Electricity: measuring and testing – A material property using electrostatic phenomenon – In a liquid
Patent
1995-09-20
1998-01-06
Wieder, Kenneth A.
Electricity: measuring and testing
A material property using electrostatic phenomenon
In a liquid
324452, 324457, 324553, G01N 2760
Patent
active
057059306
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a sensor and particularly, but not exclusively, to a sensor for sensing electrostatic charge in the gas path of a gas turbine engine.
It has been known for some time that it is possible to detect the presence of electrostatic charge in the gas path of a gas turbine engine. Particles of debris naturally carry an electrostatic charge and by detecting such charge it is possible to monitor the passage of debris through an engine. Sensors can be placed at several positions along the gas path. For example, a sensor can be used at the air inlet to an engine in order to monitor debris ingested into the engine and another sensor can be used at the exhaust to monitor debris in the exhaust gases. Signals obtained from such sensors can be analysed for example by determining whether or not debris has been generated internally by, say, a blade rubbing against a fixed portion of the engine.
The environment of a gas turbine engine is hostile, particularly in parts of the engine after the combustion chamber where exhaust gases reach very high temperatures. Clearly, a sensor in this part of the engine must be capable of surviving in the hostile environment if it is to be of any use. One form of sensor that has hitherto been used comprises conductive material sprayed onto the inside of the engine body to form a loop sensor around the gas flow path. Such sensors are applied using plasma spraying techniques. Sprayed on sensors are difficult to connect to electrically and, using presently available materials, tend to fall off into the gas flow path thereby adding to the debris in the engine. Another loop sensor is disclosed in a European patent application published as EP-A-0 120 087. This sensor comprises a conductive loop placed behind the engine and is therefore only suitable for use in ground tests and is not suitable for use in continuously monitoring an engine when the engine is in use in say an aircraft. Loop sensors can detect the passage of charge at any point across the gas flow path but they also have a wide angle of view along the gas path. It is important to be able to see across the whole of the gas flow path in order that all debris therein can be detected but advantageously the view along the gas path should be narrow so that the sensor only sees a thin cross section of the path. A narrow field of view helps to reduce noise in signals produced by the sensor.
Another form of sensor that has hitherto been used comprises a probe mounted in an insulating body which can be fitted to a convenient location on the body of an engine. These sensors sense electrostatic charge passing a point, i.e. the point at which the sensor is mounted, in the gas path. The sensors generally have a wide conical field of view and often two or more sensors are required to achieve a field of view across the whole of the gas path. Thus, point sensors also suffer from the disadvantage that they have a wide field of view along the gas path. Point sensors can be designed to conform to the surface of the engine body thereby significantly reducing the unpredictable effects that could occur if the sensors were to intrude into the gas flow path. This enables point sensors to be retrofitted to existing engines without the need for extensive recalculation of gas flow behaviour to take account of any intrusion into the gas path. In practice point sensors, be they gas path intrusive or conformal, have a finite sensing area of a few square centimeters. For this reason conformal point sensors are also known as button sensors. Points sensors are thus not insubstantial in size. Therefore, retrofitting of point sensors requires the cutting of mounting holes in the body of the engine, thereby necessitating the recalculation of stresses within the engine to ensure that the engine will not be damaged by the retrofitting of the sensors. Clearly, this is undesirable but it is also very necessary because there are many designs of engine currently in service where debris sensing could be usefully employed for example in monitoring the heal
REFERENCES:
patent: 4222007 (1980-09-01), Comstock
patent: 4251775 (1981-02-01), Michel
patent: 4433298 (1984-02-01), Palm
patent: 4625176 (1986-11-01), Champion et al.
patent: 4642559 (1987-02-01), Slough
patent: 4760342 (1988-07-01), Conrads et al.
patent: 4875133 (1989-10-01), Kawamura
patent: 5596266 (1997-01-01), Mori et al.
Brown Glenn W.
Stewart Hughes Limited
Wieder Kenneth A.
LandOfFree
Gas path electrostatic sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas path electrostatic sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas path electrostatic sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2332381