DE102007051845A1 - Turbocharger and method for generating a pre-whirl before a compressor of the turbocharger - Google Patents

Abstract

The invention relates to a method for generating a pre-whirl in front of a compressor of a turbocharger, comprising the steps of: providing a valve arrangement, wherein air can be supplied via the valve arrangement, for generating a pre-whirl in front of the compressor; Determining if the compressor is stalled and thus pumping the compressor during operation, and if it is determined that pumping of the compressor occurs, the valve assembly is driven so that sufficient air can be supplied to the compressor via the valve assembly, so that a pre-whirl is generated in front of the compressor sufficient to substantially completely prevent pumping of the compressor.

Description

The The invention relates to a turbocharger and a method for generating a predrunk in front of a compressor of the turbocharger to the occurrence To reduce the pumping of the compressor or substantially completely to suppress.

Of the Compressor of an exhaust gas turbocharger is characterized by a map, in which the pressure as a function of the turbocharger speed and the mass flow is indicated, for a corresponding Turbocharger speed and a corresponding mass flow, a generate predetermined pressure according to the map leaves. This map becomes at high mass flows limited by the so-called Stopfgrenze. For small mass flows the map is limited by the surge limit. This so-called surge limit occurs due to a stall at the compressor wheel inlet or at the compressor wheel outlet or both.

Out The prior art is known that by means of the pre-swirl the surge limit in the compressor map to smaller mass flows to shift. The Vordrall can be with the help of Vorleitapparaten in radial or axial design realize.

In the state of the art, as in the US 20070039320 is disclosed, a method for controlling the pumping in radial or axial compressors is further described. In this case, a device for controlling the pumping of a compressor includes an air circulation line. This is connected at one end downstream to the compressor outlet and at the other end upstream to the compressor inlet. The air circulation duct circulates air from the compressor outlet to the compressor inlet. Furthermore, a mixer device and an air cooling device are provided.

Furthermore, the describes US 6,779,344 also a method of controlling the pumping in a compressor. In this case, a control system is disclosed which has an air nozzle between the compressor and the engine, and a so-called. Wastgate. The wastegate is arranged upstream of the engine and downstream of the turbine.

In addition, the describes US 6,793,455 a method, wherein a control device is provided, which controls a vent valve and / or a fuel valve. The control device controls the vent valve in such a way so that the compressor on the one hand can achieve a maximum pressure, and on the other hand at this pressure no pumping occurs in the compressor.

The previously described methods are all based on an air mass flow from a tap behind the compressor through a valve to control an injection point in front of the compressor so that the operating point of the compressor to higher mass flows is moved and the compressor in a stable map area located.

Therefore It is the object of the present invention, a method and to provide a device, wherein a surge line of a compressor can be moved by means of generating a pre-whirl, so that pumping the compressor at least reduced or substantially can be completely prevented, taking on the use of Vorleitapparaten can be waived.

These The object is achieved by a method having the features of the patent claim 1 solved.

• – Bereitstellen einer Ventilanordnung, wobei über die Ventilanordnung Luft bereitstellbar ist, zum Erzeugen eines Vordralls vor dem Verdichter,
• – Bestimmen, ob bei dem Verdichter im Betrieb ein Strömungsabriss und damit ein Pumpen des Verdichters auftritt,
• – wobei, wenn festgestellt wird, dass ein Pumpen des Verdichters auftritt, die Ventilanordnung so angesteuert wird, dass ausreichend Luft über die Ventilanordnung dem Verdichter zugeführt werden kann, so dass ein Vordrall vor dem Verdichter erzeugt wird, der ausreichend ist, das Pumpen des Verdichters zumindest zu reduzieren oder im Wesentlichen ganz zu verhindern.

