Peter R.N. Childs

Review of Temperature Measurement

A variety of techniques are available enabling both invasive measurement, where the monitoring device is installed in the medium of interest, and noninvasive measurement where the monitoring system observes the medium of interest remotely. In this article we review the general techniques available, as well as specific instruments for particular applications. The issues of measurement criteria including accuracy, thermal disturbance and calibration are described. Based on the relative merits of different techniques, a guide for their selection is provided.

Air-Gap Convection in Rotating Electrical Machines

This paper reviews the convective heat transfer within the air gap of both cylindrical and disk geometry rotating electrical machines, including worked examples relevant to fractional horsepower electrical machines. Thermal analysis of electrical machines is important because torque density is limited by maximum temperature. Knowledge of surface convective heat transfer coefficients is necessary for accurate thermal modeling, for example, using lumped parameter models. There exists a wide body of relevant literature, but much of it has traditionally been in other application areas, dominated by mechanical engineers, such as gas turbine design. Particular attention is therefore given to the explanation of the relevant nondimensional parameters and to the presentation of measured convective heat transfer correlations for a wide variety of situations from laminar to turbulent flow at small and large gap sizes for both radial-flux and axial-flux electrical machines.

Heat Flux Measurement Techniques

Abstract Heat flux measurement is used in the field of fluid mechanics and heat transfer to quantify the transfer of heat within systems. Several techniques are in common use, including: differential temperature sensors such as thermopile, layered resistance temperature devices or thermocouples and Gardon gauges; calorimetric methods involving a heat balance analysis and transient monitoring of a representative temperature, using, for example, thin-film temperature sensors or temperature sensitive liquid crystals; energy supply or removal methods using, for example, a heater to generate a thermal balance; and, finally, by measurement of mass transfer which can be linked to heat transfer using the analogy between the two. No one method is suitable to all applications because of the differing considerations of accuracy, sensitivity, size, cost and robustness. Recent developments including the widespread availability and application of thin-film deposition techniques for metals and ceramics, allied with advances in microtechnology, have expanded the range of devices available for heat flux measurement. This paper reviews the various types of heat flux sensors available, as well as unique designs for specific applications. Critical to the use of a heat flux measurement technique is accurate calibration. Use of unmatched materials disturbs the local heat flux and also the local convective boundary layer, producing a potential error that must be compensated for. The various techniques in common use for calibration are described. A guide to the appropriate selection of a heat flux measurement technique is provided according to the demands of response, sensitivity, temperature of operation, heat flux intensity, manufacturing constraints, commercial availability, cost, thermal disturbance and acceleration capability for vibrating, rotating and reciprocating applications.

A Review of Forced Convective Heat Transfer in Stationary and Rotating Annuli

The study of heat transfer by forced convection in annular passages is of interest across the range of process and aeronautical industries, for example from annular heat exchangers to the various configurations of annuli found in turbomachinery. The aim of this paper is to review relevant experimental, numerical and analytical research of heat transfer in both stationary and rotating annuli, with an emphasis on presenting useful information for designers. The geometries considered are the stationary annulus with superposed axial throughflow and the rotating annulus with rotation of either the inner or outer cylinder (both with and without throughflow). The work presented covers laminar and turbulent flows as well as flow regimes where transition occurs or vortex flows are present.

Advances in temperature measurement

The need for temperature measurement is ever present in science and industry from requirements for monitoring processes, in the management of quality control and research. Temperature can be measured by means of direct contact between the medium of interest and the measuring device or by remote observation of a temperature-dependent parameter. The range of devices with which temperature can be measured is extensive, not surprisingly because most physical parameters exhibit a dependency on temperature. In recent years the dominant position of liquid-in-glass and bimetallic thermometers, thermocouples, and resistant temperature detectors has been challenged as the common choice for temperature measurement by infrared thermometers and an increasing array of other noninvasive techniques. This chapter outlines the principal techniques available for the measurement of temperature, describing the physical phenomena exploited, the temperature range of use, equipment required, and typical applications. Recent trends in requirements for traceability and quantification of uncertainty, as well as developments in the areas of instrumentation capability and technique, are described.

A psychological ownership approach to designing object attachment

The mental state in which an individual claims an object as theirs is called psychological ownership. Psychological ownership is associated with motives, routes, affordances, and outcomes directly linked to attachment. This research introduces psychological ownership in the context of designing object attachment and identifies affordance principles that help facilitate it. A framework presenting the motives for and routes to psychological ownership is proposed to provide a holistic understanding of object attachment. In the framework each route to psychological ownership, that is, control, intimate knowledge, and self-investment, has a corresponding class of affordances. Overall a total of 16 affordance principles are identified through contextual inquiry with 4 objects (a car, a mobile phone, a pair of shoes, and a park bench). Previous studies have identified various elements of this framework but have fallen short of clearly defining and relating the motives, routes, and affordances to psychological ownership identified here. These affordance principles are readily mapped to experience design models and provide a practical resource for designers. Together, the framework and the affordances inform design decisions and move towards a prescriptive design method for facilitating object attachment.

