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  • Author: Mirosław Kowalski x
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Abstract

The article analyses the impact of emulsified fuel, containing H2O2 hydrogen peroxide, on the emissions of nitrogen oxides and diesel engine smoke. The process of forming toxic components in exhaust gases of reciprocating engines during the engine operation, and the relationship that specifies the hydrogen peroxide decomposition process were presented. The research was carried out with the use of fuel containing 30%, 20% and 10% of hydrogen peroxide. The concentration courses of the nitric oxide (NO) and nitrogen oxides (NOx), as well as the (CO) carbon monoxide concentration and (S) engine smoke courses were shown separately for the external characteristics of the engine. Finally, the importance of knowledge related to the mechanisms of generation of toxic components in exhaust gases in the reciprocating engines was emphasised.

Statistical Verification of Experimental Tests to Determine Geographical Positions of Objects

The article describes statistical methods of verification of measurements taken to determine geographical position of a single soldier on a battlefield using the latest GPS satellite techniques. The GPS system allows of considerable improvement in effectiveness of military operations owing to its capabilities to provide precise location of either the whole organizational unit or a single soldier, and precise time. What has been gained from experimental tests are sets of tables with, among other elements, geographic coordinates to express location (longitude and latitude), and altitude.

Abstract

The research paper discusses the advantages of using compressor downstream air partial bleed and supplying it downstream of the turbine, which was applied in a prototype of a “bypass” turbojet engine. The impact of such a solution on the value of achieved basic operating parameters of the engine was described, i.e., unit thrust and unit power consumption. The presented attempt to compare these parameters with the parameters achieved for a turbojet, single flow engine is very important; in the first case without air bleed, and in the second, with air bleed to the environment and with the parameters of a turbojet, turbofan engine with a jet mixer.

Abstract

Certain results of the comparative studies of the high-speed Diesel engine V-12 of the “W” series were presented in the article. The engine was modernised in regard of possibilities to achieve better performances at specific fuel consumption, smaller exhaust emission, smaller scavenge, lower noise and better thermal stability. The subject of this work is the piston cast of novel composite silumin. The development of novel composite silumin (aluminium-silicon alloy), which contains a little more Copper and Nickel, and the introduction of novel alloyed elements, such as Chromium, Molybdenum, Tungsten, increases the strength of the alloy and its thermal stability during successive heating and cooling. The pistons made of this alloy may have a little bigger outside diameter than the pistons made of PA-12 standard alloy, and a smaller clearance between the piston and cylinder liner. The pistons made of standard and novel alloy were mounted successively in the “W” engine. The full load and part load curves were determined. The lubrication oil consumption, fuel consumption, exhaust emission, blow-by and noise were determined too. The article presents the results of the above-mentioned research. The novel composite alloy enables further engine modernization because the engine should operate at higher pressure and temperature in the combustion chamber.

Abstract

The conducted tests were aimed at determination of the drop diameters and shaping of the velocity field at different configurations of the test injector. The test results allowed defining the relationship between the injector configuration and the distribution of velocities and dimensions of drops in the fuel stream. The effect of the fuel viscosity and injection pressure on the dimensions of fuel drop diameters and the distribution of the velocity field of drops in the stream were tested. The tests were carried out on a special test rig with a fixed volume chamber. The measurements were carried out with the use of laser Doppler measurement systems (PDPA, LDV). The tests were conducted for seven different fuel types varying in viscosity and surface tension. In addition, the injection pressure from 50 MPa to 130 MPa was applied. The test results allowed determining the relationship between the injector structure configuration, fuel types and fuel additives, and the distribution of velocity and an atomisation spectrum of drops in the fuel stream, and the air impact on the fuel stream.

Abstract

The article presents the modelling of the combustion process of liquid fuels using professional ANSYS FLUENT software. This program allows modelling the dynamics of compressible and incompressible, laminar and turbulent flows as well as heat exchange phenomena with occurrence and without chemical reactions. The model presented in the article takes into account the influence of the gas phase on the liquid phase during the fuel combustion process. The influence of velocity and pressure of the flowing gas and the type of flow has a significant impact on the combustion of liquid fuels. The developed model is fully reliable and the presented results are consistent with experimental research. The occurrence of a laminar sublayer in a turbulent flow was confirmed, and the thickness of this layer and the turbulent layer significantly influences the course of the combustion process. The use of the flat flow model reflects the basic phenomena occurring during the combustion of liquid fuels under turbulent conditions. The use of the program for flows with different flow velocity profiles is justified. It gives important information about the processes taking place during the combustion of liquid fuels. The results of numerical tests are presented graphically. The article presents graphs of velocity field, absolute pressure, power lines, temperature and density.

