An indirect estimation of automotive demister performance

Motor vehicle users expect greater comfort and refinement in vehicle performance. Demisting systems are often considered to produce uncomfortable air flows and noisy operation. To prevent the user simply switching off the system and compromising occupant safety, manufacturers are investing more in demisting and climate control to improve detailed performance, whilst maintaining comfort and refinement. An indirect performance estimation would be extremely desirable, using less climatic test facility time and allowing prediction of end performance for a range of conditions An experimental investigation has been carried out to reproduce glass misting in a purpose built environmental facility, at conditions representative of typical car markets. [Continues.

A Numerical and Experimental Investigation of the Effects of Cutting Fluid on Machining Performance

Cutting fluids play an important role in improving machining performance. However, cutting fluids have adverse effects on health and environment. A new methodology has been proposed for the prediction of tool temperature and the experimentally validated methodology revealed that turning operations can be performed with reduced amount of cutting fluid. Followed by, experiments were conducted and the results demonstrated that the reduce amount of cutting fluid is sufficient to obtain acceptable machining performance

Fluorine-hydrogen performance evaluation. Phase I, part I - Analysis, design, and demonstration of high performance injectors for the liquid fluorine-gaseous hydrogen combination Final report

Analysis, design, and demonstration of high performance injectors for liquid fluorine- gaseous hydrogen propellant combinatio

Fire performance of residential shipping containers designed with a shaft wall system

seven story building made of shipping containers is planned to be built in Barcelona, Spain. This study mainly aimed to evaluate the fire performance of one of these residential shipping containers whose walls and ceiling will have a shaft wall system installed. The default assembly consisted of three fire resistant gypsum boards for vertical panels and a mineral wool layer within the framing system. This work aimed to assess if system variants (e.g. less gypsum boards, no mineral wool layer) could still be adequate considering fire resistance purposes. To determine if steel temperatures would attain a predetermined temperature of 300-350ºC (a temperature value above which mechanical properties of steel start to change significantly) the temperature evolution within the shaft wall system and the corrugated steel profile of the container was analysed under different fire conditions. Diamonds simulator (v. 2020; Buildsoft) was used to perform the heat transfer analysis from the inside surface of the container (where the fire source was present) and within the shaft wall and the corrugated profile. To do so gas temperatures near the walls and the ceiling were required, so these temperatures were obtained from two sources: (1) The standard fire curve ISO834; (2) CFD simulations performed using the Fire Dynamics Simulator (FDS). Post-flashover fire scenarios were modelled in FDS taking into account the type of fuel present in residential buildings according to international standards. The results obtained indicate that temperatures lower than 350ºC were attained on the ribbed steel sheet under all the tested heat exposure conditions. When changing the assembly by removing the mineral wool layer, fire resistance was found to still be adequate. Therefore, under the tested conditions, the structural response of the containers would comply with fire protection standards, even in the case where insulation was reduced.Postprint (published version

Experimental Investigation of Fluid Dynamics and Heat Transfer Characteristics of a Turbulent Jet Impinging on an Oscillating Target Surface

This work comprises an experimental study of a turbulent jet impinging on an oscillating target surface. The fluid dynamics and heat transfer characteristics of jet impingement on an oscillating target surface are measured and compared with those of jet impingement on a static target surface. This study shows that target-surface oscillation generates higher turbulence intensities in the impinging-jet flow which give rise to an enhanced heat transfer rate, compared to a static target surface

Heat transfer study of a triple row impingement channel at large impingement heights