Accordingly, according to the invention, a method is provided for generating a pre-whirl in front of a compressor of a turbocharger, comprising the steps:

• Providing a valve arrangement, air being able to be supplied via the valve arrangement, for producing a pre-orifice in front of the compressor,
• Determining whether a stall occurs in the compressor during operation and thus a pumping of the compressor,
• Wherein, when it is determined that pumping of the compressor occurs, the valve assembly is driven so that sufficient air can be supplied to the compressor via the valve assembly so that a pre-charge is created in front of the compressor sufficient to pump the compressor at least reduce or substantially completely prevent it.

The method has the advantage that targeted a pre-whirl can be generated before the compressor or the Verdichterradeintritt, which is suitable to reduce the pumping of the compressor or at least essentially to prevent. By way of the valve arrangement, sufficient air is supplied to the compressor so that a suitable pre-whirl can be generated.

advantageous Refinements and developments of the invention will become apparent the dependent claims and the description with reference on the drawings.

In an embodiment of the invention is in the step of determining whether a pump of the compressor initially there is a pressure curve of a pressure of the air mass flow determines, which allows a conclusion, whether when the compressor is pumping or not. Is found the pressure profile of the pressure reaches or exceeds a surge limit, so will an analysis of the amplitude of the pressure curve of the pressure for example, performed in a customized frequency range. It is determined whether the amplitude exceeds a predetermined limit. For example, the threshold is set to have a value indicates for the amplitude, from which a pumping at the compressor occurs. If the limit is reached or exceeded, so it can be determined that pumping the compressor is present. In this case, the valve arrangement can be controlled, a suitable pre-whirl before the compressor or the compressor wheel entry to create. This way, through an active control, while the operation of the turbocharger, the occurrence of the pumping of the compressor be prevented.

In a further embodiment of the invention is closed as a pressure on the basis of a pump of the compressor can be, for example, the pressure of the air mass flow behind the compressor outlet, the pressure of the air mass flow before the compressor inlet, the pressure behind the diffuser exit and / or the pressure before the diffuser inlet determined. These pressures have the advantage of being easy to draw conclusions about allow the occurrence of stalls on the compressor wheel and thus an occurrence of a pumping of the compressor.

According to one other embodiment of the invention For example, the valve assembly includes a bleed valve a variable cross section. This has the advantage that the Air mass flow, the compressor via the bleed valve is fed, can be controlled selectively. It can the compressor, for example, depending on the Pressure, so much air are supplied, that a pre-twist is generated before the compressor, sufficient to pump the At least reduce or completely prevent compressor.

In a further inventive embodiment has the bleed valve, for example, a sampling point for Air in the spiral of a compressor housing, at the height a diffuser of the compressor or behind the wheel outlet of the Compressor wheel on. Basically, the sampling point the bleed valve but also at any other position on the turbo charger be arranged, which is suitable to remove air and the compressor supply.

According to one other embodiment of the invention is at the step of determining whether a pump of the compressor is present, at least one map provided in which the Pumping limit of the compressor is specified. The map can the Pumping limit thereby depending on the air mass flow and indicate a pressure ratio. Depending on the instantaneous air mass flow and the instantaneous pressure ratio can be determined whether the surge limit reached and exceeded becomes. In this case, air is released via the valve arrangement fed to the compressor to a targeted Vordrall ago to produce the compressor sufficient to pump the compressor to prevent.

In a further embodiment of the invention has the valve assembly, such as a bleed valve, a variable cross section, for example, the turbocharger speed, the air mass flow and the pressure ratio Π depends. In this case, one of the pressure ratio Π dependent Air mass flow discharged through the valve assembly or supplied to the compressor. The air mass flow is the same chosen that he is sufficient to a suitable Vordrall in front of the compressor to produce a pumping of the compressor at least to reduce or substantially prevent. In this way can be relative to the map simply be determined or estimated, whether a pump occurs on the compressor and a corresponding Vordrall over the valve assembly can be generated to suppress the pumping.

