JPH08303721A - Liquid fuel combustion device - Google Patents

Abstract

PURPOSE: To provide a liquid fuel combustion device, capable of reducing the minimum amount of combustion (combustion load) remarkably compared with a conventional device without inviting any deterioration of the condition of combustion. CONSTITUTION: The volume of an auxiliary combustion chamber 5 is set so as to be sufficiently smaller than a main combustion chamber 4 to obtain a volume suitable for the minimum amount of combustion and maintain the good mixing condition of fuel and air in the auxiliary combustion chamber 5 even when the amount of combustion air is reduced. Further, the diameter of an auxiliary combustion tube 52 is enlarged suddenly with respect to the auxiliary mixing tube 51 of the auxiliary combustion chamber 5 to reduce the flow speed of combustion air suddenly in the auxiliary combustion tube 52 whereby flame retaining effect, retaining a flame ignited by an ignition device 6, can be obtained. According to this method, good combustion can be maintained without inviting any deterioration of burning conditions even during the minimum combustion amount (ULO combustion amount) wherein the flow rate of fuel is set so as to be remarkably smaller amount (the degree of 1/15-1/20, for example) than the amount upon the HI combustion amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion device for burning liquid fuel, which is suitable for heating automobiles (especially electric vehicles).

[0002]

2. Description of the Related Art Conventionally, in a combustion type heating device for an automobile, liquid fuel (light oil, kerosene, etc.) is burned, and the combustion gas and water are heat-exchanged to produce hot water, and the hot water is used in a passenger compartment. It circulates through a heating heat exchanger (heater core), where heating air is heated and blown out into the passenger compartment.

Then, the temperature of the hot water is detected, and the combustion load of the combustor can be switched between three levels: high (HI), low (LO), and stopped (OFF) according to the temperature of the hot water. And the combustion load of LO is normally 1/2 to 1 of HI.
It is set to a value of / 4.

[0004]

By the way, when heating is performed by using the above-described combustor alone, if the air volume of the blower for heating air is reduced and the heat radiation amount in the heater core is reduced, Even if the combustion amount (combustion load) of the combustor is set to LO, the amount of heat generated by the combustor is larger than the amount of heat dissipated by the heater core, so the hot water temperature rises more than necessary. Therefore, conventionally, in order to protect the combustor, there is a situation in which the combustion of the combustor must be temporarily stopped.

However, once the combustion of the combustor is stopped, it takes time for scavenging and preheating of the combustor until re-ignition. Therefore, the temperature of the hot water drops during this period, and the temperature of the air blown into the passenger compartment is reduced. However, there was a problem that the required heating capacity was not obtained. In addition, the harmful components in the exhaust gas discharged from the combustor are particularly large during ignition and extinguishing.Therefore, if the combustion control that frequently repeats ignition and extinguishing is performed as described above, this harmful component will increase. , Causes a problem of adversely affecting the environment.

In order to avoid such a problem, LO
However, in the conventional combustor structure, the combustion state deteriorates for the following reasons with the decrease in the combustion amount, so it is difficult to reduce the combustion amount below the current LO. there were. That is, in the conventional combustor structure, the size of the combustion chamber is generally HI that is in a normal use state.
It is designed to match the combustion amount of. For this reason,
For example, at a combustion amount of 30% or less of HI, the air swirl speed inside the combustion chamber due to the swirl flow generator (swirler) decreases as the intake air amount decreases, and the mixing state of air and fuel vapor deteriorates. To do.

Therefore, in the combustion chamber, excess air is locally generated, and conversely, excess fuel is locally generated, which deteriorates the combustion state. Further, in the conventional combustor structure, since there is no place in the combustion chamber for holding the ignited flame well, the combustion amount decreases, and when the combustion amount becomes about 10% of HI, the flame becomes weak. Therefore, problems such as being blown out by the combustion air are likely to occur.

The present invention has been made in view of the above points,
An object of the present invention is to provide a liquid fuel combustion apparatus capable of significantly reducing the minimum combustion amount (combustion load) as compared with a conventional apparatus without causing deterioration of the combustion state.

