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Technical Paper

Use of Renewable Oxygenated Fuels in Order to Reduce Particle Emissions from a GDI High Performance Engine

2011-04-12
2011-01-0628
The use of oxygenated and renewable fuels is nowadays a widespread means to reduce regulated pollutant emissions produced by internal combustion engines, as well as to reduce the greenhouse impact of transportation. Besides PM, NOx and HC emissions, also the size distribution of particles emitted at the engine exhaust represent meaningful information, considering its adverse effects on the environment and human health. In this work, the results of a comprehensive investigation on the combustion characteristics and the exhaust emissions of a GDI high performance engine, fuelled with pure bio-ethanol and European gasoline, are shown. The engine is a 4-cylinder, 4-stroke, 1750 cm₃ displacement, and turbocharged. The engine was operated at different speed/load conditions and two fuel injection strategies were investigated: homogeneous charge mode and stratified charge mode.
Technical Paper

Optimization of Control Parameters for a Heavy-Duty CNG Engine via Co-Simulation Analysis

2011-04-12
2011-01-0704
Internal combustion engines for vehicle propulsion are more and more sophisticated due to increasingly restrictive environmental regulations. In case of heavy-duty engines, Compressed Natural Gas (CNG) fueling coupled with Three-Way Catalyst (TWC) and Exhaust Gas Recirculation (EGR) can help in meeting the imposed emission limits and preventing from thermal stress of engine components. To cope with the new issues associated with the more complex hardware and to improve powertrain performance and reliability and after-treatment efficiency, the engine control strategies must be reformulated. The paper focuses on the steady-state optimization of control parameters for a heavy-duty engine fueled by CNG and equipped with turbocharger and EGR. The optimization analysis is carried out to design EGR, spark timing and wastegate control, aimed at increasing fuel economy while reducing in-cylinder temperature to prevent from thermal stress of engine components.
Technical Paper

Optical Investigation of Injection and Combustion Phases of a Fouled Piezoelectric Injector in a Transparent CR Diesel Engine

2013-04-08
2013-01-1591
This study was conducted to determine the effects of the fouling process on the piezoelectric injectors in a transparent common-rail diesel engine. Piezoelectric injectors are characterized by a ceramic actuator that can dilate or retract when it receives a pulse of current. The piezo element controls a valve, which creates an imbalance in the pressure that is exerted at each end of the needle, causing the needle rising or closing. Two same model injectors were tested; one was new and the other one was fouled on a vehicle. The aim of the experimental investigation was to evaluate the performance of a new and a fouled piezoelectric injector in terms of injection and flame evolution. It was evaluated how the nozzle carbon deposits affect the injection quantity and combustion. The experimental apparatus was a single-cylinder research engine equipped with a Euro 5 multi-cylinder head. A second-generation common rail injection system and 6-hole piezoelectric injectors were used too.
Journal Article

Fuel Consumption Optimization and Noise Reduction in a Spark-Ignition Turbocharged VVA Engine

2013-04-08
2013-01-1625
Modern VVA systems offer new potentialities in improving the fuel consumption for spark-ignition engines at low and medium load, meanwhile they grant a higher volumetric efficiency and performance at high load. Recently introduced systems enhance this concept through the possibility of concurrently modifying the intake valve opening, closing and lift leading to the development of almost "throttle-less" engines. However, at very low loads, the control of the air-flow motion and the turbulence intensity inside the cylinder may require to select a proper combination of the butterfly throttling and the intake valve control, to get the highest BSFC (Brake Specific Fuel Consumption) reduction. Moreover, a low throttling, while improving the fuel consumption, may also produce an increased gas-dynamic noise at the intake mouth. In highly "downsized" engines, the intake valve control is also linked to the turbocharger operating point, which may be changed by acting on the waste-gate valve.
Technical Paper

Statistical Investigation of In Use Emissions and Fuel Consumption Measured by PEM on Different Gasoline Cars

2013-04-08
2013-01-1511
In this paper some results relative to tests performed on road with a Fiat Panda Bipower, (CNG and gasoline powered), and a New Panda Twin Air with auto Start & Stop system, are presented. Gaseous emissions are measured with Portable Emission Measurement Systems (PEMS) on two different urban routes, in terms of traffic and slope characteristics during in use experiments. PEMS testing offers an easy and efficient way to evaluate the vehicle emissions over a huge variety of conditions and provides us a direct way to study the in-use emissions of combustion engines, when you want to verify the effect of the traffic and of a particular device on fuel economy and emissions reduction. Moreover now PEMS performances are very comparable to those obtained by standard laboratory instrumentation systems.
Technical Paper

