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Viewing 1 to 30 of 20042
Technical Paper
2014-04-15
Rakesh Kumar Maurya, Avinash Kumar Agarwal
Homogeneous charge compression ignition (HCCI) engines are attracting attention as next-generation internal combustion engines mainly because of very low NOx and PM emission potential and excellent thermal efficiency. Particulate emissions from HCCI engines have been usually considered negligible however recent studies suggest that PM number emissions from HCCI engines cannot be neglected. This study is therefore conducted on a modified four cylinder diesel engine to investigate this aspect of HCCI technology. One cylinder of the engine is modified to operate in HCCI mode for the experiments and port fuel injection technique is used for preparing homogenous charge in this cylinder. Experiments are conducted at 1200 and 2400 rpm engine speeds using gasoline, ethanol, methanol and butanol fuels. A partial flow dilution tunnel was employed to measure the mass of the particulates emitted on a pre-conditioned filter paper. The collected particulate matter (PM) was subjected to chemical analyses in order to assess the amount of Benzene Soluble Organic Fraction (BSOF) and trace metals (marker of toxicity) using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES).
Technical Paper
2014-04-01
Karthikeyan N, Anish Gokhale, Narendra Bansode
Abstract The Continuous Variable Transmission (CVT) in scooters is used to transmit the power from the engine to the wheels. The CVT transmission consists of a drive pulley and a driven pulley connected to each other through a belt. The centrifugal clutch is attached to the rear pulley which transmits the power to the wheel. The engagement and disengagement of the clutch generates heat and friction heat is generated between the belt and pulley, thereby requiring continuous external cooling for its safe operation. A centrifugal fan is employed for cooling of the CVT belt. Since the cooling fan takes air from atmosphere, there is always a possibility of dust from the atmosphere entering the system, which might cause wear of pulley and belt, thereby decreasing the performance of the transmission system. The objective of the work is to analyze the dust ingress pattern in to CVT housing. The work aims at simulating the possible conditions for dust entry into the CVT housing for a complete scooter and the study of different design proposals to minimize the dust entry without compromising the cooling requirement of CVT.
Technical Paper
2014-04-01
Georgios Fontaras, Panagiota Dilara, Michael Berner, Theo Volkers, Antonius Kies, Martin Rexeis, Stefan Hausberger
Due to the diversity of Heavy Duty Vehicles (HDV), the European CO2 and fuel consumption monitoring methodology for HDVs will be based on a combination of component testing and vehicle simulation. In this context, one of the key input parameters that need to be accurately defined for achieving a representative and accurate fuel consumption simulation is the vehicle's aerodynamic drag. A highly repeatable, accurate and sensitive measurement methodology was needed, in order to capture small differences in the aerodynamic characteristics of different vehicle bodies. A measurement methodology is proposed which is based on constant speed measurements on a test track, the use of torque measurement systems and wind speed measurement. In order to support the development and evaluation of the proposed approach, a series of experiments were conducted on 2 different trucks, a Daimler 40 ton truck with a semi-trailer and a DAF 18 ton rigid truck. Two different torque measurement systems (wheel rim torque sensors and half shaft torque sensors) were used for the measurements and two different vehicle tracking approaches were investigated (high precision GPS and opto-electronic barriers).
Technical Paper
2014-04-01
Kelly Daly Flynn, Ionut C. Harta, J. David Schall
Tribological performance of tungsten sulfide (WS2) nanoparticles, microparticles and mixtures of the two were investigated. Previous research showed that friction and wear reduction can be achieved with nanoparticles. Often these improvements were mutually exclusive, or achieved under special conditions (high temperature, high vacuum) or with hard-to-synthesize inorganic-fullerene WS2 nanoparticles. This study aimed at investigating the friction and wear reduction of WS2 of nanoparticles and microparticles that can be synthesized in bulk and/or purchased off the shelf. Mixtures of WS2 nanoparticles and microparticles were also tested to see if a combination of reduced friction and wear would be achieved. The effect of the mixing process on the morphology of the particles was also reported. The microparticles showed the largest reduction in coefficient of friction while the nanoparticles showed the largest wear scar area reduction. Mixtures of nanoparticles and microparticles did not provide the desired combination of significant friction and wear reductions.
