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A transient analysis simulation program is developed for studying the response of an indirect injection, naturally aspirated, diesel engine after a rapid increase in load when this is equipped with various types of indirect acting governors. Analytical expressions are presented for the better simulation of engine mechanical friction, inertia moments and heat loss to the walls under transient conditions, governor dynamics for both the sensing element and the servopiston, soot emissions and the fuel pump operation. Various types of governor sensing elements (i.e. mechanical, electrical, two-pulse) and feedbacks (i.e. unity and vanishing) for the servomechanism are studied. Explicit diagrams are given to show how each combination of governor type and technical parameters (i.e. mass and number of flyweights, geometrical dimensions, amplification factors) affects the speed response as well as the speed droop and the recovery period of the particular engine.

The present work investigates the effect of low levels CO2 addition on the combustion characteristics inside a single cylinder optical engine operated under low load conditions. The effects of dilution levels (up to 7.5% mass flow rate CO2 addition), the number of pilot injections (single or double pilot injections) and injection pressure (25 or 40 MPa), are evaluated towards the direction of achieving a partially premixed combustion (PPC) operation mode. The findings are discussed based on optical measurements and via pressure trace and apparent rate of heat release analyses in a Ricardo Hydra optical light duty diesel engine. The engine was operated under low IMEP levels of the order of 1.6 bar at 1200 rpm and with a CO2 diluent-enhanced atmosphere resembling an environment of simulated low exhaust gas recirculation (EGR) rates. Flame propagation is captured by means of high speed imaging and OH, CH and C2 line-of-sight chemiluminescence respectively.

This study investigates the impact of mid-high biodiesel blends on the criteria and PAH emissions from a modern pick-up diesel vehicle. The vehicle was a Euro 4 (category N1, subclass III) compliant common-rail light-duty goods pick-up truck fitted with a diesel oxidation catalyst. Emission and fuel consumption measurements were performed on a chassis dynamometer equipped with CVS, following the European regulations. All measurements were conducted over the certification New European Driving Cycle (NEDC) and the real traffic-based Artemis driving cycles. Aiming to evaluate the fuel impact on emissions, a soy-based biodiesel, a palm-based biodiesel, and an oxidized biodiesel obtained from used frying oils were blended with a typical automotive ultra-low-sulfur diesel at proportions of 30, 50 and 80% by volume. The experimental results revealed that CO₂ emissions and fuel consumption exhibited an increase with biodiesel over all driving conditions.

A comprehensive transient analysis simulation model is used for the calculation of diesel engine performance under variable speed and load conditions. The analysis includes a detailed description of engine subsystems under transient conditions, thus accounting for the continuously changing character of transient operation, simulating among others the fuel injection, transient mechanical friction, heat losses to the walls and governor operation. The results of engine performance, at every time step during the transient event, are used as inputs for the formulation of thermal boundary conditions, which are needed for the calculation in a parallel way of the thermal transients propagating inside the engine structure.

Despite the improvement in HD Diesel engine out emissions future emission legislation requires significant reduction of both NOx and particulate matter. To accomplish this task various solutions exist involving both internal and external measures. As widely recognized, it will be possibly required to employ both types of measures to meet future emission limits. Towards this direction, it is necessary to reduce NOx further using internal measures. Several solutions exist in that area, but the most feasible ones according to the present status of technical knowledge are EGR, water injection or fuel/water emulsions. These technologies aim to the reduction of both the gas temperature and oxygen concentration inside the combustion chamber that strongly affect NOx formation. However, there remain open points mainly concerning the effectiveness of water addition techniques and penalties related to bsfc and soot emissions.

In the present work, a multi-zone model is presented for the simulation of HCCI engines. This model is an improvement of a previous one developed by the authors. The present model describes the combustion, heat and mass transfer processes for the closed part of the engine cycle, i.e. compression, combustion and expansion. The zones occupy geometrical positions within the engine cylinder and exchange heat and mass throughout the compression and expansion strokes, based on their spatial configuration. Heat exchange is considered between zones and to the cylinder wall. A phenomenological model has been developed to describe mass exchange between zones and the flow of a portion of the in-cylinder mixture in and out of the crevice region. The crevice flow is a new feature and is included in the present model since the crevice regions are considered to contribute to unburned HC emissions. Another new feature is the incorporation of chemical kinetics, based on combustion chemistry reactions.

