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Technical Paper

Chemical and Physical Characterization of Organic Particulate Matter from Last Generation Exhaust Aftertreatment System of Medium Duty Diesel Engine

2019-09-09
2019-24-0053
Particulate Matter from Euro 6 Medium Duty diesel engine was analyzed from engine-out, downstream of particulate filter (DPF), and up to the exit of a selective catalytic reactor (SCR) to characterize its chemical and physical nature. Particular attention was devoted to the analysis of particles down to 23 nm. An array of chemical, physical and spectroscopic techniques (Gas chromatography coupled with mass spectrometry (GC-MS), mobility analyzer, UV-visible absorption and fluorescence spectroscopy) was applied for characterizing the organic particulate matter (PM, constituted of polycyclic aromatic hydrocarbons (PAH), heavy aromatic compounds, soot) in the exhaust. The engine was operated at “full-load” (100% of the total power, representing the best performance of the engine operation) condition, and at different engine speeds. Results showed that the DPF efficiency was greater than 96% in the reduction of the sub 23 nm particles across the speeds range.
Technical Paper

1D Modeling of Alternative Fuels Spray in a Compression Ignition Engine using Injection Rate Shaping Strategy

2019-09-09
2019-24-0132
The Injection Rate Shaping consists in a novel injection strategy to control air-fuel mixing quality via a suitable variation of injection timing that affects the injection rate profile. This strategy has already provided to be useful to increase combustion efficiency and reduce pollutant emissions in the modern compression ignition engines fed with fossil Diesel fuel. But today’s, the ever more rigorous emission targets are enhancing a search for alternative fuels and/or new blends to replace conventional ones, leading in turn a change in the air-fuel mixture formation. In this work a 1D model aims to investigate the combined effects of both Injection Rate Shaping and alternative fuels on the air-fuel mixture formation in a compression ignition engine. In a first step, a ready-made model for conventional injection strategies has been set up for the Injection Rate Shaping.
Technical Paper

Temperature Measurements of the Piston surface in a Research Compression Ignition Engine in Transient Conditions for 1d Model of Heat Transfer

2019-09-09
2019-24-0182
Analysis of heat losses in internal combustion engines (ICEs) is fundamental to evaluate and improve the engine efficiency. Detailed and reliable heat transfer models are required for more complex 1d-3d combustion models. At the same time, the thermal status of engine components, as pistons, is needed for an efficient design. Measurements of piston temperature during ICEs operation represent a precious and challenging result to get for the aforementioned purposes. In previous works, the authors, first, evaluated and, then, measured the temperature of the optical window in a research compression ignition engine via thermal imaging and thermocouple installation, respectively. The tests concerned steady state and transient conditions.
Technical Paper

A Mixing Timescale Model for PDF Simulations of LTC Combustion Process in Internal Combustion Engines

2019-09-09
2019-24-0113
Transported probality density function (PDF) methods are currently being pursued as a viable approach to model the effects of turbulent mixing and mixture stratification, especially for new alternative combustion modes as for example Homogeneous Charge Compression ignition (HCCI) which is one of the advanced LTC concepts. Recently, they have been applied to simple engine configurations to demonstrate the importance of accurate accouting for turbulence/chemistry interactions. PDF methods can explicity account for the turbulent fluctuations in species composition and temperature relative to mean value. The choice of the mixing model is an important aspect of PDF approach. Different mixing models can be found in the literature, the most popular is the IEM model (Interaction by Exchange with the Mean). This model is very similar to the LMSE model (Linear Mean Square Estimation).
Technical Paper

Analysis of Dual Fuel Combustion in Single Cylinder Research Engine Fueled with Methane and Diesel by IR Diagnostics

2019-04-02
2019-01-1165
In the present study, dual fuel mode is investigated in a single cylinder optical compression ignition (CI) research engine. Methane is injected in the intake manifold while the diesel is delivered via the standard injector directly into the engine. The aim is to study by non-intrusive diagnostics the effect of increasing methane concentration at constant injected diesel amount during the combustion evolution from start of combustion. IR imaging is applied in cycle resolved mode. Three filters are adopted to detect from injection to combustion phase with high spatial and temporal resolution: OD1.45 (3-5.5 μm), band pass 3.3 μm (hydrocarbons) and band pass 4.2 μm (CO2). Using the band pass IR imaging qualitative information about fuel-vapor distribution and ignition locations during low and high temperature combustion have been provided.
Technical Paper

Assessment of the New Features of a Prototype High-Pressure “Hollow Cone Spray” Diesel Injector by Means of Engine Performance Characterization and Spray Visualization

2018-09-10
2018-01-1697
The application of more efficient compression ignition combustion concepts requires advancement in terms of fuel injection technologies. The injector nozzle is the most critical component of the whole injection system for its impact on the combustion process. It is characterized by the number of holes, diameter, internal shape, and opening angle. The reduction of the nozzle hole diameter seems the simplest way to promote the atomization process but the number of holes must be increased to keep constant the injected fuel mass. This logic has been applied to the development of a new generation of injectors. First, the tendency to increase the nozzle number and to reduce the diameter has led to the replacement of the nozzle with a circular plate. The vertical movement of the needle generates an annulus area for the fuel delivery on 360 degrees, so controlling the atomization as a function of the vertical plate position.
Technical Paper

