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Medium speed diesel engines are well established today as a power source for heavy transport and stationary applications and it appears that they will remain so in the future. However, emission legislation becomes stricter, reducing the emission limits of various pollutants to extremely low values. Currently, many techniques that are well established for automotive diesel engines (common rail, after treatment, exhaust gas recirculation - EGR, …) are being tested on these large engines. Application of these techniques is far from straightforward given the different requirements and boundary conditions (fuel quality, durability, …). This paper reports on the development and experimental results of cooled, high pressure loop EGR operation on a 1326kW four stroke turbocharged medium speed diesel engine, with the primary goal of reducing the emission of oxides of nitrogen (NOx). Measurements were performed at various loads and for several EGR rates.

Hydrogen-fueled internal combustion engines (H₂ICEs) are an affordable, practical and efficient technology to introduce the use of hydrogen as an energy carrier. They are practical as they offer fuel flexibility, furthermore the specific properties of hydrogen (wide flammability limits, high flame speeds) enable a dedicated H₂ICE to reach high efficiencies, bettering hydrocarbon-fueled ICEs and approaching fuel cell efficiencies. The easiest way to introduce H₂ICE vehicles is through converting engines to bi-fuel operation by mounting a port fuel injection (PFI) system for hydrogen. However, for naturally aspirated engines this implies a large power penalty due to loss in volumetric efficiency and occurrence of abnormal combustion. The present paper reports measurements on a single-cylinder hydrogen PFI engine equipped with an exhaust gas recirculation (EGR) system and a supercharging set-up.

In 2004 the European Parliament ratified the Euro III and IV standards limiting the pollutant emission of, among others, rail and marine diesel engines. In these sectors, it is particularly important to keep any fuel consumption penalty, when reducing emissions, to a strict minimum. Furthermore, exhaust gas after treatment is mostly avoided for cost reasons. Thus, manufacturers are looking to pretreatment of fuels, alternative fuels, and limiting engine-out emissions as ways to attain the required emission levels. This paper discusses the experimental work done on a 1324 kW, 1000 rpm six cylinder marine diesel engine equipped with mechanical unit injectors. The aim was to determine the influence of compression ratio and fuel injection parameters on engine-out emissions, with emphasis on NOx emissions. A range of fuel injection parameters were examined, varying the start of injection, pump plunger diameter, injection pressure, and injector nozzle geometry.

There is a growing consensus that there will not be a single alternative to fossil fuels, but rather different fuels, fuel feedstocks, engine types and operating strategies. For stationary diesel engines, straight vegetable oils are an interesting alternative to fossil diesel, because of their potential for lower life cycle greenhouse gas emissions. Using animal fats is also compelling, as it does not imply the cultivation of oil-bearing seeds and related emissions, not to mention the ‘food versus fuel’ debate. The aim of the present work is to correlate engine performance and durability with the properties (composition) of these alternative fuels, to provide a basis from which standards can be formulated for the properties of oils and fats to be used as engine fuel. Tests on different oils and fats are reported.

Hydrogen-fueled internal combustion engines equipped with port fuel injection offer a cheap alternative to fuel cells and can be run in bi-fuel operation side-stepping the chicken and egg problem of availability of hydrogen fueling station versus hydrogen vehicle. Hydrogen engines with external mixture formation have a significantly lower power output than gasoline engines. The main causes are the lower volumetric energy density of the externally formed hydrogen-air mixture and the occurrence of abnormal combustion phenomena (mainly backfire). Two engine test benches were used to investigate different means of compensating for this power loss, while keeping oxides of nitrogen (NOx) emissions limited. A single cylinder research engine was used to study the effects of supercharging, combined with exhaust gas recirculation (EGR). Supercharging the engine results in an increase in power output.

