JP2011163176A - Fuel consumption reducing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover power from exhaust gas with increased temperature after passing through an NO<SB>X</SB>reduction catalyst by a power turbine to improve fuel consumption even in an engine with a high pressure loop. <P>SOLUTION: A fuel consumption reducing system is applied to the diesel engine 1 (the engine) having a turbocharger 2, an NO<SB>X</SB>storage reduction catalyst 12 (the NO<SB>X</SB>reduction catalyst), a fuel adding device 14 (a fuel adding means) adding fuel as a reducing agent necessary for emission control of NO<SB>X</SB>, and the high pressure loop 15 for extracting part of exhaust gas 9 from an exhaust manifold 10 and recirculating the part of the exhaust gas 9 to a vicinity of an inlet port of an intake manifold 7. The system includes a power turbine 18 recovering the power from the exhaust gas 9 after passing through the NO<SB>X</SB>storage reduction catalyst 12 and transmitting the power to a side of the diesel engine 1 as auxiliary power, and a low pressure loop 19 extracting part of the exhausting gas 9 from an exhaust pipe 11 in a downstream side of the power turbine 18 and recirculating the part of the exhaust gas 9 to a vicinity of an inlet port of a compressor 2a of the turbocharger 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel consumption reduction system.

Conventionally, exhaust purification is carried out with an exhaust purification catalyst installed in the middle of the exhaust pipe. As this type of exhaust purification catalyst, NOx in exhaust gas is oxidized when the exhaust air-fuel ratio is lean. Thus, a NOx occlusion reduction catalyst having the property of temporarily storing in the form of nitrate and decomposing and releasing NOx through the intervention of unburned HC, CO, etc. when the O ₂ concentration in the exhaust gas decreases is reduced and purified. Are known.

In the NOx occlusion reduction catalyst, when the occlusion amount of NOx increases and reaches the saturation amount, no more NOx can be occluded, and therefore, O _{2 of} the exhaust gas flowing into the NOx occlusion reduction catalyst periodically. It is necessary to decompose and release NOx by reducing the concentration.

For example, when used in a gasoline engine, by reducing the operating air-fuel ratio of the gasoline engine (operating at a rich air-fuel ratio), the O ₂ concentration in the exhaust gas is reduced and the unburned HC in the exhaust gas is reduced. It is possible to promote the decomposition and release of NOx by increasing reducing components such as CO and CO. However, when the NOx storage reduction catalyst is used as an exhaust gas purification device for a diesel engine, the diesel engine should be operated at a rich air-fuel ratio. Is difficult.

For this reason, when using the NOx storage reduction catalyst as an exhaust purification device for a diesel engine, fuel is added to the exhaust gas upstream of the NOx storage reduction catalyst, and this added fuel is used as a reducing agent on the NOx storage reduction catalyst. the O ₂ concentration in the exhaust gas by reacting with O ₂ is required to be reduced.

  In addition, the following patent documents 1-3 etc. are mention | raise | lifted as prior art document information relevant to this invention.

JP 2007-126995 A JP 2008-208720 A Japanese Patent No. 4337809

  However, in a diesel engine equipped with such a NOx storage reduction catalyst, reaction heat is generated when the added fuel undergoes an oxidation reaction on the NOx storage reduction catalyst, and the exhaust gas rises in temperature due to the reaction heat and expands. However, until now, the exhaust gas that has passed through the NOx storage reduction catalyst has been exhausted as it is outside the vehicle while there is room for power recovery.

  Therefore, the present inventors provide a power turbine downstream of the NOx storage reduction catalyst, recover power from the exhaust gas whose temperature has risen via the NOx storage reduction catalyst, and transmit the recovered power as auxiliary power to the engine side to reduce fuel consumption. Many of the diesel engines have a high-pressure loop that draws a part of the exhaust gas from the exhaust manifold and recirculates it near the inlet of the intake manifold. Even if it was placed downstream of the storage reduction catalyst, fuel efficiency was not improved.

