CN103790696A

CN103790696A - Method and apparatus for preventing formation of condensate upstream of compressor of turbocharged automotive internal combustion engine

Info

Publication number: CN103790696A
Application number: CN201310524405.0A
Authority: CN
Inventors: C·W·维吉尔德; A·库斯克; D·罗杰
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2012-10-30
Filing date: 2013-10-30
Publication date: 2014-05-14
Also published as: DE102012219812A1; DE102012219812B4

Abstract

The present invention relates to a method and apparatus for preventing formation of a condensate upstream of a compressor (8) of a turbocharged automotive internal combustion engine with low-pressure exhaust recirculation from an exhaust gas aftertreatment unit (22) to an air intake channel (5) of the compressor (8) via an exhaust recirculation cooler. According to the invention, the compressor (8) receives an air mixture from the air intake channel (5). The air mixture is composed of air at the ambient temperature and air heated by waste heat of the internal combustion engine with a mixing ratio substantially variable between 0% to 100%. The mixing ratio of the air at the ambient temperature and the heated air is adjusted such that the temperature of the air mixture is regulated as far as possible to a value lying in a predetermined temperature range.

Description

Method and device for preventing the formation of condensate upstream of the compressor of a turbocharged motor vehicle internal combustion engine

Technical Field

The present invention relates to a method and an apparatus for preventing the formation of condensate upstream of a compressor of a turbocharged motor vehicle internal combustion engine having low-pressure exhaust gas recirculation, wherein low-pressure exhaust gas is recirculated from an exhaust gas aftertreatment unit to an intake channel of the compressor via an exhaust gas recirculation cooler, as described in the preambles of the independent claims.

Background

Modern diesel engines and Otto-cycle (Otto-cycle) engines typically have Exhaust Gas Recirculation (EGR), in which exhaust gases are led back to the intake manifold in order to, inter alia, reduce temperature peaks in the cylinders (due to the setting of low oxygen concentrations in the mixture). In this way, it is possible in turn to achieve a reduction or limitation of the emissions of nitrogen oxides, which is necessary in order to comply with the limits specified, for example, in the exhaust standard EURO 6.

In the case of internal combustion engines with exhaust-gas turbochargers, a distinction is made between low-pressure exhaust-gas recirculation and high-pressure exhaust-gas recirculation, wherein both may also be provided. In the case of low-pressure exhaust gas recirculation, an exhaust gas mass flow branched off downstream from the exhaust gas aftertreatment unit is provided into the fresh air at a location upstream of the compressor of the turbocharger. In the case of high-pressure exhaust gas recirculation, the exhaust gas mass flow branched off from the exhaust manifold is provided into the fresh air at a location downstream of the compressor of the turbocharger. One of the two exhaust gas recirculation cycles is selected based on the current operating conditions. Cooler low-pressure exhaust gas recirculation with less particulate matter is generally preferred here, in particular because the inlet air is not heated by the very hot exhaust gas, which reduces the volumetric efficiency in the case of high-pressure exhaust gas recirculation, and because the exhaust gas mass flow upstream of the turbine of the turbocharger is not reduced as in the case of high-pressure exhaust gas recirculation.

However, low pressure exhaust gas recirculation has a problem in that, depending on the temperature and humidity of the ambient air being drawn in, water droplets or ice particles may condense out of the intake air upstream of the compressor, where they may damage the blades of the compressor wheel rotating at high speed. This risk exists in particular in the case of an internal combustion engine of a motor vehicle operating at ambient temperatures below freezing, wherein in this case the ambient temperature is understood to mean the temperature of the air surrounding the motor vehicle.

DE102010032693a1 discloses a method for preventing the formation of condensate upstream of the compressor of a turbocharged motor vehicle internal combustion engine having a low-pressure exhaust gas recirculation from an exhaust gas aftertreatment unit via an exhaust gas recirculation cooler to the intake passage of the compressor, in which method a portion of the low-pressure exhaust gas recirculation mass flow is led through a bypass which bypasses the exhaust gas recirculation cooler in order to increase the mixture temperature and thus eliminate the tendency of the formation of condensate upstream of the compressor. However, since the amount of exhaust gas that can be recirculated is limited, if the ambient temperature is very low, the method will reach its limit and the overall efficiency of the internal combustion engine will suffer.

