Patent Application
20080034753
Refer now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike.
Disclosed herein are turbocharger (e.g., centrifugal turbocharger) systems comprising a turbocharger and a control system. The control system comprises a process controller capable of monitoring the operation of the turbocharger and detecting the onset of surging events prior to actual surge through monitoring surge precursors. Upon detecting the surge precursors, the process controller is capable of determining the proximity of a surging event and capable of adjusting the operating conditions of the turbocharger system to avoid surge, thereby maintaining efficient operation.
Illustrated in
During operation, the turbocharger 2 operates in a dynamic manner wherein its operating variables change often. Despite these frequent changes, it is desirable that the turbocharger 2 operates with high efficiency and at sufficient pressure ratio to meet the air requirements of the emissionized engine. Efficient operation is generally achieved when the turbocharger 2 is operating at a lower volumetric inlet volume and a high-pressure ratio. This can be visually represented as the exemplary performance map 30 illustrated in
As disclosed, it is desirable to operate the turbocharger 2 at a point of operation that is highly efficient and produces sufficient pressure ratio to meet engine-operating requirements. Therefore, as the operation of the turbocharger 2 approaches the surge boundary 36, efficiency generally increases until surging occurs, wherein efficiency, flow, and pressure ratio decrease rapidly. For example, four exemplary operating conditions, or points of operation, are illustrated on the performance map 30 as points of operation 40-46. As can be seen, point of operation 40 is disposed a substantial distance away from the surge boundary 36. Thus, at point of operation 40 no surge precursors are experienced by the turbocharger 2, wherein a surge precursor is defined as any information that indicates the turbocharger is approaching a surging event, such as an instability in operating temperature or compressor discharge pressure. Analyzing point of operation 42, this point of operation is disposed closer to the surge boundary 36, whereat the turbocharger 2 operates at greater efficiency and higher pressure ratio compared to point of operation 40, but can experience the onset of surge, wherein surge precursors are exhibited without actually experiencing a surge. To be more specific, the onset of surge is defined as the point of turbocharger 2 operation wherein the volumetric flow rate is relatively low compared to a relatively high pressure ratio, thereby generating a condition wherein, although surging does not occur, the operation of the turbocharger exhibits surge precursors. At point of operation 44, the turbocharger 2 operates at yet greater efficiency and pressure ratio, however surge precursors increase, indicating the compressor is on the verge of unstable operation. At point of operation 46, the turbocharger experiences a surging event whereat efficiency, pressure ratio, and flow decrease rapidly. Mechanical damage can also occur if operation in surge is left to continue.
Referring again to
In one embodiment, the controller 26 is capable of determining if the turbocharger 2 is exhibiting surge precursors, as well as determining the proximity of a surging event. The controller 26 is capable of these functions by employing the first sensor 22 and the second sensor 24 to provide temperature information (e.g., a temperature differential) about the air within the air inlet 16. The controller 26 can also compare the temperature information to memory to determine the proximity of a surging event.
These capabilities are based on the discovery that as a surging event approaches, a hot boundary layer of air migrates up the air inlet 16 (against the flow of the air therein) from the compressor 6. As the hot boundary layer advances, the temperature communicated to the controller 26 from the second sensor 24 increases as it is engulfed by the hot boundary layer, creating a temperature differential between the second sensor 24 and the first sensor 22. The presence of the temperature differential is the surge precursor as it indicates the hot boundary layer has reached the second sensor 24 and the turbocharger 2 is experiencing the onset of surge.
As the hot boundary layer further advances, the first sensor 22 is engulfed by the hot boundary layer, which causes the temperatures communicated to the controller 26 continue to increase as well as the temperature differential because the hot boundary layer comprises an internal temperature differential. As the boundary layer continues to advance past the first sensor 22, the temperatures communicated to the controller 26 continue to increase and the temperature differential continues to exist until the point of surging. Yet further, it has also been discovered that these surge precursors can be utilized to also determine the proximity of a surging event.
