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Technical Paper
2014-04-01
Xiao Ma, Yunliang Qi, Zhi Wang, Hongming Xu, Jian-Xin Wang
Abstract Using EGR instead of throttle to control the load of a stoichiometric dual-fuel dieseline (diesel and gasoline) compression ignition (SDCI) engine with three-way catalyst (TWC) aftertreatment is considered a promising technology to address the challenges of fuel consumption and emissions in future internal combustion engines. High-speed imaging is used to record the flame signal in a single-cylinder optical engine with a PFI+DI dual injection system. The premixed blue flame is identified and separated using green and blue channels in RGB images. The effects of injection timing on SDCI combustion are studied. An earlier injection strategy is found to be ideal for soot reduction; however, the ignition-injection decoupling problem results in difficulties in combustion control. It is also found that a split injection strategy has advantages in soot reduction and thermal efficiency. Only 10% of the total diesel fuel for the main injection can advance the combustion phase significantly and the combustion duration can be reduced by approximate 50%.
Technical Paper
2014-04-01
Mufaddel Dahodwala, Satyum Joshi, Erik W. Koehler, Michael Franke
Abstract The advantages of applying Compressed Natural Gas (CNG) as a fuel for internal combustion engines are well known. In addition to a significant operating cost savings due to a lower fuel price relative to diesel, there is an opportunity to reduce the engine's emissions. With CNG combustion, some emissions, such as Particulate Matter (PM) and Carbon Dioxide (CO2), are inherently reduced relative to diesel fueled engines due to the nature of the combustion and the molecular makeup of the fuel. However, it is important to consider the impact on all emissions, including Total Hydrocarbons (THC) and Carbon Monoxide (CO), which can increase with the use of CNG. Nitrogen Oxides (NOx) emission is often reported to decrease with the use of CNG, but the ability to realize this benefit is significantly impacted by the control strategy and calibration applied. FEV has investigated the emissions and performance impact of operating a heavy-duty diesel engine with CNG in a dual fuel mode. The CNG was introduced via injectors mounted to an inlet pipe located upstream of the intake manifold.
Technical Paper
2014-04-01
Nassim Khaled, Michael Cunningham, Jaroslav Pekar, Adrian Fuxman, Ondrej Santin
Abstract In this paper we consider the issues facing the design of a practical multivariable controller for a diesel engine with dual exhaust gas recirculation (EGR) loops. This engine architecture requires the control of two EGR valves (high pressure and low pressure), an exhaust throttle (ET) and a variable geometry turbocharger (VGT). A systematic approach suitable for production-intent air handling control using Model Predictive Control (MPC) for diesel engines is proposed. Furthermore, the tuning process of the proposed design is outlined. Experimental results for the performance of the proposed design are implemented on a 2.8L light duty diesel engine. Transient data over an LA-4 cycle for the closed loop performance of the controller are included to prove the effectiveness of the proposed design process. The MPC implementation process took a total of 10 days from the start of the data collection to build a calibrated engine model all the way through the calibration of the controller over the transient drive cycle.
Technical Paper
2014-04-01
Ivan Arsie, Andrea Cricchio, Cesare Pianese, Matteo De Cesare, Walter Nesci
Abstract In the last years the automotive industry has been involved in the development and implementation of CO2 reducing concepts such as the engines downsizing, stop/start systems as well as more costly full hybrid solutions and, more recently, waste heat recovery technologies. These latter include ThermoElectric Generator (TEG), Rankine cycle and Electric Turbo Compound (ETC) that have been practically implemented on few heavy-duty application but have not been proved yet as effective and affordable solutions for the automotive industry. The paper deals with the analysis of opportunities and challenges of the Electric Turbo Compound for automotive light-duty engines. In the ETC concept the turbine-compressor shaft is connected to an electric machine, which can work either as generator or motor. In the former case the power can satisfy the vehicle electrical demand to drive the auxiliaries or stored in the batteries. In the latter case the electric motor can assist the turbine and speed up the compressor when requested.