[0009]

In order to achieve the above object, the present invention employs the following technical means. In the invention according to claim 1, a fuel supply means (63,
64) and an air supply means (7) for supplying combustion air,
A combustion chamber (4, 5) for mixing and burning the liquid fuel and the combustion air, an ignition device (6) for igniting a mixture of the liquid fuel and the combustion air, and the combustion chamber (4, 5). Heat exchanger (8) for exchanging heat between the burned combustion gas and the heat medium
And a sub-combustion chamber (5) located upstream of the mixture, and a main combustion chamber (4) located downstream of the sub-combustion chamber. The auxiliary combustion chamber (5) is configured to have a smaller volume than the main combustion chamber (4), and the ignition device (6) ignites the air-fuel mixture in the auxiliary combustion chamber (5). The liquid fuel combustion apparatus is characterized in that a flame holding portion for holding the flame ignited by the ignition device (6) is formed in the sub combustion chamber (5).

According to a second aspect of the invention, in the liquid fuel combustion apparatus according to the first aspect, a sub-mixing cylinder (51) for mixing the liquid fuel and the combustion air is provided in the sub-combustion chamber (5). A sub-combustion cylinder (52) for burning a mixture of liquid fuel and combustion air mixed in the sub-mixing cylinder (51) is provided, and the sub-combustion cylinder (52) with respect to the sub-mixing cylinder (51). The flame holding portion is formed by rapidly expanding the volume of).

According to a third aspect of the present invention, in the liquid fuel combustion apparatus according to the first or second aspect, an air hole (51a) for allowing the combustion air to swirlly flow into the sub-mixing cylinder (51), The fuel supply pipe (6 of the fuel supply means
3) and the ignition device (6) are provided, and the air-fuel mixture is ignited in the sub-mixing cylinder (51).

The reference numerals in parentheses of the above means indicate the correspondence with the concrete means described in the embodiments described later.

[0013]

According to the inventions of claims 1 to 3,
As described above, since the volume of the auxiliary combustion chamber is set smaller than that of the main combustion chamber so that the volume is adapted to the minimum combustion amount, even if the combustion air amount decreases, the amount of fuel and air in the auxiliary combustion chamber decreases. A good mixed state can be maintained, and local excess air and excess fuel do not occur.

Moreover, since the auxiliary combustion chamber is formed with the flame holding portion for holding the flame ignited by the igniter, the flame holding action for holding the flame well can be obtained even when the minimum combustion amount is set. To be In addition, unlike the main combustion chamber, the combustion air supply pipe is not installed in the sub-combustion chamber, so the flame touches this pipe and is cooled, or the flame is blown out by the air blown out from this pipe. Does not occur.

Therefore, even at the minimum combustion amount (ULO combustion amount) in which the fuel flow rate is set to a minute amount (for example, about 1/15 to 1/20) which is significantly smaller than that at the HI combustion amount, the combustion state deteriorates. Good combustion can be maintained without causing. Therefore, it is possible to continue the combustion at the minimum combustion amount (ULO combustion amount) and maintain the flame in the state of the pilot fire. Therefore, when it is necessary to increase the heating capacity, the combustion amount L is large.
It is possible to smoothly shift the combustion mode to the O combustion amount and the HI combustion amount.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an embodiment of the present invention, FIG. 2 shows an entire system of a heating device for an electric vehicle, and 1 is a liquid fuel combustion device according to the present invention, which comprises combustion gas and water. Heat is exchanged to produce hot water. 2 is a heater unit for heating the passenger compartment, which is a liquid fuel combustion device 1
The hot water heated in step 2 and the blown air of the blower 2a (air inside or outside the vehicle) are heat-exchanged to heat the blown air,
The heated air (warm air) is blown into the passenger compartment. Three
Is a water pump for circulating hot water between the liquid fuel combustion device 1 and the heater unit 2.

The above liquid fuel combustion device 1 and water pump 3
Is installed in a motor room in which a traveling motor of the electric vehicle is installed, and the heater unit 2 is installed in a vehicle room of the electric vehicle. FIG. 1 shows a specific structure of the liquid fuel combustion apparatus 1. This apparatus is roughly classified into a main combustion chamber 4, a sub-combustion chamber 5, an ignition device 6, a blower 7 for combustion air, a heat exchanger 8, And a water pump 3 for circulating hot water.