Technical Paper
2014-04-01
Narankhuu Jamsran, Ocktaeck Lim, Norimasa Iida
This study has been computationally investigated how the DME autoignition reactivity is affected by EGR and intake-pressure boost over various engine speed. CHEMKIN-PRO was used as a solver and chemical-kinetics mechanism for DME was utilized from Curran's model. We examined first the influence of EGR addition on autoignition reactivity using contribution matrix. Investigations concentrate on the HCCI combustion of DME at wide ranges of engine speeds and intake-pressure boost with EGR rates and their effects on variations of autoignition timings, combustion durations in two-stage combustion process in-detail including reaction rates of dominant reactions involved in autoignition process. The results show that EGR addition increases the combustion duration by lowering reaction rates. It was also found that autoignition timings were very sensitive to boost pressure due to boost pressure enhances the reactivity of intermediate species but combustion durations dominantly depend on the EGR addition.
Technical Paper
2014-04-01
Jing Gong, Jian Cai, Chenglong Tang
Propanol isomers are oxygenated fuels and have higher octane number and energy density compared to methanol and ethanol. In recent years, with the development of fermentation method, propanol isomers have gained more attention as engine additive to reduce the emission and the consumption of traditional fossil fuels. In this study, Hydrocarbon (HC), carbon monoxide (CO) and particulate matter (PM) emission characteristic of propanol isomers/gasoline blends were comparatively investigated at different blending ratios (0, 10, 20, 40 and 100) combined with exhaust gas recirculation (EGR) in a spark-ignition engine. The number distribution of particulate matter emission is mainly studied in addition to the particulate matter mass distribution. Results show that pure propanol isomers yield significantly different emission characteristics compared to the other blends. With the increase of blending ratio, CO emission shows a decreased trend while unidentified HC emissions are observed except pure propanol isomers.
Technical Paper
2014-04-01
Xiangyu Feng, Yunshan Ge, Jianwei Tan, Jiaqiang Li, Yao Zhang, Chenglei Yu
Abstract The NOx conversion efficiency of vanadium-based SCR catalyst is lower under low temperature. Utilizing an exhaust analyzer, the effects of electrically heated catalyst on the performance of vanadium-based SCR catalyst under low temperature was studied on the engine test bench. The inlet temperature of SCR catalyst without the electrically heated catalyst were in the range of 150°C∼270°C under various steady engine modes, and the NSR (Normalized Stoichiometric Ratio) was set as 0.4,0.6,0.8,1.0. The results showed that under the space velocity of 20000h−1, with the application of the electrically heated catalyst, the inlet temperature of SCR increased about 19.9°C on average and the NOx conversion efficiency improved about 8.0%. The NOx conversion efficiency increased 1.7%∼8.6% at the temperatures of 150°C∼174°C, and 1.0%∼15.9% at the temperatures of 186°C∼270°C. The experiment space velocity properties indicated that with the electrically heated catalyst, the inlet temperature increase and the increasing rate of the NOx conversion efficiency both decreased with the increasing space velocity.
Technical Paper
2014-04-01
Jason D. Pless, Mojghan Naseri, Wassim Klink, Glen Spreitzer, Sougato Chatterjee, Penelope Markatou
Selective Catalytic Reduction (SCR) catalysts have been demonstrated as an effective solution for controlling NOx emissions from diesel engines. There is a drive to reduce the overall packaging volume of the aftertreatment system for these applications. In addition, more active SCR catalysts will be needed as the applications become more challenging: e.g. lower temperatures and higher engine out NOx, for fuel consumption improvements. One approach to meet the challenges of reduced volume and/or higher NOx reduction is to increase the active site density of the SCR catalyst by coating higher amount of SCR catalyst on high porosity substrates (HPS). This approach could enable the reduction of the overall packaging volume while maintaining similar NOx conversion as compared to 2010/2013 systems, or improve the NOx reduction performance for equivalent volume and NH3 slip. In this work, systems consisting of SCR coated on high porosity substrates were evaluated in comparison to standard substrate based SCR systems used in typical 2010 applications.
