JP2013001627A - Fuel evaporation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel evaporation device capable of stably evaporating a liquid fuel independent of variation of ambient temperature.SOLUTION: An evaporation face 51 formed in a fuel evaporation channel 36 comprises a first evaporation face 51a at the upstream side and a second evaporation face 51b at the downstream side. The first evaporation face 51a is heated by a first heater 31-1 and the second evaporation face 51b is heated by a second heater 31-2. When the temperature of the first evaporation face 51a is lowered e.g. due to an increase in liquid fuel supply, the preset temperature of the second evaporation face 51b heated by the second heater 31-2 is changed from T1 to T2 (T2>T1) to increase the heating rate with the second heater 31-2 and raise the temperature of the second evaporation face 51b. Accordingly, the temperature lowering of the second evaporation face 51b linked with temperature lowering of the first evaporation face 51a is promptly avoided to enable stable evaporation of the liquid fuel.

Description

  The present invention relates to a fuel evaporation apparatus that evaporates liquid fuel used in a fuel cell system, and more particularly to a technique for stably evaporating fuel even when a temperature change occurs.

  In recent years, the use of various fuel cells has been studied due to the growing interest in global environmental problems. Among these, in the case of a highly efficient solid oxide fuel cell (SOFC), a gas containing a large amount of hydrogen is used as fuel, oxygen is used as an oxidant, hydrogen, carbon monoxide, and hydrocarbons are used. Power is generated by the electrochemical reaction. At this time, a method of reforming liquid fuel as fuel gas and supplying the obtained reformed gas to the fuel cell is adopted.

  As a liquid fuel to be supplied to the reformer, a liquid raw fuel of high carbon number organic liquid such as gasoline is used, and these liquid fuels are gasified by a fuel evaporator and introduced into the reformer. At this time, the fuel evaporator needs to stably gasify the liquid fuel, and it is desirable that the temperature of the fuel evaporation passage be kept substantially constant. That is, when the temperature of the fuel evaporation passage is not stable, heat may not be easily transmitted to the liquid fuel at an appropriate temperature, which causes a problem that coking occurs.

  As a solution to this problem, for example, as described in Japanese Patent Application Laid-Open No. 2006-327835 (Patent Document 1), the temperature of the entire evaporation surface is liquid-evaporated using a high-temperature gas used in a fuel cell system. A method is known in which fuel is evaporated by maintaining a temperature slightly higher than the temperature and supplying a sufficient amount of heat for evaporation.

JP 2006-327835 A

  However, in the conventional example disclosed in Patent Document 1 described above, when a device (for example, a reformer) that is operated at a temperature higher than the set temperature in the evaporator is connected to the downstream side of the evaporator. May be affected by the temperature of these high-temperature parts. In addition, since heat is taken away by evaporation in the fuel evaporation section, the evaporation surface of the evaporator also undergoes temperature fluctuations due to changes in the fuel amount. For this reason, there is a problem that it is difficult to evaporate the fuel in a stable state when the operating surface changes in the evaporation surface temperature of the evaporator.

  The present invention has been made to solve such a conventional problem, and the object of the present invention is to stably evaporate liquid fuel without being affected by changes in ambient temperature. It is to provide a fuel evaporation device.

  In order to achieve the above object, the invention according to claim 1 of the present application is a fuel evaporation device that includes a fuel evaporation passage and evaporates liquid fuel supplied from the outside, and passes through a first evaporation region in the fuel evaporation passage. A first heating means for heating the liquid fuel to be heated; a second heating means for heating a second evaporation area adjacent to the first evaporation area in the fuel evaporation passage; and a temperature of the first evaporation area. A temperature detecting means; and a control means for controlling a heating temperature by the first heating means and the second heating means, the control means in accordance with the temperature detected by the temperature detecting means. It is characterized in that the set temperature at the time of heating by the heating means is changed.

  In the fuel evaporation apparatus according to the present invention, the temperature of the first evaporation region is measured by the temperature detecting means, and the temperature of the second evaporation region adjacent to the first evaporation region is controlled according to the measured temperature. Temperature fluctuations can be complemented between the evaporation regions, and the temperature in the fuel evaporation passage can be stabilized. As a result, the liquid fuel can be stably gasified.

