scholarly journals Marine diesels mechanical charging driving improvement through overrunning-safety clutch application

2020 ◽  
Vol 26 (1) ◽  
pp. 58-71
Author(s):  
Владислав Олександрович Проценко ◽  
◽  
Володимир Олександрович Малащенко ◽  
◽  
◽  
...  
Keyword(s):  
Load Transfer ◽  
Steady Motion ◽  
Static Balance ◽  
Response Accuracy ◽  
Friction Forces ◽  
Operational Characteristics ◽  
Torque Response ◽  
Marine Diesel ◽  
Charging Efficiency ◽  
Safety Clutch

Article deals with marine diesels mechanical charging driving protecting problem. On the base of marine diesel EMD 710G overrunning clutch construction analysis its disadvantages were highlighted. Main of them is the principle of working load transfer by friction forces. That is the reason of clutch skidding in operation and charging efficiency degradation. A new design of the safety-overrunning clutch for marine diesels mechanical charging driving, based on the principle of engagement is proposed. In new overrunning-safety clutch construction, which protected by patent, the overrunning and safety parts are mutually integrated. Clutch operations on the overrunning and overload modes are described. On the basis of ball acting forces on steady motion description expressions for its static balance are obtained. Those static balance expressions were the basis for coupling nominal working torque ratios receiving. On the next stage ball forces balance on the overload mode was analyzed. As a result of those stage studies expressions for calculating overload spring deformation, torques of the beginning and ending of its operation are obtained. On the basis of clutch nominal torque, torques of beginning and ending operation the ratios for assessing the main operational characteristics of the coupling when operating in overload mode are obtained - coefficients for exceeding the nominal torque, response accuracy and sensibility.

Marine Diesel Propulsion Plants for the U.S. Navy: Requirements for Geared Medium-Speed Engines

1991 ◽  
Vol 28 (05) ◽  
pp. 276-301
Author(s):  
Zbigniew J. Karaszewski ◽  
Wilhelm F. Schaefer
Keyword(s):  
Gas Turbines ◽  
State Of The Art ◽  
The United States ◽  
Point Of View ◽  
Operational Characteristics ◽  
Medium Speed ◽  
Marine Diesel ◽  
Prime Movers ◽  
Main Components ◽  
Economic Considerations

Economic considerations for reduced operational costs of U.S. Navy diesel ships and the experience of European operators with diesel propulsion can no longer be ignored. The operational characteristics of high-powered diesel engines, compared with those of the steam or gas turbines, as prime movers, is different with respect to the propulsion system balance of torque variations. Maintenance is also quite different when compared to that of turbine installations. From an engineering point of view it is essential to have well-defined criteria for achieving balanced main components and system design. The sudden turn of American operators—with predominant knowledge and confidence in steam or gas turbine propulsion design and operation—towards marine diesel plants could result in unacceptable operational scenarios of existing diesel ships and eventual abundance or long delay of diesel power plant applications in the United States. This paper provides a broader understanding and greater appreciation of the technical aspects governing the application, design and operation of a state-of-the-art diesel propulsion plant.

scholarly journals ANALYSIS OF PROCEDURES ON IMPROVING OPERATIONAL QUALITIES OF THE SHIP SMALL-SIZE DIESEL ENGINES

2018 ◽  
pp. 48-59
Author(s):  
Elena Georgievna Ilyina ◽  
Anzor Akhmedovich Muzaev ◽  
Pavel Aleksandrovitch Dorokhov ◽  
Nadezhda Vladimirovna Pakhomova
Keyword(s):  
Diesel Engines ◽  
Internal Combustion Engines ◽  
General Purpose ◽  
Analytical Determination ◽  
Friction Forces ◽  
Marine Diesel ◽  
Coating Methods ◽  
Reducing Costs ◽  
To Come ◽  
Object Of Study