  This is because in a diesel engine having a high-pressure loop, a part of the exhaust gas is recirculated through the high-pressure loop, so that the flow rate of the exhaust gas passing through the power turbine decreases and the output decreases. Moreover, in order to recirculate the required amount of exhaust gas through the high-pressure loop, the nozzle vane opening of the turbocharger turbine must be narrowed to increase the pressure of the exhaust manifold, which increases the pumping loss. Because there was.

  In the first place, the addition of a power turbine inevitably increases pumping loss due to an increase in exhaust pressure. Therefore, fuel efficiency cannot be improved unless the output of the power turbine exceeds the deterioration of pumping loss. However, as described above, under the condition that the output of the power turbine decreases due to exhaust gas recirculation through the high-pressure loop and the pumping loss further increases due to the pressure increase of the exhaust manifold, the power turbine The deterioration of pumping loss tends to exceed the output, making it difficult to improve fuel efficiency.

  It should be noted that in order to recirculate the required amount of exhaust gas through the high pressure loop, the reason why the nozzle vane opening of the turbocharger turbine must be narrowed down is as follows. The vicinity of the inlet is in a high pressure condition after being supercharged by a turbocharger compressor, and in order to recirculate the exhaust gas without difficulty, the nozzle vane opening of the turbine is narrowed down to reduce the pressure of the exhaust manifold. Therefore, a sufficient differential pressure with respect to the intake side where the exhaust gas is recirculated must be secured.

  The present invention has been made in view of the above circumstances, and even in an engine having a high-pressure loop, the power turbine efficiently recovers power from exhaust gas whose temperature has risen through a NOx reduction catalyst such as a NOx storage reduction catalyst. The purpose is to improve fuel economy.

  The present invention relates to a turbocharger that recovers power from exhaust gas delivered from an exhaust manifold and supercharges intake air, and NOx installed in the middle of an exhaust pipe so as to purify NOx in exhaust gas that has passed through the turbocharger. A reduction catalyst, fuel addition means for adding fuel upstream of the NOx reduction catalyst as a reducing agent necessary for NOx purification treatment, a part of the exhaust gas is extracted from the exhaust manifold and recirculated near the inlet of the intake manifold A fuel consumption reduction system for application to an engine having a high-pressure loop that recovers power from exhaust gas that is provided downstream of the NOx reduction catalyst and passes through the NOx reduction catalyst and transmits the recovered power to the engine side as auxiliary power. A portion of the exhaust gas is extracted from a power turbine and an exhaust pipe downstream from the power turbine to It is characterized in that a low pressure loop recycled to the inlet near the suppressor.

  Thus, in this way, the exhaust gas rises in temperature due to the reaction heat generated by the reaction using the added fuel from the fuel addition means as the reducing agent on the NOx reduction catalyst, and is directly introduced into the power turbine. Therefore, the surplus energy of the exhaust gas is efficiently recovered by the power turbine and effectively used as auxiliary power to the engine side.

Further, a part of the exhaust gas passing through the power turbine is recirculated through the low-pressure loop to the vicinity of the inlet of the turbocharger compressor. This exhaust gas uses the added fuel in the NOx reduction catalyst as a reducing agent. Since the O ₂ concentration is reduced due to the reaction, the exhaust gas recirculated through the low-pressure loop contributes to the reduction of the O ₂ concentration in the intake manifold.

As a result, the amount of exhaust gas recirculation required to reduce the O ₂ concentration of the intake manifold to the predetermined value is smaller than before, and the exhaust gas flow rate through the power turbine is secured higher than before. As a result, the output power of the power turbine is increased, and even if the nozzle vane opening of the turbocharger turbine is opened and the pressure of the exhaust manifold is lowered from the conventional level, the recirculation amount of exhaust gas required on the high-pressure loop side (conventional) Therefore, the pumping loss can be greatly reduced by the pressure drop of the exhaust manifold.

  Furthermore, in the present invention, a particulate filter may be interposed between the power turbine and the exhaust extraction portion of the low-pressure loop, and in this way, soot is collected through the particulate filter. Relatively clean exhaust gas can be recirculated through the low pressure loop.

  In the present invention, a particulate filter may be interposed between the power turbine and the NOx reduction catalyst. In this way, relatively clean exhaust gas is recirculated through the low pressure loop. In addition, the heat generated when the soot collected in the particulate filter burns can be recovered by the power turbine, and the soot is collected through the particulate filter. A relatively clean exhaust gas can be guided to the power turbine.