Technical Paper
2014-04-01
Takahiro Umeno, Masaya Hanzawa, Yoshiyuki Hayashi, Masao Hori
Abstract In this study several NOx storage materials have been investigated to see their NOx storage properties. And sulfur release properties of these materials have been also investigated. Based on these findings, new LNT catalyst was developed. In this new LNT catalyst Barium is supported on one basic material, and Strontium is coated in the whole catalyst with high dispersion. And it shows higher NOx storage performance against conventional LNT one even though 10g/L of sulfur was introduced to the catalysts. According to analysis results of new LNT catalyst after sulfur poisoning, it was found that sulfur was mainly adsorbed on Strontium selectively, and then it formed sulfate compound as SrSO4. On the other hand, another sulfate compounds could be hardly observed. And regarding Barium on basic material some analysis measurement said that it has not only better NOx storage function, but also better sulfur release function. The assumption why new LNT catalyst has high sulfur resistance is that Strontium works like scavenger effect against sulfur, therefore it enables to keep higher NOx storage performance by Barium even if it contains much sulfur amount in the catalyst.
Technical Paper
2014-04-01
Alok Warey, Anil Singh Bika, Alberto Vassallo, Sandro Balestrino, Patrick Szymkowicz
Cooled exhaust gas recirculation (EGR) is widely used in diesel engines to control engine out NOx (oxides of nitrogen) emissions. A portion of the exhaust gases is re-circulated into the intake manifold of the engine after cooling it through a heat exchanger known as an EGR cooler. EGR cooler heat exchangers, however, tend to lose efficiency and have increased pressure drop as deposit forms on the heat exchanger surface due to transport of soot particles and condensing species to the cooler walls. In our previous work surface condensation of water vapor was shown to be successful in removing a significant portion of the accumulated deposit mass from various types of deposit layers typically encountered in EGR coolers. Significant removal of accumulated deposit mass was observed for “dry” soot only deposit layers, while little to no removal was observed for the deposit layers created at low coolant temperatures that consisted of both soot and condensed hydrocarbons (HC). The focus of this study was to explore the potential benefits of combining a pre-EGR cooler oxidation catalyst (OC) in the high pressure EGR loop with exposure to water vapor condensation.
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
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
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
Theodoros G. Vlachos, Pierre Bonnel, Adolfo Perujo, Martin Weiss, Pablo Mendoza Villafuerte, Francesco Riccobono
In-use testing with Portable Emissions Measurement Systems (PEMS) has received attention by policy makers and industry as an effective and cost-efficient means to verify emissions of a wide range of vehicles. We provide an overview of the state-of-the-art PEMS in-use emissions testing in the current and future European emissions legislation for light-duty and heavy-duty vehicles as well as non-road mobile machinery. For obtaining type approval in European Union (EU), light-duty vehicles have to comply with Euro 6 emission standards from January 2014 onward. In parallel, a new test procedure will complement standard emissions testing in the laboratory to control gaseous and particulate emissions over a wide range of real-world driving conditions. Two candidate procedures are developed at present, i.e., random cycle testing and on-road emissions testing with PEMS. Currently, key challenges are the definition of test conditions and design of a suitable method for data evaluation. For heavy-duty vehicles, in-use testing with PEMS is already enforced in the European Union since 2009.
Technical Paper
2014-04-01
Stefan Schmidt, Maurice Smeets, Roland Boehner, Robert Aas, Christian Winkler, Markus Schoenen, Peter Hermann, Julian Tan, Magdi Khair, Joern Bullert
Tighter emission limits are discussed and established around the world to improve quality of the air we breathe. In order to control global warming, authorities ask for lower CO2 emissions from combustion engines. Lots of efforts are done to reduce engine out emissions and/or reduce remaining by suitable after treatment systems. Watlow, among others, a manufacturer of high accurate, active temperature sensor ExactSense™, wanted to understand if temperature sensor accuracy can have an influence on fuel consumption (FC). For this purpose a numerical approach was chosen where several non-road driving cycles (NRTCs) were simulated with the data base of a typical Stage IV heavy duty diesel engine. The engine is equipped with an exhaust gas after treatment system consisting of a DOC, CDPF and an SCR. In this work scope, the investigations shall be restricted to the FC benefits obtained in the active and passive DPF regeneration. The numerical investigations were performed using DPF soot loading and oxidation models using a commercially available software program.
Technical Paper
2014-04-01
Usman Asad, Jimi Tjong
Abstract Modern diesel engines employ a multitude of strategies for oxides of nitrogen (NOx) emission abatement, with exhaust gas recirculation (EGR) being one of the most effective technique. The need for a precise control on the intake charge dilution (as a result of EGR) is paramount since small fluctuations in the intake charge dilution at high EGR rates may cause larger than acceptable spikes in NOx/soot emissions or deterioration in the combustion efficiency, especially at low to mid-engine loads. The control problem becomes more pronounced during transient engine operation; currently the trend is to momentarily close the EGR valve during tip-in or tip-out events. Therefore, there is a need to understand the transient EGR behaviour and its impact on the intake charge development especially under unstable combustion regimes such as low temperature combustion. This study describes a zero-dimensional EGR model that enables the estimation of transient (cycle-by-cycle) build-up of EGR and the time (engine cycles) required to reach steady-state EGR operation (intake/exhaust concentrations).
