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2015-04-14
Technical Paper
2015-01-1069
Philipp Baumann, Matthias Schroeder, Harald Kurz, Thomas Maier, Wolfgang Thiel, Udo Strehl
The continuous trend towards more resource efficient and less pollutant emitting individual traffic is reflected in a wide range of modern propulsion concepts including Plug-In Hybrid Electric Vehicles (PHEVs). This variety of increasingly complex powertrains is associated with a number of challenges to measure exhaust gas emissions. Although the conventional constant volume sampler (CVS) and exhaust gas measurement systems being a high precision emission measurement concept there are still questions to be answered: • Which measurement uncertainties have to be considered, such as mass transport of exhaust emissions from the transfer tube into the dilution tunnel during engine-off phases? • Is the tested PHEV influenced by the measurement system, e.g. catalyst cooling? • Can different types of PHEV be adequately tested with the existing exhaust emission measurement system and test procedure regarding the European emission legislation?
2015-04-14
Technical Paper
2015-01-0861
Matthew Younkins, Margaret S. Wooldridge, Brad A. Boyer
Hydrogen fueled internal combustion engines have potential for high thermal efficiencies; however, high efficiency conditions can produce high nitrogen oxide emissions (NOx) that are challenging to treat using conventional 3-way catalysts. This work presents the results of an experimental study to reduce NOx emissions while retaining high thermal efficiencies in a single-cylinder research engine fueled with hydrogen. Specifically, the effects on engine performance of the injection of water into the intake air charge were explored. The hydrogen fuel was injected into the cylinder directly. Several parameters were varied during the study, including the amount of water injected into the intake charge, the amount of fuel injected, the phasing of the fuel injection, the number of fuel injection events, and the ignition timing. The results were compared with expectations for a conventionally operated hydrogen engine where load was controlled through changes in equivalence ratio.
2015-04-14
Technical Paper
2015-01-1648
Hendrik Golzke, Heiko Holler, Wolfgang Friedrich, Philippe Leick, Ulrich Schoenauer, Andreas Dreizler
The spatial distribution of internal exhaust gas recirculation (EGR) is evaluated in an optically accessible direct injection spark ignition engine using near infrared laser absorption to visualize the distribution of the H2O molecule. The obtained overall internal exhaust gas recirculation compares well to gas-exchange cycle calculations and the spatial distributions are consistent with those measured with inverse LIF. The experimental procedures described in this report are designed to be simple and rapidly implemented without the need to resort to unusual optical components. The necessary spectral data of the selected absorption line is obtained from the HITEMP database and is validated with prior experiments carried out in a reference cell. Laser speckle in the images is effectively reduced using a ballistic diffuser.
2015-04-14
Technical Paper
2015-01-1730
Luca Romani, Giovanni Vichi, Giovanni Ferrara, Francesco Balduzzi, Paolo Trassi, Jacopo Fiaschi, Federico Tozzi
High specific fuel consumption and pollutant emissions are the main drawbacks of the small crankcase-scavenged two-stroke engine. The symmetrical timing of the scavenging ports combined with a carburetor or an indirect injection system leads to a lower scavenging efficiency than a four-stroke engine and to the short-circuit of fresh air-fuel mixture. The use of fuel supply systems as the indirect injection and the carburetor are the standard solutions for a small two-stroke engine equipment, due to necessity of reducing the complexity, weight, overall dimensions and costs. This paper presents the results of a detailed study on the application of an innovative Low Pressure Direct Injection system (LPDI) to an existing 300 cc cylinder formerly equipped with a carburetor. The proposed solution is characterized by two injectors working at 5 bar of injection pressure.
2015-04-14
Technical Paper
2015-01-1032
Z. Gerald Liu, Nathan Ottinger
U.S. and European nonroad diesel emissions regulations have led to the implementation of various exhaust aftertreatment solutions. One approved configuration, a vanadium-based selective catalytic reduction catalyst followed by an ammonia oxidation catalyst (V-SCR + AMOX), does not require the use of a diesel oxidation catalyst (DOC) or diesel particulate filter (DPF). While certification testing has shown the V-SCR + AMOX system to be capable of meeting the nitrogen oxides, carbon monoxide, and particulate matter requirements, open questions remain regarding the efficacy of this aftertreatment for volatile and nonvolatile organic emissions removal, especially since the removal of this class of compounds is generally attributed to both the DOC and DPF.