The Invention will be described below with reference to the schematic figures the drawings specified embodiments closer explained. Show it:

1 a flow chart for controlling a pre-whirl according to a first embodiment of the invention;

2 a diagram in which the pressure curve of a pressure P2 before a diffuser outlet as a function of the time t is shown;

3 a flow chart for controlling a pre-whirl according to a second embodiment of the invention; and

4 a diagram in which different speed lines and a respective surge limit are shown depending on a pressure ratio and a mass flow.

In 1 First, a flowchart is shown which represents a first embodiment of the method according to the invention.

A active control for shifting the surge line to smaller mass flows, in order to prevent a "pumping" of the compressor, according to the first embodiment is carried out as follows.

In a first step S1, for example, a pressure P2 of the air mass flow behind a compressor outlet of a turbocharger (not shown) measured. Basically, this can be a pressure of the air mass flow but also, for example, before and / or behind the compressor or behind the diffuser outlet (pressure P3) and / or before the diffuser inlet be measured.

Furthermore, it is now determined in a second step S2 whether the pressure profile of the pressure P2 is a surge limit 10 reached. When reaching the surge limit 10 At the compressor, an essentially periodically recurrent drop in the mass flow occurs, which in turn results in a substantially periodic fluctuation of the pressure P2 at the compressor outlet. In this case, a so-called "pumping" of the compressor can occur. This "pumping" of the compressor is based on the fact that local backflows occur in a correspondingly large number of blade channels or in all blade passages of the compressor wheel, so that it ultimately comes to a stall. The "pumping" of the compressor in this case, for example, lead to bearing damage and thus damage the turbocharger.

In a further step S3 is now the pressure fluctuation of the pressure P2 at the compressor outlet or its amplitude, for example in an adapted frequency range, analyzed or monitored and determines if a "pumping" of the compressor occurs or not. For example, with the adjusted frequency range Aspects, such as the natural frequency and the harmonics of the intake system of the engine, etc., as much as possible exact inference to allow whether a "pumping" of the compressor takes place or not.

exceeds the amplitude of the oscillation of the pressure P2 is now a predetermined one Limit, so it is detected or determined in step S3 (S3: Yes) that the compressor is "pumping". The limit gives a value for the size the amplitude at which a "pumping" of the compressor occurs or a stall occurs. Is the amplitude smaller? as the limit, so there is no case of "pumps" at the compressor before (S3: No) and the analysis of the amplitude the pressure oscillation is continued, for example.

If it is now determined in step S3 that the case of "pumping" is present in the compressor (S3: yes), then in a next step S4 at least one bleed air valve is actuated, which provides bleed air, in order to make a targeted pre-whirl before the wheel entry of the compressor to create. The bleed air valve may, for example, have an extraction point for air in the spiral of the compressor housing, at the level of the diffuser and / or behind the wheel outlet or at any other point in the turbocharger housing which is suitable for taking air. The bleed valve then feeds the extracted air to the compressor prior to the compressor wheel inlet to produce a pre-whirl prior to wheel entry that is capable of preventing or at least reducing so-called "pumping" of the compressor. Here, the surge limit 10 as in 1 is indicated in a range of lower mass flows m • be moved in order to prevent in this way the "pumping" of the compressor.

The bleed valve is doing for example via a motor, such. B. a stepper motor, so actuated, so that it opens, for example, a dependent of the turbocharger speed N cross-section A, wherein the bleed air valve thereby allows a dependent on the pressure P2 air mass flow m • flow, which generates a pre-whirl before the compressor, which is sufficient to the surge limit 10 in the compressor map and to prevent a "pumping" of the compressor or at least reduce. The shifting of the surge line 10 is described below on the basis of the map in 4 the second embodiment of the invention explained in more detail.

