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Optimization of Multi Stage Direct Injection-PSCCI Engines

Università degli Studi della Basilicata-Annarita Viggiano, Vinicio Magi
  • Technical Paper
  • 2019-24-0029
To be published on 2019-08-15 by SAE International in United States
The more stringent regulations on emissions induce the automotive companies to develop new solutions for engine design, including the use of advanced combustion strategies and the employment of mixture of fuels with different thermochemical properties. The HCCI combustion coupled with the partial direct injection of the charge, in order to control the performance and emissions and to extend the operating range, is a promising technique. In this work an in-house developed multi-dimensional CFD software package was used to analyse the behaviour of a multi stage direct injection (DI)-partially stratified charge compression ignition engine fueled with PRF. A skeletal kinetic mechanism for PRF oxidation was employed, with a dynamic adaptive chemistry technique to reduce the computational cost and a model based on the partially stirred reactor model to couple turbulence and chemistry. Most of the fuel was injected during the intake stroke, in order to get a homogeneous mixture of fuel and air, whereas the remaining part was injected at the end of the compression stroke, in order to stratify the fuel and temperature distributions in…
 

Possibilities of wall heat transfer measurements at a supercharged Euro IV heavy-duty Diesel engine with high EGR-rates, an in-cylinder peak pressure of 250 bar and injection pressure up to 2500 bar

Daimler AG-Christian HENNES, Jürgen Lehmann
KIT Karlsruhe Institute Of Technology-Thomas Koch
  • Technical Paper
  • 2019-24-0171
To be published on 2019-08-15 by SAE International in United States
A raise of efficiency is, especially for CV, the strongest selling point concerning the TCO. Accompanied by legislations, with contradictive development demands, satisfying solutions have to be found. The analysis of energy losses in modern engines shows three influencing parameters. The losses resulting from taking real gas properties and non-ideal combustion into account have only a limited potential for gains, wall heat losses are currently believed to have the highest optimization potential. Critical for the occurrence of these losses is the wall heat transfer, which can be described by coefficients. To reduce WHT accompanying losses a decrease of energy transfer between combustion gas and combustion chamber wall is necessary. A measurement of heat fluxes is needed to determine the WHT relations at the combustion chamber of an engine. Methods to reduce the WHT can be developed and their effectiveness can be evaluated. As this is not done before for a heavy-duty engine, with peak pressures up to 250 bar, an increased in-cylinder turbulence and high EGR-rates is presented the following. The different methods to determine…
 

A Review of Spark-Assisted Compression Ignition (SACI) Research in the Context of Realizing a Production SACI Strategy

Clemson Univ-Robert Prucka
Clemson Univ.-Dennis Robertson
  • Technical Paper
  • 2019-24-0027
To be published on 2019-08-15 by SAE International in United States
Low temperature combustion (LTC) strategies have been a keen interest in the automotive industry for over four decades since they offer improved fuel efficiency compared to conventional spark-ignition (SI) engines. LTC strategies use high dilution to keep combustion temperatures below about 2000 K to reduce heat transfer losses while avoiding locally rich in-cylinder regions that produce high soot. High dilution also enables an efficiency improvement from reduced pumping work and improved thermodynamic properties, though it requires high ignition energy. Combustion can be achieved by triggering autoignition from compression energy. High compression ratios are typically required to produce this level of ignition energy, which further improves fuel efficiency. The timing of the autoignition event is influenced by fuel properties and mixture composition, and is exponentially sensitive to temperature. Control of autoignition timing is difficult without a direct actuator, and has been a significant obstacle for realizing LTC in production. Spark-assisted compression ignition (SACI) addresses this challenge by using a spark plug to initiate chemical reactions that trigger autoignition. The combustion chamber is slightly stratified to promote…
 

One-way Coupling Methodology of Nozzle Flow and Spray for a Multi-Hole GDi Injector

