Optymalizacja tribologiczna i symulacja zasuw klinowych do zastosowań przemysłowych

Problem Statement (Relevance). Modern small unmanned aerial vehicles impose high demands on their performance quality, especially in extreme operating conditions. One of the key factors affecting the reliability and longevity of such vehicles is maintaining stable thermal conditions for the batteries in low-temperature environments. Optimizing thermal management becomes necessary to ensure the specified flight characteristics and improve the efficiency of the vehicle's power supply system. To maintain stable power system performance for small unmanned aerial vehicles under such conditions, the development of innovative approaches to thermal management is required. The use of LED lighting devices, due to their significant heat generation, can serve as an unconventional combined source of both light and heat for these aerial systems. This opens new prospects for the development of thermal management models that can provide additional support in maintaining the battery temperature at levels sufficient for normal operation. Objectives. The goal of this work is to develop a battery heating management model for small unmanned aerial vehicles using LED systems, aimed at maintaining optimal operating temperatures for the batteries and improving the reliability and quality of flights in low-temperature conditions (down to -15 degrees Celsius). Methods Applied. This study utilizes a comprehensive approach that includes numerical modeling of thermal processes based on differential heat transfer equations, as well as experimental research aimed at evaluating the efficiency of the proposed model in real-world operating conditions. The modeling was conducted using Python and MATLAB programming languages, ensuring high accuracy and adaptability of the calculations. The simulation of the system's operation was based on data concerning the dynamics of temperature changes, battery characteristics, and LED light sources. Methods of optimal thermal process modeling were applied, along with an analysis of the compliance of the developed model with quality and operational standards under the specified temperature conditions. Originality. For the first time, the integration of LED systems as an active element of thermal management for small unmanned aerial vehicles is proposed, enabling not only illumination but also battery heating in extreme temperature conditions. The developed mathematical model takes into account the main parameters affecting heat transfer and system performance, such as material heat capacity, thermal conductivity coefficients, convection, and radiation. Special attention is given to modeling the interaction of thermal flows within the power source of small unmanned aerial vehicles and accounting for aerodynamic effects on its body, which helps maintain the required flight quality under extreme temperature conditions. Result. The conducted modeling and experimental studies showed that using LEDs to maintain optimal battery temperatures leads to a significant increase in battery life. Practical Relevance. The application of the proposed model and strategy significantly improves the operational characteristics of small UAVs, enhancing their reliability and efficiency in cold climatic conditions. The developed model can be integrated into the design and operation of small UAVs, improving flight quality and the effective use of these devices, thereby expanding their applicability in moderately cold climatic regions.

Thin-walled plate-shell structural elements find wide application in many sectors of engineering and the national economy, particularly in the aerospace and the oil and gas industry, power engineering, mechanical engineering, construction, etc. The integrity and homogeneity of structures can be compromised by the presence of inhomogeneities. Such structures often have various manufacturing defects or design inhomogeneities: holes, cutouts, recesses, inclusions, microcracks, and other similar formations, which act as local stress concentrators. Under real-world operating conditions, an increased stress concentration in the zones of local stress concentrators significantly affects the strength and durability of structural elements, thus making a search for ways to reduce stress concentration a key issue in solid mechanics. When designing up-to-date equipment, optimizing material consumption and extending the service life of components using novel materials and technologies is a priority, which determines their competitiveness in various industries. This study involves a computer simulation and a finite element analysis of the stress and strain fields of thin-walled cylindrical shells with a small circular through hole and several elliptical inclusions of a different material symmetrically arranged around it. For definiteness, it is assumed that the inclusions are homogeneous and located in the plane of the shell. This paper analyzes the effect of the geometry, the mechanical properties, the number, and the arrangement of the inclusions on the stress and strain fields of the shells in the vicinity of the holes under the action of a uniaxial uniform tensile load applied to the shell ends. The distributions of the stress and strain intensities in the zones of local stress concentration are obtained. The obtained numerical results are compared with the results for shells without inclusions and with known similar results for plates. It is shown that the use of "stiff" elliptical inclusions contributes to stress concentration reduction by ~ (10 – 36) % depending on their number and arrangement. In the case of two diagonal inclusions, the stress concentration zone shifts, which is in agreement with the results for a similar problem for a plate.

