JP4964193B2 - Energy system - Google Patents

Description

  The present invention includes an engine that compresses and burns an air-fuel mixture in a combustion chamber and outputs shaft power, exhaust heat recovery means that recovers exhaust heat of the engine and supplies heat to a heat load, The present invention relates to an energy system including power generation means for generating electric power generated by shaft power and generating electric power supplied to an electric load.

  In the energy system as described above, the exhaust heat recovery means stores, for example, a heat exchanger that heats hot water by exchanging heat with exhaust gas from an engine or jacket water, and hot water heated by the heat exchanger. A hot water storage tank is provided, and hot water stored in the hot water storage tank is configured to be supplied to a heat load such as a hot water supply unit or a heating device. The power generation means is, for example, a power generator that generates power using shaft power of the engine, and is configured to supply power generated by the power generator to a power load such as a power device. A so-called cogeneration system or the like is known as an energy system provided with such exhaust heat recovery means and power generation means.

  The required heat amount at the heat load and the required power amount at the power load change with changes in various conditions such as time zone and season. Therefore, in order to improve energy saving, the ratio of the generated heat amount of the exhaust heat recovery means to the generated power amount of the power generation means corresponding to the change in the required heat amount at the heat load and the required power amount at the power load. It is required to change the generated thermoelectric ratio (= generated heat amount / generated power amount). In particular, in cogeneration systems, the required heat amount at the heat load and the required power amount at the power load change every moment, so depending on the changing required heat amount at the heat load and the required power amount at the power load. There is a need to change the generated thermoelectric ratio.

  Therefore, in the conventional energy system, in the spark ignition type engine, the generated thermoelectric ratio is changed by changing the ignition timing of the engine (see, for example, Patent Document 1). The conventional energy system has a characteristic that when the ignition timing is changed to the retard side, the temperature of the exhaust gas increases as the shaft output of the engine decreases. Therefore, by utilizing the characteristics, the amount of heat generated by the exhaust heat recovery means is increased by the temperature rise of the exhaust gas, and the generated thermoelectric ratio is increased. Conversely, by changing the spark ignition timing to the advance side, the amount of heat generated by the exhaust heat recovery means is decreased so that the generated thermoelectric ratio is lowered.

JP 2005-264755 A

In the conventional energy system described above, the ignition timing must be significantly changed in order to change the generated thermoelectric ratio. Therefore, abnormal combustion such as knocking or misfire is likely to occur, causing engine damage or stoppage.
In particular, in order to increase the power generation efficiency, when using an engine in which the excess air ratio of the mixture is set within a lean fuel range and the mixture is lean burned in the combustion chamber, the ignition timing of the engine If is changed to the retarded angle side, misfire is likely to occur, and there is a problem that the amount of unburned hydrocarbons increases.

  The present invention has been made paying attention to such a point, and its purpose is to cope with changes in required heat amount at a thermal load and required power amount at an electric load while suppressing the occurrence of abnormal combustion in the engine. Thus, it exists in the point which provides the energy system which can change the generated thermoelectric ratio.

In order to achieve this object, the characteristic configuration of the energy system according to the present invention includes an engine that compresses and burns an air-fuel mixture in a combustion chamber and outputs shaft power, and recovers exhaust heat of the engine to a heat load. An energy system comprising: exhaust heat recovery means for generating heat to be supplied; and power generation means for generating electric power generated by shaft power of the engine to be supplied to an electric load,
As the combustion mode of the engine, the stoichiometric combustion mode for setting the excess air ratio of the air-fuel mixture combusting in the combustion chamber within the stoichiometric range, and the excess air ratio of the air-fuel mixture combusting in the combustion chamber are set within the stoichiometric range. And a stoichiometric / EGR combustion mode in which a part of the exhaust gas of the engine is recirculated to the combustion chamber by the EGR means, and the amount of heat supplied to the heat load is given priority over the amount of power supplied to the power load. In a situation where the combustion mode is switched to the stoichiometric combustion mode and the amount of power supplied to the power load is prioritized over the amount of heat supplied to the thermal load, the combustion mode is changed to the stoichiometric / EGR combustion. Combustion mode switching means for switching to the mode ,
The stoichiometric EGR combustion mode is a combustion mode in which the EGR rate is increased as the required thermoelectric ratio of the required heat amount at the thermal load to the required electric energy at the electric load decreases .

