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Technical Paper

A “Dynamic System” Approach for the Experimental Characterization of a Multi-Hole Spray

2017-09-04
2017-24-0106
The analysis of a spray behavior is confined to study the fluid dynamic parameters such as axial and radial velocity of the droplets, size distribution of the droplets, and geometrical aspect as the penetration length. In this paper, the spray is considered like a dynamic system and consequently it can be described by a number of parameters that characterize its dynamic behavior. The parameter chosen to describe the dynamic behavior is the external cone angle. This parameter has been detected by using an experimental injection chamber, a multi-hole (8 holes) injector for GDI applications and recorded by a high-speed C-Mos camera. The images have been elaborated by a fuzzy logic and neural network algorithm and are processed by using a chaos deterministic theory. This procedure carries out a map distribution of the working point of the spray and determines the stable (signature of the spray) and instable behavior.
Technical Paper

Analysis and Design of an Intake Filter Box for a Downsized VVA Engine

2014-04-01
2014-01-1693
The present paper reports 1D and 3D CFD analyses of the air-filter box of a turbocharged VVA engine, aiming to predict and improve the gas-dynamic noise emissions through a partial re-design of the device. First of all, the gas-dynamic noise at the intake mouth is measured during a dedicated experimental campaign. The developed 1D and 3D models are then validated at full load operation, based on experimental data. In particular, 1D model provides a preliminary evaluation of the radiated noise and simultaneously gives reliable boundary conditions for the unsteady 3D CFD simulations. The latter indeed allow to better take into account the geometrical details of the air-filter and guarantee a more accurate gas-dynamic noise prediction. 3D CFD analyses put in evidence that sound emission mainly occur within a frequency range of 350 to 450 Hz.
Journal Article

Analysis of Knock Tendency in a Small VVA Turbocharged Engine Based on Integrated 1D-3D Simulations and Auto-Regressive Technique

2014-04-01
2014-01-1065
In the present paper, two different methodologies are adopted and critically integrated to analyze the knock behavior of a last generation small size spark ignition (SI) turbocharged VVA engine. Particularly, two full load operating points are selected, exhibiting relevant differences in terms of knock proximity. On one side, a knock investigation is carried out by means of an Auto-Regressive technique (AR model) to process experimental in-cylinder pressure signals. This mathematical procedure is used to estimate the statistical distribution of knocking cycles and provide a validation of the following 1D-3D knock investigations. On the other side, an integrated numerical approach is set up, based on the synergic use of 1D and 3D simulation tools. The 1D engine model is developed within the commercial software GT-Power™. It is used to provide time-varying boundary conditions (BCs) for the 3D code, Star-CD™.
Technical Paper

Analysis of the Cooling Plant of a High Performance Motorbike Engine

2012-04-16
2012-01-0354
This paper is based on a Research Project of the Department of Mechanical Engineering (DiME) in collaboration with Aprilia, the Italian motorbike manufacturer. In an attempt to simulate the functioning of the cooling plant of the Aprilia RSV-4 motorbike a numerical model was constructed using mono-dimensional and three-dimensional simulation codes. Our ultimate aim was to create a simulation model which could be of assistance to engine designers to improve cooling plant performance, thereby reducing research and development costs. The model allows to simulate the running conditions of the whole cooling circuit upon variations in environmental and running conditions. In particular, the centrifugal pump of the cooling plant was simulated by a 3D commercial software, while the whole circuit was built by a 1D commercial code which allows simulation of all the thermal exchanges and pressure drops in the cooling circuit.
Technical Paper

CFD Modeling and Validation of the ECN Spray G Experiment under a Wide Range of Operating Conditions

2019-09-09
2019-24-0130
The increasing diffusion of gasoline direct injection (GDI) engines requires a more detailed and reliable description of the phenomena occurring during the fuel injection process. As well known the thermal and fluid-dynamic conditions present in the combustion chamber greatly influence the air-fuel mixture process deriving from GDI injectors. GDI fuel sprays typically evolve in wide range of ambient pressure and temperatures depending on the engine load. In some particular injection conditions, when in-cylinder pressure is relatively low, flash evaporation might occur significantly affecting the fuel-air mixing process. In some other particular injection conditions spray impingement on the piston wall might occur, causing high unburned hydrocarbons and soot emissions, so currently representing one of the main drawbacks of GDI engines.
Technical Paper