It is a block diagram which shows the structure of the fuel cell system with which the fuel evaporation apparatus which concerns on embodiment of this invention is used. It is explanatory drawing which shows the structure of the fuel evaporation apparatus which concerns on embodiment of this invention. It is a block diagram which shows the electric constitution of the fuel evaporation apparatus which concerns on embodiment of this invention. It is a timing chart which shows the temperature of each evaporation surface, and operation | movement of each heater when the whole evaporation surface is in a thermal equilibrium state. It is a timing chart which shows the temperature of each evaporation surface, and the operation | movement of each heater when the fuel evaporation apparatus which concerns on 1st Embodiment of this invention is not applied. It is a timing chart which shows the temperature of each evaporation surface, and the operation | movement of each heater when the fuel evaporation apparatus which concerns on 1st Embodiment of this invention is applied. It is a timing chart which shows the temperature of each evaporation surface, and the operation | movement of each heater when the fuel evaporation apparatus which concerns on 2nd Embodiment of this invention is not applied. It is a timing chart which shows the temperature of each evaporation surface, and the operation of each heater when the fuel evaporation system concerning a 2nd embodiment of the present invention is applied. It is a timing chart which shows the temperature of each evaporation surface, and the operation of each heater when the fuel evaporation system concerning a 3rd embodiment of the present invention is not applied. It is a timing chart which shows the temperature of each evaporation surface, and the operation of each heater at the time of applying the fuel evaporation system concerning a 3rd embodiment of the present invention. It is a block diagram which shows the electrical structure of the fuel evaporation apparatus which concerns on the modification of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Description of fuel cell system configuration]
FIG. 1 is a block diagram showing a configuration of a fuel cell system 100 in which a fuel evaporation device 14 according to an embodiment of the present invention is mounted. As shown in FIG. 1, the fuel cell system 100 includes a fuel cell 11 having a cathode 11a and an anode 11b, a reformer having a fuel reformer 15a and a combustion burner 15b for heating the fuel reformer 15a. Device 15. The reformed gas output from the fuel reformer 15a is supplied to the anode 11b. Further, the exhaust gas from the cathode 11a is supplied to the combustion burner 15b.

  Also, a first air blower 12 for supplying air to the cathode 11a of the fuel cell 11, a heat exchanger 13 for heating the air sent from the first air blower 12, and an outlet side of the anode 11b, A circulation blower 16 that circulates the exhaust gas to the fuel reformer 15 a and a branch valve 25 installed on the outlet side of the circulation blower 16 are provided.

  Further, a second air blower 17 that supplies air to the fuel reformer 15a, a fuel evaporator 14 that vaporizes liquid fuel sent from a fuel pump (not shown), and a third that supplies air to the combustion burner 15b. An air blower 20. Therefore, the air sent from the second air blower 17, the fuel gas vaporized by the fuel evaporator 14, and the anode exhaust gas sent via the branch valve 25 are supplied to the fuel reformer 15 a as a mixed gas. The

  Since the reformed gas reformed by the fuel reformer 15a is supplied to the anode 11b of the fuel cell 11 and air is supplied to the cathode 11a, a current flows between the cathode 11a and the anode 11b. The power can be supplied to a load (not shown).

  Next, a detailed configuration of the fuel evaporation device 14 which is a characteristic part of the present invention will be described with reference to FIGS. FIG. 3 is a cross-sectional view of the fuel evaporation device 14, and FIG. 2 is a block diagram showing an electrical configuration of the fuel evaporation device 14.

  As shown in FIG. 3, the fuel evaporation device 14 includes a fuel evaporation passage 36 having a hollow cylindrical shape, a fuel supply port 41 provided on the upstream side of the fuel evaporation passage 36, and a downstream side of the fuel evaporation passage 36. Evaporative gas outlet 42 provided.

  Further, a first heater 31-1, a second heater 31-2, and a third heater 31-3 are installed around the fuel evaporation passage 36 from the upstream side toward the downstream side. The first heater 31- The upstream area heated by 1 is the first evaporation surface 51a, the intermediate area heated by the second heater 31-2 is the second evaporation surface 51b, and the downstream area is heated by the third heater 31-3. This area is the third evaporation surface 51c. As shown in FIG. 2, the first to third heaters 31-1 to 31-3 are each connected to the temperature control unit 33 through the power supply line 34, and the electric power is controlled by the control of the temperature control unit 33. The supply is switched on and off to be controlled to a desired temperature.

  Therefore, the liquid fuel supplied from the fuel supply port 41 is injected into the fuel evaporation passage 36, and the injected liquid fuel is the evaporation surface 51 (first evaporation surface 51a, second evaporation surface) around the fuel evaporation passage 36. 51b, the third evaporation surface 51c) is supplied with heat and vaporized, and the vaporized fuel is sent to the outside via the evaporative gas outlet 42. In the present embodiment, the three heaters 31-1 to 31-3 are provided. However, the present invention is not limited to this, and may be two, or four or more.

  Further, the first temperature sensor 32-1 that measures the surface temperature of the first evaporation surface 51a, the second temperature sensor 32-2 that measures the surface temperature of the second evaporation surface 51b, and the surface temperature of the third evaporation surface 51c. A third temperature sensor 32-3 for measuring the temperature is provided, and the first to third temperature sensors 32-1 to 32-3 are connected to the temperature control unit 33 via the control line 35.

  The temperature control unit (control means) 33 can be configured by, for example, a microcomputer including a CPU, a RAM, a ROM, and various operators, and is detected by each temperature sensor 32-1 to 32-3. Based on the temperature data, control is performed to adjust the temperature of each of the heaters 31-1 to 31-3 by a procedure described later.

  Hereinafter, the fuel evaporation apparatus 14 according to the first to third embodiments of the present invention will be described in detail.

[Description of First Embodiment]
Before explaining the operation of the first embodiment, referring to the timing chart shown in FIG. 4, the first evaporation surface 51a, the second evaporation surface 51b, and the like when the fuel evaporation device 14 is in a thermal equilibrium state. The relationship between the temperature change of the third evaporation surface 51c and the on / off operations of the first to third heaters 31-1 to 31-3 will be described.