The A bleed air valve with a variable cross-section A, as described above has, for example, a conical valve seat, wherein about the slope of the conical seat and the feed of the cross section A of the bleed air valve is adjusted to a predetermined Let air mass flow m to drain. The invention is but not on a Kegelventilssitz at the bleed valve limited. In addition to a bleed valve can also also any other valve or valve combination used which can be suitably operated or controlled to allow a predetermined air mass flow m • to flow.

in the Following the generation of the pre-whirl will be the measurement of the pressure P2 of the air mass flow again performed or continued (step S1) and determines whether a "pumping" of the Compressor occurs again (steps S2, S3) and a corresponding Control intervention (step S4) is necessary.

In 2 a diagram is shown in which the pressure P2 is plotted on the compressor outlet as a function of the time t. The pressure P2 reaches the previously described surge limit at a time t1 10 , In this case, a recurring substantially periodic dip in the mass flow occurs, which in turn results in substantially periodic variations in the pressure curve of the pressure P2.

If the amplitude of the pressure oscillation or fluctuation of the pressure P2 now exceeds the predetermined limit value from which a "pumping" of the compressor occurs, then a regulating intervention takes place for shifting the pumping limit and for preventing the "pumping" of the compressor 12 is in 2 drawn with an upper and lower dashed line.

So if a "pumping" of the compressor is detected, then an intervention to shift the surge line 10 , This is done by the bleed air valve, for example, by a control device, such as the engine control is controlled, or its actuator, such as the engine described above. In this case, the bleed air valve is actuated in such a way that it opens, for example, a cross-section A dependent on a rotational speed N. As an actuating device for actuating the bleed air valve, as described above, for example, a stepper motor may be provided or another suitable motor. In principle, however, any other type of operation of the bleed air valve can be provided, with which the bleed air valve can be suitably adjusted to provide a desired air mass flow m •.

As described above, the bleed air valve allows a dependent of the pressure P2 air mass flow m • flow. This is, for example, supplied to the compressor in such a way that a suitable pre-whirl is generated before the compressor, which is sufficient to prevent a "pumping" of the compressor and the surge limit 10 to move to a range of lower mass flows m, as in 2 is shown. In this case, a higher target pressure can be achieved, as in 2 is shown.

In 3 Now, a second embodiment of the invention is shown. This differs from the first embodiment according to the invention substantially in that instead of analyzing the amplitude of a pressure curve, a characteristic diagram 16 with a surge line 10 is determined by which it is determined whether a "pumping" of the compressor is present or not.The statements made to the first embodiment therefore essentially apply to the second embodiment.

The map used in the second embodiment 16 For example, has an operating range for the turbocharger, in which a surge line 10 is predetermined, depending on operating parameters, such as the air mass flow m • and a pressure ratio Π. The pressure ratio Π is composed, for example, as follows:

Based on this map 16 is during operation of the turbocharger in a first step S1 * first an instantaneous air mass flow m • ₁ and a current pressure conditions Π ₁ determined. Based on the map 16 is then determined in a second step S2 *, if the surge limit 10 is exceeded and a "pumping" of the compressor occurs or not In the present case, the surge limit 10 over steps, as in the map 16 in 3 is shown. In this case, the instantaneous air mass flow m • ₁ and the instantaneous pressure ratio Π ₁ can be determined and evaluated, for example, continuously or continuously or at regular or irregular intervals.

After it has been determined in the second step S2 * that the surge limit 10 has been exceeded and thus a "pumping" occurs in the compressor, in a next step S3 *, a corresponding pre-whirl is achieved by driving a suitable valve as a valve, as in the first embodiment, for example, a bleed air valve is used, the z The embodiments of the bleed-air valve in the first embodiment also apply correspondingly to the bleed-air valve of the second embodiment Alternatively to the bleed-air valve with a variable cross-section A, each other can also be used in the second embodiment Valve or any other combination of valves can be used, which can be suitably operated or driven to provide a predetermined air mass flow m •.

In the next step S3 *, therefore, the bleed air valve is controlled in such a way that sufficient air can be supplied to the compressor to produce a suitable pre-whirl before the compressor in order to prevent "pumping" of the compressor 10 suitably shifted into a range of smaller air mass flows m •.

