Newly developed Diesel engine control strategies are mainly aimed at pollutant emissions reduction, due to the increasing request for engine-out emissions and fuel consumption reduction. In order to reduce engine-out emissions, the development of closed-loop combustion control algorithms has become crucial. Modern closed-loop combustion control strategies are characterized by two main aspects: the use of high EGR rates (the goal being to obtain highly premixed combustions) and the control of the center of combustion. In order to achieve the target center of combustion, conventional combustion control algorithms correct the measured value by varying Main injection timing. It is possible to obtain a further reduction in pollutant emissions through a proper variation of the injection parameters. Modern Diesel engine injection systems allow designing injection patterns with many degrees of freedom, due to the large number of tuneable injection parameters (such as start and duration of each injection). Each injection parameter’s variation causes variations in the whole combustion process and, consequently, in pollutant emissions production. Injection parameters variations have a strong influence on other quantities that are related to combustion process effectiveness, such as noise radiated by the engine. This work presents a methodology that allows real-time evaluating combustion noise on-board a vehicle. The radiated noise can be evaluated through a proper in-cylinder pressure signal processing. Even though in-cylinder pressure sensor on-board installation is still uncommon, it is believed that in-cylinder pressure measurements will be regularly available on-board thanks to the newly developed piezo-resistive sensors. In order to set-up the methodology, several experimental tests have been performed on a 1.3 liter Diesel engine mounted in a test cell. The engine was run, in each operating condition, both activating and deactivating pre-injections, since pre-injections omission usually produces a decrease in pollutant emissions production (especially in particulate matter) and a simultaneous increase in engine noise. The investigation of the correlation between combustion process and engine noise can be used to set up a closed-loop algorithm for optimal combustion control based on engine noise prediction.

There has been an extensive worldwide search for alternate fuels that fit with the existing infrastructure and would thus displace fossil-based resources. In metabolic engineering work at Argonne National Laboratory, strains of fuel have been designed that can be produced in large quantities by photosynthetic bacteria, eventually producing a heavy alcohol called phytol (C 20 H 40 O). Phytol’s physical and chemical properties (cetane number, heat of combustion, heat of vaporization, density, surface tension, vapor pressure, etc.) correspond in magnitude to those of diesel fuel, suggesting that phytol might be a good blending agent in compression ignition (CI) engine applications. The main reason for this study was to investigate the feasibility of using phytol as a blending agent with diesel; this was done by comparing the performance and emission characteristics of different blends of phytol (5%, 10%, 20% by volume) with diesel. The experimental research was performed on a single-cylinder engine under conventional operating conditions. Since phytol’s viscosity is much higher than that of diesel, higher-injection-pressure cases were investigated to ensure the delivery of fuel into the combustion chamber was sufficient. The influence of the fuel’s chemical composition on performance and emission characteristics was captured by doing an injection timing sweep. Combustion characteristics as shown in the cylinder pressure trace were comparable for the diesel and all the blends of phytol at each of the injection timings. The 5% and 10% blends show lower CO and similar NO x values. However, the 20% blend shows higher NO x and CO emissions, indicating that the chemical and physical properties have been altered substantially at this higher percentage. The combustion event was depicted by performing high-speed natural luminosity imaging using endoscopy. This revealed that the higher in-cylinder temperatures for the 20% blend are the cause for its higher NO x emissions. In addition, three-dimensional simulations of transient, turbulent nozzle flow were performed to compare the injection and cavitation characteristics of phytol and its blends. Specifically, area and discharge coefficients and mass flow rates of diesel and phytol blends were compared under corresponding engine operating conditions. The conclusion is that phytol may be a suitable blending agent with diesel fuel for CI applications.