Technical Paper
2014-04-01
Jean Balland, Michael Parmentier, Julien Schmitt
Similar to single-brick SCR architectures, the multi-brick SCR systems described in this paper require urea injection control software that meets the NOx conversion performance target while maintaining the tailpipe NH3 slip below a given threshold, under all driving conditions. The SCR architectures containing a close-coupled SCRoF and underfloor SCR are temperature-wise more favorable than the under-floor location and lead to significant improvement of the global NOx conversion, compared to a single-brick system. But in order to maximize the benefit of close-coupling, the urea injection control must maximize the NH3 stored in the SCRoF. The under-floor SCR catalyst can be used as an NH3 slip buffer, lowering the risk of NH3 slip at the tailpipe with some benefit on the global NOx conversion of the system. With this approach, the urea injection strategy has a limited control on the NH3 coverage of the under-floor SCR catalyst. To take more advantage of the under-floor SCR catalyst for improving the NOx conversion, the NH3 coverage of the under-floor SCR must be taken into account, and therefore a combined control of both catalysts is required.
Technical Paper
2014-04-01
Keld Johansen, Henrik Bentzer, Arkady Kustov, Kenneth Larsen, Ton V.W. Janssens, Rasmus G. Barfod
Abstract Today, the DPF and SCR catalysts are combined sequentially in diesel exhaust systems. However, such sequential system configuration has several drawbacks: 1) large volume; 2) insufficient temperature for the SCR catalyst during cold start when DPF is placed in front of SCR; and 3) unfavorable conditions for passive soot regeneration if SCR is placed upstream of the DPF. The problems can potentially be solved by integrating the SCR catalyst into the particulate filter as one multifunctional unit. The study indicates that SCRonDPF based on Cu-zeolite type as SCR material can achieve the NOx conversion levels close to flow-through SCR catalysts for LDV (Light Duty Vehicles) using forced regenerations. Forced soot regeneration solves potential sulfur poisoning. For HDV (Heavy Duty Vehicles) applications with full managed passive soot regenerations, integration of V-based SCR formulations on DPF represents an attractive solution due to high sulfur resistance accompanied by low-temperature fuel economy.
Technical Paper
2014-04-01
Matthieu Lecompte, Stephane Raux, Arnaud Frobert
Abstract The selective catalytic reduction (SCR) based on urea water solution (UWS) is an effective way to reduce nitrogen oxides (NOx) emitted by engines. The high potential offered by this solution makes it a promising way to meet the future stringent exhaust gas standards (Euro6 and Tier2 Bin5). UWS is injected into the exhaust upstream of an SCR catalyst. The catalyst works efficiently and durably if the spray is completely vaporized and thoroughly mixed with the exhaust gases before entering. Ensuring complete vaporization and optimum mixture distribution in the exhaust line is challenging, especially for compact exhaust lines. Numerous parameters affect the degree of mixing: urea injection pressure and spray angle, internal flow field (fluid dynamics), injector location …. In order to quantify the mixture quality (vaporization, homogeneity) upstream of the SCR catalyst, it is proposed to employ non intrusive optical diagnostics techniques such as laser induced fluorescence (LIF).
Technical Paper
2014-04-01
Hongsuk Kim, Cheon Yoon, Junho Lee, Hoyeol Lee
Abstract One of most effective NOx control technology of modern diesel engines is SCR with ammonia. Current NOx reduction systems are designed to use a solution of urea dissolved in water as a source of ammonia. However, the liquid urea systems have technical difficulties, such as a freezing point below −11°C and solid deposit formation in the exhaust temperature below 200°C. The objective of this study is to investigate the possibility of a new ammonia generation system that uses low-cost solid ammonium salt, such as solid urea and ammonium carbonate. The result shows that ammonium carbonate is more suitable than solid urea because of low decomposition temperature and no change to the other ammonium salt during the decomposition process. This paper also shows the NOx reduction capability of the new ammonia delivery system that uses ammonium carbonate.
Technical Paper
2014-04-01
Zakwan Skaf, Timur Aliyev, Leo Shead, Thomas Steffen
Abstract Selective Catalytic Reduction (SCR) is a leading aftertreatment technology for the removal of nitrogen oxide (NOx) from exhaust gases (DeNOx). It presents an interesting control challenge, especially at high conversion, because both reagents (NOx and ammonia) are toxic, and therefore an excess of either is highly undesirable. Numerous system layouts and control methods have been developed for SCR systems, driven by the need to meet future emission standards. This paper summarizes the current state-of-the-art control methods for the SCR aftertreatment systems, and provides a structured and comprehensive overview of the research on SCR control. The existing control techniques fall into three main categories: traditional SCR control methods, model-based SCR control methods, and advanced SCR control methods. For each category, the basic control technique is defined. Further techniques in the same category are then explained and appreciated for their relative advantages and disadvantages.
