End Wall Research Articles

Multi-mode analysis of surface losses in a superconducting microwave resonator in high magnetic fields.

This paper reports on a surface impedance measurement of a bulk metal niobium-titanium superconducting radio frequency (SRF) cavity in a magnetic field (up to 10T). A novel method is employed to decompose the surface resistance contributions of the cylindrical cavity end caps and walls using measurements from multiple TM cavity modes. The results confirm that quality factor degradation of a NbTi SRF cavity in a high magnetic field is primarily from surfaces perpendicular to the field (the cavity end caps), while parallel surface resistances (the walls) remain relatively constant. This result is encouraging for applications needing high Q cavities in strong magnetic fields, such as the Axion Dark Matter eXperiment because it opens the possibility of hybrid SRF cavity construction to replace conventional copper cavities.

Electroosmotic mixing of non-Newtonian fluid in an optimized geometry connected with a modulated microchamber

The main objective of this work is to enhance the micromixing of different species transported through the electrokinetic mechanism applicable in lab-on-a-chip devices used in BioMEMS. In this process, it is essential to predict the efficiency and precision of the micromixture for the quick and correct mixing. In this paper, a numerical study is conducted to investigate the mixing quantification of the electroosmotic micromixer with a nozzle–diffuser shaped channel connected to reservoirs located at both ends of the channel with a microchamber located in the middle of the channel modulated with an inner rectangular obstacle. Since enhancing mixing quality is the paramount factor, this study examines how the design of the mixing chamber (circular and triangular), the size of the inner obstacle, the conical angle of the nozzle–diffuser channel, and the electric double layer height influence the flow inside the electroosmotic micromixer. Numerical simulations have been performed by using the Poisson–Nernst–Planck based Cauchy momentum equations for a non-Newtonian power-law fluid. This study focuses on both the mixing enhancement and the performance evaluation factor by lowering the pressure drop with variation of geometric modulation. The reservoir end wall effects are considered for the flow rate and mixing of the power-law fluids with variation of different flow parameters. After obtaining the optimal values of the effective parameters used in the micromixers for the experiments, regardless of the geometry of the obstacles, the present model is formulated and validated, and the results are presented. According to the findings, it is observed that the height and width of the inner obstacle, Debye–Hückel parameter, and the slope of the channel have a significant role in the overall mixing quality. The mixing efficiency is improved up to 90% for Newtonian fluid and 96% for shear thickening fluid by using obstacle fitted in the microchamber of the system. In addition, the results demonstrate that shear thickening fluids have better mixing performance than shear thinning fluids, which can be helpful in the fabrication of advanced micromixers.

Revealing the effect of structural components made of sandwich panels on loading the container transported by railroad

The object of this study is the processes of emergence, perception, and redistribution of loads in the supporting structure of a 1CC size container with end walls made of sandwich panels. To reduce the longitudinal load of the container under operational modes, the introduction of sandwich panels into its design is proposed. This solution is implemented on the example of its end walls as the most loaded component of the body in operation. The thickness of the sandwich panel sheet was determined, provided that the strength in operation is ensured. Mathematical modeling of dynamic load of a container with end walls made of sandwich panels placed on a platform car during shunting co-impact was carried out. It was established that taking into account the proposed improvement makes it possible to reduce the dynamic loads that the container perceives by 10 % compared to the typical structure. The results were confirmed by computer simulation of the dynamic load of the container. The models formed within the framework of the study were verified according to the F-criterion. The results of calculations for the strength of the container showed that the stresses in its structure are 15 % lower than those in the typical one. A feature of the findings is that the proposed improvement of the container helps improve its strength in operation by reducing the loads acting on it. The scope of practical use of the results is the engineering industry, namely, railroad transport. At the same time, the conditions for the practical application of the research results are the introduction of energy-absorbing material as a component of the sandwich panel. This study will contribute to devising recommendations for designing modern structures of vehicles of a modular type and for improving the efficiency of the transport industry

Vortex Structure Topology Analysis of the Transonic Rotor 37 Based on Large Eddy Simulation

