JPH031572B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a vaporizer that vaporizes liquid fuel, mixes it with combustion air, and supplies an air-fuel mixture to a combustion section.

Structure of a conventional example and its problems A conventional vaporizer of this type is shown in FIGS. 1 and 2. A fuel supply pipe 5 and an air supply pipe 6, which are connected to a fuel pump 3 and a combustion fan 4, respectively, are opened in the side wall of a pot-shaped vaporizing cylinder 2 heated by a heater 1. Further, a mixing plate 8 in which a mixture passage 7 is opened and a burner head 10 in which a burner port 9 is formed are arranged at the upper opening of the vaporizing cylinder 2. Tsute vaporization chamber 11
A mixing chamber 12 is defined between the mixing plate 8 and the burner head 10. In the above configuration, the heater 1 is energized to heat the vaporization cylinder 2, and when the temperature reaches a predetermined temperature, the fuel pump 3 and the combustion fan 4 are operated to supply liquid fuel and combustion air to the vaporization chamber 11. The liquid fuel that has entered the vaporization chamber 11 is vaporized on the inner wall surface of the vaporization cylinder 2, mixed with combustion air, and passed through the mixture passage 7 to the mixing chamber 12.
to go into. The air-fuel mixture that enters the mixing chamber 12 is further mixed uniformly there and is delivered to the burner head 10 and the flame opening 9.
It is ignited by an ignition device (not shown) to cause combustion.

However, in the conventional example above, the vaporization wall temperature is
When fuels that are low at around 230℃ to 280℃ and easily turn into tar, such as denatured oil or heavy oil, are vaporized, tar adheres to the inner wall of the vaporizer cylinder 2, making it difficult to ignite and creating a strong odor after digestion. The dot was hot. In addition, in the conventional example, since the vaporization surface is under the nucleation film condition, most of the fuel sent from the fuel supply pipe 5 to the vaporization chamber 11 is vaporized at the collision surface 13 with the vaporization cylinder 2, and this portion The formation and adhesion of tar was concentrated in the area. Further, as time passes, tar increases and accumulates in a bank-like manner around the outer periphery of the collision surface 13, preventing fuel from dispersing, and eventually causing a pool of liquid. This caused problems such as the generation of unburned vaporized gas (white flame) due to vaporization delay during ignition, unstable combustion such as standing flames due to pulsating vaporization during steady combustion, and strong odor when extinguished.

On the other hand, the components in fuel that easily turn into tar are high boiling point components, and the formation and adhesion of tar can be prevented by setting the vaporization wall temperature to a high temperature, such as the film boiling temperature of the fuel or higher. When the temperature was increased, stable vaporization was not possible. In other words, the fuel filler port 5
The fuel sent out collides with the collision surface 13, but
Due to the high temperature of the wall surface, only a portion of the gas is vaporized, and most of it is dispersed as fine particles, which fall to the bottom of the vaporization cylinder and are vaporized. However, since the bottom surface is also under high-temperature film boiling conditions, the fallen fuel particles roll while floating on the vapor layer that forms in the boundary layer with the vaporization bottom surface, and tend to coalesce into giant particles.
Vaporization becomes irregular and stable vaporization is not performed.
In the case of combustion in the burner head 10, there were cases where flames started or, in extreme cases, misfires occurred.

Purpose of the Invention The present invention solves the above-mentioned problems in the conventional example, and aims to prolong the life of the vaporizer by preventing the formation and adhesion of tar during the vaporization of denatured oil and heavy oil. The purpose is to obtain a vaporized state.

Composition of the Invention In order to achieve this object, the present invention makes the surface roughness of the other vaporization surface of the vaporization cylinder larger than that of the collision surface with the fuel delivered from the fuel supply pipe, and the collision surface is maintained above the film boiling temperature of the fuel.

With this configuration, fuel that collides with a relatively smooth collision surface under high-temperature film boiling conditions splits into fine particles and scatters, and falls onto the vaporization surface with a large surface roughness, resulting in a high temperature state. However, the fuel vaporizes rapidly and stably in the nucleate boiling state, where the rate of vaporization and evaporation of the fuel is high. As a result, not only does tar not adhere to the collision surface, but also the vaporized fuel is not concentrated on the vaporization surface and is vaporized at a high temperature, thereby preventing the generation of tar and preventing pulsating vaporization, odor, etc.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. Components in the figure that are the same as those in FIG. 1 are designated by the same numbers, and explanations thereof will be omitted.

The vaporizing surface, which is the inner surface of the vaporizing cylinder 2, is coated with a heat-resistant paint film or a thermally sprayed film 100 of metal, ceramic, etc.
At the same time, only the collision surface 13 with the fuel is exposed as a smooth metal surface constituting the carburetor cylinder 2.