2015-04-14
Technical Paper
2015-01-1064
Ahmad Khalfan, Hu Li, Gordon Andrews
The tailpipe exhaust emissions were measured under real world urban driving conditions by using a EURO4 emissions compliant SI car equipped with an on-board heated FTIR, a differential GPS for velocity, altitude and position, thermal couples for temperatures, and a MAX fuel meter for transient fuel consumption. Emissions species were measured at 0.5 Hz. The tests were designed to enable cold start to occur into congested traffic, typical of the situation of people living alongside congested roads into a large city. The cold start was monitored through temperature measurements of the TWC front and rear face temperatures and lubricating oil temperatures. The emissions are presented to the end of the cold start, defined when the downstream TWC face temperature is hotter than the front face and above 400oC. Journeys at various times of the day were conducted to investigate traffic flow impacts on the cold start.
2015-04-14
Technical Paper
2015-01-1740
Kelsie S. Richmond, Stephen Henry, Russell Richmond, David Belton
Gasket materials are utilized for various different types of high temperature testing to prevent leaking at bolted joints. In particular, the automotive test services field uses flanged-gasket bolted exhaust joints to provide a convenient method for installation & removal of exhaust components like catalytic converters for aging, performance testing, etc. Recent improvements in the catalyst aging methods require flanged-gasket joints that can withstand exhaust temperatures as high as 1200°C. Gasket materials previously used in these applications like the graphite based gasket materials have exhibited physical breakdowns, severe leakage, and general thermal failures under these extreme temperatures. In order to prevent these leaks, metal-reinforced gasket materials in a number of configurations were introduced to these extreme temperature environments to evaluate their robustness to these temperatures.
2015-04-14
Technical Paper
2015-01-1065
Piotr Bielaczyc, Joseph Woodburn, Andrzej Szczotka
Increasing concern over anthropogenic greenhouse gas (GHG) emissions and general air quality and sustainability concerns has made the issue of fuel consumption by passenger cars a topic of great technical and political interest, at an international level. Carbon dioxide is the GHG of most importance regarding passenger cars running on conventional carbon-based fuels, with fleet average limits for CO2 emissions now in force in the European Union. In the USA, CO2 emissions are effectively subject to fleet average limits, although the metric employed is fuel economy – CO2 being the strongest controlling factor. In fact, regardless of the metric employed, 3 out of every 4 vehicles sold globally in 2012 were subject to some kind of energy efficiency regulation. In this context, accurate, repeatable measurement of CO2 emissions from passenger cars is vital for a variety of reasons, and these measurements are arguably more critical than in the past.
2015-04-14
Technical Paper
2015-01-1066
Frank Adam, Jan Schoenhaber, Armin Wagner
The introduction of vehicle emission and fuel economy standards (CO2) accelerates the introduction of new platform and powertrain combinations into the market place. All of these combinations will require unique exhaust gas aftertreatment systems that comply with the current emission legislation. The optimization of each unique aftertreatment solution requires the proper application of catalyst technologies at the lowest PGM concentrations. The optimization process needs to be fast, reliable, realistic, and cost attractive. It is arguable that performing the aftertreatment optimization on a chassis dynamometer is variable, time consuming and expensive. This work demonstrates how a synthetic gas bench (SGB) can be used to simulate stoichiometric engine emissions and aftertreatment performance. The SGB procedure duplicates the vehicle NEDC engine-out emissions and catalyst heat-up profiles.
2015-04-14
Technical Paper
2015-01-0989
Steve Schiller, Mark Brandl, Bruce Hoppenstedt, Korneel De Rudder
Diesel engine NOx emissions requirements have become increasingly stringent. Engine manufacturers have shown through the use of EGR and SCR technology that these requirements can be met. However, the demands for improved fuel efficiency, lower overall cost, and potential legislation to reduce NOx levels further increase the demand for higher DEF dosing rates. To meet this demand, a new DEF mixing technology has been developed. This paper describes the development of a compact, in-pipe mixer which utilizes an optimized wire mesh along with swirling flow to permit very high dosing rates without deposit formation while maintaining excellent mixing for high NOx reduction. Utilization of this technology makes it possible to reduce regeneration frequency, reduce the size of the SCR system, possibly eliminate the EGR system, and improve fuel efficiency through combustion enhancements.
