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Knock and Pre-Ignition Limits on Utilization of Ethanol in Octane-on-Demand Concept

King Abdullah Univ. of Science & Tech.-Eshan Singh, Robert Dibble
Saudi Aramco-Kai Morganti
Published 2019-09-09 by SAE International in United States
Octane-on-Demand (OoD) is a promising technology for reducing greenhouse emissions from automobiles. The concept utilizes a low-octane fuel for low and mid load operating conditions, and a high-octane additive is added at high load operating conditions. Researchers have focused on the minimum ethanol content required for operating at high load conditions when the low-octane fuel becomes knock limited. However, it is also widely known that ethanol has a high tendency to pre-ignite, which has been linked with its high laminar flame speed and surface ignition tendency. Moreover, ethanol has a lower stoichiometric air-fuel ratio, requiring a larger injected fuel mass per cycle. A larger fuel mass increases the potential for oil dilution by the liquid fuel, creating precursors for pre-ignition. Hence, the limits on ethanol addition owing to pre-ignition also need consideration before the technology can be implemented. In this regard, experiments were performed using light naphtha (RON 68) and ethanol in direct and port-fuel injection configuration, respectively. The engine load was parametrically swept by simultaneously increasing the intake air and fuel quantity until the…
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Large Eddy Simulation of Ignition and Combustion Stability in a Lean SI Optical Access Engine

Università degli Studi di Perugia-Jacopo Zembi, Francesco Mariani, Michele Battistoni
  • Technical Paper
  • 2019-24-0087
Published 2019-09-09 by SAE International in United States
Large-Eddy simulations (LES) are becoming an engineering tool for studying internal combustion engines (ICE) thanks to their ability to capture cycle-to-cycle variability (CCV) resolving most of the turbulent flow structures. ICEs can operate under lean combustion conditions to maximize efficiency. However, instabilities associated with lean combustion may cause problems, such as excessive levels of CCV or even misfires. In this context, the energy released by the spark during the ignition and its interaction with the flow field are fundamental parameters that affect ignition stability and how combustion takes place and develops. The aim of this paper is the characterization of the combustion stability in a SI optical access engine, by means of multicycle LES simulations, using CONVERGE software. Sub-grid-scale turbulence is modeled with a viscous one-equation model. Two different combustion approaches are used combined with local adaptive mesh refinement (AMR): G-equation combustion model and the perfectly stirred reactor (PSR) combustion model with a skeletal kinetic mechanism for primary reference fuel (PRF). First, a mesh sensitivity study was carried out comparing three different resolutions and discussing…
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Development of a Dedicated CNG Three-Way Catalyst Model in 1-D Simulation Platforms

FPT Industrial SpA-Stefano Golini, Francesco Giovanni Rutigliano
Istituto Motori CNR-Carlo Beatrice, Valentina Fraioli
Published 2019-09-09 by SAE International in United States
A growing interest towards heavy-duty engines powered with NG, dictated by stringent regulations in terms of emissions, has made it essential to study a specific Three-Way Catalyst (TWC). Oxygen storage phenomena characterize the catalytic converter efficiency under real world driving operating conditions and, consequently, during strong dynamics in Air-to-Fuel ratio (AFR).A numerical “quasi-steady” model has been set-up to simulate the chemical process inside the reactor. A dedicated experimental campaign has been performed in order to evaluate the catalyst response to a defined λ variation, thus providing the data necessary for the numerical model validation. In fact, goal of the present research activity was to investigate the effect of very fast composition transitions of the engine exhaust typical of the mentioned driving conditions (including fuel cutoffs etc.) on the catalyst performance and on related emissions.A surface reactions kinetic mechanism, representing CH4, CO, H2 oxidation and NO reduction, has been appropriately calibrated in steady-state operation, using a step-by-step procedure all over the engine operating conditions at different AFRs. Then transient conditions were numerically reproduced, through cyclical and…
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Inner-Insulated Turbocharger Technology to Reduce Emissions and Fuel Consumption from Modern Engines