The valve cross section A of the bleed air valve is, for example, from a corresponding 3-dimensional map 18 certainly. The map 18 indicates the valve cross-section A as a function of the air mass flow m •, the pressure ratio Π and the turbocharger speed N, as in 3 is shown. In this way, the bleed air valve is driven so that there is a shift to the surge line 10 suitable air mass flow m • can flow, which creates a suitable pre-ram in front of the compressor, to prevent the pumping of the compressor and thereby the surge limit 10 to move in the compressor map to smaller mass flows, with a higher target pressure can be achieved.

In 4 is further shown a diagram in which, for example, five different speed characteristics 14 are plotted, depending on the air mass flow m • and the pressure ratio Π.

verschoben werden kann. Des Weiteren kann, wie in 4 gezeigt ist, ein Arbeitspunkt in einen Bereich höherer Luftmassenströme m • verschoben werden bzw. wie in 4 dargestellt, von einem Punkt A* nach einem Punkt B*.From the diagram in 4 can be found here that the surge limit 10 in a conventional compressor in a range of higher mass air flows m •, whereas according to the invention, by the generation of a predrirl, the surge limit 10 into a range of small air mass flows

can be moved. Furthermore, as in 4 is shown, an operating point in a range of higher air mass flows m • be moved or as in 4 represented from a point A * to a point B *.

at the method according to the first and second embodiments In accordance with the invention, the pre-whirl is regulated in front of the compressor wheel. For this purpose, the bleed air of a bleed air valve is used, the one sufficient air mass flow m • before the compressor provides to create a suitable pre-whirl. The bleed air is in accordance with the first and second embodiment of the invention not just circulated to shift the mass flow to be used in the map, but uses a targeted To create a pre-twist that is sufficient for a respective "pumping" to prevent the compressor.

The Control according to the invention thus relates to a active control to shift the surge line and not directly for active control of the mass flow at the surge line. The se active Control to shift the surge line is achieved in the Pressure P2 in the first embodiment behind the diffuser outlet is measured to determine if a "pumping" of the compressor present or not. The first embodiment of the invention has the advantage that the occurrence of a "pumping" of the compressor can be determined more accurately and according to a suitable Vordrall can be generated. In this way, the efficiency of the turbocharger additionally be improved.

Even though the present invention above based on the preferred embodiments is described, it is not limited thereto, but Modifiable in a variety of ways. The previously described Embodiments are combined with each other, in particular individual features thereof.

For example, a combination of the two embodiments may be performed as follows. According to the second embodiment can first during the operation of the turbocharger on the basis of the map 16 (Step S1 *, step S2 *), it is determined whether the surge limit 10 is exceeded and one "Pumping" of the compressor occurs or not is determined in step S2 * that the surge limit 10 has been exceeded and thus a "pumping" occurs in the compressor, so in step S3 * a corresponding Vordrall provided by driving the bleed air valve.

In a further step, an active control intervention can now take place according to the first embodiment. In this case, in step S1, for example, a pressure P2 of the air mass flow behind a compressor outlet of the turbocharger is measured. Further, in step S2, it is determined whether the pressure waveform of the pressure P2 is the surge limit 10 achieved or whether there is a substantially periodic variation of the pressure P2 at the compressor outlet. In step S3, the pressure fluctuation of the pressure P2 or its amplitude is analyzed and it is determined whether or not a "pumping" of the compressor occurs, and if the amplitude of the vibration of the pressure P2 exceeds the predetermined limit value, it is determined in step S3 (FIG. S3: Yes) that the compressor is "pumping". In step S4, therefore, the bleed air valve is actuated to produce a targeted pre-whirl prior to the wheel entry of the compressor.

