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This paper proposes a new construction with a heat sink integrated into the concentrated wound coils of an axial flux, direct liquid cooled electrical machine. A preliminary assessment of the effectiveness of the heat sink and its position is made using computational fluid dynamics. Lumped-parameter thermal models are also developed, thus allowing accurate comparison of the thermal profile of the two constructions. Following experimental calibration of the model and thermal validation, the temperature profile of the new construction is compared to that from a traditional concentrated wound coil. The model is then used to estimate the effect of the new construction on the current density of the stator windings. The paper demonstrates that for an axial flux motor run at a typical operating point of 300 Nm and 1500 rpm, the maximum temperature is reduced by 87 K. The current density can be increased by 140% before the limiting maximum coil temperature is achieved.
Robert Camilleri; Malcolm McCulloch. Integrating a Heat Sink into Concentrated Wound Coils to Improve the Current Density of an Axial Flux, Direct Liquid Cooled Electrical Machine with Segmented Stator. Energies 2021, 14, 3619 .
AMA StyleRobert Camilleri, Malcolm McCulloch. Integrating a Heat Sink into Concentrated Wound Coils to Improve the Current Density of an Axial Flux, Direct Liquid Cooled Electrical Machine with Segmented Stator. Energies. 2021; 14 (12):3619.
Chicago/Turabian StyleRobert Camilleri; Malcolm McCulloch. 2021. "Integrating a Heat Sink into Concentrated Wound Coils to Improve the Current Density of an Axial Flux, Direct Liquid Cooled Electrical Machine with Segmented Stator." Energies 14, no. 12: 3619.
This paper presents a new approach in performing CFD modelling for electrical machine stator windings. Thermal modelling of the stator windings is important as the winding insulation is rated to a maximum operating temperature which limits the machine life or the torque ratings.
Robert Camilleri. CFD Modelling and Experimental Calibration of Concentrated Windings in a Direct Oil-Cooled Segmented Stator. Advances in Heat Transfer and Thermal Engineering 2021, 433 -437.
AMA StyleRobert Camilleri. CFD Modelling and Experimental Calibration of Concentrated Windings in a Direct Oil-Cooled Segmented Stator. Advances in Heat Transfer and Thermal Engineering. 2021; ():433-437.
Chicago/Turabian StyleRobert Camilleri. 2021. "CFD Modelling and Experimental Calibration of Concentrated Windings in a Direct Oil-Cooled Segmented Stator." Advances in Heat Transfer and Thermal Engineering , no. : 433-437.
This paper re-evaluates flat windings to improve the current density of concentrated windings. The paper produces finite element and lumped parameter thermal models to compare the thermal profile of the new flat winding construction with traditional concentrated windings of square cross-sectional area. An experimental setup is developed to validate the models which are then used to establish the thermal profile and current density of the two constructions. Traditional concentrated windings are shown to have a number of thermal resistances across their inter winding layers. A hot spot temperature is therefore produced at the winding with the longest thermal path. Flat windings as proposed here eliminates this problem, leading to lower temperatures. As a result, higher current can be injected before the maximum allowed temperature is reached. The paper demonstrates that for a typical motor operating point of 300 Nm and 1500 rpm the maximum temperature is reduced by 97 K. For the same maximum temperature, the current density can be increased between 130-150%.
Robert Camilleri; Malcolm D. McCulloch. Assessing the Temperature and Current Density of Flat Winding Coils for Concentrated Windings Within a Segmented Stator Machine. IEEE Transactions on Industry Applications 2021, 57, 2440 -2448.
AMA StyleRobert Camilleri, Malcolm D. McCulloch. Assessing the Temperature and Current Density of Flat Winding Coils for Concentrated Windings Within a Segmented Stator Machine. IEEE Transactions on Industry Applications. 2021; 57 (3):2440-2448.
Chicago/Turabian StyleRobert Camilleri; Malcolm D. McCulloch. 2021. "Assessing the Temperature and Current Density of Flat Winding Coils for Concentrated Windings Within a Segmented Stator Machine." IEEE Transactions on Industry Applications 57, no. 3: 2440-2448.