Sustainability by design: a reflection on the suitability of pedagogic practice in design and engineering courses in the teaching of sustainable design

Courses in product design are offered within the United Kingdom at the University of Brighton and the University of Sussex and in both cases are run within engineering departments alongside traditional engineering courses. This paper outlines some of the intrinsic pedagogic practices that are employed by these, and other, design courses. It highlights why creativity is a central tenet within these courses, which has underpinned the successful bid by the universities to jointly become the UK Centre of Excellence in Teaching and Learning in Creativity (CETL in C), and why, in particular, creativity is a key requirement in sustainable design. It supposes why these practices might, and should, offer a suitable role model for more traditional engineering courses.

ICAS-GT: A European Collaborative Research Programme on Internal Cooling Air Systems for Gas Turbines

The Internal Cooling Air Systems for Gas Turbines (ICAS-GT) research programme, sponsored by the European Commission, ran from January 1998 to December 2000, and was undertaken by a consortium of ten gas turbine manufacturing companies and four universities. Research was concentrated in five discrete but related areas of the air system including turbine rim seals, rotating cavity flow and heat transfer, and turbine pre-swirl system effectiveness. In each case, experiments were conducted to extend the database of pressure, temperature, flow and heat transfer measurements to engine representative non-dimensional conditions. The data was used to develop correlations, and to validate CFD and FE calculation methods, for internal fluid flow and heat transfer. This paper summarises the outcome of the project by presenting a sample of experimental results from each technical work package. Examples of the associated CFD calculations are included to illustrate the progress made in developing validated tools for predicting rotating cavity flow and heat transfer over an engine representative range of flow conditions.Copyright

Experimental Investigation of Turbine Stator Well Rim Seal, Re-Ingestion and Interstage Seal Flows Using Gas Concentration Techniques and Displacement Measurements

Gas turbine engine performance requires effective and reliable internal cooling over the duty cycle of the engine. Life predictions for rotating components subject to the main gas path temperatures are vital. This demands increased precision in the specification of the internal air system flows which provide turbine stator well cooling and sealing. This in turn requires detailed knowledge of the flow rates through rim seals and interstage labyrinth seals. Knowledge of seal movement and clearances at operating temperatures is of great importance when prescribing these flows. A test facility has been developed at the University of Sussex, incorporating a two stage turbine rated at 400 kW with an individual stage pressure ratio of 1.7:1. The mechanical design of the test facility allows internal cooling geometry to be rapidly re-configured, while cooling flow rates of between 0.71 CW, ENT and 1.46 CW, ENT, may be set to allow ingress or egress dominated cavity flows. The main annulus and cavity conditions correspond to in cavity rotational Reynolds numbers of 1.71 × 106 < Reϕ <1.93 × 106. Displacement sensors have been used to establish hot running seal clearances over a range of stator well flow conditions, allowing realistic flow rates to be calculated. Additionally, gas seeding techniques have been developed, where stator well and main annulus flow interactions are evaluated by measuring changes in gas concentration. Experiments have been performed which allow rim seal and re-ingestion flows to be quantified. It will be shown that this work develops the measurement of stator well cooling flows and provides data suitable for the validation of improved thermo-mechanical and CFD codes, beneficial to the engine design process.

Windage sources in smooth-walled rotating disc systems:

Abstract This article presents experimental data and an associated correlation for the windage resulting from a disc rotating in air, characteristic of gas turbine engines and relevant to some electrical machine applications. A test rig has been developed that uses an electric motor to drive a smooth bladeless rotor inside an enclosed pressurized housing. The rig has the capability of reaching rotational and throughflow Reynolds numbers representative of a modern gas turbine. A moment coefficient has been used to allow a non-dimensional windage torque parameter to be calculated and an agreement with the relevant data in the literature has been found within 10 per cent. Infrared measurements have been performed that allow direct surface temperatures of the rotating disc to be obtained. Laser Doppler anemometry measurements have been made that allow velocities in the flow field of the rotor—stator cavity to be examined and tangential velocities corresponding to rotationally and radially dominated flow conditions are shown. The importance of the flow regime in relation to the resulting windage has been identified and in particular it is noted that windage is a function not only of the ratio of rotational and radial flow dominance as defined by the turbulence parameter, but also for a given value of the turbulence parameter, the magnitude of the rotationally induced and superimposed flows. The experiments extend the range of data available for windage in rotor—stator systems and have been used to produce a correlation suitable for applications operating up to the range of Reψ=107.