Highly three–dimensional and complex flow structures are closely related to the aerodynamic losses occurring in the transonic axial–flow compressor. The large eddy simulation (LES) approach was adopted to study the aerodynamic performance of the NASA rotor 37 for the cases at the design, the near stall (NS), and the near choke (NC) flow rate. The internal flow vortex topology was analyzed by the Q–criterion method, the omega (Ω) vortex identification method, and the Liutex identification method. It was observed that the Q–criterion method was vulnerable to being influenced by the flow with high–shear deformation rate, especially near the end–wall regions. The Ω method was adopted to recognize the three–dimensional vortex structure with a higher precision than that of the Q–criterion method. Meanwhile, the Liutex vortex identification method showed a good performance in vortex identification, and the corresponding contribution of Liutex components in the vortex topology was analyzed. The results show that the high–vortex fields around the separation line and reattachment line had high vortex components in the x–axis, the tip clearance vortices presented a high–vortex component in the y–axis, and the suction side corner vortex possessed high–vortex components in the y– and z–axes.

Integration of a transonic high-pressure turbine with a rotating detonation combustor and a diffuser

Abstract In this paper, a diffuser is used to integrate a transonic high-pressure turbine with a rotating detonation combustor (RDC). The paper focuses on the required design modifications to the turbine endwalls (EW) to enable high efficiency, while preserving the airfoil blade-to-blade geometry. The main challenge is the stator passage unstarting, due to the high inlet Mach number. First of all, steady Reynolds Averaged Navier Stokes simulations were performed to compare the efficiency of turbines with constant-radius EWs to turbines with axisymmetric EWs. A modified EW design prevented the unstarting of the stator passage, enabling a significant gain in performance. Afterward, the influence on the turbine efficiency and damping due to the unsteadiness from the diffuser-like fluctuations of the RDC was evaluated with unsteady Reynolds Averaged Navier Stokes simulations with a mixing plane approach (MPA). Full unsteady simulations were carried out on selected inlet conditions and compared to the mixing plane results. This parametric study provides turbine designers with recommended diffusion rates along the vane EWs. Additionally, we provide guidance on the upstream diffuser design, specifically the required damping and outlet Mach number.

Research on Aerodynamic Design of an End Wall Based on a Quasi-3D Optimization Method

To investigate the effects of different passage structures on the aerodynamic performance of the transonic fans, this paper develops a reliable and practical quasi-3D optimization method for the hub based on the experimental data of Stage 67. In the method, the hub profile of Stage 67 can be optimized without changing the geometrical data of the blades. The optimization results show that stream tube diffusion characteristics depend on the hub profile’s curvature in the boundary layer near the hub. In the front part of the hub, the end wall with a concave construction can enhance the expansion of the stream tubes near the root of the rotor blade, which helps control the diffusion flow of viscous fluid effectively to decrease the low-energy fluid’s energy degradation and radial secondary flow in the boundary layer. In the latter part of the hub, the end wall with a convex construction facilitates the shrinkage of stream tubes to decrease the secondary flow loss and separated flow loss by controlling the separation of the boundary layer efficiently. This construction of the hub profile is beneficial to promote the aerodynamic performance of a transonic fan.

On the Effect of Side Clearance in the Vaned Diffuser of a Centrifugal Compressor

AbstractEnvironmental and regulatory pressures have prompted original equipment manufacturers (OEMs) to explore highly boosted internal combustion (IC) engines as a means to minimize toxic air pollutants and meet strict legislative targets. The exhaust gas turbocharger is a key technology used to achieve the boost pressures necessary for advanced engines of the future. Centrifugal compressors with vaneless diffusers have been widely implemented in turbochargers for IC engines, particularly passenger vehicles, primarily due to their compact size and ability to deliver high-pressure ratios over a wide range of flowrates. Methods to improve compressor efficiency near surge without reducing the surge margin have received considerable interest in the past. In many situations, changes to the impeller blade design and/or diffuser are limited by the need to meet the strict engine-rated power target. Such competing demands have encouraged designers to develop variable geometry compressors with the aim of improving near surge performance without sacrificing rated power performance. The on/off-type vaned diffuser is a variable geometry compressor capable of delivering a pressure ratio benefit near surge by utilizing a vaned diffuser rather than a vaneless diffuser. The vanes are retracted prior to the diffuser choking to form a vaneless diffuser in order to reach the engine-rated power condition. Diffuser vane-shaped clearances in the hub or the shroud end wall, termed side clearances, enable axial sliding variability of the vanes into and out of the diffuser passage. Unfortunately, the clearances manifest themselves as a discontinuity in the flow field which gives rise to an efficiency penalty. It is not yet clear how the side clearance geometry and position affect the compressor performance i.e., efficiency and stability. Hence, a numerical and experimental investigation was carried out to determine the impact of side clearance geometry and end wall position on compressor performance. It was found that a side clearance positioned at the shroud end wall reduced the surge margin of the investigated compressor for both types of clearance geometry considered. In contrast to this, a clearance positioned at the hub end wall improved the compressor surge margin but had the lowest efficiency benefit near surge. An experimentally validated Computational Fluid Dynamics (CFD) model was used to inspect the flow field and to elucidate the reasons behind the changes in compressor performance.