This paper presents the prediction of the heat transfer coefficient (HTC) in a direct oil cooled battery packs. The HTC is a critical parameter which is required for accurate thermal modelling of the battery pack and a precise thermal management system. The paper investigates direct oil cooling on cylindrical 18650 type battery cells. To increase the volumetric efficiency and energy density of the pack, the flow orientation is turned by 90° such that the coolant flows along the length of the cells, through the gaps formed between closely packed in-line cylindrical cells. The paper finds that direct oil cooling suffers from a large entry length during which the boundary layer is still developing. This requires correlations for developing flows to be used. When compared to CFD results, the Seider Tate equation was found to be within 8% at 100 <; Re <; 140. This however produces over prediction of around 60% at 100 <; Re. In this regime, the turbulent equation was found to perform better, most likely due to similarities in boundary layer at this early stage.
Robert Camilleri; Mahmoud Sawani. Prediction of the Heat Transfer Coefficient in Direct Oil Cooling of Lithium-Ion Batteries. 2018 5th International Symposium on Environment-Friendly Energies and Applications (EFEA) 2018, 1 -6.
AMA StyleRobert Camilleri, Mahmoud Sawani. Prediction of the Heat Transfer Coefficient in Direct Oil Cooling of Lithium-Ion Batteries. 2018 5th International Symposium on Environment-Friendly Energies and Applications (EFEA). 2018; ():1-6.
Chicago/Turabian StyleRobert Camilleri; Mahmoud Sawani. 2018. "Prediction of the Heat Transfer Coefficient in Direct Oil Cooling of Lithium-Ion Batteries." 2018 5th International Symposium on Environment-Friendly Energies and Applications (EFEA) , no. : 1-6.
This paper proposes a new flat winding construction for use in a direct liquid cooled segmented stator. Following a demonstration of how the conductivity across the windings limits further increasing in current density, the paper proposes a new construction using flat windings to replace traditional concentrated windings. The paper addresses some of the more practical challenges with the manufacturing of this type of windings. A thermal model is developed and used to demonstrate that the new flat windings construction offers a reduction in maximum winding temperature by approximately 97 °C, for a typical operating point of 300 Nm and 1500 rpm of the YASA machine. The lower operating temperature offers an improvement in the lifetime of the machine. Alternatively, for the same maximum temperature, the flat windings construction offers a 35% increase in current density.
R. Camilleri; M.D. McCulloch. A New Flat Winding Construction for Direct Liquid Cooled Axial Flux Machine with Segmented Stators. 2018 XIII International Conference on Electrical Machines (ICEM) 2018, 2416 -2422.
AMA StyleR. Camilleri, M.D. McCulloch. A New Flat Winding Construction for Direct Liquid Cooled Axial Flux Machine with Segmented Stators. 2018 XIII International Conference on Electrical Machines (ICEM). 2018; ():2416-2422.
Chicago/Turabian StyleR. Camilleri; M.D. McCulloch. 2018. "A New Flat Winding Construction for Direct Liquid Cooled Axial Flux Machine with Segmented Stators." 2018 XIII International Conference on Electrical Machines (ICEM) , no. : 2416-2422.
The heat transfer coefficient (HTC) is a critical parameter that is required for accurate thermal modeling of electrical machines. This is often achieved from empirical correlations of ideal geometries or computational fluid dynamics (CFD) simulations. This paper presents a novel technique using double-sided thin film heat flux gauges for measuring the HTC from a direct oil-cooled electrical machine with segmented stator. While thin film gauges are often used in transient measurements of the HTC on gas turbine components, their application to electrical machines has been largely unexplored. This is the topic of this paper. Due to the large viscosity of the coolant, the transient technique was found to be inadequate and a steady-state adaptation for oil-cooled machines was developed. This paper explores the challenges linked with this measurement technique when applied to oil-cooled machines, and develops new nondimensional correlations of the Nusselt number with Reynolds number. These correlations are applicable to machines with different geometries, flow, and coolant properties. The experimental results were compared to CFD simulations and existing pipe flow correlations. It is shown that these underpredict the HTC by approximately 60% at Re = 20. The discrepancy gradually decreases to around 10% at Re = 200.
Robert Camilleri; Paul Beard; David A. Howey; Malcolm D. McCulloch. Prediction and Measurement of the Heat Transfer Coefficient in a Direct Oil-Cooled Electrical Machine With Segmented Stator. IEEE Transactions on Industrial Electronics 2017, 65, 94 -102.
AMA StyleRobert Camilleri, Paul Beard, David A. Howey, Malcolm D. McCulloch. Prediction and Measurement of the Heat Transfer Coefficient in a Direct Oil-Cooled Electrical Machine With Segmented Stator. IEEE Transactions on Industrial Electronics. 2017; 65 (1):94-102.