In the present invention, when the exhaust air-fuel ratio is lean, NOx in the exhaust gas is oxidized and temporarily stored in the form of nitrate, and when the O ₂ concentration in the exhaust gas decreases, the NOx is interposed by HC. NOx occlusion reduction catalyst with the property of decomposing and releasing to reduce and purify may be used as a NOx reduction catalyst, and selective reduction type catalyst with the property of selectively reacting NOx with a reducing agent even in the presence of oxygen reduces NOx. It may be a catalyst.

  According to the fuel consumption reduction system of the present invention described above, various excellent effects as described below can be obtained.

  (I) It is possible to increase the power turbine output by increasing the flow rate of the exhaust gas passing through the power turbine, and to reduce the pumping loss of the engine significantly by lowering the pressure of the exhaust manifold than before. Therefore, even in an engine equipped with a high-pressure loop, the fuel efficiency of the engine can be greatly improved by efficiently recovering power from the exhaust gas whose temperature has been increased through the NOx reduction catalyst by the power turbine.

  (II) If a configuration in which a particulate filter is interposed between the power turbine and the exhaust extraction point of the low-pressure loop is adopted, a relatively clean exhaust gas that has collected soot through the particulate filter is passed through the low-pressure loop. Therefore, it is possible to prevent contamination by soot such as a compressor or an intercooler of the turbocharger.

  (III) When a configuration in which a particulate filter is interposed between the power turbine and the NOx reduction catalyst is adopted, in addition to the effect of (II), when the soot collected in the particulate filter burns Heat can be recovered by the power turbine to further improve the fuel efficiency of the engine, and a relatively clean exhaust gas in which soot is collected through the particulate filter is guided to the power turbine. Thus, contamination of the power turbine by soot can be prevented.

It is the schematic which shows an example of the form which implements this invention. It is the schematic which shows another form example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a diesel engine equipped with a variable nozzle type turbocharger 2 (variable geometry turbocharger), which is introduced from an air cleaner 3. The intake air 4 is sent to the compressor 2 a of the turbocharger 2 through the intake pipe 5, and the intake air 4 pressurized by the compressor 2 a is sent to the intercooler 6 to be cooled, and further from the intercooler 6. The intake air 4 is guided to the intake manifold 7 and is distributed to each cylinder 8 of the diesel engine 1 (the case of in-line 6 cylinders is illustrated in FIG. 1).

Further, the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 10, and the exhaust gas 9 that has driven the turbine 2b passes through the exhaust pipe 11. In the middle of the exhaust pipe 11, NOx in the exhaust gas 9 is oxidized when the exhaust air-fuel ratio is lean, and is temporarily occluded in the form of nitrate and in the exhaust gas 9. A NOx occlusion reduction catalyst 12 (NOx reduction catalyst) having the property of decomposing and releasing NOx by the intervention of HC to reduce and purify it when the O ₂ concentration of NO is reduced is held in the catalyst case 13 and equipped.

A fuel addition device 14 (fuel addition means) for adding fuel as a reducing agent necessary for NOx purification treatment is provided in the exhaust pipe 11 on the inlet side of the catalyst case 13. By periodically adding fuel, the concentration of O ₂ in the exhaust gas 9 can be reduced to promote the decomposition and release of NOx, and the NOx that has been decomposed and released can be reduced and purified on the NOx storage reduction catalyst 12 through the intervention of HC. It is like that.

  In addition, one end of the exhaust manifold 10 in the arrangement direction of the cylinders 8 and the intake pipe 5 in the vicinity of the inlet of the intake manifold 7 are connected by a high-pressure loop 15, and the exhaust gas 9 extracted from the exhaust manifold 10 is connected. A part is recirculated near the inlet of the intake manifold 7 through a water-cooled EGR cooler 16 and an EGR valve 17, and each cylinder 8 is recirculated from the exhaust system to the intake system. The generation of NOx can be reduced by suppressing the combustion of the fuel and lowering the combustion temperature.

