Showing papers on "Diesel engine published in 2002"

A techno-economic comparison of power production by biomass fast pyrolysis with gasification and combustion

Abstract: This paper presents an assessment of the technical and economic performance of thermal processes to generate electricity from a wood chip feedstock by combustion, gasification and fast pyrolysis. The scope of the work begins with the delivery of a wood chip feedstock at a conversion plant and ends with the supply of electricity to the grid, incorporating wood chip preparation, thermal conversion, and electricity generation in dual fuel diesel engines. Net generating capacities of 1–20 MWe are evaluated. The techno-economic assessment is achieved through the development of a suite of models that are combined to give cost and performance data for the integrated system. The models include feed pretreatment, combustion, atmospheric and pressure gasification, fast pyrolysis with pyrolysis liquid storage and transport (an optional step in de-coupled systems) and diesel engine or turbine power generation. The models calculate system efficiencies, capital costs and production costs. An identical methodology is applied in the development of all the models so that all of the results are directly comparable. The electricity production costs have been calculated for 10th plant systems, indicating the costs that are achievable in the medium term after the high initial costs associated with novel technologies have reduced. The costs converge at the larger scale with the mean electricity price paid in the EU by a large consumer, and there is therefore potential for fast pyrolysis and diesel engine systems to sell electricity directly to large consumers or for on-site generation. However, competition will be fierce at all capacities since electricity production costs vary only slightly between the four biomass to electricity systems that are evaluated. Systems de-coupling is one way that the fast pyrolysis and diesel engine system can distinguish itself from the other conversion technologies. Evaluations in this work show that situations requiring several remote generators are much better served by a large fast pyrolysis plant that supplies fuel to de-coupled diesel engines than by constructing an entire close-coupled system at each generating site. Another advantage of de-coupling is that the fast pyrolysis conversion step and the diesel engine generation step can operate independently, with intermediate storage of the fast pyrolysis liquid fuel, increasing overall reliability. Peak load or seasonal power requirements would also benefit from de-coupling since a small fast pyrolysis plant could operate continuously to produce fuel that is stored for use in the engine on demand. Current electricity production costs for a fast pyrolysis and diesel engine system are 0.091/kWh at 1 MWe when learning effects are included. These systems are handicapped by the typical characteristics of a novel technology: high capital cost, high labour, and low reliability. As such the more established combustion and steam cycle produces lower cost electricity under current conditions. The fast pyrolysis and diesel engine system is a low capital cost option but it also suffers from relatively low system efficiency particularly at high capacities. This low efficiency is the result of a low conversion efficiency of feed energy into the pyrolysis liquid, because of the energy in the char by-product. A sensitivity analysis has highlighted the high impact on electricity production costs of the fast pyrolysis liquids yield. The liquids yield should be set realistically during design, and it should be maintained in practice by careful attention to plant operation and feed quality. Another problem is the high power consumption during feedstock grinding. Efficiencies may be enhanced in ablative fast pyrolysis which can tolerate a chipped feedstock. This has yet to be demonstrated at commercial scale. In summary, the fast pyrolysis and diesel engine system has great potential to generate electricity at a profit in the long term, and at a lower cost than any other biomass to electricity system at small scale. This future viability can only be achieved through the construction of early plant that could, in the short term, be more expensive than the combustion alternative. Profitability in the short term can best be achieved by exploiting niches in the market place and specific features of fast pyrolysis. These include: •countries or regions with fiscal incentives for renewable energy such as premium electricity prices or capital grants; •locations with high electricity prices so that electricity can be sold direct to large consumers or generated on-site by companies who wish to reduce their consumption from the grid; •waste disposal opportunities where feedstocks can attract a gate fee rather than incur a cost; •the ability to store fast pyrolysis liquids as a buffer against shutdowns or as a fuel for peak-load generating plant; •de-coupling opportunities where a large, single pyrolysis plant supplies fuel to several small and remote generators; •small-scale combined heat and power opportunities; •sales of the excess char, although a market has yet to be established for this by-product; and •potential co-production of speciality chemicals and fuel for power generation in fast pyrolysis systems.

