Thermal measuring and testing – Temperature measurement – Nonelectrical – nonmagnetic – or nonmechanical temperature...
Patent
1997-01-06
1998-09-08
Bennett, G. Bradley
Thermal measuring and testing
Temperature measurement
Nonelectrical, nonmagnetic, or nonmechanical temperature...
374121, G01B 902
Patent
active
058036075
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to sensors and associated apparatus and methods for high bandwidth, unsteady gas temperature measurement, based on interferometry using optical fibres. The invention is particularly concerned with the measurement of gas total temperature measurement in turbomachinery, most particularly in gas turbines and compressors as used, for example, in aeroengines.
2. Discussion of Prior Art
Aeroengine development continues to demand exacting improvements in compressor performance. Military aeroengines require increased thrust-to-weight ratio and decreased cost of ownership while maintaining adequate levels of stable operating range and efficiency. Improving efficiency is the primary aim of civil engine development. These requirements are responsible for generic trends in modern compressor design. Fewer rotor stages tend to be used, which increases the aerodynamic stage loading. Blade rows tend to be spaced closer together which, coupled with the increased aerodynamic loading, increases the influence that each row exerts on neighbouring rows. There is also a tendency for the aspect ratio of the blades to be decreased which increases the complexity of the boundary layer flows on the blades, and on the end walls. The consequence of these trends is that the unsteady flow field within the compressor becomes more significant and needs to be taken into account during the design and development of future compressors.
In response to these trends, there is a growth in the attention being paid to unsteady blade row interaction in turbomachinery. However, because of the problems associated with taking unsteady aerodynamic measurements in high speed turbomachinery, there are few measurements in engine-relevant compressors and there is consequently a poor empirical understanding of the fundamental flow processes involved. Nevertheless, concerted effort since the mid-1980's has overcome many of the problems associated with taking wide bandwidth pressure measurements in high speed compressors and such sensors have been employed in engine-relevant machines. Unfortunately, the situation is less satisfactory when unsteady temperature measurements are considered. Both unsteady pressure and temperature measurements are required if the compressor efficiency and entropy flux are to be measured accurately. Further, it is recognised that the measurement systems used to derive steady state blade row performance do not respond properly to the highly pulsatile filed behind rotor rows. Therefore there is a need for pressure, and particularly temperature, measurement systems capable of resolving the fluctuating flow field so that more accurate steady-state measurements can be derived.
SUMMARY OF THE INVENTION
The invention thus relates to measurement apparatus and methods, including a measurement probe based on a fibre optics sensor, for use in measuring rapidly varying temperatures in such applications. The present disclosure includes the results of a demonstration of an embodiment of the probe in a continuous flow compressor test rig. Similar techniques may also be applied to the measurement of pressure at high bandwidth.
It is an object of the invention to provide an optical fibre based sensor allowing the measurement of unsteady temperature fluctuations in high speed compressors. Unsteady pressure measurements in such a compressor have revealed periodic and random flow effects. A corresponding measurement of unsteady temperature was sought in the same compressor, operating under the same conditions. For this purpose it was required that the optical fibre sensor have: features associated with blade passing frequencies of up to 12 kHz; between closely spaced compressor blade rows; and high-transonic Mach number flows laden with oil mist).
A gas temperature resolution of less that 1 K is desirable, with a sensor operating range up to 600 K.
Whilst the above mentioned performance parameters are desirable for typical turbomachinery applications of the inventio
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Barton James S
Chana Kamaljit S
Jones Julian D C
Kidd Stephen R
Bennett G. Bradley
The Secretary of State for Defence in Her Britannic Majesty's Go
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