This paper presents an application of the mean value combustion model to simulate large bore turbocharged diesel engines, coupled with large electric AC synchronous generators, to mimic power generation within a training simulator for a ship board electrical power system. A mean value engine model has been developed to simulate the most prevalent phenomena occurring in diesel direct injection internal combustion engines. The combustion process is modeled as a mean value system where characteristics of combustion are averaged over the entire cycle. Detailed models of the air intake, fuel delivery, and internal/external cooling systems have been developed using concepts from fluid dynamics and thermodynamics. The engine model has been created in MATLAB ® Simulink ® to simulate actual hardware signals sent to the power management controller to facilitate the development of the power system trainer. The model has been structured so that it is highly adaptable and is capable of simulating a wide variety of engine bore sizes and cylinder numbers which has significantly increased the utility of the work presented herein.

Spark ignition constitutes the most common way of mixture inflammation for gas engines of CHP units (combined heat and power). However, spark plug durability is limited due to spark erosion. High maintenance costs as a result of frequent spark plug replacements are the consequence. Beside the durability aspect, the inflammation of lean mixtures makes high demands on the inflammation process itself. Due to the small reactive mixture volume, the level of air-fuel ratio as well as the efficiency increase is limited. The ignition by means of a hot surface enables an increase of the reactive mixture volume and, as a result, an enhancement of the lean burn limit. A hot surface ignition (HSI) system was developed for stationary lean burn operation in due consideration of low manufacturing costs and electrical characteristics that allow a reliable control of the ignition timing. The main component of the inflammation element is a pin-shaped glow plug, whose temperature can be regulated by adjusting the electrical power. Due to external influences such as fluctuating ambient pressure and gas quality a control unit is essential for securing an optimal combustion phasing of the engine. Several designs of hot surface ignition, including passive prechamber and shielded versions, were tested on a single cylinder test bed engine operating with a homogeneous air-petrol mixture. The engine tests were accompanied by 3D flow simulations. The trials showed that the power consumption, and hence the temperature of the hot surface, as well as the flow conditions around the glow plug have a strong influence on the ignition timing. Furthermore, a strong correlation between the mean combustion chamber temperature and combustion phasing became evident. Based on this coherence, it was possible to develop a closed-loop control that adjusts the combustion phasing by controlling the combustion chamber temperature at a stationary operating point. The shielded inflammation element stood out to be the target-aiming version of hot surface ignition. It is characterised by an accelerated inflammation which allows reducing the cycle-to-cycle variations compared to prechamber spark ignition and, hence, to enhance the lean burn limit. As a result, a significant improvement of the efficiency-NO x trade-off is possible. The obtained results provide the basis for further trials on a gas engine CHP module operating with natural gas.

Porous media (PM) has interesting advantages in compared with free flame combustion due to the higher burning rates, the increased power range, the extension of the lean flammability limits, and the low emissions of pollutants. Future clean internal combustion (IC) engines should have had minimum emissions level (for both gaseous and particulate matter) under possible lowest fuel consumption permitted in a wide range of speed, loads and having good transient response. These parameters strongly depend on mixture formation and combustion processes which are difficult to be controlled in a conventional engine. This may be achieved by realization of homogeneous combustion process in engine. This paper deals with the simulation of direct injection IC engine equipped with a chemically inert PM, with cylindrical geometry to homogenize and stabilize the combustion of engine. A 3D numerical model for PM engine is presented in this study based on a modified version of the KIVA-3V code. Due to lack of any published data for PM engines, numerical results of thermal and combustion wave propagation in a porous medium are compared with experimental data of lean methane-air mixture under filtration in packed bed and very good agreement is seen. For PM engine simulation methane as a fuel is injected directly inside hot PM that is assumed, mounted in cylinder head. Lean mixture is formed and volumetric combustion occurs in PM and in-cylinder. Mixture formation, pressure and temperature distribution in both phases of PM and in-cylinder fluid with the production of pollutants CO and NO and also effects of injection time in the closed part of the cycle are studied.

