Compared to conventional Pylon-mounted engines, a 5-15% reduction in aircraft fuel consumption is possible with the use of Boundary Layer Ingestion (BLI) propulsion system. However, this type of ...propulsion system uses a fan that has to operate under continuous inlet distortion and over a wide range of altitude within the flight envelope, which forces researchers to consider the Re effects on the BLI distorted fan stall. For typical spike-type stall, tip leakage flow (TLF) contributes crucially to its generation. Thus, this paper aims to investigate the Re effects on the tip unsteady flow structures under the circumferential distorted inflow near the stall point. In this study, a full-annulus 3D steady/unsteady CFD calculation has been employed to calculate the performance of the NASA 67 transonic fan stage with a 60-deg circumferential distortion at different Re. The results show that the Re effects change the location of peak amplitude of blade tip unsteady flow, without altering the frequency properties. For the further study of the Re effects on the tip unsteady flow, time series analyses of detailed flow structure features and tip leakage vortex (TLV) evolution are performed. At low Re, the angle between the TLF and the axis increases from 77 to 81 deg by comparing the shock structure at 0.99 span, and the secondary flow is enhanced with a marked tendency of blade leading edge spillage. The results indicate that TLV has greater size and strength for low Re condition, and the TLV is more pronounced in the distortion sector than it in the clean sector. Further analysis reveals that the change of shock structure affects the periodic variation in rotor differential pressure on the both surfaces, enhancing the circumferential momentum of TLF near the leading edge, which is the major contributor for changing the vortex structure and causing the stall advance in low Re condition.
•Signal preservation is explored with a reduced-complexity submarine fan model.•Autogenic masking renders longer-period allogenic input signals undetectable.•Shorter-period allogenic input signals ...are preserved.•Topographic noise disrupts but does not obscure autogenic or allogenic signals.•5:1 cycle bundling is produced in this case by purely autogenic processes.
Variations in climate, sea-level and tectonic processes can be recorded in various ways in strata, and recognising and measuring such external signals preserved in strata is an important aspect of deciphering Earth history. Key questions are what type of signals are likely to be preserved; how input signals may be shredded, over-printed or otherwise reduced before preservation, by stochastic or autogenic processes; and how allocyclic products may be mimicked and masked by autogenic processes. A reduced-complexity numerical forward model of down-slope sediment erosion, transport and dispersive deposition of submarine fan strata is the simplest-possible formulation that produces reasonably realistic strata that can be robustly analysed for signal content across model realisations with a range of external forcing amplitudes and periods. Three different initial topographic surfaces that include increasing influence of random noise allow comparison of the signal preserved with different levels of random influence on the deterministic model. Spectral analysis, with rigorous testing for statistical significance, shows that the signal recorded depends strongly on the level of noise present in the underlying topography, that short-period high-amplitude allocyclic signals are the most likely to be preserved in this case, and that autogenic dynamics in the modelled system can effectively mask even long-period high-amplitude input signals because they have similar periodicities. Autogenic processes in this model can also produce 5:1 bundling of cyclical strata commonly assumed to be strong evidence for orbital forcing. This analysis suggests that we might be substantially underestimating the complexity involved in extracting a signal of external forcing from strata where any autogenic processes operate, to the extent that the two different effects may often be practically indistinguishable, indicating that a multiple hypothesis approach is important to account for the resulting uncertainty.
In this study, two different industrial refrigerators were designed, manufactured and tested to analyze the impact of different types of fans (Type 1 and Type 2) used in industrial cooling systems on ...the performance of the cooling system. In order to test the fan performance and airflow effects, two axial fan configurations with different structures and different motor technology (EC and shaded-pole induction) were tested in two separate industrial refrigerator test rooms in accordance with TS EN ISO 23953-2 standards. R290 (Propane) was used as a refrigerant in the systems. The average temperature and relative humidity values of the environment where the experiment was conducted were measured as 25 °C and 60 % (Class 3), respectively. During the experiments, the total of 51.71 kWh energy was consumed in system 1, while the total of 54.22 kWh energy was consumed in system 2 and the difference between the energy consumption of the two systems was calculated as 4.85%. The average temperatures of the inlet and outlet of the evaporator of the system 1 and 2 were -21.57 °C, -18.97 °C and -23.43 °C, -20.94 °C, respectively. The average refrigerant temperatures for the system 1 and 2 were calculated as -24.65 °C, -26.44 °C, respectively. While the average coefficient of performance value of the type 1 system was 1.74, it was calculated as 1.54 for the type 2 cooling system. The average second-law efficiencies for the two cooling systems were calculated as 30.85 % and 29.81 %, respectively. In addition, the environmental economy analysis was carried out using the amount of CO2 that was prevented from emitting and the CO2 emission price calculated accordingly.
