Reduce Heat Generation Research Articles

Dedicated drill design for reduction in burr and delamination during the drilling of composite materials

In the drilling of composite materials such as carbon fiber reinforced plastic, burrs and delamination occur during machining. This study proposed a design of a drill tool with a shape that suppresses burrs and delamination during the drilling of composite materials. The tool shape (tip, groove, land, etc.) is determined, and a nick shape that cuts off chips and reduces heat generation is adopted. A finite element analysis and an experimental evaluation involving 4600 holes were conducted. The maximum errors in the hole diameter and roundness were 15 μm and 0.016, respectively. Further, the maximum burr height was observed to be 80 μm or less, and delamination was not observed in the experiment.

Tribological characteristics of cast polyamide 6 (PA6G) matrix and their composite (PA6G SL) under normal and overload conditions using dynamic pin-on-plate system

The current study addresses the tribological characteristics of Cast Polyamide 6 (PA 6 G) matrix and its composite filled with polyethylene (PE) solid lubricant (PA 6 G SL). Tribological tests under different contact kinematics (1) traditional pin-on-disc (PoD) and (2) dynamic pin-on-plate (PoP). Tribotests revealed that the PA 6 G SL composite showed increased wear resistance and reduction in heat generation as compared to the virgin PA 6 G matrix. The difference in tribological characteristics was analyzed with respect to morphology (primary and secondary layer) of the transfer layer formed on the counter material. In summary, the solid lubricant alters the tribological process by means of altering the surface response by introducing a limitation in the wear particle generation.

A new multiple air beam approach for in-process form error optical measurement

In-process measurement can provide feedback for the control of workpiece precision in terms of size, roughness and, in particular, mid-spatial frequency form error. Optical measurement methods are of the non-contact type and possess high precision, as required for in-process form error measurement. In precision machining, coolant is commonly used to reduce heat generation and thermal deformation on the workpiece surface. However, the use of coolant will induce an opaque coolant barrier if optical measurement methods are used. In this paper, a new multiple air beam approach is proposed. The new approach permits the displacement of coolant from any direction and with a large thickness, i.e. with a large amount of coolant. The model, the working principle, and the key features of the new approach are presented. Based on the proposed new approach, a new in-process form error optical measurement system is developed. The coolant removal capability and the performance of this new multiple air beam approach are assessed. The experimental results show that the workpiece surface y(x, z) can be measured successfully with standard deviation up to 0.3011 µm even under a large amount of coolant, such that the coolant thickness is 15 mm. This means a relative uncertainty of 2σ up to 4.35% and the workpiece surface is deeply immersed in the opaque coolant. The results also show that, in terms of coolant removal capability, air supply and air velocity, the proposed new approach improves by, respectively, 3.3, 1.3 and 5.3 times on the previous single air beam approach. The results demonstrate the significant improvements brought by the new multiple air beam method together with the developed measurement system.

Continuous-wave, singly-resonant, intracavity optical parametric oscillator based on a single-mode-laser-diode-pumped Yb:KYW laser.

We report a continuous-wave (cw), intracavity, singly resonant optical parametric oscillator (ICSRO) based on an Yb:KYW laser pumped by a single-mode laser diode (LD). Pumping the ICSRO by a low-noise single-mode LD, combined with the reduced heat generation due to the lower quantum defect of the Yb:KYW laser system, effectively eliminated the onset of relaxation oscillations, which have been a long-standing problem in previous multimode-LD-pumped ICSROs, and resulted in a cw ICSRO being operated free of relaxation oscillations. At an LD power of 515mW, the generated idler power was 21mW at ∼3500 nm. To the best of our knowledge, this is the first demonstration of a single-mode-LD-pumped ICSRO.

Numerical simulation of laser preheating of friction stir welding of dissimilar metals

ABSTRACTFriction stir welding, FSW, of harder metal alloys is difficult to perform, like here dissimilar welding of titanium alloy to stainless steel in butt joint configuration. One major limitation is tool wear which can be reduced by preheating with a laser beam. A mathematical model to calculate the tool forces during FSW was developed further. The calculations show that the laser beam reduces forces at the pin and shoulder of the FSW-tool, accompanied by reduced heat generation through the tool. Within its operating limits, the process has low sensitivity on the lateral position of the leading laser beam. The model supports the understanding and optimisation of the complex interaction zone of forces and heat around the FSW-tool.