The excess air ratio is obtained by dividing the air-fuel ratio of the air-fuel mixture by the stoichiometric air-fuel ratio. That is, it can be said that the excess air ratio is higher as the fuel component is smaller in the air-fuel mixture, and the air excess ratio is lower as the fuel component is increased.
In the energy system according to the present invention, the excess air ratio of the air-fuel mixture is set within a stoichiometric range of, for example, about 1.0 in both the stoichiometric combustion mode and the stoichiometric / EGR combustion mode. In the stoichiometric combustion mode, the combustion speed is high and knocking may occur. For example, knocking can be avoided by adjusting the ignition timing. In the stoichiometric / EGR combustion mode, the combustion state may become somewhat unstable due to the recirculation of exhaust gas into the combustion chamber. For example, the combustion state can be stabilized by adjusting the ignition timing. Can be achieved, and a stable combustion state can be maintained.

In the stoichiometric combustion mode, a mixture of air and fuel corresponding to the theoretical air amount is used, so that the heat capacity of the mixture per input heat amount is small, and the temperature of the combustion gas becomes high. As a result, the amount of heat loss in the combustion chamber increases and the power generation efficiency of the power generation means decreases. On the other hand, due to the high temperature of the combustion gas, the exhaust gas of the engine and the jacket water after cooling the engine become high temperature, and the amount of heat generated by the exhaust heat recovery means can be increased. As a result, in the stoichiometric combustion mode, the generated thermoelectric ratio (= generated heat amount / generated power amount), which is the ratio of the generated heat amount of the exhaust heat recovery means to the generated power amount of the power generating means, can be increased.
In the stoichiometric EGR combustion mode, the temperature increase of the combustion gas can be suppressed by recirculation of the exhaust gas. Thereby, the amount of heat loss in the combustion chamber is reduced, and the power generation efficiency of the power generation means can be increased. On the other hand, the amount of heat generated by the exhaust heat recovery means is reduced by suppressing the temperature rise of the combustion gas. As a result, in the stoichiometric / EGR combustion mode, the generated thermoelectric ratio can be lowered.
For example, if the required heat amount at the heat load is larger than the set heat amount, the combustion mode switching means determines that the supply heat amount to the heat load should be given priority over the supply power amount to the power load. Switch to stoichiometric combustion mode. Further, the combustion mode switching means determines that the power supply amount to the power load should be given priority over the heat supply amount to the heat load when the required power amount at the power load is larger than the set power amount. The combustion mode is switched to the stoichiometric / EGR combustion mode. Thereby, the generated thermoelectric ratio can be changed corresponding to the change in the required heat amount at the heat load and the required power amount at the power load.
Since the stoichiometric / EGR combustion mode is a combustion mode in which the EGR rate is increased as the required thermoelectric ratio of the required heat amount at the heat load relative to the required electric energy at the electric load decreases from the stoichiometric combustion mode, the generated thermoelectric ratio Can be appropriately followed by the required thermoelectric ratio.

  Therefore, in the energy system of the present invention, the generated thermoelectric ratio can be changed so as to respond to changes in the required heat amount at the heat load and the required power amount at the power load while suppressing the occurrence of abnormal combustion in the engine.

  In a further characteristic configuration of the energy system according to the present invention, the combustion mode switching means is configured so that the required thermoelectric ratio of the required heat amount at the thermal load relative to the required electric energy at the power load is higher than a set ratio. When the combustion mode is switched to the stoichiometric combustion mode and the required thermoelectric ratio is lower than the set ratio, assuming that the amount of heat supplied to the heat load should be given priority over the amount of power supplied to the power load In addition, the combustion mode is switched to the stoichiometric / EGR combustion mode, assuming that the amount of power supplied to the power load should be given priority over the amount of heat supplied to the heat load.

  According to this characteristic configuration, the combustion mode switching means switches the engine combustion mode between the stoichiometric combustion mode and the stoichiometric / EGR combustion mode depending on whether the required thermoelectric ratio is higher or lower than the set ratio. As a result, the generated thermoelectric ratio can be changed in correspondence with the required thermoelectric ratio, and the change in the required heat amount at the heat load and the required electric energy at the power load can be flexibly and accurately handled.

  A further characteristic configuration of the energy system according to the present invention is that the required heat amount at the heat load and the required power amount at the power load are determined based on the past required heat amount and the past required power amount, A load prediction unit that predicts a required power amount, and the combustion mode switching unit includes a future required heat amount predicted by the load prediction unit as a required heat amount at the thermal load and a required power amount at the power load. And it is in the point comprised so that required electric energy may be used.

  According to this characteristic configuration, the combustion mode switching means changes the engine combustion mode between the stoichiometric combustion mode and the stoichiometric / EGR combustion in accordance with changes in the future required heat amount and the future required electric energy predicted by the load predicting means. You can switch to mode. Therefore, it is possible to accurately change the generated thermoelectric ratio in response to changes in the required heat amount and the required power amount in the future, and it is possible to accurately improve the energy saving.