In this configuration, when the vaporization cylinder 2 is heated to a predetermined temperature and the fuel pump and combustion fan are operated to supply fuel and combustion air from the fuel supply pipe 5 and the air supply pipe 6 to the vaporization chamber 11, the fuel is heated to a high temperature. The smooth metal surface collides with the exposed collision surface 13 under film boiling conditions, breaks up, and scatters as fine particles to the vaporizing surface. Since the vaporization surface is covered with a heat-resistant paint film or thermal sprayed film that has a higher surface roughness than the metal surface, it will reach a nucleate boiling state even if it is at the same temperature as the collision surface 13, and the scattered and fallen fuel particles will Vaporized rapidly and stably. FIG. 3 is a characteristic diagram showing the above-mentioned vaporization state, with the horizontal axis showing the vaporization wall temperature and the vertical axis showing the relationship between the time required for vaporization and evaporation of a certain amount of fuel particles dropped onto the vaporization surface. In the figure, the solid line A indicates the characteristics of the vaporization surface where a smooth metal surface is exposed, and the broken lines B and B' indicate the characteristics of the vaporization surface covered with a heat-resistant paint film and a thermal spray coating. . As can be seen from the figure, on a smooth metal surface, the evaporation time begins to increase from around a relatively low temperature T _O , and the transition from the nucleate boiling region where the evaporation/vaporization time is short to the film boiling region begins. At a higher temperature, T ₁ , the film is completely boiling, and the vaporization and evaporation time are longer. In this state, the fuel that collides with the vaporization surface splits and scatters as high-temperature particles without being vaporized. On the other hand, on the vaporization surface covered with a heat-resistant paint film with a large surface roughness shown by line B, the nucleate boiling state with a short vaporization time is maintained not only at T _O mentioned above but also at a temperature of T ₁ . Fuel can be rapidly and stably vaporized even on the vaporization surface maintained at a temperature of ₁ . Furthermore, since the fuel falling onto the vaporization surface is at a high temperature at the collision surface, more rapid vaporization can be achieved. On the other hand, the same applies to the thermal spray coating shown by line B', and as shown in Fig. 4, on the metal surface of the vaporization cylinder, only the collision surface is made smooth, and the vaporization surface is made to have a large surface roughness by shot blasting, etc. You may. In this way, since there are almost no vaporized components of the fuel on the collision surface 13, not only is tar formation and adhesion on the collision surface 13 prevented, but also on the vaporization surface where the split and scattered high-temperature fuel particles fall. Although it is in a nucleate boiling state, the fuel to be vaporized is concentrated and does not fall, so the vaporization load is small, and since it is basically vaporized at a high temperature, rapid and stable vaporization can be obtained that prevents the formation of tar.

Next, another embodiment of the vaporizer of the present invention is shown in FIG. 5 and will be described. The vaporization surface of the vaporization cylinder 2 is covered with a heat-resistant paint film 101 with a large surface roughness, and the collision surface 13 is covered with a heat-resistant paint film 102 with a small surface roughness, so that the collision surface 13 is covered with a heat-resistant paint film 101 with a small surface roughness. condition. A characteristic diagram showing the relationship between the vaporization wall temperature and the fuel evaporation/vaporization time on the vaporization surface covered with a heat-resistant paint film with a small surface roughness is shown by the dashed line C in FIG. As is clear from Fig. 3, the vaporization surface (collision surface) covered with a heat-resistant paint film with a small surface roughness transitions to a film boiling state at a higher temperature than the metal surface shown by line A.
At high temperatures such as T ₂ , film boiling occurs,
The colliding fuel splits and scatters. On the other hand, the vaporization surface covered with the heat-resistant paint film 101 with a large surface roughness shown by line B maintains a nucleate boiling state even at a temperature of _T2 , and the fuel particles falling onto the vaporization surface rapidly and stably. Since it is vaporized at a high temperature, it is possible to prevent the formation and adhesion of tar.

Effects of the Invention As is clear from the above explanation, according to the present invention, the surface roughness of the other vaporization surfaces is made larger than the surface roughness of the collision surface of the fuel delivered from the fuel supply means with the vaporization tube. At the same time, because the collision surface was maintained at a temperature higher than the film boiling temperature of the fuel, the fuel that collided with the high-temperature collision surface splits and scatters, and disperses and falls as high-temperature fuel particles on the vaporization surface. Vaporization occurs rapidly and stably in the nucleate boiling state. Furthermore, since there are almost no vaporized components on the collision surface, there is no tar adhesion, and even on the vaporization surface, the fuel is dispersed as particles and falls, so the vaporization load is small, and since the fuel is vaporized at high temperatures, tar does not adhere to it. It is possible to obtain a long-life vaporizer that prevents generation and adhesion and is free from odor during ignition and extinguishing.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing a conventional vaporization device;
Figures a and b are cross-sectional views showing one embodiment of the vaporization device of the present invention, Figure 3 is a characteristic diagram showing the relationship between the vaporization wall temperature at the vaporization surface and the fuel vaporization time, and Figures 4a, b and FIGS. 5a and 5b are cross-sectional views showing other embodiments of the vaporizer of the present invention. 2... Vaporization cylinder, 3... Fuel pump, 4... Combustion fan, 13... Collision surface, 100, 101... Heat-resistant paint film with large surface roughness, 102... Heat-resistant paint film with small surface roughness.

Claims (1)

[Scope of Claims] 1. A vaporizer cylinder maintained at a high temperature, a combustion air supply means and a fuel supply means for supplying combustion air and fuel into the vaporization cylinder, and the fuel delivered from the fuel supply means and the fuel supply means. The surface roughness of the other vaporization surfaces is greater than the surface roughness of the collision surface, so that the fuel will be in a film boiling state at the collision surface with the vaporization surface of the vaporization cylinder, and will be in a nucleate boiling state at other vaporization surfaces. A larger vaporizer. 2. The collision surface is an exposed smooth metal surface of the vaporizing tube, and the other vaporizing surface is covered with a heat-resistant paint film having a large surface roughness or a thermal spray coating of ceramic or the like. vaporizer. 3. The vaporizer according to claim 1, wherein the collision surface is covered with a heat-resistant paint film having a small surface roughness, and the other vaporizing surface is covered with a heat-resistant paint film having a large surface roughness.