  FIG. 4 (1a) shows changes in the temperature of the first evaporation surface 51a (temperature detected by the first temperature sensor 32-1), and (1b) shows changes in the on / off state of the first heater 31-1. Show. 4 (2a) shows a change in the temperature of the second evaporation surface 51b (temperature detected by the second temperature sensor 32-2), and (2b) shows whether the second heater 31-2 is turned on or off. It shows a change. FIG. 4 (3a) shows the change in the temperature of the third evaporation surface 51c (temperature detected by the third temperature sensor 32-3), and (3b) shows the change in the on / off state of the third heater 31-3. Show.

  And the temperature control part 33 controls ON / OFF of each heater 31-1 to 31-3 so that the temperature of each evaporation surface 51a-51c may become preset temperature T1 (reference temperature) each preset. For example, as shown in FIG. 4 (1a), when the temperature of the first evaporation surface 51a exceeds the set temperature T1, the first heater 31-1 is turned off to stop the heat generation. If it falls below, the first heater 31-1 is turned on to generate heat. As a result, the temperature of the first evaporation surface 51a is controlled so as to fluctuate up and down around the set temperature T1, and on average, it is controlled to be substantially constant. At this time, since the first evaporation surface 51a is connected to the other evaporation surfaces (the second evaporation surface 51b and the third evaporation surface 51c), heat is exchanged between the evaporation surfaces, but each temperature sensor 32 is also used. Since each heater 31-1 to 31-3 is controlled to be turned on / off based on the temperature detected at -1 to 32-3, each of the evaporation surfaces 51a to 51c is maintained at a substantially constant temperature. In addition, the characteristic curve of the temperature change shown in FIG. 4 (1a) or the like is shown in a triangular wave shape for easy understanding. Actually, the curve is a smooth curve that fluctuates up and down. The same applies to other characteristic curves.

  Next, when the temperature control according to the present embodiment is not performed (that is, when the conventional control method is used), the second evaporation surface 51b and the third evaporation surface when the temperature of the first evaporation surface 51a decreases. The temperature change of the evaporation surface 51c will be described with reference to the timing chart shown in FIG. FIG. 5 (1a) shows the temperature change of the first evaporation surface 51a, (1b) shows the on / off change of the first heater 31-1, and (1c) shows the temperature drop level with respect to the set temperature T1. Yes. 5 (2a) shows the temperature change of the second evaporation surface 51b, and (2b) shows the ON / OFF change of the second heater 31-2. FIG. 5 (3a) shows the temperature change of the third evaporation surface 51c, and (3b) shows the ON / OFF change of the third heater 31-3.

  And in this example, the case where the temperature of the 1st evaporation surface 51a falls gradually with progress of time is shown. As a situation where such a temperature change occurs, for example, there is a case where the fuel supplied from the fuel supply port 41 shown in FIG. 2 increases. When the amount of fuel supplied into the fuel evaporation passage 36 increases, the amount of heat of evaporation evaporating from the first evaporation surface 51a heated by the first heater 31-1 increases. As shown, the time during which the temperature of the first evaporation surface 51a falls below the set temperature T1 increases, and the ON time of the first heater 31-1 becomes relatively longer than the OFF time. Further, when the amount of heat generated by the first heater 31-1 cannot cover the heat of vaporization required for evaporating the fuel, the first heater 31-1 is kept in the on-state (always turned on). However, the temperature of the first evaporation surface 51a continues to decrease.

  Further, since the first evaporation surface 51a and the second evaporation surface 51b are connected, as shown in FIG. 5 (2a), the time when the temperature of the second evaporation surface 51b eventually falls below the set temperature T1 increases, and the second The on time of the heater 31-2 becomes relatively longer than the off time, and the amount of heat generated by the second heater 31-2 increases.

  When the amount of heat generated by the second heater 31-2 increases to cover the amount of heat evaporated by the second evaporation surface 51b, the temperature of the second evaporation surface 51b can be maintained at the set temperature T1. However, the temperature decreasing tendency continues for the first evaporation surface 51a. In this case, the liquid fuel is supplied with heat from the first evaporation surface 51a and the second evaporation surface 51b, and vaporizes in stages. First, a low boiling point component (in the fuel) is generated by the first evaporation surface 51a. The component that tends to evaporate) evaporates, and then the high boiling point component (component that does not easily evaporate) in the fuel evaporates on the second evaporation surface 51b, so that the fuel cokes on the second evaporation surface 51b, etc. This problem is likely to occur.

  That is, in the temperature control method shown in FIG. 5 (a technique not employing the present invention), for example, when the amount of fuel supplied into the fuel evaporation passage 36 fluctuates, the supplied fuel is stably evaporated. It may not be possible to do so.

  Next, a temperature change when the temperature control according to the first embodiment of the present invention is performed when the temperature of the first evaporation surface 51a is lowered will be described with reference to a timing chart shown in FIG.

  In the fuel evaporation apparatus 14 according to the first embodiment, when the temperature of the first evaporation surface 51a that is the upstream region of the fuel evaporation passage 36 tends to decrease, the second evaporation surface 51b adjacent thereto is heated. By increasing the set temperature of the second heater 31-2, the amount of heat supplied to the second evaporation surface 51b is increased, and control is performed so that the liquid fuel sprayed in the fuel evaporation passage 36 is surely vaporized. To do.