Experimental and Numerical Investigation of the Outer Ring Cooling Concept in a Hybrid and in an All-Steel Ball Bearing Used in Aero-Engines by the Introduction of a Helical Duct

Rolling element bearings for aero engine applications have to withstand very challenging operating conditions because of the high thermal impact due to elevated rotational speeds and loads. The high rate of heat generation in the bearing has to be sustained by the materials, and in the absence of lubrication these will fail within seconds. For this reason, aero engine bearings have to be lubricated and cooled by a continuous oil stream. When the oil has reached the outer ring it has already been heated up, thus its capability to remove extra heat from the outer ring is considerably reduced. Increasing the mass flow of oil to the bearing is not a solution since excess oil quantity would cause high parasitic losses (churning) in the bearing chamber and also increase the demands in the oil system for oil storage, scavenging, cooling, hardware weight, etc. A method has been developed for actively cooling the outer ring of the bearing. The idea behind the outer ring cooling concept was adopted from fins that are used for cooling electronic devices. A spiral groove engraved in the outer ring material of the bearing would function as a fin body with oil instead of air as the cooling medium. The method was first evaluated in an all steel ball bearing and the results were a 50% reduction in the lubricating oil flow with an additional reduction in heat generation by more than 25%. It was then applied on a Hybrid ball bearing of the same size and the former results were reconfirmed. Hybrid bearings are a combination of steel made parts, like the outer ring, the inner ring, and the cage and of ceramic rolling elements. This paper describes the work done to-date as a follow up of the work described in, and demonstrates the potential of the outer ring cooling for a bearing. Friction loss coefficient, Nusselt number, and efficiency correlations have been developed on the basis of the test results and have been compared to correlations from other authors. Computational Fluid Dynamics (CFD) analysis with ANSYS CFX has been used to verify test results and also for parametric studies.

Methods of Cement Replacement and Cement Paste Replacement to Reduce Heat Generation of Concrete

Methods of Cement Replacement and Cement Paste Replacement to Reduce Heat Generation of Concrete

Methods of Cement Replacement and Cement Paste Replacement to Reduce Heat Generation of Concrete

Methods of Cement Replacement and Cement Paste Replacement to Reduce Heat Generation of Concrete

Heterogeneously Integrated Membrane Lasers on Si Substrate for Low Operating Energy Optical Links

High demand exists for low operating energy optical links that use wavelength division multiplexing technologies in datacenter networks. Thus, we fabricate a directly modulated membrane distributed-reflector laser with low operating energy on a thermally oxidized silicon (Si) substrate. Because we use epitaxial growth to bury an active region on a directly bonded InP-based membrane, it needs to be kept within a critical thickness, which is related to the growth temperature and the thermal expansion coefficients of materials. In previous studies, we used 250-nm-thick structures, causing relatively large series resistance that limited device performance on such aspects as energy cost and output power. In this study, we increase the III–V membrane thickness to 350 nm, which is close to the calculated critical thicknesses. We achieve the same high crystal quality of multiquantum-wells found in our previous studies. The fabricated laser shows a differential resistance of 72 Ω and thermal resistance of 982 K/W. Thanks to a reduction in bias voltage, the laser can be directly modulated at 25.8 Gbit/s with an energy cost of 97 fJ/bit. In addition, due to a reduction in heat generation, direct modulation with a 50-Gbit/s non return to zero signal is demonstrated by increasing bias current up to 10 mA.

Examination on The Number of Strands of Litz Wire Used for Transformer for LLC resonance Converter

In this paper, the results of examining the number of strands for high efficiency and low heat generation of litz wire used for transformer of LLC resonant converter are described. Converter used for switching power supplies are required to be smaller and more efficient. To reduce the size of the converter, examinations have been made by increasing the frequency of the driving frequency. However, due to the high frequency, heat generation in the winding increase due to an increase in AC resistance in the transformer, which is one of the programs of high frequency. In view of this, we study reduction in heat generation by making the wire diameter of the winding constant and changing the number of strands. As a results, it is possible to improve efficiency of the LLC converter by 0.3 % and suppress heat generation of the transformer at 37 °C.