The ability to determine the proximity of a surging event is highly desirable because once this is determined, the controller 26 can alter the operating conditions of the turbocharger system to avoid surging, which prolongs the service life of the turbocharger 2, or the controller 26 may alter the operating conditions to achieve an increased efficiency, which reduces operating expenses.
In an exemplary embodiment, the second sensor 24 is positioned a distance of about 0.15 inches (0.381 cm) from the compressor 6, and the first sensor 22 and the second sensor 24 are positioned at an axial distance (axial with respect to the axis of the air inlet 16) equal to about 0.25 inches (0.635 cm) from one another. However, depending upon the specific design of the turbocharger 2 (e.g., compressor 6), air inlet 16, operating conditions, as well as the position of the sensors, and other variables, the configuration of the sensors will vary. The sensors can be positioned at any point along the length of the air inlet 16 that can provide sufficient information (e.g., a temperature differential) to the controller 26 to determine the onset of surge. In general, the sensors can be positioned less than or equal to about 12 inches, or more specifically, less than or equal to about 6 inches, or even more specifically, less than or equal to about 1 inch from the compressor 6.
The specific temperatures and/or temperature differentials that are indicative of the onset of surge will vary based on variables such as turbocharger 2 design (e.g., compressor design), air outlet 14 design (e.g., length or diameter), operating conditions, sensor positions, and others. Therefore, the controller 26 can compare the information received from the sensors to memory (e.g., an operational map, a look-up table, a data array, and so forth) to determine if the turbocharger 2 is experiencing the onset of surge and/or the proximity of a surging event.
The memory accessed by the controller 26 is desirably programmed by the manufacturer based upon experimental test results, however the information in the memory can be empirically determined by the controller 26 or the user. The memory can be connected in operational communication to the controller 26 or integral therein.
Referring now to the exemplary flowchart in
Next, the controller 26 determines if the turbocharger 2 is exhibiting surge precursors. This can be determined utilizing any of the operating conditions measured as well as memory (e.g., a performance map, look-up table, data, algorithms, and so forth). For example, the memory can consist of a look-up table wherein the controller 26 utilizes the current operating conditions (e.g., the temperature differential between the first sensor 22 and the second sensor 24) to look-up a limit, wherein if the operating conditions are above the limit the turbocharger 2 is exhibiting surge precursors, and if the operating conditions are below the limit the turbocharger is not exhibiting surge precursors. In one specific example, the temperature differential between a first temperature measurement supplied by the first temperature sensor 22 and a second temperature supplied by the second temperature sensor 24 can be determined by the controller 26 and, for example, compared to a limit within memory (e.g., look-up table). If the temperature differential is greater than or equal to the limit, the controller 26 determines that the turbocharger 2 is exhibiting a surge precursor. If the temperature differential is less than the limit, the controller 26 determines that the turbocharger 2 is not exhibiting a surge precursor.
In another embodiment, the memory can comprise a performance map, wherein the controller 26 utilizes the current operating conditions (e.g., rotational speed, flow rate, pressure ratio, and/or temperatures) to determine a current point of operation (see
In yet another embodiment, the current operating conditions of the turbocharger 2 can be employed to locate a specific algorithm within the memory, wherein the algorithm can be employed to calculate a point of operation whereat surge precursors are exhibited.
If the turbocharger 2 is not exhibiting signs of the onset of surge (e.g., surge precursors), the controller can continue to monitor the operating conditions and compare the operating conditions to memory as discussed above.
If the controller 26 determines the turbocharger 2 is exhibiting surge precursors (e.g., using wavelet function processor), the next step of the method can be initiated wherein the proximity of a surging event is determined. To be even more specific, the proximity of a surging event is a determination of when the turbocharger 2 will experience surge from the turbocharger's current point of operation. The proximity of a surging event can be determined utilizing any of the operating conditions measured as well as memory (e.g., a performance map, look-up table, data, algorithms, and so forth), and can be determined with respect to an operating condition. For example, the controller 26 can determine the turbocharger 2 will experience surge if the revolutions per minute (RPM) of the turbocharger reaches a certain value under the current operating conditions.
