Full Film Research Articles

Numerical study on the effects of inlet swirling direction on the turbine guide vane full film cooling effectiveness

Numerical study on the effects of inlet swirling direction on the turbine guide vane full film cooling effectiveness

Numerical study on the effects of inlet swirling direction on the turbine guide vane full film cooling effectiveness

Numerical study on the effects of inlet swirling direction on the turbine guide vane full film cooling effectiveness

Moving beyond Flow Factors: Modeling Full Film Lubrication with Representative Surface Topography Using Heterogeneous Multiscale Methods

Moving beyond Flow Factors: Modeling Full Film Lubrication with Representative Surface Topography Using Heterogeneous Multiscale Methods

Study on the mixed lubrication of rough planar extrusion considering surface texture

Surface texture plays a crucial role in fluid dynamic lubrication. The non-Newtonian thermal elastohydrodynamic lubrication problem involving rough surfaces with texture has not been investigated to date. In this paper, a model for non-Newtonian thermal elastohydrodynamic lubrication incorporating rough surfaces and texture morphology is developed, focusing on the problem of mixed lubrication in planar extrusion with texture. The model builds upon the Reynolds equation with flow factor introduced. It considers the effects of rough surface texture, thermal effects, and non-Newtonian effects. The Reynolds equation is numerically solved using the Semi-System method to calculate the oil film pressure in full film region and contact pressure in dry contact area. The DC-FFT algorithm is employed to calculate surface elastic deformation. Comparing the calculated friction coefficient of the present model with the measured values in literature experiments, the average error is only 6.94%. Furthermore, the study investigates the effects of texture, temperature, and non-Newtonian on interfacial lubrication performance under mixed lubrication conditions. It’s found that compared to untextured surface, the average film thickness of textured surface increased by a maximum of 10.8%, and the friction coefficient decreased by a maximum of 67.4%; Compared to Newtonian fluids, shear thinning fluids reduce temperature by 0.18%, and shear thickening fluids are more conducive to improving mixed lubrication performance. A stepped pit texture is designed based on the dynamic pressure mechanism of the texture, indicating that the circular stepped pit texture has the best load-bearing capacity improvement.

In vivo recording of visually evoked potentials with novel full diamond ECoG implants

Implantable neuroprosthetic devices such as electrocorticography (ECoG) and intracortical microelectrodes have the potential to restore neurological functions in disabled individuals. They constitute the direct interface with the body and require long term efficiency. We propose an ultra-thin diamond-based implant to tackle challenges related with long term implantation, and demonstrate its functionality on rodents. Here we take advantage of thin-film diamond to generate not only the electrodes but also the thin passivation foil, leading to a full thin film diamond EcoG. Implants were fabricated based on boron-doped diamond (BDD) electrodes connected through titanium nitride (TiN) conductive tracks, all being encapsulated in intrinsic diamond. A complete electrochemical characterization proved that the TiN tracks were well embedded inside diamond and the efficiency of the BDD electrodes. Functionality of the ECoG device was also provided by the recording of classic visual evoked potentials (VEPs) on wild-type mice and rats. This thin film diamond technology successfully responds to long term issues (linked with electrode material or device packaging) and holds the potential to inspire and pave the way for future generations of various electrode arrays.

Growth and properties of full Heusler Co2TiSn epitaxial thin films

Full Heusler Co2TiSn thin film were grown by DC magnetron sputtering on MgO(001) substrates at temperatures from ambient up to 800°C. The epitaxial films with full Heusler structure and high purity were achieved at 700°C with thickness ranging from ∼ 20 nm to over 1000 nm enabling deeper study of the film growth and the effect of the thickness on film properties. The state of films was investigated by wide range of techniques including atomic force and electron microscopy, X-ray diffraction and photoelectron spectroscopy, magnetometry, and magnetooptical ellipsometry supported by ab initio calculation. Structural diffraction study and magnetooptical spectral analysis reveal that under suitable deposition conditions at 700°C almost perfect L21 ordering can be attained with the [100] film direction along diagonal of cubic MgO substrate. Photoelectron spectroscopy indicated the purity of the deposited material and the fourfold symmetry of deposited films in agreement with XRD. The only downside of these films is a relatively high surface roughness as indicated by SEM and measured by AFM. Saturation magnetization at 10 K and Curie point at 370 K was comparable to bulk. The ordering as well as agreement between experimental and calculated Kerr spectra improve with increasing film thickness. In comparison the properties of Co2TiSn are similar to other alloys in the family such as Co2FeSi and Co2FeGa.