In this study, the transesterification process of 4 different vegetable oils (sunflower, rapeseed, olive oil and used frying oil) took place utilizing ethanol, in order to characterize the ethyl esters and their blends with diesel fuel obtained as fuels for internal combustion engines. All ethyl esters were synthesized using calcium ethoxide as a heterogeneous solid base catalyst. The ester preparation involved a two-step transesterification reaction, followed by purification. The effects of the mass ratio of catalyst to oil, the molar ratio of ethanol to oil, and the reaction temperature were studied on conversion of sunflower oil to optimize the reaction conditions in both stages. The rest of the vegetable oils were converted to ethyl esters under optimum reaction parameters. The optimal conditions for first stage transesterification were an ethanol/oil molar ratio of 12:1, catalyst amount (3.5%), and 80 °C temperature, whereas the maximum yield of ethyl esters reached 80.5%.

A three-dimensional multi-zone combustion model is developed for the description of the combustion mechanism inside the engine cylinder of direct injection diesel engines. Various multi-zone models have been proposed in the past for the prediction of DI diesel engine performance and emissions. These models offer an alternative tool if one wants to avoid the use of other more complicated and sophisticated flow models that require high computational times. Most of them have the disadvantage that they focus mainly on emissions, failing to predict at the same time engine performance adequately. In almost all multi-zone models the resulting fuel jet after injection, which is divided into zones, is assumed to be symmetrical around its axis. In the present work a different approach is followed. The fuel jet is divided into zones in the three dimensions overcoming the need for the previous symmetry assumption.

During the past years most fundamental research worldwide has been concentrated on the direct injection diesel engine (DI). This engine has a lower specific fuel consumption when compared to the indirect injection diesel engine (IDI) used up to now in most passenger cars. But the application of the direct injection engine on passenger cars and light trucks has various problems. These are associated mainly with its ability to operate at high engine speeds due to the very low time available for combustion. To overcome these problems engineers have introduced various techniques such as swirl and squish for the working fluid and the use of extremely high pressure fuel injection systems to promote the air-fuel mixing mechanism. The last requires the solution of various problems associated with the use of the high pressure and relatively small injector holes.

Homogeneous Charge Compression Ignition (HCCI) engines have the potential of reducing NOx emissions as compared to conventional Diesel or SI engines. Soot emissions are also very low due to the premixed nature of combustion. However, the unburned hydrocarbon emissions are relatively high and the same holds for CO emissions. The formation of these pollutants, for a given fuel, is strongly affected by the temperature distribution as well as by the charge motion within the engine cylinder. The foregoing physical mechanisms determine the local ignition timing and burning rate of the charge affecting engine efficiency, performance and stability. Obviously the success of any model describing HCCI combustion depends on its ability to describe adequately both the chemistry of combustion and the physical phenomena, i.e. heat and mass transfer within the cylinder charge. In the present study a multi-zone model is developed to describe the heat and mass transfer mechanism within the cylinder.

During the last years a great deal of effort has been made for the reduction of pollutant emissions from direct injection Diesel Engines. Towards these efforts engineers have proposed various solutions, one of which is the use of gaseous fuels as a supplement for liquid diesel fuel. These engines are referred to as dual combustion engines i.e. they use conventional diesel fuel and gaseous fuel as well. The ignition of the gaseous fuel is accomplished through the liquid fuel, which is auto-ignited in the same way as in common diesel engines. One of the fuels used is natural gas, which has a relatively high auto-ignition temperature. This is extremely important since the CR of most conventional diesel engines can be maintained. In these engines the released energy is produced partially from the combustion of natural gas and from the combustion of liquid diesel fuel.

The need of a more realistic and dynamic driving cycle which simulates real-world driving conditions in the largest city in the greater area of Balkans, led to the development of the Athens Driving Cycle (ADC). Emission and fuel consumption measurements were conducted over the ADC and compared with those of the New European Driving Cycle (NEDC) using a chassis dynamometer. A Euro II compliant diesel vehicle was used in this study, fuelled with a typical automotive diesel fuel and biodiesel blends at proportions of 5, 10, and 20 % respectively. The unregulated emissions were characterized by determining the soluble organic fraction (SOF) in the particulate matter, together with qualitative hydrocarbon analysis present in the SOF fraction, and of carbonyl compounds (aldehydes, ketones). Emissions of NOx, CO, THC, CO2, and PM10 were also measured over the two test cycles.

During recent years, the deterioration of greenhouse phenomenon, in conjunction with the continuous increase of worldwide fleet of vehicles and crude oil prices, raised heightened concerns over both the improvement of vehicle mileage and the reduction of pollutant emissions. Diesel engines have the highest fuel economy and thus, highest CO2 reduction potential among all other thermal propulsion engines due to their superior thermal efficiency. However, particulate matter (PM) and nitrogen oxides (NOx) emissions from diesel engines are comparatively higher than those emitted from modern gasoline engines. Therefore, reduction of diesel emitted pollutants and especially, PM and NOx without increase of specific fuel consumption or let alone improvement of diesel fuel economy is a difficult problem, which requires immediate and drastic actions to be taken.