Technical Paper
2014-04-01
René Wolf, Peter Eilts
When comparing automotive and large-bore diesel engines, the latter usually show lower specific fuel consumption values, while automotive engines are subject to much stricter emission standards. Within an FVV (Research Association for Combustion Engines) project these differences were identified, quantified and assigned to individual design and operation parameters. The approach was split in three different phases: 1 Comparison of different-sized diesel engines2 Correlation of differences in fuel consumption to design and operating parameters3 Further investigations under automotive boundary conditions The comparison in the first phase was made on the basis of operating data and energy balances as well as the separation of losses based on the thermodynamic analysis. To also determine the quantitative effects of each design and operating parameter, a 1D process calculation model of the passenger car engine was transformed gradually to a large-bore engine in the second phase. The advantage of the large-bore engines results basically from their higher combustion air ratio, shorter combustion duration, lower wall heat losses and high positive gas exchange work due to a high turbocharger efficiency.
Technical Paper
2014-04-01
Arnon Poran, Moris Artoul, Moshe Sheintuch, Leonid Tartakovsky
This paper describes a model for the simulation of the joint operation of internal combustion engine (ICE) with methanol reformer when the ICE is fed by the methanol steam reforming (SRM) products and the energy of the exhaust gases is utilized to sustain endothermic SRM reactions. This approach enables ICE feeding by a gaseous fuel with very favorable properties, thus leading to increase in the overall energy efficiency of the vehicle and emissions reduction. Previous modeling attempts were focused either on the performance of ICE fueled with SRM products or on the reforming process simulation and reactor design. It is clear that the engine performance is affected by the composition of the reforming products and the reforming products are affected by the exhaust gas temperature, composition and flow rate. Due to the tight interrelations between the two main parts of the considered ICE-reformer system, it is desirable to create a single model that simulates joint operation of the ICE and the SRM reactor.
Technical Paper
2014-04-01
Daniele Farrace, Michele Bolla, Yuri M. Wright, Konstantinos Boulouchos
This paper presents numerical simulations of in-cylinder soot evolution in the optically accessible heavy-duty diesel engine of Sandia Laboratories performed with the conditional moment closure (CMC) model employing a reduced n-heptane chemical mechanism coupled with a two-equation soot model. The influence of exhaust gas recirculation (EGR) on in-cylinder processes is studied considering different ambient oxygen volume fractions (8 - 21 percent), while maintaining intake pressure and temperature as well as the injection configuration unchanged. This corresponds to EGR rates between 0 and 65 percent. Simulation results are first compared with experimental data by means of apparent heat release rate (AHRR) and temporally resolved in-cylinder soot mass, where a quantitative comparison is presented. The model was found to fairly well reproduce ignition delays as well as AHRR traces along the EGR variation with a slight underestimation of the diffusion burn portion. Subsequently, the impact of EGR on the mixture formation, spray characteristics and soot evolution is investigated numerically and governing processes are identified and discussed.
Technical Paper
2014-04-01
Indranil Brahma, James Schmidt, Ryan Confair, Josh Kurtz, Ian Rafter, Peter Stryker, Daniel Johnson
Orifices, flow nozzles and arbitrarily shaped flow obstructing flow measurement devices are widely used to estimate EGR flow rates in engines, and also used to model flow restricting components like valves in engine analysis tools such as GT-Power. The standard assumptions about the flow discharge coefficient and its variation with Reynolds number are based on investigations of orifices across steady non-pulsating flows, widely reported in literature. In this work, the discharge coefficient for steady state pulsating flow as well as accelerating pulsating flow, commonly encountered during steady state and dynamic engine operation respectively, were investigated by installing an orifice on the exhaust side of a naturally aspirated diesel engine, while making reference flow measurements with a Laminar Flow Element on the intake side. ‘Snap Throttle’ tests were performed to accelerate the flow on the exhaust side with a sudden increase in exhaust gas temperature and accompanying decrease in density.
