JP4548722B2 - Cogeneration equipment - Google Patents

Description

  The present invention relates to a cogeneration apparatus, and more particularly to a cogeneration apparatus having means for preventing freezing of condensed water generated by heat exchange.

In recent years, the necessity of protecting the global environment has been spread, and a cogeneration apparatus as a private power generation facility that generates power and hot water using an engine such as a gas engine that uses city gas as fuel as a power source has attracted attention. In the exhaust heat recovery device used in this type of cogeneration device or the like, condensed water is generated when the exhaust gas is cooled by the exhaust heat exchanger. Therefore, a waste heat recovery device has been proposed in which a drain trap is provided at the bottom of the muffler through which the exhaust passes, and the condensed water accumulated in the drain trap is discharged through the drain passage (for example, a special feature (Kaihei 11-72018).
Japanese Patent Laid-Open No. 11-72018

  Condensate generated while the medium recovered by the cogeneration system is heated to a normal stable temperature is blown away by the momentum of the exhaust, so even if the operation is stopped there, almost no condensed water is present on the exhaust path. Does not remain.

  Further, when the operation is started in a state where the installation environment temperature is below the freezing point, the condensed water generated may adhere to the inner wall of the exhaust system and freeze at the beginning of the operation. However, the frozen condensed water is heated and melted by the exhaust gas before the exhaust path is blocked, and in this case, too, the condensed water does not remain on the exhaust system path.

  However, if the operation is stopped for some reason immediately after the operation is started at a temperature below the freezing point, the condensed water may remain on the exhaust path without being blown off by the exhaust. If left in a freezing environment, the condensed water remaining on the exhaust path will freeze. Then, when the operation is started thereafter, the newly generated condensed water adheres to the frozen condensed water and freezes. As a result, the frozen condensed water may block the exhaust circuit and hinder the operation.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a cogeneration apparatus capable of preventing the exhaust path from being blocked by condensed water frozen in the exhaust path.

  The present invention provides an engine, a generator driven by the engine, a heat exchanger that recovers thermal energy from exhaust heat of the engine, and supplies the thermal energy recovered by the heat exchanger to an external heat load. In a cogeneration apparatus having a heat medium circulation path and an exhaust path for exhausting the engine exhaust to the outside, an engine stop request detection unit, an environmental temperature sensor for sensing the environmental temperature of the exhaust path, and the heat A heat medium sensor that senses the temperature of the heat medium downstream from the exchanger, and the engine temperature when the sensed environmental temperature is below freezing and the sensed temperature of the heat medium is below a preset reference temperature. There is a first feature in that an engine control unit that suspends execution of the stop request and continues the operation of the engine is provided.

  In addition, the present invention has a second feature in that the engine control unit releases the suspension of the stop request when the temperature of the heat medium exceeds the reference temperature.

  Furthermore, the present invention has a third feature in that the engine control unit uses the engine speed target value for idling while the stop request is pending.

  According to the present invention having the above characteristics, the exhaust temperature is sufficient to blow the condensed water in a situation where the exhaust path is placed below the freezing point where the condensed water may freeze. When the temperature of the heat medium does not reach the reference temperature indicating that the engine is not stopped. That is, the operation of stopping in a short time is avoided, and the condensed water does not remain in the exhaust path, so that it is possible to prevent the condensed path from freezing and closing the exhaust path.

  According to the second feature, since the engine operation is continued until the temperature of the heat medium becomes higher than the reference temperature, the engine is warmed up and the exhaust gas is heated to a temperature sufficient to blow off condensed water from the exhaust path. It is judged that Accordingly, since the exhaust temperature is sufficiently high during normal operation, no condensed water remains on the exhaust path.

  According to the third feature, when the engine is idling, the exhaust temperature is high and the amount of condensed water generated is small, so that the exhaust path can be more effectively prevented from freezing. Therefore, an operation capable of preventing freezing can be achieved with minimum energy consumption.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 is a block diagram showing a configuration of an exhaust heat recovery apparatus used in the cogeneration apparatus. The exhaust heat recovery apparatus 1 includes an engine 2 and a generator 3 driven by the engine 2. The engine 2 is provided with an oil pan 4 for storing lubricating oil. The oil pan 4 is provided with an oil heat exchanger (oil cooler) 5 that performs heat exchange between the oil in the oil pan 4 and the heat medium.

  Above the exhaust heat recovery apparatus 1, an air filter 7 that cleans the air taken into the cylinder head 6 of the engine 2 and control devices such as the ECU 30, the power supply unit 31, and the motor driver unit 32 are provided. The ECU 30 has an electronic governor device that converges the rotational speed of the engine 2 to a target value. The control device such as the ECU 30 is preferably installed in a room separated from the lower space by a partition plate in order to make it less susceptible to the thermal influence of the engine 2.