Experimental study and numerical simulation on in-cylinder flow of small motorcycle engine

Lower back pain is one of the most frequent complaints in US orthopedic outpatient departments. Intervertebral disc degeneration (IDD) is an important cause of lower back pain. Previous studies have found that mechanical loading was associated with IDD, but the underlying mechanism remains unclear. In the present study, a human nucleus pulposus cell line was used to establish an in vitro mechanical loading model. Mechanical loading, western blot analysis, quantitative PCR, ELISA, cell viability assay and IHC staining were used in the current study. It was found that a short loading time of 4 h followed by a long period of rest (20 h) exerted protective effects against matrix degradation in nucleus pulposus cells, whilst a longer loading time of 20 h followed by a shorter period of rest (4 h) resulted in cell apoptosis and extracellular matrix (ECM) degradation. Excessive mechanical loading may induce ECM degradation by activation of the NF-κB signaling pathway. Taken together, these findings demonstrated that whilst moderate mechanical loading exerted beneficial effects on nucleus pulposus cells, excessive mechanical loading inhibited human nucleus pulposus cell viability and promoted ECM degradation by activating NF-κB.

This thesis presents a system approach with the aim to develop improved concepts for small capacity, high temperature lift air-water heat pumps. These are intended to replace fuel fired heating systems in the residential sector, which leads to a major reduction of the local greenhouse gas emissions. Unfavorable temperature conditions set by the existing heat distribution systems and by the use of atmospheric air, as the only accessible heat source, have to be overcome. The proposed concepts are intended to cover the total application range and to provide the full heat demand without any additional (electric) heat supply. A systematic approach, using a multi objective optimization tool, has been applied to evaluate possible alternate refrigerants, which perform best, regarding to the system COP and the specific heat output. All the optimal refrigerant blends are composed by flammable refrigerants and a potential increase of the COP of 8% (compared to the commercial blend R-407C) has been determined. These potential improvements highly depend on the acceptance to use flammable refrigerants, as can be shown by this evaluation. The standard concepts of small capacity heat pumps suffer from a restricted application range and show highly decreasing performances (COP and provided heat) at extreme operating conditions. From the examination of the thermodynamic cycle, different improved concepts are proposed and are assembled in a generalized super-configuration. The most promising concepts have been built as prototype units and have been tested in laboratory. These concepts are: a) the two-stage compression cycles with economizer heat exchanger or b) with economizer flash tank at the intermediate pressure level, c) the booster-compressor setup, d) the one-stage compression cycle including a new developed hermetic compressor, which enables intermediate injection of saturated vapor flow and e) a small capacity auxiliary cycle for liquid subcooling. In all these concepts the application range could be extended, by achieving reduced discharge temperatures and the heat rate provided at extreme operating conditions could be substantially increased (20%-35%, +100% for the booster setup), using the same compressor and evaporator size. System COP has been improved ( 5%) over a large application range, and specifically in high temperature lift operating conditions. The experimental evaluation reveals the major problem of unbalanced oil migration in two-stage compression cycles (except for the booster concept). An extensive evaluation has been applied, to analyze the oil migration in two-stage compression heat pumps. A new developed measurement technique, using a Fourier Transform Infrared Spectrometry combined with a high pressure supporting ATR cell, has been calibrated (with a lower detection limit at 0.2% - 0.4%, and a sensitivity of 0.1%) with the used refrigerant-oil mixtures (R-134a/POE oil and R-407C/POE oil). It has been applied to perform on-line oil concentration measurements during two-stage and one-stage steady stage and during transitory operating modes. A generalized steady state simulation model has been developed including namely the new developed compressor model with an intermediate injection port, considering the geometrical flow path of the tested prototype compressors. A flow map based extensive heat transfer model is integrated into a finned tube evaporator model and taking into account oil effects on the heat transfer. General models of plate heat exchangers and for capillary tube expansion devices complete this modular simulation model, on which the concepts of the super-configuration can be calculated and some parametric analysis has been performed. An in house developed fluid interface module includes the fluid properties calculation program Refprop and allows to define new mixtures or to use the large number of predefined refrigerants.