In another embodiment, the controller 26 can make use of converging or diverging trends in the temperature differential to determine the proximity of a surging event. In yet another embodiment, the controller 26 can determine a current temperature and the current rate of temperature change of the second temperature sensor 24. The current temperature and rate of temperature change can then be compared to a look up table to determine the proximity of the surging event via extrapolation. In yet another embodiment, the controller 26 can utilize the current operating conditions of the turbocharger 2 to locate a specific algorithm within the memory that can be employed to calculate a point of operation whereat surging will occur.
Once the controller 26 has determined if the turbocharger 2 is exhibiting signs of the onset of surge, and has determined the proximity of surge, the next step of the method is to determine the action to be taken. The action to be taken can be for any reason, such as to avoid surge or to increase the operating efficiency of the turbocharger 2. The determination can be made utilizing any of the operating conditions measured as well as memory (e.g., a performance map, look-up table, data, algorithms, and so forth). In one embodiment, the controller 26 can first determine if an action is desired to avoid surging by evaluating the proximity information determined in the prior step. If an action is not desired to avoid surging, the controller 26 can then evaluate if an action is desired to increase efficiency. To do so, the controller 26 can compare the temperatures supplied by the first sensor 22 and the second sensor 24, and the temperature differential therebetween, to a look-up table, wherein the look-up table provides information regarding the turbocharger's efficiency to the controller 26.
In another example, the controller 26 can determine that although the turbocharger 2 is operating at an acceptable efficiency, the proximity of a surging event is unacceptable, and therefore an action is performed to avoid surge.
The specific action determined by the controller 26 will depend upon the specific configuration of the turbocharger system. For example, the controller 26 can be connected to an operational device, such as backpressure valve disposed in fluid communication with the air outlet 14, wherein the backpressure valve is capable of bleeding off air to adjust the pressure ratio of the turbocharger 2 to avoid surging. In another embodiment, the controller 26 can be capable of controlling the operation of a pressure recycle circuit wherein a portion of the high pressure air from the air inlet 16 can be directed into the air outlet 14 to avoid surging. It is to be understood that additional devices and systems can be employed to avoid surging.
In the above methods, exemplary methods are disclosed for determining if surge precursors are being exhibited by a turbocharger 2 as well as methods for predicting the proximity of a surging event. It is to be apparent to those skilled in the art that many methods can be employed for these functions, such as employing mathematical prediction methods (e.g., algorithms, trend estimation, extrapolation, interpolation, and so forth), statistical methods (e.g., probability, regression analysis, and so forth), as well as other predictive methods.
In the previous embodiments temperature measurement is employed to determine if surge precursors are evident and to determine the proximity of a surging event. However, it has also been discovered that pressure-based surge precursors can also be identified, therefore enabling the use of pressure measurement to detect the onset of surge. Yet further, it has also been discovered that these pressure-based surge precursors increase in amplitude as a turbocharger's operation nears the surge boundary 36. Therefore, the proximity of a surging event can be determined.
To be more specific, as a turbocharger 2 approaches a surging event, it has been discovered that the signal received from a pressure sensor exhibits a significant increase in amplitude at frequencies less than or equal to about 10 Hz. Further, as the point of operation of the turbocharger 2 nears a surging event, the amplitude of these frequencies further increases.
Referring now to
The first pressure sensor 54 is disposed on the air inlet 16 and in operational communication with the air therein. The second pressure sensor 56 is disposed on the air outlet 14 and in operational communication with the air therein. In one specific embodiment, the first pressure sensor 54 is positioned at an axial distance (axial with respect to the axis of the air inlet 16) of about 0.15 inches (0.381 cm) from the compressor 6. The second pressure sensor 56 is positioned at an axial distance (axial with respect to the axis of the air outlet 14) of about 0.15 inches (0.381 cm) from the compressor 6. However, depending upon the specific design of the turbocharger 2 (e.g., compressor 6), air inlet 16, air outlet 14, operating conditions, as well as the position of the pressure sensors, and other variables, the configuration of the sensors will vary. The first pressure sensor 54 can be positioned at any point along the length of the air inlet 16, and the second pressure sensor 56 can be positioned at any point along the length of the air outlet 14, whereat they provide information (e.g., a pressure signal) to the controller 26 that is utilized to determine the onset of surge. In certain embodiments, the sensors can be positioned less than or equal to about 12 inches, or more specifically, less than or equal to about 6 inches, or even more specifically, less than or equal to about 1 inch from the compressor 6.