  The exhaust heat recovery apparatus 1 includes a heat medium, that is, a cooling water circulation path 12 in order to recover the exhaust heat generated as the engine 2 is operated. The circulation path 12 is set so that the cooling water is conveyed in the order of the oil heat exchanger 5, the exhaust heat exchanger 9, the exhaust manifold 8, and the cylinder head 6 of the engine 2 in order to efficiently recover the exhaust heat of the engine 2. Has been.

  The cooling water circulation path 12 is provided with water temperature sensors (heat medium sensors) 33 and 34 for detecting the temperature of the cooling water. The water temperature sensor 33 is provided in the cylinder head 6, and the water temperature sensor 34 is provided downstream from the installation position of the water temperature sensor 33, for example, near the outlet of the exhaust heat recovery apparatus 1 for supplying hot water to an external heat load. The reason why the water temperature sensors 33 and 34 are provided at two locations is to detect the presence or absence of cooling water in the circulation path 12 (see Japanese Patent Application Laid-Open No. 2003-21393). Therefore, when detecting the presence or absence of cooling water by other means, one of the water temperature sensors 33 and 34 can be omitted. Further, the setting position of the water temperature sensor is not limited to these positions.

  The exhaust heat recovery apparatus 1 is provided with an interior temperature sensor 35 that senses the interior temperature. In the exhaust heat recovery device 1, a ventilation system that introduces air into the cabinet from the outside using an electric fan and guides the air upward by an internal cooling fan and a hose and exhausts the air from a duct near the ceiling to the outside. adopt. Therefore, the bottom of the cabinet tends to be low temperature. Therefore, if the inside temperature sensor 35 is installed near the exhaust outlet of the exhaust heat exchanger 9 at the bottom of the inside where the exhaust heat recovery apparatus 1 is expected to be the lowest temperature, the environmental temperature of the exhaust system It is convenient to obtain condition data for detecting freezing in the exhaust system by sensing the above.

  A water pump 10 for circulating the heat medium is provided on the inlet side of the heat medium circulation path 12. With this arrangement, contact between the water pump 10 and the high-temperature heat medium is avoided, so that the seal member and the like are not easily deteriorated, and the life of the water pump 10 is extended.

  The heat medium fed by the water pump 10 circulates in order through the oil heat exchanger 5, the exhaust heat exchanger 9, the exhaust manifold 8, and the cylinder head 6 of the engine 2 to recover the exhaust heat of the engine 2. That is, the heat medium is introduced into the oil heat exchanger 5 in the oil pan 4, and heat is exchanged with the oil recovered from the engine 2 to cool the oil and obtain heat therefrom. Subsequently, the heat medium exchanges heat with the exhaust from the engine 2 in the exhaust heat exchanger 9 to obtain heat. The heat medium that has risen in temperature by obtaining heat in the oil heat exchanger 5 and the exhaust heat exchanger 9 is further supplied to a cylinder wall of the engine 2 and a pipe provided in the cylinder head 6, that is, a cooling unit and a cylinder head including a water jacket 6A. Heat is recovered through 6, and the temperature is further increased.

  The heat medium whose temperature has increased by collecting the exhaust heat is circulated to an external heat load such as a boiler unit. The exhaust heat recovery apparatus 1 is provided with a thermo cover 16 incorporating a thermostat. By the action of the thermostat, the thermo cover 16 can be closed at a temperature lower than a preset temperature so that the heat medium is not circulated. .

  On the other hand, the exhaust from the engine 2 is discharged to the outside through the exhaust manifold 8, the exhaust heat exchanger 9, and a plurality of exhaust mufflers.

  FIG. 3 is a perspective view showing the configuration of the exhaust system. A plurality of exhaust mufflers 23, 25, and 27 are provided in the exhaust system. The first exhaust hose 17 drawn from the bottom of the exhaust heat exchanger 9 disposed at the lower part of the exhaust heat recovery device 1 is connected to an exhaust temperature sensor hose 19 via an exhaust pipe 18. The exhaust temperature sensor hose 19 is connected to the second exhaust hose 21 via the exhaust temperature sensor pipe 20. An exhaust temperature sensor 22 is attached to the exhaust temperature sensor pipe 20. The upper end of the second exhaust hose 21 extending almost directly above is connected to the upper portion of the first exhaust muffler 23.

