JP2011220234A - Engine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply nitric oxide to a filter while preventing increase in size of an engine system and preventing the engine system from being complicated in the engine system.SOLUTION: The engine system includes nitric oxide concentration increasing sections 5 and 6 that increases the concentration of nitric oxide contained in a combustion gas Y using a burner 4 when a particle attached to at least a filter 3 is ignited.

Description

  The present invention relates to an engine system.

For example, an engine system including a diesel engine (internal combustion engine) includes a filter for removing particulates such as soot contained in exhaust gas from the diesel engine. Since soot or the like adheres to the filter one after another, the amount of fine particles deposited on the filter increases with time.
When the soot accumulation amount in the filter increases, the pressure loss in the filter increases, and when the accumulation amount becomes too large, the filter becomes clogged, making it difficult to smoothly exhaust the exhaust gas.
Further, since the filter melts due to excessively accumulated soot, it is necessary to periodically remove the soot so as not to exceed a certain value.
Therefore, conventionally, a method has been adopted in which the soot adhering to the filter is removed by burning.

  By the way, in patent document 1, it is proposed to implement | achieve soot combustion by low temperature rather than the case where oxygen is supplied as an oxidizing agent by supplying nitrogen dioxide as an oxidizing agent with respect to the filter in which soot accumulated. .

Japanese Patent No. 3012249

However, Patent Document 1 does not disclose a specific configuration of how to supply nitrogen oxide to the filter in the engine system as described above.
Simply adding a device for supplying nitric oxide to a conventional engine system is undesirable because it increases the size and complexity of the engine system, and is generally not included in the engine exhaust. However, there is a problem that sufficient nitric oxide cannot be obtained.
For this reason, the structure which can supply nitric oxide with respect to a filter is calculated | required, suppressing the enlargement and complication of an engine system.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to make it possible to supply nitrogen oxide to a filter while suppressing an increase in size and complexity of the engine system in an engine system.

  The present invention adopts the following configuration as means for solving the above-described problems.

  A first invention includes an internal combustion engine, a filter for collecting and removing particulates contained in exhaust gas discharged from the internal combustion engine, an oxidation catalyst disposed on the upstream side of the filter, and an upstream side of the oxidation catalyst And a burner that supplies combustion gas to the oxidation catalyst, and is included in the combustion gas using the burner when igniting at least the fine particles adhering to the filter. A configuration in which a nitric oxide concentration increasing means for increasing the nitrogen oxide concentration is provided is adopted.

  According to a second invention, in the first invention, the nitrogen oxide concentration increasing means increases the nitrogen oxide concentration contained in the combustion gas only when the fine particles adhering to the filter are ignited. To do.

  According to a third aspect of the present invention, in the first aspect of the invention, the nitrogen oxide concentration increasing means continues to contain the nitrogen oxide in the combustion gas while burning the fine particles adhering to the filter.

According to a fourth invention, in any one of the first to third inventions, the nitric oxide concentration raising means is
A configuration is adopted in which auxiliary air supply means for supplying air to the burner in an auxiliary manner and control means for adjusting the amount of air supplied from the auxiliary air supply means to the burner are employed.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the nitric oxide concentration increasing means is configured to prevent the fine particles adhering to the filter from changing the rotational speed and load of the internal combustion engine over time. A configuration is adopted in which the deposition amount is calculated, and when the calculated deposition amount of the fine particles exceeds a predetermined value stored in advance, the concentration of nitric oxide contained in the combustion gas is increased.

  According to a sixth invention, in any one of the first to fourth inventions, the nitric oxide concentration increasing means deposits the fine particles adhering to the filter from a differential pressure in an upstream region and a downstream region of the filter. A configuration is adopted in which the amount is calculated, and the concentration of nitrogen oxide contained in the combustion gas is increased when the calculated deposition amount of the fine particles exceeds a predetermined value stored in advance.

  According to a seventh invention, in the fifth invention, the nitric oxide concentration increasing means corrects the amount of deposited fine particles based on the differential pressure between the upstream region and the downstream region of the filter. adopt.

In the present invention, when supplying nitrogen oxide to the filter, the nitrogen oxide concentration increasing means increases the concentration of nitrogen oxide contained in the combustion gas using the burner. That is, according to the present invention, nitric oxide supplied to the filter is generated using the burner provided in the conventional engine system.
For this reason, compared with the case where the apparatus for exclusive use for supplying nitric oxide is provided separately, the enlargement and complication of an engine system can be suppressed. In addition, since the amount of nitric oxide supplied to the filter has been dependent on the amount of nitric oxide discharged from the internal combustion engine, the range that can be controlled according to the rotational speed and load of the internal combustion engine has been limited. The amount of nitric oxide can be controlled independently regardless of the state of the internal combustion engine.
Therefore, according to the present invention, in the engine system, it is possible to supply nitrogen oxide to the filter while suppressing an increase in size and complexity of the engine system.