In the present embodiment, the controller 26 is capable of receiving an analog signal (e.g., millivolts) from each of the pressure sensors and evaluating each of the signals for surge precursors. To be more specific, frequencies of the signals that are less than or equal to about 10 Hertz (Hz) can be evaluated for amplitude peaks that are indicative of the onset of surging. For example, referring now to
Referring now to
Referring now to
Lastly, referring now to
From
In addition, it is to be apparent that although the turbocharger 2 and control system 20 illustrated in
To detect surge precursors using pressure measurement signals, a wavelet function processor is employed to dissect the signal into discrete frequency ranges (bands) using a wavelet transform function. The wavelet function processor can be operably connected to the controller 20 or part thereof. This advantageously allows for the monitoring of discrete frequency bands of interest for surge precursors (e.g., changes in signal amplitudes).
Although not bound by theory, wavelet transforms are especially useful in this application as they are capable of extracting frequency information without losing time information. In addition, compared to Fourier transforms, wavelet transforms are especially effective at accounting for non-stationary signals having frequency transients, yield improved time-frequency resolution, and are computationally more efficient.
The controller 20 can employ any sampling rate for the information received from the sensors, however the rate is to be sufficient to adequately predict a surging event. In general, the frequency employed should be greater than about 0.01 Hz, such as greater than about 1.0 Hz, or greater than about 100.0 Hz. In one example, the controller can receive information at about 400 Hz.
Referring now to
Once the signal has been buffered, the conditioned signal (e.g., signal block data) is decomposed into several different frequency ranges using a wavelet function processor. The extracted signal (e.g., of the specific frequency range of interest, e.g. 0-12.5 Hz) is then further conditioned using a root-mean-square block wherein the square root of the mean of the squares of the specific frequency range values is calculated to produce a root mean squared value (RMS value). The RMS value is then passed through a moving average filter to give the final signal called as ‘final processed signal’.
The final processed signal for the specific frequency(ies) (e.g., a singular frequency or multiple frequencies of interest) is then evaluated by the controller 26 to determine if the turbocharger 2 is exhibiting signs of surge precursors. This can be determined utilizing any of the operating conditions measured as well as memory (e.g., a performance map, look-up table, data, algorithms, and so forth). For example, the final process signal can be evaluated for peaks having an amplitude greater than or equal to a specified limit, such as about 30 dB.
If the turbocharger 2 is not exhibiting signs of the onset of surge (e.g., surge precursors), the controller can continue to monitor the operating conditions and compare the operating conditions to memory as discussed above.
If the controller 26 determines the turbocharger 2 is exhibiting surge precursors, the next step of the method is initiated wherein the proximity of a surging event is determined. To be even more specific, the proximity of a surging event is a determination of when the turbocharger 2 will experience surge from the turbocharger's current point of operation. The proximity of a surging event can be determined utilizing any of the operating conditions measured as well as memory (e.g., a performance map, look-up table, data, algorithms, and so forth), and can be determined with respect to time or with respect to an operating condition. For example, the controller 26 can determine the turbocharger 2 will experience surge if the RPM of the turbocharger reaches a certain value under the current operating conditions.
In another embodiment, the controller 26 can determine the proximity of a surging event by determining the current amplitude of a peak and the current rate of change in the peak's amplitude. Thereafter, the amplitude of the peak and the current rate of change in the peak's amplitude can be compared to a look up table to determine the proximity of the surging event via extrapolation. In yet another embodiment, the controller 26 can utilize the current operating pressures to locate a specific algorithm within the memory that can be employed to calculate a point of operation whereat surging will occur.
