Arturo de Risi

The two-stroke crosshead diesel engines, nowadays moving the majority of merchant vessels, have lubrication systems which significantly contribute to their overall emissions, since they work on total loss basis: a relevant fraction of lubricant enters the exhaust duct, increasing total exhaust emissions. This paper demonstrates that a viable solution to reduce lubrication system related emissions can be found in the application of a new common rail type ( CR) lubrication system. Particularly, in the first part of this study, a common rail injector was simulated and numerically optimized by means of AMESim. The main parameters influencing lube oil injected mass were identified, with the purpose to design a highly time responsive injector. Therefore, a CR injector was realized and experimentally characterized by means of a dedicated test cell, defining the lube oil injection map over the entire engine load range. Finally, full scale engine tests allowed to evaluate oil loss at exhaust...

In this study, several experimental investigations on the effects of nanofluids on the convective heat transfer coefficient in laminar and turbulent conditions were analyzed. The aim of this work is to provide an overview of the thermal performance achieved with the use of nanofluids in various experimental systems. This review covers both forced and natural convection phenomena, with a focus on the different experimental setups used to carry out the experimental campaigns. When possible, a comparison was performed between different experimental campaigns to provide an analysis of the possible common points and differences. A significant increase in the convective heat transfer coefficient was found by using nanofluids instead of traditional heat transfer fluids, in general, even with big data dispersion from one case to another that depended on boundary conditions and the particular experimental setup. In particular, a general trend shows that once a critic value of the Reynolds nu...

Nanofluids have great potential to improve the heat transfer properties of liquids, as demonstrated by recent studies. This paper presents a novel idea of utilizing nanofluid. It analyzes the performance of a HVAC (Heating Ventilation Air Conditioning) system using a high-performance heat transfer fluid (water-glycol nanofluid with nanoparticles of Al2O3), in the university campus of Lecce, Italy. The work describes the dynamic model of the building and its heating and cooling system, realized through the simulation software TRNSYS 17. The use of heat transfer fluid inseminated by nanoparticles in a real HVAC system is an innovative application that is difficult to find in the scientific literature so far. This work focuses on comparing the efficiency of the system working with a traditional water-glycol mixture with the same system that uses Al2O3-nanofluid. The results obtained by means of the dynamic simulations have confirmed what theoretically assumed, indicating the working co...

ABSTRACT In this study, a modified flat panel solar thermal collector was built and thermal efficiency was measured with two heat transfer fluids: distillated water and Al2O3-distillated water based nanofluid at high concentration (3.0%) volume fraction of solid phase. In this work for the first time nanofluid with high nanoparticle concentration has been used thanks to a modified solar thermal collector, based on patent WO2011138752 A1, which consists in bottom and top headers properly shaped in order to reduce sedimentation of clusters of nanoparticles. Thermal efficiency has been measured through an experimental setup, according to EN 12975-2 standard. Experimental results showed that an increase of thermal efficiency up to 11.7% compared to that measured with water has been obtained by using nanofluid. Besides effect of nanofluid on thermal efficiency is greater at high temperatures.

Abstract: An innovative methodology aimed at reducing emissions and improving fuel consumption has been developed for the design of internal combustion engines. The method allows the design of new combustion chambers by means of a fully automated procedure based on ...

The present work addresses the possibility to correctly simulate Partial Homogeneous Charge Compression Ignition (PHCCI) combustion, obtained by the application of EGR up to 60% without using detailed kinetic models. In particular, the laminar and turbulent time characteristic model has been analyzed and improved. The study illustrates the prediction capabilities that can be achieved with such an approach. The paper reports the results obtained from the simulation of a single cylinder research engine and a four-cylinder diesel engine to verify the validity of the proposed method independently of engine geometry and configuration. All numerical results are compared with experimental pressure traces and rates of heat release, as well as with NOx and soot emissions over a wide range of operating conditions. With the modified characteristic time model, realistic simulations of engine combustion up to EGR values of about 60% have been obtained for both engines. In particular, simulations...

By applying electrostatic charge to the fuel from a fuel injector, electrostatic assistance of fuel injector sprays is one possible means of improving the atomization and fuel distribution in an engine. A gasoline injector was modified to induce electrostatic charge on the fuel spray and particle imaging velocimetry (PIV) measurements of the spray velocity field were performed. These results were complemented by high speed video of combustion of electrostatically charged ethanol blended gasoline droplets suspended from a capillary. Ethanol blended gasoline was selected as a fuel because of its widespread use in automotive gasoline engines. The experiment took place at room temperature and pressure and under normal gravity and a spark ignition system was utilized. Non-charged droplets were burned under otherwise identical conditions to compare to the combustion of the charged droplets, and images of the droplets prior to combustion were taken to provide a measure of droplet diameter....