Softwood Anatomy: A Review

Although conifers have very homogeneous wood anatomical structure, some of their features allow differentiation of genera or groups of genera. Softwood anatomy is reviewed and the authors have added contributions, grouping features in five blocks (axial tracheids, axial parenchyma, rays, resin canals and mineral inclusions), with special attention to their diagnostic value at the family, genus or species levels. The discussion addresses, in axial tracheids: growth rings, intercellular spaces, pit arrangement, presence of scalloped tori, torus extensions, notches, warty layer, organic deposits, helical and callitroid thickenings, bars of Sanio and trabeculae; in axial parenchyma: presence or absence, arrangement and type of transverse end walls; in rays: composition, type of horizontal and end walls and cross-field pitting; in resin canals: epithelium and the presence of normal or traumatic resin canals; and in mineral inclusions: presence or absence. Wood structure is characterised at the family level, discussing the main elements that can be used for diagnosis at the genus level or in groups of genera.

Numerical investigations of vortex dynamics and loss generation in the corner separation region of a high subsonic compressor blade

Three-dimensional corner separation seriously deteriorates the aerodynamic performance of a compressor blade. In this study, the complicated vortex dynamics and loss mechanism in the corner region of a high subsonic compressor blade (the inlet Mach number is 0.67) are investigated using large eddy simulations (LESs) at a Reynolds number (Re) of 5.6 × 105. The results show that the predicted total pressure loss and outlet flow angle match well with the experimental data, indicating that the LES method can accurately predict the size and strength of corner separation in the compressor blade. With the passage vortex rolling up and further interacting with the low-momentum fluids originating from the end wall boundary layers and the local blade boundary layers, strong shear strain induces a large-scale concentrated shedding vortex (CSV) near the spanwise location of x/H = 0.3. The formation and rolling-up of the CSV not only cause the strongest flow blockage but also strengthen the turbulence anisotropy. As the CSV moves toward the trailing edge, the strong interaction with a pair of counter-rotating vortices shed in the wake region (wake shedding vortex) further accelerates the local generation of turbulent kinetic energy (TKE). Detailed TKE budget analysis shows that the streamwise Reynolds normal stress (w′w′¯) plays the most decisive role in the TKE production term. Furthermore, we demonstrate that the strength of turbulence anisotropy is positively correlated with the TKE budget. Therefore, turbulence anisotropy should be considered carefully in predicting the loss level in the corner region of a compressor blade.

Study of the electric field density distribution in cylindrical chamber with coaxial feed of super high frequency radiation energy

The main design options for supplying SHF energy to the end wall of a cylindrical resonator were considered. 2 types of designs for coaxial feed of energy were selected and optimized, differing in the location of the coaxial line relative to the required direction of wave propagation. As a result of the calculations, the electric fields inside the cylindrical chamber and in the horn coaxial antennas were found, and the SWR of the systems was determined. A comparison in distribution of the electric field when metal objects were placed in the chamber was carried out. The areas of occurrence of a plasma SHF discharge on the surface of a cylindrical object were shown.