Source reconciliation of atmospheric gas-phase and particle-phase pollutants during a severe photochemical smog episode

Abstract: A comprehensive organic compound-based receptor model is developed that can simultaneously apportion the source contributions to atmospheric gas-phase organic compounds, semivolatile organic compounds, fine particle organic compounds, and fine particle mass. The model is applied to ambient data collected at four sites in the south coast region of California during a severe summertime photochemical smog episode, where the model determines the direct primary contributions to atmospheric pollutants from 11 distinct air pollution source types. The 11 sources included in the model are gasoline-powered motor vehicle exhaust, diesel engine exhaust, whole gasoline vapors, gasoline headspace vapors, organic solvent vapors, whole diesel fuel, paved road dust, tire wear debris, meat cooking exhaust, natural gas leakage, and vegetative detritus. Gasoline engine exhaust plus whole gasoline vapors are the predominant sources of volatile organic gases, while gasoline and diesel engine exhaust plus diesel fuel vapors dominate the emissions of semivolatile organic compounds from these sources during the episode studied at all four air monitoring sites. The atmospheric fine particle organic compound mass was composed of noticeable contributions from gasoline-powered motor vehicle exhaust, diesel engine exhaust, meat cooking, and paved road dust with smaller but quantifiable contributions from vegetative detritus and tire wear debris. In addition, secondary organic aerosol, which is formed from the low-vapor pressure products of gas-phase chemical reactions, is found to be a major source of fine particle organic compound mass under the severe photochemical smog conditions studied here. The concentrations of secondary organic aerosol calculated in the present study are compared with previous fine particle source apportionment results for less intense photochemical smog conditions. It is shown that estimated secondary organic aerosol concentrations correlate fairly well with the concentrations of 1,2-benzenedicarboxylic acid in the atmospheric fine particle mass, indicating that aromatic diacids may be useful in the quantification of certain sources of secondary organic aerosol in the atmosphere.

Brassica carinata as an alternative oil crop for the production of biodiesel in Italy: engine performance and regulated and unregulated exhaust emissions.

Abstract: A comparison of the performance of Brassica carinata oil-derived biodiesel with a commercial rapeseed oil-derived biodiesel and petroleum diesel fuel is discussed as regards engine performance and regulated and unregulated exhaust emissions. B. carinata is an oil crop that can be cultivated in coastal areas of central-southern Italy, where it is more difficult to achieve the productivity potentials of Brassica napus (by far the most common rapeseed cultivated in continental Europe). Experimental tests were carried out on a turbocharged direct injection passenger car diesel engine fueled with 100% biodiesel. The unregulated exhaust emissions were characterized by determining the SOOT and soluble organic fraction content in the particulate matter, together with analysis of the content and speciation of polycyclic aromatic hydrocarbons, some of which are potentially carcinogenic, and of carbonyl compounds (aldehydes, ketones) that act as ozone precursors. B. carinata and commercial biodiesel behaved similarl...

The effects of the catalytic converter and fuel sulfur level on motor vehicle particulate matter emissions: light duty diesel vehicles.

Abstract: Wind tunnel measurements and direct tailpipe particulate matter (PM) sampling are utilized to examine how the combination of oxidation catalyst and fuel sulfur content affects the nature and quantity of PM emissions from the exhaust of a light duty diesel truck. When low sulfur fuel (4 ppm) is used, or when high sulfur (350 ppm) fuel is employed without an active catalyst present, a single log-normal distribution of exhaust particles is observed with a number mean diameter in the range of 70−83 nm. In the absence of the oxidation catalyst, the high sulfur level has at most a modest effect on particle emissions (<50%) and a minor effect on particle size (<5%). In combination with the active oxidation catalyst tested, high sulfur fuel can lead to a second, nanoparticle, mode, which appears at ∼20 nm during high speed operation (70 mph), but is not present at low speed (40 mph). A thermodenuder significantly reduces the nanoparticle mode when set to temperatures above ∼200 °C, suggesting that these particles...

Method of initiating regeneration of a particulate filter for a direct-injection diesel engine with a common rail injection system

Abstract: A method of initiating regeneration of a particulate filter for a diesel engine having a common rail injection system permitting, at each engine cycle and in each cylinder of the engine, a fuel injection strategy performing one or more of the following injections; a main injection; a first pre-injection preceding the main injection and performed at the compression stroke; a second pre-injection preceding the main injection and following the first pre-injection; a first post-injection following the main injection; and a second post-injection following the first post-injection and performed at the exhaust stroke; the second pre-injection and the first post-injection being performed close enough to the main injection to participate, together with the main injection, in the actual fuel combustion phase, and wherein the timing of one or more of the injections performed is varied with respect to the timing of the injections in particulate filter non-regenerating conditions.