It is a functional block diagram which shows schematic structure of the engine system in 1st Embodiment of this invention. It is a graph which shows the relationship between the ratio of the air of the air-fuel | gaseous mixture in the burner with which the engine system in 1st Embodiment of this invention is provided, and nitric oxide density | concentration. It is a flowchart for demonstrating operation | movement of the engine system in 1st Embodiment of this invention. It is a functional block diagram which shows schematic structure of the engine system in 2nd Embodiment of this invention.

  Hereinafter, an embodiment of an engine system according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

(First embodiment)
FIG. 1 is a functional block diagram showing a schematic configuration of the engine system S1 of the present embodiment.
As shown in this figure, the engine system S1 of this embodiment includes a diesel engine 1 (internal combustion engine), a DOC (Diesel Oxidation Catalyst) 2 (oxidation catalyst), a DPF (Diesel Particulate Filter) 3 (filter), A burner 4, an assist air supply device 5 (auxiliary air supply means), and a control device 6 (control means) are provided.

  The diesel engine 1 is mounted on a vehicle or the like as a power source, and injects fuel into air that has been compressed to a high temperature and high pressure to cause self-ignition and take out the explosive force as rotational power. . The diesel engine 1 discharges exhaust gas X generated by combustion to the outside.

  DOC2 is an oxidation catalyst containing platinum, and is disposed on the downstream side of the diesel engine 1 and on the upstream side of the DPF 3 in the flow direction of the exhaust gas X. And in engine system S1 of this embodiment, DOC2 oxidizes this nitric oxide to nitrogen dioxide, when exhaust gas X supplied contains nitrogen monoxide (nitrogen oxide).

The DPF 3 collects fine particles (Particulate Matter) contained in the exhaust gas X and removes them from the exhaust gas X, and is disposed on the downstream side of the DOC 2 in the flow direction of the exhaust gas X.
As the DPF 3, for example, a monolithic filter made of cordierite or silicon nitride is used. In the engine system S1 of the present embodiment, the DPF 3 is regenerated by an active regeneration method in which fine particles collected by the high-temperature gas supplied from the burner 4 are burned and regenerated.

  The burner 4 generates a high-temperature gas Y (combustion gas) by burning an air-fuel mixture of fuel and oxidant (air or exhaust gas X), and supplies this high-temperature gas Y into the exhaust gas X flow. Is supplied to the DPF 3. The burner 4 is disposed between the diesel engine 1 and the DOC 2 and supplies a high-temperature gas Y into the exhaust gas X flowing from the diesel engine 1 to the DOC 2.

The burner 4 is electrically connected to the control device 6, and the combustion state is controlled by the control device 6. And in engine system S1 of this embodiment, the density | concentration of the nitrogen monoxide (nitrogen oxide) contained in the high temperature gas Y is comprised using the burner 4 so that adjustment is possible.
Specifically, in the engine system S1 of the present embodiment, the burner 4 increases the concentration of nitric oxide contained in the high-temperature gas Y only when igniting the fine particles attached to the DPF 3, and the fine particles attached to the DPF 3 After the ignition, the concentration of nitric oxide contained in the high temperature gas Y is reduced as much as possible.

It is desirable that the nitrogen oxide contained in the exhaust gas X discharged outside through the DPF 3 is as small as possible. On the other hand, in order to efficiently burn the fine particles adhering to the DPF 3, it is desirable that the nitrogen oxide contained in the exhaust gas X supplied to the DPF 3 is somewhat large.
For this reason, in the engine system S1 of this embodiment, by increasing the concentration of nitrogen oxide contained in the exhaust gas X only when the fine particles adhering to the DPF 3 are ignited (that is, when energy is most required), Nitrogen oxide contained in the exhaust gas X discharged to the outside through the DPF 3 is reduced as much as possible, and the fine particles adhering to the DPF 3 are efficiently burned.

  The assist air supply device 5 is for supplying air to the burner 4 in an auxiliary manner, and supplies air to the burner 4 separately from the oxidant required for the air-fuel mixture used in the burner 4. . The assist air supply device 5 is electrically connected to the control device 6 and adjusts the amount of air supplied to the burner 4 under the control of the control device 6.

  As shown in FIG. 2, when the air-fuel mixture is completely burned in the burner 4, the concentration of nitric oxide contained in the exhaust gas tends to increase as the equivalence ratio approaches 1. For this reason, in the engine system S1 of the present embodiment, the supply of air from the assist air supply device 5 to the burner 4 is reduced or stopped when the fine particles adhering to the DPF 3 are ignited.

  The control device 6 is electrically connected to the diesel engine 1, the burner 4 and the assist air supply device 5. The control device 6 mainly controls the operating state of the burner 4 and supplies the air from the assist air supply device 5 to the burner 4. To control.

