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High-frequency electromagnetic linear machine is one major component for linear eletro-hydraulic actuator that in turn is extrimely important for the flight control of more-electrical or all-electrical aircrafts. The employment of high-frequency linear machine helps to achieve high reliability and dynamic performance of the actuators. However, the capability of heat dissipation of the linear machine unavoidably constrains the input current, which in turn depresses its output performance. Therefore, this paper proposes a novel electromagnetic linear machine based on the self-powered direct oil-cooling windings. Specifically, the windings are immersed into the oil directly, which helps to decrease the temperature of the linear machine significantly and thus increase its output performance. In addition, the oil is pushed by the motion of the mover itself. No additional pump is required. The design concept of high-frequency electromagnetic linear machine along with its operating principle is presented. A high-precision three-dimensional (3D) piecewise modeling method is proposed to simultaneously consider axial, radial and circumferential equivalent thermal circuits. Numerical simulation is conduced to validated the analytical model. A research prototype of the machine based on direct oil-cooling windings is developed and empolyed for experimental study, and the experimental result verifies the mathematical model of the thermal field well.

Publisher Copyright: IEEE With growing interest in green technologies and sustainable transport, hybrid and pure electric powertrains are attracting a lot of attention. According to demanded metrics, such as lightweight and high-power density motors, these offer clear motivation to develop advanced thermal management methods and integrate them with conventional cooling approaches. The oil spray cooling method is one of the latest cooling methodologies integrated with the conventional cooling approaches. Therefore, this article provides a comprehensive study on the oil spray cooling approach for electrical motors utilized in electric vehicle (EV) traction application drives. The objective is to provide the reader with a picture of the state of the art regarding the opportunities, challenges, and offered solutions for the cooling requirements in EV motors. In addition, this article presents the guidelines for selecting the appropriate spray nozzles and coolants as well as estimating their performance, spray characteristics, and heat transfer coefficient (HTC) during the design period. Besides, various closed-loop systems of spray cooling approach, including refrigerants as a coolant, low viscosity liquid coolant with high boiling temperature, and high viscosity lubricant oil as a coolant, are discussed with the pros and cons of each system being compared. Moreover, real-life examples of this method, applied in the latest automotive traction motor prototypes, have been described and evaluated. Finally, the performance of different schemes is addressed.

To form the stator slots and isolate the stator and rotor, composite components for the oil-cooling air-core stator of a high temperature superconducting motor (HTSM) were designed based on a process that could be summarized as follows. First, the computational fluid dynamics analysis of the oil-cooling air-core stator was conducted. From the results, the load of temperature and oil pressure that apply on the composite cylinder were chosen to be 50 °C and 0.1 MPa, respectively. Second, the structure of the composite components was designed according to the forming technology, and the performance of that was obtained from the finite element method. The results show that the composite teeth were chosen to be a combination of GFRP block and 1Cr18Ni9Ti sheet. And the stresses of the composite cylinder with the thickness of 11 mm in all directions were lower and without buckling at 0.1 MPa. Third, the full-scale composite cylinder was designed and manufactured, and a full-scale simplified performance test platform was also developed to verify the strength of the cylinder. The test results show that the maximum strain of measuring point on the cylinder under 0.1 MPa is 325.1 $\mu \varepsilon $ , which meets the design requirements of the HTSM.

A 2 MW direct-drive (DD) high temperature superconducting (HTS) wind power generator with HTS wires in the rotor field windings and copper transposed conductor in the stator coils was explored for the wind turbine application in this study. An oil-cooling air-core stator with non-magnetic teeth of the 2 MW DD HTS generator was designed because the high flux density generated by the HTS wires wound result in larger dissipation in iron teeth, and the process of that could be summarized as follows. First, a 2 MW DD HTS wind power generator was designed, and the electromagnetic (EM), loss, EM force, and insulation of the DD HTS generator were analyzed and developed, respectively. Second, the thermal and mechanical of the one pole pair oil-cooling air-gap armature was analyzed by the finite element analysis. Then, a pole pair segment of the oil-cooling air-core stator with the same structure as the 2 MW generator was designed and manufactured to identify potential challenges, obtain practical knowledge before production, and then reduce the development risk of the 2 MW DD HTS generator. Furthermore, a test system with converter, oil-cooling system, and data acquisition equipment was developed simultaneously to test the temperature distribution of the slotless stator. The performance test results show that the maximum temperature rise of the one pole pair oil-cooling stator under rated conditions is about 81.4 K, which satisfies the design requirements of the 2 MW DD HTS generator.