Technical Paper
2014-04-01
Xander Seykens, Frank Willems, Berry Kuijpers, Clint Rietjens
This paper presents an automated fit for a control-oriented physics-based diesel engine combustion model. This method is based on the combination of a dedicated measurement procedure and structured approach to fit the required combustion model parameters. Only a data set is required that is considered to be standard for engine testing. The potential of the automated fit tool is demonstrated for two different heavy-duty diesel engines. This demonstrates that the combustion model and model fit methodology is not engine specific. Comparison of model and experimental results shows accurate prediction of in-cylinder peak pressure, IMEP, CA10, and CA50 over a wide operating range. This makes the model suitable for closed-loop combustion control development. However, NO emission prediction has to be improved.
Technical Paper
2014-04-01
Christopher Chadwell, Terrence Alger, Jacob Zuehl, Raphael Gukelberger
Abstract Southwest Research Institute (SwRI) converted a 2012 Buick Regal GS to use an engine with Dedicated EGR™ (D-EGR™). D-EGR is an engine concept that uses fuel reforming and high levels of recirculated exhaust gas (EGR) to achieve very high levels of thermal efficiency [1]. To accomplish reformation of the gasoline in a cost-effective, energy efficient manner, a dedicated cylinder is used for both the production of EGR and reformate. By operating the engine in this manner, many of the sources of losses from traditional reforming technology are eliminated and the engine can take full advantage of the benefits of reformate. The engine in the vehicle was modified to add the following components: the dedicated EGR loop, an additional injector for delivering extra fuel for reformation, a modified boost system that included a supercharger, high energy dual coil offset (DCO) ignition and other actuators used to enable the control of D-EGR combustion. In addition, the compression ratio of the engine was increased to 11.7:1 to take advantage of the improved knock resistance from reformate and EGR.
Technical Paper
2014-04-01
Quan Liu, Alasdair Cairns, Hua Zhao, Mohammadreza Anbari Attar, Luke Cruff, Hugh Blaxill
Abstract The work was concerned with visualisation of the charge homogeneity and cyclic variations within the planar fuel field near the spark plug in an optical spark ignition engine fitted with an outwardly opening central direct fuel injector. Specifically, the project examined the effects of fuel type and injection settings, with the overall view to understanding some of the key mechanisms previously identified as leading to particulate formation in such engines. The three fuels studied included a baseline iso-octane, which was directly compared to two gasoline fuels containing 10% and 85% volume of ethanol respectively. The engine was a bespoke single cylinder with Bowditch style optical access through a flat piston crown. Charge stratification was studied over a wide spectrum of injection timings using the Planar Laser Induced Fluorescence (PLIF) technique, with additional variation in charge temperature due to injection also estimated when viable using a two-line PLIF approach. Overall, both gasoline-ethanol fuels generally exhibited a higher degree of stratification, albeit at least partly alleviated with elevated rail pressures.
Technical Paper
2014-04-01
Andrew Lewis, Sam Akehurst, James Turner, Rishin Patel, Andrew Popplewell
Increasingly stringent regulations and rising fuel costs require that automotive manufacturers reduce their fleet CO2 emissions. Gasoline engine downsizing is one such technology at the forefront of improvements in fuel economy. As engine downsizing becomes more aggressive, normal engine operating points are moving into higher load regions, typically requiring over-fuelling to maintain exhaust gas temperatures within component protection limits and retarded ignition timings in order to mitigate knock and pre-ignition events. These two mechanisms are counterproductive, since the retarded ignition timing delays combustion, in turn raising exhaust gas temperature. A key process being used to inhibit the occurrence of these knock and pre-ignition phenomena is cooled exhaust gas recirculation (EGR). Cooled EGR lowers temperatures during the combustion process, reducing the possibility of knock, and can thus reduce or eliminate the need for over-fuelling. It has also been shown to reduce exhaust gas temperature and improve combustion efficiency through improved combustion phasing.
Technical Paper
2014-04-01
Brian C. Kaul, Charles E.A. Finney, Robert M. Wagner, Michelle L. Edwards
Abstract Operation of spark-ignition (SI) engines with high levels of charge dilution through exhaust gas recirculation (EGR) achieves significant efficiency gains while maintaining stoichiometric operation for compatibility with three-way catalysts. Dilution levels, however, are limited by cyclic variability-including significant numbers of misfires-that becomes significant with increasing dilution. This variability has been shown to have both stochastic and deterministic components. Stochastic effects include turbulence, mixing variations, and the like, while the deterministic effect is primarily due to the nonlinear dependence of flame propagation rates and ignition characteristics on the charge composition, which is influenced by the composition of residual gases from prior cycles. The dynamics of operation with an external EGR loop differ substantially from those of dilute operation without external recirculation, both in time-scale and cylinder-synchronization effects, especially when misfires are encountered.