Interest in alternative fuels is motivated by concerns for greenhouse gas accumulation, air quality, security of energy supply and of course the non-stop increasing crude oil and natural gas prices. Hydrogen usage can be a solution for these problems. Hydrogen plays the role of an energy carrier that has two major advantages: it can be generated from many sources and it is very clean in its use. One end-use technology that can handle hydrogen is the well-known internal combustion engine (ICE). However, before this technology can be put to use, it needs to be able to compete with conventionally fuelled power units. Particularly in terms of specific power output and NOX emissions, development work needs to be done. In the work described in this paper the main focus is on the combustion strategies for high efficiency and low NOx emissions. A comparison is made between lean burn and EGR (exhaust gas recirculation) strategies.

The literature on hydrogen fueled internal combustion engines is surprisingly extensive and papers have been published continuously from the 1930's up to the present day. Ghent University has been working on hydrogen engines for more than a decade. A summary of the most important findings, resulting from a literature study and the experimental work at Ghent University, is given in the present paper, to clarify some contradictory claims and ultimately to provide a comprehensive overview of the design features in which a dedicated hydrogen engine differs from traditionally fueled engines. Topics that are discussed include abnormal combustion (backfire, pre-ignition and knock), mixture formation techniques (carbureted, port injected, direct injection) and load control strategies (power output versus NOx trade-off).

During the last years natural gas is increasingly used as an alternative fuel for internal combustion engines, mainly because of the concern for the environment and the high gasoline prices. Natural gas can be stored by liquefaction, compression, or adsorption. When it is used in vehicles, natural gas is usually stored as compressed natural gas, (CNG), at pressures of about 20 MPa. Reducing the storage pressure is interesting as the energy necessary for compression is strongly reduced, the filling stations become less expensive and the necessary safety regulations are less stringent. With the adsorption of natural gas on activated carbon (ANG), the storage pressure is reduced to 5 MPa or less, and the designers get more freedom in tank design. In this paper, first an overview is given of the adsorption and desorption process and of the filling and emptying procedures of the tank. The equations of the isotherms are analysed and extended for multi component adsorption (guard bed).

Hydrogen is seen as one of the important energy vectors of the next century. Hydrogen as a renewable energy source, provides the potential for a sustainable development particularly in the transportation sector. Hydrogen-driven vehicles reduce both local as well as global emissions. The laboratory of transport technology (University of Gent) converted a General Motors Corporation/Crusader V-8 engine for hydrogen use. Once the engine is optimized, it will be built in a low-floor midsize hydrogen city bus for public demonstration. For a complete control of the combustion process and to increase the resistance to backfire (explosion of the air-fuel mixture in the inlet manifold), a sequential timed multipoint injection of hydrogen and an electronic management system is chosen. The results as a function of the engine parameters (ignition timing, injection timing and duration, injection pressure) are given.

The use of hydrogen in a spark ignited engine is accompanied by a significant risk for backfire and knock, especially at full load, where the richest mixture is used. In fact, when attempting to maximize engine power, knock can (and usually will) lead to runaway surface ignition and backfire without much delay. Since backfire (and knock) has to be avoided at all cost, an attempt was made to detect and quantify knock from the measured pressure traces. For future use knock detection, combined with multipoint timed hydrogen injection, offers the possibility to avoid backfire by temporarily cylinder deactivation. In a first attempt the standard method using the third derivative of the pressure was tried, but proved to be too insensitive to be of any practical use, even though knock was very audible and the pressure oscillations are easily visible on the measurements. This insensitivity is caused by the very fast combustion achieved with hydrogen, compared to other fuels.

The ignition delay in a diesel engine is generally seen as consisting of two different consecutive although overlapping phases: the physical and the chemical ignition delay. As is commonly accepted, the physical ignition delay corresponds to the mixture formation, and the chemical delay to the time necessary to get an exponential increase in the chemical reaction rate. In this paper it is shown that if the assumption is made that the ignition of the spray is started by the ignition of a single droplet, the physical ignition delay is determined by the chemical ignition delay. If the results of the ignition delay measurements reported in the literature are interpreted with respect to this ignition model, better understanding of diesel ignition is obtained.