JP2022109638A - Small-sized combustion type heater - Google Patents

Abstract

To provide a small-sized combustion type heater system excellent in exhaust emission performance applicable to various heating means mounted in an automobile for vehicle room heating and others, and capable of developing quick heating ability in a short warming-up time for the system.SOLUTION: In the combustion type heater for making air mixed with gasified fuel generated by gasifying liquid fuel, introducing the generated air-fuel mixture into a combustion chamber to cause premixed combustion, and heating cooling water with a heat exchanger provided downstream, the liquid fuel is gasified in a fuel vaporization pipe with combustion heat, the equivalence ratio of the air-fuel mixture is controlled to be 0.65-0.8, and the air-fuel mixture is agitated in an agitation chamber. The directions of a plurality of nozzle holes formed in a burner top provided in the inlet of the combustion chamber are set to cause swirl flow in the combustion chamber, and the length in the upstream and downstream direction of the combustion chamber is set to be 60-150 mm.SELECTED DRAWING: Figure 2

Description

The present invention relates to a heater that heats water through a heat exchanger with a burner that evaporates liquid fuel, premixes it with air, and burns it, and relates to a compact heater that can be mounted on a vehicle.

Exhaust heat generated by internal combustion engines for automobiles has been used as a heat source for in-vehicle heaters. However, in recent years, as the efficiency of internal combustion engines has improved, the proportion of this exhaust heat has decreased, causing problems such as insufficient heat in the heater, longer engine warm-up time, and difficulty in starting up the heater. Also, in cold regions, the heating of automobiles is one of the important functions, and if the heating function is insufficient, it may lead to a matter of life and death.

Against this background, compact combustion heaters that use liquid fuel and can be mounted on vehicles have been put to practical use. For example, European manufacturers such as Webasto and Eberspaecher heat the cooling water of the engine with a small combustion heater and provide a system that assists the heating capacity for cold regions for the manufacturer's finished vehicle and for the aftermarket. .

Since these existing systems use combustion heaters, exhaust gases are emitted when the systems are in operation. Since automobile emissions regulations do not apply to combustors alone, existing systems do not give high priority to purification of exhaust gases, and some products do not sufficiently purify exhaust gases.

By installing a small combustion heater system in a car, it can be used not only to assist heating, but also to improve fuel efficiency by accelerating the heating of cooling water at startup, and to improve emissions by accelerating warm-up of the catalyst. For its intended use, the exhaust of automobile exhaust systems, including that of small combustion heaters, must be sufficiently purified to meet national exhaust emission regulations. For that purpose, it is necessary to sufficiently purify the exhaust gas of the compact combustion heater system itself.

In addition, since the compact combustion heater system popularized in the market by the aforementioned manufacturers uses a fuel vaporizer made of metal mesh to vaporize the fuel, it takes time to warm up the fuel vaporizer when the system is started. However, it takes 2 to 3 minutes for the system to reach steady state operation at which the system exhibits sufficient heat generation capacity, and there is the problem that it is not possible to quickly respond to heating demands that change according to operating conditions.

In addition, as shown in FIG. 12, the disclosed practical use S54-138137 describes a combustion apparatus in which fuel fed by an electromagnetic pump 103 is heated and vaporized by a vaporizer 110 and jetted to a burner 107 for combustion. A configuration is disclosed in which a preheat pipe 108 is provided in the middle of the discharge side pipe 106 between the carburetors 110 and the fuel is preheated by the exhaust gas after passing through the heat exchanger 117 .

According to this configuration, the exhaust gas preheats the fuel, so the system can be expected to start up quickly. Also, since the temperature of the exhaust gas after passing through the heat exchanger 117 is around 200° C., it is possible to prevent the fuel from being overheated and carbonized. However, this application was filed before exhaust emission regulations were strengthened, and there is no description about exhaust emission, and no device is incorporated from the viewpoint of purifying exhaust gas.

Public practical use S54-138137

The present invention has been made in view of the above points, and its main purpose is to be able to be installed in automobiles and used for various heating means such as vehicle interior heating, which has excellent exhaust emission performance and warms up the system. To provide a small-sized combustion heater system capable of quickly exhibiting heat generation capacity in a short time.

