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Knock Onset Detection Methods Evaluation by In-Cylinder Direct Observation

Istituto Motori CNR-Francesco Catapano, Paolo Sementa, Bianca Maria Vaglieco
  • Technical Paper
  • 2019-24-0233
To be published on 2019-10-07 by SAE International in United States
Improvement of performance and emission of future internal combustion engine for passenger cars is mandatory during the transition period toward their substitution with electric propulsion systems. In middle time, direct injection spark ignition (DISI) engines could offer a good compromise between fuel economy and exhaust emissions. However, abnormal combustion and particularly knock and super-knock are some of the most important obstacles to the improvement of SI engines efficiency. Although knock has been studied for many years and its basic characteristics are clear, phenomena involved in its occurrence are very complex and are still worth of investigation. In particular, the definition of an absolute knock intensity and the precise determination of the knock onset are arduous and many index and methodologies has been proposed. In this work, most used methods for knock onset detection from in-cylinder pressure analyses have been considered. Moreover, same methodologies were applied also to the ionization signal collected through the spark plug, properly instrumented. High speed imaging has been carried out in the combustion chamber of a high performance DISI engine provided…
 

How to Improve SI Engine Performances by Means of Supercritical Water Injection

University of Basilicata – Potenza 85100-Antonio Cantiani, Annarita Viggiano, Vinicio Magi
  • Technical Paper
  • 2019-24-0235
To be published on 2019-10-07 by SAE International in United States
The efficiency of ICEs is strongly affected by the heat losses of exhaust gases and engine cooling system, which account for about 60% of the heat released by combustion. Several technologies were developed to recover waste heat in ICEs, from turbochargers to ORCs, Stirling cycles and piezoelectric generation. A promising approach is to transfer the waste heat to a fluid, like water, and inject it into the combustion chamber. In such a way, the recovered energy is partially converted into mechanical work, by improving both engine efficiency and performance. In this work, the engine benefits obtained by using supercritical water as the vector to recover heat losses are analysed. Water has been chosen since it has a relatively high heat capacity and can be extracted directly from exhaust gases. A quasi-dimensional model has been implemented to simulate the ICE work cycle. Specifically, in this paper a spark ignition ICE, four-stroke with port fuel injection (PFI) has been considered. The model accounts for gas species properties (Janaf tables and CoolProp libraries) and includes valves opening/closing laws,…
 

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

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

Analysis of the Impact of the WLTP Procedure on CO2 Emissions of Passenger Cars

European Commission Joint Research-Biagio Ciuffo, Georgios Fontaras
Politecnico di Torino-Giuseppe DiPierro, Federico Millo, Claudio Cubito
  • Technical Paper
  • 2019-24-0240
To be published on 2019-10-07 by SAE International in United States
Until 2017, the pollutant emissions and fuel consumption Type Approval (TA) procedure for light duty vehicles in Europe was based on the New European Driving Cycle (NEDC), a test cycle performed on a chassis dynamometer. However several studies highlighted significant discrepancies in terms of CO2 emissions between the TA test and the real world, due to the limited representativeness of the actual test procedure. Therefore, the European authorities decided to introduce a new, up-to date, test procedure capable to closer represent real world driving conditions, called Worldwide Harmonized Light Vehicles Test Procedure (WLTP). This work aims to analyse the effects of the new WLTP on vehicle CO2 emissions through both experimental and simulation investigations on two different Euro 5 vehicles, a petrol and a diesel car, representatives of average European passenger cars. The study also considers the effect of the engine warm-up and the impact of the start-stop technology in this new TA scenario. It was found that, although the higher test mass and Road Loads (RLs), as well as the higher driving cycle dynamics…
 

Study of Fuel Octane Sensitivity Effects on Gasoline Partially Premixed Combustion Using Optical Diagnostics

King Abdullah Univ of Science & Tech-Hao Shi, Yanzhao An, Bengt Johansson
  • Technical Paper
  • 2019-24-0025
To be published on 2019-09-09 by SAE International in United States
Partially premixed combustion (PPC) is a low-temperature combustion (LTC) concept that could deliver higher engine efficiency, as well as lower NOx and soot emissions. Gasoline-like fuels are beneficial for air/fuel mixing process under PPC mode because they have superior auto-ignition resistance to prolong ignition delay time. In current experiments, the high octane number gasoline fuel E10 (US market used gasoline, RON=91) and low octane number GCI blend fuel (RON=77) were tested respectively in a full-transparent AVL single cylinder optical compression ignition (CI) engine. Aiming at investigating the fuel sensitivity on engine performances under different combustion modes as well as soot particle emissions, the engine operating parameters and emission data were analyzed from CI to HCCI (homogeneous charge compression ignition) via PPC (partially premixed combustion) by changing fuel injection timing. In addition, in order to get a deep insight of in-cylinder auto-ignition and combustion evolution process, planar laser-induced fluorescence (PLIF) imaging and high-speed natural flame luminosity (NFL) imaging techniques are used for visualizing fuel distribution, auto-ignition kernel development and combustion processes.
 

