Internal Loss Research Articles

Study on external performance and internal flow characteristics in a centrifugal pump under different degrees of cavitation

Cavitation as a form of unsteady flow within centrifugal pumps can cause the reduced performance of pumps, disordered internal flow regimes, and flow loss. The present criterion used for determining the occurrence of cavitation is a 3% head drop. However, in most cases, pump cavitation already occurs with less than a 1%–2% head drop due to significant changes in the internal flow status. To examine changing patterns in internal flow characteristics as the degree of cavitation deepens in the early stage of cavitation in centrifugal pumps when the head curve does not show significant fluctuation, this paper focuses on a low specific speed centrifugal pump to analyze distributions of total internal pressure, speed, bubble volume, vortex structure, and entropy generation across different degrees of cavitation and obtain internal flow characteristics and flow loss patterns of pumps, with an aim of providing preferences for anti-cavitation hydraulic design of centrifugal pumps.

On the question of the smallest rolling resistance coefficient value of elastic wheel on a rigid horizontal surface

As is known, rolling resistance of an elastic wheel on a rigid support surface is determined by internal friction losses (hysteresis) in the wheel material and friction losses in the contact of wheel with support surface (friction losses in the hub bearings and aerodynamic losses are neglected due to their smallness compared to with the above). To assess rolling resistance, the rolling resistance coefficient is used, which is defined as ratio of rolling resistance force applied to the wheel axle to the normal reaction on the wheel. Its value can be determined experimentally or by analytical dependencies. In this article, an analytical derivation of equation for calculating rolling resistance coefficient is given, followed by determining conditions under which this coefficient will be minimal.

Experimental and analytical method for determining specific losses in the presence of a surface effect

In this article, based on the accumulated experience of determining the intensity of the internal loss function in the active nodes of electromechanical devices, an experimental and analytical method for determining this intensity in time by the coordinates of the area under study is proposed. The error in determining the intensity of internal losses is determined based on comparing the results of calculating the integration of two variants of the two-dimensional heat equation.

Energy efficiency optimization of water pump based on heuristic algorithm and computational fluid dynamics

Abstract To reduce the energy consumption of large centrifugal pumps, modified heuristic intelligent algorithms are used to directly optimize the diffuser of centrifugal pumps. Considering the hydraulic efficiency under the design condition as the optimization target, in this study, 14 geometric parameters such as the inlet diameter, outlet diameter, and leading and trailing vane angles of the diffuser are selected as design variables, and the modified particle swam optimization and gravitational search algorithm are used to directly search for optimization in the design space. The performance and loss of internal entropy production of the different models before and after optimization are compared and analyzed in detail. The results show that the global optimization ability of the modified algorithm is improved. The diffuser model changes from cylindrical to twisted, the vane wrap angle increases, and the thickness of the leading edge decreases. Under the design condition, the efficiency of modified particle swarm optimization algorithm solution is increased by 2.75% and modified gravitational search algorithm solution by 2.21%, while the power remains unchanged. Furthermore, the optimization solution has the largest lift efficiency improvement under part-load conditions. After optimization, the unstable flow in the model is improved and internal entropy production loss is reduced significantly. The interior of the diffuser is dominated by turbulent entropy production and direct entropy production under different operating conditions, and the wall entropy production accounts for the smallest proportion.

Lewis acidic molten salts etching route driven construction of double-layered MXene-Fe/carbon nanotube/silicone rubber composites for high-performance microwave absorption

Transition metal carbide/nitride (MXene) materials have triggered intensive research interest in the field of microwave absorption (MA). However, the complicated fabrication process and monotonous loss mechanism of MXene materials seriously hinder their practical applications. Here, we first developed a green and facile synthesis of dielectric-magnetic MXene-Fe nanocomposites via one-step Lewis acidic molten salts etching, which were combined with carbon nanotube (CNT) filler and silicone rubber (SR) matrix to fabricate double-layered MXene-Fe/CNT/SR composites by casting and curing. The in-situ growth magnetic Fe nanoparticles on MXene and unique double-layered structure composed of MXene-Fe/SR as the upper absorption layer and CNT/SR as the bottom reflection layer imparted the composites with excellent MA properties by offering appropriate impedance matching, strengthened internal reflection, polarization, magnetic loss, and conductive loss. Accordingly, the proposed double-layered composites showed superior MA properties compared with other MXene-based composites. The MXene-Fe-45%/CNT-5%/SR sample showed a reflection loss value of −65.9 dB at 12 GHz and an effective absorption bandwidth up to 8.24 GHz at 2.86 mm thickness. The double-layered composites exhibited tunable absorption frequency between the whole Ku-band and X-band by simply regulating the sample thicknesses and filler contents. These features indicate that the developed double-layered MXene-Fe/CNT/SR composites have great potential for high-performance MA applications. This study offers a novel and simple strategy to develop high-efficiency and broadband MA materials.