Exploring the Effect of Frictional Heat on Rate of Fuel Combustion by ICE through Modeling and Simulation with Reference to ICE Parameters.

Otto cycle operations of ICEs have relatively higher capacities and efficiency. Factors of efficiency, emission, fuel consumption and output power are considered during design and construction of ICEs. Engine size, engine weight, number of pistons, swept volume, cylinder arrangement and number of valves all differs in accordance to type of ICE. Fundamental principle of ICE is burning of air – fuel mixture of appropriate proportions in air tight chamber to produce heat energy for motion. Fossil fuel of diesel and gasoline obtained from underground are the main fuels used by ICEs. The engine block houses cylinders, pistons rings, connecting rods and pistons. At top seals of cylinders are located inlet valves, outlet valves and channels. Crankcase houses crankshaft and bearings whiles the sump serves as reservoir for lubrication oil. Lubrication oil also known as lubricant reduces friction between moving surfaces in ICEs through piston ring grooves. Connecting rod is the linkage between crankshaft and piston. Gudgeon – pin transmits combustion force from piston to connecting rod then to crankshaft. Thus, crankshaft converts reciprocating motion of piston to cyclic motion. During operations of ICEs, friction occurs between pistons with piston rings collectively and inner walls of cylinder. Frictional effects account for about thirty five percent (35%) of total heat generated in ICEs. The methodology adopted by this article is modeling and simulating frictional models by previous authors. These models were incorporated with ICE parameters before modeling and simulation again. Objectively, graphical results show reduction in heat generation due to friction.

Stabilizing the Electrode/Electrolyte Interface of LiNi0.8Co0.15Al0.05O2 through Tailoring Aluminum Distribution in Microspheres as Long-Life, High-Rate, and Safe Cathode for Lithium-Ion Batteries

The unstable electrode/electrolyte interface of high-capacity LiNi0.8Co0.15Al0.05O2 (NCA) cathodes, especially at a highly delithiated state, usually leads to the transformation of layered to spinel and/or rock-salt phases, resulting in drastic capacity fade and poor thermal stability. Herein, the Al-increased and Ni-,Co-decreased electrode surface is fabricated through tailoring element distribution in micrometer-sized spherical NCA secondary particles via coprecipitation and solid-state reactions, aimed at stabilizing the electrode/electrolyte interface during continuous cycles. As expected, it shows much extended cycle life, 93.6% capacity retention within 100 cycles, compared with that of 78.5% for the normal NCA. It also delivers large reversible capacity of about 140 mAh g-1 even at 20 C, corresponding to energy density of around 480 Wh kg-1, which is enhanced by 45% compared to that of the normal NCA (about 330 Wh kg-1). Besides, the delayed heat emission temperature and reduced heat generation mean remarkably improved thermal stability. These foregoing improvements are ascribed to the Al-increased spherical secondary particle surface that stabilizes the electrode/electrolyte interface by protecting inner components from directly contacting with electrolyte and suppressing the side reaction on electrode surface between high oxidizing Ni4+ and electrolyte.

Performance enhancement of cryogenic machining and its effect on tool wear during turning of Al-Ticp composites

ABSTRACTThe current research is to focus on developing a liquid nitrogen diffusion system to optimize the usage of liquid nitrogen and maximizing cooling and lubrication capability by effective penetration. An atomized liquid nitrogen spray system was developed to diffuse liquid nitrogen effectively at a low flow rate (10–12 L/h) and as a high velocity (8–50 m/s) droplet jet to the machining zone. Using coated carbide tool with varying tool geometry (rake angle, approach angle, and nose radius), an investigation was performed to study the role of atomized liquid nitrogen spray-assisted machining, on performance of tool and surface quality of the machined workpiece during turning of Al-TiCp composite. To analyze the performance of liquid nitrogen spray-assisted machining, various experiments were conducted. The results obtained from the experiments reveal that the effective use of atomized liquid nitrogen spray machining is a feasible alternative to dry, wet, and cryogenically chilled argon gas. This technique significantly reduces heat generation in machining zone. The study also emphasizes the influence of tool geometry on the machinability of Al-TiCp metal matrix composites.

