pulses in an operative interval of the heater with respect to the integral of an 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 in the same operative interval of the heater, so that said duty cycle value is less than 50%.

[0136] In particular, the on duration T1, or pulse duration, and the off duration T2, or duration of the pause interval, are chosen so as to ensure a continuous supply of fuel to the nebulizer.

[0137] 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.

[0138] According to an embodiment, the method comprises a step of modulating the ON duration T1 compared to the OFF duration T2 of each period T so as to provide the liquid fuel to the nebulizer 13 at a pressure not lower than a predefined minimum threshold of nebulisation pressure.

[0139] According to an embodiment, the method comprises a step of modulating the frequency of said sequence of pulses in the time unit so as to supply the liquid fuel to the nebulizer 13 at a pressure not lower than said predefined minimum threshold of nebulisation pressure.

[0140] According to an embodiment, the control method comprises a step of varying over time the duration of the pulses with respect to the duration of the pause intervals, so as to supply the liquid fuel to the nebulizer 13 at a pressure not less than a predefined minimum threshold of nebulisation pressure.

[0141] According to an embodiment the control method comprises a step of varying over time the frequency of the sequence of pulses so as to supply the liquid fuel to the nebulizer 13 at a pressure not less than a predefined minimum threshold of nebulisation pressure.

[0142] A person skilled in the art may make modifications and adaptations to the embodiments of the device described above, replacing elements with others functionally equivalent so as to satisfy contingent requirements while remaining within the sphere of protection of the following claims. Each of the characteristics described as belonging to a possible embodiment may be realised independently of the other embodiments described.