Hereinafter, each of the above components will be specifically described. The main combustion chamber 4 has a cylindrical shape extending in the horizontal direction, and is a main mixing cylinder 4 for mixing combustion air and fuel vapor.
1 and a main combustion cylinder 42 connected to the downstream side of the main mixing cylinder 41. An air supply pipe 43 that supplies combustion air is concentrically arranged in the center of the main mixing cylinder 41. A plurality of slits 44 extending in the axial direction are provided on the circumferential surface of the air supply pipe 43. Further, between the main mixing cylinder 41 and the main combustion cylinder 42, a flame holding diaphragm 45 for holding a flame in the main mixing cylinder 41 is arranged.

The sub-combustion chamber 5 is disposed in an upper portion of the main mixing chamber 41 of the main combustion chamber 4, and the sub-combustion chamber 5 has a cylindrical shape extending in the vertical direction.
It has a sub-mixing cylinder 51 for mixing combustion air and fuel vapor, and a sub-combustion cylinder 52 connected to the downstream side (lower side) of the sub-mixing cylinder 51. By expanding the diameter of the sub-combustion cylinder 52 with respect to the sub-mixing cylinder 51 by, for example, about twice,
The volume of the sub-combustion cylinder 52 is suddenly increased with respect to the sub-mixing cylinder 51, and when the combustion air flows into the sub-combustion cylinder 52 from the sub-mixing cylinder 51, the flow velocity of the combustion air sharply decreases. The flame holding portion for holding the flame is formed by the shape of the sudden expansion of the volume.

The ignition device 6 comprises a glow plug 61 for fuel ignition.
The glow plug 61 has a glow plug boss portion 6
It is screwed and fixed to 2. The glow plug 61 is provided with a cylindrical heating portion 61a made of an electric resistor, and the surface of this heating portion 61a is covered with a ceramic heat-resistant member. The heating portion 61a is provided in the sub-mixing cylinder 5
1 is vertically arranged so as to project inside.

In the glow plug boss portion 62, the fuel supply pipe 6 is provided at the base of the heating portion 61a of the glow plug 61.
3 is opened, and liquid fuel (light oil, kerosene, etc.) is supplied to this pipe 63 by an electrically operated fuel pump (for example, solenoid pump) 64. Then, the liquid fuel is supplied to the root portion of the heating portion 61a from the opening end at the tip of the fuel supply pipe 63.

The blower 7 for combustion air is arranged in a lower portion of the main mixing chamber 41 of the main combustion chamber 4.
It has a centrifugal blower fan 71 and a motor 72 for driving the same. The air sucked from the air intake port 73 is blown by the blower fan 71 to the swirl flow generator (swirler) 74 side. The swirl flow generator 74 is arranged at the inlet of the air supply pipe 43 described above, and gives a swirl flow to the combustion air flowing into the pipe 43. Further, a part of the combustion air supplied to the swirling flow generator 74 part is branched, passes through the air passage 75, and passes through the main mixing cylinder 4
The air flows into the main mixing cylinder 41 directly from the air holes 41a formed in the first mixing hole 1.

Further, a part of the combustion air supplied to the swirling flow generator 74 is branched and passed through the air passage 76,
The air is introduced into the sub-mixing cylinder 51 through a plurality of air holes 51a formed in the sub-mixing cylinder 51. Here, in this example, the plurality of air holes 51a are opened in four locations on the wall surface of the sub-mixing cylinder 51 in the tangential direction of the circumferential surface. The reason why the plurality of air holes 51a are opened in the circumferential tangential direction of the wall surface of the sub-mixing cylinder 51 in this way is to form a swirling flow of combustion air in the sub-mixing cylinder 51.

In this embodiment, the glow plug boss portion 62 is integrally formed with the sub mixing cylinder 51 and the sub combustion chamber 52. The combustion air blown by the blower 7 is distributed so that about 80% of the combustion air is supplied to the air supply pipe 43 and about 10% is supplied to each of the air passage 75 and the air passage 76.