BorgWarner Turbo Systems-Jürgen Werner
Ricardo UK Ltd-Joshua Dalby
Published 2019-09-09 by SAE International in United States
Reducing emissions from light duty vehicles is critical to meet current and future air quality targets. With more focus on real world emissions from light-duty vehicles, the interactions between engine and exhaust gas aftertreatment are critical. For modern engines, most emissions are generated during the warm-up phase following a cold start. For Diesel engines this is exaggerated due to colder exhaust temperatures and larger aftertreatment systems. The De-NOx aftertreatment can be particularly problematic. Engine manufacturers are required to take measures to address these temperature issues which often result in higher fuel consumption (retarding combustion, increasing engine load or reducing the Diesel air-fuel ratio).In this paper we consider an inner-insulated turbocharger as an alternative, passive technology which aims to reduce the exhaust heat losses between the engine and the aftertreatment. Firstly, the concept and design of the inner-insulated turbocharger is presented. A transient 3D CFD/FEM (Computation Fluid Dynamics/Finite Element Modelling) simulation is conducted and predicts that external heat losses will be reduced by 70% compared to a standard turbocharger, i.e. non-insulated turbocharger. A 1D modelling methodology…
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Back-Pressure and Fuel Type Effects on Exhaust Gas Oxygen Sensor Readings for a Single Cylinder Spark Ignition Engine Running on Gasoline and Ethanol

Istituto Motori CNR-Adrian Irimescu
  • Technical Paper
  • 2019-24-0046
Published 2019-09-09 by SAE International in United States
Application of more and more complex control strategies in spark ignition (SI) engines is required for ensuring high conversion efficiency and effective emissions reduction. Closed loop fuel injection is being implemented on an ever wider scale in small size SI units that generally feature single cylinder architecture. For such systems the readings from the exhaust gas oxygen sensor are essential for controlling air-fuel ratio and indirectly combustion. The present study looked at the influence of pressure oscillations on the values given by the sensor, for different equivalence ratio settings in wide open throttle conditions for an experimental SI unit. As expected, the readings were found to be influenced by pressure oscillations in the exhaust line during lean operation, while with stoichiometric and rich fueling the effects were minimal. Fuel type was also found to be an important aspect. Gasoline was compared to ethanol, and the latter underlined the effect of combustion efficiency on how the sensor readings need to be interpreted. Quasi-dimensional simulation using the GT-Power software was also used to provide further insight into…
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A Quasi-Dimensional Model of Pre-Chamber Spark-Ignition Engines

FEV Engine Technology-Knut Habermann
University of Naples-Fabio Bozza, Vincenzo De Bellis, Daniela Tufano, Enrica Malfi
Published 2019-04-02 by SAE International in United States
Increasingly stringent pollutant and CO2 emission standards require the car manufacturers to investigate innovative solutions to further improve the fuel economy of their fleets. Among these techniques, an extremely lean combustion has a large potential to simultaneously reduce the NOx raw emissions and the fuel consumption of spark-ignition engines. Application of pre-chamber ignition systems is a promising solution to realize a favorable air/fuel mixture ignitability and an adequate combustion speed, even with very lean mixtures.In this work, the combustion characteristics of an active pre-chamber system are experimentally investigated using a single-cylinder research engine. Conventional gasoline fuel is injected into the main chamber, while the pre-chamber is fed with compressed natural gas. In a first stage, an experimental campaign was carried out at various speeds, spark timings and air-fuel ratios. Global engine operating parameters as well as cylinder pressure traces, inside main combustion chamber and pre-chamber, were recorded and analyzed.Based on the available experimental data, a phenomenological model of this unconventional combustion system with divided combustion chambers was developed and validated. The model was then implemented…
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Optimization of a Diesel Engine with Variable Exhaust Valve Phasing for Fast SCR System Warm-Up