AKKA-Stefano Bergamini
Toyota Motor Corp-Jun Miyagawa, Kazuhiro Uehara, Yasushi Noguchi
  • Technical Paper
  • 2019-24-0031
To be published on 2019-08-15 by SAE International in United States
With future emission regulations, progressively tighter limitations on particulate number (PN) will be applied on GDi engines. The fuel spray plays an important role on PN formation as it directly affects the homogeneity of air fuel mixture. So detailed investigation of spray characteristics is required. To reduce high prototyping cost and time of making a new injector, a predictive spray model can be used to simulate nozzle flow and spray formation. However, those models are challenging due to the complex and multi-phase phenomena occurring in the combustion chamber, but also because of the different spatial and temporal scales in the different components of the injection systems. This work presents a methodology developed to accurately simulate the spray formation by Discrete Droplet Models (DDM) without experimentally measuring the injector mass flow rate and/or momentum flux. Transient nozzle flow simulations are used instead to define the injection conditions of the spray model. The methodology is applied for the first time to a multi-hole Gasoline Direct injection (GDi). Firstly, the DDM constant values are calibrated comparing simulation results…
 

Ultra-Lean Pre-Chamber Gasoline Engine for Future Hybrid Powertrains

FEV Europe GmbH-Knut Habermann
IFP Energies nouvelles, Institut Carnot IFPEN TE-David Serrano, Jean-Marc Zaccardi
  • Technical Paper
  • 2019-24-0104
To be published on 2019-08-15 by SAE International in United States
Lean burn gasoline spark-ignition engines can support the reduction of CO2 emissions for future hybrid passenger cars. Very high efficiencies and very low NOx raw emissions can be achieved, if relative air/fuel ratios (lambda) of 2 and above can be reached. The biggest challenge here is to assure a reliable ignition process and to enhance the fuel oxidation in order to achieve a short burn duration and a good stability for the combustion. This article aims at introducing an innovative combustion system fully optimized for ultra-lean operation and very high efficiency. Thereto, a new cylinder head concept has been realized with high peak firing pressure capability and with a low surface-to-volume ratio at high compression ratios. 1D and 3D simulations have been performed to optimize the compression ratio, charge motion and intake valve lift. Numerical calculations also supported the development of the ignition system. Stable ignition and fast flame propagation were achieved thanks to a centrally located active pre-chamber which allows to control the air/fuel ratio independently of the air/fuel ratio in the main combustion…
 

Injection Pattern Investigation for Gasoline Partially Premixed Combustion Analysis

MAGNETI MARELLI SpA - Div. Powertrain-Federico Stola, Matteo De Cesare
University of Bologna-Fabrizio Ponti, Vittorio Ravaglioli, Giacomo Silvagni
  • Technical Paper
  • 2019-24-0112
To be published on 2019-08-15 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…
 

CFD analysis and knock prediction within the crevices of piston to liner fireland of a high performance I.C.E.

Ferrari Gestione Sportiva-Angelo Rosetti, Corrado Iotti, Andrea Bedogni
University of Modena e Reggio Emilia-Giuseppe Cantore, Stefano Fontanesi, Fabio Berni
  • Technical Paper
  • 2019-24-0006
To be published on 2019-08-15 by SAE International in United States
The paper aims at defining a methodology for the prediction and understanding of knock tendency in internal combustion engine piston crevices by means of CFD simulations. The motivation for the analysis comes from a real design requirement which appeared during the development of a new high performance SI unit: it is in fact widely known that, in high performance engines (especially the turbocharged ones), the high values of pressure and temperature inside the combustion chamber during the engine cycle may cause knocking phenomena. “Standard” knock can be easily recognized by direct observation of the in-cylinder measured pressure trace; it is then possible to undertake proper actions and implement design and control improvements to prevent it with relatively standard 3D-CFD analyses. Some unusual types of detonation may occur somewhere else in the combustion chamber: knocking inside piston/liner crevices belongs to the latter category and damages on the piston top land (very similar to pitting) are one of the evidence of knock onset in this region. The very localized regions of damage onset, the cycle to cycle…
 