The combustion gas that has passed through the main combustion cylinder 42 of the main combustion chamber 4 makes a U-turn at the downstream end of the main combustion cylinder 42 (the right end portion in FIG. 1) to form a cylindrical shape on the outer peripheral surface side of the main combustion cylinder 42. The gas is discharged from the exhaust port 47 to the outside through the exhaust passage 46 formed in. The heat exchanger 8 for exchanging heat between the combustion gas and water is formed in a cylindrical shape further on the outer peripheral side of the cylindrical exhaust passage 46, and hot water is supplied to the space (water passage) in the heat exchanger 8. The circulating water pump 3 is arranged below the main combustion cylinder 42. The water pump 3 is composed of a pump unit 31 and a driving motor 32, and when the pump unit 31 operates, the hot water inlet 3 located at the right end of FIG.
The hot water is sucked from 3 and the hot water is supplied to the hot water inlet portion 81 of the heat exchanger 8.

The hot water passage 82 in the heat exchanger 8 is formed in a spiral shape by the spiral protrusions 82a, so that the hot water flows in the hot water passage 82 spirally from the right side to the left side in FIG. ing. The heat exchanger 8 is a plate-shaped fin 8 arranged so as to project into the exhaust passage 46.
The hot water is heated by exchanging heat with the combustion gas via 2b.
In the heat exchanger 8, a hot water outlet 83 is arranged at the left end of FIG. 1, and the hot water flows out from the hot water outlet 83 to the heater unit 2 for heating the passenger compartment in FIG. ing.

Reference numeral 9 is a frame sensor for detecting the presence / absence of flame in the main mixing cylinder 41, which is composed of a photodiode. 1
Reference numeral 0 denotes a hot water temperature sensor arranged at the hot water inlet portion 81 of the heat exchanger 8, which detects the temperature of the hot water flowing into the heat exchanger 8 to control the combustion amount (combustion load). Become. Reference numeral 11 denotes a thermostat for preventing heating by air (for preventing overheating), which is arranged on the outer surface side of the heat exchanger 8 and detects the outer surface temperature of the heat exchanger 8 to open and close the switch.

Reference numeral 12 is a fuel evaporator (wick) in which a heat-resistant metal such as stainless steel is formed in the shape of a wire mesh, and is arranged on the inner peripheral wall surfaces of the sub-mixing cylinder 51, the sub-combustion chamber 52, and the main mixing cylinder 41. Has been done. FIG. 3 is a block diagram showing a schematic configuration of electric control. 13 is an electric control device, 14 is an operation switch of a vehicle heating device, 15 is an on / off operation of the blower 2a of the heater unit 2 for heating the vehicle interior, and a blower. Two
It is a heater fan switch for speed switching of a. Reference numeral 16 is an operation indicator light.

Next, the operation of this embodiment having the above-mentioned structure will be described. FIG. 4 is a timing chart showing the operation transition of each device with respect to the elapsed time t after the operation switch 14 is turned on (ON). The operation indicator lamp 16 blinks when the operation switch 14 is turned on, and at the same time, the glow plug 61 and the water. The pump 3 is energized. After the glow plug 61 is preheated for a predetermined time (for example, about 20 seconds), the blower 7 for combustion air is energized, and the blower 7 is started. Also,
Almost at the same time, the fuel pump 64 is energized to start the supply of fuel, so that the fuel is supplied into the glow plug boss portion 62, the mixture of fuel and air is ignited, and combustion is started.

At the same time as the ignition, the flame sensor 9 detects the flame of combustion, and after a predetermined time (for example, about 35 seconds) has passed, the glow plug 61 is de-energized, and thereafter, the steady combustion state is entered. At this time, the heating fan 2a is started and the operation indicator lamp 16 is continuously turned on. In the steady combustion state, the hot water inlet 81 of the heat exchanger 8
HI- of the combustion amount (combustion load) of the combustion device according to the hot water temperature detected by the hot water temperature sensor 10 arranged in
The LO is automatically switched.