  According to a further characteristic configuration of the energy system according to the present invention, the exhaust heat recovery means includes a hot water storage tank for storing hot water heated by the exhaust heat of the engine, and the hot water stored in the hot water storage tank is stored in the thermal load. The combustion mode switching means is configured to supply the amount of heat supplied to the heat load rather than the amount of power supplied to the power load when the temperature of the water supplied to the hot water storage tank is lower than a set temperature. When the combustion mode is switched to the stoichiometric combustion mode and the feed water temperature is higher than the set temperature, the supply to the power load is higher than the supply heat amount to the heat load. As a situation where priority should be given to the amount of electric power, the combustion mode is switched to the stoichiometric / EGR combustion mode.

  According to this feature configuration, when the feed water temperature is lower than the set temperature, for example, it can be determined that it is winter, and in winter, the required heat amount at the heat load increases, so the amount of power supplied to the power load Priority should be given to the amount of heat supplied to the heat load. Conversely, when the feed water temperature is higher than the set temperature, for example, it can be determined that it is summer, and in summer, the required heat amount at the heat load is small, so the amount of heat supplied to the power load is greater than the amount of heat supplied to the heat load. Priority should be given to the amount of power supplied. Therefore, the combustion mode switching means appropriately determines whether the priority should be given to the amount of heat supplied to the heat load or the amount of power supplied to the power load by comparing the feed water temperature and the set temperature. The combustion mode can be switched between the stoichiometric combustion mode and the stoichiometric / EGR combustion mode. Therefore, energy saving can be improved accurately.

  A further characteristic configuration of the energy system according to the present invention is such that, in the stoichiometric / EGR combustion mode, an EGR rate of an exhaust gas flow rate recirculated to the combustion chamber with respect to a flow rate of an air-fuel mixture to the combustion chamber becomes 15% or more. It is in the point set to.

  In the stoichiometric EGR combustion mode, if the EGR rate is increased by increasing the flow rate of the exhaust gas recirculated to the combustion chamber by the EGR means, it is possible to more effectively suppress the temperature rise of the combustion gas. Therefore, it is possible to reduce the generated thermoelectric ratio by increasing the EGR rate. According to this characteristic configuration, in the stoichiometric / EGR combustion mode, the generated thermoelectric ratio in the stoichiometric / EGR combustion mode can be made as low as possible by setting the EGR rate to 15% or more. Thereby, the difference between the generated thermoelectric ratio in the stoichiometric combustion mode and the generated thermoelectric ratio in the stoichiometric / EGR combustion mode can be maximized. Therefore, by switching the engine combustion mode between the stoichiometric combustion mode and the stoichiometric / EGR combustion mode, the generated thermoelectric ratio can be changed as much as possible, and the generated thermoelectric ratio can be changed effectively.

  A further characteristic configuration of the energy system according to the present invention is that a three-way catalyst is disposed in the exhaust passage of the engine at a portion through which exhaust gas passes in both the stoichiometric combustion mode and the stoichiometric / EGR combustion mode. It is in the point.

  According to this characteristic configuration, for example, a NOx (nitrogen oxide) is contained by disposing a three-way catalyst in which a noble metal component such as platinum, palladium, or rhodium is supported on an inorganic carrier such as alumina in the exhaust passage. NOx can be reduced and removed by passing the exhaust gas through the three-way catalyst. As a result, the NOx emission amount can be suppressed to a specified amount or less. In addition, the stoichiometric condition is maintained in both the stoichiometric combustion mode and the stoichiometric / EGR combustion mode, so that the oxidizing component and the reducing component contained in the exhaust gas are balanced. Therefore, the three-way catalyst can remove CO (carbon monoxide), HC (hydrocarbon) and the like simultaneously with the reduction and removal of NOx. As a result, NOx, CO, and HC contained in the exhaust gas can be accurately removed.

An embodiment of an energy system according to the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the energy system 100 is configured as a cogeneration system that generates electric power in addition to heat. The energy system 100 includes an engine 1 that compresses and burns an air-fuel mixture M in a combustion chamber 2 to output shaft power, and exhaust heat recovery means that recovers exhaust heat of the engine 1 and generates heat supplied to a heat load 16. 7 and a generator 5 (an example of a power generation means) that generates electric power by the shaft power of the engine 1 and generates electric power to be supplied to the electric power load 21. The generator 5 is configured to supply electric power generated in connection with the commercial power system 20 to a power load 21 such as an electric device.

  The engine 1 sucks a mixture M of fuel G and air A supplied via the fuel supply valve 6 from the intake passage 3 into the combustion chamber 2, compresses the mixture M in the combustion chamber 2, and mixes the mixture M The gas M is ignited in the combustion chamber 2 to be combusted / expanded, and the exhaust gas E generated by the combustion is discharged to the exhaust passage 4 to have the same configuration as that of a normal four-cycle engine.