The previously described example is one possibility of several, how the two embodiments combined can be. The invention is based on this combination not limited.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 20070039320 [0004]
• - US 6779344 [0005]
• - US 6793455 [0006]

Claims (13)

Method for generating a pre-whirl before a Compressor of a turbocharger with the steps: a) Provide a valve assembly, wherein via the valve assembly air can be provided for generating a pre-whirl before the compressor, b) Determine if the compressor is stalling during operation and for pumping of the compressor to occur (steps S1, S2, S3; Steps S1 *, S2 *) c) where it is determined that a pumping of the compressor occurs, the valve assembly is driven so that sufficient air through the valve assembly to the compressor can be fed so that a pre-twist in front of the compressor is sufficient, the pumping of the compressor at least to reduce or substantially completely prevent (step S4; Step S3 *) A method according to claim 1, characterized in that the step c) for determining whether a pumping of the compressor is present further comprises the steps of: c1) determining a pressure profile of a pressure (P2, P3) of the mass air flow, which allows a conclusion as to whether Compressor Pumping Occurs or Not (Step S1), c2) Determining Whether the Pressure History of Pressure (P2, P3) Defines a Pumping Threshold (FIG. 10 ) or not (step S2), c3) the surge limit ( 10 ) are reached or exceeded, determine whether an amplitude of the pressure curve of the pressure (P2, P3) a predetermined limit ( 12 ), the limit ( 12 ) is exceeded, it is determined that there is a pumping of the compressor (step S3). Method according to at least one of the claims 1 or 2, characterized in that as pressure (P2), for example at least one or more of the following pressures determinable are, for example, the pressure (P2) of the air mass flow behind the compressor outlet, the pressure of the air mass flow before the compressor inlet, the pressure (P3) behind the diffuser outlet, the pressure before the diffuser inlet, the pressure in the spiral, the Pressure behind the spiral, the pressure behind the discharge nozzle. Method according to at least one of the claims 1 to 3, characterized in that the valve arrangement a controlled variable cross-section (A), for example via a sliding cone valve seat is generated. Method according to at least one of the claims 1 to 4, characterized in that the valve arrangement at least having a bleed air valve. Method according to claim 5, characterized in that that the bleed air valve, for example, at least one sampling point for air in the spiral of a compressor housing, at the height of a diffuser of the compressor and / or behind having the wheel outlet of the compressor wheel. Method according to at least one of the claims 4 to 6, characterized in that the variable cross section (A) the valve arrangement, for example, from the turbocharger speed (N) is dependent, wherein the valve arrangement is driven in such a way becomes (step S4), so that one of the pressure (P2, P3) dependent Air mass flow (m •) flows, which is sufficient to one to generate suitable pre-whirl before the compressor to pump at least reduce or substantially to the compressor prevent. Method according to at least one of claims 1 to 7, characterized in that the step c) for determining whether a pumping of the compressor is present further comprises the steps: C1) providing at least one characteristic map ( 16 ) in which the pumping limit of the compressor is specified, C2) determining whether the compressor is the surge limit ( 10 ), wherein when the surge limit is exceeded ( 10 ) determines that there is a pumping of the compressor (step S1 *, S2 *). A method according to claim 8, characterized in that the characteristic field the surge limit ( 10 ) of the compressor, for example, depending on an air mass flow (m •) and a pressure ratio Π shows. A method according to claim 9, characterized in that the pressure ratio

is. Method according to at least one of the claims 8 to 10, characterized in that the valve arrangement a variable cross-section (A), for example, the turbocharger speed (N), the air mass flow (m •) and the pressure ratio Π depends, the valve arrangement being controllable in this way (step S3 *), so that one of the pressure ratio Π dependent Air mass flow (m •) flows, which is sufficient to one to generate suitable pre-whirl before the compressor to pump at least reduce or substantially to the compressor prevent. Turbocharger with a compressor and a valve assembly for providing air to make a pre-whirl in front of the compressor to produce according to the method of one of Claims 1 to 11. Turbocharger according to claim 12, characterized in that the valve arrangement has at least one bleed air valve, wherein the bleed air valve via an actuating device is operable, wherein the actuating device For example, has a motor, such as a stepper motor.