This paper addresses particular features and the comparative feasibility of ekranoplans - a new alternative in fast sea transport. It provides a brief discussion of the present status and prospects for the development and implementation of the wing-in-ground effect technology. Three simplified mathematical models, describing the aerodynamics of a lifting surface in extreme ground effect are introduced and compared (GEM = ground effect machine). Based on these models some estimates are made of the aerodynamic performance and economic feasibility of ekranoplans, in particular the ride quality in flight over waves, take-off efficiency, lift-to-drag ratio, fuel consumption and direct operating costs.
The paper presents general possibilities of identification of technical state of the flow elements in a marine gas turbine. The identification was set on the basis of relative change of gas thermodynamical parameters. The paper contains some results of the research on the flow elements of a marine gas turbine in operation. The research contained measurements of thermodynamical parameters in a marine gas turbine and endoscopic inspection of its passages.
This paper reviews the properties of some currently used ceramics and the potential benefits to be gained from their use in marine engines. Manufacturing techniques for ceramic-coated components are briefly covered, along with the Aeronautical and Maritime Research Laboratory's (AMRL) testing programme. Engine performance and efficiency with and without ceramic insulation have been predicted using a spreadsheet model developed at the AMRL. A finite element analysis has been developed to determine the effect of using ceramic materials on the temperature distribution within critical components. Initial results from this work are included. A single cylinder research engine has been set up as a technology demonstrator. Future plans for modelling and engine testing of ceramic coatings are outlined.
Given the increasingly widespread application of variable speed electrical drive systems for marine propulsion, much has been published in respect of particular projects and the systems selected therein. This paper, however, presents a more detailed focus on the power converter, the variable voltage/frequency component of the system : specifically, the design of the electrical power circuit is examined, the control aspects, the protection and diagnostics, all features which combine to give the modem day converter. Reference is made to current and voltage source systems, taking synchroconverter, cycloconverter and PWM type drives as examples.
This paper describes the design, construction and preliminary performance of a prototype integrated switched reluctance propulsion unit. The device is suitable for use as a steerable propulsor for small submersible and surface vessels. The electric motor used in the unit is a specially designed switched reluctance sector motor which has a six pole stator and a twenty pole rotor. The paper addresses the factors which influenced the design of the motor and considers some of the trade-offs between the mechanical and electromagnetic requirements. A set of preliminary test results is also presented.
A programme of research undertaken by Lloyd's Register into air quality and ventilation on ro-ro ferry vehicle decks is discussed. This work included measurement of the gaseous exhaust emission components, nitric oxide, nitrogen dioxide and carbon monoxide, as well as total suspended particulates and polynuclear aromatic hydrocarbons. The performance of the mechanical ventilation systems and air flow distributions was also assessed and relationships between ventilation and air quality evaluated. In parallel with this research, consideration was being given at the International Maritime Organization (IMO) to the need to amend the relevant SOLAS regulations in order to ensure acceptable air quality for crews working on vehicle decks. The outcome of these deliberations and its relationship with the findings of the research conducted by LR is discussed. In addition, the IMO Guidelines on the Design of Ventilation Systems in Ro-Ro Cargo Spaces and Operational Recommendations for Minimising Air Pollution in Ro-Ro Cargo Spaces, which emerged as part of these discussions, are outlined.
Computer analysis and simulation is of vital importance to ensure the successful design and development of marine engineering systems. In many areas, conventional modelling methods have produced system representations which are inaccurate and/or computationally expensive in terms of processing power and memory requirements. The application of artificial neural networks in certain cases can be used to identify complex marine system characteristics and produce favourable results in comparison to mathematically derived models or look-up tables. This paper provides an introduction to the artificial neural network theory that is relevant to marine system modelling applications. The computational elements that combine to form artificial neurones are outlined and the network topology is examined for static and dynamic modelling purposes. The training procedure is crucial to the performance of a neural network, not only in terms of adapting the network but also in the way that data is presented. Again, these areas are discussed in this paper so that they are relevant to marine system models. Finally, a simple case study is used to demonstrate the application of these learning methods. A comparison is made between a mathematical formulation, a look-up table and an artificial neural network approach to obtain the friction factor as part of a simulation of pipeline fluid flow. This case study demonstrates the ability of well trained neural networks statically to model complex non-linear functions with extreme accuracy and speed.
Simulation studies are of particular value for the research, design and development of marine systems. The extent of their use is dependent upon the accuracy and response speed of the dynamic models constructed. This paper analyses the identification and modelling of dynamic systems and proposes the use of artificial neural network methods in an attempt to improve the simulation process. The application and benefit of such techniques are illustrated by the use of a marine diesel engine case study.
Although hatch covers are a vitally important part of the ship system, it is common experience that they can be troublesome and prone to leakage and other failures in service. This paper briefly reviews the statutory position and the main hatch cover design variations, before going on to discuss the very real practical problems of maintenance and operation that are inherent to many designs. The paper suggests short term management approaches using check lists and operational procedures to spot defects before they cause loss or damage. The same approach can be used to plan maintenance. The presentation is illustrated with specific hatch cover failures.
