Fan Stall Detection System
A system for detecting onset of a stall in a rotor is disclosed, the system comprising a sensor located on a static component spaced radially outwardly and apart from tips of a row of blades arranged circumferentially on the rotor wherein the sensor is capable of generating an input signal corresponding to a flow parameter at a location near the tip of a blade, a control system capable of generating a rotor speed signal, and a correlation processor capable of receiving the input signal and the rotor speed signal wherein the correlation processor generates a stability correlation signal.
This invention relates generally to gas turbine engines, and, more specifically, to a system for detection of a stall in a compression system therein, such as a fan.
In a turbofan aircraft gas turbine engine, air is pressurized in a compression system, comprising a fan module, a booster module and a compression module during operation. In large turbo fan engines, the air passing through the fan module is mostly passed into a by-pass stream and used for generating the bulk of the thrust needed for propelling an aircraft in flight. The air channeled through the booster module and compression module is mixed with fuel in a combustor and ignited, generating hot combustion gases which flow through turbine stages that extract energy therefrom for powering the fan, booster and compressor rotors. The fan, booster and compressor modules have a series of rotor stages and stator stages. The fan and booster rotors are typically driven by a low pressure turbine and the compressor rotor is driven by a high pressure turbine. The fan and booster rotors are aerodynamically coupled to the compressor rotor although these normally operate at different mechanical speeds.
Operability in a wide range of operating conditions is a fundamental requirement in the design of compression systems, such as fans, boosters and compressors. Modern developments in advanced aircrafts have required the use of engines buried within the airframe, with air flowing into the engines through inlets that have unique geometries that cause severe distortions in the inlet airflow. Some of these engines may also have a fixed area exhaust nozzle, which limits the operability of these engines. Fundamental in the design of these compression systems is efficiency in compressing the air with sufficient stall margin over the entire flight envelope of operation from takeoff, cruise, and landing. However, compression efficiency and stall margin are normally inversely related with increasing efficiency typically corresponding with a decrease in stall margin. The conflicting requirements of stall margin and efficiency are particularly demanding in high performance jet engines that operate under challenging operating conditions such as severe inlet distortions, fixed area nozzles and increased auxiliary power extractions, while still requiring high a level of stability margin throughout the flight envelope.
Stalls are commonly caused by flow breakdowns at the tip of the rotor blades of compression systems such as fans, compressors and boosters. In gas turbine engine compression system rotors, there are tip clearances between rotating blade tips and a stationary casing or shroud that surrounds the blade tips. During the engine operation, air leaks from the pressure side of a blade through the tip clearance toward the suction side. These leakage flows may cause vortices to form at the tip region of the blade. A tip vortex can grow and spread when there are severe inlet distortions in the air flowing into compression system or when the engine is throttled and lead to a compressor stall and cause significant operability problems and performance losses.
Accordingly, it would be desirable to have the ability to measure and control dynamic processes such as flow instabilities in a fan. It would be desirable to have a system that can measure an engine parameter related to the onset of flow instabilities, such as the dynamic pressure near the blade tips, and process the measured data to predict the onset of stall in a stage of a compression system, such as a multistage fan. It would also be desirable to have a system to mitigate compression system stalls based on the measurement system output, for certain flight maneuvers at critical points in the flight envelope, allowing the maneuvers to be completed without stall or surge.
BRIEF DESCRIPTION OF THE INVENTIONThe above-mentioned need or needs may be met by exemplary embodiments which provide a system for detecting onset of a stall in a rotor, the system comprising a sensor located on a static component spaced radially outwardly and apart from tips of a row of blades arranged circumferentially on the rotor wherein the sensor is capable of generating an input signal corresponding to a flow parameter at a location near the tip of a blade, a control system capable of generating a rotor speed signal, and a correlation processor capable of receiving the input signal and the rotor speed signal wherein the correlation processor generates a stability correlation signal.
In another embodiment, a system for detecting onset of a stall in a multi-stage fan rotor comprises a pressure sensor located on a casing surrounding tips of a row of fan blades wherein the pressure sensor is capable of generating an input signal corresponding to the dynamic pressure at a location near the fan blade tip.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, however, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:
Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,
The fan section 12 that pressurizes the air flowing through it is axisymmetrical about the longitudinal centerline axis 8. The fan section 12 includes a plurality of inlet guide vanes (IGV) 30 and a plurality of stator vanes 31 arranged in a circumferential direction around the longitudinal centerline axis 8. The multiple fan rotor stages 12 of the fan section 12 have corresponding fan rotor blades 40a, 40b, 40c extending radially outwardly from corresponding rotor hubs 39a, 39b, 39c in the form of separate disks, or integral blisks, or annular drums in any conventional manner.