\n In this note we address the issue of hydrodynamical instabilities in Astrophysical rotating shear flows in the light of recent publications focused on the possibility for differential rotation to trigger and sustain turbulence in the absence of a magnetic field. We wish to present in a synthetic form the major arguments in favor of this thesis along with a simple schematic scenario of the transition to and self-sustenance of such turbulence. We also propose that the turbulent diffusion length scale scales as the local Rossby number of the mean flow. A new prescription for the turbulent viscosity is introduced. This viscosity reduces to the so-called β-prescription in the case of velocity profiles with a constant Rossby number, which includes Keplerian rotating flows.\n\n\n

The increasing demand for corrosion-resistant reinforcement in concrete structures has highlighted the potential of basalt fiber-reinforced polymer (BFRP) bars as a sustainable alternative to conventional steel reinforcement. However, the flexural behavior of BFRP-reinforced concrete beams remains insufficiently characterized, particularly through advanced numerical simulation. This study develops and validates a finite element model (FEM) to analyze the flexural performance of BFRP-reinforced concrete beams and to compare it with that of steel-reinforced beams. Eight beam specimens (200 × 300 × 3,100 mm), including six reinforced with BFRP bars and two with steel bars, were modeled under four-point bending using ANSYS software. The FEM predictions were validated against experimental data and benchmarked with the design provisions of ACI 440.1R-15 and CSA S806-12. The model showed strong agreement with experimental results, yielding ultimate load ratios of 0.92–0.94 for steel-reinforced beams and 1.01–1.45 for BFRP-reinforced beams. At higher reinforcement ratios, FEM predictions tended to overestimate the capacity of BFRP-reinforced beams. While steel-reinforced beams exhibited ductile failure, BFRP-reinforced beams failed in a brittle manner. The predicted moment-deflection responses and crack patterns closely matched both experimental observations and code-based predictions. This validated FEM provides a reliable computational framework for assessing and optimizing the design of BFRP-reinforced concrete beams, thereby advancing the application of non-metallic reinforcement in structural engineering. The findings also highlight challenges in accurately modeling concrete crushing and bond behavior within FEM, indicating directions for future refinement.

Solar-powered air-conditioning system investigation using the finite element method

The tidal straining can generate convective motions and exert a periodic modification of turbulence and sediment transport in estuarine and coastal bottom boundary layers. However, the evidence and physics of convection and sediment suspension induced by tidal straining have not been straightforward. To examine these questions, mooring and transect surveys have been conducted in September 2015 in the region of the Yangtze River plume influence. Field observations and scaling analyses indicate an occurrence of convective motions at the head of saline wedge. Theoretical analyses of stratification evolution in the saline wedge show that unstable stratification and resultant convection are induced by tidal straining. Vertical turbulent velocity and eddy viscosity at the head of saline wedge are both larger than their neutral counterparts in the main body, largely enhancing sediment suspension at the head of saline wedge. Moreover, sediment suspension in both neutral and convection‐affected flows is supported by the variance of vertical turbulent velocity, rather than the shearing stress. Finally, the stability correction functions in the Monin‐Obukhov similarity theory can be simply derived from the local turbulent kinetic energy balance to successfully describe the effects of tidal straining on turbulent length scale, eddy viscosity, and sediment diffusivity in the convection‐affected flow. These recognitions may provide novel understanding of estuarine turbidity maxima, and the dynamical structure and processes for coastal hypoxia.

