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2015-09-06
Technical Paper
2015-24-2419
Riccardo Amirante, Caterina Casavola, Elia Distaso, Paolo Tamburrano
A simply way measuring the pressure inside cylinder of internal combustion engine is proposed in this paper. It is well known that the in-cylinder pressure is one of the most significant variables describing the combustion status in internal combustion engines. The pressure as a feedback variable allows a closed loop monitoring and control techniques in order to improve engine performance and to reduce fuel consumption and emissions. This control strategy has been limited by costs, reliability and lifetime of the cylinder pressure sensors. The present paper proposes a very simple and low cost experimental device for measuring pressure inside the combustion chamber, developed for engine control and monitoring applications. The sensor exploits the strains measurements of the external wall of cylinder, which is indicative of the pressure information during the combustion process.
2015-09-06
Technical Paper
2015-24-2440
Dávid Kovács, Peter Eilts
A variable air path gives further possibilities regarding the reduction of emissions, fuel consumption and performance increase. One of the possibilities is the Miller cycle, which is known as an effective way to reduce the process temperatures and so the NOx emissions. The present paper discusses the potentials of this strategy for HD diesel engines with the goal of defining, analyzing and quantifying the benefits and the effects caused. The measurements were carried out on a heavy duty single cylinder diesel test engine equipped with an in-house developed camless variable valve actuation system. Further a flexible test environment was required to isolate the effects caused by the adjustment of the valve timing from the other engine parameters. The Miller cycle was investigated in the upper load range by advancing and retarding the intake valve closing. The first part of the investigations shows the isolated effect of the Miller strategy.
2015-09-06
Technical Paper
2015-24-2441
Robert Morgan, Andrew Banks, Andrew Auld, Morgan Heikal, Christopher lenartowicz
Diesel fuel injection pressures have increased steadily on heavy duty engines over the last twenty years and pressures as high as 3000 bar are now possible. This was driven by the need to control toxic exhaust emissions, in particular particulate emissions using in-cylinder strategies . With the introduction of efficient aftertreament systems for both particulate and NOx emissions control, there is less demand for in cylinder emissions control especially considering the drive for improved fuel economy. In this paper, we consider the benefit of high fuel injection pressure for a number of emissions control strategies. A test programme was undertaken on a single cylinder heavy duty research engine installed at the University of Brighton, in collaboration with Ricardo. The engine was fitted with the Delphi F2 fuel injection system, capable of 3000 bar injection pressure and multiple fuel injections.
2015-09-06
Technical Paper
2015-24-2445
Carlo Beatrice, Gabriele Di Blasio, Ezio Mancaruso, Luigi Sequino, Bianca Maria Vaglieco
In this paper, a detailed combustion and emission analysis is carried out on both metal and optical research light duty diesel engines equipped with up-to-date combustion architecture. Both engines were fed by glycerol ethers mixture (GEM) in blend of 20% v/v within a commercial diesel fuel. The engines run in significant operating points in the NEDC (New European Driving Cycle) emission homologation area. The results of the experimental campaign on the metal engine show comparable performances between the diesel/GEM blend and the diesel fuel and demonstrate benefits mainly in terms of soot production and particle size distribution. In particular, the particles diameters of diesel/GEM blend shift toward smaller dimensions and the total number decreases. Moreover, at lower load conditions, the outputs show a worsening of the unburnt mainly ascribable to the fuel characteristics.
2015-09-06
Technical Paper
2015-24-2476
Christian Pötsch, Laura Sophie Baumgartner, Daniel Koch, Felix Bernhard, Bastian Beyfuss, Georg Wachtmeister, Donatus Wichelhaus
Alongside with the severe restrictions according to technical regulations of the corresponding racing series (air and/or fuel mass flow), the optimization of the mixture-formation in SI-race engines is one of the most demanding challenges with respect to engine performance. Bearing in mind its impact on the ignition behavior and the following combustion, the physical processes during mixture-formation play a vital role not only in respect of the engine’s efficiency, fuel consumption, and exhaust gas emissions but also on engine performance. Furthermore, abnormal combustion phenomena such as engine knock may be enhanced by insufficient mixture-formation. This can presumably be explained by the strong influence of the spatial distribution of the air-fuel-ratio on the inflammability of the mixture as well as the local velocity of the turbulent flame front.