Tooth coil windings, in particular when using a double layer structure, present opportunities for in-slot liquid cooling. Since the windings are not overlapping, access to the slot from the end section for coolant liquids is enabled. In this article, a solution for in-slot and in-stator direct oil cooling for a tooth coil winding machine is presented. The coils are prewound on bobbins and inserted on the stator teeth. The novelty of the design consists in the integration of the cooling, using a thermally conductive epoxy resin to create the channels within the slot as well as the positioning of the stator yoke cooling channels. A 50-kW machine for an automotive traction application is designed, manufactured, and tested. Conjugate heat transfer simulations are used in the design process in combination with finite-element analysis for the loss mapping. The thermal model is verified with measurements at 6-L/min oil flow and 17.5 A/mm $^2$ continuous and 35 A/mm $^2$ 30-s peak. The thermal model is then used to establish a continuous operating point at 25 A/mm $^2$ .

Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.

This paper presents the heat transfer analysis of the electric vehicle motor and optimization of an operating parameter for improving the performance of the motor with an oil cooling system. The homogeneous multi-phase flow model in commercial software, ANSYS CFX, is applied to solve the flow of mixture, including oil and air. We mainly focus on the influence of operating (oil level) and driving conditions (roll and pitch angles) on the cooling system. Several CFD simulations are performed with various input parameters (oil level, roll, and pitch angles) generated from the Latin Hypercube Sampling method. Based on the CFD results, we built a Polynomial Chaos Expansions based surrogate model to predict the temperature distribution, maximum temperature, and torque loss, which respond to the input parameters. Sensitivity analysis indicates that the oil level significantly affects system performance (maximum temperature and torque loss). Finally, the optimal range of oil level is estimated, considering the maximum allowable temperature of the motor.

Based on the structure analysis and the working principle of cylindrical giant magnetostricve actuator (CGMA) for ball screw preload, a thermal error suppression method using oil cooling system to control the temperature is proposed. Firstly, the heat transfer model and thermal circuit model of CGMA are established; next, the steady-state temperature model and the thermal expansion displacement model of cylindrical giant magnetostrictive material (CGMM) are obtained according to the heat-transfer rules and loop analysis method in circuit analysis; finally, the design parameters of the oil-cooling temperature control system are determined by combining thermal circuit model analysis with finite element simulation analysis. Such optimization method saves a lot of computation and provides a simple way for the design of oil cooling structure. In addition, a test platform for the CGMA is established. The experimental results indicate that the measured temperatures are in good agreement with the simulation results under forced oil cooling, and the relative error is less than 5%, which proves the rationality of the temperature control system. Moreover, the output accuracy and stability of the CGMA is significantly improved with proposed oil cooling method, which further confirms the thermal error suppression method is effective. As a result, this study provides a basis for the application of CGMA in the precise adjustment of double-nut ball screw preload.

Unreliability and interruptions facing power supply are evidence of the excessive heat generated in power systems, as a result of the inefficiency of oil cooling medium employed in distribution transformers. The design and implementation of a prototype automatic temperature control system is to be employed as a method towards solving the above stated problem of excessive temperature rise in distribution transformers. The prototype design consists of a PIC microcontroller programmed in C language, an LM35 temperature sensor, an electric fan and other diverse electronic component. It operates a mechanism that detects temperature rise in the transformer and automatically turns on the cooling fan at extreme temperature conditions. A 16x2 LCD is employed as the medium for temperature display unit of the transformer. The resulting prototype functions in a way that it has the ability to detect every 1ºC rise and reduction in the temperature of the transformer. Thus, at extreme temperature conditions, the automatic temperature control system diminishes the excessive heat generated in the transformer to the appropriate working temperature condition. Orjiewulu, J. C. | Department of Electrical Electronics Engineering, University of Benin, Benin City, Edo State, Nigeria.