Research of thermal and hydrodynamic flows of heat exchangers for different air cooling systems in poultry houses

Increasing the productivity of poultry farms is connected with the need to create an optimal regulated microclimate in poultry houses. This problem becomes of primary importance due to the decrease in the productivity of poultry farming due to the imperfection of the existing systems. The purpose of the study was the development and numerical modeling of a shell-and-tube heat exchanger of a new design for cooling supply air as an element of the air conditioning system used in ventilation systems of various types in the summer period. Two types of ventilation systems are considered, namely tunnel and lateral. For these ventilation systems, heat exchangers designed to cool incoming air in the summer season have been developed. A total of 80 automatic inlet valves measuring 0.3 × 0.85 m were arranged in the side walls. In addition, evaporative cooling systems 5.3 × 1.1 m were located on the front end walls. When considering these two separate systems, the heat exchangers were installed instead of the evaporative cooling system and automatic supply valves. The processes of heat and mass transfer in developed heat exchangers for various types of ventilation systems were investigated. Numerical modeling of hydrodynamics and heat transfer was carried out, as well as analysis of the operation of heat exchangers of two different designs for tunnel and side ventilation systems. Velocity, temperature, and pressure fields in the studied channels were obtained. The conditions of the hydrodynamic flow in the channels of the heat exchangers were analyzed. In the case of the tunnel ventilation system, the pressure drop is 991 Pa, which is 3.3 times less compared to the side ventilation system. The outlet temperature is +23 ℃, which meets the design requirements. The main disadvantage is the financial costs for the purchase, cutting of pipes and, actually, their welding. Both the tunnel and side ventilation systems are quite effective. In order to ensure standardized conditions of the air environment in the poultry house, taking into account all aspects of technical and economic analysis, it is proposed to choose a heat exchanger for the tunnel ventilation system. In practice, such heat exchange devices can be used not only in microclimate systems of poultry houses, but also in the industrial, energy industry and critical infrastructure facilities

Landslide mechanism and stability of an open-pit slope: The Manglai open-pit coal mine

A clear understanding of landslide mechanisms and stability analyses is of great significance for landslide monitoring, prediction, and control. A large-scale end wall landslide occurred and its area reached 47,752 m2 on August 7–20, 2020, in the Manglai open-pit coal mine, China. In this paper, the engineering geological survey, mechanical test, large-deformation finite element numerical method, limit equilibrium method and analytical formula are used to analyze how the groundwater level rise caused this end wall failure and landslide. The engineering geological conditions, hydrogeological conditions, landslide activity signs and physical and mechanical parameter calibration of the sliding mass are investigated in detail and tested. Three-dimensional and two-dimensional numerical models of slopes are established, and an analytical formula calculation method to calculate the factor of safety (FoS) is proposed when sliding cracks are located on the top and toe of a slope. The results indicate that the fault fracture zone, soft strata, continuous heavy rainfall, and groundwater were the main contributors to this landslide. The three-dimensional numerical calculation results are consistent with the deformation and failure process of the slope observed in the field, which shows a retrogressive progressive failure mode. The calculation results of SLOPE/W and the analytical formula are consistent; i.e., when the groundwater level rises to +950, the stability of the end wall reaches the critical stability state. With the passage of time, the creep of the sliding surface accelerates until the entire end wall landslide.

Numerical study of transition process in different zones of a compressor cascade channel

Abstract The complex vortex structure compressor leads to the problem that the transition model is insufficient in predicting the flow instability of the compressor. In this paper, the rectangular cascade of compressor of different turning-angle conditions is taken as the object, and the transition characteristics on the end wall and the blade surface of the compressor cascade are in comparison by the method of large eddy simulation/LES. The effects of the horseshoe vortex and the separation bubble over the compressor cascade on the transition process are emphatically discussed. By analyzing characteristic parameters of the vortex structure, it is found that the separated transitional flow corresponds to multiple separations-and reattachments of the shedding vortex, and is affected by the cross-flow transition and the separate-transition. Finally, by discussing the instability of the separation line, reattachment line and the cross-flow inflection point of the separated transitional flow, it reveals that the transient disturbance caused by the vortex motion is an important reason affecting the prediction accuracy of the transition model.