Chaos Theory Approach as Advanced Technique for GDI Spray Analysis

2017-03-28
2017-01-0839
The paper reports an innovative method of analysis based on an advanced statistical techniques applied to images captured by a high-speed camera that allows highlighting phenomena and anomalies hardly detectable by conventional optical diagnostic techniques. The images, previously elaborated by neural network tools in order for clearly identifying the contours, have been analyzed in their time evolution as pseudo-chaotic variables that may have internal periodic components. In addition to the Fourier analysis, tools as Lyapunov and Hurst exponents and average Kω permitted to detect the chaos level of the signals. The use of this technique has permitted to distinguish periodic oscillations from chaotic variations and to detect those parameters that actually determine the spray behavior.
Technical Paper

Characterization of Combustion and Emissions of a Propane-Diesel Blend in a Research Diesel Engine

2016-04-05
2016-01-0810
The interest of the vehicle producers in fulfillment emission legislations without adopting after treatment systems is driving to the use of non-conventional energy sources for modern engines. A previous test campaign dealing with the use of blends of diesel and propane in a CI engine has pointed out the potential of this non-conventional fuel for diesel engines. The soft adaptation of the common rail injection system and the potential benefits, in terms of engine performances and pollutant emissions, encourage the use of propane-diesel blends if an optimization of the injection strategies is performed. In this work, the performances of a propane-diesel mixture in a research diesel engine have been investigated. The injection strategies of Euro 5 calibration have been used as reference for the development of optimized strategies. The aim of the optimization process was to ensure the same engine power output and reduce the pollutant emissions.
Journal Article

Development of Chemistry-Based Laminar Flame Speed Correlation for Part-Load SI Conditions and Validation in a GDI Research Engine

2018-04-03
2018-01-0174
The detailed study of part-load conditions is essential to characterize engine-out emissions in key operating conditions. The relevance of part-load operations is further emphasized by the recent regulations such as the new WLTP standard. Combustion development at part-load operations depends on a complex interplay between moderate turbulence levels (low engine speed and tumble ratio), low in-cylinder pressure and temperature, and stoichiometric-to-lean mixture quality (to maximize fuel efficiency). From a modelling standpoint, the reduced turbulence intensity compared to full-load operations complicates the interaction between different sub-models (e.g., reconsideration of the flamelet hypothesis adopted by common combustion models). In this article, the authors focus on chemistry-based simulations for laminar flame speed of gasoline surrogates at conditions typical of part-load operations. The analysis is an extension of a previous study focused on full-load operations.
Technical Paper

Emission Factors Evaluation in the RDE Context by a Multivariate Statistical Approach

2019-09-09
2019-24-0152
The Real Driving Emission (RDE) procedure will measure the pollutants, such as NOx, emitted by cars while driven on the road. RDE will not replace laboratory tests, such as the current WLTP but it will be added to them. RDE is complementary to the laboratory-based procedure to check the pollutant emissions level of a light-duty vehicle in real driving conditions. This means that the car will be driven on a real road according to random acceleration and deceleration patterns conditioned by traffic flow. So, the procedure will ensure that cars deliver real emissions over on-road and so the currently observed differences between emissions measured in the laboratory and those measured on road under real-world conditions, will be reduced. However, the identification of a path on the road to check the test conditions of RDE is not easy and hardly repeatable.
Technical Paper

Ethanol Addition Influence on Backfire Phenomena during Kickback in a Spark-Ignition Transparent Small Engine

2014-11-11
2014-32-0093
This paper investigates abnormal combustion during the cranking phase of spark-ignition small engines, specifically the occurrence of backfire at the release of the starter motor during kickback. The research focusses on the influence of fuel composition, mainly in terms of ethanol percentage, on backfire occurrence. Interest in this abnormal combustion is growing due to the increased use of fuels with different chemical-physical properties with respect to gasoline. Moreover, this issue will become even more topical due to the implementation of simple control and fuel supply systems on low cost-engines, which are widely used in developing countries. Experimentation was carried out in an optically accessible engine derived from a 4-stroke spark ignition engine for two-wheel vehicles. The test bench was instrumented and adapted in order to simulate the engine conditions that lead to anomalous ignition in the intake duct (backfire) during the reverse rotation of the engine (kickback).
Journal Article