In the invention according to claim 1, the air supplied through the air supply passage by the blower is mixed with the vaporized fuel produced by vaporizing the liquid fuel, and the produced mixture is introduced into the combustion chamber for premixed combustion. In a combustion heater that heats cooling water by guiding the combustion gas to a heat exchanger provided downstream of the combustion chamber, the liquid fuel is vaporized by the combustion heat of the combustion chamber in a fuel evaporation pipe provided in the fuel passage. , the amount of the air and the vaporized fuel is controlled so that the equivalence ratio of the air-fuel mixture is between 0.65 and 0.8, and the air-fuel mixture is stirred in a stirring chamber provided in front of the combustion chamber. The directions of the plurality of injection holes for blowing out the air-fuel mixture formed in the burner top provided at the inlet of the combustion chamber are arranged so as to generate a swirling flow in the combustion chamber, and upstream and downstream of the combustion chamber. The length in the direction is set to 60 mm or more and 150 mm or less.

According to the first aspect of the present invention, in a warm steady state except at the time of starting, the fuel is vaporized by the combustion heat of the combustion chamber in the fuel evaporation pipe provided in the fuel passage, and a good air-fuel mixture is generated. Therefore, good exhaust emission performance can be obtained.

In addition, since the fuel is vaporized by the heat of combustion in the combustion chamber as described above, once ignited, the rated heat generating capacity can be exhibited quickly without requiring a long warm-up time.

In addition, the mixture is vaporized with air so that the equivalence ratio (a well-known physical quantity representing how many times the theoretical amount of fuel is supplied to air) is an arbitrary value between 0.65 and 0.8 Since the amount of fuel is controlled and the air-fuel mixture is sufficiently agitated in the agitation chamber before combustion, a good air-fuel mixture can be formed, and in particular the generation of CO and HC can be suppressed.

In addition, the direction of the plurality of injection holes for blowing out the air-fuel mixture formed in the burner top is configured so as to generate a swirl flow in the combustion chamber, and the length of the combustion chamber in the upstream and downstream directions is sufficiently secured, and the combustion Since the combustion gas can be retained in the room for a sufficient time, the generation of CO can be particularly suppressed.

The invention according to claim 2, in addition to the configuration of the invention according to claim 1, comprises a venturi at the end of the air supply passage, and a fuel nozzle is opened in the venturi portion, so that when the combustion heat is not present at the time of starting, the venturi It is characterized in that the air and the liquid fuel are mixed in a part.

According to the configuration of claim 2, when the system is started when the heat of combustion cannot be used, air and liquid fuel can be mixed in the venturi section, ensuring startability and improving exhaust emissions at the time of starting. be able to.

The invention according to claim 3 is characterized in that, in addition to the configuration of the invention according to claim 2, the stirring chamber is configured at the outlet of the venturi, and the downstream of the stirring chamber is partitioned by a mixing plate having a large number of holes. do.

According to the configuration of claim 3, air and vaporized fuel are mixed in the venturi to form an air-fuel mixture. Since the mixture is allowed to cool and is further stirred, a good air-fuel mixture can be generated.

The invention according to claim 4 is characterized in that, in addition to the invention according to claim 3, a guide-like protrusion is provided on the wall of the stirring chamber so that the air-fuel mixture forms a vortex.

According to the configuration of claim 4, since the guide-like protrusion is provided on the wall of the stirring chamber so that the air-fuel mixture forms a vortex, the stirring of the air-fuel mixture is facilitated, and a better air-fuel mixture is generated to generate a good air-fuel mixture in the combustion chamber. introduced into

The invention according to claim 5, in addition to the configuration of the invention according to claims 1 to 4, is that the nozzle holes are regularly aligned and have the same shape, and the directions are opposite to each other with the central axis of the burner top as a boundary. oriented nozzles are arranged, or the burner top is equally divided into four portions axially symmetrically and the adjacent portions are arranged with nozzles oriented in directions different from each other by 90°; It is characterized by arranging an orifice oriented in a direction in which a reverse-direction swirling flow is generated.