The functional characteristics of ship small-sized diesel engines are the object of study. Application of new or well-known technical solutions for improving operational characteristics of diesel engines in mass production or modernization processes has been proposed as a variant of reducing costs at designing and manufacturing small-size diesel engines. The paper presents the review of the designs of marine small-size diesels and an overview of possible measures to improve their performance characteristics. Comparative assessment of internal combustion engines quality for a certain set of their parameters refers to the problem that mechanical engineers often have to come across. There appears the need in a well-developed general-purpose methodology for comparative quality assessment of marine diesel engines, which could be used under different circumstances: quality certification, analysis of competitiveness, etc. Hence the need for solving the following partial problems: to develop a methodology for analytical determination of the value of marine diesel engines using their functional indicators given in the manufacturers’ prospectuses. Renovations and improvements require the methodology for evaluating costs and gross income resulted from the operation of the product or profits. Developing running-in coating methods is considered as a subproblem, as well as a scientific justification for these methods which reduce energy losses when overcoming friction forces in the cylinder group. The new technique will give the possibility to calculate the effective power of the main ship engine using operable indicator diagrams.

scholarly journals RESEARCH OF STARTING MODES OF THE RT-FLEX ENGINE

2020 ◽  
Vol 41 ◽  
pp. 117-124
Author(s):  
E.M. Polovinka ◽  
◽  
I.N. Tabulinskiy ◽  
P.S. Muradyan ◽  
Keyword(s):  
Fuel Injection ◽  
Combustion Process ◽  
Oscillatory Process ◽  
Working Process ◽  
Mixture Formation ◽  
Fuel Flow ◽  
Operational Characteristics ◽  
Marine Diesel ◽  
Start Ups ◽  
Atomization Pressure

Starting modes are one of the most critical in the operation of marine diesel engines. Under the unsteady conditions of the flow of working processes, it is difficult to ensure their quality indicators. Of particular importance is the reliability in maneuvering. The foregoing relates, first of all, to fuel injection, which determines to a large extent the combustion process and all the operational characteristics of a diesel engine. Typical start-ups are the first fuel supply cycles [1], presented in Fig. 1 by the oscillograms of the nozzle needle movement. An oscillatory process is observed, accompanied by a partial rise of the needle. This increases the duration of injection, and an incomplete rise leads to a throttling of the fuel flow in the section under the needle. The atomization pressure decreases, the conditions of mixture formation deteriorate, which, along with the low parameters of the air charge, adversely affects the characteristics of the working process up to skipping the ignition.

Skin Friction Directionality in Monotonically- and Cyclically-Loaded Bio-inspired Piles in Sand

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Alejandro Martinez
Keyword(s):  
Cyclic Loading ◽  
Service Life ◽  
Skin Friction ◽  
Load Transfer ◽  
Compressive Loading ◽  
Axial Loading ◽  
Load Testing ◽  
Friction Forces ◽  
Caudal Direction ◽  
Loose Deposits

Piles can be subjected to axial loading in opposite directions during their installation and service life. For instance, piles for offshore jacket structures and load testing reaction systems are subjected to compressive loading during installation and tensile or cyclic loading during service life. This creates a design dilemma: while a large skin friction can lead to refusal at shallower depths than required during driving, it also promotes a large pile axial capacity. This paper describes the load-transfer behavior of piles with surfaces inspired by the belly scales of snakes that mobilize a direction-dependent skin friction. The investigation presented herein consists of a series of twelve centrifuge pile load tests on bio-inspired and smooth reference piles in dense and loose deposits of Ottawa F65 sand. Test results indicate that greater skin friction forces are mobilized when the bio-inspired piles are displaced in the cranial direction (i.e. soil moving against asperities) relative to the caudal direction (i.e. soil moving along asperities). This is observed during pushing and driving installation, where greater skin friction forces were mobilized during installation by pushing in the cranial direction and driving in the cranial direction required more blows per meter. Similarly, the skin friction mobilized during pullout tests was between 82% and 198% greater in the cranial direction than in the caudal direction, and the skin friction mobilized during pullout by the bio-inspired pile in the cranial direction was between 560% to 845% greater than that mobilized by the reference untextured pile. During cyclic loading, degradation of the skin friction magnitude and pile secant stiffness was observed in both cranial and caudal directions; however, the mobilized magnitudes were generally greater in the cranial direction. Discussion is provided on the potential benefits that the bio-inspired surface texture could realize on the overall performance of axially-loaded piles.