Abstract

The article presents the results of the investigations cover novel composite silumins with new alloying additives, such as chromium and molybdenum (not yet used in this type of silumin) and increased content of nickel and copper. The samples strength tests were performed at room temperature (20°C) and at elevated temperatures (up to 350°C), and were carried out using the strength machine, equipped with the special climate chamber. The dimensional stability of the new aluminum alloy was investigated using the precision dilatometer. This device allows one to register and record the sample dimensions as a function of temperature, during sample heating and cooling. During the DTA crystallization process investigations, derivative curves have been determined, that allows the analysis of the solidification process and the analysis of the heat transfer process in the sample structure and phase transformations. In the article shows the derivative curve and representative microstructures, and characteristic temperatures for the conventional AlSi12 alloy and novel composite alloy. All research results indicated that the newly developed composite aluminum alloy has far better parameters than aluminum alloys used previously for pistons of the internal combustion engines.

This article concludes with a summary of the advantages of the new composite alloys.

Abstract

The emulsion is a mixture of two or more insoluble liquids. Microemulsion is the emulsion with particles dimension in a range of one micrometre and smaller. Such a microemulsion of water and diesel fuel will create a novel quality and allows one to simultaneously achieve environmental and economic effects, as well as eliminate the ad-verse impact of normal emulsions, or adverse effects of water injection into the engine intake system or directly into the combustion chamber, as well as the sequential injection of water directly into the combustion chamber. Application of microemulsion of water and diesel to fuel diesel engine positively affects the combustion process through the catalytic impact of microparticles of water, and improves the process of preparation of the microemulsion injection into the combustion chamber as a result of water microparticles’ microexplosions. This article presents the investigation results of an internal combustion engine fuelled by an emulsion of water and diesel fuel and fuelled by emulsion of FAME and water. It therefore seems appropriate to a strong increase in the degree of dispersion of water droplets in the emulsion by applying the methods to obtain the size of water droplets on nanometric range. This should dramatically improve both the stability of emulsion and its influence on the chemical effects of combustion in diesel engine.

Abstract

The article presents theoretical and practical aspects of aircraft reliability and safety of the performance of test flights in the operation process. The selected issues of operation of the means of transport in the aspect of the aircraft reliability, as well as the intensity of damage during the performance of test flights were presented. In short, the rules for operating the aircraft during test flights are described. A brief description of the causes of air crashes during test flights was presented, and the main hazards and risk occurring at the same time were shown. Subsequently, the authors’ methodology including a diagram for studying the aircraft features in terms of aerodynamic characteristics and performance and a model of the maintenance system of aircraft to perform the test flights, were demonstrated. The elements of the decision-making model, developed for this purpose, were briefly presented, showing the required and defined decision variables, constraints and an objective criterion function. The algorithm of the method was presented, and the examples of practical application and graphical data presentation in the DOSPIL application were indicated. The article was concluded with a short summary in which the main effects and directions of further work were presented.

Abstract

The paper analyses the mechanisms of creation of toxic exhaust gases, which mainly derived from inexact fuel metering and improper air-fuel mixture preparation. The paper describes the process of creating toxic components in the exhaust gases of piston engines during engine operation, and impact on the emission of these components determining the composition of the fuel mixture determined equivalence factor Φ. The principal mechanisms of formation of toxic exhaust gases, in particular nitrogen oxides, carbon monoxide and hydrocarbons, and also essential according to create each of toxic exhaust gases are the subject of the paper. Moreover, empirical relationships, by means of which it is possible to determine the time of creation of the individual components of toxic exhaust gases, are presented. For example, one of the mechanisms for prompt formation of nitrogen oxides and hydrocarbons graphic illustration of formation as a function of crank angle is described. At the conclusion, the summary and significance of information on creation mechanisms of toxic components in the exhaust gases of piston engines are presented.