JPH0311366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid fuel combustion device that evaporates fuel using a vaporizing surface.

Conventional configuration and its problems Conventionally, this type of liquid fuel combustion device had a heater embedded in the lower part of the carburetor, and the side wall of the carburetor had a ventilation passage connected to a ventilation fan and the tip formed a nostle. The fuel capillary is connected to the fuel pump and exposed. A combustion tube is provided at the top of the carburetor.

A temperature sensor (thermistor, etc.) is embedded in the vaporizer to control the heater. With this configuration, during combustion, the carburetor is heated by the combustion gas and conductive heat from the combustion flame. This heating amount is
It increases or decreases depending on changes in combustion amount, passages, and heat receiving configuration.
Also, when the temperature of the vaporizer was not sufficient, a temperature detector was activated and the heater was energized to maintain a constant temperature.

Therefore, even when the amount of combustion increased or decreased, the wall surface of the carburetor was kept at a constant temperature. For this reason, when the amount of combustion is small, the amount of heat of vaporization that the fuel receives from the wall surface is small, so the fuel temperature during the evaporation process becomes high, the fuel forms a ball, and the evaporation rate slows down. It produced pulsation, odor, and fire. In addition, when the amount of combustion increases, conversely, because the amount of fuel is large, the amount of heat of vaporization increases, and the fuel absorbs a lot of heat from the wall surface, so the temperature gradient between the vaporization wall surface and the fuel becomes large, and the temperature of the wall surface becomes high. Despite this, the temperature of the fuel was low, resulting in fuel pools due to delayed evaporation and tar generation due to fuel decomposition. As a result, the vaporization was delayed, resulting in sloppy combustion, the outflow of unburned gas, and odor, and the generation of tar, which made it impossible to control the combustion, creating dangers such as flames and standing flames, and making it unusable for a long period of time.

Purpose of the Invention The purpose of the present invention is to stabilize and maintain combustion.

Structure of the Invention The present invention sets the set temperature of the vaporizer temperature detection means of the vaporizer in which the fuel evaporates to be high when there is a large amount of liquid fuel.
Also, when the amount is low, the evaporation rate is increased by changing the set temperature to a low value, thereby stably producing combustion without causing a vaporization delay.

Description of examples Hereinafter, an explanation will be given based on one embodiment of the present invention.

In FIG. 1, a heater 2 is embedded in the circumferential direction at the lower side of a bottomed vaporizer 1, and a mixing plate 3 having a diaphragm shape is attached to the open surface. Further, a blower fan 5 is provided on the side circumferential wall of the carburetor 1 via a blower passage 4, and a thin fuel tube 6 whose tip constitutes a nozzle is passed through the blower passage 4 to face the carburetor 1 from an air guide 7. The other end of this fuel thin tube 6 is connected to a fuel tank 9 via a fuel pump 8. In the upper part of the vaporizer 1, along the circumferential direction, there is provided a rectifying cylinder 11 having a large number of pores 10 and formed into a cylindrical shape, and a rectifying space 12 provided around the rectifying cylinder 11. A combustion tube 14 made of a combustion wire mesh 13 is provided, and this combustion tube 14 has a closing plate 15.
The upper end is closed by Further, an outer cylinder 17 is provided around the combustion cylinder 14 through a combustion space 16 whose one end is closed by a closing plate 15. The outlet 21 provided in the outlet forms a passageway for flowing out to the outside.

A temperature detector 20 (such as a thermistor) for detecting temperature is embedded in the wall surface 19 of the vaporizer 1 to control whether the heater 2 is turned on or off. That is,
When the amount of combustion is small, the operating setting value of the temperature detector 20 is set to 280 to 320°C, and it is increased as the amount of combustion increases, and when the amount of combustion is large, the operating setting value of the temperature sensor 20 is The temperature shall be 380-450℃. In other words, the control means 22 controls the input to the heater 2 after receiving an output from a comparison between the temperature detected by the temperature detector 20 and the set temperature, which is high when the combustion amount is large and low when it is small. Further, the shape, material, and passage area of each component are set so that the amount of heat received by the vaporizer 1 from the combustion gas is greater than the amount of heat received by the vaporization chamber 1 from the combustion flame.

With this configuration, the vaporizer 1 is heated by energizing the heater 2 in the vaporizer 1.
Thereafter, by driving the blower fan 5 provided through the blower passage 4, combustion air is introduced into the carburetor 1 from the air guide 7. Next, fuel is sucked from the fuel tank 9 by driving the fuel pump 8, and the fuel flows from the tip nozzle of the fuel tube 6.
It is ejected into the vaporizer 1. The ejected fuel becomes granular and collides with the wall surface 19 of the carburetor 1, receives heat from the high-temperature wall surface 19, becomes vaporized gas, passes through the constriction part of the mixing plate 3 disposed above, and flows into the combustion tube 14. At this time, the vaporized fuel gas is mixed with combustion air, flows outward from the periphery of the combustion tube 14 equipped with a wire mesh as a premixture, and is ignited in the combustion space 16 between the outer tube 17 and the combustion tube 14. vessel (not shown)
ignition, and a combustion flame is formed on the surface of the combustion wire mesh 13.