2015-09-06
Technical Paper
2015-24-2478
Johannes Palmer, Mogan Ramesh, Valeri Kirsch, Manuel Reddemann, Reinhold Kneer
Fuel blends are one possible solution to improve the performance of biofuels in engines. Two candidates for a biofuel blend are the linear C8H18O isomers 1-octanol and di-n-butyl ether (DNBE). Both fuels feature an increased amount of oxygen that reduces soot emissions in a diesel engine. However, material properties differ significantly and a different type of spray mixing and combustion is expected. The reduced reactivity of 1-octanol causes a longer ignition delay that allows an extended spray mixing phase for better homogenization. The lower reactivity of 1-octanol comes along with increased HC and CO emissions. DNBE in contrary is more volatile and has a short ignition. The high Cetane number of DNBE makes it an ideal blend component for 1-octanol in order to act as an ignition booster without losing any positive effects in terms of soot emissions.
2015-09-06
Technical Paper
2015-24-2477
Ezio Mancaruso, Renato Marialto, Luigi Sequino, Bianca Maria Vaglieco, Massimo Cardone
Blends of propane-diesel fuel can be used in direct injection diesel engines to improve the air-fuel mixing and the premixed combustion phase, and to reduce pollutant emissions. The potential benefits to use propane in Diesel engines are both environmental and economic; furthermore, its use does not require changes to the compression ratio of conventional diesel engines. The present paper describes an experimental investigation of injection process for different liquid preformed blends of propane-diesel fuel in an optically accessible Common Rail diesel engine. To operate with a blend of propane–diesel fuel slight modification of the injection system were required. Pure diesel fuel and two propane-diesel mixtures at different mass ratio have been tested (20% and 40% in mass of propane named P_20 and P_40).
2015-09-06
Technical Paper
2015-24-2484
Enrico Mattarelli, Carlo Alberto Rinaldini
An interesting alternative to the first or second generation of biodiesels is the oil derived from microalgae. Biofuels from microalgae are classified as third generation, both because they do not compete with food crops in land use, as done by the first generation, and for their distinguishing properties such as: very rapid growth rate, high CO2 fixation capability and high content of lipids. While the use of first generation biodiesels on different types of compression ignition engines is well documented in the open literature, much less information is available on algal fuels. In fact, the influence on combustion and pollutant emissions is not definitively assessed, depending on the combination of the specific features of both fuel and engine. The aim of this paper is to analyze the combustion process in an industrial engine fueled by an algal Biodiesel, blended with standard Diesel fuel.
2015-09-06
Technical Paper
2015-24-2485
Tamara Ottenwaelder, Thomas Raffius, Christian Schulz, Philipp Adomeit, Gerd Grunefeld, Stefan Pischinger
In order to reduce engine out CO2 emissions it is a main subject to find new alternative fuels out of renewable sources. For this reason in this paper a blend out of 1-octanol and di-n-butylether and pure di-n-butylether are investigated in comparison to n-Heptane as diesel- like fuel. The alternative fuels have a different combustion behavior particularly concerning important combustion parameters like ignition delay and mixture formation. Especially the formation of pollutants like nitrogen oxides in the combustion of alternative fuels is of global interest. The knowledge of the combustion behavior is important to design new engine geometries or implement a new calibration of the engine. In previous measurements in a single cylinder engine was it found out that both alternative fuels form nearly no soot emissions.
2015-09-06
Technical Paper
2015-24-2482
Wolfgang Mühlbauer, Sebastian Lorenz, Dieter Brueggemann
In view of finite fossil energy sources and discussions about CO2 as a main cause for climate warming, a scientific and engineering challenge is to replace fossil by alternative diesel fuels. Relating to more strict European emission standards, diesel engines have to meet strong limits for particulate number emissions. Biogenic diesel fuels of the first generation like biodiesel (fatty acid methyl esters from rapeseed, soybean and palm oil) are under critical discussion. Its production is even in direct competition with foodstuff and needs extended cultivated areas. Therefore, many research groups have worked on the production of biogenic fuels of the second generation in the last few years. These fuels could be derived from cellulosic sources like plant material, which is not used for foodstuff production. According to recent studies, di-n-butyl ether (DNBE) is one of the promising second generation biofuels, which could be synthesized via etherification of n-butanol.
