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Technical Paper
Mirko Baratta, Daniela Misul, Prashant Goel, Danilo Laurenzano MD, Betrand Lecointe, Loic Rouleau, Frederic Ravet, Panagiotis Christou
The present paper is concerned with part of the work performed by Renault, IFPEN and Politecnico di Torino within the Gason research project (H2020 framework of the EC). More precisely, the overall objectives of the project mainly consist in the reduction of the carbon footprint through the mitigation of the CO2 emissions, as well as in the reinforcement of alternative fuels so as to progressively decrease the dependence on crude oil. Accordingly, the Gason WP4 is focused on the development of a dedicated CNG engine featuring a 25% decrease in fuel consumption with respect to an equivalent Diesel engine with the same performance targets. To that end, based on the previous experience of the partners in the Mogador and InGAS projects, the present work has been primarily devoted to the optimization and implementation of different breakthrough technologies in the Gason engine, namely, direct injection, variable valve timing, LP EGR with advanced turbocharging, and diluted combustion.
Journal Article
Hamed Kheshtinejad, Mirko Baratta, Danilo Laurenzano, Claudio Maino, Daniela Anna Misul
CNG is at present retaining a growing interest as a factual alternative to traditional fuels for SI engines, thanks to its high potentials in reducing the engine-out emissions. Increasing thrust into the exploitation of NG in the transport field is in fact produced by the even more stringent emission regulations that are being introduced into the worldwide scenario. The present paper aims at deeply investigating into the potentials of a heavy-duty engine running on CNG and equipped with two different injection systems, an advanced single point (SP) one and a prototype multi-point (MP) one. The considered 7.8-liter engine was designed and produced to implement a SP strategy and hence modified to run with a dedicated MP system. A thorough comparison of the engine equipped with the two injection systems has been carried out at steady state as well as at transient operations.
Journal Article
Mirko Baratta, Daniela Misul, Jiajie Xu, Alois Fuerhapter, Rene Heindl, Cesare Peletto, Jean Preuhs, Patrick Salemi
Abstract Natural gas is a promising alternative fuel for internal combustion engine application due to its low carbon content and high knock resistance. Performance of natural gas engines is further improved if direct injection, high turbocharger boost level, and variable valve actuation (VVA) are adopted. Also, relevant efficiency benefits can be obtained through downsizing. However, mixture quality resulting from direct gas injection has proven to be problematic. This work aims at developing a mono-fuel small-displacement turbocharged compressed natural gas engine with side-mounted direct injector and advanced VVA system. An injector configuration was designed in order to enhance the overall engine tumble and thus overcome low penetration.
Journal Article
Mirko Baratta, Roberto Finesso, Daniela Misul, Ezio Spessa
Abstract The potential of internal EGR (iEGR) and external EGR (eEGR) in reducing the engine-out NOx emissions in a heavy-duty diesel engine has been investigated by means of a refined 1D fluid-dynamic engine model developed in the GT-Power environment. The engine is equipped with Variable Valve Actuation (VVA) and Variable Geometry Turbocharger (VGT) systems. The activity was carried out in the frame of the CORE Collaborative Project of the European Community, VII FP. The engine model integrates an innovative 0D predictive combustion algorithm for the simulation of the HRR (heat release rate) based on the accumulated fuel mass approach and a multi-zone thermodynamic model for the simulation of the in-cylinder temperatures. NOx emissions are calculated by means of the Zeldovich thermal and prompt mechanisms.
Technical Paper
Daniela Anna Misul, Mirko Baratta, Hamed Kheshtinejad
Abstract Sustainable mobility has become a major issue for internal combustion engines and has led to increasing research efforts in the field of alternative fuels, such as bio-fuel, CNG and hydrogen addition, as well as into engine design and control optimization. To that end, a thorough control of the air-to-fuel ratio appears to be mandatory in SI engine in order to meet the even more stringent thresholds set by the current regulations. The accuracy of the air/fuel mixture highly depends on the injection system dynamic behavior and to its coupling to the engine fluid-dynamic. Thus, a sound investigation into the mixing process can only be achieved provided that a proper analysis of the injection rail and of the injectors is carried out. The present paper carries out a numerical investigation into the fluid dynamic behavior of a commercial CNG injection system by means of a 0D-1D code.