One of the key conjunctions in the IC engine is that made by the top compression ring to the cylinder liner. Although the compression ring has seen considerable improvements since its introduction into steam engines by John Ramsbottom in the 1850s, its multiple and often contradictory functions still remain a challenge today. The primary aim has always been to seal the combustion chamber and guard against leakage of combustion gasses. The ring is also required to conduct some of the generated heat away. These requirements call for good ring-bore conformance, but often at the expense of increased friction. A simplified inter-ring gas flow model, as well as the measured chamber pressure using a Kistler pressure transducer is carried out under motored conditions to obtain the net gas pressure acting behind the ring. This and the elastic pressure as the result of ring restoring tension force in fitment constitute the contact load, which is usually carried by a mixed-hydrodynamic regime of lubrication. The conjunction pressures are treated as a combination of hydrodynamic generated pressures and asperity-pair interactions. The former is obtained by solution of two dimensional Reynolds equation, whilst the latter is determined assuming a Gaussian distribution of asperities on the counterfaces. Surface topography of the bounding solids; the compression ring and the liner are measured and used as appropriate statistical functions in the Greenwood and Tripp model. Using an analytical flow model, pressure acting behind the ring (on the inner periphery of the ring) is obtained, leading to the calculation of ring-bore friction. A floating liner is used to measure friction of piston and ringpack in situ . The characteristic of the predicted variations are compared with the measured data. However, a quantitative comparison is not possible as the measured data corresponds to all the conjunctions of piston system, including the oil control rings as well as the piston skirt. The results show that variation of gas force behind the ring significantly changes the ring-bore contact, thus friction and the nature of interactions.

The impact of fuel composition on the emission performance and combustion characteristics for partially premixed combustion (PPC) were examined for four fuels in the gasoline boiling range together with Swedish diesel MK1. Experiments were carried out at 8 bar IMEP g and 1500 rpm with 53±1% EGR and λ = 1.5. This relation gave inlet mole fractions of approximately 5% CO 2 and 13% O 2 . The combustion phasing was adjusted by means of start of injection (SOI), for all fuels, over the range with stable combustion and acceptable pressure rise rate combined with maintained λ, EGR ratio, inlet pressure, and load. The operating range was limited by combustion instability for the high RON fuels, while MK1 and the low RON fuels could be operated over the whole MBT plateau. The largest difference in engine-out emissions between the fuels was the filtered smoke number (FSN), as the gasoline fuels produced a much lower FSN value than MK1. Higher RON value gave higher levels of carbon monoxide (CO) and unburned hydrocarbon (HC) for the gasoline fuels, while MK1 had the lowest levels of these emissions.

The behavior of lagrangian spray models for the application in large two stroke marine engines is investigated. 3D-CFD simulations of a Spray Combustion Chamber (SCC) with a single hole (0.875 mm diameter) injector are presented and compared with experimental results. Shadow images of the spray under evaporating and non-evaporating conditions, with and without swirl flow and for different chamber pressures are available by means of which the simulation results are validated. A novel post processing methodology for 3D CFD spray simulations is introduced, which converts the numerical data into images which allows for a more rigorous quantitative comparison with the experimental data. Good agreement of the simulation results with the experiment is reported both in terms of spray penetration as well as concerning the evaporation of the fuel. Since the appropriate discretization of the large volumes typical of 2-stroke marine engines presents a substantial challenge, the influence of the grid resolution is investigated. In addition, the influence of fuel quality on the evolution of the spray morphology is assessed. For this purpose, simulations with heavy fuel oil (HFO) are compared with experiment.

