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SYSTEM AND METHOD FOR DETERMINING TORQUE ON A TURBINE SHAFT

IP.com Disclosure Number: IPCOM000192585D
Publication Date: 2010-Jan-25
Document File: 6 page(s) / 173K

Publishing Venue

The IP.com Prior Art Database

Abstract

A system and method for determining torque on a turbine shaft are disclosed. The disclosed method includes measuring the torque by utilizing the Moiré interference effect. The disclosed method utilizes two gratings to generate the Moiré interference pattern. Further, a spatial period of the interference pattern is utilized to determine an angular displacement and subsequently the torque applied to the shaft. The disclosed system measures the torque with more accuracy.

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RP13302

SYSTEM AND METHOD FOR DETERMINING TORQUE ON A TURBINE SHAFT

BRIEF ABSTRACT

    A system and method for determining torque on a turbine shaft are disclosed. The disclosed method includes measuring the torque by utilizing the Moiré interference effect. The disclosed method utilizes two gratings to generate the Moiré interference pattern. Further, a spatial period of the interference pattern is utilized to determine an angular displacement and subsequently the torque applied to the shaft. The disclosed system measures the torque with more accuracy.

KEYWORDS

    Torque, angular displacement, moiré interference effect, moiré interference pattern, grating, shaft, turbine, fringes

DETAILED DESCRIPTION

    Turbines are used, for example, in aircraft engines and as industrial gas turbines. Turbines efficiency is an important characteristic that is evaluated, at great expense, under operating conditions during turbine development. For such evaluations, temperatures and pressures at the turbine intake and turbine outlet are obtained and are averaged. The efficiency is inferred from these measurements and from further measured variables via an overall model of the

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RP13302

propulsion unit or the gas turbine. Differences in the temperature and pressure fields and further effects, some of which are difficult to estimate, typically result in uncertainties of .+/-.2% or more.

    Further, the power output by the turbine to the compressor via the shaft, which may be measured via the torque applied to the shaft, represents an additional independent variable which may be used to improve the efficiency determination. Torque is an important parameter monitored by pilots and engine operators to control aircraft or other engines and prevent damage to drive train components. Optical torque sensing methods are well suited for turbine applications as such methods enable shaft torque/power measurements at shaft sections where temperatures can be high.

    In general, torsion angle is measured over a finite part of the shaft, i.e., angular displacement or torsion strain is measured locally on the shaft surface in order to determine the torque on the shaft. Torque relates to the measured variable via the shear modulus and the geometry of the shaft. Typically, torque sensors which are based on the torsion angle measure the twist in a drive shaft within the engine. However, accuracy of such torque measurements is affected by the shaft material properties, the temperature of the shaft, the frictional components that support the shaft, and the torsion creep of the shaft itself. In addition, deficiencies in the accuracy, resolution, environmental response of the transducer, signal conditioning, and computations have a large effect on the measurement accuracy.

    In one conventional torsion angle based sensing technique, time delay between two...