AN OPTIMIZED MOUSE PARABIOSIS PROTOCOL FOR INVESTIGATION OF AGING AND REJUVENATIVE MECHANISMS

Abstract Surgical parabiosis is widely used to study the mechanistic influence of the circulating milieu on aging and regeneration. This powerful model presents diverse complications based on age, strain, sex, and other experimental parameters. In young (Y) and old (O) male and female C57BL6 mice, we optimized heterochronic (n=12) and isochronic (n=10 Y-Y, n=7 O-O) parabiosis. Throughout protocol development, we identified several complications including variable responses to anesthesia, external and internal dehiscence, dehydration, and weight loss. We identified and implemented solutions during surgical and post-surgical periods, including titrated anesthesia, reinforced internal sutures, topical agents to promote wound healing, and increased supplementation. By consistently adopting protocol changes we were able to significantly increase survival. Separately, we confirmed the time course of chimerism in heterochronic pairs of C57BL6 and Tg(act-EGFP)Y01Osb (eGFP) mice. Baseline and longitudinal blood samples were collected via tail vein. Flow cytometry was used to visualize GFP-positive cells from the parabiont blood sample. Through blood analysis we found that chimerism occurs as early as 2 days post-operatively. Exploitation of our optimized protocol may enable others to efficiently adopt the surgical parabiosis model to dynamically study mechanisms of aging and regeneration.

Evaluating energy loss with the entropy production theory: A case study of a micro horizontal axis river ducted turbine

Hydrokineticpoweras acleanrenewableenergy has been aroused awidespread concern. Horizontal axis turbines are widely used in the field of tidal and river current energy power generation, but their internal flow loss characteristics have not been fully revealed. In this paper, a micro horizontal axis river ducted turbine is taken as the research object, and the flow loss characteristics of the turbine under different yaw angles and tip clearances are analyzed by numerical simulation method combined with entropy production theory. A detailed entropy production analysis shows that most of the energy losses take place near the blade tip, at the outlet of the duct, and in the downstream wake region. The turbulent dissipation is the main cause of entropy generation in the ducted turbine. Results demonstrated that with the increase of the yaw angle, the power coefficient Cp increases first, and then reduces. The Cp is up to maximum at θ = 10°. When θ = 25°, the maximum value of Cp decreased by 24.8%, compared with θ = 10°. It is also suggested that there is no obvious negative effect to shaft work and power coefficient for ducted turbine under certain yaw environment (θ ≤ 10°) and the optimal tip clearance should be between 0.02D and 0.04D.

Using smart meters data to model customer water consumption and evaluate customer flow patterns

ABSTRACT The correct determination of water consumption is key to increasing hydraulic modeling reliability. In this context, Smart Metering (SM) is an important concept. The SM systems can provide consumption at a customer level and in small intervals of time. In this scenario, the work focused on a residential condominium, in Brazil, where an SM system was implemented. The work uses data obtained to model consumers’ water consumption and proposes a system to detect metering failures and internal water loss. Three models were proposed: one uses Autoregressive Integrated Moving Average (ARIMA) theory, another uses the Seasonal Autoregressive Integrated Moving Average (SARIMA), and the last uses multivariate linear regression. The average root mean square error of the first model was 14,73, of the second was 13,50, and of the third was 20,99. A metering and consumption system, able to detect internal leaks and others, was also developed.

