G. T. Reader

Effect of various working fluid compositions on combustion noise in diesel engines

Increasingroad traffic has brought about legislation aimed at reducing noise from vehcle engines. Noise is transmitted throughout the engine block and other rigidly attached components as vibration. These vibrations can exists across the entire spectrum of frequencies. When they are in the range at which a healthy human ear can hear they radiatefrom the engine structure as audible. This noise and vibration can create severe problems for the engine structure, its operators, and the surroundings. Engine noise can be grouped into one of three categories; air flow, mechanical and combustion noise. Most of previous research undertakenhas investigated means of reducing air flow and mechanical noise primarily through the use of dampers, better balancing techniques and acoustic enclosures. Such solutions require extensive and usually expensive physical modifications to the engine structure. However, reduction of the prima~y noise source, combustion noise, requires detailed insight into and modification of the combustion process itself. Combustion noise can be the predominant source of noise in diesel engines and in high compression lightweight gasoline engines. High compression ratio engines have a tendency to exhibit faster rates of combustion chamber pressure rise and are, therefore, more prone to elevatedlevels of combustion noise. Although not the only factor to effect combustion noise, rate of pressure rise is most definitely a primary parameter. In thls paper an investigation is reported on the effect whlch variation in intake mixture composition have on combustion noise in an indirect injection (IDI) hesel engine across a wide range of audible and inaudible frequencies. Pressure rise and rate of pressure rise are also monitored to provide a better understandmg of the relationshp between the combus tion process and noise production. Relationships were establishedrelating combustion noise levels, rate of pressure rise, intake mixture composition andload. These are given in here. Introduction The use of intake mixture modification through such techniques as exhaust Gas Recirculation (EGR) with sparkignition engines has become a common technique used for reducing the emissions of automobile pollutants. However, until recently especially outside of Europe, diesel engines were seldom equipped wi th similar environmentally beneficial EGR equipment. However, a form of EGR diesel unit, commonly called the closed cycle diesel, has been used and investigated sporadically for over 80 years for utilisation as an airindependent submarine power system [I]. Recent investigations into EGR systems have shown that the technique used to make the diesel operate independentof air may have many land based environmental benefits by being developedas a method of emission control for diesel engines

Low power Stirling engine for underwater vehicle applications

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.

The effect of exhaust gas recirculation on the combustion noise level of an indirect injection diesel engine

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 NO/sub x/ 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.

Small-scale liquefaction of hydrogen

Abstract Hydrogen may be stored compactly as a cryogenic liquid at low pressure and temperature, i.e. 20 K at atmospheric pressure. Gaseous hydrogen at normal temperature may be liquefied on a small scale using a cryogenic refrigerator (cryocooler). Stirling refrigerators are well suited to this duty. These machines operate on a closed thermodynamic regenerative cycle with compression and expansion of the working fluid (helium) at different temperature levels. Very low temperature Stirling refrigerators have several stages of expansion, typically two or three for a hydrogen liquefier. A concept for an electrically driven Stirling hydrogen liquefier of low capacity is described. Stirling machines can also be used as power systems converting heat to work. A second concept is described for a combustion heated Stirling — Stirling hydrogen liquefier. Conceptual design studies for both units have been carried out including computer simulation of the power system and cryocooler systems. These indicate the net energy flow and principal dimensional parameters permitting first order estimates of costs for prototype manufacture and the unit costs in series production.

Destruction of marine sewage using conventional engine technology

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 NO/sub x/ 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.

Application of Stirling Engines in the Oil and Gas Industry

Successful innovation is the product of a complex network of interactions, stretching from basic university research to diffusion of commercial innovations in the market. Essential to the network is the importance of seeing innovation in system-wide terms and not just as a matter of individual, standalone technologies. The innovation theme needs to pervade all areas of future energy research and development activity and specifically in the ability to develop, adopt, adapt and apply technology that provides for enhanced hydrocarbon energy natural resource development whilst providing low and near-zero emissions, including greenhouse gases. As technology develops to meet the challenges of a carbon-constrained world, the ability to control hydrocarbon combustion processes when using a combination of opportunity fuels will become even more important - Stirling cycle heat engines may offer distinct advantages when these new factors are taken into account. This is especially the case when the myriad of possible hydrocarbon fuels and wastes that are derived from the exploration and exploitation of the hydrocarbon energy industry are considered; this accommodating nature of the Stirling engine combustion system is essential to success in utilizing the varied compositions found in waste and fugitive hydrocarbon liquids found in current and future upstream petroleum operations. These engines are available in a wide range of sizes and operate very well under part-load conditions, thus making them well suited to the small and declining quantities of gas/liquid volumes encountered in oilfield productions. This paper reviews the opportunities for the utilization of Stirling engine systems in the Western Canadian Oil and Gas Industry.

Diesel-Electric Generators

The sections in this article are n n n1 nGenerator Applications n n2 nEngine Size, Classification, and Selection n n3 nEngine and Generator Set Ratings n n4 nBasic Concepts and Working Cycles of Engine Operation n n5 nPractical Aspects of Engine Operation n n6 nEnvironmental Aspects n n7 nOperations with Non-Air Intake Mixtures n n8 nAC Generators

Diesel engine integration into autonomous underwater vehicles

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 achieved The 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.

Performance of a 10 kW underwater diesel engine system

To operate in a nonair environment, a diesel engine must be supplied with a synthetic atmosphere which mimics the role of normally aspirated air. To determine the optimum synthetic atmosphere mixture, an intensive experimental investigation has been carried out by the authors using a specially developed test rig. Provision has been made on the test rig so that a number of different composition synthetic atmospheres can be produced. In this way, it has been possible to measure the effects of carbon dioxide ratios on the performance of the diesel engine. In addition to the shaft performance, power and fuel efficiency, exhaust gas emissions and combustion noise have also been measured. This paper details the operational principle of an underwater diesel engine and reports on the performance of such an engine whilst operating with high intake carbon dioxide levels.

Simulating the performance of non-air-breathing diesel engines

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.