Cooling capacity decreases due to faults appearing over time in the thrust bearing oil cooling systems of hydroelectric power plants and cooling process cannot proceed sufficiently. For this reason, while the turbine-generator unit generates energy, the thrust bearing heats up. This temperature problem prevents the unit from operating at full capacity and therefore decreases in energy production. Producing deficient energy in hydroelectric power plants, which is a renewable energy source, causes long-term economic losses for countries. In this study, the thrust bearing cooling system of a vertical Francis turbine, which produces 150 MW of energy per hour, is investigated. The reduction in the cooling capacity over time in turbine thrust bearing cooling system is solved by using exchanger system with additional plate and the power produced by the turbine-generator unit is increased 15 MW/h. This improvement has greatly contributed to the national economy. The method of increasing the cooling capacity applied to the hydroelectric power plant thrust bearings can be applied to all hydraulic turbines. This method will increase the energy production amount of the unit by approximately 10% and it costs approximately 80% cheaper than completely replacing the existing cooling system.

Baja ST 41 merupakan salah satu dari jenis baja golongan baja karbon rendah dan dapat ditingkatkan lagi sifat mekaniknya dengan cara proses perlakuan panas. Hardening merupakan proses perlakuan panas yang bertujuan untuk meningkatkan kekerasan serta kekuatan baja dengan cara pemanasan, penahanan dan pendinginan dalam interval waktu dan media pendingin tertentu. Tujuan penelitian ini adalah untuk mengetahui pengaruh temperatur pemanasan dan media pendingin terhadap kekerasan dan struktur mikro baja ST 41. Proses hardening dilakukan pada temperatur austenit (850oC, 900oC dan 950oC) dengan waktu tahan (holding time) 15 menit kemudian didinginkan cepat menggunakan media pendingin aquades, oli SAE 20W-50, dan air kelapa. Hasil pengujian menunjukkan nilai kekerasan optimum adalah 326,2 HV pada temperatur pemanasan 850oC dengan media pendingin air dan kekerasan minimum 153,1 HV pada temperatur pemanasan 950oC dengan media pendingin oli SAE 20W-50, sementara hasil pengujian struktur mikro setelah proses hardening memperlihatkan struktur yang terbentuk adalah martensit dan bainit. Daripenelitian ini dapat diambil kesimpulan bahwa proses hardening dapat menaikkan nilai kekerasan pada baja ST 41.

The hot-spot temperature is a key parameter in transformer loading management. It plays a significant role in evaluating transformer winding thermal performances, as well as in the determination of winding insulation’s loss of life. A simplified winding thermal model has been developed based on the presented methodology in favour to reduce real-world model complexity. A conjugate heat transfer has been approached to solve the cooling effects of natural oil convection. Results show a good agreement with only 3.1% percentage difference for the average winding temperature between the newly developed winding model and manufacturer factory-end test report. The plotted graphs of oil flow and thermal distributions showed a unique relation between localised hot-spot temperature and oil flow patterns. The hottest temperature and its location are well pronounced with the inclusion of eddy current loss distribution within winding height. The proposed methodology can be used to investigate the oil cooling scheme of transformer winding and allows the manufacturers to optimise their thermal design.

Si3N4-GCr15 (silicon nitride-bearing steel) friction pair is often used in high-speed bearings. The molecular dynamics model of graphene additive lubricating oil (mixed oil) is developed to study the effect of graphene as a nano lubricant additive on the thermal conductivity of the lubricating oil. With the research temperature range of 298~532 K, the results of internal molecular dynamics simulation show that the thermal conductivity of mixed oil increases with the increase in the graphene mass fraction at 298 K. When the temperature is higher than 298 K, the thermal conductivity of the mixed oil increases first and then decreases with the increase of the graphene mass fraction. When the mass fraction of graphene is constant, the thermal conductivity of the mixed oil increases first and then decreases with the increase of temperature. An experiment was designed to investigate the heat transfer coefficient for mixed lubricating oil at test specimen surface. Experiments show that an appropriate amount of graphene is added to improve the convective heat transfer between the lubricating oil and the test piece. However, as the amount of graphene added increases, the viscosity of the mixed oil increases, thereby inhibiting the fluid flow behaviour, resulting in a decrease in the convective heat transfer coefficient. This shows that only an appropriate amount of graphene additive has a cooling effect on Si3N4-GCr15 friction pair.

The presence of harmonics in locomotives used in Indian Railways has started to become one of the major concerns during the last few years. The cause of harmonics distortions in these locomotives is due to the increase in the use of power electronics devices, wherein the introduction of GTO and IGBT-based locomotives have brought up technological advancement in railways, while on the other hand it have its own certain limitations as well. Hence, the study was carried out on oil cooling blowers and traction motor blowers used in a locomotive which uses GTO and IGBT-based converters. This paper presents the analysis of current harmonics which were recorded using a current clamp and DSO.