Controlling stick–slip in low-speed motion with a lifting force of magnetic fluid

Stick–slip is a standard friction-induced self-excited vibration that usually occurs in the boundary or mixed lubrication regimes. Broadening of the hydrodynamic lubrication regime is conducive to suppressing stick–slip motion. In this paper, the load carrying capacity of a magnetic fluid (MF) film in the presence of a magnetic field is derived based on the modified Reynolds equation. An additional lifting force produced by MF under the magnet was applied between the tribopairs to achieve the full fluid lubrication. Thus, the stick–slip is expected to be inhibited in a lower speed scope. The effect of magnet thickness on the lifting force is investigated experimentally and theoretically. Special attention is given to the influence of the lifting force on the friction and the critical transition speed of the hydrodynamic lubrication regime. Results demonstrate that the lifting force increases with the increment of the magnet thickness. The presence of the additional lifting force expands the hydrodynamic lubrication and makes the critical transition speed move left, as shown by the friction transitions on the Stribeck curve. Therefore, stick–slip motion can be suppressed at a lower sliding speed. Such beneficial effects are more pronounced in thicker magnets. It can be confirmed that, so long as the lifting force is higher than the normal load, the friction will invariably operate in the full film lubrication and the stick-slip motion may be eliminated theoretically.

Understanding the Influences of Multiscale Waviness on the Elastohydrodynamic Lubrication Performance, Part II: The Partial-Film Condition

This paper is the second part of a two-part report studying the responses of a typical point-contact elastohydrodynamic lubrication (EHL) system to multiscale roughness mimicked by wavy surfaces. The wavy surfaces are defined by three key parameters: amplitudes, frequencies, and directions. The previous Part I paper focuses on the full film lubrication condition, while the current paper focuses on the partial film regime where asperity contacts occur. A transient thermal EHL model simulates lubrication problems with different waviness parameters, loads, and speeds. The total number of simulations is 1600. Performance parameters, including the asperity contact ratio, minimum film thickness, maximum pressure, central point film thickness, central point pressure, mean film thickness, coefficient of friction (COF), and the maximum temperature rise, are obtained for each simulation. These performance parameters are post-processed in the same manner as those in the previous Part I paper. The influences of the waviness parameters, load, and speed values on the eight performance parameters are discussed.

Mulching Practices Improve Soil Moisture and Enzyme Activity in Drylands, Increasing Potato Yield

Mulch is an important measure for improving agricultural productivity in many semiarid regions of the world. However, the impacts of various mulching materials on soil hydrothermal characteristics, enzyme activity, and potato yield in fields have not been comprehensively explored. Thus, a two-growing-season field experiment (2020–2021) with four treatments (SSM, straw strip mulching; PMP, plastic film mulching with large ridge; PMF, double ridge-furrow with full film mulching; and CK, no mulching with conventional planting as the control) was conducted to analyze soil hydrothermal and soil enzyme activities and potato yield on the semiarid Loess Plateau of Northwest China. The results indicated that mulching practices had a positive effect on the soil moisture, with SSM, PMP, and PMF increasing by 7.3%, 9.2%, and 9.2%, respectively, compared to CK. Plastic film mulching significantly increased the soil temperature by 1.3 °C, and straw mulching reduced the soil temperature by 0.7 °C in the 0–30 cm soil layers of the whole growth period. On average, SSM, PMP, and PMF increased soil urease activity in 0–40 cm soil layers by 14.2%, 2.8%, and 2.7%, respectively, and enhanced soil sucrase activity by 19.2%, 8.6%, and 5.7%, respectively, compared with CK. Plastic film mulching increased soil catalase activity by 9.6%, while SSM decreased by 10.1%. Mulching treatments significantly increased tuber yield and water use efficiency based on dry tuber yield (WUE), and SSM, PMP, and PMF increased tuber yield by 18.6%, 31.9%, and 29.7%, enhanced WUE by 50%, 50%, and 57.0% over CK. The correlation analysis revealed that soil moisture was the main factor influencing tuber yield (r = 0.95**). Mulching could improve the soil hydrothermal environment, regulate soil enzyme activities, and promote yield increase. As a sustainable protective mulching measure, straw strip mulching is conducive to improving the ecological environment of farmland and the sustainable development of regional organic agriculture.

