Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings in which some but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
A turbocharged engine system 10 in accordance with one embodiment of the invention is schematically illustrated in
The compressor discharges the pressurized air through a discharge duct 30 that is connected to an air intake 32 of the engine. The pressurized air is mixed with fuel supplied through a fuel supply line 34 by a fuel controller 36.
The engine system includes an engine control unit (ECU) 40 that contains a microprocessor and memory. The ECU is operable to execute a set of programmed instructions stored in nonvolatile memory of the ECU, for controlling various components of the engine system to regulate the operation of the engine. The ECU receives data from various engine sensors (not shown) that sense temperatures, pressures, engine speed, and other parameters, and provides control signals to various engine components based in part on the received data. In particular, the ECU is connected by a communication line 42 to the engine fuel controller 36 for receiving data (e.g., fuel flow rate, fuel temperature, etc.), and for providing control signals to the fuel controller to regulate the fuel flow rate to the engine.
The engine system 10 further comprises at least one vibration sensor 50 arranged for detecting vibration of the turbocharger rotor. The vibration sensor can be of various types such as piezoelectric, capacitance, null-balance, strain gage, resonance beam, piezoresistive and magnetic induction. Vibration sensors can measure vibration along only one axis, or along two or three orthogonal axes simultaneously.
The force associated with the vibration (usually expressed in terms of the gravity or “G” force) is proportional to the amplitude A of the vibration and the square of the frequency F of the vibration, as follows:
G=kAF
2,
where k is a constant whose value is dependent on the particular characteristics of the system undergoing the vibration.
The “G” force represents the magnitude of the destructive force of the vibration. This force is not measured directly. Instead, the vibration sensor generally produces a signal indicative of the displacement of an element in the sensor. Based on the time-varying displacement, the velocity of the element's movement can be determined by taking the first time derivative of the displacement, and the acceleration of the element can be determined by taking the second time derivative of the displacement. Analysis of the time-varying output signal of the sensor can also yield the amplitude and frequency of displacement, which enables the calculation of the “G” force from the above equation.
The vibration sensor 50 is connected to the ECU 40 or to another controller that is integrated in the ECU or is a stand-alone unit separate from the ECU. In any event, the controller receives the output signal from the vibration sensor 50. Analysis of the time-varying output signal of the sensor to deduce the amplitude and frequency of displacement, and optionally the “G” force, can be performed in the controller based on known vibration analysis techniques. Alternatively, some vibration sensors can include onboard capabilities to perform such analysis and provide an output signal directly indicative of a parameter of interest such as “G” force. In one embodiment of the invention, the analysis is performed in real time, whether by the sensor or by the controller. This allows a virtually instantaneous indication of the “health” of the turbocharger rotor.
As noted, the conditions experienced by the bearing system for the turbocharger rotor are challenging. The bearing system, which typically is lubricated by oil from the engine's oil system, is susceptible to damage and failure from various causes, but chief among them are contaminated oil and foreign object damage to the compressor or turbine. Contaminated oil can cause rapid wear of the bearing surfaces and eventually lead to bearing failure. Foreign object damage to the compressor or turbine can cause rotor imbalance that likewise can lead to bearing failure.
Bearing wear generally occurs over time as opposed to suddenly, and is characterized by an increase in rotor vibration over time. If the bearing deterioration is allowed to continue long enough, the magnitude of the vibration (which can be characterized by the displacement amplitude A or the “G” force) can reach a destructive level at which a catastrophic failure of the bearings can occur. It is desired to be able to detect the deterioration process early on to allow maintenance personnel to investigate whether maintenance or replacement of the bearings may be indicated, and thereby to prevent such catastrophic failures.
Foreign object damage (FOD) can occur over time or suddenly, and thus can be characterized by an increase in vibration magnitude over time or a sudden increase in vibration. In either case, it is desired to be able to detect the increase in vibration magnitude early enough to allow investigation and possible maintenance or replacement actions to be taken before any catastrophic failure occurs.
In accordance with the invention, the controller or ECU 40 is operable to determine whether the vibration magnitude exceeds one or more predetermined limits, and to take predetermined actions when one or more limits are exceeded in order to prevent or substantially reduce the likelihood of a catastrophic failure of the turbocharger 20. With reference to
At step 104, the controller then determines whether the vibration magnitude V1B exceeds a predetermined second limit V2. In either step 100 or step 104, if the respective vibration limit is not exceeded, then the controller returns to the beginning at step 100 and the control loop is executed again at the next pass-through.
If the second limit V2 is exceeded at step 104, thus indicating a potential abnormal condition in the turbocharger, the controller at step 106 issues a command to the fuel controller for the engine to cause the fuel controller to place the engine in a predetermined safe operating mode selected to reduce the likelihood of turbocharger and engine damage from the abnormal condition. In particular, the controller can provide a control signal to the fuel controller to reduce the engine fuel flow rate from the rate in effect at the current time. The fuel flow rate can be reduced to a predetermined value that is irrespective of the rate in effect when the potential abnormal condition is detected. Alternatively, the fuel flow rate can be reduced by a predetermined percentage of the rate in effect when the potential abnormal condition is detected, or can be reduced to a rate that is some other function of the rate in effect when the potential abnormal condition is detected.
The limits V1, V2 are graduated, i.e., the magnitude of V1 is less than that of V2. The limit V1 can be selected to attempt to identify potential abnormal conditions that are not so severe as to warrant taking immediate action to protect the turbocharger. The limit V2 can be selected to identify abnormal conditions that are considered potentially catastrophic if the engine and turbocharger were allowed to continue to operate normally. It is also possible to employ only a single limit or to employ more than two graduated limits.
With reference again to
The engine system 10 can also include a data recording device 60 structured and arranged for recording the output signal of the vibration sensor 50 (and/or data derived from analysis of the output signal) as a function of time so as to produce a history of rotor vibration for predictive and/or diagnostic purposes. The recording device can be of various types, including but not limited to devices for recording data on magnetic recording media, devices for recording data on optical recording media, RAM devices, flash memory devices, and the like. As illustrated, the recording device can be integrated into the ECU 40. Alternatively, the recording device could be a stand-alone unit.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.