Defect propagation and material degradation affect both the performance and safety of energy storage systems. Both processes may accompany operation over time, be nucleated during manufacturing, or be initiated rapidly by external stimuli. This raises particular concerns in lithium-ion cell technologies, where the consequences of faults can be dramatic. However, to date, we have limited capability to detect and/or predict these critical lifetime- and reliability-determining events, especially during operation under real-world operating conditions. In this paper we present our work related to embedding sensors within and around commercially available pouch and cylindrical format cells. The types of sensors include reference electrodes for measuring half cell voltages during operation, optical fibres to measure mechanically and thermally induced strain, and magnetoresistive sensors to measure the local magnetic field resulting from the flow of charge. Embedding of these sensors is not trivial as the performance of the cell must be unaffected by the modifications. Furthermore, the embedded sensors must survive the cells internal environment. Methodologies for embedding sensors in pouch and cylindrical cells are discussed. These instrumented cells collectively provide a powerful suite of in-situ and in-operando diagnostics for assessing performance, detecting defect propagation and materials degradation. These diagnostic methods are of great academic interest allowing ageing and failure mechanisms to be studied in greater detail. Furthermore, such diagnostic methods would also be useful in industry allowing systems reliant on lithium battery technology to be characterised in relation to battery operation. Here we present examples of the use of instrumented cells to understand the changes occurring within the cells when operated outside manufacturers’ guidelines and under abuse conditions. Data showing progression of failure is also presented.

<div class="section abstract"><div class="htmlview paragraph">This paper presents the design, structural analysis, structural test validation and risk assessment done by Cummins to evaluate the structural integrity of Light Duty engine cylinder head for a Medium Wheelbase (MWB) pick-up truck. Initially, Cummins used the 2.5L and 3.0L (4-cylinder) engines that have standard power ratings based on existing requirements, but rising market demands for more power, fuel efficiency, lower cost and weight, and future emission compliance led to customer requirements for 15% uprate for 2.5L and 22% uprate for 3.0L from the same base engine. The increase in power requirement possesses challenges on critical components, especially cylinder heads in terms of thermal and structural limits.</div><div class="htmlview paragraph">Multiple analysis led design iterations were performed using cutting edge CAE software such as Ansys, Dassault Systems fe-safe, and PTC Creo to ensure the structural integrity of the cylinder head under high thermal and mechanical loads, and to keep design margins within acceptable limits. A key feature identified through topology optimization was diagonal ribbing pattern on each cylinder, which is novel, and similar pattern can be applied to both new and existing engine platforms to enhance stiffness without major changes to the water jacket.</div><div class="htmlview paragraph">The Cylinder head was subjected to a long endurance test, which comprises of high thermal and mechanical loads under extreme operating conditions. After running for specified number of hours as per inhouse test requirements, the engine was stopped for magnetic particle inspection for any signs of fatigue failure.</div><div class="htmlview paragraph">No major cracks were observed on the 3.0L Cylinder head combustion face. However, a few cracks were observed on the 2.5L cylinder head combustion face at exhaust & intake bridges. Upon investigation, it was concluded that crack was due to high thermo-mechanical fatigue loads and hence further optimization was carried out on the cylinder head design. Furthermore, cylinder head gasket coolant orifice optimization is done to improve the coolant distribution to each cylinder. Thermal analysis showed a reduction in exhaust & intake bridge temperature within the acceptable limits. This paper captures the detailed design and structural analysis on 3.0L and 2.5 L diesel engine Cylinder head.</div></div>

A simple but robust and effective method to improve collective pitch control of variable-speed wind turbines given information on future inflow is proposed. The present paper focuses on the design and prospects of a control concept using predictive disturbance compensation. This feed-forward control structure is based on calculation of a future effective wind speed, on static disturbance compensation from steady turbine data and on estimation of the dynamic behavior. The control strategy is evaluated with regards to stability, robustness and performance in frequency and time domain. The required wind field information is currently not available for common control, but can in general be obtained from measurements with remote sensing technologies and wind modeling. Significant reductions of rotor speed variations, mechanical loads and pitch activity at fatigue and extreme operating conditions are demonstrated.

