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Estimation of Fuel Consumption and CO2 Emissions of Car Travel in Transportation Planning: the Lazio Region Case Study

Niccolò Cusano University-Paolo Delle Site
Sapienza University-Sonia Briglia
  • Technical Paper
  • 2019-24-0252
To be published on 2019-10-07 by SAE International in United States
The reduction of oil dependence and CO2 emissions have been included in the set of policy objectives by the European Union, according to the latest White Paper on transportation. Car travel is heavily dependent on oil, with minor exceptions represented by CNG (compressed natural gas) and all-electric vehicles. There is a tight relationship between CO2 emissions, almost unanimously recognized as main determinant of climate change, and fuel consumption. The paper provides a comparative analysis of two methods that can be used in transportation planning for the estimation of fuel consumption and CO2 emissions of car travel. The first method uses consumption and emission factors per vehicle-km travelled that are based on average network speed. The second method uses consumption and emission factors that are specific of the individual links of the network. In the second case, the link-specific average speed and flow that result from the assignment of the origin-destination travel demand matrix to the road network, subject to congestion, are the inputs of consumption and emission estimation. Link-specific travel times and flows, in a…

Effects of Prechamber on Efficiency Improvement and Emissions Reduction of a SI Engine Fuelled with Gasoline and CNG

Istituto Motori CNR-Paolo Sementa, Francesco Catapano, SILVANA Di Iorio, Bianca Maria Vaglieco
  • Technical Paper
  • 2019-24-0236
To be published on 2019-10-07 by SAE International in United States
The permanent aim of the automotive industry is the further improvement of the engine efficiency and the simultaneous pollutant emissions reduction. The aim of the study was the optimization of the gasoline and compressed natural gas (CNG) combustion by means of a passive prechamber. This analysis allowed the improvement of the engine efficiency in lean-burn operation condition too. The investigation was carried out in an real small Spark Ignition (SI) engine fueled with Gasoline and CNG and equipped with a proper designed passive prechamber. In particular, Gasoline and CNG were used to analyze the effects of the prechamber on engine performance and associated pollutant emissions. Indicated Mean Effective Pressure, Heat Release Rate and Mass Burned Fraction were used to evaluate the effects on engine performance. Gaseous emissions were measured as well. Particulate Mass, Number and Size Distributions were analyzed. Emissions samples were taken from the exhaust flow, just downstream of the valves. Opacity was measured downstream the Three-Way Catalyst. Three different engine speeds were investigated, namely 2000, 3000 and 4000 rpm. Stoichiometric and lean condition…

Experimental Characterization of Methane Direct Injection From an Outward-Opening Poppet-Valve Injector

Istituto Motori CNR-Maurizio Lazzaro, Francesco Catapano, Paolo Sementa
  • Technical Paper
  • 2019-24-0135
To be published on 2019-09-09 by SAE International in United States
The in-cylinder direct injection of natural gas represents a further step towards cleaner and more efficient internal combustion engines (ICE). However, the injector design and its characterization, either experimentally or from numerical simulation, is challenging because of the complex fluid dynamics related to gas compressibility. In this work, the underexpanded flow of methane from an outward-opening poppet-valve injector has been experimentally characterized by Schlieren and Shadowgraph high-speed imaging. The jet evolution was also followed through Mie-scattering imaging using n-heptane droplets as a tracer. The investigation has been performed at ambient temperature and pressure and different nozzle pressure ratios (NPR) ranging from 10 to 17. The gaseous jet has been characterized in terms of its macroscale parameters.

