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The paper presents a comparative analysis of the operational parameters, smoke emission and the content of toxic components in exhaust gases of a compression ignition engine fuelled with fossil diesel, commercially available biodiesel (fatty acid methyl ester) and their 50%/50% blend. The study was carried out using a diesel engine equipped with an in-line injection pump used in delivery vans. An indirect injection, considerably worn engine was chosen because such engines are very often fuelled with the less expensive biodiesel. Measurements were made on an engine operated at different rotational speeds under full load as well as using the European Stationary Cycle (ESC) test. Emissions of regulated and non-regulated compounds were measured with the use of the Fourier-Transform Infrared (FTIR) analytical system, which provided concentrations of 23 exhaust gas components.

The paper investigates the cylinder liner wear and its influence on the engine blowby. The course of cylinder liner wear was established on the basis of investigation, which was carried out using 5 diesel engines during long-lasting operation in motor trucks. Cylinder diameters were periodically measured in two perpendicular planes at four depths of the liner. During service of the trucks the blowby rate was also measured, which enabled evaluating of the changes of the blowby rate as a function of truck mileage. The effect of cylinder wear on the blowby was also predicted with the use of a mathematical model of a gas flow through the ring pack. The results of the numerical simulations and empirical investigations are compared and discussed.

The paper considers the effect of axial and radial clearances of compression rings in the piston grooves on the engine blowby. A mathematical model of piston-rings-cylinder seal, which integrates model of gas flow through the crevices of the RPC seal and model of rings motions in the grooves was used to predict the influence of particular clearances values on the blowby. The results of numerical calculations show that this influence is different for the top and second ring clearances and depends on engine operating conditions (especially rotational speed). The paper also presents some results of experimental research conducted to verify the model. The results of the experiment confirmed the results of the numerical predictions.

The paper presents results of spectroscopic research of the air excess ratio in a combustion chamber of a spark- ignited engine fuelled with gasoline and LPG. For the evaluation of air excess ratio a correlation with relative concentration of HC and C2 radicals existing in combustion flame was used. Concentration of radicals was measured on the basis of chemiluminescence forming as a result of transition from electron-excited states. Light emission from the combustion chamber was recorded using measurement system composed of optical combustion sensor, transmission optical waveguides, optical filters, monochromators and electronic devices for signal conversion. A strong correlation of relative optical emission with air excess ratio in combustion chamber was confirmed. However, for different engine loads and rotational speeds, some scattering of measurement points was noticed. Therefore it was necessary to use artificial neural networks to analyze courses of optical signal.

The paper deals with the method of probabilistic car engine durability prediction. The method is based on observation of mechanical wear of elements composing piston-rings-cylinder assembly during short-term research and allows to calculate the probability of reaching wear limit value for a given time moment or mileage. The way of assessing the prediction error is also suggested. Two examples of calculation are made on the basis of cylinder liner wear data obtained from test-stand and truck on-road operational engine research. The prediction was verified in long-term maintenance studies carried out on five medium size trucks. Proposed method of assessing engine durability does not require complicated computations. It can be easily used for results of wear measurements done in various conditions and with different methods. The condition of efficient application of the method is knowledge of reliable value of boundary wear and usage of run-in engines during the experiments.

Evaluation of the air excess ratio (lambda) in the combustion chamber can be done on the base of simplified flame spectrum analysis. Although the obtained results are valuable for the better understanding of the process, they do not let to determine the air excess ratio in different operation conditions. The research limitations have appeared due to incomprehension of chemical and physical aspects of combustion process. Light intensity during the combustion is influenced by several parameters such as engine load, rotational speed, ignition timing, temperature etc. Thus, it is extremely difficult to develop an accurate measurement method based on evaluation of radicals' emission ratio. Artificial neural networks (ANN) can be used in order to derive air excess ratio from time-domain courses of light intensity signals measured in chosen wavelengths.

One of the most important utilization features of vehicle engine is its durability. Durability depends mainly on the wearing processes of frictional connections of engine elements. The studies of engine parts wearing can be divided into two kinds: quantitative and comparative according as the purpose is to define quantitative durability or comparison of the influence of selected design, technological and utilization factors. The present report describes distribution of metallic impurities coming from mechanical wear of parts in the combustion engine. Distribution of impurities between lubricating system and exhaust system is of nonlinear character. High nonlinearity appears in not fixed conditions of the engine. In the longer time interval of engine operation, the distribution proportions between oil, oil filter and exhaust gases are going to stabilize.

The paper is devoted to the issues of the non-stationary, stochastic analysis of the fuel injection. The aim of the experiment was to obtain data about SI engine operating parameters during operation. The object randomness in sequentially injected combustion engines are investigated. A numerical procedure is designed for the intake manifold mixture preparation to compensate the mixture variations. There are some direct consequences of inherent non-linearities in the basic dynamics of mixture preparation. Compensating for the mixture dynamics (fuel path, air path consisting of intake manifold and wall-wetting dynamics and the oxygen sensor dynamics) performs well only if the statistical properties of the stochastic processes are sufficiently matched. Since this a priori knowledge is hardly accessible in the present case, the authors implemented an experimental procedure.