Coupling Performance Enhancement of GaSb-Based Single-Transverse-Mode Lasers with Reduced Beam Divergence Obtained via near Field Modulation

Symmetric narrow waveguide structure has been developed and fabricated to achieve low beam divergence and improved coupling performance of the 1.95 μm GaSb-based single-transverse-mode diode lasers. The near-field expansion effect of the narrowed 150 nm vertical waveguide design leads to a reduced fast-axis beam divergence of 44.2° full width at half maximum (FWHM) as well as 62% single-mode fiber (SMF) coupling efficiency, which has 55% relative promotion compared to the 40% efficiency of the conventional 270 nm waveguide design with 60.4° FWHM. The highest SMF coupling power of 113 mW was obtained by the 210 nm narrow waveguide lasers with lower internal optical loss at a 55% coupling efficiency, which performed balanced optimal performance with a narrowed divergence of 53.4° and a relatively high optical power of 206 mW. The high coupling efficiency and power will provide more promising prospects for the GaSb-based single-transverse-mode lasers in the widespread fiber-based and external-cavity applications.

Characterization of Electrochemical Behavior for Aqueous Organic Redox Flow Batteries

Use of aqueous redox flow batteries with organic redox-active materials holds great promise for large-scale and sustainable energy storage. The development of low-cost, highly efficient aqueous redox flow batteries lies in a comprehensive understanding of the electrochemical behaviors of redox-active compounds. An alkaline redox battery with organic dihydroxyphenazine sulfonate (DHPS) anolyte and ferro-/ferricyanide (Fe(CN)6) catholyte is investigated as a typical example of aqueous redox flow batteries using organic redox-active materials. The electrochemical kinetics of DHPS and Fe(CN)6 are separately characterized using the symmetrical cell design. The resistance components are calculated directly from the experimental measurement. The key kinetic parameters are extracted and compared for DHPS and Fe(CN)6 electrolytes. The extracted parameters are validated with symmetrical and full flow cell simulations at different operating conditions. Key parameters and internal loss are also compared with all-vanadium redox flow batteries, representing current state of the art. In addition, our extracted key parameters from a symmetrical flow cell are compared with the measured key parameters by cyclic voltammetry, a widely deployed electroanalytical technique. The cell performance prediction of DHPS anolyte on a 780 cm2 interdigitated cell is made and found the power density is peaked at 475 mW cm−2 at our measurement condition.

Experimental and simulation approach of cooling system in 3-phase inverter using extended surface

Overheating is a failure mode that significantly affects the reliability of electronic devices. All electronic devices, including a 3-phase inverter driving a traction motor, produce heat dissipation. Heat dissipation needs to be controlled with cooling to prevent overheating. Overheating can be avoided by increasing cooling or reducing heat dissipation. Heat dissipation in the 3-phase inverter is caused by the internal resistance of the metal–oxide–semiconductor field-effect transistor (MOSFET), switching loss, and other factors. Cooling for the 3-phase inverter can use water coolant or air coolant. The cooling system is based on the amount of heat dissipation produced. Cooling of a 3-phase inverter can use air coolant with the addition of an extended surface area in the heat sink. The heat sink uses aluminum material, often called pin fin. There are kinds of aluminum available in the market. We calculated heat generation based on the MOSFET's internal resistance, switching loss, and other factors. We validated the simulation results experimentally using a thermal camera. Thus, we could find an optimal number, dimensions, and aluminum type of fin for the cooling system in the 3-phase inverter.

Electrochemical Impedance Spectroscopy study on ammonia-fed Solid Oxide Fuel Cells

The use of ammonia as a fuel is one of the promising pathways to decarbonize the energy sector. When ammonia is converted into power in the so-called “Ammonia-to-Power”, the most interesting technology is the Solid Oxide Fuel Cell (SOFC) that can operate directly with ammonia and reach high performance in terms of efficiency. SOFCs are a high-efficiency and, potentially, low-cost technology, but still suffer from degradation issues related to internal losses. An innovative experimental technique to evaluate losses evolution caused by degradation is electrical impedance spectroscopy (EIS), followed by measurement data post-processing through the Distribution of Relaxation Times (DRT) analysis. In this study, a single SOFC is studied with a combined EIS and DRT methodology, when operating with a gas mixture of hydrogen, nitrogen and ammonia. The results identify the contribution to DRT of fuel dilution and the internal ammonia decomposition reaction.