Optimization Design of Aspect Ratio and Solidity of a Heavy-Duty Gas Turbine Transonic Compressor Rotor

To investigate the influence of blade aspect ratio and solidity on the performance of heavy-duty gas turbine transonic compressors, a multi-objective optimization design platform was built by adopting the blade parameterization method based on the superposition of thickness distribution on the suction surface, the Kriging surrogate model, and the NSGA-II optimization method. The spanwise distribution of solidity and number of blades were the optimization variables. The multi-objective optimization was carried out with isentropic efficiency and stall margin as the objective parameters for the inlet stage transonic rotor of an F-class heavy-duty gas turbine compressor. The results show that the isentropic efficiency and stall margin at design condition with a constant mass flow rate can be improved by 0.96% and 18.7%, respectively, and the total pressure ratio can also increase. The analysis shows that, for regions where the shock wave–boundary layer interaction is obvious, increasing the solidity can reduce the shock wave loss, the shock wave–boundary layer interaction loss, and the end wall loss, and reducing the aspect ratio can reduce the blade boundary layer loss. The spanwise distributions of solidity and aspect ratio determine the stall margin by affecting the radial matching of the load of each blade section. Tip solidity near the tip region needs to be determined according to the pressure field established by the bulk of the flow.

Визуализация эволюции тепловых полей при отражении ударной волны от торца канала ударной трубы

Panoramic thermographic visualization of a non-stationary thermal fields on the rectangular shock tube end wall was carried out. Thermal fields evolution of outer (end wall) surface during shock wave reflection is studied. Heat fluxes distribution data were obtained at various times within 4 seconds after reflection. The influence of the boundary layer on heat transfer behind the reflected shock wave is analyzed.

Long-term follow up of left ventricular remodeling in ST segment myocardial infarction patients after primary percutaneous coronary intervention

Introduction The adaptive reaction known as left ventricular remodeling after ST-elevation myocardial infraction (STEMI) involves both the infarct zone and remote zones, and it lasts for at least 2 years after STEMI. In STEMI patients having primary percutaneous coronary intervention (PPCI), this study was conducted to look at long-term consequences of left ventricular remodeling. Patients and methods Ninety-three patients were successfully treated by primary PCI more than 2 years ago at Assiut University Heart Hospital were enrolled in this study. Detailed history, complete general examination and local cardiac examination were done. Electrocardiography, two-dimensional echocardiography before primary PCI, at discharge and 6 months after PPCI, coronary angiographic and PPCI data from patient admission sheet. Patients were examined by transthoracic 2DE using Phillips ie33 ultrasound system device. Results Thirty-six (38.7%) patients were determined to have left ventricular remodeling when their left ventricular end diastolic volume index increased by more than 20%, compared with 57 (61.3%) patients who did not. Mean age of patients 56.31 ± 11.11 years and mean overall duration of follow up was 3.69 ± 0.45 years. The long-term predictors of left ventricular remodeling were: extensive anterior MI (P < 0.001), left anterior descending as infarct-related artery (P = 0.03), left ventricular end systolic volume index (P = 0.04) and wall motion index (P < 0.001). Discussion Patients who had extensive anterior MI, a wall motion score index more than 1.5, and left anterior descending as infarct-related artery were seen as having a high probability of LV remodeling following PPCI. Only wall motion score index more than 1.5 and extensive anterior MI were independent indicators of LV remodeling following PPCI.