  That is, in the first embodiment, the first evaporation surface 51a is the first evaporation region, the second evaporation surface 51b is the second evaporation region, the first heater 31-1 is the first heating means, The two heaters 31-2 are the second heating means, and the first temperature sensor 32-1 is the temperature detection means.

  In FIG. 6, (1a) shows the temperature change of the first evaporation surface 51a, (1b) shows the ON / OFF change of the first heater 31-1, and (1c) is the temperature drop level with respect to the set temperature T1. Is shown. 6 (2a) shows a change in the temperature of the second evaporation surface 51b, and (2b) shows a change in the on / off state of the second heater 31-2. FIG. 6 (3a) shows the temperature change of the third evaporation surface 51c, and (3b) shows the ON / OFF change of the third heater 31-3.

  As shown in the example of FIG. 5, for example, when the amount of evaporated fuel supplied from the fuel supply port 41 increases, the amount of heat supplied to the liquid fuel from the first heater 31-1 increases. As shown, the temperature of the first evaporation surface 51a, that is, the temperature detected by the first temperature sensor 32-1 decreases. Therefore, as shown in FIG. 6 (1b), the temperature control unit 33 has a relatively long on-time (Ton) with respect to the off-time (Toff), and is finally always on.

  In addition, when the temperature of the first evaporation surface 51a decreases and decreases to a preset lower limit threshold temperature Tth1 (a temperature lower by ΔT than the set temperature T1) as shown in FIG. As shown in FIG. 6 (2a), the controller 33 changes the set temperature T1 by the second heater 31-2 to T2 (where T2> T1). Accordingly, the second heater 31-2 is controlled to be turned off when the temperature of the second evaporation surface 51b is higher than the set temperature T2, and is turned on when the temperature is lower than that in FIG. 6 (2b). As shown, the ON time is controlled to be relatively longer than the OFF time. Therefore, the amount of heat generated by the second heater 31-2 is increased, and the temperature of the second evaporation surface 51b is controlled to be high.

  As a result, as shown in FIG. 5 (2a), it is possible to suppress the temperature of the second evaporation surface 51b from decreasing in conjunction with the temperature decrease of the first evaporation surface 51a. The liquid fuel that is not evaporated on the evaporation surface 51a can be heated and evaporated.

  Thus, in the fuel evaporation apparatus 14 according to the first embodiment, the temperature of the first evaporation surface 51a is detected, and when this temperature falls below the preset lower threshold temperature Tth1, the first evaporation surface 51a. The set temperature of the second evaporation surface 51b adjacent to the downstream side is increased. Specifically, a process of changing from T1 to T2 shown in FIG. 6 (2a) is performed. Therefore, the amount of heat generated by the second heater 31-2 for heating the second evaporation surface 51b can be increased at an early stage, and the second evaporation surface 51b is heated in response to the temperature decrease of the first evaporation surface 51a. It is possible to prevent the decrease, and sufficient heat can always be applied to the liquid fuel supplied to the fuel evaporation passage 36. As a result, the occurrence of problems such as coking can be avoided, and the liquid fuel can be stably vaporized.

  In the first embodiment described above, the first temperature sensor 32-1 is used to measure the temperature of the first evaporation surface 51a. However, the ratio between the on time and the off time of the first heater 31-1 is used. That is, it is also possible to detect the temperature drop of the first evaporation surface 51a based on the ratio between the on time ton and the off time toff shown in FIG. 6 (1b). Further, as a technique for detecting the temperature drop of the first evaporation surface 51a, detection is performed based on the difference between the measured average temperature within a certain time and the set temperature, or the hold value of the lowest temperature during the measurement is detected. It is also possible to detect based on the fact that the heater OFF time exceeds a certain value range.

  Furthermore, the change amount ΔT of the set temperature can be appropriately set according to the fuel to be evaporated. For example, when gasoline is used as the fuel, the initial set temperature T1 is set to 200 ° C., and the set temperature T2 at the time of temperature drop is set to a value of about 250 ° C., thereby suppressing the occurrence of coking. Is possible.

[Description of Second Embodiment]
Next, a second embodiment will be described. First, in the case where the temperature control according to the second embodiment is not performed (that is, when the conventional control method is used), the first evaporation surface 51a and the first evaporation surface when the temperature of the third evaporation surface 51c rises The temperature change of the 2 evaporation surface 51b is demonstrated with reference to the timing chart shown in FIG.

  FIG. 7 (1a) shows the temperature change of the first evaporation surface 51a, and (1b) shows the ON / OFF change of the first heater 31-1. 7 (2a) shows the temperature change of the second evaporation surface 51b, and (2b) shows the ON / OFF change of the second heater 31-2. FIG. 7 (3a) shows the temperature change of the third evaporation surface 51c, (3b) shows the on / off change of the third heater 31-3, and (3c) shows the temperature rise level with respect to the set temperature T1. Yes.

  In this example, as shown in FIG. 7 (3a), the temperature of the third evaporation surface 51c gradually increases with time. As a situation where such a temperature change occurs, for example, when the temperature of the fuel reformer 15a provided on the downstream side of the fuel evaporation device 14 or the fuel cell 11 (see FIG. 1) is higher than the evaporation temperature, The case where the temperature of the 3rd evaporation surface 51c greatly exceeds preset temperature T1 under the influence of temperature is mentioned.