Experimental Investigation on the Heat Dissipation and Postfire Structural Performance of a Reinforced Concrete Column with Biomimicked Geometry

Cactus plants are prevalent in hot terrain locations. The spines in the cactus plants have an important function in preventing water evaporation. The strong pointed spines serve to distribute heat and prevent internal moisture loss owing to high heat. This paper addresses the biomimicking of a cactus plant to a reinforced concrete column. Columns are one of the most predominant elements in a structure and are responsible for maintaining the stability of the structure. Under the occurrences of fire, columns are the most affected, and the failure of the same could eventually steer to global collapse of the structure. In this study, various geometries were adopted based on the cactus plant, and the heat dissipation characteristics were studied. Finite element analysis was used to determine the optimal form based on the heat dissipation. The optimized shape was tested experimentally using a high-temperature localized heating element. Five column specimens were considered for experiments and named C (conventional nonheated column), C1 (conventional heated column), C2 (mimicked column), C3 (mimicked column with rebar in cone), and C4 (mimicked column with rebar in cone (quenching)). The heat-dissipating nature was observed, and the structural aspects were tested aftermath. The results reveal that the quenched specimen depicts better heat dissipation than the other specimens and eventually maintains the stability of the specimen throughout the height.

Collapse of composite-repaired cylinders with internal metal loss subjected to external hydrostatic pressure

The present study investigates the collapse performance of composite-repaired cylinders with internal metal loss subjected to external pressure. Three groups of intact, thinned, and repaired cylinders were designed, analytically verified, fabricated, geometrically measured, externally tested, and numerically modeled. Each group had three nominally identical cylinders to ensure the repeatability of experiments. The cylinders had the same end closure, effective length, total length, external radius, and intact thickness for an equivalent comparison. The thinned cylinder was considered as the intact cylinder with internal metal loss, whereas the repaired cylinder was considered as the thinned cylinder with composite reinforcement. The results indicated that the external loading capacity of cylinders with internal metal loss could be fully restored and even enhanced by composite reinforcement. Composite-repaired cylinders are much less sensitive to initial geometrical imperfections than intact cylinders.

DYNAMICS OF THE ACTIVITY OF LIPID PEROXIDATION OF THE LIVER, MANIFESTATIONS OF CYTOLYSIS SYNDROME AND ENDOTOXICOSIS UNDER CONDITIONS OF CLOSED ABDOMINAL TRAUMA COMPLICATED BY INTERNAL BLEEDING

RNAL BLEEDINGAbstract. Traumatism is one of the urgent problems of today. Their structure is dominated by combined and multiple lesions with secondary damage to internal organs and the formation of multi- organ failure. Much more serious consequences arise in the case of direct impact of the traumatic factor on the body cavities. Under the conditions of traumatic damage to the abdomen, there is a direct impact of the impact energy on the internal organs and blood loss. However, until now there are no convincing data to what extent the presence of blood in the peritoneal space can deepen the manifestations of insuffi ciency of the organs of the gastrointestinal tract, in particular, the liver.Goal. To fi nd out the activity of lipid peroxidation in the liver, manifestations of cytolysis syndrome and endotoxicosis under the conditions of closed abdominal trauma complicated by internal bleeding.Material and methods. 132 sexually mature white male Wistar rats were used in the experiments. In experimental group 1, under thiopental sodium narcosis, TTS was simulated. In experimental group 2, external bleeding (20% of circulating blood volume) was additionally induced by transection of the femoral vein. In experimental group 3, also after TTS, bleeding was induced in a similar volume, which was administered intraperitoneally. After 1, 3, 7 and 14 days, the content of reagents to thiobarbituric acid (TBK-active products of POL) was determined in the homogenate of the liver of the experimental rats, in the blood serum – alanine aminotransferase activity (AlAT activity) and the content of the fraction of molecules with an average mass of 280 nm (MSM280). The probability of diff erences was assessed by the non-parametric Mann- Whitney test.The results. Applying only TTZ signifi cantly deepens the processes of lipid peroxidation in the liver, activates the processes of cytolysis and endotoxicosis. The content of TBK-active processes of LPO gradually increases with a maximum after 7 days, AlAT activity and the content of the MSM280 fraction in blood serum reach a maximum by the 3rd day of the experiment, followed by a decrease that does not reach the control level by the 14th day. Applying TT in combination with acute blood loss naturally leads to deepening of the studied processes. Compared with rats that were modeled only with TSH, the content of TBC-active products of LPO, ALT activity, and the content of the MSM fraction in blood serum signifi cantly increased. Comparison of the depth of violations under conditions of blood loss of diff erent origins. showed that the same volume of blood loss with blood fl ow into the intraperitoneal space compared to external blood loss is accompanied by signifi cantly greater violations of the studied indicators.Conclusions. Internal bleeding against the background of TTS, compared to blood loss of a similar volume after external bleeding, causes greater violations of the studied indicators of lipid peroxidation with the maximum manifestation after 3-7 days of the experiment, cytolysis – after 7 days, endotoxicosis – after 7-14 days.