A car Diesel engine has been transformed into a dual fuel engine for operation on natural gas. The potential reduction of polluting emissions makes natural gas a very interesting alternative fuel for automotive applications. The aim of he present investigation is the transformation of a D.I. Diesel engine into a dual fuel engine with pilot injection via the common rail

Inthe present investigation, a parametric study of the geometric,characteristics ,of a ,two-cylinder four-stroke gasoline engine was carried out. Engine power, torque, specific consumption, engine efficiency, in-cylinder pressure,for both the cylinders and ,pressure ,along ,the intake and,exhaust,manifolds,at different positions were experimentally,measured ,for engine ,speeds ,ranging from,5000 to 9500 rpm. All measurements ,were ,made under steady,state conditions and full load. Engine

The experimental characterization of an innovative optical system for detection of carbon monoxide (CO) is reported. In this system a photodetector based on gallium nitride (GaN) and an UV light source are integrated. The gas flows between the light source and the GaN photodetector. The UV light source consists of a spark produced by an arc discharge which induced transitions in the gas, causing a modification of the light intensity as a function of gas composition. These transitions modify the fraction of light in the UV spectral region which is detected by the GaN-photodetector, as a function of the species concentration. By virtue of its structural properties, gallium nitride (GaN) allows to operate at high temperature and high speed and to work in-situ in the exhaust manifold of combustion engines at temperatures as high as 600degC, at which the deposited organic residuals on the detector can be oxidized. This assures the clear surface needed for a real time optical measurement of the species concentration to be used for a closed loop control of the fuel injection process. The system was applied to the detection of CO with concentration between 0-2.4% in a buffer of pure nitrogen gas, showing an increase in the measured photocurrent as a function of the above gases

ABSTRACT The paper proposes a cost-saving analytical methodology using empirical based models to efficiently evaluate design alternatives in the optimization of a CNG converted diesel engine. The procedure is performed in five steps. Firstly, a database of different combustion chambers that can be obtained from the original piston is obtained. The chambers in the database differ for the shape of the bowl, the value of the compression ratio, the offset of the bowl and the size of the squish region. The second step of the procedure is the selection, from the first database, of the combustion chambers able to resist to the mechanical stresses due to the pressure and temperature distribution at full load. For each combination of suitable combustion chamber shape and ignition timing, a CFD simulation is used to evaluate the combustion performance of the engine. Then, a post-processing procedure is used to evaluate the detonation tendency and intensity of each combination. All the tools developed for the application of the method have been linked in the ModeFrontier optimization environment in order to perform the final choice of the combustion chamber. The overall process requires not more of a week of computation on the 4 processor servers considered for the optimization. Moreover, the selected chambers can be obtained from the original piston of the engine. Therefore, the conversion cost of the engine is quite small compared with the case of a completely new piston. The procedure can be applied to diesel engines to be converted to either CNG dedicated or dual fuel combustion. The main aspects and challenges to be taken into account in both cases are also analyzed.

ABSTRACT In this work we present a thermoelectric energy harvesting system consisting of a miniaturized and wearable flexible thermoelectric generator (TEG) and a dedicated ASIC, finalized to efficiently recover and manage energy from heat dispersed into the environment. The proposed TEG was realized on flexible Kapton substrate, which is particularly appreciated for its optimum properties of chemical and physical stability, permeability to atmospheric agents (humidity, oxygen) and thermal conductivity. Contrary to a conventional rigid substrate, like glass or silicon, a flexible one adds to the device lighter weight, increased robustness, freedom of shape, compactness, and low cost. Although the TEG was designed as "electronic garment" for wearable use in Ambient Assisted Living (AAL) applications, the device can be easily adapted to different contexts thanks to its flexibility and design that extend the application range to various sectors, from home automation and structural health monitoring to biotechnology. A Transfer Length Method (TLM) analysis was performed on three different multi-layer contact schemes in order to select the best solution to use for the deposition of both embedded thermometers to monitor the thermocouples junctions temperature and contact pads to electrically test single partitions of the array. A custom designed ASIC, based on step-up principle was coupled to the TEG in order to ensure a 1.2 V output and complete power management solution for wireless sensing and data acquisition.

ABSTRACT Present work highlights the progress in the field of polymeric package reliability engineering for a flexible thermoelectric generator realized by thin film semiconductor technology on Kapton®. Together with mechanical enhancement, the thermal insulation performance of the realized 3D custom package was tested. The effect of different plasma treatments on the mechanical performance and interface of a Polydimethylsiloxane (PDMS)/Kapton® assembly were investigated; in order to increase the package mechanical stability of the realized wearable power source, Kapton® surface wettability was investigated by static contact angle measurements using deionized water and PDMS as liquid test. In fact, well known weak adhesion between PDMS and Kapton® leads to delamination of the package with unrecoverable damage of the generator. Plasma effect on adhesion performances was evaluated by scratch test method. By a numerical thermal analysis, the device packaging was optimized by coupling the module realized onto Kapton foil (by thin film PVD technology) to a PDMS layer opportunely molded to thermally insulate TEG cold junctions and enhance the thermal gradient useful for thermocouples operation. Fabrication process with optical lithography steps allows high resolution definition of thermoelectric semiconductors alloys. The main advances in wearable generator packaging technology is represented by increased structural robustness of PDMS/Kapton® assembly in terms of delamination and fatigue resistance.

ABSTRACT In this paper we report on optical absorption measurements performed on several metal oxide nanoparticles (ZnO, CeO2, Fe2O3) as a function of temperature in the range 25500 °C, in order to study the optical properties, and to investigate how several heating cycles could affect nanoparticle structural stability and absorption characteristics. These are quite important issues to be investigated in order to assess the possibility to use such metal-oxide nanoparticles as gas-based high temperature nanofluid in concentrated solar power (CSP).