Cooperating with a fan rotor stage 12a, 12b, 12c is a corresponding stator stage comprising a plurality of circumferentially spaced apart stator vanes 31a, 31b, 31c. The arrangement of stator vanes and rotor blades is shown in
Operating map of an exemplary compression system, such as the fan section 12 in the exemplary gas turbine engine 10 is shown in
Stalls in fan rotors due to inlet flow distortions, and stalls in other compression systems that are throttled, are known to be caused by a breakdown of flow in the tip region 52 of rotors, such as the fan rotors 12a, 12b, 12c shown in
The ability to control a dynamic process, such as a flow instability in a compression system, requires a measurement of a characteristic of the process using a continuous measurement method or using samples of sufficient number of discrete measurements. In order to mitigate fan stalls for certain flight maneuvers at critical points in the flight envelope where the stability margin is small or negative, a flow parameter in the engine is first measured that can be used directly or, with some additional processing, to predict the onset of stall of a stage of a multistage fan shown in
In the exemplary embodiment shown in
During engine operation, there is an effective clearance 48 between the fan blade tip and the casing 50 or the shroud 51 (see
The flow parameter measurement from the sensor 502 generates a signal that is used as an input signal 504 by a correlation processor 510. The correlation processor 510 also receives as input a fan rotor speed signal 506 corresponding to the rotational speed of the fan rotor 12a, 12b, 12c, as shown in
The correlation processor 510 receives the input signal 504 from the sensor 502 and the rotor speed signal 506 from the control system 74 and generates a stability correlation signal 512 in real time using conventional numerical methods. Auto correlation methods available in the published literature may be used. In the exemplary embodiments shown herein, the correlation processor 510 algorithm uses the existing speed signal from the engine control for cycle synchronization. The correlation measure is computed for individual pressure transducers over rotor blade tips. The auto-correlation system in the exemplary embodiments described herein sampled a signal from a pressure sensor 502 at a frequency of 200 KHz. This relatively high value of sampling frequency ensures that the data is sampled at a rate at least ten times the fan blade 40 passage frequency. A window of seventy two samples was used to calculate the auto-correlation showing a value of near unity along the operating line 116 and dropping towards zero when the operation approached the stall/surge line 112 (see
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Claims
1. A system for detecting onset of a stall in a rotor, the system comprising:
- a sensor located on a static component spaced radially outwardly and apart from tips of a row of blades arranged circumferentially on the rotor wherein the sensor is capable of generating an input signal corresponding to a flow parameter at a location near the tip of a blade;
- a control system capable of generating a rotor speed signal; and
- a correlation processor capable of receiving the input signal and the rotor speed signal wherein the correlation processor generates a stability correlation signal.
2. A system according to claim 1 further comprising:
- a plurality of sensors arranged on the static component spaced radially outwardly and apart from tips of the row of blades.
3. A system according to claim 2 wherein the sensor is a pressure sensor.
4. A system according to claim 2 wherein the sensor is a pressure sensor capable of generating a pressure signal corresponding to the dynamic pressure at a location near the blade tip.
5. A system according to claim 1 further comprising:
- a plurality of sensors arranged circumferentially on the static component around an axis of rotation of the rotor and spaced radially outwardly and apart from tips of the row of blades.
6. A system according to claim 2 wherein the static component is a casing.
7. A system according to claim 2 wherein the static component is a shroud.
8. A system according to claim 1 wherein the rotor comprises a plurality of fan rotors.
9. A system according to claim 1 wherein the sensor is located at a location on the static structure corresponding to the mid-chord of a blade.
10. A system according to claim 1 wherein the sensor is located at a location on the static structure corresponding to the lead edge of a blade.
11. A system for detecting onset of a stall in a fan rotor comprising:
- a pressure sensor located on a static component surrounding tips of a row of fan blades wherein the pressure sensor is capable of generating an input signal corresponding to the dynamic pressure at a location near the blade tip;
- a control system capable of generating a fan rotor speed signal; and
- a correlation processor capable of receiving the input signal and the fan speed signal wherein the correlation processor generates a stability correlation signal.
12. A system according to claim 11 further comprising a plurality of fan rotors wherein a plurality pressure sensors are located on the static component surrounding tips of a row of fan blades of at least two fan rotors.
13. A system according to claim 11 further comprising a plurality of sensors arranged circumferentially on the static component around an axis of rotation of the rotor and spaced radially outwardly and apart from tips of the row of fan blades.
14. A system according to claim 11 wherein a fan blade tip operates at a supersonic speed during the generation of the pressure signal.
15. A system according to claim 11 wherein the correlation processor receives the input signal from a plurality of pressure sensors and the rotor speed signal to generate a correlation signal.
16. A system according to claim 11 wherein the correlation processor generates a correlation signal based on the input signal from a plurality of pressure sensors and the rotor speed signal.
17. A system according to claim 11 wherein the correlation processor generates a correlation signal based on the input signal from pressure sensors located on the static component surrounding tips of a row of fan blades of at least two fan rotors.
18. A system according to claim 11 wherein the static component is a casing.
19. A system according to claim 11 wherein the static component is a shroud.
20. A system according to claim 11 wherein the sensor is located at a location on the static structure corresponding to the mid-chord of a fan blade.
21. A system according to claim 11 wherein the sensor is located at a location on the static structure corresponding to the leading edge of a fan blade.
Type: Application
Filed: Dec 28, 2007
Publication Date: Nov 11, 2010
Inventors: Aspi Rustom Wadia (Loveland, OH), Seyed Gholamali Saddoughi (Clifton Park, NY), Clark Leonard Applegate (West Chester, OH)
Application Number: 11/966,242
International Classification: F04D 29/00 (20060101);