High efficiency, power concentration and reliability are the main requirements from Diesel Engines that are used in most technical applications. This becomes more important with the increase of engine size. For this reason the aforementioned characteristics are of significant priority for both marine and power generation applications. To guarantee efficient engine operation and maximum power output, both research and commercial communities are increasingly interested in methods used for supervision, fault-detection and fault diagnosis of large scale Diesel Engines. Most of these methods make use of the measured cylinder pressure to estimate various critical operating parameters such as, brake power, fuel consumption, compression status, etc. The results obtained from the application of any diagnostic technique, used to assess the current engine operating condition and identify the real cause of the malfunction or fault, depend strongly on the quality of these data.

FAME is the most common renewable component of conventional automotive diesel. Despite the advantages, biodiesel is more susceptible to oxidative deterioration and due to its chemical composition as well as its higher affinity to water, is considered to be a favorable substrate for microorganisms. On the other hand, apart from biodiesel, alcohols are considered to be promising substitutes to conventional diesel fuel because they can offer higher oxygen concentration leading to better combustion characteristics and lower exhaust emissions. More specifically, n-butanol is a renewable alcohol demonstrating better blending capabilities and properties when it is added to diesel fuel, as its composition is closer to conventional fuel, when compared ethanol to for example. Taking into consideration the alleged disinfectant properties of alcohols, it would be interesting to examine also the microbial stability of blends containing n-butanol in various concentrations.

In the present paper a new method is proposed for the analysis of the two main phases of the engine exhaust stroke blowdown and displacement. The method is based on the processing of fast-response experimental temperatures obtained from the exhaust manifold wall during the engine cycle. A novel experimental installation has been developed, which separates the engine transient temperature signals into two groups, namely the long- and the short- term response ones. This has been achieved by processing the respective signals acquired from two independent data acquisition systems. Furthermore, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object-oriented, control code for fast data acquisition have been designed and applied. For the experimental procedure a direct injection (DI), air-cooled diesel engine is used.

An experimental analysis is carried out to investigate several heat transfer characteristics during the engine cycle, in the combustion chamber and exhaust manifold walls of a direct injection (DI), air-cooled, diesel engine. For this purpose, a novel experimental installation has been developed, which separates the engine transient temperature signals into two groups, namely the long-and the short- term response ones, processing the respective signals in two independent data acquisition systems. Furthermore, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object-oriented, control code for fast data acquisition have been designed and applied. Experimentally obtained cylinder pressure diagrams together with semi-empirical equations for instantaneous heat transfer were used as basis for the calculation of overall heat transfer coefficient.

In this paper, the results are presented from the analysis of the second stage of an experimental investigation with the aim to provide insight to the cyclic, instantaneous heat transfer phenomena occurring in both the cylinder head and exhaust manifold wall surfaces of a direct injection (DI), air-cooled diesel engine. Results from the first stage of the investigation concerning steady-state engine operation have already been presented by the authors in this series. In this second stage, the mechanism of cyclic heat transfer was investigated during engine transient events, viz. after a sudden change in engine speed and/or load, both for the combustion chamber and exhaust manifold surfaces. The modified experimental installation allowed both long- and short-term signal types to be recorded on a common time reference base during the transient event.

A great deal of research is taking place at the present time in the field of diesel engines, especially regarding the emission of gaseous pollutants and soot. This research is essential for engine manufacturers since it is difficult for diesel engines to meet current standards regarding soot and nitric oxide emissions. The problem will become even more severe when the new legislation will be applicable requiring a 50% reduction of existing levels. Many manufacturers and researchers feel that engines will be difficult to meet this criterion without the use of other techniques such as gas aftertreatment or newly developed fuels (low sulfur content, etc.). The aim of this research is to examine the effect of fuel composition and physical properties on the mechanism of combustion and pollutants formation.

Cylinder pressure measurements are common practice for internal combustion reciprocating engines during field or lab applications for the purpose of combustion analysis, condition monitoring etc. The most accurate method is to measure cylinder pressure using a crank angle encoder as a trigger source to guarantee cylinder pressure measurement at predefined crank angle events. This solution, even though favorable, presents a number of practical difficulties for field applications and increased cost, for this reason its use is practically restricted to lab applications. Therefore a commonly used approach for ad hoc measurements is to digitize samples at fixed time intervals and then convert time into crank angle assuming a constant rotational speed. But if engine rotational speed is not constant within the engine cycle this may result to incorrect cylinder pressure CA referencing.