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The aim of the present paper is to provide an insight into the fluid dynamic processes that occur during the air/fuel mixture formation period in direct injection diesel engines. An experimental and numerical investigation has been performed to analyse the mixing process between an evaporating diesel spray and a swirl air flow under realistic engine conditions. Experimental tests have been carried out spraying the fuel within an optically accessible prototype 2-stroke Diesel engine equipped with an external combustion chamber having cylindrical shape. The intake air flow, coming from the engine cylinder, is forced within the combustion chamber by means of a tangential duct generating a well structured swirl flow similar to that developing in a real light duty diesel engine with a high swirl ratio. A micro-sac 5-hole, 0.13 mm diameter, 150° spray angle electro-hydraulic injector supplies the fuel by a common rail injection system able to manage multiple injection strategies.

This paper illustrates a numerical and experimental analysis of performances and overall noise radiated from a common rail light duty diesel engine. The engine was equipped with two different injection systems: an under development low-cost fuel injector and a commercial Bosch one, employed for automotive applications. The injectors behaviour was compared throughout an experimental investigation that was carried out on a naturally aspirated, four strokes, two valves, single cylinder engine (225 cm3 displacement). Both engine performances, pollutant and noise emissions were measured at different operating conditions for two injection strategies. Concerning the acoustic analysis, both structure born and gasdynamic noise contributions were estimated using different experimental techniques.

This paper illustrates the results of an experimental investigation on the liquid fuel spray from a multi-jet common rail injection system both under non evaporative and evaporative conditions. Tests have been taken using a 5 hole, 0.13 mm diameter, 150° spray angle, micro-sac nozzle having a flow rate of 270 cm3/30 sec@10 MPa exploring different injection strategies. Experiments have been taken, under non evaporative conditions, injecting the fuel within stagnant inert gas, at different density, in a high-pressure optically-accessible cylindrical vessel with three large quartz windows. Under evaporative conditions, the experiments have been taken within a crank-case scavenged single-cylinder 2-stroke direct injection Diesel engine provided of optical accesses to the combustion chamber. It allows to study the fuel injection process under thermodynamic conditions similar to those currently reached in modern direct injection diesel engines.

The paper summarizes the activities related to the characterization of the noise sources and related sound emission levels emitted by a single cylinder diesel engine. A deep analysis is carried out aiming to clearly define the various noise sources, through the employment of numerical and experimental techniques. In particular, an intensimetric analysis is carried out to define a bi-dimensional noise level map around the engine. In addition, the gasdynamic noise, at the different engine speeds, is measured through a microphone mounted near the intake and exhaust mouth. Contemporarily to the experimental activity, a theoretical one dimensional simulation of the whole engine, is also carried out. The presented one-dimensional analysis is able to characterize the wave propagation phenomena in the external ducts and provide the estimation of both engine performance and gasdynamic noise emission too.

The aim of this paper is to analyse the main concerns related to on board hydrogen catalytic production of fuel cell electric vehicles, starting from different gaseous and liquid fuels. In particular, limits and potentialities of hydrocarbons and alcohols have been examined, considering steam reforming and partial oxidation reactions with reference to emission and efficiency implications. Preliminary results of an experimental investigation on steam reforming of natural gas and liquid hydrocarbons are reported. Furthermore, a mono-dimensional mathematical model of methane steam reformer based on first order kinetics has been developed to simulate the experimental results.

Conventional methods for combustion gas concentration measurement are typically based on gas sampling, sample treatment and subsequent analysis. These procedures could affect the species concentrations in particular when temporal variations of process parameters are under study. Moreover, in these methods, the concentration measurements are usually performed at standard temperature and pressure. In order to overcome these limitations, in-situ and real-time concentration measurement techniques are needed. In this paper, an in-situ technique with high spatial and temporal resolution, based on ultraviolet-visible absorption spectroscopy, was proposed. This technique allowed the simultaneous determination of NO and OH absolute concentrations inside optically accessible diesel combustion chamber. Temporal and spatial distribution of OH and NO was evaluated.

A chemical and physical characterization of particulate emitted in undiluted exhaust of single cylinder direct injection (D.I.) diesel engine was made by an optical technique. On-line scattering and extinction measurements in the spectral range from 200 to 500nm were carried out in the exhaust ofthe engine operating under steady-state conditions. These measurements provided a useful tool for the comprehension of chemical and physical structure of the particulate. They allowed the evaluation in real time of the size, the concentration and also the optical properties. Preliminary results of size and mass concentration of particulate are presented. A good agreement was observed comparing the results with those obtained by gravimetric measurements, TEM and X-ray diffraction. HIGH EFFICENCY OF DIESEL ENGINES and their ability to burn heavy fuels make them ofgreat interest in the transportation field.

The fluid-mechanic behaviour of straight-sided and re-entrant chamber geometries has been studied using laser doppler anemometry (LDA) technique. Measurements have been carried out during the compression stroke in a direct injection diesel engine, representative of medium size family, operating at 1000 rpm under motored conditions. The mean motion and turbulence intensity have been computed using a filtering procedure on the LDA data. Using the second version of KIVA code, the air flow field evolution during the same crank angle period has been also computed. To perform proper comparisons between measured and computed values of mean velocity and turbulence intensity, a careful choice of the initial conditions for computations has been performed. Reasonable agreement has been found between computed and measured mean swirl velocities for both combustion chamber geometries tested. On the contrary, the computed turbulence intensities underestimate those measured.

The development of combustion system of a multipurpose utility single cylinder d.i. diesel engine for low emissions is discussed. Engine tests, using two shallow re-entrant combustion bowls, four nozzles with reduction sac volume and different holes diameter and spray angle, have been carried out. Shallow re-entrant bowls with high compression ratio give low smoke emissions. Nozzles with reduced sac volume decrease the hydrocarbon emissions while NOx emissions can be limited operating at more retarded start of combustion.

The optimization of combustion system of a single-cylinder d.i. diesel engine, representative of heavy-duty family, is discussed. The characterization of in-cylinder fluid motion of a conventional straight-sided and a re-entrant combustion chamber, carried out by LDA technique, is presented. Engine tests, using the same chambers and sacless nozzles with different holes diameter and appropriate spray angle, have been performed. Strong reduction of smoke and HC emissions has been obtained, remaining unchanged the engine performance.

Technical information on the development of a new Lombardini prechamber diesel engine family, called FOCS, is given. Market requirements in terms of high performance, low fuel consumption, light engine weight and low noise and pollutant emissions have been met. The engine family consists of 2, 3 and 4 cylinder models with 72 mm cylinder bore and with two stroke-length (62, 75 mm) version covering 505 cc, 611 cc, 916 cc and 1222 cc displacement. Comparison of performance and emissions between FOCS 602 and competitive engines nowadays available on the international market is reported.

Improvement of combustion system for low emissions of a single cylinder diesel engine is presented. In particular the effects of spray angle, holes diameter and number, compression ratio and combustion chamber geometry on engine performance and emissions are evaluated. The fluid-dynamic behaviour of combustion system is analyzed by LDA technique. Engine tests have been carried out at two engine speed and at different start of combustion. The particulate matter has been analyzed in terms of soluble organic fraction and dry soot.

Comparisons are presented of computed and measured air flow fields in an open chamber diesel engine running at 1,000 and 2,000 rpm without combustion. Both Conchas spray and KIVA codes were tested. The effect of turbulence is represented using both K-ε and SGSD (Sub-grid Scale Differential) submodels. A Laser Doppler Velocimeter (LDV) was used to make velocity and turbulence measurements during the compression stroke. Reasonable agreement between numerical and experimental results for the engine examined was observed.