Chicago/Turabian StyleRobert Camilleri; Paul Beard; David A. Howey; Malcolm D. McCulloch. 2017. "Prediction and Measurement of the Heat Transfer Coefficient in a Direct Oil-Cooled Electrical Machine With Segmented Stator." IEEE Transactions on Industrial Electronics 65, no. 1: 94-102.
This paper presents a computationally efficient thermo-fluid model to predict the temperature and flow distribution in an oil-cooled electrical machine with a segmented stator. The Yokeless and Segmented Armature axial flux machine was used as a case study in which a numerical model was set up and validated to within 6% of experimental results. The model was adapted to predict the temperature distribution of the segmented stator of a machine, identifying the hotspot temperatures and their location. Changes to the flow geometry on the stator temperature distribution were investigated. It was shown how by carefully controlling the flow distribution in the stator, the temperature distribution is improved and the hot spot temperature is reduced by 13 K. This benefits the machine by doubling the insulation lifetime or by increasing the current density by approximately 7%.
Robert Camilleri; David Howey; Malcolm D. McCulloch. Predicting the Temperature and Flow Distribution in a Direct Oil-Cooled Electrical Machine With Segmented Stator. IEEE Transactions on Industrial Electronics 2015, 63, 82 -91.
AMA StyleRobert Camilleri, David Howey, Malcolm D. McCulloch. Predicting the Temperature and Flow Distribution in a Direct Oil-Cooled Electrical Machine With Segmented Stator. IEEE Transactions on Industrial Electronics. 2015; 63 (1):82-91.
Chicago/Turabian StyleRobert Camilleri; David Howey; Malcolm D. McCulloch. 2015. "Predicting the Temperature and Flow Distribution in a Direct Oil-Cooled Electrical Machine With Segmented Stator." IEEE Transactions on Industrial Electronics 63, no. 1: 82-91.
This paper presents a computationally efficient flow network model to predict the flow distribution in compact multi-channel parallel flow heat exchangers. Compact U-type and Z-type heat exchangers with nine parallel channels were used as test case on which the model was validated to within 4–8% in terms of non-dimensional flow distribution ratio. The model was used to perform a sensitivity analysis of flow mal-distribution with changes in operational and geometric boundary conditions. The results show that the tube to header area ratio is an important global parameter for controlling mal-distribution. As the area ratio increases, flow mal-distribution becomes more pronounced and more sensitive to increased Reynolds number and decreased parallel pipe length.
R. Camilleri; D.A. Howey; M.D. McCulloch. Predicting the flow distribution in compact parallel flow heat exchangers. Applied Thermal Engineering 2015, 90, 551 -558.
AMA StyleR. Camilleri, D.A. Howey, M.D. McCulloch. Predicting the flow distribution in compact parallel flow heat exchangers. Applied Thermal Engineering. 2015; 90 ():551-558.
Chicago/Turabian StyleR. Camilleri; D.A. Howey; M.D. McCulloch. 2015. "Predicting the flow distribution in compact parallel flow heat exchangers." Applied Thermal Engineering 90, no. : 551-558.
Robert Camilleri; Malcolm McCulloch. Investigation of an Integrated Evaporative Cooling Mechanism for an Outer-Rotor Permanent Magnet Machine. Heat Transfer Engineering 2014, 36, 1192 -1202.
AMA StyleRobert Camilleri, Malcolm McCulloch. Investigation of an Integrated Evaporative Cooling Mechanism for an Outer-Rotor Permanent Magnet Machine. Heat Transfer Engineering. 2014; 36 (14):1192-1202.
Chicago/Turabian StyleRobert Camilleri; Malcolm McCulloch. 2014. "Investigation of an Integrated Evaporative Cooling Mechanism for an Outer-Rotor Permanent Magnet Machine." Heat Transfer Engineering 36, no. 14: 1192-1202.
R. Camilleri; M.D. McCulloch; D.A. Howey. Experimental investigation of the thermal contact resistance in shrink fit assemblies with relevance to electrical machines. 7th IET International Conference on Power Electronics, Machines and Drives (PEMD 2014) 2014, 1 .
AMA StyleR. Camilleri, M.D. McCulloch, D.A. Howey. Experimental investigation of the thermal contact resistance in shrink fit assemblies with relevance to electrical machines. 7th IET International Conference on Power Electronics, Machines and Drives (PEMD 2014). 2014; ():1.
Chicago/Turabian StyleR. Camilleri; M.D. McCulloch; D.A. Howey. 2014. "Experimental investigation of the thermal contact resistance in shrink fit assemblies with relevance to electrical machines." 7th IET International Conference on Power Electronics, Machines and Drives (PEMD 2014) , no. : 1.