Technical Paper
2014-04-01
D. Ryan Williams, Chad Koci, Scott Fiveland
Driven by the desire to implement low-cost, high-efficiency NOx aftertreatment systems, such as Three Way Catalysts (TWC) or Lean NOx Traps (LNT), a novel 6-Stroke engine cycle was explored to determine the feasibility of implementing such a cycle on a compression ignition engine while continuing to deliver fuel efficiency. Fundamental questions regarding the abilities and trade-offs of a 6-stroke engine cycle were investigated for near-stoichiometric and lean operation. Experiments were performed on a single-cylinder 15-liter (equivalent) research engine equipped with flexible valvetrain and fuel injection systems to allow direct comparison between 4-stroke and 6-stroke performance across multiple hardware configurations. 1-D engine simulations with predictive combustion models were used to support, iterate on, and explore the 6-stroke operation in conjunction with the experiments. Output from the experiments and simulations were then used to perform Availability and Energy balances for a thermodynamic comparison of the two cycles.
Technical Paper
2014-04-01
Jacqueline O'Connor, Mark Musculus
Post injections have been shown to reduce engine-out soot emissions in a variety of engine architectures and at a range of operating points. In this study, measurements of the engine-out soot from a heavy-duty optical diesel engine have conclusively shown that interaction between the post-injection jet and soot from the main injection must be, at least in part, responsible for the reduction in engine-out soot. Extensive measurements of the spatial and temporal evolution of soot using high-speed imaging of soot natural luminosity (soot-NL) and planar-laser induced incandescence of soot (soot-PLII) at four vertical elevations in the piston bowl at a range of crank angle timings provide definitive optical evidence of these interactions. The soot-PLII images provide some of the most conclusive evidence to date that the addition of a post injection dramatically changes the topology and quantity of in-cylinder soot. As the post jet penetrates toward the bowl wall, it carves out regions from the main-injection soot structures, either through displacement of the soot or through rapid and progressive oxidation of the soot.
Technical Paper
2014-04-01
Glenn Lucachick, Aaron Avenido, David Kittelson, William Northrop
Diesel low temperature combustion (LTC) is an operational strategy that is effective at reducing soot and oxides of Nitrogen (NOx) emissions at low engine loads in-cylinder. A downside to LTC in diesel engines is increased hydrocarbon (HC) emissions. This study shows that semi-volatile species from LTC form the bulk of particulate matter (PM) upon dilution in the atmosphere. The nature of gas-to-particle conversion from high HC operating modes like LTC has not been well characterized. In this work, we explore engine-out PM and HC emissions from LTC and conventional diffusion combustion (CC) operation for two different engine load and speed modes using a modern light-duty diesel engine. An experimental method to investigate PM volatility was implemented. Raw exhaust was diluted under two dilution conditions. A tandem differential mobility analyzer (TDMA) was used to identify differences in volatility between particle sizes. The study revealed that LTC PM mass and number concentration showed a greater dependence on dilution conditions than PM from CC.
Technical Paper
2014-04-01
Yizhou Zhang, Jaal Ghandhi, David Rothamer
Abstract Comparison of particulate size distribution measurements from different combustion strategies was conducted with a four-stroke single-cylinder diesel engine. Measurements were performed at four different load-speed points with matched combustion phasing. Particle size distributions were measured using a scanning mobility particle sizer (SMPS). To study the influence of volatile particles, measurements were performed with and without a volatile particle remover (thermodenuder) at low and high dilution ratios. The use of a single testing platform enables quantitative comparison between combustion strategies since background sources of particulate are held constant. A large number of volatile particles were present under low dilution ratio sample conditions for most of the operating conditions. To avoid the impact of volatile particles, comparisons were made based on the high dilution ratio measurements with the thermodenuder. As anticipated, CDC had the highest particle number emissions for all operating conditions for particle sizes greater than the 23 nm PMP cutoff.