Once the controller 26 has determined if the turbocharger 2 is exhibiting surge precursors, and has determined the proximity of surge, the controller can then determine if an action is desired. The action to be taken can be for any reason, such as to avoid surge or to increase the operating efficiency of the turbocharger 2. If the action is desired, the action is performed.
As discussed prior, in one embodiment, the controller 26 can first determine if an action is desired to avoid surging by evaluating the proximity information determined in the prior step. If an action is not desired to avoid surging, the controller 26 can then evaluate if an action is desired to increase efficiency. To do so, the controller 26 can compare the temperatures supplied by the first sensor 22 and the second sensor 24, and the temperature differential therebetween, to a look-up table, wherein the look-up table provides information regarding the turbochargers efficiency to the controller 26. Based on the efficiency information, the controller 26 compares the turbochargers current efficiency to a minimum value. If above the minimum value, the controller determines no action is to be taken except to continue to monitor the operating conditions of the turbocharger 2. In another example, the controller 26 can determine, that although the turbocharger 2 is operating at an acceptable efficiency, the proximity of a surging event is unacceptable, and therefore an action is performed to avoid surge.
As discussed earlier, the control system 20 can comprise an operational device. One exemplary device is a backpressure valve disposed in fluid communication with the air outlet 14 wherein the backpressure valve is capable of adjusting the pressure ratio of the turbocharger 2 to avoid surging (not shown). The controller 26 can also or alternatively, be capable of controlling the operation of a pressure recycle circuit wherein a portion of the high pressure air from the air outlet 14 can be directed into the air inlet 16 to avoid surging. It is to be understood that additional devices and systems can be employed to avoid surging and/or adjust the operating conditions of the turbocharger (e.g., open a bypass valve, increase air outlet 14 flow, increase exhaust inlet 8 flow, and so forth).
The methods disclosed above can be embodied in the form of computer-implemented processes. These methods can also be embodied in the form of computer program code embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer or controller, the device executing the code is an apparatus for practicing the method. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits.
To be specific, the technical effect of the actions of the controller 26 is the monitoring and/or control of a turbocharger and/or the determination of the presence of surge precursors and/or the determination of the proximity of a surging event. When these capabilities are embodied in software, firmware, hardware or some combination thereof, the embodiment can be an individual article for sale or included as a part of a computer system or sold separately.
The flow diagrams depicted herein are examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from this disclosures spirit. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified.
The turbocharger systems disclosed herein provide several notable benefits. Firstly, turbocharger systems are disclosed that can determine the presence of surge precursors. Second, using operating information regarding the surge precursors, the turbocharger systems can determine the proximity of a surging event. This enables the controller to determine if an action is required to avoid a surging event or adjust the operating conditions closer to the surge boundary to achieve greater operating efficiency. Third, turbocharger systems are disclosed that employ pressure and/or temperature sensors (e.g., operating condition(s) can be determined by monitoring (i) a temperature differential in an air inlet connected in fluid communication to the compressor, and/or (ii) a pressure), providing flexibility in the design and configuration of the turbocharger system. For example, in many cases thermocouples are less expensive than pressure transducers. Finally, methods for operating turbochargers are disclosed that provide for efficient operation and extended service life due to avoiding surging events.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs. Reference throughout the specification to “one embodiment”, “another embodiment”, “an embodiment”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the element(s) are not necessarily all referring to the same embodiment, and particular elements may be combined in any suitable manner in the various embodiments. The terms “first”, “second”, and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item, and the terms “front”, “back”, “bottom”, and/or “top”, unless otherwise noted, are merely used for convenience of description, and are not limited to any one position or spatial orientation. If ranges are disclosed, the endpoints of all ranges directed to the same component or property are inclusive and independently combinable (e.g., ranges of “up to about 25 wt. %, or, more specifically, about 5 wt. % to about 20 wt. %,” is inclusive of the endpoints and all intermediate values of the ranges of “about 5 wt. % to about 25 wt. %,” etc.). The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., “the colorant(s)”, includes one or more colorants). Furthermore, as used herein, “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.
While the turbocharger control systems described are in reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the turbocharger control systems without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
