Search Results (8)

The combustor liner of the modern aero-engine operates under extreme thermal loads with limited coolant supply, necessarily making efficient cooling approaches important. Impingement–effusion double-wall cooling integrates impingement, convection, and film cooling, but most studies testing this approach have been conducted at atmospheric pressure, limiting the application of the technology in real engines. This work experimentally and numerically evaluates the cooling performance of baseline and optimized configurations, focusing on the effects of pressure drop, initial cooling filmand operating pressure under atmospheric and elevated pressures up to 0.3 MPa. The results show that increasing the pressure drop enhances cooling effectiveness, which can be attributed to enhanced jet momentum and cooling film coverage, though benefits diminish when the pressure drop further increases to over 4%. Introducing initial film cooling extends upstream protection, improves downstream uniformity, and stabilizes overall effectiveness across varying pressure drops. Elevated operating pressure further enhances the cooling effectiveness of impingement–effusion cooling, as higher coolant density promotes stronger impingement and more coherent cooling film formation. The simulations confirm that pressure-induced density effects dominate the cooling process, whereas blowing-ratio-based similarity fails to capture these dependencies. The results highlight the limitations of atmospheric evaluations and provide physical insights for designing efficient combustor liners under realistic pressure conditions. Full article

Background: In reverse shoulder arthroplasty (RSA), the neck–shaft angle (NSA) has trended downward from 155° to 135° to reduce scapular notching, but concerns about instability persist. To assess superior–lateral stability, we developed the intraoperative two-hand lever test (2HLT). The primary objective was to evaluate the effectiveness of the 2HLT, analyze the learning curve in this first study reporting on the new Perform stem, and compare the liner characteristics of 155° and 135° systems. Methods: In a single-surgeon learning curve study, 81 RSA procedures with the new Perform stem (Stryker) were included. The outcomes included the 2HLT test applied in 65 cases, early dislocations, stem alignment, stem length, liner type/thickness, and complications. The early dislocation rate was compared to 167 prior Ascend Flex RSA procedures (Stryker). The liner characteristics of three 135° systems (Perform/Stryker, Univers/Arthrex, and Altivate/Enovis) were compared to traditional 155° Grammont systems (Delta Xtend/DePuy, Affinis Metal/Mathys, SMR 150/Lima, and Aequalis Reversed/Stryker), focusing on jump height (JH) and the liner stability ratio (LSR). Results: In 63% (31/49) of the cases, the 2HLT detected superior–lateral instability, necessitating a retentive 135° liner. The early dislocation rate in the Perform cohort was 4.9% (0% for retentive liners, 8% for standard liners) versus 0% in the Ascend Flex cohort. The mean effective NSA was 133° (127–144°) for short Perform stems and 135° (129–143°) for long stems. Long Perform stems significantly reduced varus outlier density below 132° and 130° (p = 0.006, 0.002). The 36 mm Perform 135° standard liner has a JH of 8.1 mm and an LSR of 152%, markedly lower than the Altivate (10.0 mm/202%) and Univers (9.7 mm/193%) and similar to traditional 155° Grammont liners (8.1–8.9 mm/147–152%). Perform retentive liners have LSR values of 185–219%, comparable to the established 135° design standard liners (195–202%). In the Perform cohort, early complications included four superior–lateral dislocations (all standard liners, LSR 147–152%) requiring four revisions. Conclusions: Perform standard liners have a lower LSR than the established 135° designs. Retentive Perform liners (LSR > 184%) are comparable to standard liners of established 135° designs and effectively mitigate instability. We recommend discontinuing non-retentive Perform standard liners (NSA 135°, LSR < 158%) due to the 63% superior–lateral instability rate detected with the novel 2HLT, necessitating retentive liners, the documented LSR-NSA implant mismatch, and an early clinical dislocation rate of up to 8%. Full article