  An oxygen sensor 18 that detects the oxygen concentration of the exhaust gas E is provided in the exhaust passage 4 through which the exhaust gas E discharged from the combustion chamber 2 flows. The control device 50 that controls the operation of the engine 1 is configured to control the opening of the fuel supply valve 6 while monitoring the oxygen concentration of the exhaust gas E detected by the oxygen sensor 18. Thereby, the excess air ratio of the air-fuel mixture M formed in the intake passage 3 can be arbitrarily set.

  The exhaust heat recovery means 7 recovers exhaust heat of the engine 1 from both the jacket water JW after cooling the engine 1 and the exhaust gas E discharged from the combustion chamber 2, and the hot water HW heated by the recovered exhaust heat Is supplied to a heat load 16 such as a hot water supply unit or a heating device. The exhaust heat recovery means 7 circulates the jacket water JW by operating the circulation pump 10. Thereby, after cooling the engine 1 and raising the temperature, the jacket water JW recovers the heat of the exhaust gas E by passing through the heat transfer pipe 11 provided in the exhaust passage 4 and is further heated. The exhaust heat recovery means 7 includes an exhaust heat recovery heat exchanger 8 that performs heat exchange between the hot jacket water JW after passing through the heat transfer tube 11 and the hot water HW, and hot water heated by the exhaust heat recovery heat exchanger 8. The hot water storage tank 9 for storing the hot water HW stored in the hot water storage tank 9 is supplied to the heat load 16.

  The hot water storage tank 9 forms a high temperature layer in which the high temperature hot water HW stays at the upper part, and so-called temperature stratification for storing the hot water HW so as to form a low temperature layer in which the low temperature hot water HW stays in the lower part of the high temperature layer. It is structured into a mold. By operating the pump 15, the relatively low temperature hot water at the lower end of the hot water storage tank 9 is passed through the exhaust heat recovery heat exchanger 8 and heated to an appropriate target hot water storage temperature (for example, 75 ° C.) or higher. Return to the upper end of the tank 9. Thereby, the hot water storage tank 9 forms temperature stratification and stores the hot water HW. Hot hot water HW taken out from the upper end of the hot water storage tank 9 is supplied to the heat load 16. At the same time, the water supply W corresponding to the consumed hot water HW is replenished to the lower end of the hot water storage tank 9.

The exhaust gas E of the engine 1 passes through the exhaust passage 4 and is discharged. In the exhaust path 4, for example, a three-way catalyst 12 is disposed which is formed by supporting a noble metal component such as platinum, palladium or rhodium on an inorganic carrier such as alumina.
An EGR passage 22 for returning a part E1 of the exhaust gas in the exhaust passage 4 to the intake passage 3, an EGR valve 23 that can be switched between a closed state and an open state, and whose opening degree is adjustable in the open state. And are provided. By opening the EGR valve 23, a part of the exhaust gas E1 in the exhaust passage 4 can be returned to the intake passage 3 in the EGR passage 22, and the exhaust gas E1 can be recirculated to the combustion chamber 2. By adjusting the opening degree of the EGR valve 23 in the open state, the amount of exhaust gas returned to the intake passage 3 through the EGR passage 22 can be adjusted, and the amount of exhaust gas recirculated to the combustion chamber 2 can be adjusted. Thereby, the EGR flow path 22 and the EGR valve 23 are configured to function as the EGR means 24. The EGR means 24 is configured to realize a so-called external EGR in which exhaust gas is recirculated using the EGR flow path 22.

  The control device 50 is configured to function as a load prediction unit 51, an output control unit 52, a combustion mode switching unit 53, and an EGR control unit 54 by executing a predetermined computer program.

The load predicting means 51 predicts the future required heat amount and the required power amount based on the past required heat amount and the past required power amount with respect to the required heat amount at the heat load 16 and the required power amount at the power load 21. It is configured. That is, the load predicting means 51 stores the past heat consumption in the heat load 16 and the past power consumption in the power load 21. For example, the load prediction unit 51 divides one week for each day of the week, and stores power consumption and heat consumption during a set period (for example, 24 hours) of each day of the week. The load predicting means 51 predicts the predicted heat consumption as the future required heat amount in the future setting period (for example, 24 hours) based on the stored past power consumption and past heat consumption, It is configured to predict a consumed power amount as a future required power amount.
Here, the amount of heat consumed in the heat load 16 can be obtained from, for example, the flow rate and temperature of the hot water HW supplied from the hot water storage tank 9 to the heat load 16 and the measurement results. The amount of power consumed in the power load 21 can be obtained by measuring the amount of power supplied from the generator 5 and the commercial power system 20 to the power load 21.