Degradation of materials under harsh, high-temperature conditions is one of the grand challenges of high-performance energy conversion. Current approaches make use of refractory materials that do not possess ideal properties but are resistant to decomposition by heat. To suppress undesired thermal transport, multiple refractory materials are shaped and arranged with varying degrees of complexity, ranging from multilayers to plasmonic arrays and 3D photonic crystals. Ultimately these structures progress toward more thermodynamically favorable configurations and result in intermixing, reaction or new phase formation, and coarsening. This severely limits their performance in extreme conditions. Here, we introduce the concept of using immiscible refractory oxides with high crystallinity as building blocks of functional ultrahigh-temperature materials. We demonstrate epitaxial oxide heterostructures made from perovskite BaZry gHfy 593 (BZHO) and rocksalt MgO as a photonic crystal (PhC) that can suppress undesired thermal emission at a desired cutoff wavelength. The PhC is implemented as surface filter to suppress mid-infrared thermal emission from the best intrinsic, spectrally selective emitter operating at 1350°C in air. The heterostructure exhibits coherent atomic registry that retains clearly separated refractive index mismatched layers without interface coarsening, interdiffusion, phase change, or decomposition up to at least 1100°C in dry air. The use of dissimilar crystal structures, with low lattice and thermal expansion mismatch, allows for high crystallinity superlattices with interlayer immiscibility at high temperatures. The understanding gained from this study can be used to develop thermal barrier coatings and selective emitters that are resistant to instabilities in air. Beyond BZHO/MgO, we computationally identify ~10° potential oxide pairings that fit our design criteria, demonstrating the vast potential of this approach.

CD = drag coefficient CDDES = empirical parameter Cf = skin-friction coefficient CL = lift coefficient Cp = pressure coefficient Ce1 = model constant for the dissipation equation Ce2 = model constant for the dissipation equation c = chord length f = elliptic operator fd = delayed detached-eddy simulation blending function h = hill height k = turbulent kinetic energy L = turbulent length scale Re = Reynolds number S = deformation tensor Ub = bulk velocity U∞ = freestream velocity y = distance to the nearest wall y = nondimensional wall distance Δ = large-eddy simulation filter width Δt = time step e = turbulent dissipation κ = von Karman constant ν = molecular viscosity νt = turbulent viscosity Ψ = delayed detached-eddy simulation correction term

Objectives/Scope This document presents the application steps of the repair and structural reinforcement system with high-performance polymer and composite material. Without the need to shut-down the offshore platform, this technology is based on ASME and ISO international standards with high safety and applicable in classified areas where hot-work permit is not obtainable. Methods, Procedures, Process The methods and procedures are applied and carried out exclusively for each application, after a judicious risk assessment. Recently, a 14" super duplex pipe carrying seawater line, operating at 8 bar pressure, on an oil platform located in Ghana showed active leak. In order to carry a conventional repair, (replacement of the problematic section or conventional hot welding) the shut-down of production would be necessary. Furthermore, the conventional method was not applicable due to the potentially explosive atmospheric conditions. Based on Part 4 of the ASME PCC-2 standard, the repair system was engineered to a 10-year lifespan and carried out with absolute safety. The procedure consists of a surface preparation, leak containment and structural reinforcement on the defective area of the pipe. All the steps in the aforementioned procedure were cold-work type and without the need to shut-down, therefore without loss of production. The equations used to calculate the thickness and length of the repair system with composite material, as well as the risk assessment, were in accordance to the referenced standards. Results, Observations, Conclusions The repair system was applied with success without the need to shut-down the production and was considered permanent by ABS. The hardness of the composite, measured after 24 hours, indicates full cure of the repair as predicted by the procedure and quality standards. Therefore, the leak was 100% sealed and the area was structurally reinforced in line with the engineering plan and without any loss of production. Novel/Additive Information The integrity of aging offshore assets is a common global problem due to the constraint of concurrent activities in a production environment. This methodology using composite materials in association with asset integrity management without shutdown production has gained recognition to be a long-term solution. The implementation of the repair and structural reinforcement system with high-performance polymer and composite material provides cost reduction, significant health, safety and environmental advantages as it enables immediate attention for the defect, on top of the benefit to avoid the loss of production.