Characterization of PCCI Combustion in a Single Cylinder CI Engine Fuelled with RME and Bio-Ethanol

2013-04-08
2013-01-1672
This paper reports experiments on a single-cylinder direct-injection compression ignition engine operating in premixed charge compression ignition (PCCI) combustion mode. The engine was fuelled with pure rapeseed methyl ester (RME) and bio-ethanol. RME was injected in the combustion chamber by common rail (CR) injection system at 800 bar and bio-ethanol in the intake manifold by commercial port fuel injection system at 3.5 bar. The effects of different percentage of bio-ethanol were studied by means of both the in-cylinder heat release analysis and the high-speed UV-visible chemiluminescence visualization. The pollutant formation and exhaust emissions of the engine operating in dual fuel mode were evaluated. The increase of the bio-ethanol content improved the brake thermal efficiency slightly even if the brake fuel consumption increased. However, the choice to inject two biofuels decreases both the smoke opacity and NOx concentration.
Journal Article

CFD Gas-Dynamic Noise Prediction of a VVA Engine Intake System

2013-05-13
2013-01-1884
Modern VVA systems offer new potentialities in improving fuel consumption for spark-ignition engines at low and medium load, meanwhile they grant a higher volumetric efficiency and performance at high load. Recently introduced systems enhance this concept through the possibility of modifying the intake valve opening, closing and lift, leading to the development of almost ‘throttle-less’ engines. However, at low loads, the absence of throttling, while improving the fuel consumption, also produces an increased gas-dynamic noise at the intake mouth. Wave propagation inside the intake system is in fact no longer absorbed by the throttle valve and directly impact the radiated noise. In the paper, 1D and 3D simulations of the gas-dynamic noise radiated by a production VVA engine are performed at full load and in two part-load conditions. Both models are firstly validated at full load, through comparisons with experimental data.
Technical Paper

An experimental investigation on combustion and engine performance and emissions of a methane-gasoline dual-fuel optical engine

2014-04-01
2014-01-1329
The use of methane as supplement to liquid fuel is one of the solution proposed for the reduction of the internal combustion engine pollutant emissions. Its intrinsic properties as the high knocking resistance and the low carbon content makes methane the most promising clean fuel. The dual fuel combustion mode allows improving the methane combustion acting mainly on the methane slow burning velocity and allowing lean burn combustion mode. An experimental investigation was carried out to study the methane-gasoline dual fuel combustion. Methane was injected in combustion chamber (DI fuel) while gasoline was injected in the intake manifold (PFI fuel). The measurements were carried out in an optically accessible small single-cylinder four-stroke engine. It was equipped with the cylinder head of a commercial 250 cc motorcycles engine representative of the most popular two-wheel vehicles in Europe.
Journal Article

UV-visible Optical Characterization of the Early Combustion Stage in a DISI Engine Fuelled with Butanol-Gasoline Blend

2013-10-14
2013-01-2638
Detailed experimental information on the early stages of spark ignition process represent a substantial part for guiding the development of engines with higher efficiencies and reduced pollutant emissions. Flame kernel formation influences strongly combustion development inside the cylinder, especially for a direct injection spark ignition engine. This study presents the analysis of the evolution of spark-ignited flame kernels with detailed view upon cycle-to-cycle variations. Experiments are performed in a SI optical engine equipped with the cylinder head and injection system of a commercial turbocharged engine. Blend of commercial gasoline and butanol (40% by volume) is tested at stoichiometric and lean mixture conditions. Experiments are carried out at 2000 rpm through conventional tests (based on in-cylinder pressure measurements and exhaust emission analysis) and through optical diagnostics. In particular, UV-visible digital imaging and natural emission spectroscopy are applied.
Journal Article

Experimental Characterization of Diesel Combustion Using Glycerol Derived Ethers Mixtures

2013-09-08
2013-24-0104
In this paper the characteristics of a mixture of glycerol-based ethers usable in a compression ignition engine are investigated, in terms of efficiency and emissions. Alternative pathways for the energetic exploitation of biodiesel derived glycerol became of increasing interest as the biodiesel production was increased worldwide. Because of its detrimental physical and chemical properties, raw glycerol is hardly usable in conventional internal combustion engines (ICE). However, etherification of glycerol with tert-butyl alcohol and isobutylene allows obtaining a mixture mainly composed of higher glycerol ethers (GEM) suitable for compression ignition engines. Thus, the aim of this research study was to test a mixture of mono-, di- and tri-tert-butyl ethers of glycerol in blend with a commercial diesel fuel in a compression ignition engine, evaluating the fuel efficiency and the impact on the pollutant emissions.
Technical Paper