  As shown in FIG. 7 (3a), when the temperature of the third evaporation surface 51c rises due to the influence of the reforming temperature or the like of the fuel reformer 15a, the temperature of the third evaporation surface 51c becomes equal to the set temperature T1. The exceeding time increases, and as shown in FIG. 7 (3b), the on-time (ton) of the third heater 31-3 decreases relative to the off-time (toff). Thereafter, when the temperature of the third evaporation surface 51c does not decrease, the third heater 31-3 is always turned off, and the temperature of the third evaporation surface 51c continues to increase.

  Further, since the third evaporation surface 51c and the second evaporation surface 51b on the upstream side thereof are connected, as shown in FIGS. 7 (2a) and (2b), the temperature of the second evaporation surface 51b eventually reaches the set temperature T1. The exceeding time increases, the off time of the second heater 31-2 increases relative to the on time, and the heat generation amount of the second heater 31-2 decreases.

  If the amount of heat generated by the second heater 31-2 can be reduced by a decrease in the amount of heat generated by the second heater 31-2, the second evaporation heated by the second heater 31-2 is possible. The surface 51b can be maintained at the set temperature T1. However, with respect to the third evaporation surface 51c, the temperature increasing trend is continued. Therefore, the temperature of the third evaporation surface 51c cannot be kept constant.

  That is, in the temperature control method shown in FIG. 7 (a technique that does not employ the present invention), for example, under the influence of the temperature of the fuel reformer 15a provided on the downstream side of the fuel evaporator 14 and the temperature of the fuel cell 11, When the temperature of the third evaporation surface 51c increases, the temperature at the time of evaporating the liquid fuel cannot be maintained constant, and the fuel cannot be stably evaporated.

  Next, a temperature change when the temperature control according to the second embodiment of the present invention is performed when the temperature of the third evaporation surface 51c rises will be described with reference to a timing chart shown in FIG.

  In the fuel evaporation apparatus 14 according to the second embodiment, when the temperature of the third evaporation surface 51c, which is the region on the downstream side of the fuel evaporation passage 36, tends to increase, it is adjacent to the upstream side of the third evaporation surface 51c. By reducing the set temperature of the second heater 31-2 for heating the second evaporation surface 51b, the amount of heat supplied to the second evaporation surface 51b is reduced, and the liquid fuel supplied into the fuel evaporation passage 36 Control to avoid transferring more heat than necessary.

  That is, in the second embodiment, the third evaporation surface 51c is the first evaporation region, the second evaporation surface 51b is the second evaporation region, the third heater 31-3 is the first heating means, The two heaters 31-2 are the second heating means, and the third temperature sensor 32-3 is the temperature detecting means.

  In FIG. 8, (1a) shows the temperature change of the first evaporation surface 51a, and (1b) shows the ON / OFF change of the first heater 31-1. 8 (2a) shows the temperature change of the second evaporation surface 51b, and (2b) shows the ON / OFF change of the second heater 31-2. FIG. 8 (3a) shows the temperature change of the third evaporation surface 51c, (3b) shows the on / off change of the third heater 31-3, and (3c) shows the temperature rise level with respect to the set temperature T1. Yes.

  As shown in the example of FIG. 7, for example, when the region on the downstream side of the fuel evaporation passage 36 is affected by the temperature of the fuel reformer 15a, the heat of the fuel reformer 15a is applied to the third evaporation surface 51c. As a result, the temperature of the third evaporation surface 51c rises as shown in FIG. 8 (3a). Therefore, as shown in FIG. 8 (3b), the temperature control unit 33 controls the third heater 31-3 so that the off time (Toff) is relatively longer than the on time (Ton), Finally, it is always turned off.

  Further, when the temperature of the third evaporation surface 51c rises and rises to a preset upper limit threshold temperature Tth2 (a temperature higher by ΔT than the set temperature T1) as shown in FIG. 8 (3c), the temperature As shown in FIG. 8 (2a), the controller 33 changes the set temperature T1 by the second heater 31-2 to T3 (where T3 <T1). As a result, the second heater 31-2 is controlled to turn off when the temperature of the second evaporation surface 51b exceeds the set temperature T3 and to turn on when the temperature falls below the set temperature T3. As shown, the ON time is controlled to be relatively shorter than the OFF time. Accordingly, the amount of heat generated by the second heater 31-2 is reduced, and the temperature of the second evaporation surface 51b is controlled to be low.

  As a result, as shown in FIG. 7 (2a), it is possible to suppress the temperature of the second evaporation surface 51b from increasing in conjunction with the increase in the temperature of the third evaporation surface 51c. The temperature of the evaporation surface 51b can be maintained at a substantially constant temperature.

  Thus, in the fuel evaporation apparatus 14 according to the second embodiment, the temperature of the third evaporation surface 51c is detected, and when this temperature exceeds the preset upper threshold temperature Tth2, the third evaporation surface 51c. Lower the set temperature of the second evaporation surface 51b adjacent to the upstream side. Specifically, a process of changing from T1 to T3 shown in FIG. 8 (2a) is performed. Accordingly, the amount of heat generated by the second heater 31-2 for heating the second evaporation surface 51b can be reduced, and the temperature of the second evaporation surface 51b rises in conjunction with the temperature decrease of the third evaporation surface 51c. This can be prevented, and stable heat can always be applied to the liquid fuel injected into the fuel evaporation passage 36. As a result, the liquid fuel can be vaporized stably by applying uniform heat.