Technical Paper
2014-04-01
Thomas Wittka, Bastian Holderbaum, Teuvo Maunula, Michael Weissner
The regulations for mobile applications will become stricter in Euro 6 and further emission levels and require the use of active aftertreatment methods for NOX and particulate matter. SCR and LNT have been both used commercially for mobile NOX removal. An alternative system is based on the combination of these two technologies. Developments of catalysts and whole systems as well as final vehicle demonstrations are discussed in this study. The small and full-size catalyst development experiments resulted in PtRh/LNT with optimized noble metal loadings and Cu-SCR catalyst having a high durability and ammonia adsorption capacity. For this study, an aftertreatment system consisting of LNT plus exhaust bypass, passive SCR and engine independent reductant supply by on-board exhaust fuel reforming was developed and investigated. The concept definition considers NOX conversion, CO2 drawback and system complexity. The passive SCR significantly contributes to the total NOX conversion over a broad temperature range.
Technical Paper
2014-04-01
Nathan Ottinger, Brandon Foley, Yuanzhou Xi, Z. Gerald Liu
Ammonia oxidation (AMOX) catalysts are critical parts of most diesel aftertreatment systems around the world. These catalysts are positioned downstream of selective catalytic reduction (SCR) catalysts and remove unreacted NH3 that passes through the SCR catalyst. In many configurations, the AMOX catalyst is situated after a diesel oxidation catalyst and catalyzed diesel particulate filter that oxidize CO and hydrocarbons. However, in Euro V and proposed Tier 4 final aftertreatment architectures there is no upstream oxidation catalyst. In this study, the impact of hydrocarbons is evaluated on two different types of AMOX catalysts. One has dual washcoat layers-SCR washcoat on top of PGM washcoat-and the other has only a PGM washcoat layer. Results are presented for NH3 and hydrocarbon oxidation, NOx and N2O selectivity, and hydrocarbon storage. The AMOX findings are rationalized in terms of their impact on the individual oxidation and SCR functions. Finally, these new results are compared to recent hydrocarbon conversion measurements made on vanadium-based SCR catalysts in order to estimate the potential system-level reduction of hydrocarbons possible with a combined V-SCR+AMOX aftertreatment.
Technical Paper
2014-04-01
Jongik Jeon, Hyongman Seo, Kangwon Lee, Soonhyung Kwon, Kisong Bae
Abstract This paper describes how to meet LEVII ULEV70 emission standards and minimize fuel consumption with the combined NOx after-treatment (LNT+SCR) system for diesel vehicles. Through analysis of LNT's functionality and characteristics in a LNT+SCR combined after-treatment system, allowed a new control strategy to be established, different from the existing LNT-only system. In the 200°C or higher condition where SCR can provide the most stable NOx conversion efficiency, rich regeneration of LNT was optimized to minimize LNT deterioration and fuel consumption. Optimized mapping between rapid heat up strategy and raw NOx reduction maximized LNT's NOx conversion efficiency during the intervals when it is not possible for SCR to purify NOx This study used bench aged catalysts which were equivalent to 150K full useful life. During the Highway (HFET) driving cycle when the SCR conversion rate is generally high, fuel economy was improved by minimization DeNOx in LNT and improvement of the engine combustion efficiency.
Technical Paper
2014-04-01
Joel Op de Beeck, Kevin Slusser, Neall Booth
Abstract Automotive SCR systems are dimensioned to reduce NOx efficiently in normal driving conditions. In markets such as North America and Europe, extreme winter conditions are common over a period of many weeks where temperatures are usually below DEF (Diesel Exhaust Fluid) freezing temperatures at −11°C (12°F). In previous studies and applications, DEF was heated in the tank in a dedicated pot or alternatively by a standardized central heater. Due to the local character of these heating solutions, it was not possible to thaw the full tank volume. The objective of this study is to demonstrate how to significantly improve performance of the SCR system in cold weather conditions for passenger car, light commercial vehicles and SUV applications. The performance improvement is demonstrated by sustainability testing showing how much of the full tank content can be thawed and made available for injection in the exhaust system. Based on maximum average dosing rates of 250 g/h, external temperatures down to −40°C and depending on the tank shape the heater is designed to optimize tank heating performance.