Recent developments in numerical techniques and computational processing power now permit time-dependent, multi-dimensional computational fluid dynamic (CFD) calculations with reduced chemical kinetic mechanisms (approx. 20 species and 100 reactions). Such computations have the potential to be highly effective tools for designing lean-burn, high BMEP natural gas engines that achieve high fuel efficiency and low emissions. Specifically, these CFD simulations can provide the analytical tools required to design highly optimized natural gas engine components such as pistons, intake ports, precombustion chambers, fuel systems and ignition systems. To accurately model the transient, multi-dimensional chemically reacting flows present in these systems, chemical kinetic mechanisms are needed that accurately reproduce measured combustion data at high pressures and lean conditions, but are of sufficient size to enable reasonable computational times. Presently these CFD models cannot be used as accurate design tools for application in high BMEP lean-burn gas engines because existing detailed and reduced mechanisms fail to accurately reproduce experimental flame speed and ignition delay data for natural gas at high pressure (40 atm and higher) and lean (0.6 equivalence ratio (ϕ) and lower) conditions. Existing methane oxidation mechanisms have typically been validated with experimental conditions at atmospheric and intermediate pressures (1 to 20 atm) and relatively rich stoichiometry. These kinetic mechanisms are not adequate for CFD simulation of natural gas combustion in which elevated pressures and very lean conditions are typical. This paper provides an analysis, based on experimental data, of the laminar flame speed computed from numerous, detailed chemical kinetic mechanisms for methane combustion at pressures and equivalence ratios necessary for accurate high BMEP, lean-burn natural gas engine modeling. A reduced mechanism that was shown previously to best match data at moderately lean and high pressure conditions was updated for the conditions of interest by performing sensitivity analysis using CHEMKIN. The reaction rate constants from the most sensitive reactions were appropriately adjusted in order to obtain a better agreement at high pressure lean conditions. An evaluation of this adjusted mechanism, “MD19”, was performed using Converge CFD software. The results were compared to engine data and a remarkable improvement on combustion performance prediction was obtained with the MD19 mechanism.

Over the two last decades, gaseous and particle mass emissions of new diesel engines have been reduced effectively and progressively in response to the emissions legislation and due to the applied new technologies. There is, however, increasing concern about whether the engine modifications, while improving combustion and reducing emissions, have increased the number emissions of ultrafine and nanoparticles. So far, emissions regulations have solely been based on particulate matter (PM) mass measurements, not on particle number. Nanoparticles, however, form a major part of the PM emissions, but they do not considerably contribute to the PM mass and can not be seen as a problem, if only PM mass is determined. Therefore, there is increasing interest in expanding the scope of the regulations to also include particle number emissions, e.g. Euro VI for on-road engines. The PM number limit will also be enforced for non-road engines slightly later. Thus, more information is required about the particle number emissions themselves, but also about the effects of the engine technology on them. Wall-flow diesel particulate filters (DPFs) reduce the particle number very effectively within the entire particle size range. Nevertheless, in order to keep the DPF as small as possible and to lessen the need for regeneration, the engine-out PM number should also be minimized. If the DPF could be left out or replaced by a simpler filter, there would be greater freedom of space utilization or cost savings in many non-road applications. This might be realized in installations where the engine is tuned at high raw NO x and an SCR system is adopted for NO x reduction. However, it is not self-evident that new engine technologies would reduce the PM number emissions sufficiently. In this study, particle number emissions were analyzed in several non-road diesel engines representing different engine generations and exploiting different emissions reduction technologies: 4- or 2-valve heads, exhaust gas recirculation (EGR), different injection pressures and strategies, etc. All engines were turbocharged, intercooled, direct-injection non-road diesel engines. Most engines used common-rail fuel injection technology. Comparisons were, however, also performed with engines utilizing either a distributor-type or an in-line fuel injection pump to see the long-term development of the particle number emissions. In this paper, the PM number emissions of nine (9) non-road diesel engines are presented and compared. Gaseous exhaust emissions and fuel consumption figures are also provided.