  The upper end of the third exhaust hose 24 is connected to the lower part of the first exhaust muffler 23. The lower end of the third exhaust hose 24 is connected to the second exhaust muffler 25. The lower end of the fourth exhaust hose 26 is connected to the lower part of the second exhaust muffler 25. The fourth exhaust hose 26 extends upward, and its upper end is connected to the upper part of the third exhaust muffler 27 located at the upper part of the exhaust heat recovery apparatus 1. A duct 274 having an exhaust port is attached to the upper portion of the third exhaust muffler 27. A drain passage including a drain hose 28 and a drain pipe 29 is connected to the lower surface of the third exhaust muffler 27.

  The shell or housing of the exhaust heat exchanger 9 is formed of a metal material such as stainless steel, but the first and second exhaust mufflers 23 and 25 and the third exhaust muffler 27 constitute an exhaust passage having a lowered temperature. Each may be formed of a blow molded product of a resin material (for example, polypropylene).

  Exhaust flow indicated by arrows in FIG. 3 will be described. The exhaust of the engine 2 is introduced into the exhaust heat exchanger 9 from above. In the exhaust heat exchanger 9, heat is exchanged with the cooling water conveyed through the exhaust heat exchanger portion of the circulation path 12 piped inside. The exhaust cooled in the exhaust heat exchanger 9 is introduced into the first exhaust muffler 23 via the first exhaust hose 17, the exhaust pipe 18, the exhaust temperature sensor hose 19, the exhaust temperature sensor pipe 20, and the second exhaust hose 21. Thus, the first stage mute is performed.

  Exhaust gas discharged from the first exhaust muffler 23 is introduced into the second exhaust muffler 25 and silenced in the second stage. The exhaust discharged from the second exhaust muffler 25 is guided further upward to reach the third exhaust muffler 27, and is silenced in three stages by the third exhaust muffler 27, and the exhaust is discharged to the outside from the duct 274.

  The exhaust of the engine 2 is cooled by taking heat away from each of the heat exchange units described above. At this time, moisture in the exhaust gas is condensed to generate condensed water. Condensed water generated in the exhaust system is conveyed to the third exhaust muffler 27 according to the flow of the exhaust, and is discharged to the outside through the drain hose 28 and the drain pipe 29.

  Condensate generated while the medium recovered by the cogeneration system is heated to a normal stable temperature is blown away by the momentum of the exhaust, so even if the operation is stopped there, almost no condensed water is present on the exhaust path. Does not remain.

  Further, when the operation is started in a state where the installation environment temperature is below the freezing point, the condensed water generated may adhere to the inner wall of the exhaust system and freeze at the beginning of the operation. However, the frozen condensed water is heated and melted by the exhaust gas before the exhaust path is blocked, and in this case, too, the condensed water does not remain on the exhaust system path.

  However, if the operation is stopped for some reason immediately after the operation is started at a temperature below the freezing point, the condensed water may remain on the exhaust path without being blown off by the exhaust. If left in a freezing environment, the condensed water remaining on the exhaust path will freeze. Then, when the operation is started thereafter, if the newly generated condensed water adheres to the frozen condensed water and freezes, the frozen condensed water will block the exhaust circuit, which will hinder the operation. It can happen. Therefore, in this embodiment, the following measures are taken to prevent the connection portion and the narrow portion from being blocked due to this freezing.

  FIG. 1 is a block diagram showing the main functions of an ECU according to an embodiment of the present invention. In FIG. 1, the internal temperature sensor 35 is installed in the vicinity of the exhaust heat exchanger 9 as described above, and senses the environmental temperature of the exhaust system. The water temperature sensor 34 detects the temperature of the cooling water downstream from the most downstream heat exchange section (engine cylinder head 6). The stop request input unit 36 inputs an engine stop request STOP to the engine control unit 37 when the heat request from the external heat load is lost or when an operation stop instruction is input from the control panel.

  The environmental temperature determination unit 38 determines whether the environmental temperature T1 of the exhaust system detected by the internal temperature sensor 35 is below freezing (0 ° C. or lower). If the environmental temperature T1 is 0 ° C. or lower, the environmental low temperature signal AL is set to a high level (H).

  The water temperature determination unit 39 determines whether or not the cooling water temperature T2 detected by the water temperature sensor 34 is equal to or lower than the reference temperature Tref. The reference temperature Tref is a temperature at which it can be determined that the exhaust temperature does not cause condensed water to be generated in the exhaust path and that the condensed water can be blown away. The reference temperature Tref is 75 ° C. as an example. The reason why the cooling water temperature is compared with the reference temperature Tref instead of the exhaust temperature is that the temperature change of the cooling water is more gradual and is more reliable than the judgment based on the exhaust temperature. If the cooling water temperature T2 is equal to or lower than the temperature Tref, the cooling water low temperature signal CL is set to a high level (H).