Stator coils of automobiles in operation generate heat and are cooled by coolant poured from above. The flow characteristic of the coolant depends on the coil structure, flow condition, solid–fluid interaction, and fluid property, which has not been clarified due to its complexities. Since straight coils are aligned and layered with an angle at the coolant-touchdown region, the coil structure is simplified to a horizontal square rod array referring to an actual coil size. To obtain the flow and wetting characteristics, two-phase fluid flow simulations are conducted by using the phase-field lattice Boltzmann method. First, the flow onto the single-layered rod array is discussed. The wetting area is affected both by the rod gap and the wettability, which is normalized by the gap and the averaged boundary layer thickness. Then, the flow onto the multi-layered rod arrays is investigated with different rod gaps. The top layer wetting becomes longitudinal due to the reduction of the flow advection by the second layer. The wetting area jumps up at the second layer and increases proportionally to the below layers. These become remarkable at the narrow rod gap case, and finally, the dimensionless wetting area is discussed at each layer.

Cooling media is a substance that increases the hardness value of a materialthrough a heat-treatment process. This study aims to determine the effect of cooling media on the hardness of ST 37 steel due to Gas Tungsten Arc Welding (GTAW). The method used is an experimental method using the independent variables, namely water cooling media, seawater cooling media, and oil cooling media, while the dependent variable is the hardness test result. In specimens using water cooling media, the hardness in the weld area is 47.19 kg/mm2, in the HAZ area the it is 54.6 kg/mm2, and the base metal gets a value of 40.87 kg/mm2. While the specimens with seawater cooling media get a value in the weld area of 76.37 kg/mm2, in the HAZ area it gets a value of 83.89 kg/mm2 and the base metal gets a value of 70.13 kg/mm2. The specimens with oil cooling media the value in the weld area is 40.77 kg/mm2, in the HAZ area it gets a value of 43.32 kg/mm2 and the base metal gets a value of 36.09 kg/mm2 . From the hardness values obtained, specimens immersed in seawater cooling media have the highest hardness values compared to water and oil cooling media.

In recent years, the automotive industry has seen increasing applications of oil cooling in drivetrain designs. Oil jet cooling is one of the most popular schemes that can be found in many modern commercial products. However, literatures focusing on the topic are few. This paper presents a new way of modelling electrical machines with hairpin windings and oil jet cooling using experimental data. A custom build experiment setup is used to conduct oil jet cooling experiments on a stator with hairpin windings. The modelling of the machine is performed with Motor-CAD software using a new type of thermal resistance network. The proposed workflow is also applied to spray cooling designs. Simulation results and experimental results show good agreement with each other, suggesting that the proposed workflow can be used to facilitate designing of similar electrical machines.

In the production process of the oil cooling pipe, the roundness error of the pipe is mainly measured manually, which has the problem of low detection efficiency and inability to detect in real-time. Based on machine vision, this paper proposes a method for roundness detection and sorting of oil cooling pipes. By establishing the kinematics model of the robot SR7CL, then using Adams and Matlab to simulate kinematics and dynamics to verify the correctness of the model and ensure the accuracy of grasping. Taking the nozzle of the oil cooling pipe as the research object, the characteristics of the nozzle are highlighted through adaptive threshold segmentation, and the contour information are extracted by the Canny algorithm. Finally, used the least square method to detected the roundness error, and the cooling pipes are determined according to the roundness error. This system not only improves the quality and efficiency of detection, but also solves the real-time problems.

A grain boundary diffusion process (GBDP) was adopted to improve magnetic properties of Dy-free highly coercive Nd–Fe–B permanent magnet by coating thin layers of Nd and Cu in grain boundaries. For GBDP of Nd and Cu, Nd and Cu were coated by wet process, e.g., electrochemical and electroless on Nd–Fe–B magnets, which was fabricated by hot-deformed/die-upset with melt-spun specimen. Heat treatment was performed for 20 min at 600 °C followed by several different cooling conditions. The cooling conditions after heat treatment were varied to understand distribution and microstructural effects of Nd and Cu species in grain boundaries. The coercivity increased from 1.565 to 1.637 T in oil cooling rate but remanence decreased, while remanence jumped with little decrease in coercivity in furnace cooling. Microstructure analyses suggested that the coercivity was closely related to the cooling rate as well as distribution of Nd. The mechanism of coercivity enhancement due to the cooling rate was discussed based on the results presented here and those in the literature.

