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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 nowadays, 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 of spray injection 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

Axial Flow Turbine Concept for Conventional and e-Turbocharging

2019-09-09
2019-24-0185
Engine downsizing has established itself as one of the most successful strategies to reduce fuel consumption and pollutant emissions in the automotive field. To this regard, a major role is played by turbocharging, which allows an increase in engine power density, so reducing engine size and weight. However, the need for turbocharging imposes some issues to be solved. In the attempt of mitigating turbo lag and poor low-end torque, many solutions have been presented in the open literature so far, such as: low inertia turbine wheels and variable geometry turbines; or even more complex concepts such as twin turbo and electrically assisted turbochargers. None of them appears as definitive, though. As a possible way of reducing turbine rotor inertia, and so the turbo lag, also the change of turbine layout has been investigated, and it revealed itself to be a viable option, leading to the use of mixed-flow turbines.
Technical Paper

Temperature Measurements of the Piston Optical Window in a Research Compression Ignition Engine to Set-Up a 1d Model of Heat Transfer in Transient Conditions

2019-09-09
2019-24-0182
The analysis of heat losses in internal combustion engines (ICEs) is fundamental to evaluate and to improve 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, like pistons, is needed for an efficient design. Measurements of piston temperature during ICEs operation represent an important and challenging result to get for the aforementioned purposes. In the present work, temperature measurements collected at different engine speeds and loads, both in motored and fired modes, have been performed and used to set-up a theoretical correlation and 1d model of heat transfer through the optical window of the piston. The in-cylinder gas and external ambient temperature, together with the thermodynamic and material properties are given. The model has been first calibrated in some selected operating conditions and then validated in the remaining.
Technical Paper

Integrated CFD-Experimental Methodology for the Study of a Dual Fuel Heavy Duty Diesel Engine

2019-09-09
2019-24-0093
This paper deals with the experimental and numerical investigation of a 2.0 litre single cylinder Heavy Duty Diesel Engine fuelled by natural gas and diesel oil in Dual Fuel mode. Due to the gaseous nature of the main fuel and to the high compression ratio of the diesel engine, reduced emissions can be obtained. An experimental study has been carried out at three different load level (25%, 50% and 75% of full engine load). Basing on experimental data, the authors recreated a 45° mesh sector of the engine cylinder and performed CFD simulations for the cases at 50% and 75% load levels. Numerical simulations were carried out on the 3D code Ansys FORTE. The aim of this work is to study combustion phenomena and, in particular, the interaction between natural gas and diesel oil, respectively represented by methane and n-dodecane. A reduced kinetic scheme for methane auto-ignition was implemented while for n-dodecane two set of reactions were utilised.
Technical Paper

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

2019-09-09
2019-24-0113
Transported probability 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 low temperature combustion (LTC) concepts. Recently, they have been applied to simple engine configurations to demonstrate the importance of accurate accounting for turbulence/chemistry interactions. PDF methods can explicitly 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

Chemical and Physical Characteristics of Organic Particulate Matter from Exhaust After-Treatment System of Euro 6 Diesel Engine Operating at Full Load

2019-09-09
2019-24-0053
The current legislation does not take into account the limitation of sub 23 nm particles from engine. Nevertheless, the Common Rail Diesel engine emits a large number of nanoparticle, solid and volatiles, that are very dangerous for human health. In this contest, the challenge of the “dieper EU project” is to apply advanced technologies for exhaust after-treatment to existing diesel engines and to optimize the characteristics of a new generation of engines with regards to emissions, fuel consumption and drivability. Aim of the present paper is to provide useful information for the development of the after-treatment system that will have to fulfill Euro6 further steps. In order to characterize the chemical and physical nature of Particulate Matter emitted from Euro 6b Medium Duty diesel engine, the pollutants were collected and analyzed: from engine-out, downstream of the particulate filter (DPF), and at the exit of a selective catalytic reactor (SCR).
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

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

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

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

Performance Improvement and Emission Control of a Dual Fuel Operated Diesel Engine

2017-09-04
2017-24-0066
The present study deals with the simulation of a Diesel engine fuelled by natural gas/diesel in dual fuel mode to optimize the engine behaviour in terms of performance and emissions. In dual fuel mode, the natural gas is introduced into the engine’s intake system. Near the end of the compression stroke, diesel fuel is injected and ignites, causing the natural gas to burn. The engine itself is virtually unaltered, but for the addition of a gas injection system. The CO2 emissions are considerably reduced because of the lower carbon content of the fuel. Furthermore, potential advantages of dual-fuel engines include diesel-like efficiency and brake mean effective pressure with much lower emissions of oxides of nitrogen and particulate matter. In previous papers, the authors have presented some CFD results obtained by two 3D codes by varying the diesel/NG ratio and the diesel pilot injection timing at different loads.
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

Conceptual Design of a Variable Geometry, Axial Flow Turbocharger Turbine

2017-09-04
2017-24-0163
The modern automotive industry is under strict regulations to reduce emissions to comply with the Kyoto Protocol, a universally acknowledged treaty aiming at reducing exhaust gas emissions. In order to achieve the required future emission reduction targets, further developments on gasoline engines are required. One of the main methods to achieve this goal is the application of engine downsizing. Turbocharging is a cost-effective method of downsizing an engine whilst reducing exhaust gas emissions, reducing fuel consumption and maintaining prior performance outputs. For these reasons, the turbocharging is becoming the most widely adopted technology in the automotive markets. In 2012, 32% of passenger and commercial vehicles sold had a turbocharger installed, and is predicted to be 40% of 2017 [1]. Even if the engine turbocharging is a widespread technology, there are still drawbacks present in current turbocharging systems.
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

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

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

Dual Fuel Diesel Engine at Variable Operating Conditions: A Numerical and Experimental Study

2015-09-06
2015-24-2411
The dual-fuel (diesel/natural gas, NG) concept represents a solution to reduce emissions from diesel engines by using natural gas as an alternative fuel. As well known, the dual-fuel technology has the potential to offer significant improvements in the emissions of carbon dioxide from light-duty compression ignition engines. A further important requirement of the DF operation in automotive engines is a satisfactory response in a wide range of load levels. In particular, the part-load levels could present more challenging conditions for an efficient combustion development, due to the poor fuel/air ratio. Basing on the above assumptions, the authors discuss in this article the results of a combined numerical and experimental study on the effect of different injection timings on performance and pollutant fractions of a common rail diesel engine supplied with natural gas and diesel oil.
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.
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.
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