High-Temperature and High-Pressure Tribological Properties of Siliconized Graphite for Water-Lubricated Thrust Bearing Application in Main Coolant Pump

The effect of the microstructure of siliconized graphite on tribological properties is investigated by using a high-temperature and high-pressure water-lubricated tribometer on a self-mated ring-on-ring configuration under an applied load of 500–1500 N with a spindle speed of 100–5000 rpm in both 90 °C (5 MPa) and 25 °C (1 MPa) water environments, respectively. The Stribeck curves measurement and continuous wear tests are performed and analyzed in both water environments. The wear behaviors of the graphite, SiC, and free-silicon phases in siliconized graphite are demonstrated to explore the wear mechanism. The larger wear depths of a low-worn surface roughness on the three phases contribute to the boundary lubrication. The shallower wear depths are observed on the SiC and Si phases under the mixed lubrication, corresponding to partial contact wear of surface asperities. The wavy surface of the SiC phase and uniform flow-oriented striae of the Si phase are attributed to hydrodynamic lubrication, caused by full water film scouring the worn surface. Finally, an integrated evaluation method of G duty parameters is successfully used to identify the lubrication regimes of siliconized graphite from the boundary, mixed, to hydrodynamic lubrications for a water-lubricated thrust bearing application in the main coolant pump of a nuclear power plant.

Approach to Determine the Limiting Shear Stress of Lubricants at High Pressures Based on Traction Mapping

Typical lubricants behave in a non-Newtonian manner under conditions of high shear and high pressure, as is commonly observed in lubricated rolling/sliding contacts. To optimize and predict the friction therein, knowledge of the high-pressure rheological behaviors of lubricants and limiting shear stress (LSS) is essential. This study developed an approach for determining the LSS of lubricants based on friction mapping of rolling/sliding contacts, using a ball-on-disc traction machine. The main contribution lies in the introduction of a practical approach for the selection of a proper entrainment velocity for determining the LSS, with reduced thermal influences and near isothermal conditions. The proposed approach enables full film lubrication, while keeping the film as thin as possible to prevent excessive shear heating and, thus, thermal effects. The LSS of two lubricants, PAO40 and complex ester, has been measured at pressures ranging from 1.2 GPa to 1.7 GPa. A bilinear model has been used to describe the variation of LSS with pressure. The impact of entrainment velocity selection on the measurement of LSS is also discussed.

Investigation of the effect of combustor swirl flow on turbine vane full coverage film cooling

In response to the challenges posed by aviation engine energy consumption and the imperative to reduce NOx emissions, modern advanced aviation engines have increasingly embraced lean-burn and swirl-stabilized combustion chambers. Consequently, the impact of residual swirl flow at the combustion chamber exit on heat transfer to turbine blades has gained prominence. This study delves into the cooling characteristics and variations under swirling inlet conditions, employing both pressure-sensitive paint (PSP) experiments and numerical simulations. The experiments measured film cooling effectiveness (η) on full film cooling blades across different levels of swirl inflow, while numerical simulations dissected flow patterns under swirling and uniform inflow conditions. The results reveal that the extent of film migration does not exhibit a direct proportionality to the level of swirl intensity. Under low swirl conditions (SN = 0.3), film migration is subtle, resulting in a maximum area-averaged η reduction of 3.0%. Conversely, under high swirl conditions (SN = 0.45), film migration becomes notably pronounced, leading to a maximum area-averaged η reduction of 11.9%. Increasing the coolant flow rate mitigates the migration characteristics, albeit with limited effectiveness. The migration of film on the blade surface of full film cooling blades is partially induced by swirling vortices but is primarily attributed to the migration of the leading edge film. Swirling inflow induces the movement of the stagnation-point line, thereby affecting the distribution of cooling air on the blade surface. Finally, this study proposes a combination of measures as an improvement strategy, including an asymmetric counterflow arrangement for the leading-edge holes, a reduction in the outflow angle of the leading-edge holes, and forward-laidback fan-shaped holes. These improvement measures are anticipated to alleviate film migration, reduce the overall uneven film distribution, and increase the average η across the blade.