Effect of Oxygenated Fuel on Combustion and Emissions in a Light-Duty Turbo Diesel Engine

Abstract: In previous studies on a single-cylinder IDI diesel engine and a V-8 DI turbo diesel engine, significant reductions in particulate matter emissions were observed with the blends of glycol ethers in diesel fuel. In this study, experiments on the effects of oxygenated fuels on emissions and combustion were performed in a 4-cylinder TDI diesel engine. A blend of 20 wt % monoglyme and 80 wt % diglyme, referred to as CETANER, has been examined as a diesel reformulating agent. Blend ratios were considered to provide approximately 2, 4, and 6 wt % oxygen to low-sulfur diesel fuel. Gaseous and particulate emission measurements, as well as heat release rate analysis, have been used to address how emissions and combustion scale with increasing weight percent oxygen in the fuel. The results demonstrate that the oxygenated fuel provides significant reduction in particulate matter with a small penalty on NOx emission, especially at high load. This oxygenated fuel effect may result from an enhanced concentration of oxy...

A comparison of combustion characteristics of waste cooking oil with diesel as fuel in a direct injection diesel engine

Abstract: The use of waste cooking oil (WCO) as an alternative to diesel in engines has advantages from both economic and environmental standpoints. Typical of vegetable oils, WCO has a higher viscosity, leading to a general perception that its use is likely to have an adverse effect on the fuel injection system and consequent combustion process. In the present investigation, tests were carried out to determine engine performance and combustion analysis as well as emissions for both WCO and diesel. It was observed that because of the shorter ignition delay the premixed combustion phase of WCO was less intense than that of diesel. However, because of the corresponding smaller combustion volume, the peak pressures were on average 1.5 bar higher and occurred 1.1°-3.8° earlier than for diesel. This early peaking characteristic requires careful attention to ensure that, while running with WCO, the peak pressure takes place marginally after top dead centre for efficient operation. In terms of emissions of CO, NO ...

Factors Affecting Heavy-Duty Diesel Vehicle Emissions

Abstract: Societal and governmental pressures to reduce diesel exhaust emissions are reflected in the existing and projected future heavy-duty certification standards of these emissions. Various factors affect the amount of emissions produced by a heterogeneous charge diesel engine in any given situation, but these are poorly quantified in the existing literature. The parameters that most heavily affect the emissions from compression ignition engine-powered vehicles include vehicle class and weight, driving cycle, vehicle vocation, fuel type, engine exhaust aftertreatment, vehicle age, and the terrain traveled. In addition, engine control effects (such as injection timing strategies) on measured emissions can be significant. Knowing the effect of each aspect of engine and vehicle operation on the emissions from diesel engines is useful in determining methods for reducing these emissions and in assessing the need for improvement in inventory models. The effects of each of these aspects have been quantified in this paper to provide an estimate of the impact each one has on the emissions of diesel engines.

Ultrafine PM emissions from natural gas, oxidation-catalyst diesel, and particle-trap diesel heavy-duty transit buses.

Abstract: This paper addresses how current technologies effective for reducing PM emissions of heavy-duty engines may affect the physical characteristics of the particles emitted. Three in-use transit bus configurations were compared in terms of submicron particle size distributions using simultaneous SMPS measurements under two dilution conditions, a minidiluter and the legislated constant volume sampler (CVS). The compressed natural gas (CNG) -fueled and diesel particulate filter (DPF) -equipped diesel configurations are two “green” alternatives to conventional diesel engines. The CNG bus in this study did not have an oxidation catalyst, whereas the diesel configurations (with and without particulate filter) employed catalysts. The DPF was a continuously regenerating trap (CRT). Particle size distributions were collected between 6 and 237 nm using 2-minute SMPS scans during idle and 55 mph steady-state cruise operation. Average particle size distributions collected during idle operation of the diesel baseline bus...