  In the diesel engine 1 configured in this way, power is recovered from the exhaust gas 9 that has passed through the NOx storage reduction catalyst 12 downstream of the NOx storage reduction catalyst 12 and used as auxiliary power to the diesel engine 1 side. A power turbine 18 for transmission is provided, and the power recovered by the power turbine 18 is transmitted to the crankshaft of the diesel engine 1 via a gear train, a fluid coupling, etc. (not shown). When the diesel engine 1 is provided with an electric assist mechanism, the generator is driven by the power recovered by the power turbine 18 to generate electric power, and the generated electric power is transmitted to the diesel engine via the electric assist mechanism. You may make it utilize as 1 auxiliary power.

  Further, the exhaust pipe 11 downstream from the power turbine 18 and the intake pipe 5 near the inlet of the compressor 2 a of the turbocharger 2 are connected by a low-pressure loop 19, and the exhaust pipe downstream from the power turbine 18. A part of the exhaust gas 9 extracted from 11 is recirculated to the vicinity of the inlet of the compressor 2 a of the turbocharger 2 through the EGR valve 20.

  In the example shown here, the particulate filter 21 is interposed between the power turbine 18 and the exhaust extraction portion of the low-pressure loop 19 so as to be held by the filter case 22, and the particulate filter 21. The relatively clean exhaust gas 9 from which the soot has been collected is recirculated through the low-pressure loop 19.

  Thus, in this way, the exhaust gas 9 rises in temperature due to the reaction heat generated by the reaction using the added fuel from the fuel addition device 14 as a reducing agent on the NOx occlusion reduction catalyst 12 and expands as it is. Since the power is recovered by being introduced into the turbine 18, the surplus energy of the exhaust gas 9 is efficiently recovered by the power turbine 18 and effectively used as auxiliary power to the diesel engine 1 side.

Further, a part of the exhaust gas 9 passing through the power turbine 18 is recirculated to the vicinity of the inlet of the compressor 2 a of the turbocharger 2 through the low pressure loop 19, and this exhaust gas 9 is supplied to the NOx storage reduction catalyst 12. Since the O ₂ concentration is reduced due to the reaction using the added fuel at the reductant at the exhaust gas 9, the exhaust gas 9 recirculated through the low-pressure loop 19 contributes to the reduction of the O ₂ concentration in the intake manifold 7. Become.

As a result, the recirculation amount of the exhaust gas 9 on the high-pressure loop 15 side required for reducing the O ₂ concentration of the intake manifold 7 to a predetermined value is smaller than before, and the flow rate of the exhaust gas 9 passing through the power turbine 18 is reduced. More power is ensured than before, and the output of the power turbine 18 is increased. Moreover, even if the nozzle vane opening of the turbine of the turbocharger 2 is opened and the pressure of the exhaust manifold 10 is lowered than before, it is necessary on the high-pressure loop 15 side. Therefore, a sufficient amount of exhaust gas 9 can be recirculated (a recirculation amount that can be reduced as compared with the prior art), and the pumping loss can be greatly reduced by the pressure drop of the exhaust manifold 10.

  Therefore, according to the above embodiment, the flow rate of the exhaust gas 9 passing through the power turbine 18 can be increased as compared with the prior art, and the output of the power turbine 18 can be increased, and the pressure of the exhaust manifold 10 can be lowered as compared with the conventional diesel engine. Since the pumping loss of the engine 1 can be greatly reduced, even the diesel engine 1 having the high-pressure loop 15 can be efficiently powered by the power turbine 18 from the exhaust gas 9 whose temperature has risen via the NOx storage reduction catalyst 12. The fuel consumption of the diesel engine 1 can be greatly improved by collecting the fuel.

  Further, in particular, in the present embodiment, since the particulate filter 21 is interposed between the power turbine 18 and the exhaust extraction portion of the low pressure loop 19, the comparison in which the soot is collected through the particulate filter 21. The clean exhaust gas 9 can be recirculated through the low-pressure loop 19, and contamination by soot such as the compressor 2a and the intercooler 6 of the turbocharger 2 can be prevented.

  FIG. 2 shows another embodiment of the present invention. The power turbine 18 and the particulate filter 21 in FIG. 1 are reversely arranged, and the particulate filter is interposed between the power turbine 18 and the NOx storage reduction catalyst 12. 21 is interposed.

