This paper investigates Homogeneous Charge Compression Ignition (HCCI) combustion on an engine that is fuelled with ethanol, iso-octane, and ethanol/iso-octane. The engine is a four-stroke three cylinder in-direct injection type diesel engine converted to a single cylinder HCCI operation. In order to clarify the effects of fuel chemistry on HCCI combustion, the trials were done at a constant engine speed, a fixed initial charge temperature and engine coolant temperature. The HCCI engine was fuelled with a lean mixture of air and fuel (ethanol, iso-octane or mixture of ethanol/iso-octane). The engine performance parameters studied here include indicated mean effective pressure (IMEP) and thermal efficiency. Heat-release rate (HRR) analysis was done to determine the effect of fuels on combustion on-set. The experimental results demonstrate that the addition of iso-octane to ethanol retards the on-set of combustion and subsequently leads to a reduction of the IMEP and thermal efficiency. For a particular fuel, the on-set of combustion depends closely on the intake charge temperature (as reported by several other researchers) and any increase in the initial charge temperature leads to advances in the on-set of combustion. Furthermore, the experimental results demonstrate that operating the engine on a lean charge reduces engine-out NOx emissions significantly.

The need to commercially, scientifically and militarily exploit the oceans has increased dramatically over the last 30 years. With this requirement has been generated the need for efficient underwater vessels capable of extended endurance, autonomy, high reliability and increased power density. In the past the majority of these vessels have been powered by secondary batteries, however, with the previous criteria in mind, batteries are in many instances no longer capable of meeting mission objectives. Advancements in air independent heat engines requires the use of stored chemical energy, normally in the form of hydrocarbon fuel and an oxidant. In the latter case, the oxidant volumetric and gravimetric storage densities can be changed by storing or deriving the oxygen from several different sources such as pure oxygen, oxygen rich compounds and oxygen extraction from seawater by electrolysis or membranes. Each oxygen source offers a different oxygen liberation capability, as well as dissimilar storage densities. Apart from the physical properties of the different oxidants, they each require a different type of containment and operating system. All of these factors will affect the total oxygen system weight and volume requirements. To understand the trade-offs involved in the oxidant system used for a particular vehicle and mission profile, this paper assesses the selection and evaluation of the possible oxygen sources required for hydrocarbon fuelled heat engines

In hydrocarbon fuelled air-independent power system research, whether an internal/external combustion heat engine, or fuel cell, an exhaust gas management system is required. In previous research many techniques have been proposed for the control and/or removal of the combustion generated exhaust products, notably heat exchangers and carbon dioxide separation techniques. However, there has been little research on the merits of one system verses another for a particular vehicle application and engine. To address the systems and their applicability to a particular power system and vehicle, the paper assesses and evaluates exhaust gas management systems for a Stirling engine driven diver propulsion vehicle

The critical enabling technologies which have been identified to fully realise the potential of AUVs are: long endurance propulsion/energy systems; geodetic and relative navigation; underwater communications; mission management and control; sensors and signal processing; and vehicle design. However, perhaps the most critical technology for almost every AUV application, and often the operational limiting factor, is the availability of adequate onboard energy/power. Given the specialist nature of the AUV market, research and development into new AUV-specific power systems is inevitably limited by resources.At the present, the relative merits and disadvantages of the competing Air-Independent Power Systems (AIPS) are fairly well known. However, the greatest need of advice is with the "total system" and its integration, i.e., how the AIPS is affected by, and affects the overall vehicle design. Hence, with the numerous design considerations of an AUVs, full knowledge and understanding of the total AIPS integration is essential, if a technically and operationally successful vehicle design is to be achievedThe aim of this paper is to examine the conceptual design of an AUV with specific emphasis on the integration of an Air-Independent Power System, thereby enabling the initial design of AUVs to be evaluated.

The capabilities of a diesel engine to operate on an atmosphere of 70 mol% carbon dioxide and 30 mol% oxygen when pre-heated to 150 degrees C h as been demonstrated. The rated brake power is reduced by 20-23%, while brake-specific fuel consumption is increased by 23-28%, The hypothesis that carbon dioxide is seriously affecting both pre- and post-ignition processes by slowing down reaction rates is presented. Simulation work has shown that phenomenological models, when suitably modified, can predict brake performance parameters of engines operating on such atmospheres to within 5% within certain limitations. Custom-derived ignition delay and heat release models have been successfully validated specifically for non-air diesel operation.