By arranging the injection holes as described in claim 5, the generation of swirl of the combustion flow in the combustion chamber is promoted, and the residence time of the combustion gas in the combustion chamber can be further increased. Generation of CO can be further suppressed.

The invention according to claim 6, in addition to the configurations of the inventions according to claims 2 to 5, takes in burnt gas from the downstream part of the combustion chamber and guides the burnt gas to the venturi part through the burnt gas passage. The burnt gas is mixed with the air-fuel mixture using the venturi negative pressure.

A large amount of the burned gas can be recirculated by taking in the burned gas from the downstream portion of the combustion chamber as described in claim 6 and mixing the same burned gas into the air-fuel mixture using the venturi effect. It is possible to reduce the maximum temperature of the flame, mainly to reduce NOx.

In addition to the configuration of the invention according to claim 6, the invention according to claim 7 is arranged such that the burned gas passage is arranged adjacent to the cooling water passage, the burned gas is appropriately cooled, and the burnt gas is cooled in the venturi. It is characterized in that the air-fuel mixture is prevented from self-igniting.

By arranging the burned gas passage adjacent to the cooling water passage as described in claim 7 and appropriately cooling the burned gas, it is possible to unintentionally cool the mixture in the vicinity of the venturi before reaching the combustion chamber. It is possible to prevent the system from being damaged due to self-ignition and abnormal combustion.

According to the present invention, it is possible to provide a compact combustion heater system which is excellent in exhaust emission performance, and which can quickly generate heat with a short warm-up time.

1 is an external view of a compact combustion heater in one embodiment of the present invention; FIG. 1 is a vertical cross-sectional view of a compact combustion heater in one embodiment of the present invention; FIG. It is a horizontal sectional view of the combustion chamber upper part of a small combustion type heater. FIG. 4 is a vertical cross-sectional view showing the venturi portion of the air supply passage above the small combustion heater and the vicinity of the fuel nozzle; FIG. 4 is a vertical cross-sectional view showing a fuel passage and a fuel evaporator in the upper portion of the compact combustion heater; It is the figure which looked at the mixing plate and the stirring chamber from the combustion chamber direction. It is the figure which looked at the horizontal cross section of the stirring chamber from the combustion chamber direction. (A), (B), (C) are plan views of three types of burner tops. It is a vertical cross-sectional view of the combustion chamber of the compact combustion heater. (A), (B), and (C) are graphs showing the exhaust emission performance of a compact combustion heater. (A) and (B) show a comparison of the water heating amount start-up performance and the exhaust emission start-up performance of the developed product (compact combustion heater of the present invention) and the market product (compact combustion heater manufactured by another company). 1 is a representation of a combustion device as described in published application S54-138137; FIG.

1 Small Combustion Heater 2 Blower 3 Combustion Chamber Head 4 Combustion Chamber Block 5 Heat Exchanger Holder 11 Air Supply Passage 12 Stirring Chamber 13 Combustion Chamber 14 Heat Exchanger 15 Cooling Water Passage 16 Venturi 17 Fuel Nozzle 18 Fuel Passage 19 Fuel Evaporator 20 ignition heater 21 mixing plate 22 guide projection 23 burner top 24 injection port 30 exhaust passage 31 volume portion 32 combustion chamber wall 35 EGR passage 36 cooling water inlet 37 cooling water outlet

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail based on the drawings. In addition, this invention is not limited to the following embodiment. In addition, appropriate modifications are possible without departing from the scope of the effects of the present invention.

FIG. 1 is a diagram showing the appearance of a compact combustion heater in one embodiment of the present invention. FIG. 2 is a vertical sectional view of the compact combustion heater. Although the compact combustion heater 1 does not require the current attitude shown in the figure when it is mounted on a vehicle, the vertical and horizontal directions are indicated based on the attitude shown for the sake of convenience.

(Structure of the compact combustion heater of the present invention)
First, the configuration of the compact combustion heater of the present invention will be described with reference to FIGS. 1 to 7. FIG.
As shown in FIG. 1, air is supplied through the air supply passage 11 by the action of the blower 2 . After exiting the blower 2, the air supply passage 11 is connected to an air supply passage formed in the combustion chamber head 3 as shown in FIG.