A Coupled Tabulated Kinetics and Flame Propagation Model for the Simulation of Fumigated Medium Speed Dual-Fuel Engines

Ghent University-Gilles Decan
Lund University-Sebastian Verhelst
  • Technical Paper
  • 2019-24-0098
To be published on 2019-09-09 by SAE International in United States
The present work describes the numerical modeling of medium-speed marine engines, operating under a fumigated dual-fuel concept, i.e. with the second fuel injected in the ports. Due to the need to reduce engine-out emissions while maintaining engine efficiency, manufacturers are investigating new engine technologies. In the maritime industry, a promising technology to achieve these goals is that of fumigated dual-fuel engines, allowing a large amount of diesel to be replaced by a premixed fuel. To fully optimize the operational parameters of such a large maritime engine, computational fluid dynamics can be very helpful. Accurately describing the combustion process in such an engine is key, as the prediction of the heat release and the pollutant formation is crucial. Auto-ignition of the diesel fuel needs to be captured, followed by the combustion and flame propagation of the premixed fuel. In this work, an approach based on tabulated kinetics has been used, to include detailed chemistry while still maintaining acceptable computation times. To allow for the modeling of a fumigated dual-fuel engine, it has been extending with a…

Literature Review on Dual-Fuel Combustion Modelling

Lund University-Menno Merts, Sebastian Verhelst
  • Technical Paper
  • 2019-24-0120
To be published on 2019-09-09 by SAE International in United States
In the search for low greenhouse gas propulsion, the dual fuel engine provides a solution to use low carbon fuel at diesel-like high efficiency. Also a lower emission of NOx and particles can be achieved by replacing a substantial part of the diesel fuel by for example natural gas. Limitations can be found in excessively high heat release rate (combustion-knock), and high methane emissions. These limitations are strongly influenced by operating parameters and properties of the used (bio)-gas. To find the dominant relations between fuel properties, operating parameters and the heat release rate and methane emissions, a combustion model is beneficial. Such a model can be used for optimizing the process, or can even be used in real time control. As precursor for such a model, the current state of art of dual fuel combustion modelling is investigated in this work. The focus is on high speed dual fuel engines for heavy duty and marine applications, with a varying gas/diesel ratio. Modelling is limited to the closed part of the 4-stroke engine cycle. A methodology…

Effect of Methane Number in a Diesel Engine Converted to Natural Gas Spark Ignition

Universita degli Studi di Perugia-Luca Ambrogi, Michele Battistoni, Lorenzo Gasbarro
West Virginia Univ.-Jinlong Liu, Cosmin Dumitrescu
  • Technical Paper
  • 2019-24-0008
To be published on 2019-09-09 by SAE International in United States
Natural gas (NG) is an alternative fuel for spark-ignition engines. In addition to its cleaner combustion, recent breakthroughs in drilling technologies increased its availability and lowered its cost. NG consists of mostly methane, but it also contains heavier hydrocarbons and inert diluents, the levels of which vary substantially with geographical source, time of year, and treatments applied during production or transportation. To investigate the effects of NG composition on engine performance and emissions, a 3D CFD model of a heavy-duty diesel engine retrofitted to spark ignition operations simulated engine operation under lean-combustion, low-speed, and medium load conditions. To eliminate the effect of different gas energy density, three NG blends of similar lower heating value but different H/C ratio have been investigated at fixed spark timing. The results indicated that a lower H/C ratio increased flame propagation and thus increased in-cylinder pressure and indicated mean effective pressure. In addition, the lower H/C ratio increased thermal efficiency despite the higher heat transfer, most probably due to the more advanced combustion phasing. Also, a higher H/C ratio reduced…

Experimental and Numerical Analysis of a Dual Fuel Operation of Turbocharged Engine at Mid-High Load

Univ. of Zagreb-Darko Kozarac, Mladen Bozic, Ante Vucetic, Josip Krajnovic, Momir Sjeric
  • Technical Paper
  • 2019-24-0122
To be published on 2019-09-09 by SAE International in United States
Due to the potential benefits in lowering of the CO2 emissions and lowering of the cost of fuel, internal combustion engines fueled by natural gas are an attractive alternative to conventional diesel or gasoline engines. In compression ignition engines natural gas is used in a dual fuel combustion mode where the premixed mixture of natural gas and air is ignited by a small amount of directly injected diesel fuel. At constant intake pressure the load is varied by the total fuel mass, i.e. by the excess air ratio, with specific limit on the highest possible excess air ratio. If duel fuel combustion mode is used on a turbocharged engine with the variable geometry turbocharger, the mid-high load operating points can be obtained with number of different combinations of intake pressures and excess air ratios. Besides the impact on the combustion the specific combination of intake pressure - excess air ratio also has impact on the exhaust back pressure caused by the turbocharger and consequently on the obtained brake efficiency. In addition to the intake pressure…