Study on Cracking Law of Earthen Soil under Dry Shrinkage Condition

Earthen sites are easily eroded by the natural environment, resulting in a large number of micro cracks on the surface. In order to explore the internal relationship between environmental factors and the cracking law of soil sites, this paper carries out dry shrinkage tests of different soil layers at the Zhouqiao site, reconstructs the study on cracking law of earthen soil under dry shrinkage-conditioned microstructure of site soil at different depths based on electron microscope pictures and finite element method, and explores the influence of different moisture content on the cracking of soil samples at the site. The results show that under conditions of dry shrinkage, the thickness of the soil layer has the greatest influence on the cracking of site soil samples. Due to the internal water loss and shrinkage of the soil sample, the thinner the soil layer, the more often the soil layer cracks first. The crack rate of the soil sample with a thickness of 1 cm is nearly three times higher than that of the soil sample with a thickness of 5 cm. Through numerical simulation analysis, it is found that the evolution process of soil fractures at the Zhouqiao site is mainly divided into the formation stages of initial stress field, single main fracture, secondary fracture and fracture network. The formation time of the secondary fracture is longer than that of the initial stress field and single main fracture, and the cracking of the upper soil sample is more serious than that of the lower soil sample. Under conditions of dry shrinkage, the particle arrangement of the soil sample is relatively loose, and there are many cracks inside, which provides evaporation and infiltration channels for water, forming unrecoverable weak pores, and finally, the cracks start to sprout at the weak points. The research results provide some reference for the disease mechanism and safety analysis of earthen sites.

Internal freezing and heat loss of apple (Malus domestica Borkh.) and sweet cherry (Prunus avium L.) reproductive buds are decreased with cellulose nanocrystal dispersions.

Cold damage has caused more economic losses to fruit crop growers in the U.S. than any other weather hazard, making it a perennial concern for producers. Cellulose nanocrystals (CNCs) represent a new generation of renewable bio-nanomaterials, with many unique physical and chemical properties, including their low thermal conductivity. Our team has developed a process for creating CNC dispersions that can be sprayed onto woody perennial crops, forming a thin insulating film around buds which has been shown to increase cold tolerance. Using digital scanning calorimetry (DSC) on dormant apple (Malus domestica Borkh.) reproductive buds, we investigated the thermodynamic properties of plant materials treated with CNC dispersion at lower temperatures. Scanning electron microscopy (SEM) was used to evaluate the thickness of the CNC films and their deposition on the sweet cherry bud surface. Apple buds treated with 3% CNC exhibited lethal freezing at temperatures 3.2°C and 5.5°C lower than the untreated control when sampled 1 and 3 days after application, respectively. Additionally, the latent heat capacity (J/g) of the 3% CNC-treated buds was 46% higher compared with untreated buds 1 day after application, and this difference increased 3 days after application to 168% higher. The emissivity of cherry buds treated with 3% CNC was reduced by an average of 16% compared with the untreated buds. SEM was able to detect the dried films on the surface of the buds 3 days after application. Film thickness measured with SEM increased with material concentration. The emissivity, HTE, and LTE results show that CNC-treated reproductive buds released thermal energy at a slower rate than the untreated buds and, consequently, exhibited internal ice nucleation events at temperatures as much as 5.5°C lower. The increased enthalpy during the LTE in the CNC-treated apple buds shows more energy released at lethal internal freezing, indicating that CNC coatings are increasing the amount of supercooled water. The effects of CNC shown during the DSC tests were increased by CNC concentration and time post-application. These results suggest that CNC dispersions dry into nanofilms on the bud surface, which affects their thermodynamic processes at low temperatures.