Diesel low temperature combustion (LTC) is capable of producing diesel-like efficiency while emitting ultra-low nitrogen oxides (NOx) and soot emissions. Previous work indicates that well controlled single-shot injection with exhaust gas recirculation (EGR) is an operative way of achieving diesel LTC from low to mid engine loads. However, as the engine load is increased, demanding intake boost and injection pressure are necessary to suppress high soot emissions during the transition to LTC. The use of volatile fuels such as ethanol are deemed capable of promoting the cylinder charge homogeneity, which helps to overcome the high soot challenge and thus potentially expand the engine LTC load range. In this work, LTC investigations have been carried out on a high compression ratio (18.2:1) engine. The engine was firstly fuelled with diesel, and LTC operation at 8 bar indicated mean effective pressure (IMEP) was enabled by sophisticated control of the injection pressure, injection timing, intake boost and EGR application. The engine performance was characterized as the baseline, and the challenges were identified. Further tests were aimed to improve the engine performance against these baseline results. Experiments were hence conducted on the same engine with secondary ethanol port injection (PI). Single-shot diesel direct injection (DI) was applied close to top dead center (TDC) to ignite the ethanol and control the combustion phasing. The control sensitivity has been studied through injection timing sweeps and EGR sweeps. Additional tests were performed to investigate the ethanol-to-diesel ratio effects on the mixture reactivity and the engine emissions. Engine load was also raised to 10 bar IMEP while keeping the simultaneously low NOx and soot emissions. Significant improvement of engine control and emissions was achieved by the DI+PI strategy.

Due to the vast resources of natural gas (NG), it has emerged as an alternative fuel for SI internal combustion engines in recent years. The need to have better fuel economy and less emission especially that of greenhouse gases has resulted in development of NG fueled engines. Direct injection of natural gas into the cylinder of SI internal combustion engines has shown great potential for improvement of performance and reduction of engine emissions especially CO2 and PM. Direct injection of NG into the cylinder of SI engines is rather new thus the flow field phenomena and suitable configuration of injector and combustion chamber geometry has not been investigated completely. In this study a numerical model has been developed in AVL FIRE software to perform investigation of direct natural gas injection into the cylinder of spark ignition internal combustion engines. In this regard, two main parts have been taken into consideration aiming to convert an MPFI gasoline engine to direct injection NG engine. In the first part of study multidimensional numerical simulation of transient injection process, mixing and flow field have been performed via different validation cases in order to assure the numerical model validity of results. Adaption of such a modeling was found to be a challenging task because of required computational effort and numerical instabilities. In all cases present results were found to have excellent agreement with experimental and numerical results from literature. In the second part, using the moving mesh capability, the validated model has been applied to methane injection into the cylinder of a direct injection engine. Five different piston head shapes have been taken into consideration in investigations. An inwardly opening multi-hole injector has been adapted to all cases. The injector location has been set to be centrally mounted. The effects of combustion chamber geometry have been studied on mixing of air-fuel inside cylinder via quantitative and qualitative representation of results. Based on the results, suitable geometrical configuration for a NG DI engine has been discussed.

During research on diesel engine EGR cooler fouling a test stand giving visual access to the building deposit layer has been developed. Initial experiments reveal the presence of large particles in the exhaust. While conventional wisdom is that diesel particulates typically have log-normal size distributions ranging approximately 10–200 nm, the tests reported here observe small numbers of particles with sizes on the order of tens of μm. Such particles are not generally reported in the literature because exhaust particle sizing instruments typically have inertial separators to remove particles larger than ∼1 μm in order to avoid fouling of the nanoparticle measurement system. The test stand provides exhaust or heated air flow over a cooled surface with Reynolds number, pressure, and surface temperature typical of an EGR cooler. A window allows observation using a digital microscope camera. Starting from a clean surface, a rapid build of a deposit layer is observed. A few large particles are observed. These may land on the surface and remain for long times, although occasionally a particle blows away. In order to study these particles further, an exhaust sample was passed over a fiberglass filter, and the resulting filtered particles were analyzed. Samples were taken at the engine EGR passage, and also in the test stand tubing just before the visualization fixture. The resulting images indicate that the particles are not artifacts of the test system, but rather are present in engine exhaust. MATLAB routines were developed to analyze the filter images taken on the microscope camera. Particles were identified, counted, and sized by the software. It is not possible to take isokinetic samples and give quantitative measurement of the number and size distribution of the particles because the particles are large enough that inertial and gravitational effects will cause them to at least partially settle out of the flows. Nonetheless, the presence of particles tens of μm is documented. Such particles are probably the result of in-cylinder and exhaust pipe deposits flaking. While these larger particles would be captured by the diesel particulate filter (DPF), they can affect intake and exhaust valve seating, EGR cooler fouling, EGR valve sealing, and other factors.