In this case, the carburetor 1 is heated by the combustion gas that diffuses from the combustion space 16 to the outside through the jet port provided in the support tube 18 through the side surface of the carburetor 1, and by the conductive heat from the combustion flame. The amount of heating heat increases or decreases depending on changes in combustion amount, passages, and heat receiving configuration. That is, the temperature of the combustion gas increases as the amount of combustion increases, and the amount of heat received by the vaporizer 1 increases. On the other hand, as the amount of heat conducted from the combustion flame increases, the flame moves farther away from the flame mouth, and the temperature near the flame mouth decreases. Therefore, as the amount of combustion increases, the amount of heat received by the carburetor 1 decreases. Therefore, by controlling the amount of heat received by both, when the amount of combustion is small, the temperature of the wall surface of the carburetor 1 is set to about 300℃, and when the amount of combustion is large, the temperature of the wall surface of the carburetor 1 is set to about 450℃. It is configured. In addition, when the heat feedback to the vaporizer 1 due to combustion is not sufficient, the temperature sensor 20
is detected and the temperature is raised by the heater 2 until it reaches a set value corresponding to the combustion amount. Figure 2 shows trends in evaporation rate and vaporization surface temperature due to changes in fuel combustion amount (fuel vaporization amount). The evaporation rate of fuel on the high-temperature wall surface increases in proportion to the rise in wall temperature;
When a certain temperature is reached, the fuel forms a ball and fuel gas accumulates between the fuel and the wall, reducing heat transfer and reducing the evaporation rate regardless of the rise in wall temperature. That is, there is a transition from nuclear boiling evaporation to film boiling evaporation. As the temperature further increases, the rate of evaporation increases. In order to stabilize the ratio of fuel to air and prevent tar formation and accumulation, it is desirable that the evaporation rate be as fast as possible without causing any evaporation delay. However, since it is a fuel,
Excessively high temperatures may cause ignition. As is clear from Fig. 2, when the amount of combustion is small, the amount of heat of evaporation is small, so the temperature rise of the entire fuel is uniformly high, and the evaporation rate peaks when the wall surface temperature is around 250°C. Conversely, when the amount of combustion is large, the amount of heat of vaporization of the fuel is large, so a temperature gradient occurs in the thickness direction of the fuel, and the wall surface temperature becomes lower than the inside of the wall. Therefore, the overall temperature of the fuel will be lower than the wall surface temperature,
The evaporation rate peaks when the wall temperature is around 400℃.
As can be seen from this, by controlling the wall surface temperature up and down according to the amount of combustion, vaporization can always be carried out at the peak of the evaporation rate. As a result, the fuel evaporates quickly, eliminating the generation of combustion drips, odors, and smoke due to delayed evaporation, and preventing the generation and accumulation of tar. By providing the temperature sensor 20 near the vaporizing surface of the vaporizer 1 where the fuel directly hits and evaporates, the set temperature can always be optimally controlled. In addition, the above set temperature is continuously increased in accordance with the increase in the amount of liquid fuel burned.
Further, by setting the temperature at a low value when the temperature decreases, the set temperature can always be maintained at the temperature at which the vaporization rate is the fastest even when the combustion amount increases or decreases depending on the load.

Effects of the Invention The present invention increases the evaporation rate by setting the temperature detection means of the fuel vaporizer high when there is a lot of liquid fuel and low when there is little liquid fuel. It can be used for a long time without causing abnormal combustion (soot generation, standing yellow flame, odor) due to imbalance in the ratio, and without misfires or fuel stagnation caused by accumulation of tar generated due to delayed vaporization. . Furthermore, the stabilization of combustion is
It is possible to expand the variable combustion rate, improving load controllability and increasing comfort and energy savings.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure shows the evaporation rate of fuel. 1... Carburizer, 2... Heater, 5... Blowing fan, 8... Fuel pump, 14... Combustion tube, 2
0...Temperature detector.

Claims (1)

[Claims] 1. A vaporizer having a means for supplying liquid fuel and air, a heating means, and a vaporizer temperature detection means is connected to the combustion section, and the detection output of the temperature detection means is compared with a set temperature to determine the input of the heating means. A liquid fuel combustion device comprising a control means for controlling the temperature, and setting the set temperature high when the liquid fuel is large and low when the liquid fuel is small.