Simulation and experimental study of double holes film cooling

In the modern gas turbine, film cooling has been widely used to provide thermal protection for the external surface of the gas turbine blades. Numerous number of geometrical arrangement film cooling have been presented for the past 50 years. The main inspiration of the presented geometrical arrangements film cooling are to minimize the effect of lift off phenomena caused by the formation of the Counter Rotating Vortex Pair (CRVP) which commonly discovered in the Single Cylindrical Hole (SCH) arrangement. In order to reduce the CRVP effects, tremendous efforts from the past researchers have been made including the introduction of the Double Cylindrical Hole (DCH). The present study has made use this DCH along with the employment of several geometrical arrangements including pitch distance (POD), length between holes in streamwise direction (LoD), compound angle and upstream ramp. The evaluation of these parameters involved three different blowing ratios, M and two value of the turbulence intensities, Tu. The diameter of the cooling holes in the present study is 4.75mm which taken based on the previous study. The present study has been divided into two major studies namely experimental study and simulation study. The purpose of the experimental study is to validate the present simulation study which making use of an open end wind tunnel. As the validation process shows a good agreement results, 14 more models have been built and tested using simulation study which the total cases considered are 105. As for the result, all the considered cases of DCH shows improvement in comparison with SCH. Each of the considered geometries and flow parameters have their own effects on the film cooling effectiveness which will be elaborate in details in the further chapter. As conclusion, the simulation is having good agreement with the present experimental study and the previous study which is essential to confirm the reliability of the study. Meanwhile, all DCH shows improvement in term of film cooling effectiveness on each of blowing ratio value

Machining performance of vegetable oil with phosphonium- and ammonium-based ionic liquids via MQL technique

Thermo-mechanical loads are the main factor that influences the tool wear and product surfaces during machining processes. Lubrication in metal cutting is an effective medium to reduce frictional forces and wear on the tool-workpiece interfaces. On this regards, the advantages of using refined bio-based metalworking fluids (MWFs) with the presence of low toxic, biocompatible and oil-miscible ionic liquids (ILs) additives ([N1,8,8,8][NTf2] (AIL) & [P6,6,6,14][(iC8)2PO2] (PIL)) at nominal weight concentrations of 1, 5 and 10% are explored during orthogonal cutting of AISI 1045 steel. Accordingly, the lubricants are supplied via minimum quantity lubrication (MQL) technique and comparative studies are conducted against the performance of the neat modified Jatropha-based lubricant (MJO) and commercially available synthetic ester-based MQL cutting fluid (SE). The combination of mist supply of the MJOs during machining have a great impact on cleaner production that eliminates the excessive usage of fluids and supports the utilization of environmentally friendly chemicals. This work extends the application of a minute quantity of fully miscible ILs in polar vegetable-based MWF which proven to provide a significant improvement on the lubrication effect of the MJO. MJOþAIL10% and MJOþPIL1% showed the best cutting performance amongst all lubricant mixtures with reduction of cutting forces and specific cutting energy by 4 to 5%, cutting temperatures by 7 to 10%, friction coefficient by 2 to 3%, tool-chip contact length by 8 to 11%, chip thickness by 22 to 25%, friction angle by 1 to 2% and increased shear angle by 25 to 29% compared to the SE. Besides, the effect of low friction and reduced cutting forces produced lower specific cutting energy that promotes “greener” and more sustainable working environment

Investigation on the Tribological Behaviour of Modified Jatropha Oil with Hexagonal Boron Nitride Particles as a Metalworking Fluid for Machining Process

Bio-based oil from vegetable oils was recently explored as an alternative solution to petroleum-based oil. However, the application of vegetable oils as metalworking fluids (MWFs) for machining process is still not widespread. The objective of this study was to investigate the tribological behaviour of modified vegetable oils, in comparison with synthetic ester (SE) and crude jatropha oil (CJO). In this study, the CJO was chemically modified via transesterification process to develop modified jatropha oil (MJO5). MJO5 was then blended with the hexagonal boron nitride (hBN) particles at various concentrations ranging between 0.05 to 0.5wt.%. The friction and wear test was performed using four ball tribotester. An experiment on orthogonal cutting process was carried out to evaluate the machining performances in terms of cutting force, cutting temperature, chip thickness and tool-chip contact length. The results reveal that the mixture of 0.05wt.% of hBN particles in the MJO5-based oil (MJO5a) outperformed the SE in terms of friction and wear. MJO5a showed excellent machining performances by reducing the machining force and temperature, which related to the formation of thinner chips and small tool-chip contact length. MJO5a is the best substitute to SE as sustainable MWFs in the machining operation with regards to the environmental and health concern

Tribological performance of modified jatropha oil containing oil-miscible ionic liquid, for machining applications

Modifying physicochemical and tribological properties of a bio-based lubricant is essential in improving its lubrication performances. This paper presents the effectiveness of a fully oil-miscible Ionic liquid (IL) as lubricant additive into a bio-based lubricant. Methyltrioctylammonium bis(trifluoromethylsulfonyl)imide (AIL) was selected as IL additive to improve the tribological performance of the bio- based lubricant. Additive was mixed into the bio-based lubricant at three levels of mass concentrations (1 wt.%, 5 wt.% & 10 wt.%). Tribology tests on steel/steel contacts were conducted to evaluate the lubricant samples. Test outputs were benchmarked against the neat bio-based lubricant. Results revealed good synergistic effect of the AIL additive blended into the bio-based lubricant. MJO+AIL10 % has shown good corrosion inhibition, superior friction reduction (48 %), lower worn surface area (23 %), excellent surface finish (46 %) and increased tapping torque efficiency (8 %). MJO+AIL10 % provided excellent tribological performances which corresponds to the energy saving and environmental benefit for sustainable machining applications