The output control means 52 controls the output of the engine 1 in accordance with the required power amount at the power load 21 in a form such as controlling the opening of a throttle valve (not shown) provided in the engine 1. The main operation control or so-called thermal main operation control for controlling the output of the engine 1 in accordance with the required heat amount at the heat load 16 is executed.
For example, when the output control means 52 performs the main operation control, the generated power amount of the generator 5 becomes equal to the required power amount of the power load 21 or smaller by a certain amount than the required power amount. The output of the engine 1 is controlled according to the required power amount so as to change following the amount.
Further, when the output control means 52 performs the heat main operation control, the amount of heat generated by the exhaust heat recovery means 7 becomes equal to or less than the required heat quantity of the heat load 16, and the required heat quantity. The output of the engine 1 is controlled in accordance with the required heat amount so as to change following the above.

  As the combustion mode of the engine 1, the stoichiometric combustion mode in which the excess air ratio of the air-fuel mixture combusted in the combustion chamber 2 is set within the stoichiometric range, and the excess air ratio of the air-fuel mixture combusted in the combustion chamber 2 is set within the stoichiometric range. In addition, the EGR means 24 has a stoichiometric / EGR combustion mode in which a part of the exhaust gas E of the engine 1 is recirculated to the combustion chamber 2. As shown in FIG. 2, the combustion mode switching unit 53 is configured such that the required thermoelectric ratio (= required heat amount / required power amount) of the required heat amount at the heat load 16 with respect to the required power amount at the power load 21 is higher than the set ratio. Furthermore, the combustion mode is switched to the stoichiometric combustion mode, and the combustion mode is switched to the stoichiometric / EGR combustion mode when the required thermoelectric ratio is lower than the set ratio. At this time, the combustion mode switching unit 53 uses the required heat amount and the required power amount predicted by the load prediction unit 51 for the required heat amount at the heat load 16 and the required power amount at the power load 21.

  In both the stoichiometric combustion mode and the stoichiometric / EGR combustion mode, the control device 50 controls the fuel supply valve 6 so that the oxygen concentration of the exhaust gas E detected by the oxygen sensor 18 becomes a low oxygen concentration that is substantially zero. By adjusting the opening, the excess air ratio of the air-fuel mixture M supplied to the combustion chamber 2 is set within a stoichiometric range of about 1.0. In the stoichiometric combustion mode, the combustion speed is high and knocking may occur. For example, knocking can be avoided by adjusting the ignition timing. Further, in the stoichiometric / EGR combustion mode, the combustion state may become somewhat unstable due to the recirculation of the exhaust gas E1 to the combustion chamber 2. For example, similarly, the combustion state is stabilized by adjusting the ignition timing. The stable combustion state can be maintained.

  In the stoichiometric EGR combustion mode, in addition to setting the excess air ratio of the mixture M supplied to the combustion chamber 2 within a stoichiometric range of about 1.0, the EGR control means 54 opens the EGR valve 23. As a state, a part of the exhaust gas E in the exhaust passage 4 is returned to the intake passage 3 through the EGR passage 22 to recirculate the exhaust gas E to the combustion chamber 2.

In the stoichiometric combustion mode, the heat capacity of the air-fuel mixture per input heat amount is small, and the temperature of the combustion gas becomes high. For this reason, the amount of heat loss in the combustion chamber increases, and the power generation efficiency of the generator 5 decreases. On the other hand, due to the high temperature of the combustion gas, the exhaust gas E of the engine 1 and the jacket water JW after cooling the engine 1 become high temperature, and the amount of heat generated by the exhaust heat recovery means 7 can be increased. As a result, in the stoichiometric combustion mode, the generated thermoelectric ratio (= generated heat amount / generated power amount) that is the ratio of the generated heat amount of the exhaust heat recovery means 7 to the generated power amount of the generator 5 can be increased.
In the stoichiometric EGR combustion mode, the temperature increase of the combustion gas can be suppressed by recirculation of the exhaust gas E to the combustion chamber 2. Thereby, the amount of heat loss in the combustion chamber 2 is reduced, and the power generation efficiency of the generator 5 can be increased. On the other hand, the amount of heat generated by the exhaust heat recovery means 7 is reduced by suppressing the temperature rise of the combustion gas. As a result, in the stoichiometric / EGR combustion mode, the generated thermoelectric ratio can be lowered.

Accordingly, as shown in FIG. 2, the combustion mode switching means 53 switches the combustion mode of the engine 1 between the stoichiometric combustion mode and the stoichiometric / EGR combustion mode depending on whether the required thermoelectric ratio is higher or lower than the set ratio. The generated thermoelectric ratio can be changed corresponding to the required thermoelectric ratio.
In addition, the combustion mode switching unit 53 uses the required heat amount and the required power amount predicted by the load prediction unit 51. Thereby, the generated thermoelectric ratio can be changed according to the required thermoelectric ratio predicted in the future, and the energy saving can be improved accurately.