scholarly journals CFD Analysis of a Large Marine Engine Scavenging Process

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 141
Author(s):  
Tomislav Senčić ◽  
Vedran Mrzljak ◽  
Vedran Medica-Viola ◽  
Igor Wolf
Keyword(s):  
Engine Performance ◽  
Passive Scalar ◽  
Trapping Efficiency ◽  
Pollutant Emissions ◽  
Delivery Ratio ◽  
Engine Operation ◽  
Marine Diesel ◽  
Operation Parameters ◽  
Scavenging Efficiency ◽  
Charging Efficiency

The scavenging process is an important part of the two-stroke engine operation. Its efficiency affects the global engine performance such as power, fuel consumption, and pollutant emissions. Slow speed marine diesel engines are uniflow scavenged, which implies inlet scavenging ports on the bottom of the liner and an exhaust valve on the top of the cylinder. A CFD model of such an engine process was developed with the OpenFOAM software tools. A 12-degree sector of the mesh was used corresponding to one of the 30 scavenging ports. A mesh sensitivity test was performed, and the cylinder pressure was compared to experimental data for the analyzed part of the process. The scavenging performances were analyzed for real operation parameters. The influence of the scavenge air pressure and inlet ports geometric orientation was analyzed. The scavenging process is analyzed by means of a passive scalar representing fresh air in the cylinder. Isosurfaces that show the concentration of fresh air were presented. The variation of oxygen and carbon dioxide with time and the axial and angular momentum in the cylinder were calculated. Finally, the scavenging performance for the various operation parameters was evaluated by means of scavenging efficiency, charging efficiency, trapping efficiency, and delivery ratio. It was found that the scavenging efficiency decreases with the engine load due to the shorter time for the process. The scavenging efficiency increases with the pressure difference between the exhaust and scavenging port, and the scavenging efficiency decreases with the increase in the angle of the scavenging ports. It was concluded that smaller angles than the industry standard of 20° could be beneficial to the scavenging efficiency. In the investigation, the charging efficiency ranged from 0.91 to over 0.99, the trapping efficiency ranged from 0.54 to 0.83, the charging efficiency ranged from 0.78 to 0.92, and the delivery ratio ranged from 1.21 to 2.03.

scholarly journals Diagnosing the state of marine diesel engines by probabilistic fault recognition method

2021 ◽  
pp. 109-122
Author(s):  
Andrey V. Kulagin Kulagin
Keyword(s):  
Diesel Engine ◽  
Diesel Engines ◽  
Marine Diesel Engine ◽  
Negative Consequences ◽  
Timely Manner ◽  
Fault Recognition ◽  
Operational Characteristics ◽  
Marine Diesel ◽  
Monitoring Devices ◽  
Technical Failures

Diagnostics of marine diesel engines, during the navigation of the vessel, allows you to prevent the development of an accident, perform maintenance in a timely manner, eliminate the possibility of technical failures. The wear of parts is one of the main reasons for putting a diesel engine into repair. Timely detection of the occurrence of wear according to the indications of standard monitoring devices, allows you to prevent the negative consequences of wear, perform repairs in a timely manner, eliminate the possibility of an unplanned exit of the marine diesel engine from operation. If there is a need to operate a marine diesel engine in conditions different from those established by the manufacturer, diagnostics allows you to predict the temporary operational characteristics

scholarly journals A THERMAL ANALYSIS OF THE THREADED SPINDLE BEARING ASSEMBLY IN NUMERICALLY CONTROLLED MACHINE TOOLS

2018 ◽  
Vol 16 (2) ◽  
pp. 261 ◽  
Author(s):  
Vladislav Krstić ◽  
Dragan Milčić ◽  
Miodrag Milčić
Keyword(s):  
Thermal Analysis ◽  
Machine Tools ◽  
Heat Load ◽  
Load Transfer ◽  
Ball Bearing ◽  
Uniform Motion ◽  
Positioning Accuracy ◽  
Friction Forces ◽  
Spindle Bearing ◽  
Bearing Assembly