Technical Paper
2014-04-01
Nic van Vuuren
Abstract The implementation of stringent nitrogen oxides (NOx) emissions reduction legislation in Europe and North America is driving the introduction of new exhaust aftertreatment systems, including those that treat NOx under the high-oxygen conditions typical of lean-burn engines. One increasingly common solution, referred to as Selective Catalytic Reduction (SCR), comprises a catalyst that facilitates the reactions of ammonia (NH3) with the exhaust nitrogen oxides (NOx) to produce nitrogen (N2) and water (H2O). It is customary with these systems to use a liquid aqueous urea solution, typically at a 32% concentration of urea (CO(NH2)2). The solution is referred to as AUS-32, and is also known under its commercial name of AdBlue® in Europe, and DEF - Diesel Exhaust Fluid - in the USA. The urea solution is injected into the exhaust and transformed to NH3 by various mechanisms for the SCR reactions. Urea injection systems using AUS-32 are now in production and becoming a widespread mature technology on many on-road automotive and off-road vehicle applications.
Technical Paper
2014-04-01
Guanyu Zheng, Fengshuang Wang, Suying Zhang, Jianhua Zhang, Jianzhong Tao, Zhiguo Zhao, Jianqing Fan
Abstract In order to satisfy China IV (equivalent to EU IV) emission regulations, an unconventional design concept was proposed with injector closely coupled with SCR can body. The benefit of this design is that the urea decomposition pipe was removed or drastically shortened, resulting in much smaller packaging space and lower cost of the whole system. However, the resulting short urea mixing distance generates concerns on low urea mixing efficiency and risks of urea deposits. In particular, airless urea injectors tend to generate incomplete evaporation of urea water solution, resulting in high risks of urea deposits. New aftertreatment mixing structures need to be developed to resolve these technical challenges. To this end, stepwise and systematic enhancements of the design have been employed, resulting in multiple designs to eventually meet a set of performance targets, including emission reduction efficiency, reagent mixing, urea evaporation, ammonia and velocity distribution, back pressure, and urea deposits.
Technical Paper
2014-04-01
Shun Hong Long, Lianhua Tang, Guodong Yan, Ben Niu, Guanyu Zheng, Fengshuang Wang, Suying Zhang, Jianhua Zhang, Jianzhong Tao
Abstract To satisfy China IV emissions regulations, diesel truck manufacturers are striving to meet increasingly stringent Oxides of Nitrogen (NOx) reduction standards. Heavy duty truck manufacturers demand compact urea SCR NOx abatement designs, which integrate injectors, NOx sensors and necessary components on SCR can in order to save packaging space and system cost. To achieve this goal, aftertreatment systems need to be engineered to achieve high conversion efficiencies, low back pressure, no urea deposit risks and good mechanical durability. Initially, a baseline Euro IV Urea SCR system is evaluated because of concerns on severe deposit formation. Systematic enhancements of the design have been performed to enable it to meet multiple performance targets, including emission reduction efficiency and low urea deposit risks via improved reagent mixing, evaporation, and distribution. Acoustic performance has been improved from the baseline system as well. The optimized system improved ammonia uniformity, eliminated urea deposits, improved NOx conversion efficiency while satisfying existing EU III installation packing space.
Technical Paper
2014-04-01
Mai Huong Tran, Yoshinori Yamashita, Norihiko Aono
Abstract Recently, there has been increasing interest in catalysts with smaller volume for a Urea Selective Catalytic Reduction (SCR) system especially for use in heavy duty vehicles. In this study, several new concepts were developed in order to improve the deNOx performance of the SCR catalysts over a wide range of operating temperatures and this resulted in a compact SCR system. First, the urea decomposition process in diesel exhaust gas was elucidated. Several kinds of urea decomposition catalysts were investigated and the material which showed the best performance in NH3 (ammonia) formation was used to improve the low temperature performance of Cu-zeolite catalysts. Second, the method of reducing the amount of NH3 slip was investigated. It is well known that the amount of ammonia slip after the Urea-SCR system must be under 10 ppm and therefore materials with lower NH3 slip are preferred. The smaller the amount of NH3 slip, the larger the amount of urea that can be injected into the system and this leads to higher NOx conversion.