  Since the three-way catalyst 12 is arranged in the exhaust passage 4, NOx can be reduced and removed by passing exhaust gas containing NOx (nitrogen oxide) through the three-way catalyst. Thereby, the amount of NOx emission can be suppressed to a specified amount or less. Moreover, in both the stoichiometric combustion mode and the stoichiometric / EGR combustion mode, the oxygen concentration of the exhaust gas E is a low oxygen concentration that is substantially zero, so that the oxidizing component and reducing component contained in the exhaust gas E Is in a balanced state. Therefore, the three-way catalyst 12 can perform oxidative removal of CO (carbon monoxide), HC (hydrocarbon), etc. simultaneously with the reduction and removal of NOx. Therefore, NOx, CO, and HC contained in the exhaust gas E can be accurately removed.

  In the stoichiometric EGR combustion mode, the EGR rate of the exhaust gas flow rate recirculated to the combustion chamber 2 with respect to the flow rate of the air-fuel mixture M to the combustion chamber 2 is set to 15% or more. A target opening degree of the EGR valve 23 for setting the EGR rate to 15% or more (for example, 20%) is set in advance. The EGR control means 54 adjusts the opening degree of the EGR valve 23 to the target opening degree, thereby setting the EGR rate to 15% or more (for example, 20%).

In the stoichiometric EGR combustion mode, for example, FIG. 3 shows a change in the generated thermoelectric ratio when the EGR rate is changed from 0% to 20%. Incidentally, the EGR rate of 0% is in the stoichiometric combustion mode.
It can be seen that when the EGR rate is in the range of 0% to 20%, the generated thermoelectric ratio decreases as the EGR rate increases. Thus, by setting the EGR rate to 15% or more in the stoichiometric / EGR combustion mode, the generated thermoelectric ratio in the stoichiometric / EGR combustion mode can be set to 2.125 or less, for example. Thereby, the difference between the generated thermoelectric ratio in the stoichiometric combustion mode and the generated thermoelectric ratio in the stoichiometric / EGR combustion mode can be increased. Therefore, by switching the combustion mode of the engine 1 between the stoichiometric combustion mode and the stoichiometric / EGR combustion mode, the generated thermoelectric ratio can be greatly changed, and the generated thermoelectric ratio can be effectively changed.
Incidentally, if the EGR rate is increased, the combustion in the combustion chamber 2 may become unstable. For example, by increasing the flow amount of the air-fuel mixture or the like in the cylinder of the engine 1 (in the cylinder), the EGR Even when the rate is 15% or more (for example, 20%), combustion in the combustion chamber 2 is stabilized. The upper limit of the EGR rate is, for example, 25%.

[Second Embodiment]
The second embodiment is another embodiment of the EGR means 24 in the first embodiment. Hereinafter, the EGR means 24 in the second embodiment will be described with reference to FIGS. 4 and 5. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  As shown in FIG. 4, the EGR flow path 22 is configured to return a part of the exhaust gas E1 in the exhaust path 4 upstream of the throttle valve 25 that adjusts the intake air amount in the intake path 4. The intake passage 3 is provided with a mixing portion 26 such as a venturi mixer that mixes air and fuel, and a bypass passage 27 that bypasses the throttle valve 25, and a bypass valve 28 is provided in the bypass passage 27.

In the stoichiometric EGR combustion mode, the EGR control means 54 adjusts the opening degree of the EGR valve 23 and the opening degree of the bypass valve 28. As a result, a part of the exhaust gas E1 in the exhaust passage 4 is returned to the intake passage 3, and a part of the air containing the exhaust gas E1 is bypassed through the bypass passage 27 in the throttle valve 25 and the mixing unit 26, and Are mixed and supplied to the combustion chamber 2. Therefore, the EGR flow path 22, the EGR valve 23, the bypass path 27, and the bypass valve 28 are configured to function as the EGR means 24.
The intake air amount to the combustion chamber 2 is adjusted by the throttle valve 25, but in the stoichiometric / EGR combustion mode, the exhaust gas E <b> 1 is returned to the intake passage 3 through the EGR passage 22. Therefore, it is necessary to adjust the opening degree of the throttle valve 25 to the increase side. However, if the opening degree of the throttle valve 25 is adjusted to the excessively open side, the intake air amount may not be controlled, so that a large amount of exhaust gas E1 may not be recirculated to the combustion chamber 2. Therefore, as described above, the opening degree of the throttle valve 25 is adjusted to a large opening degree that makes the intake air amount uncontrollable by opening the bypass valve 28 and sucking the combustion chamber 2 through the bypass path 27. And a large amount of exhaust gas E1 can be recirculated to the combustion chamber 2.