A reverse-flow combustor has a larger liner surface area due to airflow turning, which complicates flow and cooling control, particularly heat transfer efficiency. Effective heat management is essential for maintaining uniform temperature distribution and preventing thermal gradients. This study explores the impact of axial position and diameter of primary holes on thermal performance and flow dynamics. Results indicate that as the primary holes move toward the dome, the recirculation vortex size decreases, leading to insufficient fuel mixing, a reduction in the high-temperature area in the primary zone, and an increase in the high-temperature area of the middle zone. On the other hand, moving the primary holes downstream enhances fuel mixing, increasing high-temperature areas in the primary zone and reducing them in the middle and dilution zones, thus improving thermal boundary layers and convective heat transfer rates. When the primary hole is moved 10 mm downstream, outlet temperature improves significantly with an outlet temperature distribution factor (OTDF) of 0.21 and a radial temperature distribution factor (RTDF) of 0.16. Additionally, reducing the upper primary hole diameter strengthens jet deflection, improving fuel–gas mixing at the dome and heat transfer to the central region. With a 2.1 mm hole diameter, the temperature gradient decreases, resulting in an OTDF of 0.184 and RTDF of 0.15. Furthermore, as the momentum flux ratio increases, the jet penetration depth initially rises and then stabilizes. Momentum flux ratios between 10.6 and 15.1 significantly affect jet penetration, while further increases result in smaller fluctuations. Higher momentum flux ratios create localized high- and low-temperature zones, reducing outlet temperature distribution quality. The optimal momentum ratio for the reverse-flow combustor, ensuring effective jet penetration and better temperature distribution, is between 10.6 and 14.7, with a corresponding penetration depth of 34.3 mm to 35.1 mm. These findings offer valuable insights for improving reverse-flow combustor design and performance. Full article

This study investigates the sustainable use of seabed dredged sediments and water treatment sludges as construction materials using combined dewatering and cement stabilization techniques. Dredged sediments and water treatment sludges, typically considered waste, were evaluated for their suitability in construction through a series of dewatering and stabilization processes. Dewatering significantly reduced the initial moisture content, while cement stabilization improved the mechanical properties, including strength and stiffness. The unconfined compressive strength (UCS), shear modulus, and microstructural changes were evaluated using various analytical techniques, including unconfined compression testing, free–free resonance testing, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results show a direct correlation between reduced w/c ratios and increased UCS, confirming the potential of treated sludge as a subbase layer for roads and landfill liners. A chemical analysis revealed the formation of calcium silicate hydrate (CSH) and ettringite, which are critical for strength enhancement. This approach not only mitigates the environmental issues associated with sludge disposal but also supports sustainable construction practices by reusing waste materials. This study concludes that cement-stabilized dredged sediments and water treatment sludges provide an environmentally friendly and effective alternative for use in civil engineering projects. Full article

Herein, we report a transdermal patch prepared using an ionic liquid-based solid in oil (IL-S/O) nanodispersion and a pressure-sensitive adhesive (PSA) to deliver the macromolecular antigenic protein, ovalbumin (OVA). The IL-S/O nanodispersion and a PSA were first mixed at an equal weight ratio, then coated onto a release liner, and covered with a support film. To evaluate the effect of the PSA, three types of PSAs, DURO-TAK 87-4098, DURO-TAK 87-4287, and DURO-TAK 87-235A, were used to obtain the corresponding IL-S/O patches SP-4098, SP-4287, and SP-235A, respectively. The prepared IL-S/O patches were characterized for surface morphology, viscoelasticity, and moisture content. In vitro skin penetration and in vivo immunization studies of the IL-S/O patches were performed using Yucatan micropig skin and the C57BL/6NJc1 mice model, respectively. The SP-4098 and SP-4287 delivered 5.49-fold and 5.47-fold higher amounts of drug compared with the aqueous formulation. Although both patches delivered a similar amount of drug, SP-4287 was not detached fully from the release liner after 30 days, indicating low stability. Mice immunized with the OVA-containing SP-4098 produced a 10-fold increase in anti-OVA IgG compared with those treated with an aqueous formulation. These findings suggested that the IL-S/O patch may be a good platform for the transdermal delivery of antigen molecules. Full article

