Fluid flow and heat transfer analysis of TEFC machine end regions using more realistic end-winding geometry

In this paper a typical small low voltage TEFC motor (output power ~10 kW) has been studied using computational fluid dynamics. The complexity of the end winding geometries, often consisting of several insulated copper strands bound together, provides a challenge to the modelling and analysis of heat transfer and fluid flow phenomena occurring in the end region which typically is an area of most interest for thermal management. Approximated geometries are usually employed in order to model the end windings to reduce analysis time and cost. This paper presents a comparison of two cases, a typical simplified geometry and a more realistic geometry of end windings and uses these cases to highlight the challenges and impact on predicted heat transfer. A comparison of the two models indicate that the different representations of end winding geometries can affect the heat dissipation rate through the outer housing by up to 45%

Numerical investigations of convective phenomena of oil impingement on end-windings

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer has been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, whilst ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure

Fluid flow and heat transfer analysis of TEFC machine end regions using more realistic end-winding geometry

In this paper a typical small low voltage TEFC motor (output power ~10 kW) has been studied using computational fluid dynamics. The complexity of the end winding geometries, often consisting of several insulated copper strands bound together, provides a challenge to the modelling and analysis of heat transfer and fluid flow phenomena occurring in the end region which typically is an area of most interest for thermal management. Approximated geometries are usually employed in order to model the end windings to reduce analysis time and cost. This paper presents a comparison of two cases, a typical simplified geometry and a more realistic geometry of end windings and uses these cases to highlight the challenges and impact on predicted heat transfer. A comparison of the two models indicate that the different representations of end winding geometries can affect the heat dissipation rate through the outer housing by up to 45%

Thermal and Electromagnetic Stator Vent Design Optimisation for Synchronous Generators

© 2020 Institute of Electrical and Electronics Engineers Inc.. All rights reserved. This paper deals with the stator cooling of an air-cooled, synchronous generator with a power rating of 400 kVA, which has been improved by adding two radial vents to the stator. To ensure an optimal vent design, a novel combined thermal and electromagnetic modelling approach is developed. A parametric 3D Conjugate Heat Transfer Computational Fluid Dynamics (CFD) model is used for the thermal modelling. An electromagnetic 2D Finite Element Analysis determined the impact that venting the stator has on the loss distribution. The models are coupled by deriving analytical correlations between the combined vent width and rotor copper, rotor iron and stator iron losses. These correlations are implemented into the optimisation procedure of the parametric CFD model. Five design parameters are optimised simultaneously with the aim of minimising the peak stator winding temperature. The modelling approach was validated experimentally by thermal, torque and mass flow measurements on the benchmark machine, as well as the newly designed prototype

Numerical investigations of convective phenomena of oil impingement on end-windings

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer has been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, whilst ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure

Computational fluid dynamics modelling of an entire synchronous generator for improved thermal management

This study is the first in a series dedicated to investigating the airflow and thermal management of electrical machines. Owing to the temperature dependent resistive losses in the machine's windings, any improvement in cooling provides a direct reduction in losses and an increase in efficiency. This study focuses on the airflow which is intrinsically linked to the thermal behaviour of the machine as well as the windage power consumed to drive the air through the machine. A full computational fluid dynamics (CFD) model has been used to analyse the airflow around all major components of the machine. Results have been experimentally validated and investigated. At synchronous speed the experimentally tested mass flow rate and windage torque were under predicted by 4% and 7%, respectively, by the CFD. A break-down of torque by component shows that the fan consumes approximately 87% of the windage torque

4MW Class High Power Density Generator for Future Hybrid-Electric Aircraft

This paper describes the underpinning research, development, construction and testing of a 4MW multi-three phase generator designed for a hybrid-electric aircraft propulsion system demonstrator. The aim of the work is to demonstrate gravimetric power densities around 20 kW/kg, as required for multi-MW aircraft propulsion systems. The key design choices, development procedures and trade-offs, together with the experimental testing of this electrical machine connected to an active rectifier are presented. A time-efficient analytical approach to the down-selection of various machine configurations, geometrical variables, different active and passive materials and different thermal management options is first presented. A detailed design approach based on 3D Finite Element Analysis (FEA) is then presented for the final design. Reduced power tests are carried out on a full scale 4 MW machine prototype, validating the proposed design. The experimental results are in good agreement with simulation and show significant progress in the field of high power density electrical machines at the targeted power rating

Research and Realization of High-Power Medium-Voltage Active Rectifier Concepts for Future Hybrid-Electric Aircraft Generation

This paper describes the research and development of a 3kV active rectifier for a 4MW aerospace generator drive system demonstrator. The converter is fed by a multi-phase high speed/high frequency, permanent magnet generator. The main aim of the work is to demonstrate for the first time the feasibility of a MW-class generator system meeting future hybrid-electric propulsion requirements. A concept with multiple and isolated three-phase systems feeding different power buses is proposed to meet the availability requirements. Multiple converters (one for each three-phase system) are connected in series and/or in parallel to achieve the rated power and DC link voltage. This paper describes the key design concepts and the development and testing of the converter to meet the challenging application requirements. Reduced power tests are carried out on a full scale 4 MW converter prototype, validating the proposed design. The work represents a step forward in terms of voltage, power, and output frequency, with respect to the state of the art

Disgust trumps lust:women’s disgust and attraction towards men is unaffected by sexual arousal

Mating is a double-edged sword. It can have great adaptive benefits, but also high costs, depending on the mate. Disgust is an avoidance reaction that serves the function of discouraging costly mating decisions, for example if the risk of pathogen transmission is high. It should, however, be temporarily inhibited in order to enable potentially adaptive mating. We therefore tested the hypothesis that sexual arousal inhibits disgust if a partner is attractive, but not if he is unattractive or shows signs of disease. In an online experiment, women rated their disgust towards anticipated behaviors with men depicted on photographs. Participants did so in a sexually aroused state and in a control state. The faces varied in attractiveness and the presence of disease cues (blemishes). We found that disease cues and attractiveness, but not sexual arousal, influenced disgust. The results suggest that women feel disgust at sexual contact with unattractive or diseased men independently of their sexual arousal

Largest ancient fortress of South-West Asia and the western world?:Recent fieldwork at Sasanian Qaleh Iraj at Pishva, Iran

The article presents recent works at Qale Iraj, near Varamin, Iran. My short contribution is on the Middle Persian ostraka found at the site