Experimental study on the feasibility of alternative materials for tilting pad thrust bearings operating in transition to mixed friction

In hydrodynamic bearings traditional bearing alloys: Babbitts and bronzes are most frequently utilized. Polymer sliding layers are sometimes applied as a valuable alternative. Hard diamond-like carbon (DLC) coatings, which are also considered for certain applications may show some advantages, as well. Although material selection is of secondary importance in a full film lubrication regime it becomes important in mixed friction conditions, which is crucial for bearings with frequent starts and stops. Experimental research aimed at studying the performance of fluid film bearings in the specific operating regime, including the transition to mixed friction, is described in the paper. The tests were carried out on four tilting pad bearings of different material compositions: Steel/bronze, DLC/steel, steel/polyether ether ketone (PEEK), and steel/Babbitt. The tests comprised stopping under load and reproduction of the Stribeck curve by decreasing rotational speed to very low values, and observing the changes of friction force during the transition to mixed friction regime. Analysis of the transition conditions and other results showed clear differences between the tested bearings, illustrating the feasibility of less popular material compositions for bearings operating in specific conditions. More specifically, the DLC/steel bearing was demonstrating superior performance, i.e. lower friction, transition to mixed friction occurring at higher load, and more stable performance at start-stop regime over the other tested bearings.

Diagnosis and root cause analysis of bearing failure using vibration analysis techniques

This paper is presented to diagnose and root cause analysis of the bearing failure. For this purpose, a vibration investigation was carried out on a motor with a 2300 kW power, 1489 rpm speed. Bearing failure was diagnosed by trending and analyzing vibration parameters. By investigating the bearing damage morphologies, a false brinelling pattern was observed. To find the failure cause, the machine was evaluated for two aspects; vibrations and lubrication. The resonance in the fan and the lack of full lubrication film formation were considered root causes of failure. To mitigate resonance, changing the operating speed was considered as a corrective action. By increasing the operating speed (1491 to 1530), the vibration amplitude decreased by nearly 21%. Also, the thickness of the lubricating film was improved by installing an airflow hose. Using this method, the time between failures increased from 3 to 11 months.

Developing a sustainable grease from jojoba oil with plant waste based nanoadditives for enhancement of rolling bearing performance

This paper presents a novel grease from jojoba oil and activated carbon nanoparticles (ACNPs) extracted from banana peel waste. The raw jojoba oil and ACNPs are first characterized for structural properties. Samples of jojoba grease blended with 0.5 and 1.5 wt. % ACNPs are prepared and tested for physicochemical and tribological properties as compared to plain jojoba grease. Adding ACNPs to jojoba grease improves corrosion resistance from grade 2c to 1a while increasing the dropping point from 100 to 109 °C. ACNPs enhanced the viscosity of jojoba oil by up to 33% for testing temperature range of 40–100 °C. The load-carrying capacity of jojoba grease is increased by about 60% when blended with 1.5 wt.% ACNPs. The same blending decreased both the coefficient of friction and the wear scar diameter by 38% and 24%, respectively. A customized test rig is used to test the effectiveness of the grease samples in rolling bearing lubrication in terms of vibration levels and power consumption. The novel jojoba grease proved to show exceptional reductions power consumption reaching 25%. The vibration spectra show the absence of resonant peaks at high frequencies suggesting the capability of jojoba grease to form a stable full film lubrication.

Stabilizing Crystal Framework of an Overlithiated Li1+xMn2O4 Cathode by Heterointerfacial Epitaxial Strain for High-Performance Microbatteries.