  In the stoichiometric EGR combustion mode, the EGR control means 54 adjusts the opening degree of the EGR valve 23 to the target opening degree. For the adjustment of the opening degree of the bypass valve 28, for example, the target opening degree of the EGR valve 23 is set. The opening degree of the bypass valve 28 can be adjusted so that the target opening degree is set in advance with respect to the degree. For example, if the target opening of the EGR valve 23 is 50%, the target opening of the bypass valve 28 is 20%. Therefore, when the stoichiometric combustion mode is switched to the stoichiometric / EGR combustion mode, the EGR control means 54 increases the opening degree of the EGR valve 23 from 0% to 50% and the opening degree of the bypass valve 28. Increase from 0% to 20%. Finally, the EGR control means 54 adjusts the opening degree of the EGR valve 23 to 50% and the opening degree of the bypass valve 28 to 20%.

  In the second embodiment, instead of the bypass passage 27 and the bypass valve 28 shown in FIG. 4, a second throttle valve 29 is provided upstream of the throttle valve 25 in the intake passage 3 as shown in FIG. You can also. In this case, for example, in the stoichiometric combustion mode, the second throttle valve 29 is adjusted to a half-closed state (opening degree 50%), and in the stoichiometric / EGR combustion mode, the second throttle valve 29 is set to a set opening degree rather than the half-closed state. The opening is adjusted to a larger opening (for example, 70% opening).

[Third Embodiment]
This third embodiment is another embodiment of the combustion mode switching means 53 in the first and second embodiments. Hereinafter, the combustion mode switching means 53 in the third embodiment will be described.
The combustion mode switching means 53 switches the combustion mode to the stoichiometric combustion mode when the feed water temperature supplied to the hot water storage tank 9 is lower than the set temperature, and switches the combustion mode when the feed water temperature is higher than the set temperature. It is configured to switch to the stoichiometric / EGR combustion mode. In order to detect the feed water temperature supplied to the hot water storage tank 9, a feed water temperature detection sensor 13 is provided, and the combustion mode switching means 53 is configured so that the detected temperature of the feed water temperature detection sensor 13 is a set temperature (for example, 15 ° C.). If it is lower than that, for example, it is determined that it is winter, and the combustion mode is switched to the stoichiometric combustion mode. Thereby, although the required thermoelectric ratio becomes high in winter, the high required thermoelectric ratio can be met by switching to the stoichiometric combustion mode and increasing the generated thermoelectric ratio. Further, when the detected temperature of the feed water temperature detection sensor 13 is higher than a set temperature (for example, 15 ° C.), the combustion mode switching means 53 determines that it is summer, for example, and sets the combustion mode to the stoichiometric / EGR combustion mode. Switch to. Thereby, although the required thermoelectric ratio becomes low in summer, the low required thermoelectric ratio can be met by switching to the stoichiometric / EGR combustion mode to reduce the generated thermoelectric ratio.

[Another embodiment]
(1) In the first to third embodiments, the case where so-called external EGR is used as the EGR means for recirculating exhaust gas using the EGR flow path 22 is exemplified. However, the exhaust gas in the combustion chamber 2 is burned as it is. It is also possible to use so-called internal EGR in which a part of the exhaust gas is recirculated by remaining in the chamber 2 or by causing the exhaust gas to flow backward.
For example, by closing the exhaust valve during the exhaust stroke from the bottom dead center to the top dead center, the exhaust gas in the combustion chamber 2 remains in the combustion chamber 2 as it is, and internal EGR can be realized. Further, by providing a throttle valve in the exhaust passage and increasing the exhaust pressure by closing the throttle valve, the exhaust gas in the combustion chamber 2 remains in the combustion chamber as it is, or the exhaust gas in the exhaust passage 4 is burned from the exhaust valve. The internal EGR can be realized by backflowing into the chamber 2.

(2) In the first and second embodiments, the combustion mode switching means 53 switches the combustion mode between the stoichiometric combustion mode and the stoichiometric / EGR combustion mode depending on whether the required thermoelectric ratio is higher or lower than the set ratio. However, for example, when the required heat amount at the heat load 16 is larger than the set heat amount, the combustion mode is switched to the stoichiometric combustion mode, and when the required power amount at the power load 21 is larger than the set power amount, The combustion mode can be switched to the stoichiometric / EGR combustion mode. In this case, when the required heat amount at the heat load 16 is larger than the set heat amount and the required power amount of the power load 21 is larger than the set power amount, and when the required heat amount at the heat load 16 is smaller than the set heat amount and power When the required power amount of the load 21 is smaller than the set power amount, switching to a predetermined one of the stoichiometric combustion mode and the stoichiometric / EGR combustion mode is performed.

  In the third embodiment, the combustion mode switching means 53 switches the combustion mode between the stoichiometric combustion mode and the stoichiometric / EGR combustion mode depending on whether the feed water temperature is higher or lower than the set temperature. For example, the combustion mode switching means 53 has a calendar function for managing the date, etc., and can be switched to the stoichiometric combustion mode in the winter and switched to the stoichiometric / EGR combustion mode in the summer.