Experimental Investigation of Combustion Characteristics in a Heavy-Duty Compression-Ignition Engine Retrofitted to Natural-Gas Spark-Ignition Operation

West Virginia Univ-Jinlong Liu
West Virginia Univ.-Cosmin Dumitrescu
  • Technical Paper
  • 2019-24-0124
To be published on 2019-08-15 by SAE International in United States
The conversion of existing diesel engines to natural gas operation can reduce U.S. dependence on petroleum imports and curtail engine-out emissions. Diesel compression ignition engines can be modified to NG spark ignition, by replacing the diesel injector with a NG spark plug and by fumigating NG in the intake manifold, to increase utilization of natural gas heavy-duty transportation sector. As the original diesel piston is maintained during conversion to decrease engine modification cost, the major of this study was to investigate the lean-burn characteristic of natural gas burning in this bowl-in-piston combustion chamber, which can accelerate the introduction of heavy-duty natural gas vehicles. Data analysis from engine experiments that changed spark timing indicated a two-stage combustion process in such retrofitted engines, which is different from traditional spark ignition engines. Inside-bowl burning is one combustion stage which experienced fast flame propagation and burned majority of fuel mass. An important mass trapped in the squish region but burned more slowly formed the other combustion stage. This combustion feature contributed to an almost identical end of combustion in…
 

Experimental and numerical analysis of a pre-chamber turbulent jet ignition combustion system

Istituto Motori CNR-Francesco Catapano, Paolo Sementa
Politecnico di Bari-Elia Distaso, Riccardo Amirante, Egidio Cassone, Pietro De Palma, Paolo Tamburrano PhD
  • Technical Paper
  • 2019-24-0018
To be published on 2019-08-15 by SAE International in United States
The growing demand for more efficient and less polluting internal combustion engine has pushed the development of non-conventional ignition systems. One of the most promising techniques appears to be the so-called Pre-Chamber initiated Turbulent Jet Ignition Combustion system in which a jet of hot combusting gasses is employed to initiate the combustion in the main chamber. In the present study, the combustion process related to this ignition system has been experimentally investigated in an optically accessible single cylinder Spark-Ignition engine. The pre-chamber was composed of a gas injector and a miniaturized spark-plug, embedded in a small annular chamber connected to the cylinder through a 4 holes pipette. A small amount of methane is injected within the pre-chamber for initiating the combustion. The flame reaches the combustion chamber through the four narrow orifices and rapidly consumes a homogeneous mixture of port injected gasoline and air. Wide open throttle conditions and various engine speeds were considered. The combustion process evolution and engine’s performance were analyzed in terms of 2D-digital imaging measurements as well as pressure and heat…
 

Development of a CFD Solver For Primary Diesel Jet Atomization in FOAM-Extend

King Abdullah Univ of Science & Tech-Hong Im
Universita degli Studi di Perugia-Michele Battistoni
  • Technical Paper
  • 2019-24-0128
To be published on 2019-08-15 by SAE International in United States
High fidelity CFD framework for the simulation of primary atomization of a high pressure diesel jet is presented in this work. The numerical model is based on a second order accurate, polyhedral Finite Volume method implemented in foam-extend, a community driven fork of the OpenFOAM software. A geometric VOF method isoAdvector is used for accurate interface advection, while the Ghost Fluid Method (GFM) is used to handle the discontinuity of the pressure and the pressure gradient at the interface between the two phases: n-dodecane and air in the combustion chamber. The discontinuities are a direct consequence of different densities and viscosities, and surface tension effects between the phases. In order to obtain highly resolved interface while minimizing computational time, an Adaptive Mesh Refinement (AMR) strategy for arbitrary polyhedral cells is employed in order to refine the parts of the mesh near the interface and within the nozzle. The developed numerical framework is tested on the Spray D geometry. The unstructured, mostly hexahedral mesh is used with the base cell size of 40 micrometres. Five refinement…