A fuel nozzle 17 opens in the venturi 16 portion. The terminal end of the venturi 16 opens into the stirring chamber 12 provided in the combustion chamber head 3 as shown in FIG. As shown in FIG. 6, the lower part of the stirring chamber 12 is partitioned by a mixing plate 21 having a large number of punched holes, and as shown in FIG. 23 and is connected to the combustion chamber 13 . The combustion chamber 13 is surrounded by a combustion chamber block 4 , and a cooling water passage 15 is formed in the wall surface of the combustion chamber block 4 .

A heat exchanger 14 is arranged in the lower part of the combustion chamber 13 , and the periphery and the lower part thereof are surrounded by a heat exchanger holder 5 . The inside of the heat exchanger holder 5 is connected to the cooling water passage 15 of the combustion chamber block 4 and filled with cooling water. With this configuration, when combustion takes place in the combustion chamber 13, the burned gas is introduced into the primary side passage formed in the heat exchanger 14, and the heat of the burned gas is transferred to the cooling water in the secondary side passage. . At the bottom of the heat exchanger holder 5, a volume part 31 for collecting the burned gas that has passed through the heat exchanger 14 and an exhaust passage 30 for guiding the burned gas to the exhaust system are provided. The cooling water passage 15 is provided with a cooling water inlet 36 at the heat exchanger holder 5 and a cooling water outlet 37 at the combustion chamber block 4 .

(Operation of the compact combustion heater of the present invention)
A certain amount of air is supplied to the air supply passage 11 by the operation of the blower 2 . Air is led to the venturi 16 through the air supply passage 11, and a fuel nozzle 17 is opened in the venturi 16 portion. With this configuration, even at the time of starting when combustion is not performed, the air-fuel mixture is formed while the fuel in the liquid state is atomized by the venturi effect.

Once the ignition heater 20 ignites the air-fuel mixture in the combustion chamber 13 to start combustion, the fuel evaporator 19 disposed in the combustion chamber is heated by the heat of the combustion flame as shown in FIG. The liquid fuel inside is vaporized. Therefore, in a steady state, the air and the vaporized fuel are mixed in the venturi 16 to supply a good air-fuel mixture and improve the exhaust emission performance.

FIG. 3 is a view of the upper portion (entrance) of the combustion chamber 13 viewed from below, and the fuel evaporation pipe 17 is arranged close to the combustion chamber wall 32 and the burner top 23 . This is constructed such that a part of the fuel passage 18 is arranged inside the combustion chamber 13 as a fuel evaporation pipe 19 . According to this configuration, the fuel evaporator 19 is appropriately heated by the flame, and the liquid fuel flowing through the fuel evaporator 19 is vaporized. The length of the fuel evaporator tube 19 is adjusted to receive sufficient heat from the flame to evaporate the fuel inside. On the other hand, the fuel evaporator 19 is arranged near the combustion chamber wall 32 where the temperature is relatively low in the combustion chamber to prevent the carbonization of the fuel inside due to the heating of the fuel evaporator 19 .

In addition, since the fuel is vaporized by the heat of combustion in the combustion chamber, once ignition is performed, the rated heat generating capacity can be exhibited quickly without requiring a long warm-up time. FIG. 11 shows an experimental comparison of the start-up performance at the time of starting the system between the compact combustion heater of the present invention (development product) and the compact combustion heater of another company (market product). In FIG. 11, (A) is the start-up performance of CO/NOx exhaust emissions, and (B) is the start-up performance of heat generation performance (water heating amount).

As shown in FIG. 11(A), the compact combustion heater of the present invention reaches a steady state within 1 minute after starting and demonstrates sufficient heat generation performance (water heating amount), whereas the market product It takes 2-3 minutes to reach a steady state. Therefore, it can be seen that the small-sized combustion heater of the present invention is superior in that it exhibits heat generation performance more quickly in response to environmental changes.

In addition, in FIG. 11(B), in terms of exhaust emission performance in a steady state, the small combustion heater of the present invention has a slightly lower CO level and a significantly lower NOx level than the marketed product. It can be seen that the exhaust emission performance is also excellent.