Disclosure of Invention

The invention is based on the object of proposing a method which can be used to prevent condensate formation in the case of low-pressure exhaust gas recirculation over a wide range of operating and ambient conditions, which can be implemented with little effort and which does not impair the overall efficiency of the internal combustion engine as far as possible.

According to the invention, the object is achieved by a method and a device as set forth in the independent claims. The dependent claims present advantageous developments of the invention.

According to the invention, the compressor receives from the intake channel (in addition to the recirculated exhaust gas) an air mixture consisting of air at ambient temperature and air which has been heated by the waste heat of the internal combustion engine in proportions which can vary substantially between 0% and 100%, the mixing ratio between air at ambient temperature and heated air being adjusted such that the temperature of the air mixture is adjusted to a value lying in a predetermined temperature range if possible (i.e. if the currently available waste heat and the current fresh air demand of the internal combustion engine and the current ambient temperature allow this). Condensate is not readily formed in the relatively hot air mixture, and the risk of damage to the compressor blades by ice particles or water droplets is reduced or even eliminated. This makes it possible to comply with stricter exhaust gas standards in the future, which require recirculation of exhaust gas under certain operating conditions, such as during periods when the nitrogen oxide storage catalytic converter often requires desulfation, even at sub-freezing temperatures. The invention makes it possible to replace the disadvantageous side effects of high-pressure exhaust gas recirculation with the advantage of low-pressure exhaust gas recirculation for this purpose.

According to US2007/0062490a1, it is sufficiently known that a portion of the intake air of an internal combustion engine is heated by its waste heat, in particular by a coolant heat exchanger and/or an exhaust gas heat exchanger. However, this achieves the object of providing a hot air store which provides the energy required for the auto-ignition of the air-fuel mixture in the event of a rapid transition from the spark-ignition operating mode to the homogeneous compression-ignition operating mode.

In a preferred embodiment of the invention, the value to which the temperature is adjusted is determined on the basis of the current temperature and/or humidity of the ambient air.

In a preferred embodiment of the invention, the compressor receives from the inlet channel substantially only air at ambient temperature when the ambient temperature is above the upper temperature limit, receives as much heated air as is available (and, if required, additional air at ambient temperature) at ambient temperatures below the lower temperature limit, and typically receives a mixture of air at ambient temperature and heated air at ambient temperatures between the upper and lower temperature limit.

The lower temperature value is preferably selected such that condensate formation upstream of the compressor is reliably prevented or at least to an extent that there is no risk of damage of the compressor blades by ice particles or water droplets. This is ensured at an inlet temperature of at least 15 ℃. However, the lower temperature value may be lower, for example about 10 ℃, especially if the humidity of the current air is additionally taken into account. If the ambient temperature is very low and not enough waste heat is available, it is furthermore possible to use the methods known from the prior art for preventing condensate formation, since a portion of the low-pressure exhaust gas recirculation mass flow is led through a bypass which bypasses the exhaust gas recirculation cooler. The upper temperature value is preferably selected such that the volumetric efficiency is not unnecessarily impaired. A suitable value is for example 20 ℃.

That is, the mixing ratio between air at ambient temperature and heated air is set such that the temperature of the air mixture is at least about 10 ℃ or 15 ℃, if possible (i.e. if the internal combustion engine outputs sufficient waste heat), and/or such that the temperature of the air mixture is at most about 20 ℃, if possible (i.e. if the ambient temperature is not higher).

In a preferred embodiment, a mixture of ambient temperature air and heated air is produced, after which the resulting air mixture is mixed with the low pressure exhaust recirculation gas and flows through the intake passage into the compressor. A particularly homogeneous mixture and a uniform mixture temperature can be achieved if the two air flows are mixed with one another upstream of the intake air filter.

In a preferred embodiment, the heated air is obtained from exhaust waste heat as it is drawn in from a cavity formed between the outer surface of the exhaust gas aftertreatment unit and the housing surrounding it, and which is fluidly connected to the ambient air through one or more openings. The cavity annularly around the exhaust aftertreatment unit may already be provided in the vehicle, for example in the form of a shield under which heat is accumulated, and may easily be modified to form an efficient exhaust heat exchanger.

Alternatively, the heated air may be derived from waste heat from the engine coolant as it is drawn from a heat exchanger that is fluidly connected to ambient air and in thermal contact with the engine coolant.

In a preferred embodiment, the mixing ratio between air at ambient temperature and heated air is adjusted by means of a flap. The position of the flap can be adjusted in a very simple manner by means of a bimetallic element, the temperature of which is determined by or significantly influenced by the temperature of the air mixture, since the bimetallic element is simply exposed to the air mixture. Alternatively, the position of the flap can be adjusted by means of an actuator which is activated by means of a signal which is based on a temperature measurement, in particular a measurement of a temperature sensor based on the temperature of the air mixture.

Drawings

Exemplary embodiments will be described below with reference to the accompanying drawings. In the drawings:

FIG. 1 shows a diagram of an internal combustion engine having a turbocharger, high and low pressure exhaust gas recirculation, and heating intake air by exhaust waste heat;

FIG. 2 shows an enlarged view of the intake portion and low pressure exhaust gas recirculation of FIG. 1;

FIG. 3 shows an enlarged view of a variation of the intake portion of FIG. 1; and

fig. 4 shows a diagram corresponding to fig. 1, but with the intake air heated by the coolant waste heat.

Detailed Description

Fig. 1 shows an internal combustion engine 2 comprising an air inlet system and an air outlet system, which in this example may be a diesel engine or a gasoline engine.

The intake system starts from an intake pipe 4 receiving ambient air, then through an air filter 6, through a compressor 8 of an exhaust gas turbocharger consisting of the compressor 8 and a turbine 10, and through an inlet temperature control module 12 to an intake manifold 18 of the internal combustion engine 2, the inlet temperature control module 12 comprising a charge air cooler 14 and an electric heater unit 16. The air cleaner 6 and the compressor 8 are connected to each other through the intake passage 5. The electric heater unit 16 enables the pressurized air to be heated during a cold start.

The exhaust system starts from the exhaust manifold 20 of the internal combustion engine 2, then through the turbine 10 of the exhaust turbocharger, through the exhaust aftertreatment unit 22, which exhaust aftertreatment unit 22 comprises a diesel oxidation catalytic converter 24 and a diesel particulate filter 26, and through a muffler 28 to the exhaust outlet pipe 30.

A high pressure exhaust gas recirculation line leads from the exhaust manifold 20 via a metering valve 32 and a high pressure exhaust gas recirculation cooler 34 with an adjustable bypass 36 to the inlet temperature control module 12.

A low-pressure exhaust gas recirculation line leads from the end of the exhaust gas aftertreatment unit 22 via a low-pressure exhaust gas recirculation cooler 38 with an adjustable bypass 40 to the inlet of the compressor 8, wherein the ratio of fresh air drawn in by the compressor 8 and recirculated exhaust gas can be adjusted by means of a rotatable flap 42 in the intake channel 5.

The exhaust aftertreatment unit 22 is encased by a cover plate 44, the cover plate 44 defining a cavity 66 (fig. 3) surrounding the exhaust aftertreatment unit 22. The cavity 66 is fluidly connected to the inlet duct 4 via the warm air conduit 46 and comprises a plurality of inlet openings 48 that open to ambient air. Mounted in the intake pipe 4 is a flap 50, which flap 50 is pivotable along the indicated double arrow and by means of which flap 50 the ratio of air at ambient temperature that is directly sucked in to air that is sucked in via the warm air line 46 can be adjusted, the air that is sucked in via the warm air line 46 being warmer than ambient temperature when the exhaust aftertreatment unit 22 is at operating temperature. The above mentioned air ratio can be adjusted between 0% and 100%, but it is generally not harmful if the flap 50 is closed in its end position without a particularly pronounced sealing action and therefore the air ratio can be adjusted within a range of slightly less than 0% to 100%.

The cover plate 44 forms an exhaust/intake heat exchanger together with the outer surface of the exhaust aftertreatment unit 22. In the enlarged view of FIG. 2, two or more possible airflow paths through the intake opening 48 around the outer surface of the exhaust aftertreatment unit 22 to the warm air conduit 46 are indicated by arrowed lines 52.

The figure also shows various mass flows, in particular the mass flow W of the air at ambient temperature that is drawn in_{Air, cold}Heated by the exhaust-gas aftertreatment unit 22Mass flow W of air_{Air, heat}Air mixture W_{Air, cold}+W_{Air, heat}Mass flow W of_{Air (a)}Low pressure egr mass flow W from low pressure egr cooler 38 to the inlet of compressor 8_LP，EGRHigh pressure EGR mass flow W from the high pressure EGR cooler 34 to the inlet temperature control module 12_HP，EGRAnd total intake mass flow W from the inlet temperature control module 12 to the intake manifold 18 of the internal combustion engine 2_AP。

Sensors, in particular an intake air temperature sensor 54 and an intake air mass flow sensor 56 in the intake passage 5 just downstream of the air filter 6, and an oxygen sensor 58 in the intake manifold 18 of the internal combustion engine 2 for measuring the oxygen content in the intake manifold 18 in order to be able to realize the so-called F, are also shown in the figures as small circles or black dots_MANThe adjustment is made to improve the combustion process in the cylinder.

If the currently available waste heat and the current fresh air requirement of the internal combustion engine and the current ambient temperature permit this, during operation of the internal combustion engine the mixing ratio between the air at ambient temperature from the inlet line 4 and the heated air from the warm air line 46 is adjusted by means of the flap 50 such that the air mixture W_{Air (a)}Is set to a value between about 15 c and about 20 c. At higher temperatures, the flap 50 closes the warm air line 46 substantially completely so that the compressor 8 only draws in air at the temperature of the surroundings, and at very low temperatures, the flap 50 may close the inlet 4 completely or close the inlet 4 to such an extent that the compressor 8 only draws in heated air, or at least draws in heated air as much as possible.

In particular, the mixing ratio is set such that the air mixture W is present if possible_{Air (a)}Is adjusted to a value between about 15 c and about 20 c, which is defined according to the current temperature and/or humidity of the ambient air.

Alternatively, the mixing ratio may be set so that the air mixture W is_{Air (a)}Is adjusted to a value or any value between about 15 c to about 20 c.

The mixing ratio may be based on the air mixture W_{Air (a)}Is adjusted because the position of the flap 50 is defined by a bimetallic strip (not shown) whose temperature sensitive portion is exposed to the air mixture W_{Air (a)}Since said portion is arranged upstream of the air filter 6, for example in the intake channel 5 leading to the compressor 8, for example also at the location of the

sensors

54, 56.

Alternatively, the mixing ratio may be based on the air mixture W_{Air (a)}Is adjusted because the position of the flap 50 is defined by an actuator 60, which actuator 60 is activated on the basis of a measurement from an intake air temperature sensor 62 arranged upstream of the air cleaner 6. This is illustrated in fig. 3, where a recirculation signal line 64 leads from an inlet air temperature sensor 62 to the actuator 60 of the flap 50, the air W drawn in from the inlet duct 4_{Air, cold}And air W drawn from the warm air line 46_{Air, heat}Is defined by the flap 50. If W is_{Air (a)}So low that there is a risk of condensate formation, e.g. at temperatures below 10 ℃ or 15 ℃, if possible, supplying more W_{Air, heat}And if W_{Air (a)}Higher than desired, e.g. higher than 20 ℃, if possible, supplying more W_{Air, cold}。

The intake air temperature sensor 62 should be positioned a sufficient distance downstream of the flap 50 so that the mass air flow W is before the temperature measurement_{Air, cold}And W_{Air, heat}Can be mixed well to form W_{Air (a)}. Instead of the dedicated intake air temperature sensor 62, the intake air temperature sensor 54 shown in fig. 1 and 2 may also be used in the intake passage 5 downstream of the air cleaner 6.

FIG. 3 also shows exhaust aftertreatment unit 22And a shroud 44 surrounding the exhaust aftertreatment unit 22, not in longitudinal section as shown in fig. 1-2, but rather in transverse section across its longitudinal axis. Two air inlets 48 are shown, ambient air W_{Air, cold}May flow through the air inlet 48 into the cavity 66 between the exhaust aftertreatment unit 22 and the cover plate 44, as indicated by the arrows.