This paper examines the benefits of a drivetrain that is able to disengage its propulsion motor from the driveline in an electric vehicle. The drivetrain was developed for an ultra-efficient eco vehicle competing in the Shell 2013 Eco Marathon. Various clutch mechanisms were examined. In spite of the complexity and losses associated with additional bearings and release surfaces, an actuated dog clutch was chosen as it offers superior performance due to the dual capability of freewheeling and regenerative braking that results. Track data from the event is presented along with experimental work that indicates that the clutch mechanism reduces power consumption by more than 35% for a ferrous permanent magnet propulsion motor. Savings were reduced to 5% for a coreless permanent magnet motor coupled to the driveline via an 11:1 straight cut spur gear arrangement. This reduced saving was due to the removal of hysteresis and eddy current losses from the stator. The paper also demonstrates during a competition in which the driver was aware of the energy consumption, the driving style changed when the technological option to free wheel was available. Finally the study was inferred onto a real world application with further experimental and simulation work on the Delta E4 Coupe, a high performance electric sports car. The vehicle uses a ferrous permanent magnet direct drive arrangement, indicated a reduction in power consumption of 10 to 14%. It is hoped that these insights are relevant when considering the development of electric vehicle drivetrains where machine topology and drive cycle will determine the value of a clutch mechanism.
R. Camilleri; P. Armstrong; N. Ewin; R. Richardson; David Howey; M.D. McCulloch. The Value of a Clutch Mechanism in Electric Vehicles. World Electric Vehicle Journal 2013, 6, 696 -706.
AMA StyleR. Camilleri, P. Armstrong, N. Ewin, R. Richardson, David Howey, M.D. McCulloch. The Value of a Clutch Mechanism in Electric Vehicles. World Electric Vehicle Journal. 2013; 6 (3):696-706.
Chicago/Turabian StyleR. Camilleri; P. Armstrong; N. Ewin; R. Richardson; David Howey; M.D. McCulloch. 2013. "The Value of a Clutch Mechanism in Electric Vehicles." World Electric Vehicle Journal 6, no. 3: 696-706.
P.M. Armstrong; D.A. Howey; R.W. Armstrong; R. Camilleri; M.D. McCulloch; R. Kang. A Reconfigurable PV Array Scheme Integrated Into an Electric Vehicle. Hybrid and Electric Vehicles Conference 2013 (HEVC 2013) 2013, 1 .
AMA StyleP.M. Armstrong, D.A. Howey, R.W. Armstrong, R. Camilleri, M.D. McCulloch, R. Kang. A Reconfigurable PV Array Scheme Integrated Into an Electric Vehicle. Hybrid and Electric Vehicles Conference 2013 (HEVC 2013). 2013; ():1.
Chicago/Turabian StyleP.M. Armstrong; D.A. Howey; R.W. Armstrong; R. Camilleri; M.D. McCulloch; R. Kang. 2013. "A Reconfigurable PV Array Scheme Integrated Into an Electric Vehicle." Hybrid and Electric Vehicles Conference 2013 (HEVC 2013) , no. : 1.
Robert Camilleri; T. Woolmer; A. Court; Malcolm McCulloch. Investigation into the temperature profile of a liquid cooled YASA© AFPM machine. 6th IET International Conference on Power Electronics, Machines and Drives (PEMD 2012) 2012, 1 .
AMA StyleRobert Camilleri, T. Woolmer, A. Court, Malcolm McCulloch. Investigation into the temperature profile of a liquid cooled YASA© AFPM machine. 6th IET International Conference on Power Electronics, Machines and Drives (PEMD 2012). 2012; ():1.
Chicago/Turabian StyleRobert Camilleri; T. Woolmer; A. Court; Malcolm McCulloch. 2012. "Investigation into the temperature profile of a liquid cooled YASA© AFPM machine." 6th IET International Conference on Power Electronics, Machines and Drives (PEMD 2012) , no. : 1.