ГОНЧАРНАЯ ПЕЧЬ ПАМЯТНИКА ПЕТРОВКА-5 В КОНТЕКСТЕ АРХЕОЛОГИИ ДАЛЬНЕГО ВОСТОКА

In Primorye, a kiln for firing ceramic material was excavated at the Petrovka-5 monument near the town of Bolshoy Kamen. The furnace occupied the northeastern cape-shaped tip of the hollow slope. The height difference at its location was 1,35 m. The furnace was erected on a flat area paved with broken bricks and baked clay. The furnace had the shape of a truncated circle with a straight end wall on the south side and a furnace on the north. The dimensions of the structure at the base are 2 × 2,3 m, the long side is oriented Northwest–Southeast. The ceiling is made of arched masonry in the shape of a dome. Ceramic vessels and tiles were loaded into the firing chamber through the southern wall. The furnace and the firing chamber were connected by a channel. The walls of the furnace are laid with a horizontal masonry of rectangular bricks 15–20 cm long, 5–6 cm thick. Clay mortar was used as a bundle for laying bricks. By type, the oven belongs to the round one. In ancient times and in the Middle Ages, furnaces of this form were widely used in the North of China. Ceramics deposited in the firing chamber are represented by pots, vases, frying pan lids, tiles. The surface color of the vessels is gray, often specially blackened. The blackening of circular vessels is recorded on the handicraft ceramics of Yin, Wei, the culture of the Amur and Primorye Jurchens, on the monuments of the state of Eastern Xia. Modeling of vessels was carried out on a circle using a bottom-capacitive filling. In shape, the vessels do not find complete analogies among the ceramics of the medieval cultures of Primorye and the Amur region. The technical and technological characteristics of the vessels correspond to the handicraft production of the Far Eastern pottery province, dating back to the traditions of the Han era. Chinese archaeologists correlated the tile material with the periods of the Eastern Jin (317–420) and Eastern Wei (534–550) dynasties. According to radiocarbon analysis of coal from the fire-chamber of the furnace, the monument Petrovka-5 is dated 600–760.

ON INVESTIGATION OF DESIGN DATA PARAMETERS INFLUENCE ON SOFT SHELLS OF REVOLUTION DEFORMING

The work suggests parameter differentiation method using for simplification of numerical investigation of hyperelastic soft shell static deforming problem design data parameters influence on stress-strain state of the shell. Resolving equation system is formulated in vector-matrix form. In contrast to traditional way of nonlinear problem solution continuation parameter choice, given relations are differentiated with respect to design data parameter, which influence on shell behavior is investigated. At this values of shell stress-strain state components values must correspond to some required shell operation condition, coupling investigated initial data parameter with the magnitudes of some characteristics of the shell state. So nonlinear boundary-value problem comes down to a set of interconnected quasilinear boundary and nonlinear initial problem in derivatives of resolving variables with respect to differentiation parameter, and the condition mentioned represents a relation coupling this parameter with the components of resolving variables vector. Solution of obtained set of equation systems is found sequentially by iterative way in the given parameter variation range. As an example influence of neohookean cylindrical shell fixed at end walls radius on maximum values of shell stress-strain state characteristics and their distribution along the meridian is investigated. It is found out that at radius increasing values of shell strains also increase, at this for circumferential and lateral strains there exists some radius value for which these characteristics reach extremum. For large values of cylinder radius increasing length of boundary effect zone is also typical.

Diversity of tracheary elements of Aspleniaceae

Abstract Tracheary elements can be classified as tracheids or vessel elements. In ferns, both cell types and even cells with intermediate characteristics can be observed. For a long time, the methods employed in the study of these cells were questioned and consequently their classification as well. In the present work, we analyze the stem tracheal elements of 13 Aspleniaceae species, occurring in different habitats and belonging to different clades. The samples were cut, dried on a hotplate, metallized, and analyzed in SEM. In general, the Asplenium species analyzed contain elongated conducting cells with oblique end walls, with scalariform thickening on all faces of the cell. The presence of pit membranes, however, varies greatly among species, it being possible to observe species with tracheids, with intermittent perforation plates, and with vessel elements.

THE SEALING CAPACITY AND HEAT TRANSFER CHARACTERISTICS OF A STRAIGHT-THROUGH LABYRINTH SEAL WITH DIFFERENT GEOMETRIC PARAMETERS

The sealing capacity and heat transfer characteristics of the straight-through labyrinth seal with different geometric parameters are analyzed in this paper through numerical investigation. The geometric parameters studied include the gap width varying from 2 mm to 6 mm, the tooth tip thickness varying from 1 mm to 3 mm, and the front inclination angle varying from 75° to 100°. For each case, the Reynolds number is varied from 10,000 to 40,000. According to the results, the sealing performance is mainly influenced by the gap width, and less affected by the tooth tip thickness and the front inclination angle. As the gap width is increased, the discharge coefficient is increased by about 40%. With the tip thickness or the front inclination angle increased, the discharge coefficient is increased by less than 5%. For the heat transfer of the end wall, the gap width has significant effects, while the effects of the other two parameters are mainly in the first tooth cavity. For the stator, the increased flow rate at the tooth tip results in enhanced local heat transfer. For the rotor, the heat transfer is determined by the vortex intensity in the tooth cavity. The presence of small secondary vortices weakens the local heat transfer.