Contents of Journal of Mechanical Engineering 59, 5–6 (2008)

ŠOOŠ, Ľ.: Contribution to the research of static and dynamic 
properties of CNC turning machine                                       231

ARSLAN, S., YILDIZ, E., AYBEK, A.: Assessing an LPG engine 
performance through mathematical modelling and simulation               241

SHARMA, V. S., DOGRA, M., BEDI, R., SHARMA, P.: Regression 
versus neuro-fuzzy model: A comparison for tool wear estimation         259

BASHRIA, A. A. Y., ADAM, N. M.: Performance analysis of single 
and double passes flat plate collector with and without porous 
media                                                                   275

DANIŽ, M., KÁLMAN, P., POLