Patent Application
20190360392
The present invention relates to a method for controlling a device feeding an amount of air to the intake of an internal-combustion engine turbocharged by a single or twin-scroll turbocharger, notably for an engine of a motor vehicle, an industrial vehicle, or for a stationary system.
As is widely known, the power delivered by an internal-combustion engine depends on the amount of air fed to the combustion chamber of this engine, with amount of air being proportional to the density of the air.
Thus, it is usual to increase the amount of air through compression of the outside air before it is allowed into this combustion chamber. This operation, known as turbocharging, can be carried out using any means such as a turbocharger or a driven compressor, which can be a centrifugal or a positive-displacement compressor.
In case of turbocharging using a single-scroll turbocharger, a rotary single-inlet turbine is connected by a shaft to a rotary compressor. The exhaust gases from the engine flow through the turbine to rotate it. This rotation is transmitted to the compressor which, compresses the outside air before it is fed into the combustion chamber.
As is better described in French patent application No. 2,478,736, it is intended to increase the compression of the outside air by the compressor even further to significantly amplify this amount of compressed air in the compression chamber of the engine.
This is achieved more particularly by increasing the rotational speed of the turbine and therefore the rotational speed of the compressor.
Part of the compressed air exiting the compressor is therefore diverted directly to the turbine inlet while mixing with the exhaust gases. This turbine is then driven by a larger amount of fluid (mixture of compressed air and exhaust gas), which allows the rotational speed of the turbine, and therefore of the compressor, to be increased (Boost). This compressor speed increase thus raises the pressure of the outside air that is compressed prior to being fed to the combustion chamber of the engine.
Thus, the compressed air has a higher density, which allows the amount of air contained in the combustion chamber to be increased.
In the case of the improvement mentioned in French patent application No. 3,024,178 filed by the applicant, a twin-scroll turbocharger is used to divert part of the compressed air exiting the compressor so that it is directly allowed into each inlet of the turbine while mixing with the exhaust gases. This causes a further increase the speed of the turbine and of the compressor, as well as the amount of air sent to the engine.
It is also known from document EP-1,138,928 to associate this amplification (Boost) with an exhaust gas recirculation (EGR).
Indeed, most diesel engines are equipped with an exhaust gas recirculation circuit, referred to as EGR circuit, for limiting the emissions of NOx contained in these gases at source.
The exhaust gas recirculation as illustrated by document EP-1,138,928 allows feeding exhaust gas from the engine to the intake of this engine.
These types of turbocharged engines, although satisfactory, however involve some significant drawbacks.
The flow of compressed air admitted at the turbine inlet(s) is not correctly controlled, which may lead to poor engine performance.
Thus, by way of example, in a case when too large an amount of compressed air is diverted into the turbine inlet, the exhaust gases entering the turbine are cooled too much by this air, which causes a decrease in the overall turbocharging efficiency.
The present invention is directed to overcoming the aforementioned drawbacks by a method for controlling a device feeding an amount of air to the intake of a turbocharged internal-combustion engine which allows meeting all engine power demands, and in particular during transient operation phases.
The invention achieves and manages a compressed air transfer from the intake to the exhaust, even when the average pressure of the compressed air at the intake is lower than that of the gases at the exhaust. All that is required is that for phases during the engine operation cycle, the pressure at the intake is higher than that at the exhaust.
The present invention thus is a method for controlling the amount of air fed to the intake of a turbocharged internal-combustion engine, the engine comprising an intake manifold and at least one exhaust gas outlet connected to an exhaust manifold, the engine comprising a turbocharger with a turbine having at least one inlet connected to the at least one exhaust gas outlet and with an outside air compressor, and at least one turbine speed amplifier circuit with at least one transfer line for transferring the compressed air from the compressor to the turbine inlet under control by throttling, characterized in that:
The compressed air transfer from the compressor to the turbine inlet can be closed when the difference between the target compressed air flow rate and the estimated air flow rate is zero.
When the engine further comprises a recirculation circuit which sends the exhaust gas back to the intake manifold, the turbine speed amplifier circuit can be kept shut off in order to use only the exhaust gas recirculation circuit.
For use of the turbine speed amplifier circuit, the exhaust gas recirculation circuit can be shut off.
When the engine further comprises a recirculation circuit sending the exhaust gas to the intake manifold, the air flow rate fed to the turbine through the amplifier circuit is controlled to compensate for the recirculated exhaust gas flow rate, for simultaneous use of the turbine speed amplifier circuit and the exhaust gas recirculation circuit.
The compressed air flow rate can be estimated by measuring the intake flow rate.
The compressed air flow rate can be estimated by measuring the richness at the exhaust.
Other features and advantages of the invention will be clear from reading the description hereafter, given by way of non limitative example, with reference to the accompanying figures wherein:
In
Preferably, this engine is a direct-injection internal-combustion engine, notably of diesel type, but the invention is applicable to any other type of internal-combustion engine.
Each cylinder comprises an intake 14 with at least one intake valve (not shown) which controls an intake pipe 16. Intake pipes 16 are connected to an intake manifold 18 which is supplied with air, such as compressed air, through a supply line 20.
The cylinders also comprises a burnt gas exhaust 22 having at least one exhaust valve (not shown) which controls an exhaust pipe 24.
The exhaust pipes are connected to an exhaust manifold 26 with an exhaust gas outlet. The exhaust gas outlet is connected to a turbocharger 30 for providing air compression, and more specifically to the expansion turbine 32 of the turbocharger.
As illustrated in
Compressor 38 comprises an outside air intake 44 supplied by an air supply line 46. Compressed air outlet 48 of this compressor is connected to supply line 20 of intake manifold 18 by a compressed air line 50.
Advantageously, a compressed air cooling radiator 52 may be provided on line 50, between the compressor and line 20.
As is better seen in
The transfer line carries throttling means 58, such as a proportional valve, controlled by a control (not shown). This valve allows controlling the circulation of the compressed air passing through the transfer line. The line also comprises a non-return valve 60, which prevents circulation of the compressed air from the line to the compressor.
This configuration thus allows, during operation of the engine, to feed compressed air into the turbine for increasing the flow rate of the turbine, and therefore of the compressor. This also allows achieving more efficient turbocharging at low engine speeds.
The example of the configuration of
In this configuration, the exhaust pipes of first cylinder 121 and of second cylinder 122, which form a first group of at least one cylinder, are connected to a first exhaust manifold 26′ with a first exhaust gas outlet 28′. The exhaust pipes of the third and fourth cylinders 123 and 124, which form a second group of at least one cylinder, are connected to a second exhaust manifold 26″ comprising a second exhaust gas outlet 28″.
The two exhaust gas outlets lead to the turbine with a first exhaust gas inlet 34′ connected to first exhaust gas outlet 28′ of first manifold 26′ and a second inlet 34″ connected to second exhaust gas outlet 28″ of second exhaust manifold 26″.
Gas outlet 40 of the turbine is conventionally connected to exhaust line 42 of the engine.
As visible in
More precisely, each partial transfer line 54′ and 54″ originates respectively from nonreturn valves 60′ and 60″, at an intersection point 56′ and 56″ between the compressor and cooling radiator 52. One 54′ of the lines ends at inlet 34′ of the turbine through its junction with first exhaust gas outlet 28′, while the other 54″ line ends at the other inlet 34″ of this turbine through its junction with second exhaust gas outlet 28″.
Each line carries throttling means 58′ and 58″, such as a proportional valve, controlled by a control that may be common to the two throttling means. This valve thus allows controlling the circulation of the compressed air passing through the line.
Advantageously, each line also comprises a non-return valve 60′ and 60″, which prevents circulation of the compressed air from the line to the compressor.
This configuration thus allows, during operation of the engine, to take advantage of the exhaust low-pressure zones occasionally prevailing in the exhaust manifolds in order to feed compressed air into the turbine and thus to increase the flow rate of this turbine, and therefore of the compressor. This also allows achieving more efficient turbocharging at low engine speeds.
As illustrated in
As is more visible in the variant of
A recirculation line 62 therefore connects transfer line 54 to air supply line 20.
This line preferably passes through a heat exchanger 64 suited for exhaust gas cooling and it carries throttling means 66, such as a preferably proportional valve.
In this variant, the engine can operate either with the amplifier circuit (Boost circuit) or with the exhaust gas recirculation (EGR) circuit by suitably controlling valves 58 and 66.
It should be noted that valves 58 and 66 can be replaced by a 3-way valve whose function is equivalent for controlling the various streams.
Of course, as in the configuration illustrated in
Both exhaust gas outlets end at the turbine with a first exhaust gas inlet 34′ being connected to first exhaust gas outlet 28′ of first manifold 26′ and a second inlet 34″ being connected to second exhaust gas outlet 28″ of second exhaust manifold 26″.
As can be seen in
More precisely, each partial transfer line originates from line 60, at an intersection point 56′ and 56″ between the compressor and cooling radiator 52. One 54′ of the lines 54′ ends at inlet 34′ of the turbine through its junction with first exhaust gas outlet 28′; while the other 54″ line ends at the other inlet 34″ of this turbine through its junction with second exhaust gas outlet 28″.
Each line carries throttling means 58′ and 58″, such as a proportional valve, controlled by a control that may be common to the two throttling means. This valve thus allows controlling the circulation of the compressed air passing through the line.
Advantageously, each line also comprises a non-return valve 60′ and 60″, which prevents circulation of the compressed air from the line to the compressor.
In this configuration, recirculation line 62 is connected to the two transfer lines 54′ and 54″ by lines 62′ and 62″.
During operation, and as illustrated in
As illustrated in the second variant of
Therefore, and for the Boost circuit and the EGR circuit to operate simultaneously, both circuits are connected on exhaust manifold 26 at two sufficiently spaced far apart points and outlet 28 sending the exhaust gas to inlet 34 of turbine 32 is positioned between the two points.
More precisely, in the case of a turbocharger 30 with a turbine 32 having a single inlet 34, transfer line 54 ends at a point 68 of the manifold and exhaust gas recirculation line 62 originates from another point 70 of the manifold distant from arrival point 68, and point 72 of outlet 28 sending the exhaust gas to inlet 34 of turbine 32 is positioned between these two points.
As mentioned for
Thus, for manifold 26′, transfer line 54′ leads to a point 68′ of manifold 26′, exhaust gas recirculation line 62′ starts at another point 70′ of manifold 26′ and point 72′ of outlet 28′ sending the exhaust gas to inlet 34′ of turbine 32 is positioned between these two points.
Similarly, for manifold 26″, transfer line 54″ leads to a point 68″ of manifold 26″, exhaust gas recirculation line 62″ starts at another point 70″ of manifold 26″ and point 72″ of outlet 28″, which sends the exhaust gas to inlet 34″ of turbine 32, is positioned between these two points.
As shown in
To ensure suitable operation of the engines described above, it is essential to use a control method so that the compression ratio of the air exiting the compressor and/or so that the amount of exhaust gas sent to the engine intake correspond to the operating points of these engines as contained in the designed engine map.
It is therefore necessary to use a method which knows the target compressed air flow rate (Qair obj) to be fed to the turbine according to a predetermined engine map giving the target compressed air flow rate (Qair obj) as a function of the engine operating point characteristics of speed, torque, etc., and which corrects the estimated air flow rate at the turbine inlet (Qair est) to approximate the target flow rate, in order to obtain the compression ratio of the air at the compressor outlet to be fed to the intake manifold to correspond to the engine operating point.
Thus, in general terms, with this method:
It should be noted that several types of compressed air flow rate estimators can be considered.
Notably, a flow rate estimator with intake flow rate measurement and engine volumetric efficiency knowledge can be used:
In the case without EGR:
In case of use of Boost or EGR:
In case of use of Boost and/or EGR:
A flow rate estimator measuring the richness at the exhaust can also be used.
In the case without EGR:
In case of use of Boost or EGR:
In case of use of Boost and/or EGR:
With reference to the examples of
One of the points, P1, requires amplification of the speed of turbine 32 (Boost zone) of turbocharger 30 in order to obtain, at the outlet of compressor 38, the desired air compression ratio to be allowed into the intake manifold.
The other point, P2, is in an operating zone where the amount of exhaust gas fed to the turbine through exhaust gas outlet 28 is sufficient to obtain the air compression ratio at the compressor outlet.
For operating point P1:
In the case of operating point P2, the amount of exhaust gas fed to the turbine through outlet 28 (or 28′, 28″) is sufficient to obtain the desired air compression ratio at the outlet of compressor 38.
Therefore, the estimation of the amount of compressed air to be allowed into turbine 32 corresponds to that of the target amount with a zero difference between the two amounts, and closing of valve 58 (or 58′, 58″) is controlled.
Thus, switching from the engine operation in the Boost zone to the other zone only requires closing valve 58 (or 58′, 58″).
The variant of
In this variant, the synergy between the use of the EGR circuit and the Boost circuit also involves a method allowing suitable control of the two circuits. This control is intended to make the most of the combination of the two circuits. This method thus allows controlling the opening and the closing of the valves to optimize engine response.
In order to better explain the method, two operating points (P1 and P2) are selected (see
Point P1 requires amplification of the speed of turbine 32 (Boost zone) of turbocharger 30 in order to obtain, at the outlet of compressor 38, the desired air compression ratio.
The other point, P2, is in an engine operating zone (EGR zone) where recirculation of the exhaust gas to the engine intake is necessary to limit pollutant emissions, notably NOx, and where the amount of exhaust gas fed to the turbine through exhaust gas outlet 28 is sufficient to obtain the air compression ratio at the compressor outlet.
In this variant, and for operating point P1:
For operating point P2, the amount of exhaust gas fed to the turbine through outlet 28 (or 28′, 28″) is sufficient to obtain the desired air compression ratio at the outlet of compressor 38, and closing of valve 58 (or 58′, 58″) is controlled since the estimation of the amount of compressed air to be allowed into turbine 32 corresponds to that of the target amount.
Upon closing of valve 58 (or 58′, 58″), opening of valve 66 of the EGR circuit is controlled to allow exhaust gas into engine intake 18.
Conversely, when switching from the EGR zone to the Boost zone, closing of valve 66 of the EGR circuit is controlled and opening of valve 58 (or 58′, 58″) is controlled.
The variant of
Unlike the variant of
By way of example only, three operating points (P1, P2 and P3) are selected (see
Point P1 requires amplification of the speed of turbine 32 (Boost zone) of turbocharger 30 in order to obtain, at the outlet of compressor 38, the desired air compression ratio.
Point P2 is in an engine operating zone (EGR zone) where recirculation of the exhaust gas to the engine intake is necessary to limit pollutant emissions, notably NOx, and where the amount of exhaust gas fed to the turbine through exhaust gas outlet 28 is sufficient to obtain the air compression ratio at the compressor outlet.
Finally, point P3 is in an engine operating zone (Boost zone+EGR zone) where amplification of the speed of turbine 32 (Boost zone) of turbocharger 30 is required and where recirculation of the exhaust gas to the engine intake is also necessary to limit pollutant emissions, notably NOx, while allowing obtaining the desired air compression ratio at the outlet of compressor 38.
In this variant, and for operating point P1:
For operating point P3 of the EGR zone, the compressed air flow rate estimation is zero, which leads to the closing of valve 58 (or 58′, 58″) since the amount of exhaust gas fed to the turbine through outlet 28 (or 28′, 28″) is sufficient to obtain the desired air compression ratio at the outlet of compressor 38.
As for point P2, the speed amplifier circuit is controlled identically to that of point P1 (estimation+measurement+comparison), with the difference that controls the degree of opening or of the degree of closing of valve 58 (or 58′, 58″) is also dependent on the degree of opening of valve 66 of the EGR circuit for the amount of exhaust gas sent to the intake manifold. This allows obtaining an exhaust gas amount at the turbine inlet corresponding to the operating point demand.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1662489 | Dec 2016 | FR | national |
Reference is made to PCT/EP2017/080973, filed Nov. 30, 2017, and French Application No. 16/62.489 filed Dec. 15, 2016, which are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/080973 | 11/30/2017 | WO | 00 |