  Similar to the first embodiment described above, also in the second embodiment, the ratio between the on time and the off time of the third heater 31-3, that is, the on time ton and the off time shown in FIG. 8 (3b). It is also possible to detect the temperature of the third evaporation surface 51c based on the ratio to toff.

[Description of Third Embodiment]
Next, a third embodiment will be described. First, when the temperature control according to the third embodiment is not performed (that is, when the conventional control method is used), the temperature of the first evaporation surface 51a is lowered, and then the temperature of the third evaporation surface 51c is decreased. The temperature change of the second evaporation surface 51b when it rises will be described with reference to the timing chart shown in FIG.

  FIG. 9 (1a) shows the temperature change of the first evaporation surface 51a, (1b) shows the on / off change of the first heater 31-1, and (1c) shows the temperature drop level with respect to the set temperature T1. ing. 9 (2a) shows the temperature change of the second evaporation surface 51b, and (2b) shows the ON / OFF change of the second heater 31-2. FIG. 9 (3a) shows the temperature change of the third evaporation surface 51c, (3b) shows the on / off change of the third heater 31-3, and (3c) shows the temperature rise level with respect to the set temperature T1. Yes.

  In this example, as shown in FIG. 9 (1a), the temperature of the first evaporation surface 51a gradually decreases with time, and as shown in FIG. 9 (3a), the temperature of the third evaporation surface 51c. Shows a case where the value gradually increases with time. As a situation where such a temperature change occurs, for example, when the fuel supplied from the fuel supply port 41 shown in FIG. 2 increases and the fuel reformer 15a provided on the downstream side of the fuel evaporation device 14 Or the case where the temperature of the fuel cell 11 (refer FIG. 1) is higher than evaporation temperature is mentioned.

  When the amount of fuel supplied into the fuel evaporation passage 36 increases, the amount of heat transferred from the first evaporation surface 51a heated by the first heater 31-1 to the fuel passing through the first evaporation surface 51a increases. As shown in FIG. 9 (1a), the time during which the temperature of the first evaporation surface 51a falls below the set temperature T1 increases, and the ON time of the first heater 31-1 increases relatively with respect to the OFF time. Further, when the amount of heat generated by the first heater 31-1 cannot cover the heat of vaporization required for evaporating the fuel, the first heater 31-1 is kept in the on-state (always turned on). However, the temperature of the first evaporation surface 51a continues to decrease. Therefore, as shown in FIG. 9 (1c), the temperature of the first evaporation surface 51a tends to decrease with the passage of time.

  On the other hand, as shown in FIG. 9 (3a), when the temperature of the third evaporation surface 51c increases, the time during which the temperature of the third evaporation surface 51c exceeds the set temperature T1 increases, as shown in FIG. 9 (3b). The on-time of the third heater 31-3 decreases relative to the off-time. Thereafter, when the temperature of the third evaporation surface 51c does not decrease, the third heater 31-3 is always turned off, and the temperature of the third evaporation surface 51c continues to increase. Therefore, the temperature of the third evaporation surface 51c increases with time as shown in FIG. 9 (3c).

  Thus, when no control is performed on the temperature decrease of the first evaporation surface 51a and the temperature increase of the third evaporation surface 51c, the temperature decreases on the upstream side of the fuel evaporation passage 36, and the downstream side As a result, the temperature rises, the temperature inside the fuel evaporation passage 36 is not uniformized, and the liquid fuel cannot be stably evaporated.

  Next, the temperature change when the temperature control according to the third embodiment of the present invention is performed when the temperature of the first evaporation surface 51a decreases and the temperature of the third evaporation surface 51c increases will be described. This will be described with reference to the timing chart shown in FIG.

  In the fuel evaporation device 14 according to the third embodiment, the temperature of the first evaporation surface 51 a that is the upstream region of the fuel evaporation passage 36 tends to decrease, and the first region that is the downstream region of the fuel evaporation passage 36 is used. When the temperature of the third evaporation surface 51c tends to increase, the temperature of the second evaporation surface 51b is controlled so that the temperature in the fuel evaporation passage 36 is stabilized.

  In other words, in the third embodiment, the first evaporation surface 51a and the third evaporation surface 51c are the first evaporation regions, of which the first evaporation surface 51a is the upstream evaporation region and the third evaporation surface 51c is the downstream side. It is an evaporation area. The second evaporation surface 51b is a second evaporation region. The first heater 31-1 and the third heater 31-3 are first heating means, of which the first heater 31-1 is an upstream heating means and the third heater 31-3 is a downstream heating means. is there. The second heater 31-2 is a second heating means. Further, the first temperature sensor 32-1 and the third temperature sensor 32-3 are temperature detection means. Among these, the first temperature sensor 32-1 measures the temperature of the upstream evaporation region, and the third temperature sensor 32. -3 measures the temperature in the downstream evaporation zone.

  In FIG. 10, (1a) shows the temperature change of the first evaporation surface 51a, (1b) shows the ON / OFF change of the first heater 31-1, and (1c) is the temperature drop level with respect to the set temperature T1. Is shown. FIG. 10 (2a) shows the temperature change of the second evaporation surface 51b, and (2b) shows the ON / OFF change of the second heater 31-2. FIG. 10 (3a) shows the temperature change of the third evaporation surface 51c, (3b) shows the on / off change of the third heater 31-3, and (3c) shows the temperature rise level with respect to the set temperature T1. Yes.