To meet the requirements of achieving higher efficiency and lower NOx pollution, the flame temperature in gas turbine combustors increases continually; thus, the effusion-cooling technology has been used to ensure the combustor liner remains within the allowed temperature, by which the combustion characteristics and emission behavior are possibly influenced. In order to investigate the effects of dome cooling air flow on combustion characteristics and NOx emissions, three-dimensional combustion simulations for a swirl-stabilized can-type gas turbine combustor are carried out in this work by using the computational fluid dynamics (CFD) method. Through adjusting the ratio of the dome cooling air flow and the dilution cooling air flow, the characteristics of flow field, temperature distribution and NOx emissions under each work condition are analyzed. At different ratios of the dome-cooling air flow to the total air flow, the flow velocity field in the region near the center of the combustion chamber is not changed much, while the velocity field near the chamber wall shows a more significant difference. The temperature in the outer recirculation zone within the combustion chamber is effectively reduced as the dome cooling air flow increases. By analyzing the distribution characteristics of the concentration of OH*, it is demonstrated that the dome cooling air flow does not have a direct effect on the reaction of combustion. It is also found that as the ratio of the dome cooling air flow to the total air flow increases from 0 to 0.15, the value of the NOx emissions drops from 28.4 to 26.3 ppmv, about a 7.4% decrease. The distribution of the NOx generation rate in the combustion chamber does not vary significantly with the increasing dome cooling air flow. Furthermore, by calculating the residence time in different stages, when the the ratio of the dome cooling air flow to the total air flow varies from 0 to 0.15, the residence time in the pilot stage decreases obviously, from 42 ms to 18 ms. This means that reduction in residence time is the main factor in the decrease of NOx emissions when the dome cooling air flow increases. Full article

After a total hip arthroplasty, a limited range of motion and lower-limb disability continue to be observed, with these being mainly associated with the implant design and the head-to-neck ratio. Larger diameters of the head bearings were assumed to provide better stability, a larger range of motion, and smaller risks of dislocation and stem-to-liner impingement. However, these claims have never been demonstrated in real patients. The specific aim of this study was to assess, via multi-instrumental analysis, whether the range of motion of a replaced hip is limited by the stem-to-liner contact in patients with large femoral head diameters. Twenty-three patients with a total hip arthroplasty were evaluated at their one-year follow-ups using clinical and instrumental examinations. A combined three-dimensional gait analysis of the full body and videofluoroscopy analysis of the replaced hip were performed during the execution of standard, i.e., daily living, and more demanding motor tasks. The latter were meant to reach the extreme range of motion at the replaced hip site, thus revealing possible stem-to-liner contact. An original technique based on imaging and computer-aided design (CAD) models of the prosthesis components was developed to calculate the stem-to-liner distance. Excellent clinical scores were observed in the study. The gait analysis showed that the range of motion of the replaced hip in the sagittal plane, averaged over all patients, ranged from 28° to 78° in standard activities. In more demanding tasks, single peaks were as high as 110°, 39°, and 60° in the sagittal, frontal, and transverse anatomical planes, respectively. In all motor tasks, the stem-to-liner distances ranged from 8.7 to 13.0 mm on average, with one outlier minimum distance being 2.2 mm. This study shows that, even in demanding motor tasks and with an extreme range of motion, the hip joint replaced with large femoral head diameters did not experience impingement between the prosthesis components. Full article

Steam-diluted combustion in gas turbine systems is an effective approach to control pollutant emissions and improve the gas turbine efficiency. The primary purpose of the present research is to analyze the influence of steam dilution on the combustion stability, flame structures, and CO emissions of a swirl-stabilized gas turbine model combustor under atmospheric pressure conditions. The premixed methane/air/steam flame was investigated with three preheating temperatures (384 K/434 K/484 K) and the equivalence ratio was varied from stoichiometric conditions to the flammability limits where the flame was physically blown out from the combustor. In order to represent the steam dilution intensity, the steam fraction Ω defined as the steam to air mass flow rate ratio was used in this work. Exhaust gases were sampled with a water-cooled emission probe which was mounted at the combustor exit. A 120 mm length quartz liner was used which enabled the flame visualization and optical measurement. Time-averaged CH chemiluminescence imaging was conducted to characterize the flame location and it was further analyzed with the inverse Abel transform method. Chemical kinetics calculation was conducted to support and analyze the experimental results. It was found that the LBO (lean blowout) limits were increased with steam fraction. CH chemiluminescence imaging showed that with a high steam fraction, the flame length was elongated, but the flame structure was not altered. CO emissions were mapped as a function of the steam fraction, inlet air temperature, and equivalence ratios. Stable combustion with low CO emission can be achieved with an appropriate steam fraction operation range. Full article