Marine Engines Performance and Emissions

This book contains a collection of peer-review scientific papers about marine engines’ performance and emissions. These papers were carefully selected for the “Marine Engines Performance and Emissions” Special Issue of the Journal of Marine Science and Engineering. Recent advancements in engine technology have allowed designers to reduce emissions and improve performance. Nevertheless, further efforts are needed to comply with the ever increased emission legislations. This book was conceived for people interested in marine engines. This information concerning recent developments may be helpful to academics, researchers, and professionals engaged in the field of marine engineering

Theoretical foundations of the methods and means of increasing the efficiency of vibration diagnostics of power equipment

The work is devoted to the development and application of computational and experimental methods and means of increasing the efficiency of vibration diagnostics of power equipment, including gas compressor units of gas transmission systems. There are solutions of the problem of natural frequencies and modes of its vibrations to calculate of the levels of power ratio (sensitivity functions) of equipment units and they are summarized in the form of computational models

Exploring the limitations of linear and nonlinear vibration absorbers

Een veel toegepaste manier om overmatige trillingsamplitudes te beperken is het lokaal aanhechten van een licht massa-veer-demper systeem, beter bekend als een dynamische trillingsdemper (dynamic vibration absorber). Aangezien de trillende hoofdstructuur zelf niet gewijzigd moet worden en men typisch met een zeer klein dynamisch element sterke trillingsreducties kan bekomen, wordt dit element zeer veel gebruikt in tal van ingenieurstoepassingen zoals onder meer bij gebouwen (aardbeving,wind), bruggen (verkeer), transportvoertuigen (auto, helikopter) en machines. Sinds de uitvinding hiervan door Frahm meer dan honderd jaar geleden, hebben onnoemelijk veel onderzoekers nieuwe types van trillingsdempers ontwikkeld in de hoop de klassieke dynamische trillingsdemper te verbeteren. Een zeer recent voorbeeld hiervan is het gebruik van sterk niet-lineaire veren die erin slagen om de trillingen in een veel ruimer frequentiegebied te onderdrukken. In dit eindwerk wordt zowel ingegaan op het klassiek lineaire element als op zijn niet-lineaire tegenhanger. Hoewel reeds zeer veel onderzoek is gewijd aan beide elementen, zijn we erin geslaagd om het inzicht in verschillende aspecten sterk te verruimen wat vooral bij het praktisch implementeren van cruciaal belang is

Systematic investigation of a large two-stroke engine crankshaft dynamics model

The crankshaft dynamics model is of vital importance to a multitude of aspects on engine diagnostics; however, systematic investigations of such models performance (especially for large two-stroke diesel engines that are widely used in the power generation and shipping industries) have not been reported in the literature. This study aims to cover this gap by systematically investigating the parameters that affect the performance of a two-stroke diesel engine crankshaft dynamics model, such as the numerical scheme as well as the engine components inertia and friction. Specifically, the following alternatives are analysed: (a) two optimal performing numerical schemes, in particular, a stiff ordinary differential equations (ODE) solver and a fast solver based on a piecewise Linear Time-Invariant (LTI) scheme method, (b) the linear and the non-linear inertia-speed approaches, and (c) three engine friction submodels of varying complexity. All the potential combinations of the alternatives are investigated, and the crankshaft dynamics model performance is evaluated by employing Key Performance Indicators (KPIs), which consider the results accuracy compared to the measured data, the computational time, and the energy balance error. The results demonstrate that the best performing combination includes the stiff ODE solver, the constant inertia-speed approach and the most simplistic engine friction submodel. However, the LTI numerical scheme is recommended for applications that require fast response due to the significant savings in computational time with an acceptable compromise in the model results accuracy

Marine Power Systems

Marine power systems have been designed to be a safer alternative to stationary plants in order to adhere to the regulations of classification societies. Marine steam boilers recently achieved 10 MPa pressure, in comparison to stationary plants, where a typical boiler pressure of 17 MPa was the standard for years. The latest land-based, ultra-supercritical steam boilers reach 25 MPa pressure and 620 °C temperatures, which increases plant efficiency and reduces fuel consumption. There is little chance that such a plant concept could be applied to ships. The reliability of marine power systems has to be higher due to the lack of available spare parts and services that are available for shore power systems. Some systems are still very expensive and are not able to be widely utilized for commercial merchant fleets such as COGAS, mainly due to the high cost of gas turbines. Submarine vehicles are also part of marine power systems, which have to be reliable and accurate in their operation due to their distant control centers. Materials that are used in marine environments are prone to faster corrosive wear, so special care also should be taken in this regard. The main aim of this Special Issue is to discuss the options and possibilities of utilizing energy in a more economical way, taking into account the reliability of such a system in operation

Advances in Vibration Analysis Research

Vibrations are extremely important in all areas of human activities, for all sciences, technologies and industrial applications. Sometimes these Vibrations are useful but other times they are undesirable. In any case, understanding and analysis of vibrations are crucial. This book reports on the state of the art research and development findings on this very broad matter through 22 original and innovative research studies exhibiting various investigation directions. The present book is a result of contributions of experts from international scientific community working in different aspects of vibration analysis. The text is addressed not only to researchers, but also to professional engineers, students and other experts in a variety of disciplines, both academic and industrial seeking to gain a better understanding of what has been done in the field recently, and what kind of open problems are in this area

Reduction of Torsional Vibrations Excited by Electromechanical Interactions in More Electric Systems

This paper studies the excitation of torsional vibrations by electromechanical interaction after the connection of electrical loads. Electrical generation and power system in aircraft are becoming of key importance, especially considering the current roadmap for aerospace systems’ electrification. However, since the drivetrain which links electrical generators to the main engine is relatively flexible in most aircraft structures, torsional vibrations can be excited by the sudden connection or disconnection of electrical loads, thus increasing the drivetrain’s fatigue and reducing its reliability and lifetime. Because of the increased amounts of intermittent electrical loads on aircraft systems, which excite torsional vibrations through electromechanical interactions, the electrical load connections are investigated in this paper. Specifically, a method for reducing torsional vibrations in aircraft drivetrains is proposed to extend their lifespan. This method is applied directly to the load being connected and it proposes the connection of the electrical loads following a pulsating pattern, for which the pulse connection time is determined as a function of the drivetrain vibration modes. Simulations results show that the proposed method provides a significant reduction in the drivetrain shaft torsional vibrations. Experimental results validate the simulation data showing the benefits this method can provide in drivetrain reliability, weight reduction and cost

A review of the dynamic analysis of axial vibrations in marine propulsion shafting system due to propeller excitation

Over the past decades, the attenuation of axial vibration due to propeller excitation has long been a complex problem due to the coupling dynamics of the propeller-shafting system. As axial vibration is often the cause of fatigue damage to the propulsion shaft components as well as the root cause to acoustical radiation along a hull of a ship, there has been continuous interest in understanding the complex dynamic characteristics of the coupled propeller-shaft system and the methods to suppress the axial vibration in the system. Therefore, several studies have been conducted to solve this vibration problem on the longitudinal axis of the marine propulsion shafting system. This paper aims to provide the theoretical foundations of this problem by reviewing the modelling techniques of this coupled dynamic problem and cover the vibration reduction strategies that are proposed by the cited studies