2015-04-14
Technical Paper
2015-01-1010
Hongsuk Kim, Hoyeol Lee, Sunyoup Lee, Gyubaek Cho
A Diesel Particulate Filter (DPF) is an effective technology for reducing Particulate Matter (PM) emitted from diesel engines. In modern light duty diesel engines, DPF is regenerated by the in-cylinder fuel injection method. In this method, the fuel is injected into the combustion chamber during the expansion stroke to produce heat to burn out the PM trapped in the DPF. However, this method causes several problems, such as complicated engine torque control and oil dilution by fuel. Diesel fuel burners have many advantages in DPF regeneration. It enables DPF regeneration at any engine operating conditions with a lower fuel penalty compared with the in-cylinder fuel injection method. However, the combustion efficiencies of conventional diesel fuel burners are low at high load conditions due to the lack of oxygen and high speed of exhaust gas flow.
2015-04-14
Technical Paper
2015-01-1082
Xin Wang, Yunshan Ge, Linlin Liu, Huiming Gong
As a cheap, clean alternative, neat methanol and methanol gasoline are widely used as vehicle fuel in many provinces in China. Though burning methanol is able to curb carbonaceous pollutants from engine, NOx and carbonyls, in particular formaldehyde, remain concerns over atmospheric environment and public health. In this paper, regulated, carbonyl emissions together with particulate matter from a neat methanol/gasoline dual-fuel passenger car were examined over New European Driving Cycle (NEDC). The results yielded that, CO, HC and NOx from different fuel regimes were very similar. 14 kinds of carbonyl compounds in the exhaust samples were analyzed. In comparison with gasoline baseline, approximately 41.9% more carbonyls, majority of which were formaldehyde, acetaldehyde, propyl aldehyde and benzaldehyde, were discharged by methanol fuelling. Regarding particulate matter, a remarkable decrease of 63% in mass was obtained by fuelling with methanol.
2015-04-14
Technical Paper
2015-01-1062
E. Robert Fanick, Svitlana Kroll, Stefan Simescu
Semi-volatile organic compounds (SVOC) are a group of compounds that form during combustion or are present in the unburned portion of the fuel and lubricating oil and become part of the exhaust. Since these compounds are present in very low concentrations in diesel engine exhaust, the methods for sampling, handling, and analyzing these compounds are critical to obtaining good results. For many years, Southwest Research Institute® (SwRI®) developed and used test procedures for sampling SVOC in dilute engine exhaust during transient engine operation. These SVOC include such compounds as PAH, nitro-PAH (NPAH), polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF). The list of SVOC used for the target model compounds included: Sample procedures were adapted from ambient air testing methods. More recently, the Environmental Protection Agency (EPA) proposed their own draft method based on steady-state stack testing methods (EPA Reference Method 23A).
2015-04-14
Technical Paper
2015-01-1732
Marie-Josee Poitras, Deborah Rosenblatt, Jeffery Goodman
The focus of this study was the characterization and comparison of power-specific exhaust emission rates from a closed-loop small spark-ignited engine fuelled with ethanol and isobutanol gasoline blends. A 4-cycle Kohler ECH-630 engine certified to the Phase 3 emissions standards was operated over the G2 test cycle in its original configuration. This engine was equipped with electronic ignition, electronic fuel injection and an oxygen sensor. Certification gasoline fuel was splash-blended by percent volume with ethanol and isobutanol to result in the test blend levels of E10, E15, iB16 and iB8-E10 – a blend of ethanol, isobutanol and gasoline. Reductions in emission rates of carbon monoxide (up to 12.0% with the ethanol blends and up to 11.4% with the isobutanol blends) were achieved along with a reduction in total hydrocarbons (up to 11.2% with the ethanol blends and up to 8.1% with the isobutanol blends).
2015-04-14
Technical Paper
2015-01-1733
Michele De Gennaro, Elena Paffumi, Giorgio Martini, Urbano Manfredi, Roberto Rossi, Paolo Massari, Roberto Roasio
The increasing urbanization level of many countries around the globe has led to a rapid increase of mobility demand in cities. Although public transport may play an important role, there are still many people relying on private vehicles, and, especially in urban areas, motorcycles and scooters can combine handling and flexibility with lower cost of operation compared to passenger cars. However, in spite of their lower fuel demand, they might significantly contribute to air pollution, lagging behind cars in terms of emission performances. The aim of this paper is to provide the scientific community with the results of an exploratory test campaign on four different motorcycles, converted from gasoline to CNG by means of an after-market conversion kit, designed and developed by a joint collaboration between the Professional School “Leon Battista Alberti” (Rimini, Italy) and local specialized companies. A fifth motorcycle, similarly converted from gasoline to LPG, was also tested.