Conducting thermal calculations of "hot" oil pipelines through which high-viscosity and high-sticking oils are transported is one of the main ones. Determining the rate of cooling of oil in a stopped pipeline is of practical importance. According to the cooling rate, the time to safely stop the "hot" pipeline is calculated. This is the time at which the "hot" oil pipeline doesn’t freeze and the station’s pressure is enough to overcome the shear stresses arising during the cooling f high-viscosity and high-sticking oil. Oil cooling in underground stopped pipelines depends on the temperature of the soil around it. Installed heat stabilizers designed to cool the soil can affect the cooling rate of the "hot" pipeline. We have carried out a numerical experiment using modern tools of mathematical modelling. The experiment showed that the installed soil heat stabilizers near the underground "hot" pipeline have an impact on the process of cooling oil. These stabilizers have reduced the time to safely stop the pipeline.

Oil heat management must be reviewed globally as an integrated function as a consequence of the development of the next generation of aeroengines because of its strong effect on the cooling strateg...

The development of science and technology today has a significant influence on technological development and advances in the industrial world. Casting is a product manufacturing technique in which the metal is melted in a furnace and then poured into a mold cavity that is similar to the original form of the cast product to be made. One of the results or products produced from the casting method in this study is a weaving gear component. The gear serves as a short distance power transmission based on the rotation ratio from the main shaft to the drive shaft. This study purpose to determine the effect of the quenching process with oil cooling media on cast iron material. The testing results reveal that the composition test results in 3.18% carbon content, such that the components in this gear manufacturing are used in cast iron, which essentially has the characteristics of being heat-resistant and brittle. It is also necessary to use it as a way of producing materials feeling the continuous impact. The brittling effect of quenching oil heat treatment improves the quality of the materials. It is observed from the research findings that use the Vickers hardness test that the quenching heat treatment shows a substantial difference in score. The highest Vickers hardness test score with quenching oil materials achieving a score of 427.84 VHN is seen. The test exhibits the maximum value of 378.18 VHN in raw materials.Keywords: Cast iron, quenching, chemical composition, Vickers hardness.

In this paper, a forced oil cooling scheme is proposed for a novel modular consequent-pole permanent magnet machine (CPM) with E-core stator. In this modular machine, flux gaps (FGs) that are normally used for improving electromagnetic performance and simplifying the winding process, can also be utilized as cooling channels for the oil to pass through, leading to significantly improved machine internal cooling. Computational fluid dynamics (CFD) analyses have been carried out and the results indicate that circa 15°C reduction in the peak temperature can be achieved based on the initial design. Moreover, the influences of several other critical parameters such as inlet position and geometry have been investigated, and optimal inlet configurations have been identified to realize the temperature uniformity. Some useful design guidelines for thermal management in the modular CPMs have also been provided in this paper.

This report details the testing of an ACT turbo-expander on a high-speed Diesel engine to explore if NOX reduction can be achieved by turbo-expansion cooling. NOX reduction in Diesels is needed due to the detrimental environmental and health impacts it has across the globe. Testing was completed using a Ford 1.5 DuraTorq engine and a custom test cycle. The test cycle was developed to test the most used section of the engines rev range, whilst also overcoming oil cooling and low intake temperature issues. A NOX analyser failure meant that NOX emissions result could not be gathered. Exhaust temperatures were compared between the standard engine and turbo-expander equipped engine, as a decrease in exhaust temperatures would indicate a reduction in combustion temperature and therefore NOX emissions. 3 tests were carried out under each condition; the results were then analysed using a two-tailed T-test with a significance level of 0.05. The results showed that at an engine speed of 2500rpm or greater the reduction in exhaust temperature was statistically significant, with the largest reduction in exhaust temperature being 34.51°C at 2750rpm at 70% throttle. At low engine speeds the turbo-expander was showed to increase the exhaust temperature with the largest increase being 52.28°C at 2000rpm at 70% throttle. The turbo-expander was also proven to reduce engine power by an average of 1kW due the reduced intake pressure resulting from the frictional loses in the turbo-expander rotating assembly. If testing is repeated changes to the test setup must be made to make it more repeatable and to capture more data.