48 W Continuous-Wave Output From a High- Efficiency Single Emitter Laser Diode at 915 nm

Improving the power and efficiency of 9xx-nm broad-area laser diodes has a great help in reducing the cost of laser systems and expanding applications. This letter presents an optimized epitaxial structure with high power and conversion efficiency. Laser diodes with 230 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> emitter width and 5 mm cavity length deliver continuous-wave output power up to 48.5 W at 48 A, 30 °C, the highest power reported for 9xx-nm single emitter lasers so far. The slope efficiency is as high as 1.23 W/A due to a low internal optical loss of 0.31 cm−1 and a high internal efficiency of 96%. The maximum power conversion efficiency reaches 72.6% at 15.3 W and 67.3% at the operating power of 30 W under a heatsink temperature of 25 °C. Life test results show no failure in 1000 hours for 55 laser diodes.

Experimental and numerical study of swirl impingement cooling for turbine blade leading edge with internal ridged wall and film extraction holes

This paper presents a comparative experimental and numerical study of the internal heat transfer and pressure loss of swirl impingement cooling for turbine blade leading edge with internal ridges and film extraction holes. The leading edge cooling study includes a typical impingement cooling with centerline normal jets, a swirl impingement cooling with offset jets, and a swirl impingement cooling with offset jets and ridged wall. The normal jets are arranged at the impingement plate centerline, and the offset jets adopt a staggered arrangement alternatively on the lateral sides of the impingement plate. The ridged concave wall features two small semi-circular ridges symmetrically on opposite sides under the offset jets. Three rows of film holes are arranged symmetrically on the leading edge cavity, and another two rows of film holes are arranged on the opposite cavity wall behind. Transient thermochromic liquid crystal (TLC) experiments are conducted to obtain the detailed heat transfer distributions on the internal surface of the leading edge cavities with different cooling configurations. The results show that in the swirl impingement cooling, the swirling flow induced by the offset jets impinging onto the concave wall improves the streamwise heat transfer uniformity on the leading edge internal wall, which overcomes the limitation of large heat transfer non-uniformness between jet stagnation region and surrounding regions in typical normal jet impingement cooling. In the swirl impingement cooling with ridged wall, the near-wall jet interacts with the ridges on the concave wall and develops more widely along the spanwise directions, which greatly improves the spatial heat transfer uniformity. In addition, the ridges on the wall can also induce near-wall jets to separate from the wall and attach to the opposite concave wall, which produces low-velocity recirculation in the leading edge cavity and improves the capability and uniformity of coolant outflow through the film holes. Compared to the normal jet impingement cooling, the heat transfer of swirl impingement cooling with smooth and ridged wall can be increased respectively by 10.8%–14.0% and 10.9%–23.6% for the jet Reynold number from 20,000 to 50,000. In addition, the pressure loss is also reduced slightly by less than 5% in the swirl impingement cooling. As supplements to the experiments, numerical computations provide more insights into the turbulent flow structure in the leading edge cooling configurations.

Independently Reconfigurable Internal Loss and Resonance Shift in an Interferometer-Embedded Optical Cavity

Optical cavities find diverse uses in lasers, frequency combs, optomechanics, and optical signal processors. Complete reconfigurability of the resonant frequency as well as the loss enables development of generic field programmable cavities for achieving the desired performance in these applications. Conventional reconfigurable cavities are generally limited to specific material platforms or specific optical tuning methods and require sophisticated fabrication. Furthermore, the tuning of the loss is coupled to the resonance shift in the cavity. We propose and demonstrate a simple and generic interferometer in a cavity structure that enables quasiperiodic modification of the internal cavity loss and the cavity resonance to reconfigure the $Q$ factor, transmission characteristics, and group delay of the hybrid cavity, with simple tuning of the optical phase in the interferometer. We also demonstrate methods to decouple the tuning of the loss from the resonance shift, that enables resonance-locked reconfigurability. This structure also enables resonance shift to both shorter and longer wavelengths using the same phase-tuning technique, which is challenging to achieve in conventional reconfigurable cavities. These devices can be implemented in any guided-wave platform (on-chip or fiber-optic) with potential applications in programmable photonics and reconfigurable optomechanics.