University of Michigan-Pavan Kumar Srinivas, Rasoul Salehi
Published 2019-04-02 by SAE International in United States
Early exhaust valve opening (eEVO) increases the exhaust gas temperature by faster termination of the power stroke and is considered as a potential warm up strategy for diesel engines aftertreatment thermal management. In this study, first, it is shown that when eEVO is applied, the engine main variables such as the boost pressure, exhaust gas recirculation (EGR) and injection (timing and quantity) must be re-calibrated to develop the required torque, avoid exceeding the exhaust temperature limits and keep the air fuel ratio sufficiently high. Then, a two-step procedure is presented to optimize the engine operation after the eEVO system is introduced, using a validated diesel engine model. In the first step, the engine variables are optimized at a constant eEVO shift. In the second step, optimal eEVO trajectories are calculated using Dynamic Programming (DP) for a transient test cycle. The optimized results indicate that with early EVO, the boost pressure should be increased to provide enough cylinder air charge and to maintain the engine torque. External EGR can be reduced due to increased internal EGR…
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Optimizing Steady State Diesel Efficiency and Emissions Using a SuperTurboTM on an Isuzu 7.8L Engine

Isuzu Motors Ltd.-Tomoyuki Itou
SuperTurbo Technologies Inc.-Barry Suelter, Thomas Waldron, Jared Brin
Published 2019-04-02 by SAE International in United States
A driven turbocharger offers many benefits for internal combustion engines over traditional turbochargers or superchargers. One type of driven turbocharger, a SuperTurbo, is an amalgamation of supercharger, turbocharger, and turbo-compounder all in one device. This is accomplished through the combination of a high-speed traction drive that transfers bi-directional torque between the turbo shaft and a CVT, which then allows for overall ratio control between the turbo and the crankshaft. High efficiency turbine designs become feasible through the removal of overspeed and turbo lag design restrictions. Isuzu recognized the benefits of a driven turbocharger and the two companies have worked to evaluate it against more conventional turbochargers. This paper documents years of simulation, development, and engine testing, with a focus on steady state optimization of a 7.8L diesel engine. While improved transient response and drive cycle efficiency have previously been published, this paper will explain how the driven turbocharger functions differently than a normal turbocharger and how it improved steady state performance by precisely controlling and balancing boost pressure, air fuel ratio, high pressure EGR, and…
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Microwave Enhancement of Lean/Dilute Combustion in a Constant-Volume Chamber

Southwest Research Institute-Yilun Luo, Terrence Alger, Barrett Mangold, Jess Gingrich, Sterling Kinkler
Published 2019-04-02 by SAE International in United States
High dilution engines have been shown to have a significant fuel economy improvement over their non-dilute counterparts. Much of this improvement comes through an increase in compression ratio enabled by the high knock resistance from high dilution. Unfortunately, the same reduction in reactivity that leads to the knock reduction also reduces flame speed, leading to the engine becoming unstable at high dilution rates. Advanced ignition systems have been shown to improve engine stability, but their impact is limited to the area at, or very near, the spark plug. To further improve the dilute combustion, a system in which a microwave field is established in the combustion chamber is proposed. This standing electric field has been shown, in other applications, to improve dilution tolerance and increase the burning velocity. The purpose of this study is to determine if a standard microwave generator can be used to couple microwaves into an engine-like combustion chamber, and if it can determine the level of combustion enhancement available at dilute conditions.For this application, a monopole antenna was designed to couple…
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The Impact of Engine Displacement on Efficiency Loss Pathways in a Highly Dilute Jet Ignition Engine

MAHLE Powertrain LLC-Nathan Peters, Michael Bunce, Hugh Blaxill
Published 2019-04-02 by SAE International in United States
Internal combustion engines currently face increasing regulatory reform which has motivated investigation of alternative combustion modes, particularly for spark ignition engines. Fuel economy regulations, among others, are presently driving the need for technological advances in the automotive sector. Stationary power generation is facing emissions standards that will be increasingly difficult to achieve with combustion-based current practices, particularly in the case of nitrogen oxides (NOx). Ultra-lean (λ > ~1.6; air-fuel ratio > 23:1) combustion via air dilution is one such combustion mode that provides the benefits of reduced fuel consumption and reduced NOx emissions. Jet ignition is a pre-chamber-based combustion system that enables enleanment beyond what is achievable with traditional spark ignition engines. Previous studies of MAHLE’s Jet Ignition® concept have primarily focused on light-duty gasoline engines. With increasing demand for fuel flexibility, particularly in power generation, and smaller engine displacement for range extender engines in automotive hybrid applications, it is important to characterize how the performance of this technology translates to other fuels and engine displacements.This paper highlights results from a 390cc, high efficiency single-cylinder…
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