To meet the increasing demands of high-energy and high-power-density lithium-ion microbatteries, overlithiated Li1+xMn2O4 (0 ≤ x ≤ 1) is an attractive cathode candidate due to the high theoretical capacity of 296 mAh g-1 and the interconnected lithium-ion diffusion pathways. However, overlithiation triggers the irreversible cubic-tetragonal phase transition due to Jahn-Teller distortion, causing rapid capacity degradation. In contrast to conventional lithium-ion batteries, microbatteries offer the opportunity to develop specific thin-film-based modification strategies. Here, heterointerfacial lattice strain is proposed to stabilize the spinel crystal framework of an overlithiated Li1+xMn2O4 (LMO) cathode by epitaxial thin film growth on an underlying SrRuO3 (SRO) electronic conductor layer. It is demonstrated that the lattice misfit at the LMO/SRO heterointerface results in an in-plane epitaxial constraint in the full LMO film. This suppresses the lattice expansion during overlithiation that typically occurs in the in-plane direction. It is proposed by density functional theory modeling that the epitaxial constraint can accommodate the internal lattice stress originating from the cubic-tetragonal transition during overlithiation. As a result, a doubling of the capacity is achieved by reversibly intercalating a second lithium ion in a LiMn2O4 epitaxial cathode with a complete reversible phase transition. An impressive cycling stability can be obtained with reversible capacity retentions of above 90.3 and 77.4% for the 4 and 3 V range, respectively. This provides an effective strategy toward a stable overlithiated Li1+xMn2O4 epitaxial cathode for high-performance microbatteries.

Interrelationships of entropy production and turbulence kinetic energy associated with simple angle and compound angle full coverage film cooling

The present paper compares experimentally-measured distributions of entropy generation with numerically-predicted distributions of streamwise vorticity, turbulence kinetic energy, and production of turbulence kinetic energy. These comparisons are provided for two full-coverage film cooling environments which are designed to model the thermal management arrangements employed for combustor liners within gas turbine engines. One of these arrangements includes alternating compound angle values of +30° in one row of holes, followed by −30° in the next row of holes. The other arrangement includes simple angle holes with a zero degree compound angle value. The associated full-coverage film cooled boundary layers are investigated within a double-wall cooling test facility wherein the air for each full-coverage film cooling arrangement is provided by an impingement jet array. Experimentally-measured entropy generation values are obtained from film cooled boundary layer measurements of local total pressure variations, obtained in isothermal flow, relative to the freestream values outside of the boundary layer. The resulting entropy generation values quantify second law losses, which are associated with aerodynamic gains. To obtain the associated numerical-prediction results for a steady-state, three-dimensional flow field, employed is the ANSYS FLUENT Version 2022 R2 computational code with a SST k–ω turbulence closure model. The resulting comparisons of entropy generation, streamwise vorticity, turbulence kinetic energy, and production of turbulence kinetic energy are provided for a blowing ratio BR of 2.9 for simple angle film cooling with a main flow Reynolds number Rems of 138,000, and for compound angle film cooling with a main flow Reynolds number Rems of 142,000. Overall, evidence is provided of strong relationships between local turbulence kinetic energy and local entropy production since the two quantities are highly correlated with each other over s substantial range of experimental conditions and configurations. For example, ratio of turbulence kinetic energy to entropy generation data collapse for Z/de values from 0 to 3.5 for Y/de = 0.5, Y/de = 1.5, and both film cooling arrangements. Here, the value of the TKE/Sgen ratio is approximately constant for these conditions, which evidences direct and simple dependences of local turbulence kinetic energy upon local entropy generation, even for lower magnitudes of Z/de. The direct and simple dependences of local turbulence kinetic energy upon local entropy generation are further illustrated by the simplicity of linear correlation equations, which represent physical behavior for different conditions and configurations. These correlation equations are developed for three arrangements, which are associated with X/de = 54.54.