That is, when the temperature detected by the temperature sensor 10 reaches the upper limit set temperature (for example, 80 ° C.), both the fuel pump 64 and the combustion air blower 7 are driven at a low speed (L).
O) operation is performed, and the combustion device performs combustion operation according to the LO combustion amount. Then, when the combustion operation by the LO combustion amount is continued and the temperature detected by the temperature sensor 10 decreases to the lower limit set temperature (for example, 70 ° C.), the fuel pump 6 is restarted.
4 and the combustion air blower 7 both operate at high speed (HI), and the combustion device performs combustion operation according to the HI combustion amount.

In this way, by automatically switching the combustion amount (combustion load) of the combustion device in two stages of HI-LO,
The hot water temperature is automatically controlled within a predetermined range. Then, in the heater unit 2, the air blown by the blower 2a is heated by exchanging heat with the hot water circulated by the water pump 3, and the heated air is blown into the vehicle interior to heat the vehicle interior.

When the operation switch 14 is turned off to stop the operation of the heating device, the fuel pump 64 is stopped, and thereafter, the combustion air blower 7 and the water pump 3 are operated for a predetermined time (for example, 20 seconds). The scavenging operation (post-purge) is continuously performed, and thereafter, the operations of the combustion air blower 7 and the water pump 3 are stopped. The combustion device is LO
Even if the combustion operation is performed with the combustion amount, the amount of heat radiation on the heater unit 2 side is small, so when the temperature detected by the temperature sensor 10 reaches the upper limit set temperature, the operation switch 14 is operated.
After performing the scavenging operation (post-purge) similar to that at the time of OFF, the combustion operation by the LO combustion amount is restarted.

The operation of the heating device as a whole is as described above, but in order to reduce the on / off of the combustion operation of the combustion device, the minimum combustion amount (ULO combustion) whose combustion amount is much smaller than the LO combustion amount. It is useful to set the combustion operation by the amount), and the combustion operation by the minimum combustion amount (ULO combustion amount) will be described in detail below.

At this minimum combustion amount (ULO combustion amount),
The fuel flow rate is set to a minute amount of about 1/15 to 1/20 of the HI combustion amount. That is, the rotation speed of the fuel pump 64 is reduced to the rotation speed corresponding to this minute amount of fuel. On the other hand, the amount of combustion air is the flow rate of air flowing into the sub-mixing cylinder 51 through the plurality of air holes 51a (the amount of air blown by the blower 7 for combustion air-
The amount of air that directly flows into the main mixing cylinder 41) is set to an amount that provides an appropriate excess air ratio (about 1.3 to 2.0).

Thus, the minimum combustion amount (ULO combustion amount)
At times, combustion is completed in the auxiliary combustion cylinder 52 because the fuel consumption is minute. In this case, since the sub-mixing cylinder 51 and the sub-combustion cylinder 52 are installed independently of the main mixing cylinder 41 and the main combustion cylinder 42, the volumes of the sub-mixing cylinder 51 and the sub-combustion cylinder 52 are set to the minimum combustion amount (ULO). It can be set to a small one that is suitable for combustion at the time of combustion).

In other words, the volumes of the sub-mixing cylinder 51 and the sub-combustion cylinder 52 can be set to be significantly smaller than those of the main mixing cylinder 41 and the main combustion cylinder 42. Therefore, the sub-mixing cylinder 51
Further, in the sub combustion cylinder 52, a good mixed state of fuel and air can be maintained, and local excess air and excess fuel do not occur. Moreover, the auxiliary combustion cylinder 52 is
When the combustion air flows into the sub-combustion cylinder 52 from the sub-mixing cylinder 51 by rapidly expanding the volume of the combustion air, the flow velocity of the combustion air is suddenly decreased. A flame action is obtained. Further, since the combustion air supply pipe 43 is not installed in the sub combustion cylinder 52,
The flame does not touch the pipe 43 to be cooled, and the air blown out from the pipe 43 blows out the flame.

Therefore, the fuel flow rate is set to 1 / the HI combustion amount.
Minimum combustion amount (U
Even at the time of the LO combustion amount), good combustion can be maintained without deteriorating the combustion state. Then, the combustion amount (combustion load) is set to the minimum amount (ULO) to suppress the rise of the combustion temperature, and the combustion gas which has completed the combustion in the auxiliary combustion cylinder 52 is supplied to the fuel supply pipe in the main mixing cylinder 41. Since it is mixed with the combustion air (low temperature outside air) supplied from the slit 44 of 43 and the air hole 41a, the temperature thereof decreases. Therefore, even if the speed of the heating blower 2a is set to a low speed (LO) in the vehicle interior heating heater unit 2 and the amount of heat radiation in the heater unit 2 becomes small, the rise of the hot water temperature is suppressed and combustion is performed. It is possible to prevent automatic stoppage to prevent overheating of the device.