In addition to gasoline and light oil, various alcohol fuels and kerosene can also be used as liquid fuels.

The amount of air and vaporized fuel is controlled so that the mixture has an arbitrary equivalence ratio between 0.65 and 0.8. As a method, the relationship between the equivalence ratio and the flame temperature is used, and the value sensed by the ignition heater 20, which also functions as a flame temperature sensor (resistance temperature sensor), is fed back so that it becomes the target value (target voltage). to control fuel flow.

At this time, the flame temperature changes depending on the intake air temperature and water temperature of the system, and the fluctuation of the equivalence ratio becomes large. is used to suppress the fluctuation of the equivalence ratio. By controlling the equivalence ratio to an arbitrary value between 0.65 and 0.8 with high precision, the trade-off relationship between CO and NOx in the exhaust gas can be kept within the target range, satisfying the requirements. good exhaust emission performance can be stably obtained.

The mixture then flows into the stirring chamber 12 . As shown in FIG. 7, a guide projection 22 is formed at the outlet of the venturi 16 at the end of the air supply passage. , two vortices are generated along the walls and these arrangements provide good mixing of the mixture.

Furthermore, as shown in FIG. 6, the lower portion of the stirring chamber 12 is partitioned by a mixing plate 21 having a large number of punched holes. is formed, which can mainly reduce CO and HC in the exhaust.

The mixture is then introduced into the combustion chamber 13 via the burner top 23 . A burner top 23 has a large number of nozzle holes 24 regularly aligned. The arranged nozzle holes 24 are configured so that the flame generates a swirling flow within the combustion chamber. Further, an ignition heater 20 is arranged so as to protrude into the combustion chamber. When the system is started, the ignition heater 20 is energized to ignite the air-fuel mixture that has flowed into the combustion chamber 13, and thereafter the burner top 23 is turned off. As many flames as the nozzle holes 24 are generated in the combustion chamber 13 .

FIG. 8 shows an example of the arrangement of nozzle holes on the burner top. FIG. 8(A) shows a pattern in which nozzle holes directed in opposite directions with respect to the central axis of the burner top are arranged. Due to this arrangement, the air-fuel mixture flowing into the combustion chamber through the nozzle forms a single spiral flame as a whole.

Next, FIG. 8(B) shows a pattern in which the burner top is equally divided into four portions axially symmetrically, and nozzle holes oriented in directions different from each other by 90° are arranged in adjacent portions. In this arrangement as well, the air-fuel mixture flowing into the combustion chamber through the nozzle forms a single swirl flame as a whole.

FIG. 8(C) shows a pattern in which nozzle holes are arranged so as to generate swirling flows in opposite directions with respect to the central axis of the burner top. In this arrangement, the air-fuel mixture entering the combustion chamber through the nozzles generally forms two oppositely directed swirl flames.

These are examples of the arrangement of the orifices on the burner top forming a spiral flame, but by devising the arrangement of the orifices, it is possible to form a spiral flame by other arrangements.

Next, FIG. 10 shows a graph showing the relationship between the height of the combustion chamber and the exhaust emission performance. FIG. 10(A) shows the NOx emission performance, FIG. 10(B) shows the CO emission performance, and FIG. 10(C) shows the trade-off performance between NOx and CO. In this experiment, the exhaust emission performance was measured by changing the combustion chamber height H shown in FIG. 9 to 60 mm, 90 mm, and 120 mm.

From these graphs, it can be seen that increasing the combustion chamber height H (Fig. 9) suppresses CO emissions and improves the trade-off performance between NOx and CO. The reason for this is that if the height H of the combustion chamber is increased, the time for which the burned gas stays in the combustion chamber increases, so that a sufficient combustion time can be secured and the amount of CO generated by incomplete combustion can be reduced.

Therefore, the lower limit of the combustion chamber height H is required to be 60 mm in order to sufficiently reduce CO, and the upper limit of the combustion chamber height H is about 150 mm in terms of mountability.

Forming a spiral flame by devising the arrangement of the nozzle holes 24 of the burner top described above can also increase the residence time of the burned gas in the combustion chamber and contribute to the reduction of CO.