A threaded gear in machine tools is a mechanical actuator that converts rotary motion into linear one of the machine axis using a recirculating ball-nut. It provides positioning accuracy, uniform motion, silent operation, reduced wear and an increased service life. The bearing assembly of the threaded spindles should provide load transfer (cutting forces and friction forces) while maintaining high guiding accuracy. Due to a high number of the threaded spindle revolutions and the presence of tension in the bearing and a high axial force originating from the cutting and friction forces, the increased heat load due to friction in the bearings is normally expected. For this reason, this paper presents a thermal analysis of the bearing assembly of the threaded spindle which is realized via an axial ball bearing with angular contact of the ZKLN type, produced by the German manufacturer Schaeffler (INA); in other words, a numerical thermal analysis has been performed.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

Deformation at interfaces of Ti-6Al-4V/SiC fiber composites

1992 ◽  
Vol 50 (1) ◽  
pp. 158-159
Author(s):  
Warren J. Moberly ◽  
Daniel B. Miracle ◽  
S. Krishnamurthy
Keyword(s):  
Thermal Stresses ◽  
Load Transfer ◽  
Coefficient Of Thermal Expansion ◽  
Hot Isostatic Pressing ◽  
Matrix Composites ◽  
Ongoing Research ◽  
Aerospace Applications ◽  
Sic Fiber ◽  
The Matrix ◽  
Intermetallic Matrix Composites

Titanium-aluminum alloy metal matrix composites (MMC) and Ti-Al intermetallic matrix composites (IMC), reinforced with continuous SCS6 SiC fibers are leading candidates for high temperature aerospace applications such as the National Aerospace Plane (NASP). The nature of deformation at fiber / matrix interfaces is characterized in this ongoing research. One major concern is the mismatch in coefficient of thermal expansion (CTE) between the Ti-based matrix and the SiC fiber. This can lead to thermal stresses upon cooling down from the temperature incurred during hot isostatic pressing (HIP), which are sufficient to cause yielding in the matrix, and/or lead to fatigue from the thermal cycling that will be incurred during application, A second concern is the load transfer, from fiber to matrix, that is required if/when fiber fracture occurs. In both cases the stresses in the matrix are most severe at the interlace.

Slow Wave Activity Related to Working Memory Maintenance in the N-Back Task

2016 ◽  
Vol 30 (4) ◽  
pp. 141-154 ◽  
Author(s):  
Kira Bailey ◽  
Gregory Mlynarczyk ◽  
Robert West
Keyword(s):  
Working Memory ◽  
Slow Wave ◽  
Time Course ◽  
Relevant Information ◽  
Wave Activity ◽  
Slow Wave Activity ◽  
Response Accuracy ◽  
Functional Neuroanatomy ◽  
Stimulus Interval ◽  
Back Task

Abstract. Working memory supports our ability to maintain goal-relevant information that guides cognition in the face of distraction or competing tasks. The N-back task has been widely used in cognitive neuroscience to examine the functional neuroanatomy of working memory. Fewer studies have capitalized on the temporal resolution of event-related brain potentials (ERPs) to examine the time course of neural activity in the N-back task. The primary goal of the current study was to characterize slow wave activity observed in the response-to-stimulus interval in the N-back task that may be related to maintenance of information between trials in the task. In three experiments, we examined the effects of N-back load, interference, and response accuracy on the amplitude of the P3b following stimulus onset and slow wave activity elicited in the response-to-stimulus interval. Consistent with previous research, the amplitude of the P3b decreased as N-back load increased. Slow wave activity over the frontal and posterior regions of the scalp was sensitive to N-back load and was insensitive to interference or response accuracy. Together these findings lead to the suggestion that slow wave activity observed in the response-to-stimulus interval is related to the maintenance of information between trials in the 1-back task.

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