2015-09-06
Technical Paper
2015-24-2490
Francesco Catapano, Silvana Di Iorio, Paolo Sementa, Bianca Maria Vaglieco
Ethanol is the most promising alternative fuel for spark ignition (SI) engines. Typically, it is blended with gasoline. However, in the last years great attention is paid to the dual fueling, ethanol and gasoline are injected simultaneously. This paper aims to analyze the better methods, blending or dual fueling, to best exploit the potential of ethanol in improving engine performance and reducing pollutant emissions. The experimental activity was carried out in a small displacement single cylinder engine, representative of 2-3 wheel vehicle engines or of 3-4 cylinder small displacement automotive engines. It was equipped with a prototype gasoline direct injection (GDI) head. The tests were carried out at 3000 rpm, 4000 rpm and 5000 rpm full load. The investigated engine operating conditions are representative of the homologation urban driving cycle. The gaseous and particle emissions were measured at the exhaust by means of a gas analyzer and a smoke meter.
2015-09-06
Technical Paper
2015-24-2488
Martin Pechout, Ales Dittrich, Martin Mazac, Michal Vojtisek-Lom
Butanol, which can be produced from biomass, has been suggested as an alternative to ethanol, due to its higher energy density, lower oxygen content and more favorable hygroscopic and corrosive properties. In the Czech Republic, E85 is widely sold at fuel stations despite a minimum of registered flexible-fuel vehicles. It is therefore used in ordinary vehicles, both with and without aftermarket control units. The potential of ordinary automobiles to run on butanol, and the associated effects on exhaust emissions, has been therefore investigated. A Škoda Felicia car with a throttle body injection and a Škoda Fabia car with a multi-point port injection has been run on gasoline and mixtures of gasoline with ethanol, with n-butanol, and with isobutanol (2-methyl-1-propanol), containing up to 85% of alcohol by volume. An auxiliary control unit has been used with higher alcohol content. On each fuel, both cars were driven multiple times along a local test route.
2015-09-06
Technical Paper
2015-24-2500
Nic van Vuuren, Gabriele Brizi, Giacomo Buitoni, Lucio Postrioti, Carmine Ungaro
One of the favored automotive exhaust aftertreatment solutions used for nitrogen oxides (NOx) emissions reductions is referred to as Selective Catalytic Reduction (SCR), which comprises a catalyst that facilitates the reactions of ammonia (NH3) with the exhaust nitrogen oxides (NOx). It is customary with these systems to generate the NH3 by injecting a liquid aqueous urea solution, referred to as AUS-32, and also known under its commercial name of AdBlue® in Europe, and DEF – Diesel Exhaust Fluid – in the USA. The urea solution is injected into the exhaust and transformed to NH3 by various mechanisms for the SCR reactions. Understanding the spray performance of the AUS-32 injector is critical to proper optimization of the SCR injection system. Results were previously presented from imaging of an AUS-32 injector spray under hot exhaust conditions at the injector spray exit for an exhaust injection application.
2015-09-06
Technical Paper
2015-24-2493
Mario Milanese, Mario Bonansone
Low Carbon fuels will play a relevant role in the transportation sector contributing, over the powertrain technology progress, to mitigate global CO2 emissions. Compressed Natural Gas (CNG), mainly composed by methane, is one of the best candidate thanks to its chemical composition and to its wide diffusion and use. Blending Hydrogen in Natural Gas could represent a further step for a better CO2 footprint (considering renewable or biohydrogen) but also to optimize the combustion process, increasing the engine thermal efficiency and reducing pollutant formation. On the other hand, capability to automatically adapt the engine parameters to variable concentrations of Hydrogen in Natural Gas (in the range from 0% to 40% by volume) is a mandatory step to maintain engine performance, emissions and efficiency.
2015-09-06
Technical Paper
2015-24-2532
Reinhard Ratzberger, Thomas Kraxner, Jochen Pramhas, Klaus Hadl, Helmut Eichlseder, Ludwig Buergler
The continuously decreasing emission limits lead to a growing importance of exhaust aftertreatment in diesel engines. Hence methods for achieving a rapid catalyst light off after engine cold start and for maintaining the catalyst temperature during low load operation will become more and more necessary. The present work evaluates several valve timing strategies concerning their ability for doing so. For this purpose simulations as well as experimental investigations were conducted. A special focus of simulation was on pointing out relevance of exhaust temperature and mass flow for these thermomanagement tasks. An increase of exhaust temperature is beneficial for both heat up catalyst and maintaining catalyst temperature. In case of the exhaust massflow, high values are advantageous only in case of a catalyst heat up process, while maintaining catalyst temperature is supported by a low mass flow.