The combustion chamber 13 communicates with the primary side gas passage of the heat exchanger 14 disposed below the combustion chamber 13, and high-temperature burned gas is introduced into the primary side gas passage. On the other hand, the secondary side cooling water passage of the heat exchanger 14 communicates with the cooling water passage 15 on the outer periphery of the heat exchanger, and the cooling water passage 15 on the outer periphery of the heat exchanger also serves as the cooling water passage on the wall surface of the combustion chamber 13. As shown in FIG. 2, cooling water is circulated between a cooling water inlet 36 provided on the heat exchanger holder 5 and a cooling water outlet 37 provided on the combustion chamber block 4 . The cooling water in the cooling water passage on the wall surface of the combustion chamber 13 circulates while cooling the combustion chamber appropriately. With these configurations, heat is transferred from the burned gas to the cooling water via the heat exchanger 14 .

The primary gas passages of the heat exchanger 14 gather at a lower volume portion 31 and are connected to an exhaust passage 30, through which burned gas is discharged.

Further, as shown in FIG. 9, an EGR passage 35 is led from the lower portion of the combustion chamber 13 to the venturi portion and opened to recirculate the burned gas. By opening the venturi, it is possible to recirculate a large amount by utilizing the venturi effect. In addition, by arranging the EGR passage adjacent to the cooling water passage 15 and appropriately cooling the burnt gas, self-ignition of the air-fuel mixture in the venturi and damage to the device are prevented. .

FIG. 10 shows the effect of EGR (exhaust gas recirculation) on exhaust emission performance. It can be seen from FIGS. 10A and 10C that NOx is remarkably reduced when EGR is performed. By performing EGR using this configuration, the exhaust emission performance of the system can be greatly improved.

Claims (7)

The air supplied through the air supply passage by the blower is mixed with the vaporized fuel generated by vaporizing the liquid fuel, the generated mixture is introduced into the combustion chamber for premixed combustion, and is installed downstream of the combustion chamber. In a combustion heater that guides this combustion gas to a heat exchanger to heat cooling water,
The liquid fuel is vaporized by combustion heat of the combustion chamber in a fuel evaporation pipe provided in the fuel passage,
The amount of the air and the vaporized fuel is controlled so that the equivalence ratio of the air-fuel mixture is between 0.65 and 0.8, and the air-fuel mixture is stirred in a stirring chamber provided in front of the combustion chamber. is,
The direction of the plurality of injection holes for blowing out the air-fuel mixture formed in the burner top provided at the inlet of the combustion chamber is configured so as to generate a swirling flow in the combustion chamber, and the length in the upstream and downstream directions of the combustion chamber is is set to 60 mm or more and 150 mm or less,
A combustion heater characterized by: A venturi is formed at the end of the air supply passage, a fuel nozzle is opened in the venturi, and the air and the liquid fuel are mixed in the venturi at the time of starting without the combustion heat.
The combustion heater according to claim 1, characterized by: The stirring chamber is configured at the outlet of the venturi, and the downstream of the stirring chamber is partitioned by a mixing plate having a large number of holes.
3. The combustion heater according to claim 2, characterized by: The wall of the stirring chamber is provided with a guide projection so that the air-fuel mixture forms a vortex,
The combustion heater according to claim 3, characterized by: The nozzle holes are regularly aligned and have the same shape, and the nozzle holes are arranged in directions opposite to each other with respect to the central axis of the burner top, or the burner top is divided into four equal parts axially symmetrically. arranging nozzle holes oriented in directions different from each other by 90° in adjacent portions, or arranging nozzle holes oriented in directions that generate swirling flows in mutually opposite directions with respect to the central axis of the burner top;
A combustion heater according to any one of claims 1 to 4, characterized in that: Burned gas is taken in from the downstream part of the combustion chamber, the burned gas is led to the venturi part through the EGR passage, and the burned gas is mixed with the air-fuel mixture using the venturi negative pressure.
The combustion heater according to any one of claims 2 to 5, characterized in that: The EGR passage is arranged adjacent to the cooling water passage to appropriately cool the burnt gas and prevent the air-fuel mixture from self-igniting in the venturi.
7. The combustion heater according to claim 6, characterized in that:

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