Here, the amount of particulates adhering to the DPF 3 can be estimated by following the change in the operating condition of the diesel engine 1.
For this reason, in the engine system S1 of the present embodiment, the control device 6 monitors the operating state of the engine system S1, and deposits of fine particles adhering to the DPF 3 from changes in the rotational speed and load of the diesel engine 1 over time. Calculate the amount. And the control apparatus 6 controls the assist air supply apparatus 5 in order to raise the density | concentration of the nitric oxide contained in the high temperature gas Y, when the calculated deposition amount exceeds the regulation value memorize | stored beforehand. As a result, the concentration of nitric oxide contained in the high temperature gas Y temporarily rises, and the fine particles adhering to the DPF 3 are ignited.

In the engine system S1 of the present embodiment, an assist air supply device 5 that supplies air to the burner 4 as an auxiliary, and a control device that adjusts the supply amount of air supplied from the assist air supply device 5 to the burner 4. 6 increases the concentration of nitric oxide contained in the hot gas Y using the burner 4.
That is, in the engine system S1 of the present embodiment, the assist air supply device 5 and the control device 6 constitute the nitrogen oxide concentration increasing means in the present invention.

FIG. 3 is a flowchart for explaining the operation of the engine system S1 of the present embodiment. As shown in this figure, in the engine system S1 of the present embodiment, the control device 6 repeatedly determines whether or not the amount of particulates deposited in the DPF 3 exceeds a specified value (Step 1).
Specifically, the control device 6 acquires a change in the rotational speed of the diesel engine 1 based on a command signal or the like input to the diesel engine 1, and determines the amount of particulates in the DPF 3 from the change in the rotational speed over time. The accumulation amount is calculated, and by comparing the calculated accumulation amount with a predetermined value stored in advance, it is determined whether the accumulation amount of the fine particles in the DPF 3 exceeds the predetermined value.

The control device 6 ignites the fine particles adhering to the DPF 3 by generating the high-temperature gas Y having a high concentration of nitric oxide contained when the amount of the fine particles accumulated in the DPF 3 exceeds a specified value. (Step 2).
Specifically, the control device 6 operates the burner 4, and reduces or stops the supply of air from the assist air supply device 5 to the burner 4, thereby mixing the air-fuel mixture within the burner 4 within a complete combustion range. The hot gas Y is generated in a state where the amount of air contained in the air is increased. As a result, a high-temperature gas Y having a high concentration of nitric oxide is generated.

Note that when the high-temperature gas Y having a high concentration of nitric oxide is mixed with the exhaust gas X and supplied to the DOC 2, the nitric oxide is oxidized into nitrogen dioxide. The exhaust gas X having a high concentration of nitrogen dioxide is supplied to the DPF 3.
When the exhaust gas X having a high concentration of nitrogen dioxide is supplied to the DPF 3, the fine particles are ignited at a lower temperature than when the exhaust gas X having a low nitrogen dioxide concentration is supplied to the DPF 3.

When the fine particles adhering to the DPF 3 are ignited in this way, the control device 6 continues the combustion of the fine particles by supplying the exhaust gas X having the lowest nitrogen dioxide concentration to the DPF 3 (Step 3).
Specifically, the control device 6 sufficiently reduces the concentration of nitric oxide contained in the high-temperature gas Y generated by the burner 4 by sufficiently supplying air from the assist air supply device 5 to the burner 4. Thus, the exhaust gas X having the lowest nitrogen dioxide concentration is supplied to the DPF 3.

  Then, the control device 6 stops the operation of the burner 4 after the combustion time set so that the fine particles are sufficiently burned and removed from the DPF 3, and ends the regeneration process of the DPF 3.

According to the engine system S1 of the present embodiment as described above, when nitrogen oxide is supplied to the DPF 3, the oxidation contained in the high temperature gas Y using the burner 4 conventionally installed for regeneration of the DPF 3 is used. The nitrogen concentration is increased.
Specifically, when the fine particles adhering to the DPF 3 are ignited, when the amount of air supplied from the assist air supply device 5 to the burner 4 is relatively reduced, and the combustion of the fine particles adhering to the DPF 3 is maintained. The amount of air supplied from the assist air supply device 5 to the burner 4 is relatively increased.

According to the engine system S1 of this embodiment, since the concentration of nitrogen oxide contained in the high-temperature gas Y is increased using the burner 4 that is conventionally installed for regeneration of the DPF 3, nitrogen oxide is supplied. As compared with the case where a dedicated device for providing the engine is separately provided, the engine system can be prevented from being enlarged and complicated.
Therefore, according to the engine system S1 of the present embodiment, it is possible to supply nitrogen oxide to the DPF 3 while suppressing an increase in size and complexity of the engine system.