Advanced cooling techniques are required to increase the Brayton cycle temperature ratio necessary for the increase of the overall cycle\u27s efficiency. Current turbine components are cooled with an array of internal cooling channels in the midchord section of the blade, pin fin arrays at the trailing edge and impingement channels in the leading edge. Impingement channels provide the designer with high convective coefficients on the target surface. Increasing the heat transfer coefficient of these channels has been a subject of research for the past 20 years. In the current study, a triple row impingement channel is studied with a jet to target spacing of 6, 8 and 10. The effects of sidewalls are also analyzed. Temperature sensitive paint alongside thin foil heaters are used to obtain heat transfer distributions throughout the target and side walls of the three different channels. Thermal performances were also calculated for the two largest channels. It was found that the side walls provide a significant amount of cooling especially when the channels are mounted side by side so that their sidewalls behave as fins. Similar to literature it was found that an increase in Z/D decreases heat transfer coefficient and provides a more uniform profile. It was also found that the Z/D = 6 and 8 target wall heat transfer profiles are very similar, hinting to the fact that successful potential core impingement may have occurred at height of eight diameters. A Computational Fluid Dynamics, or CFD, study was also performed to provide better insight into the flow field that creates such characteristic heat transfer profiles. The Realizable k-µ solution with enhanced wall functions gave surface heat transfer coefficients 30% off from the experimental data

Experimental and Computational Investigation of Ribbed Channels for Gas Turbine Thermal Management

This study focuses on the computational benchmarking as well as validation against experimental results of a rib roughed surface in an internal channel of a stationary turbine blade. STAR-CCM+ was utilized to replace a model from a published article, and to analyze the CFD conjugate heat transfer by determining the turbulence model that best matched the published experimental values. Using those computational conditions and CFD results, an in house experimental rig was validated by comparing convective heat transfer coefficients and pressure profiles. This cooling method, when compared to a smooth channel, enhances turbulent mixing my separating and reattaching the boundary layer which increases the heat transfer. The overall goal is to analyze an effective cooling method, studying the flow physics and effective heat transfer rates as well as minimizing the pressure drop across the channel. V²f turbulence model resulted in matching closest to the experimental results, but doe to its unstable nature at high Reynolds number, the EBk-E model was used for preliminary testing. Results for EBk-E showed shorter reattachment lengths giving higher Nusselt number values between ribs. The heat transfer as well as friction factors match within the uncertainty of 6.8% and 6.6% respectively of the published results. Benchmarked computational results will help validate the experimental setup for further optimization and testing different configurations in rib arrangements

Development and Evaluation of a Novel Supply System to Reduce Cutting Fluid Consumption and Improve Machining Performance