Performance and Emissions of an Advanced Multi-Cylinder SI Engine Operating in Ultra-Lean Conditions

Renault SA-Cédric LIBERT
University of Naples “Federico II”-Fabio Bozza, Daniela Tufano, Enrica Malfi, Luigi Teodosio, Vincenzo De Bellis
  • Technical Paper
  • 2019-24-0075
To be published on 2019-09-09 by SAE International in United States
In this work the performance and noxious emissions of a prototype Spark Ignition (SI) engine, working in ultra-lean conditions, are investigated. It is a four-cylinder engine, having a very high compression ratio, and an active pre-chamber. The required amount of air is provided by a low-pressure variable geometry turbocharger, coupled to a high-pressure E-compressor. The engine is equipped with a variable valve timing device on the intake camshaft.The goal of this activity is to support the development and the calibration of the described engine, and to exploit the full potential of the ultra-lean concept. To this aim, a combustion model for a pre-chamber engine, set up and validated in a previous paper for a similar single-cylinder unit, is utilized. It is coupled to additional in-house developed sub-models, employed for the prediction of the in-cylinder turbulence, heat transfer, knock and pollutant emissions.Such a complex architecture, schematized in a commercial 1D modeling framework, presents several control parameters which have to be properly selected to maximize the engine efficiency and minimize the noxious emissions over its whole operating…
 

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

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

Analysis of Water Injection Strategies to Exploit the Thermodynamic Effects of Water in Gasoline Engines by Means of a 3D-CFD Virtual Test Bench

Brandenburg Univ of Technology-Tim Franken, Corinna Netzer
FKFS Stuttgart-Marco Chiodi
  • Technical Paper
  • 2019-24-0102
To be published on 2019-09-09 by SAE International in United States
CO2 emission constraints taking effect from 2020 lead to further investigations of technologies to lower knock sensitivity of gasoline engines, main limiting factor to increase engine efficiency and thus reduce fuel consumption. Moreover the RDE cycle demands for higher power operation, where fuel enrichment is needed for component protection. To achieve high efficiency, the engine should be run at stoichiometric conditions in order to have better emission control and reduce fuel consumption. Among others, water injection is a promising technology to improve engine combustion efficiency, by mainly reducing knock sensitivity and to keep high conversion rates of the TWC over the whole engine map. The comprehension of multiple thermodynamic effects of water injection through 3D-CFD simulations and their exploitation to enhance the engine combustion efficiency is the main purpose of the analysis. As basis for the research a single cylinder engine derived from a 1l turbocharged 3-cylinders engine is used to evaluate indirect and direct water injection. The entire engine flow field is reproduced and analyzed with 3D-CFD simulations and numerical models are employed to…
 

Multi-Level Modeling of Real Syngas Combustion in a Spark Ignition Engine and Experimental Validation

C.M.D. S.p.A.-Domenico Cirillo
CNR Istituto Motori-Michela Costa, Gabriele Di Blasio, Daniele Piazzullo
  • Technical Paper
  • 2019-24-0012
To be published on 2019-09-09 by SAE International in United States
Syngas produced from biomass gasification is being increasingly considered as a promising alternative to traditional fuels in Spark-Ignition (SI) Internal Combustion Engines (ICEs). Due to the low energy density and extreme variability in the composition of this gaseous fuel, numerical modeling can give an important contribution to assure stable engine performances.The present work intends to give a contribution in this sense in this sense, by proposing a multi-level set of approaches, characterized by an increasing detail, as a tool aimed at the optimization of energy conversion of non-conventional fuels.At first, a specific characterization of the dependency of the syngas laminar flame speed upon its composition is achieved through an iterative approach pursued in the ANSYS ChemkinTM environment, where validated correlations of the flame speed tuning parameters are obtained in a zero-dimensional framework.Subsequently, the interaction between combustion kinetics and fluid dynamics is considered through the development of a mono-dimensional (1D) model of the whole engine system in the GT-Power environment. A predictive combustion model, tuned on the ground of the combustion parameters determined through the previous…
 

Injection Pattern Investigation for Gasoline Partially Premixed Combustion Analysis

Magneti Marelli SpA - Powertrain-Federico Stola, Matteo De Cesare
University of Bologna-Vittorio Ravaglioli, Giacomo Silvagni, Fabrizio Ponti
  • Technical Paper
  • 2019-24-0112
To be published on 2019-09-09 by SAE International in United States
Nowadays, compression-ignited engines are considered the most efficient and reliable technology for automotive applications. However, mainly due to the current emission regulations, that require increasingly stringent reductions of NOx and particulate matter, the use of diesel-like fuels is becoming a critical issue. For this reason, a large amount of research and experimentation is being carried out to investigate innovative combustion techniques suitable to simultaneously mitigate the production of NOx and soot, while improving engine efficiency. In this scenario, the combined use of compression-ignited engines and gasoline-like fuels proved to be very promising, especially in case the fuel is directly-injected in the combustion chamber at high pressure. The presented study analyzes the combustion process produced by the direct injection of gasoline in a compression-ignited light-duty engine. The engine under investigation has been modified to guarantee a stable engine operation over its whole operating range, that is achieved controlling boost pressure and temperature together with the design of the multiple injections pattern. The analysis of the experimental tests highlights the impact of several control variables on combustion…