2015-04-14
Technical Paper
2015-01-0974
Aaron Brooker, Jeffrey Gonder, Sean Lopp, Jacob Ward
The ADOPT model is a light duty vehicle consumer choice and stock model supported by the U.S. Department of Energy Vehicle Technologies Office. It estimates technology improvement impacts on U.S. light duty vehicles sales, petroleum use, and greenhouse gas (GHG) emission. The ADOPT model uses a logit function to estimate sales. The majority of existing vehicle makes, models, and trims are included to fully represent the market. The logit function estimates their sales based on key attributes including vehicle price, fuel cost, acceleration, range and usable volume. The average importance of several attributes changes nonlinearly across its range, and changes with income. For several attributes, a distribution of importance around the average value is used to represent consumer heterogeneity. Engine downsizing and balancing net incentives/penalties are used to ensure that the Corporate Average Fuel Economy (CAFE) is met.
2015-04-14
Technical Paper
2015-01-0836
Behzad Rohani, Stephen Sungsan Park, Choongsik Bae
Low Temperature Combustion (LTC) is feasible only in lower load ranges so for the real world application of LTC, engine operation mode should frequently change back and forth from LTC mode in lower loads to conventional mode in higher loads. In this research, effect of injection strategy on smoothness and emissions of mode transition in a single cylinder heavy duty diesel engine is studied. The Exhaust Gas Recirculation (EGR) line was controlled by a servo-valve capable of opening or closing the EGR loop during only one engine cycle. Ten cycles after the EGR valve closure were taken as the transition period during which injection timing and quantity were shifted in various ways (i.e. injection strategies) and the effect on Indicated Mean Effective Pressure (IMEP) stability and emissions was studied.
2015-04-14
Technical Paper
2015-01-0776
Gerben Doornbos, Stina Hemdal, Daniel Dahl
This paper investigates how the rate of dilution applied can be extended while maintaining normal engine operation. Adding combustion residuals or additional air to a stoichiometric air fuel mixture creates advantages for an otto engine. The lower combustion temperature and higher theoretical efficiency results in reduced fuel consumption and decreased NOx formation. However dilution negatively affects the ignite-ability of the mixture and decreases the flame speed, possibly resulting in misfires and partial burns. Therefore a Volvo four-cylinder was equipped with a dual coil ignition system. This system made it possible to extend the ignition duration and vary the ignition current. Furthermore a sweep was performed in valve timing and type of dilution, air or combustion residuals. While maintaining a CoV < 5% the dual coil ignition system was able to extend the maximum lambda value by 10 to 15% depending on the load point.
2015-04-14
Technical Paper
2015-01-0831
Wonah Park, Youngchul Ra, Eric Kurtz, Werner Willems, Rolf D. Reitz
The low temperature combustion concept is very attractive for reducing NOx and soot emissions in diesel engines. However, it has potential limitations due to higher combustion noise and CO and HC emissions. A multiple injection strategy is an effective way to reduce unburned emissions and noise in LTC. In this paper, the effect of multiple injection strategies was investigated to reduce combustion noise and unburned emissions in LTC conditions. A hybrid surrogate fuel model was developed and validated, and was used to improve LTC predictions. Triple injection strategies were considered to find the role of each pulse and then optimized. The split ratio of the 1st and 2nd pulses fuel was found to determine the ignition delay. Increasing mass of the 1st pulse reduced unburned emissions and an increase of the 3rd pulse fuel amount reduced noise. It is concluded that the pulse split ratio can be used as a control factor for emissions and noise.
2015-04-14
Technical Paper
2015-01-1298
Sangram Jadhav
In this study, the optimization of experimental parameters, such as alcohol to oil molar ratio (1:08, 1:12 and 1:16), homogeneous catalyst loading (0.5, 1 and 1.5 wt %), homogeneous catalyst types (NaOH, KOH and NaOCH3) and reaction temperature (59, 64 and 69°C) on the transesterification for the production of Mangifera oil methyl ester (Biodiesel) was performed. Homogenous alkali catalyzed method has been used for biodiesel production by using homogenous catalyst such as NaOH, KOH and NaOCH3. The taguchi method was adopted as the experimental conditions from a limited number of experiments (Columns of L9 (3**4) Array) and contribution of each signal to noise factor calculated by ANOVA. The optimum experimental condition obtained from this study are; 1:16 methanol to oil molar ratio, KOH as the catalyst type, at a loading 1.5 wt% and a reaction temperature of 64°C played the most important role in the yield of Mangifera methyl ester.