Technical Paper
2014-04-01
Henrik Smith, Thomas Lauer, Mattias Mayer, Steven Pierson
Long-term reliability is one of the major requirements for the operation of automotive exhaust aftertreatment systems based on selective catalytic reduction (SCR). For an efficient reduction of nitrogen oxides in the SCR catalyst it is desirable that the thermolysis of the injected urea water solution (UWS) is completed within the mixing section of the exhaust system. Urea might undergo a number of secondary reactions leading to the formation of solid deposits on system walls. A deeper understanding of the mechanisms and influence factors is a basic requirement to prevent and predict undesired decomposition products. This paper outlines the mechanisms of UWS transport and deposition on a typical mixing element geometry. The conditions leading to deposit formation were investigated based on optical and temperature measurements in a box with optical access. A good correlation with the deposit location observed at the close-to-series exhaust system was found. A chemical analysis complemented the investigations.
Technical Paper
2014-04-01
Lennert Sterken, Lennart Lofdahl, Simone Sebben, Tim Walker
Abstract Under a global impulse for less man-made emissions, the automotive manufacturers search for innovative methods to reduce the fuel consumption and hence the CO2-emissions. Aerodynamics has great potential to aid the emission reduction since aerodynamic drag is an important parameter in the overall driving resistance force. As vehicles are considered bluff bodies, the main drag source is pressure drag, caused by the difference between front and rear pressure. Therefore increasing the base pressure is a key parameter to reduce the aerodynamic drag. From previous research on small-scale and full-scale vehicles, rear-end extensions are known to have a positive effect on the base pressure, enhancing pressure recovery and reducing the wake area. This paper investigates the effect of several parameters of these extensions on the forces, on the surface pressures of an SUV in the Volvo Cars Aerodynamic Wind Tunnel and compares them with numerical results. To decrease the dependency of other effects within the engine bay and underbody, the SUV has been investigated in a closed-cooling configuration with upper and lower grille closed and with a smoothened underbody.
Technical Paper
2014-04-01
Wanyu Sun, Shufen Wang, Shanheng Yan, Lei Guo, Yuanjing Hou
Abstract Selective catalytic reduction (SCR) has become one of the primary technologies to reduce internal combustion engine (ICE) emission. The installation angle of urea injector plays an important role during the SCR process. The urea injector is often vertically mounted to the exhaust pipe for on road heavy duty truck because of its good performance and general packaging convenience, and this type of installation has been the focus of previous research. However, due to certain packaging constraints or responsiveness considerations, the injector is installed with an inclined acute angle to the exhaust pipe under some circumstance. To evaluate the underlying benefits and risks of this type of installation angle, a computational fluid dynamic (CFD) model based on the Renolds averaged Navier-Stokes (RANS) solver from AVL Fire is used to simulate the injection process of urea for an acute-angled 3-hole injector, through which, the urea spray's formation and motion, wallfilm accumulation and NH3 distribution uniformity characteristics are studied.
Technical Paper
2014-04-01
Stephan Stadlbauer, Harald Waschl, Luigi del Re
Abstract The emissions of modern Diesel engines, which are known to have various health effects, are beside the drivers torque demands and low fuel consumptions one of the most challenging issues for combustion and after treatment control. To comply with legal requirements, emission control for heavy duty engines is not feasible without additional hardware, usually consisting of a Diesel oxidation catalyst (DOC), a Diesel particulate filter (DPF) and a selective catalytic reduction (SCR) system. In contrast to other NOx reduction systems, e.g. lean NOx traps, the SCR system requires an additional ingredient, namely ammonia (NH3), to reduce the NOx emissions to non harmful components. Consequently, the correct amount of NH3 dosing in the SCR catalyst is one of the critical components to reach high conversion rates and avoid ammonia slip. Against this background and in contrast to existing proposals in which the NH3 dosing is often calculated based on a NOx emission sensor, this work presents a strategy to adopt the set point estimation of the NH3 dosing, based on a virtual NOx sensor extended by a virtual DOC model.
Technical Paper
2014-04-01
Zhiming Gao, Tim J. LaClair, C. Stuart Daw, David E. Smith, Oscar Franzese
We present simulated fuel economy and emissions of city transit buses powered by conventional diesel engines and diesel-hybrid electric powertrains of varying size. Six representative city drive cycles were included in the study. In addition, we included previously published aftertreatment device models for control of CO, HC, NOx, and particulate matter (PM) emissions. Our results reveal that bus hybridization can significantly enhance fuel economy by reducing engine idling time, reducing demands for accessory loads, exploiting regenerative braking, and shifting engine operation to speeds and loads with higher fuel efficiency. Increased hybridization also tends to monotonically reduce engine-out emissions, but tailpipe (post-aftertreatment) emissions are affected by complex interactions between engine load and the transient catalyst temperatures, and the emissions results were found to depend significantly on motor size and details of each drive cycle.