Journal Article
Mirko Baratta, Roberto Finesso, Hamed Kheshtinejad, Daniela Misul, Ezio Spessa, Yixin Yang, Massimo Arcidiacono
An innovative 0D predictive combustion model for the simulation of the HRR (heat release rate) in DI diesel engines was assessed and implemented in a 1D fluid-dynamic commercial code for the simulation of a Fiat heavy duty diesel engine equipped with a Variable Geometry Turbocharger system, in the frame of the CORE (CO2 reduction for long distance transport) Collaborative Project of the European Community, VII FP. The 0D combustion approach starts from the calculation of the injection rate profile on the basis of the injected fuel quantities and on the injection parameters, such as the start of injection and the energizing time, taking the injector opening and closure delays into account. The injection rate profile in turn allows the released chemical energy to be estimated. The approach assumes that HRR is proportional to the energy associated with the accumulated fuel mass in the combustion chamber.
Technical Paper
Mirko Baratta, Stefano D'Ambrosio, Daniela Anna Misul
An experimental investigation was performed on a turbocharged spark-ignition 4-cylinder production engine fuelled with natural gas and with two blends of natural gas and hydrogen (15% and 25% in volume of Hâ‚‚). The engine was purposely designed to give optimal performance when running on CNG. The first part of the experimental campaign was carried out at MBT timing under stoichiometric conditions: load sweeps at constant engine speed and speed sweeps at constant load were performed. Afterwards, spark advance sweeps and relative air/fuel ratio sweeps were acquired at constant engine speed and load. The three fuels were compared in terms of performance (fuel conversion efficiency, brake specific fuel consumption, brake specific energy consumption and indicated mean effective pressure) and brake specific emissions (THC, NOx, CO).
Technical Paper
Mirko Baratta, Nicola Rapetto, Ezio Spessa, Alois Fuerhapter, Harald Philipp
This paper presents the results of part of the research activity carried out by the Politecnico di Torino and AVL List GmbH as part of the European Community InGAS Collaborative Project. The work was aimed at developing a combustion system for a mono-fuel turbocharged CNG engine, with specific focus on performance, fuel economy and emissions. A numerical and experimental analysis of the jet development and mixture formation in an optically accessible, single cylinder engine is presented in the paper. The experimental investigations were performed at the AVL laboratories by means of the planar laser-induced fluorescence technique, and revealed a cycle-to-cycle jet shape variability that depended, amongst others, on the injector characteristics and in-cylinder backpressure. Moreover, the mixing mechanism had to be optimized over a wide range of operating conditions, under both stratified lean and homogeneous stoichiometric modes.
Journal Article
Mirko Baratta, Andrea E. Catania, Ezio Spessa, Lothar Herrmann, Klaus Roessler
Direct injection (DI) of natural gas (NG) at high pressure conditions has emerged as a high-potential strategy for improving SI engine performance. Besides, DI allows an increase in the fuel economy, due to the possibility of a significant engine dethrottling at partial load. The high-pressure gas injection can also increase the turbulence level of mixture and thus the overall fuel-air mixing. Since direct NG injection is an emerging technology, there is a lack of experience on the optimum configuration of the injection system and the associated combustion chamber design. In the last few years, some numerical investigations of gas injection have been made, mainly oriented at the development of reliable numerical investigation tools. The present paper is concerned with the development and application of a numerical Star-CD based model for the investigation of the direct NG injection process from a poppet-valve injector into a bowl-piston engine combustion chamber.
Technical Paper
M. Baratta, A. E. Catania, E. Spessa, A. Vassallo
A combustion simulation code for the prediction of heat release, flame propagation speed and pollutant formation in SI engines was developed and assessed. It is based on a multizone combustion model that takes the non-uniform spatial distribution of the in-cylinder burned-gas thermochemical properties into account. The multizone approach for burning rate calculation is coupled with a CAD procedure for the evaluation of burned-gas front area and radius. Specifically developed sub-models for determining CO and NO formation are included in the code. An original model based on the fractal geometry concept was used to describe the entrainment of fresh mixture through the flame front.
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