Bu çalışmada, endüstriyel soğutma sistemlerinde kullanılan farklı tip fanların (Tip 1 ve Tip 2) soğutma sisteminin performansına etkisini analiz etmek için iki farklı endüstriyel buzdolabı tasarlanmış, üretilmiş ve test edilmiştir. Fan performansını ve hava akış etkilerini test etmek için farklı yapılarda ve farklı motor teknolojilerine (EC ve gölge kutuplu indüksiyon) sahip iki adet aksiyal fan konfigürasyonu, TS EN ISO 23953-2 standartlarına göre iki ayrı endüstriyel buzdolabı test odasında test edilmiştir. Sistemlerde soğutucu akışkan olarak R290 (Propan) kullanılmıştır. Deneyin yapıldığı ortamın ortalama sıcaklık ve bağıl nem değerleri sırasıyla 25 ° C ve % 60 (Sınıf 3) olarak ölçülmüştür. Deneyler sırasında 1. sistemde toplam 51.71 kWh enerji tüketilirken 2. sistemde toplam 54.22 kWh enerji tüketilmiş ve iki sistemin enerji tüketimi arasındaki farkı % 4.85 olarak hesaplanmıştır. Sistem 1 ve 2'nin buharlaştırıcısının giriş ve çıkışının ortalama sıcaklıkları sırasıyla -21.57 °C, -18.97 °C ve -23.43 °C, -20.94 °C’dir.Sistem 1 ve 2 için ortalama soğutucu akışkan sıcaklıkları sırasıyla -24.65 °C ve -26.44 °C olarak hesaplanmıştır. Tip 1 sistemin ortalama performans katsayısı değeri 1.74 iken, tip 2 soğutma sistemi için 1.54 olarak hesaplanmıştır. İki soğutma sistemi için ortalama ikinci kanun verimleri sırasıyla % 30.85 ve % 29.81 olarak hesaplanmıştır. Ayrıca emisyonu önlenen CO2 miktarı ile çevre ekonomisi analizi yapılmış ve buna göre CO2 emisyon fiyatı hesaplanmıştır.
The internal water and thermal state and performance of an air-cooled proton exchange membrane (PEM) fuel cell stack are strongly determined by the fan arrangement and operational characteristics. ...This study presents an innovative method to investigate the influence of fan on stack performance through integration of fan’s full morphology, including the fan blade, grill between the fan and stack, etc. into a three-dimensional (3D) multiphase stack model. The multiple reference frame (MRF) model is implemented to simulate the air flow field caused by the rotation of fan and the multiple transfers coupled with electrochemical reactions is considered in the 3D stack model in detail. Through this integrated model, the influence of the air supply mode, fan number and duty ratio on stack performance and the distribution characteristics are investigated in detail. It is found that the air flowing into each cell in the fan-cooled stack is highly non-uniform, which increases the variations of oxygen concentration, temperature, and voltage in the stack. In comparison with the blowing mode, the suction mode helps to promote the uniformity of air supply with a lower air flow velocity.
Thermal comfort prediction with physiological parameters has been getting increasing attention due to the advances in wearable sensing technology. Previous studies in chamber and air-conditioning ...environments indicate that physiological parameter-based group and personal comfort models can predict thermal comfort accurately. To demonstrate whether physiological signals are reliable indicators for thermal comfort prediction in fan-assisted cooling environments, a series of experiments were conducted to collect participants’ physiological and thermal responses in a mixed-mode fan-assisted cooling environment in tropical Singapore. Group models and personal comfort models with different machine learning algorithms were then developed. The results show that the accuracy ranges of group thermal comfort models based on all measured physiological features for thermal sensation vote, thermal preference, and air velocity preference predictions are (62.4%, 73.3%), (74.5%, 82.2%), and (67.8%, 77.7%), respectively. For personal comfort models (PCMs), PCMs with all physiological features as inputs have a median accuracy/Area Under the Curve (AUC) of 82.0%/0.92, 84.5%/0.92, and 80.7%/0.91 for TSV, TP, and VP prediction, respectively. Additionally, personal comfort models based on four groups of input features were developed and compared to explore the feasibility of using fewer physiological parameters to predict thermal comfort. Finally, this study demonstrates that only using two skin temperatures from wearable body parts can predict thermal comfort accurately in fan-assisted cooling thermal environments.
•Long-term experiments were conducted in a mixed-mode fan-assisted cooling room.•Non-contact experiments were designed and carried out during the COVID-19.•Group and personal comfort models using physiological parameters were developed.•Personal comfort models using a few physiological parameters were developed.
This review makes four contributions to the sociological study of sports fans, alcohol use, and violent behavior. First, this article focuses explicitly on the relationship between alcohol use and ...violent behavior among sports fans. This is a worldwide social problem, yet it is quite understudied. Second, this article synthesizes the fragmented literature on alcohol use and violent behavior among sports fans. Third, this article identifies four broad sets of risk factors—sociocultural, event/venue, police, and crowd—that appear to be closely related to violent behavior among sports fans. Finally, to help explain the possible correlation between alcohol and violence among sports fans, this article draws upon the key understandings from the literature on alcohol and violence in wider society. The article concludes with suggestions for future research.