Temperature Sensitive Microprocessor Design to Reduce Heat Generation and Improve Performance

Temperature Sensitive Microprocessor Design to Reduce Heat Generation and Improve Performance

Tool wear and surface integrity of inconel 718 in dry and cryogenic coolant at high cutting speed

The high speed machining of Inconel 718 represents a significant challenge. This is attributed to the excessive heat generated during the chip formation process, which elevates the cutting tool temperature and accelerates tool wear. The heat generated can shorten the tool life and lead to dimensional inaccuracies. In severe cases, this circumstance can result in product damage. During the milling process, the use of conventional cutting fluids to control heat generation may not be sufficiently effective. This is due to the inability of these fluids to fully penetrate the cutting zone. Such a situation can lead to the development of health and environmental problems. To overcome this dilemma, a cryogenic cooling unit using liquid nitrogen (LN2) was developed to cool the tool–chip interface. This cooling technique is not only more efficient, but also environmental friendly. This paper presents the experimental investigations conducted to assess the effectiveness of cryogenic cooling for the milling of Inconel 718 in comparison to the dry cutting process. This comparison embraced tool wear rate, mechanism wear, cutting force, surface roughness and microstructure changes. The experiments involved the use of PVD coated with TiAlN/AlCrN ball nose tungsten carbide for varying cutting speeds ranging between 140–160m/min, a feed rate of 0.15–0.20mm/tooth, and a radial depth of cut of 0.2–0.4mm. The axial depth of cut was kept constant at 0.3mm. The results revealed that the cryogenic cooling process is more effective than dry cutting for reducing tool wear, lowering the required cutting force, improving surface roughness, lessening deformation of microstructure changes at the sub-surface level, and eliminating contamination of the machined part. Notch wear and flaking near the depth of the cut zone are the predominant types of tool failure during the machining of this kind of material. In comparison to dry machining, the utilization of the cryogenic technique reduces the cutting force to 23%, and improves the surface roughness to a maximum of 88%. This can be attributed to the capacity of LN2 machining to provide better cooling and lubrication through the reduction of heat generation at the cutting zone. The machined surface roughness obtained of less than 0.2µm could fulfill the demands of the aerospace industry for the finishing of precision components.

Design and analysis of energy recyclable bidirectional converter with digital controller for multichannel microstimulators

The power supply modulated microstimulator system can drive an expandable electrode array with reduced heat generation across the current drivers and high stimulation efficiency. Here, we present a comprehensive analytical modelling of the system to investigate internal and external energy flow during biphasic stimulation pulses spanning over varying loading configurations (e.g. number of electrodes, and stimulation current amplitude) that were not covered by existing works on the power supply modulated microstimulators. This paper fills the research gap by presenting the systematic tools for attaining insights of a stimulator system featuring a bidirectional DC---DC converter with an algorithmic digital controller. The models employed here are based on traditional analytical methods such as transfer functions and state-space dynamic models incorporating various circuit elements incurring power loss. With the models, the behaviour and power efficiency under a wide range of parameters associated with stimulator are attained. Numerical assessment reveals that the digital controller can track the output supply voltage at the phase transition boundaries just in tens of switching cycles. The system was also studied on a verification platform, where the internal signals of the digital controller were carefully examined. Measurement results show that the system behavior well matched to the simulation results, demonstrating the effectiveness of the analytical system model for obtaining key insights for generic large-scale micro-stimulator designs.

Investigation on Grindability of Medical Implant Material Using a Silicon Carbide Wheel with Different Cooling Conditions

Zirconia is the preferred material used in many applications including biomedical implant. The zirconia in its sintered form is the most preferred one to manufacture a near net shaped implant material with minimal work. But it is very difficult to shape as the material chip away during the machining or grinding process. Hence zirconia in a pre-sintered form is used to achieve the required shape and size for a specific application. Then it is sintered and used. In this work, the grindability of the presintered zirconia was evaluated using a dense vitreous bond silicon carbide wheel. The grinding parameters such as wheel speed, radial depth of cut and feed rate are varied to investigate its grindability in terms of force ratio, specific energy, surface finish, G-ratio and ground surface under both wet and MQL cooling conditions. The forces produced during the grinding of pre-sintered zirconia was observed lower in the MQL (Minimum Quantity Lubrication) technique due to the reduction of friction, when compared to the wet cooling condition. The calculated specific energy was less in MQL cooling condition, due to the reduction in heat generation and friction. The surface finish of the workpiece obtained from the wet cooling condition was better due to the reduction in wheel loading. The percentage difference of the G-ratio between both the wet and MQL cooling conditions was observed to be 24 percent. This was due to the active participation of grains and less wheel loading in wet grinding condition. The ground surfaces obtained from the wet cooling condition were smooth and regular, compared to the MQL grinding condition.