  The engine control unit 37 reads the environmental low temperature signal AL and the cooling water low temperature signal CL when the engine stop request STOP is input, and outputs an engine stop command when at least one of them is at a low level. Then, the engine 2 is stopped. This is because if the environmental temperature is not 0 ° C. or less, the condensed water generated does not have to be frozen even when the engine 2 is stopped. Also, if the cooling water temperature is not 75 ° C. or less, it is judged that the exhaust temperature is high and condensate is hardly generated, and the condensate that has been generated is blown off and does not remain in the exhaust path. is there.

  On the other hand, when the environmental low temperature signal AL and the cooling water low temperature signal CL are both at the high level, generation and freezing of condensed water are expected. The engine stop command is not output until one of the low temperature signals CL becomes low level. That is, the engine stop request is suspended, and the rotation state of the engine 2 is maintained. When the engine stop request is suspended, the engine speed target value is set for the idle speed, and the engine is operated with the minimum energy consumption. When the engine 2 is idling, the generator stops its output and operates without load.

  FIG. 4 is a flowchart corresponding to the function of FIG. In step S1, it is determined whether or not there is an engine stop request STOP. If there is a stop request STOP, it is determined in step S2 whether or not the environmental temperature T1 of the exhaust system is below the freezing point. If the environmental temperature T1 is below the freezing point, the process proceeds to step S3 to determine whether or not the cooling water temperature T2 is equal to or lower than a predetermined reference temperature Tref. If step S3 is negative or step S2 is negative, it is determined that there is no risk of freezing of condensed water or that condensed water is discharged from the exhaust system, and the process proceeds to step S4 to output an engine stop command. . As a result, the engine 2 stops immediately.

  If step S3 is positive, that is, if the environmental temperature T1 is below the freezing point and the cooling water temperature T2 is also a low temperature below the reference temperature Tref, the engine stop command is not output and the process proceeds to step S5 to determine whether idling is in progress That is, it is determined whether or not the engine speed target value for idling has been reached. If it is during idling, it will progress to step S2. If the engine is not idling, the process proceeds to step S6 and the engine speed target value is switched to idling. Note that step S5 and step S6 may be omitted, and if step S3 is positive, the process may proceed to step S2.

  In this embodiment, when the ambient temperature is such that there is no risk of freezing even if condensate remains, and when it is determined that the condensate will be hot and will be blown out of the exhaust system, Respond to stop requests immediately. On the other hand, if the condensate remains at an environmental temperature that may cause freezing, or if it is determined that the condensate will not be blown out of the exhaust system at a relatively low temperature, an engine stop request is required. Hold the engine to keep the engine running. This avoids short-time operation that can cause the condensed water to freeze.

  In addition, it is one of the application examples within the scope of the present invention to provide a function of giving priority to the engine stop only when the engine stop request is highly urgent.

It is a principal part functional block diagram of the cogeneration apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the cogeneration apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the structure of the engine exhaust system of the cogeneration apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the principal part process of the cogeneration apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Waste heat recovery apparatus, 2 ... Engine, 3 ... Generator, 5 ... Oil heat exchanger, 6 ... Cylinder head, 8 ... Exhaust manifold, 9 ... Exhaust heat exchanger, 12 ... Circulation path, 19, 21, 24 , 26 ... exhaust hose, 22 ... exhaust temperature sensor, 23 ... first exhaust muffler, 25 ... second exhaust muffler, 27 ... third exhaust muffler, 30 ... ECU, 34 ... water temperature sensor, 35 ... internal temperature sensor, 37 ... engine control unit, 38 ... environmental temperature judgment unit, 39 ... water temperature judgment unit

Claims (3)

An engine, a generator driven by the engine, a heat exchanger for recovering heat energy from the exhaust heat of the engine, and circulation of a heat medium for supplying the heat energy recovered by the heat exchanger to an external heat load A cogeneration apparatus having a road and an exhaust path for exhausting the exhaust of the engine to the outside,
An engine stop request detector,
An environmental temperature sensor for sensing an environmental temperature of the exhaust path;
A heat medium sensor for sensing the temperature of the heat medium downstream from the heat exchanger;
An engine control unit that suspends execution of an engine stop request and continues engine operation when the detected environmental temperature is below freezing and the detected temperature of the heat medium is equal to or lower than a preset reference temperature A cogeneration apparatus characterized by comprising:   The cogeneration apparatus according to claim 1, wherein the engine control unit releases the suspension of the stop request when the temperature of the heat medium exceeds the reference temperature.   3. The cogeneration apparatus according to claim 1, wherein the engine control unit sets an engine speed target value for idling while the stop request is pending. 4.

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