2015-09-06
Technical Paper
2015-24-2525
Luigi De Simio, Sabato Iannaccone, Michele Gambino, Veniero Giglio, Natale Rispoli, Gianluca Barbolini, Dario Catanese, Marco Ferrari, Walter Lo Casale
This paper presents an experimental study on a 2-stroke SI engine, used on small portable tools for gardening or agriculture, aimed to identify possible correlations between parameters related to ionization current and air/fuel mixture richness, considering different fuels and spark plug wear. This, to realize a simple system to control the engine parameters and adapt them to engine aging and fuel type changing. The engine was fed with commercial gasoline, low octane number gasoline, alkylate gasoline and a blend of 80% gasoline and 20% ethanol. In all tests carried out with varying engine speed and spark advance the ionization signal was characterized by a single peak, resulting in the impossibility of distinguishing chemical and thermal ionization. All data collected were analyzed looking for correlations between all the available data of CO emissions and several characteristic parameters obtained from the ionization signal.
2015-09-06
Technical Paper
2015-24-2533
Mirko Bovo, Joop Somhorst
The focus on engine thermal management is rapidly increasing due to the significant effect of heat losses on fuel consumption, engine performance and emissions. Thermal management is particularly relevant during the engine warm-up process. Engines are complex, multifunctional, highly three dimensional machines for which it is particularly challenging to model all relevant heat interactions. A modern approach to the study of engine heat balance is the use of numerical simulations. See for example [A New Tool to Perform Global Energy Balances in DI Diesel Engines, SAE 2014-01-0665]. A challenge is to implement in the model, with adequate time-space resolution, all relevant systems (e.g. cooling, oil), the geometrical complexity and the boundary conditions. This work presents the realization, calibration and verification of a high space resolution 3D complete engine heat balance model, including all relevant components.
2015-09-06
Technical Paper
2015-24-2534
Jochen Bregar, Adrian Rienäcker, Marcus Gohl, Gunter Knoll
Increased quantities of fuel in the engine oil pose a major challenge to the automotive industry in terms of controlling the oil aging and the wear caused by dilution. Due to a lack of methods to calculate the oil-fuel-composite transport across the ring pack, predicting the fuel ratio in the oil sump has been an extremely challenging task for engine manufacturers. An accurate and computationally efficient simulation model is critical to predict the quantity of fuel diluted in the oil in an early stage of development. In this work, the complex composite transport across the piston ring pack was reduced to a simple transport model, which was successfully implemented into a multi-body simulation of the ring pack. The calculation domain was partitioned into two parts, the ring grooves and the piston lands. Inside the grooves the oil flux caused by the pumping and squeezing action of the piston rings was calculated using the Reynolds equation.
2015-09-06
Technical Paper
2015-24-2536
Julien Bouilly, Francois Lafossas, Ali Mohammadi, Roger Van Wissen
Reducing pollutant and CO2 emissions while increasing customer comfort is a continuous challenge that requires more and more sophisticated technologies. However, it is often difficult to know in advance the benefit of a technology without having its prototype parts and/or knowing the optimal control strategy. In order to meet these challenges, TME has developed a vehicle thermal model in AMESim to evaluate the benefits of an Active Grille Shutter (AGS) on fuel consumption. The vehicle model is based on a C-Segment vehicle powered by a 1.4L Diesel engine. The complete oil and coolant circuits are modeled as well as a friction model based on engine coolant temperature. The entire model was validated on NEDC at -7°C and +25°C and achieved an accurate estimation of the fuel consumption, coolant and oil temperatures.
2015-09-06
Technical Paper
2015-24-2414
Vesselin Krassimirov Krastev, Gino Bella, Gennaro Campitelli
Scale-resolving turbulence modeling for engine flow simulation has steadily increased its popularity in the last decade. In contrast to classical RANS modeling approaches, LES-like approaches are able to resolve a larger number of unsteady features of the flow. This capability allows in principle to produce accurate CFD predictions of some key aspects related to the engine development and optimization, such as cycle-to-cycle variations in a modern DI engine. However, since multiple simulated engine cycles are required to extract reliable flow statistics, the high spatial and temporal resolution required by pure LES represents a severe limit to its wider application in studies on realistic engine geometries. Hybrid URANS-LES methodologies can thus become a potentially attractive option to preserve the scale-resolving capability in the core regions of the flow but at significantly lower overall computational costs compared to standard LES.