Due to its simplicity and low cost, natural ventilation is used as one of the principal ventilation methods onboard offshore structures. This paper shows that the design criteria employed should depend on the location of the platform and the local climate. For platforms in the North Sea, it has been shown that buoyancy effects on ventilation rates, due to heated surfaces inside modules, are comparatively small and should only be considered for the case when wind speeds are less than 0.5m/s. Computational Fluid Dynamics (CFD) simulations were made of the natural ventilation of a process module onboard a platform located in the Adriatic Sea. The results showed that buoyancy driven ventilation due to surfaces heated by solar radiation is significant. Also, due to the energy from solar radiation, the buoyancy driven ventilation is a significant factor for much higher wind speeds than the buoyancy driven ventilation principally due to hot equipment on platforms in the North Sea. The results also indicated that very different flow patterns will be found if buoyancy is considered and simulated even at quite high wind speeds. The latter may have implications for certain aspects of offshore module design. Given the climatic conditions in the Adriatic Sea and its weather statistics, the CFD simulations show that buoyancy driven ventilation should be considered as a primary design parameter and that erroneous designs can be the result if, say, methods developed for the North Sea were applied to platforms in the Adriatic Sea. Finally, it is suggested that CFD simulations should be integrated into the design process for natural ventilated areas.
The demand for a comfortable environment on cruise vessels and the stringent habitability standards recommended by authorities to protect shipboard personnel against hearing damage prompt the necessity of an accurate noise prediction at the ship design stage. Whilst it is recognised that noise prediction is a continuous research and development activity in many institutes and universities throughout the world, the intention of this paper is to discuss noise prediction techniques in a general manner and to describe the approach to noise prediction developed and used by Lloyd's Register (LR). There is no guarantee of absolute accuracy in any noise prediction technique. This paper first briefly outlines the problems and factors affecting the degree of accuracy. The development of LR's own noise prediction programme is then addressed. In order to demonstrate the correlation between predicted and measured results, two practical cases, which have been completed recently on a modern containership and a luxury yacht, are discussed. The final section of the paper is devoted to a discussion of how future developments may improve the accuracy of noise prediction.
Motor generators have been used as the main method of power conversion and power transfer between the ac system and the dc system on nuclear submarines since the inception of the programme. The developments in the power handling capability of power electronic devices have allowed a static alternative to the rotary motor generator to be adopted. One of the major advantages to be realised by static conversion will be an increase in submarine availability. Additionally, static conversion opens up the possibility of alternative power system architecture and motor control. Static conversion, however, brings with it new challenges to equipment and system designers, including electromagnetic compatibility (emc). Having identified the main sources and effects of electromagnetic interference, equipments/systems are designed to ensure their correct operation in the installation, particularly where they are associated with safety related systems. Converter designs using high power, fast switching devices, introduce potential sources of interference at different frequencies than previously encountered. In addition, the control and power electronics associated with high power switching systems are themselves susceptible to the effects of electromagnetic interference from other sources in the installation. Having designed the equipment, emc verification testing is carried out to demonstrate that the requirements have been met.
This paper perpetuates a long established practice of periodically presenting the findings derived from the failure investigations undertaken by Lloyd's Register (LR). The principal aim is to share some of the technical experience gained from these activities. Case studies with a strong practical bias are described in a way that is intended to interest marine engineers. The interpretation of the results and the opinions expressed are, however, necessarily those of the authors rather than of LR. A comparison with previous papers shows that failures continue to occur due to material fracture mechanisms, which are generally well understood. Examples have been selected to illustrate the wide diversity of causes associated with design, manufacture, operation, maintenance and repair that can damage shafts. Particular emphasis is focused on fatigue crack growth characteristics and the potential detrimental implications of fretting, corrosion, surface flaws and the incidence of thermal cracks due to rubbing contact. The case studies also demonstrate the interdependence between engineering measurements, metallurgical examinations and calculations in conducting failure investigations.
This paper describes the application of modern simulation tools in the design, setting-to-work, commissioning and operation of major shipboard systems. To illustrate the techniques used, a full diesel electrical propulsion system is used as the case study, tracing the evolution from conceptual design through to service operation, analysis of trials results and final model evaluation. Past experience with simulation and the efficiency of modern tools enabled a variety of innovative features to be tested at the design stage, and to be adopted with confidence in the chosen system configuration. Simulation results and trials results are presented, with a particular focus on harmonic control, power management performance and transient stability of the system. An example of simulation as a through-life vessel support tool is presented, demonstrating the development, installation and validation of system enhancements in response to specific owner requirements.
Recent progress in the development of artificial neural networks has prompted several investigations into their use. This paper describes work that has been undertaken to try and determine the applicability of neural computing techniques to existing condition monitoring problems. The findings from a feasibility study are reported, as are the results from a basic demonstrator program that was developed. Further work is then discussed, covering the application of neural computing techniques to marine diesel engines and marine gas turbines. Some results are presented and it is concluded that neural computing can offer significant advantages over traditional processing methods.
The Engineering Council has produced two Codes of Professional Practice in the past 18 months covering 'Risk' and the 'Environment'. The background to these Codes and the implied responsibilities of engineers are discussed in this paper. Examples of differing perceptions are presented to illustrate the importance of communications and there are some general observations about the increasing liability of engineers when things go wrong.
Human action is one of the main contributors to accidents and operational disturbances. The 'operator' is a vital link in maintaining safe work systems and the key factors, among many others, are the experience and training of the operator. In this paper an approach for improving the operator performance, based on more effective utilisation of computer based training methods, is presented. A safety triangle model is used to understand the goals of safety training. A number of existing offshore safety training methods are assessed and the scope for advanced software methods is examined. A new model of safety training is proposed, where the training function is integrated between the designers, safety experts and the training instructor. The conceptual framework of an ideal Safety Training System is then formalised. The significant features of this framework are the integration of a number of tutoring strategies, a shell based approach allowing instructors to develop lessons and plant models without the need for programming, and use of qualitative modelling methods for plant simulation. A prototype Knowledge Based Safety Training System, developed as a practical implementation of the ideal system, is also described.