  As shown in the example of FIG. 9, for example, when the amount of evaporated fuel supplied from the fuel supply port 41 increases, the amount of heat supplied to the liquid fuel from the first heater 31-1 increases. As shown, the temperature of the first evaporation surface 51a decreases. Accordingly, as shown in FIG. 10 (1b), the temperature control unit 33 controls the on / off of the first heater 31-1 so that the on time (Ton) is relatively longer than the off time (Toff). Finally, it is always turned on.

  Further, as shown in FIG. 10 (1c), when the temperature of the first evaporation surface 51a decreases and falls below the lower limit threshold temperature Tth1, the set temperature of the second evaporation surface 51b becomes the same as in the first embodiment described above. T1 is changed to T2 (where T2> T1). Therefore, the second heater 31-2 is controlled to turn off when the temperature of the second evaporation surface 51b exceeds T2 and to turn on when it falls below, as shown in FIG. 10 (2b). The ON time is controlled to be relatively longer than the OFF time. Therefore, the amount of heat generated by the second heater 31-2 is increased, and the temperature of the second evaporation surface 51b is controlled to be high.

  On the other hand, when the temperature of the third evaporation surface 51c rises, the temperature controller 33 changes the off time (Toff) with respect to the on time (Ton) of the third heater 31-3, as shown in FIG. 10 (3b). Control to be relatively long. Thereafter, even if the temperature of the third evaporation surface 51c rises and rises to the upper threshold temperature Tth2 at time q1 shown in FIG. 10 (3c), the set temperature by the second heater 31-2 is not changed. In other words, in this situation, the set temperature of the second heater 31-2 is changed to T2 in order to avoid the influence of the temperature drop of the first evaporation surface 51a on the upstream side. Even when the temperature of the third evaporation surface 51c exceeds the upper threshold temperature Tth2, the set temperature of the second heater 31-2 is maintained at T2.

  After that, when the temperature of the third evaporation surface 51c further rises and exceeds the upper limit allowable temperature TUL higher than the upper limit threshold temperature Tth2 at time q2, the set temperature of the second heater 31-2 is changed from T2 to T1. Process to return to. This prevents the temperature of the second evaporation surface 51b from rising excessively.

  In this way, in the fuel evaporation device 14 according to the third embodiment, when the temperature of the first evaporation surface 51a decreases and falls below the lower limit threshold temperature Tth1, the set temperature of the second evaporation surface 51b is set to T1. By changing from T2 to T2, the amount of heat generated by the second heater 31-2 is increased to prevent the temperature of the second evaporation surface 51b from being lowered. When the set temperature of the second evaporation surface 51b is T2, and the temperature of the third evaporation surface 51c exceeds the upper threshold temperature Tth2, the set temperature of the second evaporation surface 51b is set to T2. If the temperature of the third evaporation surface 51c further increases and exceeds the upper limit allowable temperature TUL (> Tth2), the set temperature of the second evaporation surface 51b is controlled to return to T1.

  Accordingly, the set temperature of the second evaporation surface 51b is appropriately controlled based on the temperature of the first evaporation surface 51a on the upstream side and the temperature of the third evaporation surface 51c on the downstream side. The liquid fuel flowing into the evaporation passage 36 can be stably evaporated.

  Here, in the example shown in FIG. 10, the example in which the temperature of the first evaporation surface 51 a first decreases and then the temperature of the third evaporation surface 51 c increases, but first the temperature of the third evaporation surface 51 c has been described. The temperature may rise and then the temperature of the first evaporation surface 51a may drop. This case will be described below.

  When the evaporation surface 51 is in a thermal equilibrium state, when the temperature of the third evaporation surface 51c rises and exceeds the upper threshold temperature Tth2 as shown in FIG. 8 (3c), the second evaporation surface 51b The set temperature is changed from T1 to T3 (T3 <T1). Thereafter, even when the temperature of the first evaporation surface 51a decreases and falls below the lower limit threshold temperature Tth1 shown in FIG. 10 (1c), the set temperature of the second evaporation surface 51b maintains T3. Then, when the temperature of the first evaporation surface 51a further decreases and falls below the lower limit allowable temperature TLL shown in FIG. 10 (1c), the set temperature of the second evaporation surface 51b is controlled to return to T1.

  Therefore, even if the temperature of the third evaporation surface 51c first increases and then the temperature of the first evaporation surface 51a decreases, the set temperature of the second evaporation surface 51b is the first evaporation on the upstream side. The liquid fuel flowing into the fuel evaporation passage 36 can be stably evaporated by being appropriately controlled based on the temperature of the surface 51a and the temperature of the third evaporation surface 51c on the downstream side.

[Explanation to modification]
Next, a modified example of the fuel evaporation apparatus according to each embodiment described above will be described. FIG. 11 is a block diagram showing a configuration of a fuel evaporation device 14a according to a modification. In each of the above-described embodiments, examples in which the first heater 31-1 to the third heater 31-3 that generate heat when supplied with electric power have been described as the heating means. However, the heating means according to the present invention uses electric power. It is not limited to a thing, It is also possible to use heating gas.