Inner nozzle flow characteristics (e.g., cavitation, turbulence, injection velocity) are known to affect spray development and hence combustion and emissions. Our previous studies showed that petrodiesel and biodiesel (soybean-based fuels) had very different cavitation and turbulence characteristics, which caused differences in spray breakup, penetration, dispersion, etc. Specifically, the atomization characteristics of biodiesel were worse than those of diesel; they were a direct consequence of biodiesel’s reduced cavitation and turbulence levels at the nozzle exit. In this study, the nozzle flow characteristics of biodiesel (from different feedstocks like tallow, soy, rapeseed, cuphea, and hydrotreated vegetable oil [HVO]) were compared with those of diesel. The first step was to obtain data on the physical properties of these fuels (e.g., their density, viscosity, surface tension, vapor pressure) at different temperatures. At full-needle open position, the cavitation contours scaled with the vapor pressure and viscosity; hence, methyl esters such as soy (SME), rapeseed (RME), and tallow (TME) exhibited less cavitation. The nozzle discharge coefficient, exit velocity, turbulent kinetic energy, and dissipation rate at the orifice exit were also compared for these fuels. Transient effects due to needle movement upon the inception of cavitation were studied. The effects of different needle-lift profiles (pertaining to various load conditions) on the nozzle flow development of these fuels were also characterized. This study also provides data on the critical boundary conditions for spray simulations from using the Kelvin Helmholtz-aerodynamic cavitation turbulence (KH-ACT) model, which accounts for cavitation and turbulence-induced breakup in addition to aerodynamic breakup.

The effect of spray penetration distance on fuel impingement on piston bowl of a 7.4 kW diesel engine for biodiesel-diesel blend (B20) was studied using modeling and CFD simulation. As the peak inline fuel pressure increased from 460 bar with base diesel to 480 bar with B20, the spray penetration distance (fuel jet) increases. It is observed from the study that the jet tip hits on piston bowl resulting to fuel impingement which is one of durability issues for use of biodiesel blend in the diesel engine. In addition to this, the simulation of effects of different injection pressures up to 2000 bar on spray penetration distance and wall impingement were also studied. The penetration distance increases with increase the in-line fuel pressure and it decreases with decrease nozzle hole diameter. The fuel impingement on piston bowl of the engine with high injection pressure (typically 1800 bar) can be avoided by decreasing the nozzle diameter from 0.19 mm to 0.1 mm. Increase in swirl ratio could also reduce fuel impingement problem.

A first-order lumped-parameter model for the prediction of thermal behavior of a single-cylinder gasoline engine for Hybrid Electric Vehicles (HEVs) has been implemented. The model is coupled with a zero-dimension in-cylinder model that evaluates the working cycle of the engine according to the actual operating conditions and calculates the temperature of the exhaust gases, the overall efficiency of the engine and the exhaust gases flow rate. The model takes into account the possibility of using exhaust gas heat recirculation in order to enhance engine warm-up during cold start which improves its efficiency. The supervisory strategy takes into account not only predicted speed and ambient and road conditions along a future time window but also actual battery state of the charge and engine temperature to select the optimal power split between the ICE-generator group and the batteries. The proposed model represents an improvement with respect to a previous investigation of the authors where the temperature of the engine were assumed to increase/decrease of on Celsius degree in each seconds according to the state of the engine (ON/OFF).