Reducing cutting fluid consumption remains a goal of the machining industry. Despite their reported advantages such as heat dissipation, friction reduction, extended tool life, and improved surface quality, cutting fluids pose several health and environmental concerns throughout their lifecycle, in particular when conventional mineral oil-based, semi-synthetic or synthetic fluids are used. Manufacturers are encouraged to reduce the use of harmful conventional fluids. However, the usage of cutting fluid is still an unavoidable industrial practice, especially when machining titanium alloys, due to the generation of large quantities of heat. High cutting temperature is one of the main reasons for rapid tool wear and hence the poor machinability of titanium alloys. Vegetable oil (VO)-based fluids have been suggested as favourable alternatives to the conventional fluids due to their superior tribological properties and high biodegradability. Several cutting fluid supply systems have been developed to reduce cutting fluid use, such as minimum quality lubricant (MQL) and cryogenic cooling or to control the temperature in the cutting zone, for example flood, and high pressure cooling (HPC) systems, to improve productivity and increase the overall performance of machining processes. Even though process improvements are achieved by these systems, inaccuracies in estimating cutting fluid flow rates, high fluid consumption and low penetrability, as well as high set-up costs, are their technical and economic drawbacks. For these reasons, the need for an innovative supply system to deliver fluids in machining processes has become crucial. In this PhD project, a novel controlled cutting fluid impinging supply system known as ‘CUT-LIST’ is developed to deliver an accurate quantity of cutting fluid into machining zones through precisely-oriented coherent nozzles. The design of CUT-LIST is supported by numerous fluid dynamic and metal cutting theories along with extensive experimentation. The performance of the new system is evaluated against a conventional flood system during the step shoulder milling of Ti-6Al-4V using a water-miscible vegetable oil-based cutting fluid. The effect of cutting conditions on the key measures of the process are investigated, including cutting force, workpiece temperature, tool flank wear, burr formation and average surface roughness (Ra). The effect of CUT-LIST on the micro-hardness and microstructure of the machined surface as well as chip formation are also evaluated. The study shows that the new system provides a dramatic decrease in cutting fluid consumption of up to 42% with noticeable reductions in cutting force, tool flank wear and burr height of 16.41%, 46.77% and 60% respectively. Relatively smaller surface roughness (Ra) values are also found with the use of the CUT-LIST supply system. In terms of the effect of the new system parameters on key process measures, feed rate has a major effect on cutting force, burr formation and surface roughness, with the highest percentage contribution ratios (PCRs) of 47.46%, 38.69% and 39.10% respectively. Meanwhile, the cutting speed has a major effect on workpiece temperature and flank wear, with the highest PCRs of 46.5% and 59.23% respectively. Nozzle position at a 15˚ angle in the feed direction and 45˚or 60˚ against feed direction helped in minimising workpiece temperature. An impinging distance of 55 or 75 mm is also necessary to control burr formation, workpiece temperature, and Ra. Metallurgical observation shows that both systems achieved acceptable micro-hardness values for aerospace components (386.3 to 419 HV100). However, a slight reduction in micro-hardness of ~5.5% was recorded with the use of CUT-LIST. The hardness is lower at distances < 50 μm below the machined surface as a result of thermal softening, while it becomes higher at distances <100 μm from the surface due to cyclic internal work hardening. The micro-hardness then gradually decreases until it reaches the base material’s nominal hardness. Both systems also produce a thin, plastically deformed layer below the machined surface under all conditions investigated. Despite the noticeable reduction in cutting fluid consumption achieved by CUT-LIST, no significant disparity is found in the microstructural subsurface damage caused by the two systems. Microstructural alteration is strongly affected by cutting speed and fluid flow rate. At higher cutting speeds, the conventional system shows visible surface defects such as smearing, surface cavities and erosion in workpiece material. With both systems, desirable discontinued serrated chips are generated. However, the increase in fluid flow rate significantly influences chip morphology, while the average distance between chip segments is more pronounced and evident with the increase in cutting speed. Severe crack propagation (up to a depth of 200 μm) is observed in the chip end free surface, with the use of the conventional system. In addition, CUT-LIST shows decreases of up to 12.5 % in saw-tooth height (hmax) and increased segment width up to 13.63 % at higher speeds, while the transition from aperiodic to periodic serrated chip formation is closely controlled by cutting speed and feed rate. Chip segmentation frequency and shear angle are also found to be sensitive to cutting speed, whilst CUT-LIST provides a larger shear angle compared to the conventional system. Based on the results achieved by CUT-LIST, it is apparent that the new system possesses various advantages over the conventional system. Hence, CUT-LIST can be considered as a feasible, efficient, and ecologically beneficial solution, offering less fluid consumption in machining processes

Modelling of diesel fuel injection processes.

Imperial Users onl

Gas-Liquid Two-Phase Flow in the Pipe or Channel

The main goal of this Special Issue was to contribute to, highlight and discuss topics related to various aspects of two-phase gas–liquid flows, which can be used both in fundamental sciences and practical applications, and we believe that this main goal was successfully achieved. This Special Issue received studies from Russia, China, Thailand, ROC-Taiwan, Saudi Arabia, and Pakistan. We were very grateful to see that all the papers presented findings characterized as unconventional, innovative, and methodologically new. We hope that the readers of the journal Water can enjoy and learn about the experimental and numerical study of two-phase flows from the published material, and share these results with the scientific community, policymakers and stakeholders. Last but not least, we would like to thank Ms. Aroa Wang, Assistant Editor at MDPI, for her dedication and willingness to publish this Special Issue. She is a major supporter of the Special Issues, and we are indebted to her