CFD Analysis of the Combustion Process in Dual-Fuel Diesel Engine

2018-04-03
2018-01-0257
Dual-fuel technology has the potential to offer significant improvements in the emissions of carbon dioxide from light-duty compression ignition engines. The dual-fuel (diesel/natural gas) concept represents a possible solution to reduce emissions from diesel engines by using natural gas (methane) as an alternative fuel. Methane was injected in the intake manifold while the diesel oil was injected directly into the engine. The present work describes the results of a numerical study on combustion process of a common rail diesel engine supplied with natural gas and diesel oil. In particular, the aim is to study the effect of increasing methane concentration at constant injected diesel amount on both pollutant emissions and combustion evolution. The study of dual-fuel engines that is carried out in this paper aims at the evaluation of the CFD potential, by a 3-dimensional code, to predict the main features of this technology.
Technical Paper

Temperature Measurements of the Piston Optical Window in a Research Compression Ignition Engine via Thermography and Templugs

2018-04-03
2018-01-0083
Internal combustion engines are characterized by high pressure and thermal loads on pistons and in cylinders. The heat generated by the combustion process is dissipated by means of water and oil cooling systems. For the best design and optimization of the engine components it is necessary to know the components temperature in order to estimate the thermal flows. The purpose of this work is to measure the piston sapphire window temperature in a research optically accessible engine by combining two different techniques: measurements with templugs and with thermography. The method is very simple and can provide a reliable value of temperature within a small interval. It fits well for applications inside the engine because of its low technical level requirements. It consists of application of temperature sensitive stickers on the target component that makes it a very robust method, not affected by piston movement.
Technical Paper

Analysis of a Prototype High-Pressure “Hollow Cone Spray” Diesel Injector Performance in Optical and Metal Research Engines

2017-09-04
2017-24-0073
Technologies for direct injection of fuel in compression ignition engines are in continuous development. One of the most investigated components of this system is the injector; in particular, main attention is given to the nozzle characteristics as hole diameter, number, internal shape, and opening angle. The reduction of nozzle hole diameter seems the simplest way to increase the average fuel velocity and to promote the atomization process. On the other hand, the number of holes must increase to keep the desired mass flow rate. On this basis, a new logic has been applied for the development of the next generation of injectors. The tendency to increase the nozzle number and to reduce the diameter has led to the replacement of the nozzle with a circular plate that moves vertically. The plate motion allows to obtain an annulus area for the delivery of the fuel on 360 degrees; while the plate lift permits to vary the atomization level of the spray.
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.
Journal Article

Real Time Prediction of Particle Sizing at the Exhaust of a Diesel Engine by Using a Neural Network Model

2017-09-04
2017-24-0051
In order to meet the increasingly strict emission regulations, several solutions for NOx and PM emissions reduction have been studied. Exhaust gas recirculation (EGR) technology has become one of the more used methods to accomplish the NOx emissions reduction. However, actual control strategies do not consider, in the definition of optimal EGR, its effect on particle size and density. These latter have a great importance both for the optimal functioning of after-treatment systems, but also for the adverse effects that small particles have on human health. Epidemiological studies, in fact, highlighted that the toxicity of particulate particles increases as the particle size decreases. The aim of this paper is to present a Neural Network model able to provide real time information about the characteristics of exhaust particles emitted by a Diesel engine.
Technical Paper

Performance, Gaseous and Particle Emissions of a Small Compression Ignition Engine Operating in Diesel/Methane Dual Fuel Mode

2016-04-05
2016-01-0771
This paper deals with the combustion behavior and exhaust emissions of a small compression ignition engine modified to operate in diesel/methane dual fuel mode. The engine is a three-cylinder, 1028 cm3 of displacement, equipped with a common rail injection system. The engine is provided with the production diesel oxidation catalyst. Intake manifold was modified in order to set up a gas injector managed by an external control unit. Experiments were carried out at different engine speeds and loads. For each engine operating condition, the majority of the total load was supplied by methane while a small percentage of the load was realized using diesel fuel; the latter was necessary to ignite the premixed charge of gaseous fuel. Thermodynamical analysis of the combustion phase was performed by in-cylinder pressure signal. Gas emissions and particulate matter were measured at the exhaust by commercial instruments.
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.
Technical Paper

Investigation of the Injection Process in a Research CR Diesel Engine using Different Blends of Propane-Diesel Fuel

2015-09-06
2015-24-2477
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 of usinf 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 the injection process for different liquid preformed blends of propane-diesel fuel in an optically accessible Common Rail diesel engine. Slight modifications of the injection system were required in order to operate with a blend of propane-diesel fuel. Pure diesel fuel and two propane-diesel mixtures at different mass ratios were tested (20% and 40% in mass of propane named P20 and P40). First, injection in air at ambient temperature and atmospheric pressure were performed to verify the functionality of the modified Common Rail injection system.
Technical Paper

Combustion Analysis of Dual Fuel Operation in Single Cylinder Research Engine Fuelled with Methane and Diesel