A prototype Diesel common rail direct-acting piezoelectric injector has been used to study the influence of fuel injection rate shaping on spray behavior (liquid phase penetration) under evaporative and non-reacting conditions. This state of the art injector allows a fully flexible control of the nozzle needle, enabling various fuel injection rates typologies under a wide range of test conditions. The tests have been performed employing a novel continuous flow test chamber that allows an accurate control on a wide range of thermodynamic test conditions (up to 1000 K and 15 MPa). The temporal evolution of the spray has been studied recording movies of the injection event with a fast camera (25 kfps) by means of the Mie scattering visualization technique. The analysis of the results showed a strong influence of needle position on the behavior of the liquid length. The needle position controls the effective pressure upstream of the nozzle holes. Higher needle lift is equivalent to higher effective pressures. According to the free-jet theory, the stabilized liquid-length depends mainly on effective diameter, spray cone-angle and fuel/air properties and does not depend on injection velocity. Therefore, higher injection pressures gives slightly lower liquid length due to small change in the spray cone-angle. However, partial needle lifts has an opposite effect: lower effective pressure upstream of the nozzle holes shows a dramatic increase on the spray cone-angle, reducing the liquid length. This behavior could be explained mainly due to the fact that the flow direction upstream of the nozzle holes is affecting the area coefficient, or in other words, the effective diameter of the holes.

Both the piston ring and cylinder bore experience wear throughout their life cycle. Therefore change occurs in the geometrical profile and topography of the ring. In addition, coating on the ring is also subject to wear, thus altering the physical/mechanical property of the contacting surface. These changes affect the tribological performance of the ring-bore conjunction. Geometrical changes often alter the ring contacting profile, which affects the entrainment of the lubricant into the conjunction. This can affect the regime of lubrication, thus mechanisms that contribute to friction. Wear of surfaces also plays some role in boundary friction in terms of topographical changes as well as surface properties such as hardness and asperity shear strength. Most analysis does not take into account changes in tribological conditions which occur as the result of these salient changes in practice. The paper intends to bridge this gap in the fundamental knowledge and provide explanations for some in-field experiences noted with wear of a compression ring in a typical engine test. The method of solution used is based on the average flow factors which are indicative of entrainment of the lubricant through the rough ring-bore conjunction. This approach was initiated by Patir and Cheng, for which realistic topographical parameters according to the stage of the wear process is included. Changes in friction and fuel energy consumed are predicted.

Analysis of the changes in mass and size of particles formed during the diesel combustion process, the morphological characteristics, and the trace elements within these amorphous particles was carried out using a total cylinder sampling system installed on a direct injection diesel engine. Utilizing field emission transmission electron microscope technology, the results showed that the amorphous particles formed during the combustion process were abundant in metallic and non-metallic elements mainly derived from the lubrication oil, which was found to have entered the combustion process, oxidized and combusted, further increasing the absorbed carbon particles during the later stages of combustion.

An experimental investigation has been carried out on a diesel 1000 cc, two-valve, three-cylinder, engine for heavy quadricycle and off-road applications. The engine was equipped with a unit-pump common rail injection system, automotive derived, with maximum pressure 140 MPa and ECU able to manage multinjection strategies in Euro 4 target for the foreseen applications. Experimental investigations on the fuel spray have been carried out in an optically accessible vessel at engine gas density. Spatial and temporal spray behavior has been studied by image processing of the evolving jet pictures. Spray tip penetrations, cone angles and fuel spatial density analysis have been extracted and correlated to the injection and engine parameters. On the other side, visible flame propagation and soot formation process have been evaluated by digital imaging at high spatial and temporal resolution using a quartz window of the third cylinder obtained modifying the engine head. Strategies consisting of two injections per cycle, pilot and main, and typical of real engine working conditions have been investigated in the pressure range 43–116 MPa both in terms of injection rates and injected fuel dispersion. The effects of different injection strategies on soot formation and exhaust emissions have been evaluated.