Long-term maintenance of high yield and soil fertility with integrated soil-crop system management on the Loess Plateau

Ridge–furrow with full film mulching has been widely applied to increase crop yield and water productivity on the Loess Plateau, but it may stimulate carbon (C) mineralization. How to integrate other technological benefits based on this technology for long-term maintenance of high yield and soil fertility is a pressing issue. With the local farmers’ practice (FP) as a control, three integrated soil-crop system management (ISSM) practices integrating fertilizer rates, fertilizer types and planting densities (ISSM-N1, ISSM-N2 and ISSM-MN) were established to improve maize yield and soil quality. Compared with the FP, the maize yield increased by 13.34%, 21.83% and 30.24%, and the soil quality index (SQI) increased by 9.66%, 14.91% and 38.38% for ISSM-N1, ISSM-N2 and ISSM-MN, respectively. However, ISSM-N1 did not significantly increase yield, and ISSM-N2 increased residual soil nitrate and decreased nitrogen (N) partial factor productivity significantly. Compared to the FP, ISSM practices increased soil organic carbon (SOC), labile organic C fractions (LOCFs) and potassium permanganate organic C fractions in the topsoil to varying degrees, but only ISSM-MN reached significant levels for most C fractions. The sensitivity index indicated very easily oxidizable C (24.6%), easily oxidizable C (24.7%), hot-water extractable C (30.8%), labile organic C (24.7%) and particulate organic C (57.3%) were more sensitive than SOC (22.7%). ISSM-MN sequestered significantly higher C than the other treatments. The results of the relative importance analysis and the structural equation model indicated that LOCFs were the direct contributors to yield, while recalcitrant C (CO) was the indirect contributor, revealing the underlying mechanism that CO decomposed to replenish LOCFs and the total N pool with the water soluble C pool as the transit station. Overall, ISSM-MN is the most promising strategy to improve crop yield and soil fertility in the long term on the Loess Plateau.

Thermoelastoplastic hydrodynamic lubrication contact analysis of three dimensional rough tooth surface considering micro-scale effect and thermal effect

The contact properties of gear rough surfaces during meshing are influenced by various factors. The analysis of rough surface thermoelastoplastic hydrodynamic lubrication (TPEHL) considering micro-scale effect and thermal effect has not been addressed in the literature. This study establishes a new TEPHL model with multi-factor coupling of thermal field, fluid lubrication, stress-strain, and geometric profile. Based on strain gradient theory (SG), a new thermoelastoplastic material constitutive considering micro-scale effect is developed. Subsequently, the three-dimensional rough surface TPEHL-SG analysis of gear is conducted. The paper investigates the impact of thermal and micro-scale effects on various parameters during the meshing of gear in the full oil film lubrication condition, including surface pressure, oil film thickness, surface temperature, surface deformation, and friction coefficient.

Abstract 13871: Portrayal of Acute Myocardial Infarction in Popular Film

Introduction: The representation of cardiovascular disease (CVD) in popular media plays a pivotal role in shaping public conceptions about CV health. CVD is the leading cause of death among women and disproportionately affects racial/ethnic minority populations in the United States, yet recent national surveys indicate a significant decline in public awareness. Our study sought to investigate the portrayal of acute myocardial infarction (AMI) in popular film. Hypothesis: Portrayal of AMI in film will predominantly show white men exhibiting symptoms of chest pain. Women, racial/ethnic minority populations, and subtle symptoms of AMI will be underrepresented. Aims: To examine 100 full length feature film scenes depicting AMI and evaluate the representation of gender, race/ethnicity, and symptoms. Methods: The 100 most popular films with scenes depicting AMI were identified using the Internet Movie Database (IMDb). Scenes and AMI symptoms were analyzed by cardiologists/cardiology fellows. Gender and race/ethnicity were acquired via movie plots/scripts or via actor self-identification if the former was unavailable. Results: Of the 100 scenes analyzed, 10% depicted women. The representation of people of color was only 6% in contrast to the 94% of scenes featuring non-Hispanic whites. Of the 10 women portrayed, 1 was non-white. The distribution of gender and race/ethnicity for all scenes is shown in Figure 1. The most prevalent presenting symptom observed in 65% of scenes was chest pain accompanied by loss of consciousness. Conclusions: Popular film depictions of AMI appear to be under representative of women and racial/ethnic minority populations. This may be a contributing factor to the inaccurate public perception that CVD does not affect these populations. Film depictions of AMI, which predominantly portray dramatic symptoms of chest pain and loss of consciousness may also perpetuate false beliefs on typical (or even atypical) symptoms of AMI.