The selection and design of a power system for any form of underwater vehicle is an extremely complex and difficult task. The system must be capable of providing the vehicle with the required mission performance in terms of power and energy and also be volumetrically and gravimetrically compact. When the vehicle to be used is a newly designed US Navy Diver Propulsion Vehicle (DPV), other power system constraints are highlighted. These constraints include limited vehicle diameter, high performance operation, low power requirements, safety and a nonmagnetic signature. Of the many power systems available, very few can fulfil the design criteria for the DPV. One system that can is the hydrocarbon fuelled Stirling engine-a dynamic heat engine using an external combustion system. This paper describes the application of the Stirling engine for underwater duties, and in particular the selection, design and development of a Stirling engine powered DPV. Details are given of the specialist vehicle requirements, engine selection and design and the development of a combustion gas recirculation system to enable pure gaseous oxygen to be used as the combustion oxidant. In addition, details are given of the restrictions imposed on component design and manufacture by the low vehicle power requirements

Ship operators are under mounting environmental pressure to reduce, and in certain cases totally eliminate, the discharge of waste into the sea. At the moment beyond the twelve mile limit untreated sewage can be legally discharged into the open oceans. For some types of waste there is international nil-discharge legislation which prohibits any dumping in certain sea areas. In the future sewage is likely to be identified as one of these nil-discharge waste materials. Thus, there may soon be a requirement for onboard sewage systems that are capable of meeting this requirement. In this paper the novel concept of using marine diesel engines to thermally destroy sewage streams is considered. The main constituent of such effluents is water, about 90% and an appreciable amount of the solid content is combustible. As direct water injection is now an established technology for NOx reduction from marine diesel engines it appears feasible, at least technically, to use such technology in sewage stream treatment. Preliminary estimates have shown that the sewage stream quantities produced onboard large marine vessels could be treated using the ships' existing diesel engines. The outline requirements for such marine diesel engines to be operated as sewage processors are discussed in this paper.

A pollutant that has not yet received as much public or regulatory attention as gaseous or solid particulate emissions is engine generated noise. Excessive levels of noise can, however, be as harmful to human health and the environment as noxious gases. In a well-designed engine, mechanical noise can be kept to a minimum but the combustion process itself still generates noise, "combustion noise". Thus, if the combustion process is modified for exhaust emission control it can be expected that the level of noise generated by combustion will also be affected, albeit not necessarily adversely. As exhaust gas recirculation (EGR) is becoming an essential technology for NOx emission control in diesel engines, and, as this technique modifies the combustion process, it is important that the effects of using EGR on noise generation be identified.

Collaborative investigators in the UK and in Canada have undertaken both experimental and modelling strategies on nonair diesel engine performance. The results of preliminary simulation strategies reported in this paper indicate that existing air-breathing models can be suitably modified to predict nonair brake performance indicators to within 5% of experimental results. However, nonair ignition delay and heat release models will provide even greater accuracy and the preliminary development of such models is also reported

The effect of nonair mixtures on cycle-to-cycle variations of cylinder pressure characteristics was investigated experimentally with an indirect-injected (IDI) diesel engine, The engine intake temperature and pressure were maintained at normal air-breathing conditions when operated with nonair mixtures, Preliminary results indicate that increases in carbon dioxide concentration can cause significant cyclic variations. Moreover, the extent of such cyclic variations is notably influenced by the oxygen concentration and inert gas constituents of the working fluids.

The oceans have been used for almost five thousand years for military purposes, for the transportation of goods and people and, especially in this century, for recreational activities. Today the oceanic seaways still provide a vitally important transportation system and probably always will. They also contain rich resources of food, energy and minerals which have yet to be fully exploited but there is already growing concern that they are being contaminated by pollution originating not only from the populated coastal areas but also from the actual use of the seas by marine vehicles. The waste generated in shipping activities has invariably been dumped into the oceans, often indiscriminately and in ignorance of the effects. However, increasing environmental awareness has now led the civilian and military marine transportation sectors to focus on the elimination of ship based environmental hazards. These hazards can take the form of atmospheric pollution, such as exhaust gases, or seawater pollution, such as sewage discharge and garbage disposal. The environmentally unfriendly discharges from vessels are not always intentional, for example, grease from the steering mechanism and erosion of the toxic anti-fouling hull paint have only been recently identified as harmful agents. The purpose of this paper ismore » to review the actual and potential environmental problem associated with the operation of both surface ships and underwater vehicles. In addition, techniques and problems associated with the control or elimination of the hazards are discussed and areas for future research identified.« less