Technical Paper
2014-04-01
John Hoard, Nandagopalan Venkataramanan, Barbara Marshik, William Murphy
Abstract Ammonia, often present in exhaust gas samples, is a polar molecule gas that interacts with walls of the gas sampling and analysis equipment resulting in delayed instrument response. A set of experiments quantified various materials and process parameters of a heated sample line system for ammonia (NH3) response using a Fourier Transform infrared spectrometer (FTIR). Response attenuation rates are due to mixing and diffusion during transport as well as NH3 wall storage. Mixing/diffusion effects cause attenuation with a time constant 1-10 seconds. Wall storage attenuation has a time constant 10-200 seconds. The effects of sample line diameter and length, line temperature, line material, hydrated versus dry gas, and flow rate were examined. All of these factors are statistically significant to variation of at least one of the time constants. The NH3 storage on the sample system walls was calculated as a function of the experimental test as well. In this case, line length and diameter were not statistically significant, but line temperature, flow rate, and material were.
Technical Paper
2014-04-01
Susanna Paz, Rosa Delgado, David Riba
Abstract Currently, regulations on vehicle evaporative emissions only focus on the sum of Total Hydrocarbons (THC) without taking into account either the detailed hydrocarbon composition nor other chemicals besides hydrocarbons emitted from gasoline evaporation. As a consequence, this composition, also known as speciation, is not always noted and is even more unknown when biofuels such as ethanol are introduced in the market. Furthermore, these regulations do not differentiate the source of these emissions in the vehicle. The programme described in this paper is designed to investigate the influence of the addition of ethanol to gasoline on evaporative emissions. It has tried to go one step ahead of these directives obtaining more detailed characterization of these evaporative emissions. The programme has enabled a list of compounds (methanol, ethanol, aldehydes, ketones and hydrocarbons) to be determined in evaporative emissions among different ethanol-gasoline fuels (E0, E5-S, E10 and E85), applied to Euro 4 and Flexifuel vehicles by three chromatographic methods based on California Air Resources Board (CARB).
Technical Paper
2014-04-01
Robert Anthony Giannelli, Ryan Stubleski, Anthony Saunders
Automobile time-resolved emissions of CO, CO2, HC, and NOx during engine and catalyst warm-up have been analyzed by fitting the emissions to the product of vehicle tractive power and a series of gaussian functions whose relative magnitudes were allowed to vary in time. From this analysis the emissions were discerned into four components : (1.) the emissions due to vehicle power demand, (2.) key-on emissions, (3.) a catalyst warm-up emissions function, and (4.) a fast idle emissions function. Both the emissions associated with the engine and the catalyst warm-up decline exponentially with time. Two additional characteristics (a.) emissions occurring during idling and (b.) emissions due to catalyst cooling during idle were observed, but not quantified. Also, a semi-empirical formula to approximate cold start emissions for light duty cars which includes the vehicle tractive power, time constants which define the emissions decrease in time, and the power demand characteristics has been developed.
Technical Paper
2014-04-01
Essam F. Abo-Serie, Mohamed Sherif, Dario Pompei, Adrian Gaylard
Abstract A potentially important, but inadequately studied, source of passengers' exposure to pollutants when a road vehicle is stationary, with an idling engine, results from the ingestion of a vehicle's own exhaust into the passenger compartment through the HVAC intake. We developed and applied a method to determine the fraction of a vehicle's exhaust entering the cabin by this route. Further the influence of three parameters: ambient tail-wind speed, vehicle ground clearance and tail pipe angle, is assessed. The study applies Computational Fluid Dynamic (CFD) simulation to the distribution of exhaust gasses around a vehicle motorized with a 2.2 liter Diesel engine. The simulation employs efficient meshing techniques and realistic loading conditions to develop a general knowledge of the distribution of the gasses in order to inform engineering design. The results show that increasing tail-wind velocity, tail-pipe angle and ground clearance reduces the presence of CO and NO at the HVAC intake.
Viewing 1 to 30 of 20042