•The effect of compound angle of fan-shaped holes on film cooling effectiveness and flow structures was numerically investigated using large eddy simulation approach.•The laterally-averaged and ...area-averaged cooling effectiveness were decreased by increasing the compound angle at lower blowing ratio.•At higher blowing ratio, by increasing the compound angle, the cooling performance also was increased.•Analysis of the turbulent statistical Reynolds stress revealed that by increasing the compound angle, the turbulence fluctuations were increased in all direction.
Large eddy simulation (LES) was utilized to investigate the influence of applying various compound angle (CA), on film-cooling effectiveness and turbulent flow structures. The baseline cooling hole was a 7-7-7 laidback fan-shaped hole, where this hole is located at a flat plate surface with a pitchwise spacing of 6D, and the hole was inclined at 30-degrees with respect to the mainstream hot-gas flow. Five different cooling hole orientations (CA0, CA15, CA30, CA45 and CA60) were numerically simulated using a constant density ratio of 1.5 and two blowing ratios (M = 1.0 and 3.0). The time-averaged computational results for the thermal and flow fields were validated by comparison with experimental data from previous literature. The simulation results revealed that under a low blowing ratio (M = 1.0), cooling performance was not affected significantly by the compound angle, but at the higher blowing ratio there was a considerable improvement of 40% for the CA60 hole over the CA0 hole, this improvement was especially pronounced in the lateral direction. The vorticity-field investigation showed that as the compound angle increased, the magnitude of the streamwise vorticity also increased while it becoming more asymmetric. In addition, time-space evaluation and spectral analysis of the velocity fluctuations indicates higher unsteadiness and greater turbulent statistics when using holes with larger compound angles.
While Ediacaran cap dolostones research is a hot topic, detailed sedimentological analysis of barite‐bearing cap dolostones remains scarce. Here, new data are presented from Xiangerwan in northern ...Three Gorges, South China, to illustrate the sedimentary characteristics, depositional environment and formation mechanism of the barite‐bearing cap dolostone. In ascending order, the succession is divided into: (i) pebbly dolostone; (ii) dolostone with unusual sedimentary structures (for example, sheet cracks and tepee structures); and (iii) barite‐bearing facies. The gravels of the pebbly dolostone record the slow relative sea‐level rise during post‐glacial transgression, with a local terrestrial influence. Sheet cracks and tepee structures represent water escape structures in the supratidal and upper intertidal zone, and gently wavy stromatolites in barite‐bearing facies are deposits typical of the upper intertidal zone. In addition, primary radial length‐slow dolomite cements were originally precipitated at the seafloor. In general, the cap dolostone was formed in a shallow‐water ramp environment. The form and sedimentary characteristics of barites indicate a primary (syngenetic) origin and help to divide the barites into bladed (Type I) and needle‐like (Type II) variants. With the ongoing melting of the Marinoan glacier and water density stratification, the cap dolostone was gradually precipitated, accompanied by exotic gravels input. The stratification persisted, and special sedimentary structures were widely developed. Phosphorus and barium ions were brought up from the deep basin by upwelling, indicated by the flourishing stromatolites and barite fan deposition. Above the sediment–water interface, the Type I barite first grew upward from substrates, then the Type II barite could grow either in the reverse ‘V‐shape’ cavities between and within the Type I barite clusters, forming rhythm layers with bedded dolomite, or scattered in the laminae of stromatolites or surrounding dolomite. Finally, the formation of barite fans indicates the end of cap dolostone deposition and deeper water sedimentation.
Modern gas turbines require the use of external film-cooling techniques to effectively cool the turbine blades, which are heated by hot combustion gases. Large eddy simulation (LES) is conducted to ...numerically evaluate the influences of trench configurations on film-cooling effectiveness and flow-field behavior of a shaped hole. The cooling hole was a laidback fan-shaped hole with a 17.5-degree forward expansion angle located on a flat plate surface with a 30-degree injection angle at a constant blowing ratio of 2.0 and a constant density ratio of 1.5. The computed film-cooling effectiveness was validated with that obtained in the experimental data for the reference case at two blowing ratios. Two geometrical parameters of the trench height and width were selected as design variables, and overall area-averaged film-cooling effectiveness was considered as an objective function. The Latin Hypercube sampling (LHS) method was applied to generate the designed cases and two different optimization algorithms, the response surface methodology (RSM) and the Kriging method, were employed to maximize the objective function. The computational LES results revealed that trenched cases with a larger trench height and a relatively smaller trench width improved cooling performance. The optimal trench configurations based on the RSM and Kriging method, demonstrated improvements in cooling performance by 27% and 25%, respectively, compared to the reference case without a trench slot. The transient analysis also showed that the flow unsteadiness and velocity disturbances near the trench exit at the mixing region were weakened for the cooling holes with the optimal trench cases.
•The effects of trench configuration applied in shaped cooling holes on cooling effectiveness were investigated.•The LHS DOE method was selected, and RSM and Kriging algorithms were used to optimize the cooling performance.•In general, increasing the trench height and decreasing the trench width, increased the cooling performance.•The RSM and Kriging optimal cases improved the overall cooling effectiveness by 28% and 26%, respectively.
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