The configuration shown in fig. 4 differs from the configuration shown in fig. 1 only in that instead of the warm air line 46, a warm air line 46 'opens into the intake pipe 4, wherein the warm air line 46' does not originate from an exhaust gas heat exchanger in the form of a cavity annularly surrounding the exhaust gas aftertreatment unit 22 as shown in fig. 1, but rather from a coolant heat exchanger 68, which coolant heat exchanger 68 receives ambient air W_{Air, cold}And heats the ambient air through thermal contact with coolant 70 from the internal combustion engine. The operation of the configuration corresponds to the operation of the configuration in fig. 1-3.

Claims

1. A method for preventing the formation of condensate upstream of a compressor (8) of a turbocharged motor vehicle internal combustion engine having low-pressure exhaust gas recirculation from an exhaust gas aftertreatment unit (22) via an exhaust gas recirculation cooler to an intake passage (5) of the compressor (8),

wherein,

the compressor (8) draws in an air mixture from the intake channel (5), which air mixture consists of air at ambient temperature and air that has been heated by the waste heat of the internal combustion engine, in a proportion that can vary substantially between 0% and 100%, the mixing ratio between the air at ambient temperature and the heated air being adjusted such that the temperature of the air mixture is adjusted, if possible, to a value that lies within a predetermined temperature range.

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

wherein

The predetermined temperature range lies between a lower temperature value of about 10 ℃ or 15 ℃ and an upper temperature value of about 20 ℃, and the value to which the temperature is adjusted is determined in dependence on the current temperature and/or the current humidity of the ambient air.

3. The method according to claim 1 or 2,

wherein,

at ambient temperatures above an upper temperature limit, the compressor (8) draws in substantially only the air at ambient temperature from the air intake passage (5), at ambient temperatures below a lower temperature limit, the compressor (8) draws in as much heated air as is available from the air intake passage (5), and at ambient temperatures between the upper and lower temperature limits, the compressor (8) generally draws in a mixture of the air and the heated air at ambient temperature from the air intake passage (5).

4. Method according to one of the preceding claims,

wherein

-generating said mixture of said air and said heated air at ambient temperature, after which said air mixture thus generated is mixed with a low-pressure exhaust recirculation gas and flows through said intake channel (5) into said compressor (8), and in particular, upstream of an intake air filter (6).

5. Method according to one of the preceding claims,

wherein

The heated air is drawn from a cavity (66), the cavity (66) is formed between an outer surface of the exhaust aftertreatment unit (22) and a housing (44) surrounding the exhaust aftertreatment unit (22), and the cavity (66) is fluidly connected to the ambient air through one or more openings (48).

6. The method according to one of claims 1 to 4,

wherein

The heated air is drawn from a heat exchanger (68), the heat exchanger (68) is fluidly connected to the ambient air, and the heat exchanger (68) is in thermal contact with the engine coolant (70).

7. Method according to one of the preceding claims,

wherein

The mixing ratio between the air at ambient temperature and the heated air is adjusted by means of a flap (50).

8. The method of claim 7, wherein the first and second light sources are selected from the group consisting of,

wherein

The position of the flap (50) is adjusted by means of a bimetallic element, the temperature of which is determined by or significantly influenced by the temperature of the air mixture.

9. The method of claim 8, wherein the first and second light sources are selected from the group consisting of,

wherein

The position of the flap (50) is adjusted by means of an actuator (60), the actuator (60) being activated by means of a signal based on the measurement of a temperature sensor (62).

10. The method according to claim 8 or 9,

wherein

The bimetallic element or the temperature sensor (62) is exposed to the air mixture.

11. An apparatus for preventing the formation of condensate upstream of a compressor (8) of a turbocharged motor vehicle internal combustion engine having low-pressure exhaust gas recirculation from an exhaust gas aftertreatment unit (22) via an exhaust gas recirculation cooler to an intake passage (5) of the compressor (8),

wherein,

the device is arranged for carrying out the method according to one of the preceding claims.