Civil aviation has instilled new perceptions of a smaller world, creating new opportunities for trade, exchange of cultures and travelling for leisure. However, it also brought with it an unforeseen impact on the environment. Aviation currently contributes to about 3·5% of the global warming attributed from human activities. With the forecasted rate of growth, this is expected to rise to about 15% over the next 50 years. Although it is projected that the annual improvements in aircraft fuel efficiency are of the order of 1-2%, it is suggested that the current gas turbine design is fully exploited and further improvements are difficult to achieve. A new generation of aero engine core concepts that can operate at higher thermal efficiencies and lower emissions is required. One possibility of achieving higher core efficiencies is through the use of an inter-cooled (IC) core at high overall pressure ratios (OPR). The concept engine, expected to enter into service around 2020, will make use of a conventional heat exchanger (HEX) for the intercooler. This paper seeks to introduce a heat pipe heat exchanger (HPHEX) as an alternative design of the intercooler. The proposed HPHEX design takes advantage of the convenience of the geometry of miniature heat pipes to provide a reduction in pressure losses and weight when compared to conventional HEX. The HPHEX will be made of a number of stages, each stage being made of a large number of miniature heat pipes in radial configuration, that will extend from the inter-compressor duct to the bypass split, thus eliminating any ducting to and from the intercooler. This design offers up to 32% reduction in hot pressure losses, 34% reduction in cold pressure losses and over 41% reduction in weight. c2 [email protected]
R. Camilleri; S. Ogaji; P. Pilidis. Applying heat pipes to a novel concept aero engine: Part 1 – Design of a heat-pipe heat exchanger for an intercooled aero engine. The Aeronautical Journal 2011, 115, 393 -402.
AMA StyleR. Camilleri, S. Ogaji, P. Pilidis. Applying heat pipes to a novel concept aero engine: Part 1 – Design of a heat-pipe heat exchanger for an intercooled aero engine. The Aeronautical Journal. 2011; 115 (1169):393-402.
Chicago/Turabian StyleR. Camilleri; S. Ogaji; P. Pilidis. 2011. "Applying heat pipes to a novel concept aero engine: Part 1 – Design of a heat-pipe heat exchanger for an intercooled aero engine." The Aeronautical Journal 115, no. 1169: 393-402.
With the ever-increasing pressure for cleaner and more fuel efficient aero engines, gas turbine manufacturers are faced with a big challenge which they are bound to accept and act upon. The path from current high bypass ratio (BPR) engines to ultra high BPR engines via geared turbo fans will enable a significant reduction in SFC and CO2 emissions. However, in order to reach the emission levels set by the advisory council for aeronautics research in Europe (ACARE), the introduction of more complex cycles that can operate at higher thermal efficiencies is required. Studies have shown that one possibility of achieving higher core efficiencies and hence lower SFC is through the use of an intercooled recuperated (ICR) core. The concept engine, expected to enter into service around 2020, will make use of a conventional fin plate heat exchangers (HEX) for the intercooler and a tube type HEX as the recuperator. Although the introduction of these two components promises a significant reduction in SFC levels, they will give also rise to higher engine complexity, pressure losses and additional weight. Thus, the performance of the engine relies not only on the behaviour of the usual gas turbine components, but will be heavily dependent on the two heat exchangers. This paper seeks to introduce a heat pipe heat exchanger (HPHEX) as alternative designs for the intercooler and the recuperator. The proposed HPHEX designs for application in an ICR aero engine take advantage of the convenience of the geometry of miniature heat pipes to provide a reduction in pressure losses and weight when compared to conventional HEX. The proposed HPHEX intercooler design eliminates any ducting to and from the intercooler, offering up to 32% reduction in hot pressure losses, 34% reduction in cold pressure losses and over 41% reduction in intercooler weight. On the other hand the proposed HPHEX recuperator design can offer 6% improvement in performance, while offering 36% reduction in cold pressure losses, up to 80% reduction in hot pressure losses and over 31% reduction in weight. An ICR using HPHEX for the intercooler and recueprator may offer up to 2·5% increase in net thrust, while still offering 3% reduction in SFC and up to 7·7% reduction in NOX severity parameter, when compared to the ICR using conventional HEX. c2 [email protected]
R. Camilleri; S. Ogaji; P. Pilidis. Applying heat pipes to a novel concept aero engine: Part 2 – Design of a heat-pipe heat exchanger for an intercooled-recuperated aero engine. The Aeronautical Journal 2011, 115, 403 -410.
AMA StyleR. Camilleri, S. Ogaji, P. Pilidis. Applying heat pipes to a novel concept aero engine: Part 2 – Design of a heat-pipe heat exchanger for an intercooled-recuperated aero engine. The Aeronautical Journal. 2011; 115 (1169):403-410.
Chicago/Turabian StyleR. Camilleri; S. Ogaji; P. Pilidis. 2011. "Applying heat pipes to a novel concept aero engine: Part 2 – Design of a heat-pipe heat exchanger for an intercooled-recuperated aero engine." The Aeronautical Journal 115, no. 1169: 403-410.