Thermal Analysis of a Fast Charging Technique for a High Power Lithium-Ion Cell

The cell case temperature versus time profiles of a multistage fast charging technique (4C-1C-constant voltage (CV))/fast discharge (4C) in a 2.3 Ah cylindrical lithium-ion cell are analyzed using a thermal model. Heat generation is dominated by the irreversible component associated with cell overpotential, although evidence of the reversible component is also observed, associated with the heat related to entropy from the electrode reactions. The final charging stages (i.e., 1C-CV) significantly reduce heat generation and cell temperature during charge, resulting in a thermally safe charging protocol. Cell heat capacity was determined from cell-specific heats and the cell materials’ thickness. The model adjustment of the experimental data during the 2 min resting period between discharge and charge allowed us to calculate both the time constant of the relaxation process and the cell thermal resistance. The obtained values of these thermal parameters used in the proposed model are almost equal to those found in the literature for the same cell model, which suggests that the proposed model is suitable for its implementation in thermal management systems.

Optimization of the Thermal Load Profile in District Heating Networks through “Virtual Storage” at Building Level

Thermal storage is of extreme importance in modern district heating networks in order to increase the share of waste heat and heat produced through renewable sources and cogeneration. Nevertheless, installation of large storage volumes is not always feasible, especially in dense urban areas. A possible option consists in virtual storage, which is obtained through variation of the thermal request profiles of some of the connected buildings with the goal of producing an effect similar to that obtained using storage. To perform such approach there are three crucial elements: 1) an advanced ICT solution able provide real time information about the thermal request of the buildings and the thermodynamic conditions at the thermal substations; 2) a detailed thermo fluid-dynamic model of the district heating network able to simulate the temperature evolution along the network as the function of time; 3) a compact model of the buildings in the district able to check the acceptability of the internal temperatures following the modified strategies.The model produces changes in the start-up time of the buildings connected with the network as well as possible pauses during the day. These changes in the request profiles usually involve a slightly larger heat load. Nevertheless, peak shaving is accompanied by a reduction in heat generation of boilers and an increase in the thermal production of efficient systems, such as cogeneration units. This results in a significant reduction in the primary energy consumption.An application to the Turin district heating network, which is the largest network in Italy, is presented. In particular, a subnetwork connecting the main transport network to about 100 buildings located in the central area of the town is considered. The analysis if performed in selected days where the optimization was conducted the day before on the basis of weather forecasts and then applied to the network. Despite the changes in the request profiles could be applied only to a limited number of buildings, the analysis show that the peak request can be reduced. Simulations performed considering the application of changes to a larger number of buildings show that reduction in the primary energy consumptions of the order of 5% can be obtained.

Enhanced Actuation Performance and Reduced Heat Generation in Shear-Bending Mode Actuator at High Temperature.

The actuation performance, strain hysteresis, and heat generation of the shear-bending mode actuators based on soft and hard BiScO3-PbTiO3 (BS-PT) ceramics were investigated under different thermal (from room temperature to 300 °C) and electrical loadings (from 2 to 10 kV/cm and from 1 to 1000 Hz). The actuator based on both soft and hard BS-PT ceramics worked stably at the temperature as high as 300 °C. The maximum working temperature of this shear-bending actuators is 150 °C higher than those of the traditional piezoelectric actuators based on commercial Pb(Zr, Ti)O3 materials. Furthermore, although the piezoelectric properties of soft-type ceramics based on BS-PT ceramics were superior to those of hard ceramics, the maximum displacement of the actuator based on hard ceramics was larger than that fabricated by soft ceramics at high temperature. The maximum displacement of the actuator based on hard ceramics was [Formula: see text] under an applied electric field of 10 kV/cm at 300 °C. The strain hysteresis and heat generation of the actuator based on hard ceramics was smaller than those of the actuator based on soft ceramics in the wide temperature range. These results indicated that the shear-bending actuator based on hard piezoelectric ceramics was more suitable for high-temperature piezoelectric applications.