High Efficiency and Low Emissions from a Port-Injected Engine with Neat Alcohol Fuels

Abstract: Ongoing work with methanol- and ethanol-fueled engines at the EPA’s National Vehicle and Fuel Emissions Laboratory has demonstrated improved brake thermal efficiencies over the baseline diesel engine and low steady state NOx, HC and CO, along with inherently low PM emissions. In addition, the engine is expected to have significant system cost advantages compared with a similar diesel, mainly by virtue of its low-pressure port fuel injection (PFI) system. While recognizing the considerable challenge associated with cold start, the alcohol-fueled engine nonetheless offers the advantages of being a more efficient, cleaner alternative to gasoline and diesel engines. The unique EPA engine used for this work is a turbocharged, PFI spark-ignited 1.9L, 4-cylinder engine with 19.5:1 compression ratio. The engine operates unthrottled using stoichiometric fueling from full power to near idle conditions, using exhaust gas recirculation (EGR) and intake manifold pressure to modulate engine load. As a result, the engine, operating on methanol fuel, demonstrates better than 40% brake thermal efficiency from 6.5 to 15 bar BMEP at speeds ranging from 1200 to 3500 rpm, while achieving low steady state emissions using conventional aftertreatment strategies. Similar emissions levels were realized with ethanol fuel, but with slightly higher BSFC due to reduced spark authority at this compression ratio. These characteristics make the engine attractive for hybrid vehicle applications, for which it was initially developed, yet the significant expansion of the high-efficiency islands suggest that it may have broader appeal to conventional powertrain systems. With further refinement, this clean, more efficient and less expensive alternative to today’s petroleum-based IC engines should be considered as a bridging technology to the possible future of hydrogen as a transportation fuel.

Application of detailed chemistry and CFD for predicting direct injection HCCI engine combustion and emissions

Abstract: The present study applied a detailed chemical kinetic mechanism to simulate the combustion and emissions in a direct-injection homogeneous charge compression ignition (HCCI) engine. The engine is a heavy-duty diesel engine equipped with a pressure-swirl injector using gasoline as the fuel. The intake air was heated to help fuel vaporization to achieve HCCI conditions. The CHEMKIN code was implemented into KIVA-3V so that the chemistry is solved in the context of the engine computational fluid dynamics simulation. The effects of turbulent mixing on the reaction rate were considered. The computations started from intake valve closure with the initial conditions provided by a one-dimensional cycle simulation code that can simulate the gas-exchange process. Good levels of agreement in combustion and emissions were obtained using the present model. Predicted cylinder pressures and heat release rates agreed well with measurements. The computational results showed that a lean and fairly homogeneous mixture was obtained under the current engine configurations. Relatively low gas temperature (with peak value only about 2000 K) was observed in the present HCCI combustion that produced low NOx emissions. The model also predicted the correct trends in unburned hydrocarbon and carbon monoxide emissions as the start-of-injection timing and engine load were varied. It was also found that the unburned hydrocarbons and carbon monoxide emissions increased drastically if the overall equivalence ratio was less than a certain limit, for example, 0.15, due to poor combustion.

Excess air factor control of diesel engine

Abstract: A diesel engine (1) provided with a NOx catalyst (28A) and a diesel particulate filter (28B) performs lean burn operation during normal running, rich burn operation during regeneration of the NOx catalyst (28A), operation under the stoichiometric air-fuel ratio during desulphating of the NOx catalyst (28A), and operation under a slightly lean air-fuel ratio to regenerate the filter after desulphating of the NOx catalyst (28A). When the lean burn operation is applied, a controller (31) first controls the fuel injection amount, and controls an air supply amount based on the fuel injection amount. When rich burn operation is applied, the controller (31) first controls the air supply amount and controls the fuel injection amount based on the air supply amount. Due to this control, the response of the excess air factor control is enhanced while preventing torque fluctuation accompanying the variation of the target excess air factor.

Device for purifying exhaust gas of diesel engines

Abstract: A diesel engine exhaust gas purifying device includes a first continuous regeneration type diesel particulate filter in the exhaust gas passage, a by-path by-passing a portion of the exhaust gas passage upstream of the first continuous regeneration type diesel particulate filter, a second continuous regeneration type diesel particulate filter in the by-path, a change-over valve in the exhaust gas passage between the ends of by-path, an exhaust gas temperature-elevating mechanism, an exhaust gas temperature region detecting mechanism, and a control mechanism for controlling the exhaust gas temperature-elevating mechanism and the change-over valve based on the exhaust gas temperature region. When the exhaust gas temperature region of the engine is in a temperature range lower than a predetermined temperature region, the control mechanism actuates the exhaust gas temperature-elevating mechanism and controls the change-over valve so that the exhaust gas passes through the second continuous regeneration type diesel particulate filter.

