International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The aim of the article is to investigate the optical properties of Bulgarian honey in regard to the potential of honey discrimination on the base of its botanical origin. Samples from three types of honey (acacia, linden, and honeydew) are measured by a fluorescence spectrometer recording emission from 350 to 800 nm with excitation at 370, 395 and 405 nm. A combination of fluorescence emission spectra with some colorimetric parameters (CIELab) is used as input data of three types of honey classifiers: the first two are based on linear and quadratic discriminant analysis, and the third one uses an artificial neural network. The neural classifier is realized as a multilayered perceptron with backpropagation learning algorithm. Principal components analysis (PCA) is used for reducing the number of inputs and for a proper visualization of the experimental results. The comparative analysis of the three classifiers is based on leave-one-out-cross validation test carried out in MATLAB environment.

The main purpose of this paper is a numerical simulation of methane injection process in the inlet manifold of a compression ignition engine. The paper gives an overview of issues related to the turbulence modeling. Computational resources such as the amount of time for the simulation and the memory of the individual models were discussed. While it is impossible to state categorically which model is the most appropriate for a specific application, general guidelines are presented in order to help you choose the turbulence model for the flow you want to model.

The paper deals with non-dismountable diagnostic of the power of a turbocharged Diesel engine. For the purposes of diagnostic the transient operation mode of the engine was described by an extended mathematic model that takes into account the influence of suction volumes and exhaust pipes. The results obtained by this improved model were similar to the values measured by an experiment. This model produces relatively more trustworthy information regarding the influence of some typical defects on the chosen diagnostic parameters. Finally, the improvement makes possible to more accurately identify them, on the basis of changes of selected and measured diagnostic quantities the defect that has caused these changes.

The escalating fuel price and carbon dioxide legislation have renewed the interest in the methods of increasing engine thermal efficiency beyond in-cylinder techniques. The aim of this study is to review the latest technologies of waste heat recovery of exhaust gases in internal combustion engines. These include turbocompounding systems, thermoelectric generators, thermoacoustic systems and closed-loop thermodynamic cycles based on Stirling, Ericsson and Rankine cycles. A number of studies revealed that Rankine cycle is the most perspective waste heat recovery system due to its higher thermal efficiency. Finally, the components of the Rankine cycle (working fluid, evaporator and expander) were studied in detail.

The article presents a numerical study of pre-injection strategy in order to reduce the rate of heat release and pressure rise in a modern direct injection diesel engine, developed for passenger car. A model of the engine was built in advanced simulation code AVL BOOST. In order to determine the injection rate a supplementary model of the solenoid injector was built in AVL HYDSIM. A study of rate of heat release and pressure rise into combustion chamber was conducted at single operating point. The engine effective power was taken into consideration as well. The results revealed that pre-injection strategy is a promising approach for reducing the rate of heat released and the engine noise at low speed and load. However, a precise control of pre-injected mass and injection timing has to be realised by engine control system.

The publication describes the properties of isopropyl alcohol and is exploring the possibility of its use as an additive to diesel fuel. Experimental results from operation of the diesel engine with 15% isopropyl alcohol are shown. The advantages of using a 15%- mixture of isopropyl alcohol and standard diesel fuel are presented here. The main physicochemical parameters of the isopropyl alcohol are also shown as well as the specification of the used diesel fuel. The specifications of the test engine are given here in detail. The experimental results are presented in both tabular and graphical form. The main economical parameters are show as a function of the load characteristics. Graphical functions proving the smoke density reduction as a function of the load characteristics, air-fuel ratio and multi- parameter characteristics are also presented. The smoke reduction is observed in exhaust gas of the diesel engine.

This paper presents the results of an analytical study for optimisation of the full-load operation of a compression ignition internal combustion engine with common rail fuel system. The model is made with the aid of the software simulation package Advanced Simulation Tools by AVL List GmbH. An existing engine is used as a prototype of the model – a PSA-manufactured DW10BTED4. The received characteristics from the performance are compared with the manufacturer data. A possible range of model improvements are also presented in the paper.

The article presents a modern approach for studying the combustion process in the DI Diesel engines developed for passenger car. The mixing controlled combustion model has been chosen for estimation the rate of heat released in the combustion chamber as well as the Arrhenius equation was used for ignition delay determination. The injection rate was calculated by means of constant injection pressure as well. Zero dimensional thermodynamic models have been used for estimation the in-cylinder parameters. All of the models were implemented as a computational code in Matlab. Finally, in-cylinder parameters variation such as pressure, temperature, rate of heat released etc., were studied at two engine operating points.