Further, according to the engine system S1 of the present embodiment, the concentration of nitrogen oxide contained in the exhaust gas X is increased only when the fine particles adhering to the DPF 3 are ignited (that is, when the most energy is required).
For this reason, it becomes possible to reduce the nitrogen oxide contained in the exhaust gas X discharged | emitted outside via DPF3 as much as possible.

  However, in the present invention, in order to further improve the combustion efficiency in the DPF 3, the concentration of nitrogen oxide contained in the exhaust gas X discharged from the engine system S1 is allowed even while the fine particles adhering to the DPF 3 are being burned. The concentration of nitric oxide in the exhaust gas X supplied to the DPF 3 may be increased within a range not exceeding the value.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the description of the present embodiment, the description of the same parts as those of the first embodiment is omitted or simplified.
FIG. 4 is a functional block diagram showing a schematic configuration of the engine system S2 of the present embodiment. As shown in this figure, the engine system S2 of this embodiment includes a differential pressure gauge 7.

  The differential pressure gauge 7 is connected to the upstream region and the downstream region of the DPF 3, and outputs the difference between the internal pressure in the upstream region and the downstream region of the DPF 3 as a measurement result. The differential pressure gauge 7 is electrically connected to the control device 6.

The differential pressure between the upstream region and the downstream region of the DPF 3 increases as the amount of particulates accumulated in the DPF 3 increases and the pressure loss in the DPF 3 increases.
Then, in the engine system S1 of the present embodiment, the control device 6 calculates the accumulation amount of the fine particles in the DPF 3 from the output result of the differential pressure gauge 7, and compares the calculated accumulation amount with a predetermined value stored in advance. It is determined whether or not the amount of particulates deposited in the DPF 3 exceeds a specified value.

  Also in the engine system S2 of the present embodiment having such a configuration, as in the engine system S1 of the first embodiment, nitrogen oxide is supplied to the DPF 3 while suppressing an increase in size and complexity of the engine system. It becomes possible to do.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

For example, in the above-described embodiment, the configuration in which the internal combustion engine in the present invention is a diesel engine mounted on a vehicle has been described.
However, the present invention is not limited to this, and any type and usage form of the internal combustion engine may be used.

  Further, the differential pressure gauge 7 shown in the second embodiment is added to the configuration of the first embodiment, and in the first embodiment, the deposition of fine particles is performed based on the output result (that is, the differential pressure) of the differential pressure gauge 7. The amount may be corrected.

  S1, S2 ... Engine system, 1 ... Diesel engine (internal combustion engine), 2 ... DOC (oxidation catalyst), 3 ... DPF (filter), 4 ... Burner, 5 ... Assist air supply device (nitrogen oxide) Concentration increasing means, auxiliary air supply means), 6 ... Control device (nitrogen oxide concentration increasing means, control means), 7 ... Differential pressure gauge, X ... Exhaust gas, Y ... High temperature gas (combustion gas)

Claims (7)

An internal combustion engine, a filter for collecting and removing particulates contained in exhaust gas discharged from the internal combustion engine, an oxidation catalyst disposed upstream of the filter, and disposed upstream of the oxidation catalyst and An engine system comprising a burner for supplying combustion gas to an oxidation catalyst,
An engine system comprising: a nitric oxide concentration increasing means for increasing the concentration of nitric oxide contained in the combustion gas using the burner when at least the fine particles adhering to the filter are ignited.   2. The engine system according to claim 1, wherein the nitrogen oxide concentration increasing means increases the nitrogen oxide concentration contained in the combustion gas only when the fine particles adhering to the filter are ignited.   2. The engine system according to claim 1, wherein the nitrogen oxide concentration increasing means continues to contain the nitrogen oxide in the combustion gas while the fine particles adhering to the filter are burned. The nitric oxide concentration increasing means is
Auxiliary air supply means for supplying air to the burner in an auxiliary manner;
The engine system according to any one of claims 1 to 3, further comprising: a control unit that adjusts a supply amount of air supplied from the auxiliary air supply unit to the burner.   The nitric oxide concentration increasing means calculates a deposition amount of the fine particles adhering to the filter from a change state of a rotational speed and a load of the internal combustion engine with time, and stores the calculated particulate deposition amount in advance. The engine system according to any one of claims 1 to 4, wherein when the value is exceeded, the concentration of nitric oxide contained in the combustion gas is increased.   The nitric oxide concentration increasing means calculates a deposition amount of the particulates adhering to the filter from a differential pressure between an upstream region and a downstream region of the filter, and the calculated deposition amount of the particulates is stored in advance. The engine system according to any one of claims 1 to 4, wherein the concentration of nitric oxide contained in the combustion gas is increased when the temperature exceeds.   6. The engine system according to claim 5, wherein the nitric oxide concentration increasing unit corrects the amount of accumulated fine particles based on a differential pressure between an upstream region and a downstream region of the filter.

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