  In this way, the relatively clean exhaust gas 9 can be recirculated through the low-pressure loop 19 as in the case of the embodiment shown in FIG. 1, and the compressor 2a and the intercooler 6 of the turbocharger 2 can be recirculated. In addition to being able to prevent pollution caused by soot, etc., the heat generated by burning the soot collected in the particulate filter 21 can be recovered by the power turbine 18 to further improve the fuel efficiency of the diesel engine 1. In addition, the relatively clean exhaust gas 9 in which soot is collected through the particulate filter 21 can be guided to the power turbine 18, and contamination of the power turbine 18 by soot can be prevented. .

Further, in the embodiment shown in FIGS. 1 and 2 described above, the case where the NOx reduction catalyst is the NOx occlusion reduction catalyst 12 is described. However, the property of selectively reacting NOx with a reducing agent even in the presence of oxygen. Of course, the selective reduction catalyst provided may be adopted as the NOx reduction catalyst. Even when this type of selective reduction catalyst is adopted as the NOx reduction catalyst, the added fuel from the fuel addition device 14 is reduced. Due to the reaction of the agent, the temperature of the exhaust gas 9 is increased by reaction heat and the O ₂ concentration of the exhaust gas 9 is decreased. Therefore, the same operational effects as those of the embodiment shown in FIGS. 1 and 2 can be obtained. .

  The fuel consumption reduction system of the present invention is not limited to the above-described embodiment. In the previous embodiment, the case where fuel addition means is provided in the exhaust pipe upstream from the NOx reduction catalyst is exemplified. However, a fuel injection device responsible for fuel injection into each cylinder of the engine is adopted as the fuel addition means, and at the non-ignition timing later than the compression top dead center following the main injection of fuel performed near the compression top dead center. The fuel may be added to the exhaust gas by performing post-injection, or the fuel may be added to the exhaust gas by delaying the timing of the main injection into the cylinder. Of course, various modifications can be made without departing from the scope of the present invention.

1 Diesel engine (engine)
2 Turbocharger 2a Compressor 7 Intake manifold 9 Exhaust gas 10 Exhaust manifold 11 Exhaust pipe 12 NOx storage reduction catalyst (NOx reduction catalyst)
14 Fuel addition device (fuel addition means)
15 High-pressure loop 18 Power turbine 19 Low-pressure loop 21 Particulate filter

Claims (5)

  A turbocharger that recovers power from the exhaust gas sent from the exhaust manifold and supercharges intake air, and a NOx reduction catalyst that is installed in the middle of the exhaust pipe so as to purify NOx in the exhaust gas that has passed through the turbocharger, A fuel adding means for adding fuel upstream of the NOx reduction catalyst as a reducing agent necessary for NOx purification treatment; a high-pressure loop for extracting a part of the exhaust gas from the exhaust manifold and recirculating it near the inlet of the intake manifold; A power turbine that is provided downstream of the NOx reduction catalyst and recovers power from the exhaust gas that has passed through the NOx reduction catalyst and transmits it to the engine side as auxiliary power, A part of the exhaust gas is extracted from the exhaust pipe downstream of the power turbine, and the compressor of the turbocharger Fuel consumption reduction system characterized in that a low pressure loop recycling around the mouth.   2. The fuel consumption reduction system according to claim 1, wherein a particulate filter is interposed between the power turbine and an exhaust extraction portion of the low pressure loop.   The fuel consumption reduction system according to claim 1, wherein a particulate filter is interposed between the power turbine and the NOx reduction catalyst. When the exhaust air-fuel ratio is lean, NOx in the exhaust gas is oxidized and temporarily stored in the form of nitrate, and when the O ₂ concentration in the exhaust gas decreases, the NOx is decomposed and released by HC to reduce and purify. The fuel consumption reduction system according to claim 1, 2 or 3, wherein the NOx storage reduction catalyst having properties is a NOx reduction catalyst.   4. The fuel consumption reduction system according to claim 1, wherein the selective reduction type catalyst having a property of selectively reacting NOx with a reducing agent even in the presence of oxygen is used as a NOx reduction catalyst.

Images