Therefore, the combustion with the minimum combustion amount (ULO combustion amount) can be continued, and the flame can be maintained in the state of the pilot fire. Therefore, when it is necessary to increase the heating capacity, the LO combustion with a large combustion amount is performed. The combustion mode can be smoothly changed to the amount and the HI combustion amount. It should be noted that the present invention is not limited to the above-described embodiment, and can be variously modified. In the above-described embodiment, the heat exchanger 8 exchanges heat between the combustion gas and water (heat medium) to generate water. Although the hot water system is configured to be heated, the heat exchanger 8 may be configured to directly heat not the water but the air (heat medium) for heating the passenger compartment by the combustion gas.

Further, in the above embodiment, the inner diameter (volume) of the sub-combustion cylinder 52 is suddenly expanded with respect to the sub-mixing cylinder 51, and the flow velocity of the combustion air flowing into the sub-combustion cylinder 52 is rapidly reduced. Although the flame holding effect is obtained by the above, the diaphragm plate having the diaphragms 51 and 52 having the same inner diameter and a throttle hole sufficiently smaller than these inner diameters is provided between the two. A (flame holding plate) may be provided to obtain a flame holding action.

Further, in the above-mentioned embodiment, the heating system for the electric vehicle has been described, but the present invention may be applied to the heating system for the vehicle equipped with the air-cooled engine. Further, the present invention is not limited to the heating device for automobiles, but can be widely applied to liquid fuel combustion devices for various purposes.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid fuel combustion apparatus showing an embodiment of the present invention.

FIG. 2 is an overall system diagram of a heating device for an electric vehicle to which the device of the present invention is applied.

FIG. 3 is a block diagram of electric control in one embodiment of the present invention.

FIG. 4 is a timing chart showing the operation of the embodiment of the present invention.

[Explanation of Codes] 3 ... Water Pump, 4 ... Main Combustion Chamber, 5 ... Sub Combustion Chamber, 51 ... Sub Mixing Tube, 52 ... Sub Combustion Tube, 6 ... Ignition Device, 63 ... Fuel Supply Pipe, 7 ... For Combustion Air Blower, 8 ... heat exchanger.

Claims (3)

[Claims] 1. A fuel supply means for supplying liquid fuel, an air supply means for supplying combustion air, a combustion chamber for mixing and burning the liquid fuel and the combustion air, and a mixture of the liquid fuel and the combustion air. A liquid fuel combustion apparatus comprising an ignition device for igniting air and a heat exchanger for exchanging heat between a combustion gas burned in the combustion chamber and a heat medium, wherein the combustion chamber is located upstream of the air-fuel mixture. A sub-combustion chamber and a main combustion chamber located downstream of the sub-combustion chamber are provided, the sub-combustion chamber is configured to have a smaller volume than the main combustion chamber, and the ignition device includes the sub-combustion chamber. The liquid fuel combustion apparatus is arranged so as to ignite an air-fuel mixture in the room, and a flame holding portion for holding a flame ignited by the ignition device is formed in the auxiliary combustion chamber. . 2. The sub-combustion chamber is provided with a sub-mixing cylinder that mixes the liquid fuel and the combustion air, and a sub-combustion cylinder that burns a mixture of the liquid fuel and the combustion air mixed in the sub-mixing cylinder. The liquid fuel combustion apparatus according to claim 1, wherein the flame holding portion is formed by rapidly expanding the volume of the auxiliary combustion cylinder with respect to the auxiliary mixing cylinder. 3. The sub-mixing cylinder is provided with an air hole for swirling the combustion air, a fuel supply pipe of the fuel supply means, and the ignition device, and in the sub-mixing cylinder, The liquid fuel combustion apparatus according to claim 1 or 2, wherein the air-fuel mixture is ignited.