2015-09-06
Technical Paper
2015-24-2474
The potential of the stratified operation of a high pressure natural gas direct injection (DI) spark ignition (SI) engine was investigated. Fuel efficiency, emissions and indication measurement data were evaluated using a thermodynamic single-cylinder engine. Investigations of the mixture formation were performed on a geometric equivalent optically accessible single-cylinder engine. The two optical measurement techniques infrared (IR) absorption and laser-induced fluorescence (LIF) were employed. Mid wavelength IR absorption is qualified for a global visualization of the natural gas injection into the combustion chamber and LIF allows quantifying the air/fuel ratio inside a detection level. While LIF measurements require complex equipment, the IR setup consists of a black body heater and a mid wavelength sensitive IR camera. Methane absorbs IR radiation at about 3.4µm.
2015-09-06
Technical Paper
2015-24-2487
AETs(Alternative Energy Technologies) are imperative to mitigate the twin crisis of environmental degradation and simultaneous fossil fuel depletion, there are wide concerns about GHG(Green House Gas) emissions which have paved ways for the development and deployment of energy technologies that do not use fossil fuels. These technologies would provide tangible benefits in terms of fossil-fuel costs, which are likely to increase as restrictions on GHG emissions are imposed. However, a number of challenges need to be overcome prior to market positioning, and the commercialization of alternative energy technologies which require a staged approach given price and technical risk. An unconventional new alternative technology is one possibility, where one could undertake cost-reducing production enhancement measures as an intermediate step prior to deployment.
2015-09-06
Technical Paper
2015-24-2420
Fabrizio Ponti, Vittorio Ravaglioli, Matteo De Cesare, Federico Stola, Davide Moro
The increasing request for pollutant emissions reduction spawned a great deal of research in the field of Low Temperature Combustion (LTC) strategies, that allow obtaining a significant reduction both in particulate matter and NOx emissions. Unfortunately, due to their nature, these innovative combustion strategies are very sensitive to in-cylinder thermal conditions. Therefore, in order to obtain a stable combustion, a closed-loop combustion control methodology is needed. Many works demonstrate that a closed-loop combustion control strategy can be based on the real-time analysis of in-cylinder pressure trace, that provides important information about the combustion process, such as Start (SOC) and Center of combustion (MFB50), torque delivered by each cylinder an Combustion Noise. Nevertheless, cylinder pressure sensors on-board installation is still uncommon, due to problems related to unsatisfactory measurement long term reliability and cost.
2015-09-06
Technical Paper
2015-24-2415
Katarzyna Danuta Bizon, Simone Lombardi, Gaetano Continillo, Paolo Sementa, Bianca Maria Vaglieco
Data decomposition techniques has become a standard approach for the analysis of the 2D imaging data originating from optically accessible internal combustion engines. In particular the method of Proper Orthogonal Decomposition (POD) has proven to be valuable tool for the evaluation of the cycle-to-cycle variability based on luminous combustion imaging and particle image velocimetry (PIV) measurements. Recently, an alternative procedure based on Independent Component Analysis (ICA) has been introduced in the engine field. Unlike POD which basically permits to characterize the dominant structures of the examined process, the method of ICA identifies the patterns corresponding to the independent physical processes. In this work, a Group-ICA approach applied to 2D cycle-resolved images of the luminosity emitted by the combustion process is used to capture cyclic variability of a port fuel injection spark ignition (PFI SI) engine.
2015-09-06
Technical Paper
2015-24-2547
Ali Fuat Ergenc, Alp Ergenc, Caner Erdogan, Alper Dumanli
A new control method for engagement/disengagement, gear selection and gear shifting for the commercial and the passenger vehicles is proposed. The method aims to minimize the total gear-shifting time and minimum transition effect for commercial and passenger vehicles. In modified transmission system, a magnetic powder clutch is employed for engagement purposes and a manual-automated gearbox is used for transmission purposes. The rationale behind the selection of magnetic powder clutch is the swiftness of the operation. Automated-manual gearbox is utilized due to its combination of ease of construction and ability for electronic automation. The study includes system identification of the powder clutch behavior and a new closed loop controller for smooth operation. In shifting of the automated-manual gearbox is actuated with two servo-motors which are also part of closed loop control of the structure. In the study, theoretical approach and experimental results are presented.