Experimental Characterization of High-Pressure Impinging Sprays for CFD Modeling of GDI Engines

2011-04-12
2011-01-0685
Today, Direct-Injection systems are widely used on Spark-Ignition engines in combination with turbo-charging to reduce the fuel-consumption and the knock risks. In particular, the spread of Gasoline Direct Injection (GDI) systems is mainly related to the use of new generations of multi-hole, high-pressure injectors whose characteristics are quite different with respect to the hollow-cone, low-pressure injectors adopted in the last decade. This paper presents the results of an experimental campaign conducted on the spray produced by a GDI six-holes injector into a constant volume vessel with optical access. The vessel was filled with air at atmospheric pressure. Different operating conditions were considered for an injection pressure ranging from 3 to 20 MPa. For each operating condition, spray images were acquired by a CCD camera and then post processed to evaluate the spray penetration and cone angles.
Technical Paper

Experimental Evaluation of Fuel Consumption and Emissions in Congested Urban Traffic

1995-10-01
952401
In this paper, first results regarding measurements of fuel consumption and emissions, relative to different traffic conditions and a specific urban area, are presented. The experimental approach used for the evaluation of emissions consists in: a) recording on-road car and engine operating conditions during designed trips performed in the center of Naples (Italy) by an instrumented car, b) determining by multivariate statistical analysis driving cycles characterizing typical traffic conditions, c) measuring emissions and fuel consumption in laboratory using defined driving cycles. Fuel flow rate measurements are performed at each second, while emissions are detected along a cycle and an average value per kilometer is obtained. Operating conditions of engine during laboratory testing are related to on-road operating conditions by comparing fuel consumption and exhaust gases temperatures measurements performed on-road and in laboratory by the same device.
Technical Paper

Experimental and Numerical Characterization of Diesel Injection in Single-Cylinder Research Engine with Rate Shaping Strategy

2017-09-04
2017-24-0113
The management of multiple injections in compression ignition (CI) engines is one of the most common ways to increase engine performance by avoiding hardware modifications and after-treatment systems. Great attention is given to the profile of the injection rate since it controls the fuel delivery in the cylinder. The Injection Rate Shaping (IRS) is a technique that aims to manage the quantity of injected fuel during the injection process via a proper definition of the injection timing (injection duration and dwell time). In particular, it consists in closer and centered injection events and in a split main injection with a very small dwell time. From the experimental point of view, the performance of an IRS strategy has been studied in an optical CI engine. In particular, liquid and vapor phases of the injected fuel have been acquired via visible and infrared imaging, respectively. Injection parameters, like penetration and cone angle have been determined and analyzed.
Technical Paper

Experimental and Numerical Investigation of High-Pressure Diesel Sprays with Multiple Injections at Engine Conditions

2010-04-12
2010-01-0179
A numerical methodology to simulate the high pressure spray evolution and the fuel-air mixing in diesel engines is presented. Attention is focused on the employed atomization model, a modified version of the Huh and Gosman, on the definition of a turbulence length scale limiter and of an adaptive local mesh refinement technique to minimize the result grid dependency. All the discussed models were implemented into Lib-ICE, which is a set of libraries and solvers, specifically tailored for engine simulations, which runs under the open-source CFD technology OpenFOAM®. To provide a comprehensive assessment of the proposed methodology, the validation procedure consisted into simulating, with a unique and coherent setup of all models, two different sets of experiments: a non-evaporating diesel fuel spray in a constant-volume vessel with optical access and an evaporating non-reacting diesel fuel spray in an optical engine.
Technical Paper

Fuel Cell Propulsion System for Urban Bus Application

2005-09-11
2005-24-043
This paper presents the experimental results obtained on Fuel Cell System designed and realized in Istituto Motori and based on 16 kW PEM (Proton Exchange Membrane) stack. This activity is part of the HBUS Project, whose goal is the realization of a midi-bus for public transportation in urban areas based on fuel cell technology. This Project involves several private and public partners, comprising Istituto Motori as research institution, I2T3 (Industrial Innovation Through Technological Transfer) agency for technological innovation and project management, together with public transportation companies and vehicle component makers.
Journal Article