Experimental Investigation of Combustion Characteristics in a Heavy-Duty Compression-Ignition Engine Retrofitted to Natural-Gas Spark-Ignition Operation

West Virginia University-Jinlong Liu, Cosmin Dumitrescu
  • Technical Paper
  • 2019-24-0124
To be published on 2019-09-09 by SAE International in United States
The conversion of existing diesel engines to natural gas operation can reduce U.S. dependence on petroleum imports and curtail engine-out emissions. Diesel compression ignition engines can be modified to NG spark ignition, by replacing the diesel injector with a NG spark plug and by fumigating NG in the intake manifold, to increase utilization of natural gas heavy-duty transportation sector. As the original diesel piston is maintained during conversion to decrease engine modification cost, the major of this study was to investigate the lean-burn characteristic of natural gas burning in this bowl-in-piston combustion chamber, which can accelerate the introduction of heavy-duty natural gas vehicles. Data analysis from engine experiments that changed spark timing indicated a two-stage combustion process in such retrofitted engines, which is different from traditional spark ignition engines. Inside-bowl burning is one combustion stage which experienced fast flame propagation and burned majority of fuel mass. An important mass trapped in the squish region but burned more slowly formed the other combustion stage. This combustion feature contributed to an almost identical end of combustion in…

Integrated CFD-Experimental Methodology for the Study of a Dual Fuel Heavy Duty Diesel Engine

Brunel University London-Vinícius Pedrozo, Hua Zhao
University of Napoli Federico II-Maria Cristina Cameretti, Roberta De Robbio, Raffaele Tuccillo
  • Technical Paper
  • 2019-24-0093
To be published on 2019-09-09 by SAE International in United States
This paper deals with the experimental and numerical investigation of a 2.0 litre single cylinder Heavy Duty Diesel Engine fuelled by natural gas and diesel oil in Dual Fuel mode. Due to the gaseous nature of the main fuel and to the high compression ratio of the diesel engine, reduced emissions can be obtained. An experimental study has been carried out at three different load level (25%, 50% and 75% of full engine load). Basing on experimental data, the authors’ methodology is based on the use of one-dimensional and 3-dimensional models. The former is able to perform the whole engine with faster simulations while the latter can study deeply the even more complex phenomena (turbulence, combustion, etc.), due to the presence and to the interaction of the two fuels, which occur in the cylinder for the most interesting operating conditions. Thus the 3-D model in KIVA-3V code has been calibrated in order to fairly reproduce the pressure curves and consequently to reach the appointed value of Indicated Mean Effective Pressure which is the index of…

Heavy-Duty Compression-Ignition Engines Retrofitted to Spark-Ignition Operation Fueled with Natural Gas

Universita degli Studi di Perugia-Lorenzo Gasbarro, Michele Battistoni, Luca Ambrogi
West Virginia Univ-Jinlong Liu, Cosmin Dumitrescu, Christopher Ulishney
  • Technical Paper
  • 2019-24-0030
To be published on 2019-09-09 by SAE International in United States
Natural gas is a promising alternative gaseous fuel due to its availability, economic, and environmental benefits. A solution to increase its use in the heavy-duty transportation sector is to convert existing heavy-duty compression ignition engines to spark-ignition operation by replacing the fuel injector with a spark plug and injecting the natural gas inside the intake manifold. The use of numerical simulations to design and optimize the natural gas combustion in such retrofitted engines can benefit both engine efficiency and emission. However, experimental data of natural gas combustion inside a bowl-in-piston chamber is limited. Consequently, the goal of this study was to provide high-quality experimental data from such a converted engine fueled with methane and operated at steady-state conditions, exploring variations in spark timing, engine speed and equivalence ratio. The results showed that a higher engine speed reduced the motoring pressure, advanced maximum brake torque timing, and reduced the power output per cycle. Moreover, advanced spark timing increased and advanced the cylinder pressure, and increased both hydrocarbon and nitrogen oxides emissions. Leaner operation retarded the flame…