2015-09-06
2015-24-2461
In the present activity, dual fuel operation was investigated in a single cylinder research engine. Methane was injected in the intake manifold while the diesel was delivered via the standard injector directly into the engine. The aim is to study the effect of increasing methane concentration at constant injected diesel amount on both pollutant emissions and combustion evolution in an optically accessible engine. Emissions are in line with those previously published by other authors, it is noted no PM and constant NOx emissions. Moreover, a decrease of the brake specific CO emissions and an increase of the brake specific THC for the operating condition with the highest premixed ratio was detected. THC was mainly constituted by methane unburned hydrocarbons. Combustion resulted more or less stable. Moreover, via both UV-VIS spectroscopy and digital imaging, the spatial distribution of several species involved in the combustion process was analyzed.
Technical Paper

Characterization of Combustion and Emissions in Light-Duty Diesel Engines Using High-Glycerol-Ethers/Diesel Blends

2015-09-06
2015-24-2445
In this paper, a detailed analysis of combustion and emissions is carried out on both metal and optical light duty diesel engines equipped with up-to-date combustion architecture. Both engines were fed with glycerol ethers mixture (GEM) in blend (10% and 20% v/v) within a commercial diesel fuel. The engines ran 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 blends and the diesel fuel and demonstrate benefits mainly in terms of soot production. The exhaust particles diameters of diesel/GEM blends 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.
Journal Article

Spray and Soot Formation Analysis by Means of a Quasi-Dimensional Multizone Model in a Single Cylinder Diesel Engine under Euro 4 Operating Conditions

2015-09-06
2015-24-2416
An investigation has been carried out on the spray penetration and soot formation processes in a research diesel engine by means of a quasi-dimensional multizone combustion model. The model integrates a predictive non stationary 1D spray model developed by the Sandia National Laboratory, with a diagnostic multizone thermodynamic model, and is capable of predicting the spray formation, combustion and soot formation processes in the combustion chamber. The multizone model was used to analyze three operating conditions, i.e., a zero load point (BMEP = 0 bar at 1000 rpm), a medium load point (BMEP = 5 bar at 2000 rpm) and a medium-high load point (BMEP = 10 bar at 2000 rpm). These conditions were experimentally tested in an optical single cylinder engine with the combustion system configuration of a 2.0L Euro4 GM diesel engine for passenger car applications.
Journal Article

Using 2d Infrared Imaging for the Analysis of Non-Conventional Fuels Combustion in a Diesel Engine

2015-04-14
2015-01-1646
The common realization of the necessity to reduce the use of mineral sources is promoting the use of alternative fuels. Big efforts are being made to replace petroleum derivatives in the internal combustion engines (ICEs). For this purpose it is mandatory to evaluate the behavior of non-conventional fuels in the ICEs. The optical diagnostics have proven to be a powerful tool to analyze the processes that take place inside the engine. In particular, 2d imaging in the infrared range can reveal new details about the effect of the fuel properties since this technique is still not very common. In this work, a comparison between commercial diesel fuel and two non-conventional fuels has been made in an optically accessible diesel engine. The non-conventional fuels are: the first generation biofuel Rapeseed Methyl Ester (RME) and an experimental blend of diesel and a fuel with high glycerol content (HG).
Technical Paper

Engine Performance and Emissions of a Small Diesel Engine Fueled with Various Diesel/RME Blends

2014-11-11
2014-32-0135
The present paper describes the results of an experimental activity performed on a small diesel engine for quadricycles, a category of vehicles that is spreading in Europe and is recently spreading over Indian countries. The engine is a prototype three-cylinder with 1000 cc of displacement and it is equipped with a direct common-rail injection system that reaches a maximum pressure of 1400 bar. The engine was designed to comply with Euro 4 emission standard that is a future regulation for quadricycles. It is worth underlining that the engine can meet emission limits just with EGR system and a DOC, without DPF. Various diesel/RME blends were tested; pure diesel and biodiesel fuels were also used. The investigation was carried out at the engine speeds of 1400, 2000 and 3400 rpm and full load. Combustion characteristics of both blended and pure RME were analyzed by means of in-cylinder pressure and heat released histories.
Technical Paper

Endoscopic Investigation of Combustion Process in a Small Compression Ignition Engine Fuelled with Rapeseed Methyl Ester

2014-10-13
2014-01-2649
The aim of this study is to investigate the combustion process and pollutant formation in a small compression ignition engine. The engine is a prototype for quadricycles. It was designed to comply with Euro 4 emission standard that is a future regulation for this type of vehicles. Two optical accesses for endoscopes were realized in the first cylinder to investigate the combustion process. Two-color pyrometry method was applied to combustion images in order to detect the flame temperature and the soot concentration. The engine ran with a biodiesel, the rapeseed methyl ester, and a conventional diesel fuel. Operating conditions at the engine speed of 2000 rpm at full and medium load were tested. NOx emissions were measured at exhaust. A smoke meter was used to determine the particulate matter concentration. The sizing and the counting of the particles were performed by means of an engine exhaust particle sizer spectrometer.
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