Functional Requirements to Exceed the 100 kW/l Milestone for High Power Density Automotive Diesel Engines

2017-09-04
2017-24-0072
The paper describes the challenges and results achieved in developing a new high-speed Diesel combustion system capable of exceeding the imaginative threshold of 100 kW/l. High-performance, state-of-art prototype components from automotive diesel technology were provided in order to set-up a single-cylinder research engine demonstrator. Key design parameters were identified in terms boost, engine speed, fuel injection pressure and injector nozzle flow rates. In this regard, an advanced piezo injection system capable of 3000 bar of maximum injection pressure was selected, coupled to a robust base engine featuring ω-shaped combustion bowl and low swirl intake ports. The matching among the above-described elements has been thoroughly examined and experimentally parameterized.
Technical Paper

Fuzzy Logic Approach to GDI Spray Characterization

2016-04-05
2016-01-0874
Advanced numerical techniques, such as fuzzy logic and neural networks have been applied in this work to digital images acquired on a mono-component fuel spray (iso-octane), in order to define, in a stochastic way, the gas-liquid interface evolution. The image is a numerical matrix and so it is possible to characterize geometrical parameters and the time evolution of the jet by using deterministic, statistical stochastic and other several kinds of approach. The algorithm used works with the fuzzy logic concept to binarize the shades gray of the pixel, depending them, by using the schlieren technique, on the gas density. Starting from a primary fixed threshold, the applied technique, can select the ‘gas’ pixel from the ‘liquid’ pixel and so it is possible define the first most probably boundary lines of the spray.
Technical Paper

GDI Spray-Wall Interaction with Numerical Characterization: Wall Temperature Influence

2015-04-14
2015-01-0917
The work analyses, from both an experimental and a numerical point of view, the impingement of a spray generated from a GDI injector on a hot solid wall. The temperature of the surface is identified as an important parameter affecting the outcome after impact. A gasoline spray issuing from a customized single-hole injector is characterized in a quiescent optically-accessible vessel as it impacts on an aluminum plate placed at 22.5 mm from the injector tip. Optical investigations are carried out at atmospheric back-pressure by a direct schlieren optical set-up using a LED as light source. A synchronized C-Mos high-speed camera captures cycle-resolved images of the evolving impact. The spatial and temporal evolution of the liquid and vapor phases are derived. They serve to define a data base to be used for the validation of a properly formulated 3D CFD model suitable to describe the impact of the fuel on the piston head in a real engine.
Technical Paper

Imaging and Vibro-Acoustic Diagnostic Techniques Comparison for a GDI Fuel Injector

2019-09-09
2019-24-0058
This work presents the results of an experimental investigation on a GDI injector, in order to analyze fuel injection process and atomization phenomenon, correlating imaging and vibro-acoustic diagnostic techniques. A single-hole, axially-disposed, 0.200 mm diameter GDI injector was used to spray commercial gasoline in a test chamber at room temperature and atmospheric backpressure. The explored injection pressures were ranged from 5.0 to 20.0 MPa. Cycle-resolved acquisitions of the spray evolution were acquired by a high-speed camera. Simultaneously, the vibro-acoustic response of the injector was evaluated. More in detail, noise data acquired by a microphone sensor were analyzed for characterizing the acoustic emission of the injection, while a spherical loudspeaker was used to excite the spray injection at a proper distance detecting possible fuel spray resonance phenomena.
Technical Paper

Improving Acoustic Performance of an Air Filter Box. TL Analysis and Device Optimization

2016-06-15
2016-01-1813
The characteristics of the intake system affect both engine power output and gas-dynamic noise emissions. The latter is particularly true in downsized VVA engines, where a less effective attenuation of the pressure waves is realized, due to the intake line de-throttling at part-load. For this engine architecture, a refined air-box design is hence requested. In this work, the Transmission Loss (TL) of the intake air-box of a commercial VVA engine is numerically computed through a 3D FEM approach. Results are compared with experimental data, showing a very good correlation. The validated model is then coupled to an external optimizer (ModeFRONTIERTM) to increase the TL parameter in a prefixed frequency range. The improvement of the acoustic attenuation is attained through a shape deformation of the inner structure of the base device, taking into account constraints related to the device installation inside the engine bay.
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