Experimental Analysis of a Natural Gas Fueled Engine and 1-D Simulation of VVT and VVA Strategies

2013-09-08
2013-24-0111
The paper deals with experimental testing of a natural gas fueled engine. Break Specific fuel Consumption (BSFC), Average Mass Flow Rate, Instantaneous Cylinder Pressure and some wall temperatures have been measured at some full and part load operating conditions. The results of this experimental activity, still in progress, have been used to calibrate a 1D-flow engine's model. Then the effects of some VVA strategies have been theoretically studied through the validated model. With the aim of maximizing the full load engine's torque, a genetic algorithm was used to calculate the optimized intake and exhaust valves timing angles. Various VVA strategies were compared at part-load in order to reduce brake specific fuel consumption.
Technical Paper

Towards On-Line Prediction of the In-Cylinder Pressure in Diesel Engines from Engine Vibration Using Artificial Neural Networks

2013-09-08
2013-24-0137
This study aims at building efficient and robust artificial neural networks (ANN) able to reconstruct the in-cylinder pressure of Diesel engines and to identify engine conditions starting from the signal of a low-cost accelerometer placed on the engine block. The accelerometer is a perfect non-intrusive replacement for expensive probes and is prospectively suitable for production vehicles. In this view, the artificial neural network is meant to be efficient in terms of response time, i.e. fast enough for on-line use. In addition, robustness is sought in order to provide flexibility in terms of operation parameters. Here we consider a feed-forward neural network based on radial basis functions (RBF) for signal reconstruction, and a feed-forward multi-layer perceptron network with tan-sigmoid transfer function for signal classification. The networks are trained using measurements from a three-cylinder real engine for various operating conditions.
Technical Paper

Coking Effect of Different FN Nozzles on Injection and Combustion in an Optically Accessible Diesel Engine

2013-09-08
2013-24-0039
Interest on the issue of diesel injector nozzle deposits is rising in the last years due to its effects on engine performance. The alteration of nozzles geometry can cause a difference in fuel mass flow and influence smoke emission. Investigation on the effects of nozzle coking in a diesel injector has been the topic of this paper. The experiments have been carried out in a single cylinder optical engine operating in premixed mode. The head of a Euro 5 production engine has been mounted on an elongated cylinder and the production CR injection system has been used. A sapphire window has been set in the piston head in order to have visible access to phenomena occurring in the combustion chamber. Three injectors with decreasing flow number (FN) have been tested. Engine has been fed with commercial diesel fuel. High spatial and temporal resolution camera has been used for the acquisition of in-cylinder injection and combustion images.
Technical Paper

Dynamic Analysis of Emission Spectra in HCCI Combustion

2013-09-08
2013-24-0042
This work reports on the application of spectroscopic measurements coupled with data processing techniques in order to study, in terms of spectral emissions, the dynamic of the HCCI (Homogeneous charge compression ignition) combustion that occurs inside the combustion chamber of an optically accessible direct injection Diesel engine. A pre-processing of the recorded spectra is required for a correct analysis. The procedure of pre-processing consists of two main steps, that is: noise filtering with a technique based on the POD (Proper Orthogonal Decomposition); estimate and subtraction of the baseline. The analysis of the dynamics of the recorded spectra was carried out by the estimates of the synchronous and asynchronous 2D correlation spectra.
Technical Paper

Experimental Investigation of a Methane-Gasoline Dual-Fuel Combustion in a Small Displacement Optical Engine

2013-09-08
2013-24-0046
In this paper the methane-gasoline dual fuel combustion was investigated. Gasoline was injected in the intake manifold (PFI fuel), while methane was injected in the combustion chamber (DI fuel), in order to reproduce a stratified combustion. The combustion process and the related engine performance and pollutant emissions were analyzed. The measurements were carried out in an optically accessible small single-cylinder four-stroke engine. It was equipped with the cylinder head of a commercial 250 cc engine representative of the most popular two-wheel vehicles in Europe. Optical measurements were performed to analyze the combustion process with high spatial and temporal resolution. In particular, optical techniques based on 2D-digital imaging were used to follow the flame front propagation and the soot and temperature concentration in the combustion chamber.
Journal Article