The Effect of Oxygenates on Diesel Engine Particulate Matter

Abstract: A summary is presented of experimental results obtained from a Cummins B5.9 175 hp, direct-injected diesel engine fueled with oxygenated diesel blends. The oxygenates tested were dimethoxy methane (DMM), diethyl ether, a blend of monoglyme and diglyme, and ethanol. The experimental results show that particulate matter (PM) reduction is controlled largely by the oxygen content of the blend fuel. For the fuels tested, the effect of chemical structure was observed to be small. Isotopic tracer tests with ethanol blends reveal that carbon from ethanol does contribute to soot formation, but is about 50% less likely to form soot when compared to carbon from the diesel portion of the fuel. Numerical modeling was carried out to investigate the effect of oxygenate addition on soot formation. This effort was conducted using a chemical kinetic mechanism incorporating n-heptane, DMM and ethanol chemistry, along with reactions describing soot formation. Results show that oxygenates reduce the production of soot precursors (and therefore soot and PM) through several key mechanisms. The first is due to the natural shift in pyrolysis and decomposition products. In addition, high radical concentrations produced by oxygenate addition promote carbon oxidation to CO and CO2, limiting carbon availability for soot precursor formation. Additionally, high radical concentrations (primarily OH) serve to limit aromatic ring growth and soot particle inception.

The Effects of Diesel-Ethanol Blends on Diesel Engine Performance

Abstract: The performance of a variable compression ratio compression ignition engine operating on ethanol-diesel fuel blends has been evaluated experimentally. We aimed to determine the optimum percentage of ethanol and the compression ratio of the engine that give the best performance and efficiency at the same time. The engine was operated with ethanol-diesel fuel blends having 2, 4, and 6% ethanol on a volume basis as well as on diesel fuel alone. The experiments were performed for the compression ratios of 19, 21, and 23. Experimental results indicate that the addition of 4% ethanol to diesel fuel increases power output and efficiency of the engine while it decreases specific fuel consumption for various compression ratios. The best efficiency was attained at the compression ratio of 21 with an increment ratio over 3.5%.

Exhaust emission purification system for diesel engine

Abstract: A first exhaust emission purification device first and a second exhaust emission purification device, each have a continuously regenerating type DPF and an SCR catalyst to constitute exhaust emission purification system for a diesel engine. When the exhaust gas temperature is within a low-temperature region lower than a predetermined temperature region, the exhaust gas temperature is raised.

An experimental analysis of low-temperature and premixed combustion for simultaneous reduction of NOx and particulate emissions in direct injection diesel engines:

Abstract: A new combustion concept, named MK (modulated kinetics) combustion, has been developed, which reduces NOx and smoke simultaneously through high exhaust gas recirculation (EGR) and retarded ...

Dynamic behaviours of piston rings and their practical impact. Part 2: Oil transport, friction and wear of ring/liner interface and the effects of piston and ring dynamics

Abstract: The paper discusses several important processes that have great impact on the lubrication between the top two rings and the liner. The analysis is conducted on the basis of the calculation results on a heavy-duty (HD) diesel engine using theoretical models. Oil supply mechanisms to different liner regions are analysed, and emphasis is given to the oil transport to the top liner region that is found critical to friction, wear and oil consumption in HD diesel engines. Additionally, the paper discusses the oil supply to the second ring, its uncertainties and the effect on the prediction of the performance of the top two rings. Furthermore, the effects of dynamics of the piston and rings on friction, wear and oil transport are illustrated and the effects of bore distortion on oil transport are discussed.For practical purposes, a formula to describe the second ring running surface profile is given based on simple geometrical constraint. A new truncation method is rendered for plateau surface roughness ...

Diesel Soot Oxidation with NO2: Engine Experiments and Simulations

Abstract: The diesel particulate filters (DPFs) technology has impressively advanced especially during the last years, driven by the interest in the reduction of automobile particulate emissions. This paper is concerned with the effect of NO2 as an active oxidation agent in the regeneration process of the soot accumulated in the particulate filter. Experiments at realistic conditions using a diesel engine equipped with a standard oxidation catalyst and a particulate filter are carried out at a wide range of operating conditions. These results are used to validate an already available mathematical model of the NO2-assisted regeneration phenomena in the particulate filter. The combined use of experimental and modeling results provides interesting conclusions regarding the significance and the chemistry of the reaction of soot with NO2. The advantages and drawbacks of such an approach compared to standard laboratory synthetic gas studies are discussed. The agreement between experimental and simulation results in terms...