  As shown in FIG. 11, a flow path (gas inflow path) into which the heated gas flows is provided in a region corresponding to the first evaporation surface 51a, and this gas inflow path is referred to as a first heater 31-1. That is, by supplying a heating gas used in the fuel cell system to the gas inflow path, the first evaporation surface 51a is heated and the liquid fuel is heated. In addition, by providing the flow rate adjustment valve 61 at the inlet of the gas inflow path, it is possible to control the flow rate of the heated gas and thus the temperature of the first evaporation surface 51a.

  As mentioned above, although the fuel evaporation apparatus of this invention was demonstrated based on embodiment of illustration, this invention is not limited to this, The structure of each part is replaced with the thing of the arbitrary structures which have the same function. Can do.

  For example, in each of the above-described embodiments, an example in which three heaters (first to third heaters 31-1 to 31-3) are provided as means for heating the evaporation surface 51 has been described. It is not limited to this, It is good also as a structure which provides three or more heaters. The first and second embodiments can be applied to the case where two heaters are provided.

  The present invention can be used to stably gasify liquid fuel.

DESCRIPTION OF SYMBOLS 11 Fuel cell 11a Cathode 11b Anode 12 1st air blower 13 Heat exchanger 14, 14a Fuel evaporator 15 Reformer 15a Fuel reformer 15b Combustion burner 16 Circulation blower 17 2nd air blower 20 3rd air blower 25 Branch valve 31-1 to 31-3 First to third heaters 32-1 to 32-3 First to third temperature sensors 33 Temperature controller 34 Power supply line 35 Control line 36 Fuel evaporating passage 41 Fuel supply port 42 Evaporating gas outlet 51 Evaporation Surface 51a First Evaporation Surface 51b Second Evaporation Surface 51c Third Evaporation Surface 61 Flow Control Valve 100 Fuel Cell System Tth1 Lower Threshold Temperature Tth2 Upper Threshold Temperature TLL Lower Threshold Temperature TUL Upper Threshold Temperature

Claims (6)

In a fuel evaporation device that includes a fuel evaporation passage and evaporates liquid fuel supplied from outside,
First heating means for heating the liquid fuel passing through the first evaporation region in the fuel evaporation passage;
A second heating means for heating a second evaporation region adjacent to the first evaporation region in the fuel evaporation passage;
Temperature detecting means for detecting the temperature of the first evaporation region;
Control means for controlling the heating temperature by the first heating means and the second heating means,
The control means includes
A fuel evaporation apparatus, wherein a set temperature when heating by the second heating means is changed according to a temperature detected by the temperature detecting means. The second evaporation region is adjacent to the downstream side of the first evaporation region with respect to the supply direction of the liquid fuel,
The control means includes
When the temperature of the first evaporation region detected by the temperature detection means is lower than a preset lower threshold temperature, the set temperature for heating by the second heating means is higher than a preset reference temperature The fuel evaporation apparatus according to claim 1, wherein the fuel evaporation apparatus is changed to a temperature. The second evaporation region is adjacent to the upstream side of the first evaporation region with respect to the supply direction of the liquid fuel,
The control means includes
When the temperature of the first evaporation region detected by the temperature detection unit is higher than a preset upper threshold temperature, the set temperature for heating by the second heating unit is lower than a preset reference temperature The fuel evaporation apparatus according to claim 1, wherein the fuel evaporation apparatus is changed to a temperature. The first evaporation region includes an upstream evaporation region adjacent to the upstream side of the second evaporation region with respect to the supply direction of the liquid fuel, and a downstream evaporation region adjacent to the downstream side,
The second heating means includes an upstream heating means for heating the upstream evaporation area, and a downstream heating means for heating the downstream evaporation area,
The temperature detecting means measures the temperature of the upstream evaporation region and the temperature of the downstream evaporation region;
The control means includes
When the temperature of the upstream evaporation region falls below a preset lower threshold temperature, the set temperature when heating by the second heating means is changed to a temperature higher than a preset reference temperature, and then the downstream 2. The control according to claim 1, wherein when the temperature of the side evaporation region exceeds a preset upper limit allowable temperature, control is performed so as to return the set temperature when heated by the second heating means to the reference temperature. Fuel evaporation system. The first evaporation region includes an upstream evaporation region adjacent to the upstream side of the second evaporation region with respect to the supply direction of the liquid fuel, and a downstream evaporation region adjacent to the downstream side,
The second heating means includes an upstream heating means for heating the upstream evaporation area, and a downstream heating means for heating the downstream evaporation area,
The temperature detecting means measures the temperature of the upstream evaporation region and the temperature of the downstream evaporation region;
The control means includes
When the temperature of the downstream evaporation region exceeds a preset upper threshold temperature, the set temperature when heating by the second heating means is changed to a temperature lower than a preset reference temperature, and then the upstream The control is performed so as to return the set temperature when heating by the second heating means to the reference temperature when the temperature of the side evaporation region falls below a preset lower limit allowable temperature. Fuel evaporation system.   At least one of the first heating unit and the second heating unit includes a gas inflow path, and by supplying a high temperature gas to the gas inflow path, the first evaporation area and the second evaporation area The fuel evaporation apparatus according to any one of claims 1 to 5, wherein a target region is heated.

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