Tribological Interaction of Bio-Based Metalworking Fluids in Machining Process

Metalworking fluids were applied during the machining process to lubricate and cool the machine tool in order to reduce wear, friction, and heat generated. The increasing attention to the environment and health impacts leads to the formulation of eco-friendly metalworking fluids derived from vegetable oils (Jatropha and palm oils) to substitute the use of mineral-based oil. The present work focuses on the performance of refined bio-based metalworking fluids during tapping torque and orthogonal cutting processes. Bio-based metalworking fluids were formulated using 0.05 wt.% of hexagonal boron nitride (hBN) and 1 wt.% of phosphonium-based ionic liquid [P66614][(iC8)2PO2] in a modified Jatropha and palm olein oils and were examined for their rheological properties in comparison with a commercially obtained synthetic ester (SE)-based cutting fluid. The tapping torque performance of the refined bio-based metalworking fluids was evaluated for their torque and efficiency. In addition, the performance of these bio-based metalworking fluids on orthogonal cutting parameters such as cutting force, cutting temperature, chip thickness, tool-chip contact length, and specific cutting energy was highlighted. The results obtained revealed that the rheological properties of the newly formulated bio-based metalworking fluids were improved. From the tapping torque and orthogonal cutting performances, it was proven that the modified palm and Jatropha oils possess good anti-wear and anti-friction behavior compared to SE. In conclusion, the newly formulated bio-based metalworking fluids are suitable for the use as a new advanced renewable metalworking fluid for machining processes that correspond to the energy-saving benefits and environmental concerns

Determination of heat flux intensity distribution and laser absorption rate of AISI D2 tool steel

The prediction of fluctuated temperature distribution generated by pulsed wave laser in laser assisted micro milling (LAMM) is crucial. The selection of processing parameter by minimize the effect on the processing characteristic is decisive to ensure the machining quality is high. Determining the effect of heat generated in underneath surface is important to make sure that the cutting tools are able to cut the material with maximum depth of cut and minimum defects in term of tool wear and tool life. In this study the simulation was carried by using Ansys APDL. In order to confirm the actual and distribution irradiation of temperature from simulation, an experimental was done to validate the results. The experiment was conducted by using Nd:YAG laser with wavelength 1064 nm

Numerical analysis of laser heating for laser assisted micro milling application

The promising processing techniques of micro scale parts are very important in products miniaturization and functions enhancement. Combination of two or more processing techniques gives better processing performance especially when dealing with difficult-to-cut materials. For that reason, the combination of laser beam and micro milling process has been widely studied and proven efficient in reducing cutting force and tool life extension. However, this process needs a precise temperature control in order to eliminate heat effect generated by laser beam irradiation. In this study, temperature distributions are determined numerically to characterize the melted zone and heat affected zone geometry. From the results, the estimation of tool and micro milling cutter distance together with the allowable depth of cut are determined

Performance Evaluation of Palm-Olein TMP Ester Containing Hexagonal Boron Nitride and an Oil Miscible Ionic Liquid as Bio-Based Metalworking Fluids / Amiril Sahab Abdul Sani ...[et al.]

Bio-based lubricants from vegetable oils are seen as a great potential alternative to the ever declining petroleum oil sources. Vegetable oils are highly biodegradable and non-toxic, pose good lubricating properties and do not require high production costs. Palm oils as the main renewable oil sources in Southeast Asia are being widely used as cooking oils. Researches have been conducted to expand their potential usage as lubricants for manufacturing applications. In this study, a chemically modified palm olein trimethylolpropane (TMP) ester (MRPO) containing various additives has been tested for their tribological characteristics. Two types of additives; hexagonal boron nitride (hBN) nanoparticles as solid lubricants and phosphonium-based ionic liquid (PIL) as an oil-miscible liquid additive were added into the MRPO to enhance its physical and tribological properties. Four ball wear tests were performed on steel/steel contacts lubricated with each of the lubricant samples. The experimental results presented improved physical properties as well as good antiwear and antifriction performances of the lubricant mixtures compared to the base oil. A minute quantity of PIL (1 wt. %) and hBN nanoparticles (0.05 wt. %) are found to increase the tribological performance of the MRPO, as well as when they are mixed together as lubricant additives into the base oil. The tribological improvements posed by the MRPO+PIL1% revealed better than or comparable results to the conventional synthetic ester and therefore is seen suitable for the use as a new advanced renewable bio-based metalworking fluid for manufacturing activities that corresponds to the energy saving benefits and environmental concerns

Numerical analysis of laser preheating for laser assisted micro milling of Inconel 718

Micro milling of super alloy materials such as nickel based alloys such as Inconel 718 is challenging due to the excellent of its mechanical properties. Therefore, new techniques have been suggested to enhance the machinability of nickel based alloys by pre-heating the workpiece’s surface to reduce its strength and ductility. The prediction of fluctuated temperature distribution generated by pulsed wave laser in laser assisted micro milling (LAMM) is crucial. The selection of processing parameter by minimize the effect on the processing characteristic is decisive to ensure the machining quality is high. Determining the effect of heat generated in underneath surface is important to make sure that the cutting tools are able to cut the material with maximum depth of cut and minimum defects in terms of tool wear and tool life. In this study the simulation was carried by using Ansys APDL. In order to confirm the actual and distribution irradiation of temperature from simulation, an experimental was done to validate the results. The experiment was conducted by using Nd:YAG laser with wavelength 1064 nm