2015-04-14
Technical Paper
2015-01-1067
Kenneth S. Price, Lin Wang, Thomas Pauly
Investigations of on-road emissions performance of vehicles have been made using various methods and instrumentation, some of which are very complex and costly. For the case of NOx emissions on Diesel road vehicles equipped with SCR, many of these vehicles are equipped with NOx sensor(s) for the purpose of OBD, and the ECM makes this data available via the diagnostic connector under the J1979 protocol for light duty vehicles. Data for mass air flow and fuel flow are also available, so the ongoing NOx mass flow can be calculated when the NOx sensors are active with no additional instrumentation. Heavy duty pickup trucks with SCR from 3 major US manufacturers, each certified to the optional chassis certification of 0.2 g/mi NOx on the FTP75, were obtained to be evaluated for SCR system behavior under normal driving conditions.
2015-04-14
Technical Paper
2015-01-1083
Robert L. Russell, Kent Johnson, Thomas Durbin, Patrick P. Chen, Jasna Tomic, Richard Parish
Emissions and fuel economy were determined over a light and a heavy driving cycle designed to represent the vehicles in-use driving patterns. The vehicles were 2010 Freightliner cabs equipped with Cummins engines with Selective Catalytic Reduction and Diesel Particulate Filter emission control systems. The carbon dioxide emissions for the hybrids were 30 to 36% lower than from the conventional. The hybrid nitrogen oxide emissions ranged from 30% higher to 20% lower than the conventional. The CO emissions were below the standards for both vehicles, but the percentage differences ranged from 18% to 2000% higher for the hybrids relative to the conventional. The high CO emissions for the hybrid are primarily related to the cooling of the Diesel Oxidation Catalyst during the 20 minute key-off soak between repeats of the driving cycles. With a 1 minute key-off soak the CO emissions from the hybrid were negative.
2015-04-14
Technical Paper
2015-01-0863
Hideyuki Ogawa, Peilong Zhao, Taiki Kato, Gen Shibata
Dual fuel combustion with premixed natural gas from an intake manifold as the main fuel and a small quantity of directly injected diesel fuel as the ignition source was investigated in a 0.83 L, single cylinder, super-charged, direct injection diesel engine with common rail fuel injection and low pressure loop cooled EGR. This type of combustion poses problems including large unburned emissions at low engine load conditions and limitations on the maximum load due to excessively rapid combustion. In this report the influence of compression ratios, the equivalence ratio of the natural gas, and the intake oxygen concentrations changed with cooled EGR on the combustion and emissions in the dual fuel operation was systematically investigated.
2015-04-14
Technical Paper
2015-01-1728
Sampoornananda Basrur, Pradeep Subramanian Srinivasan, Rahul Sharma, C Subramoniam
For small single cylinder engines (50-200cc) low speed stability (Engine idle RPM) always has been a difficult task to manage specially during cold weather. In order to improve the cold start ability without causing any inconvenience to the user, many scooter manufacturers have developed automatic choke systems. These automatic choke systems enrich the mixture depending on the engine operating temperature. With advent of Euro III and Bharat Stage IV legislations the cold start emission has become very critical. The objective of this study is to investigate the effect of automatic choke systems on CO, HC, NOx and CO2 emissions along with the temperature and light - off characteristics of catalytic converter of a 4 stroke scooter engine. The vehicle was tested on chassis dynamometer to investigate the emission on WMTC and ECER – 40 cycles with and without the automatic choke systems separately. Various choke operation durations and logics were studied.