Assessment of a New Quasi-Dimensional Multizone Combustion Model for the Spray and Soot Formation Analysis in an Optical Single Cylinder Diesel Engine

2013-09-08
2013-24-0044
An innovative quasi-dimensional multizone combustion model for the spray formation, combustion and emission formation analysis in DI diesel engines was assessed and applied to an optical single cylinder engine. The model, which has been recently presented by the authors, integrates a predictive non stationary 1D spray model developed by the Sandia National Laboratory, with a diagnostic multizone thermodynamic model. The 1D spray model is capable of predicting the equivalence ratio of the fuel during the mixing process, as well as the spray penetration. The multizone approach is based on the application of the mass and energy conservation laws to several homogeneous zones identified in the combustion chamber. A specific submodel is also implemented to simulate the dilution of the burned gases. Soot formation is modeled by an expression which derives from Kitamura et al.'s results, in which an explicit dependence on the local equivalence ratio is considered.
Technical Paper

Fuel Injection Effect on In-cylinder Formation and Exhaust Emission of Particulate from a 4-Stroke Engine for 2-Wheel Vehicles

2010-04-12
2010-01-0354
The small engine for two-wheel vehicles has generally high possibility to be optimized at low speeds and high loads. In these conditions fuel consumption and pollutants emission should be reduced maintaining the performance levels. This optimization can be realized only improving the basic knowledge of the thermo-fluid dynamic phenomena occurring during the combustion process. It is known that, during the fuel injection phase in PFI SI engines, thin films of liquid fuel can form on the valves surface and on the cylinder walls. Successively the fuel films interact with the intake manifold and the combustion chamber gas flow. During the normal combustion process, it is possible to achieve gas temperature and mixture strength conditions that lead to fuel film ignition. This phenomenon can create diffusion-controlled flames that can persist well after the normal combustion event. These flames induce the emission of soot and unburned hydrocarbons.
Technical Paper

High Spatial Resolution Visualization and Spectroscopic Investigation of the Flame Front Propagation in the Combustion Chamber of a Scooter Engine

2010-04-12
2010-01-0351
The match between the increasing performance demands and stringent requirements of emissions and fuel consumption reduction needs a strong evolution in the 2-wheel vehicle technology. In particular many steps forward should be taken for the optimization of modern small motorcycle and scooter at low engine speeds and low temperature start. To this aim, the detailed understandings of thermal and fluid-dynamic phenomena that occur in the combustion chamber are fundamental. In this work, experimental activities were realized in the combustion chamber of a single-cylinder 4-stroke optical engine. The engine was equipped with a four-valve head of a commercial scooter engine. High spatial resolution imaging was used to follow the flame kernel growth and flame front propagation. Moreover, the effects of an abnormal combustion due to firing of fuel deposition near the intake valves and on the piston surface were investigated.
Technical Paper

Modeling Pressure Oscillations under Knocking Conditions: A Partial Differential Wave Equation Approach

2010-10-25
2010-01-2185
In this work the authors present a model to simulate the in-cylinder pressure oscillations due to knock. Pressure oscillations are predicted by the explicit integration of a Partial Differential Wave Equation (PDWE) similar, in its structure, to the so-called “Equation of Telegraphy”. This equation differs mainly from the classical wave formulation for the presence of a loss term. The general solution of such equation is obtained by the Fourier method of variables separation. The integration space is a cylindrical acoustic cavity whose volume is evaluated at the knock onset. The integration constants are derived from the boundary and initial conditions. A novel approach is proposed to derive the initial condition for the derivative of the oscillating component of pressure. It descends, conceptually, from the integration of the linearized relation between the derivative of pressure versus time and the expansion velocity of burned gas.
Technical Paper

Idle Speed Control of GDI-SI Engines via ECU-1D Engine Co-Simulation

2010-10-25
2010-01-2220
Idle Speed Control plays a crucial role to reduce fuel consumption that turns in both a direct economic benefit for customers and CO\d reduction particularly important to tackle the progressive global environmental warming. Typically, control strategies available in the automotive literature solve the idle speed control problem acting both on the throttle position and the spark advance, while the Air-Fuel Ratio (AFR), that strongly affects the indicated engine torque, is kept at the stoichiometric value for the sake of emission reduction. Gasoline Direct Injection (GDI) engines, working lean and equipped with proper mechanisms to reduce NOx emissions, overcome this limitation allowing the AFR to be used for the idle speed regulation.
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