2015-09-06
Technical Paper
2015-24-2385
Guillaume Alix, Jean-Charles Dabadie, Gregory Font
Legal constraints concerning CO2 emissions have made the improvement of light duty vehicle efficiency mandatory. In result, vehicle powertrain and its development have become increasingly complex, requiring the ability to assess rapidly the effect of several technological solutions, such as hybridization or internal combustion engine (or ICE) downsizing, on vehicle CO2 emissions. In this respect, simulation is nowadays a common way to estimate a vehicle’s fuel consumption on a given driving cycle. This estimation can be done with the knowledge of vehicle main characteristics, its transmission ratio and efficiency and its internal combustion engine (ICE) fuel consumption map. While vehicle and transmission parameters are relatively easy to know, the ICE consumption map has to be obtained through either test bench measurements or computation.
2015-09-06
Technical Paper
2015-24-2387
Emiliano Vitaliani, Daniele Di Rocco, Martin Sopouch
The aim of this paper is the study of the Centrifugal Pendulum Vibration Absorber (CPVA) dynamic behaviour, with the background of improved vibration isolation and damping quality through a wide range of operating speeds. The CPVAs are passive devices, which are used in rotating machinery to reduce the torsional vibration without decreasing performance. After a first use of these damping systems in the field of aeronautics, nowadays CPVAs are employed also in railway and automotive applications. In principle, the CPVA is a mass, mounted on a rotor, which moves along a defined path relative to the rotor itself, driven by centrifugal effects and by the rotor torsional vibrations. The advantage that such absorbers provide is the capability to counteract torsional vibrations arising with frequencies proportional to the mean operating speed. This is in particular the case with Internal Combustion Engines (ICE) where the induced vibrations are caused by the combustions process.
2015-09-06
Technical Paper
2015-24-2390
Shashi Aithal, Stefan Wild
Design and optimization of automotive engines present unique challenges on account of the large design space and conflicting constraints. Optimizing the fuel consumption and reducing emissions over a driving cycle is a good example. Inlet pressure, equivalence ratio, humidity, EGR fraction, inlet air temperature, ignition timing, engine load, engine speed (RPM) etc. each impact fuel consumption and emissions and thus represent a vast parametric space to conduct de sign and global optimization studies. This large parametric space is further increased when one has to consider newer fuels and fuel-blends (varying ratios of fuel-additive mixtures) further complicating the design-optimization problem. The large design parameter space precludes the use of detailed numerical or experimental investigations. Physics-based reduced-order models (quasi-dimensional models) can be used effectively in the design and global optimization of such problems.
2015-09-06
Technical Paper
2015-24-2392
Vincenzo De Bellis, Luigi Teodosio, Daniela Siano, Fabrizio Minarelli, Diego Cacciatore
In this paper, a high performance V12 spark-ignition engine is experimentally investigated at test-bench in order to fully characterize its behavior in terms of both average and cycle-by-cycle performance parameters, for different operating conditions. In particular, for each considered point, a spark advance sweep is actuated, starting from a knock-free calibration, up to intense knock operation. Trains of 300 consecutive pressure cycles are acquired for each of the 12 cylinders, together with the main overall engine performance, including air flow, fuel flow, torque, pollutant emissions, and fuel consumption. Acquired data are statistically analyzed to derive the distributions of main indicated parameters (combustion phasing and duration, Indicated Mean Effective Pressure - IMEP, etc.) in order to find proper correlation with averaged quantities, collecting the findings of all the considered operating points and all the cylinders.
2015-09-06
Technical Paper
2015-24-2410
Stefania Falfari, Claudio Forte, Gian Bianchi, Giulio Cazzoli, Cristian Catellani, Lucio Postrioti, Fabrizio Ottobre
In the next incoming future the necessity of reducing the raw emissions leads to the challenge of an increment of the thermal engine efficiency. In particular it is necessary to increase the engine efficiency not only at full load but also at partial load conditions. In the open literature very few technical papers are available on the partial load conditions analysis. In the present paper the analysis of the effect of the throttle valve rotational direction on the mixture formation is analyzed. The engine was a PFI 4-valves motorcycle engine. The engine geometry was formed by the intake duct and the cylinder. The throttle valve opening angle was 17.2 deg, which lays between the very partial load and the partial load condition. The CFD code adopted for the analysis was the FIRE AVL code v. 2013.2. The intake and the compression phases till TDC were simulated: inlet boundary conditions from 1D simulations were imposed.
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