2015-04-14
Technical Paper
2015-01-1011
Kazutake Ogyu, Toyoki Ogasawara, Yuichi Nagatsu, Yuya Yamamoto, Tatsuhiro Higuchi, Kazushige Ohno
The Particle Number (PN) emission limit is implemented for Direct Injection (DI) gasoline from Euro6 regulation in European region. The wall-flow type ceramic filter technology is an essential component for Diesel PN emission control, and will be one potential solution to be investigated for the future Gasoline DI PN emission control demand. Especially the requirement of lower pressure loss with smaller filter volume is very strong for the filter substrate for Gasoline DI compared to DPF, not to lose better fuel economy benefit of Gasoline DI engine. Re-crystallized SiC (R-SiC) has high strength as its own property, and enable for Gasoline Particulate Filter (GPF) design to make the wall thickness thinner and the porosity higher compared to the other ceramic materials.
2015-04-14
Technical Paper
2015-01-0993
Timothy V. Johnson
This paper will discuss the current state of the industry; where it needs to go and how to get there.
2015-04-14
Technical Paper
2015-01-1682
Sangram Jadhav, Madhukar S Tandale
In this study, the heterogeneous catalyst is used instead of homogeneous catalyst. This is because to overcome the problems faced viz; Catalyst recovery, Thermal stability and excessive use of water. This paper are shows the use of heterogeneous catalyst and optimization of experimental parameters, such as alcohol to oil molar ratio (1:08, 1:12 and 1:16), heterogeneous catalyst loading (0.5, 1 and 1.5 wt %), heterogeneous catalyst types (ZnO, MgO and CaO) and reaction temperature (59, 64 and 69°C) on the heterogeneous transesterification for the production of Mahua oil methyl ester (Biodiesel) was performed. Heterogeneous catalyzed method has been used for biodiesel production by using heterogeneous catalyst such as ZnO, MgO and CaO. The taguchi method was adopted as the experimental conditions from a limited number of experiments (Columns of L9 (3**4) Array) and contribution of each signal to noise factor calculated by ANOVA.
2015-04-14
Journal Article
2015-01-0984
Yang Zheng, Mengmeng Li, Michael Harold, Dan Luss
Current NOx emission reduction systems, selective catalytic reduction (SCR) and NOx storage and reduction (NSR), function well once achieving their operation temperature (typically ca. 250 oC) but have unsatisfactory NOx conversion at low exhaust temperature encountered during cold start and low load operation. The reduced exhaust temperature afforded by the higher fuel efficiency of advanced diesel engines further challenges the low-T NOx reduction. We report here a new concept with high low-T deNOx efficiency of up to 80% at a feed temperature of ca. 200 oC at relevant space velocities (70k h-1), using high-frequency hydrocarbon pulsing on a dual-layer LNT-SCR monolithic catalyst under lean conditions. This system has the potential to expand the operating temperature window of the conventional deNOx devices.
2015-04-14
Journal Article
2015-01-0986
Dieter Rauch, David Kubinski, Giovanni Cavataio, Devesh Upadhyay, Ralf Moos
For lowering the emissions of nitrogen oxides (NOx) from learn burn diesel engines, the selective catalytic reduction (SCR) with ammonia (NH3) as reducing agent has become serial standard as exhaust gas aftertreatment system. Zeolites are in use as catalyst material as they show a high SCR performance over a wide temperature window. A crucial step in the SCR reaction mechanism over zeolites is an initial adsorption of NH3 on the catalyst surface. Only then, NOX can be converted to harmless N2 and H2O by the zeolite catalyst. In this study, a Chabazite SSZ-13 with and without copper exchange was investigated. Due to NH3 adsorption, the proton conductivity of the zeolite increases distinctly. By monitoring these changes in the material properties of the catalyst material, the NH3 loading can be in operando determined. In this work, a radio frequency technique, based on the cavity perturbation method, was applied to measure these effects.
2015-04-14
Journal Article
2015-01-1061
Piotr Bielaczyc, Andrzej Szczotka, Joseph Woodburn
Technology for light-duty CNG (Compressed Natural Gas) vehicles is well established, and CNG vehicles have performance comparable to their petrol-fuelled equivalents. CNG is commonly used in spark ignition (SI) engines because their powertrains are relatively easy to convert from liquid to gaseous fuels. In addition, the importance of natural gas (NG) will increase significantly as fuel for transportation. Apart from its massive availability at attractive current market prices, its particular advantages in terms of CO2 (carbon dioxide) and exhaust emissions have led to the increased interest in NG as a fuel source. The aim of this paper was to explore the influence of CNG fuel on emissions in the context of the new Euro 6 emissions requirements and to compare exhaust emissions of the vehicles fuelled with CNG and with petrol.
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