Technical Paper
2014-04-01
Nicolas Dronniou, Julian Kashdan, Bertrand Lecointe, Kyle Sauve, Dominique Soleri
Abstract Dual-fuel combustion strategies combining a premixed charge of natural gas and a pilot injection of diesel fuel offer the potential to reduce CO2 emissions as a result of the high Hydrogen/Carbon (H/C) ratio of methane gas. Moreover, the high octane number of methane means that dual-fuel combustion strategies can be employed on compression ignition engines without the need to vary the engine compression ratio, thereby significantly reducing the cost of engine hardware modifications. The aim of this investigation is to explore the fundamental combustion phenomena occurring when methane is ignited with a pilot injection of diesel fuel. Experiments were performed on a single-cylinder optical research engine which is typical of modern, light-duty diesel engines. A high-speed digital camera recorded time-resolved combustion luminosity and an intensified CCD camera was used for single-cycle OH*chemiluminescence imaging. Experiments were performed for a wide range of equivalence ratios of the premixed charge.
Technical Paper
2014-04-01
Peter Fussey, David Limebeer
Setting up engines to meet emissions limits often involves extensive steady-state calibration activities combined with ad-hoc strategies to compensate for transient operation. As engines become more complex and acceptable emissions levels ever lower, this task is becoming increasingly time consuming and expensive. The inclusion of models in the engine control units offers a way to reduce some of this calibration effort. Model-based control is an active area of research with advanced approaches now being proposed. One example is the use of real-time models to regulate the burn angle during transient manœuvres. This paper describes the application of a control-orientated combustion model to control directly emissions during transients. The model is used to optimize and constrain the NOx emissions directly, rather than controlling an inferred variable such as the burn angle. This has the benefit that calibration engineers will be able to set the emissions trade-off directly.
Technical Paper
2014-04-01
Justin E. Ketterer, Wai K. Cheng
Abstract Particulate emissions from a production gasoline direct injection spark ignition engine were studied under a typical cold-fast-idle condition (1200 rpm, 2 bar NIMEP). The particle number (PN) density in the 22 to 365 nm range was measured as a function of the injection timing with single pulse injection and with split injection. Very low PN emissions were observed when injection took place in the mid intake stroke because of the fast fuel evaporation and mixing processes which were facilitated by the high turbulent kinetic energy created by the intake charge motion. Under these conditions, substantial liquid fuel film formation on the combustion chamber surfaces was avoided. PN emissions increased when injection took place in the compression stroke, and increased substantially when the fuel spray hit the piston. A conceptual model was established for the particulate matter (PM) formation process in which PM is formed by pyrolysis after the normal premixed flame passage in fuel rich plumes originating from liquid films on the cylinder walls.
Technical Paper
2014-04-01
Xi Luo, Xin Yu, Kan Zha, Marcis Jansons, Valentin Soloiu
Emissions of Unburned Hydrocarbons (UHC) from diesel engines are a particular concern during the starting process, when after-treatment devices are typically below optimal operating temperatures. Drivability in the subsequent warm-up phase is also impaired by large cyclic fluctuations in mean effective pressure (MEP). This paper discusses in-cylinder wall temperature influence on unburned hydrocarbon emissions and combustion stability during the starting and warm-up process in an optical engine. A laser-induced phosphorescence technique is used for quantitative measurements of in-cylinder wall temperatures just prior to start of injection (SOI), which are correlated to engine out UHC emission mole fractions and combustion phasing during starting sequences over a range of charge densities, at a fixed fueling rate. Squish zone cylinder wall temperature shows significant influence on engine out UHC emissions during the warm-up process. Higher surface temperatures correlate with lower levels of engine-out UHC.
Technical Paper
2014-04-01
David Heuwetter, William Glewen, David Foster, Roger Krieger, Michael Andrie
The transient response of an engine with both High Pressure (HP) and Low Pressure (LP) EGR loops was compared by conducting step changes in EGR fraction at a constant engine speed and load. The HP EGR loop performance was shown to be closely linked to turbocharger performance, whereas the LP EGR loop was relatively independent of turbocharger performance and vice versa. The same experiment was repeated with the variable geometry turbine vanes completely open to reduce turbocharger action and achieve similar EGR rate changes with the HP and LP EGR loops. Under these conditions, the increased loop volume of the LP EGR loop prolonged the response of intake O2 concentration following the change in air-fuel ratio. The prolonged change of intake O2 concentration caused emissions to require more time to reach steady state as well. Strong coupling between the HP EGR loop and turbochargers was again observed using a hybrid EGR strategy. The potential benefit of the HP EGR loop's smaller volume and shorter residence time was largely negated by the simultaneous use of the larger LP EGR loop.
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