(3) In the first to third embodiments, the output control means 52 controls the output of the engine 1 according to the required power amount in the main operation control, or the engine according to the required heat amount in the heat main operation control. However, for example, in the electric main operation control and the heat main operation control, the output of the engine 1 can be a constant output.

  The present invention relates to an engine that compresses and burns an air-fuel mixture in a combustion chamber and outputs shaft power, exhaust heat recovery means that recovers exhaust heat of the engine and supplies heat to a heat load, and engine shaft power Power generation means for generating electric power to generate electric power to be supplied to the electric power load, and responding to changes in the required heat amount at the heat load and the required electric energy at the electric load while suppressing the occurrence of abnormal combustion in the engine Furthermore, it can be applied to various energy systems that can change the generated thermoelectric ratio.

Schematic configuration diagram of energy system Diagram showing switching mode of combustion mode according to required thermoelectric ratio A graph showing the relationship between the generated thermoelectric ratio and the EGR rate The figure which shows the principal part of the energy system in 2nd Embodiment. The figure which shows the principal part of the energy system in 2nd Embodiment.

Explanation of symbols

1 Engine 2 Combustion chamber 4 Exhaust path 5 Power generation means (generator)
7 Waste heat recovery means 12 Three-way catalyst 16 Thermal load 21 Electric power load 51 Load prediction means 53 Combustion mode switching means

Claims (6)

An engine that compresses and burns the air-fuel mixture in the combustion chamber and outputs shaft power;
Exhaust heat recovery means for recovering exhaust heat of the engine and generating heat to be supplied to a heat load;
An energy system including power generation means for generating electric power generated by shaft power of the engine and supplying electric power to an electric load,
As the combustion mode of the engine, the stoichiometric combustion mode for setting the excess air ratio of the air-fuel mixture combusting in the combustion chamber within the stoichiometric range, and the excess air ratio of the air-fuel mixture combusting in the combustion chamber are set within the stoichiometric range. And a stoichiometric / EGR combustion mode in which a part of the exhaust gas of the engine is recirculated to the combustion chamber by the EGR means,
In a situation where the amount of heat supplied to the heat load should be given priority over the amount of power supplied to the power load, the combustion mode is switched to the stoichiometric combustion mode, and the power load is more than the amount of heat supplied to the heat load. the supply amount of power in a situation to be priority, includes a combustion mode switching means for switching the combustion mode to the stoichiometric · EGR combustion mode,
The stoichiometric EGR combustion mode is an energy system in which the EGR rate is increased as the required thermoelectric ratio of the required heat amount at the thermal load to the required electric energy at the power load decreases . Said combustion mode switching means, when the request thermoelectric ratio is higher than the set ratio, the amount of heat supplied to the heat load than the amount of power supplied to the power load as the situation should be prioritized, the combustion mode When switching to the stoichiometric combustion mode and the required thermoelectric ratio is lower than the set ratio, it is assumed that the amount of power supplied to the power load should be given priority over the amount of heat supplied to the heat load. The energy system of claim 1, configured to switch a combustion mode to the stoichiometric EGR combustion mode. A load prediction means for predicting a future required heat amount and a required power amount based on a past required heat amount and a past required power amount for the required heat amount in the heat load and the required power amount in the power load,
The combustion mode switching unit is configured to use the future required heat amount and the required power amount predicted by the load prediction unit as the required heat amount at the thermal load and the required power amount at the power load. The energy system according to claim 2. The exhaust heat recovery means includes a hot water storage tank that stores hot water heated by exhaust heat of the engine, and is configured to supply hot water stored in the hot water storage tank to the thermal load.
The combustion mode switching means is in a situation where priority should be given to the amount of heat supplied to the heat load over the amount of power supplied to the power load when the temperature of the water supplied to the hot water storage tank is lower than a set temperature. When the combustion mode is switched to the stoichiometric combustion mode and the feed water temperature is higher than the set temperature, the amount of power supplied to the power load should be given priority over the amount of heat supplied to the heat load. The energy system according to claim 1, wherein the energy system is configured to switch the combustion mode to the stoichiometric EGR combustion mode.   5. In the stoichiometric EGR combustion mode, the EGR rate of the exhaust gas flow rate recirculated to the combustion chamber with respect to the flow rate of the air-fuel mixture to the combustion chamber is set to be 15% or more. 2. The energy system according to item 1.   6. The three-way catalyst is disposed in the exhaust passage of the engine at a portion through which exhaust gas passes in any of the stoichiometric combustion mode and the stoichiometric / EGR combustion mode. The energy system described in 1.

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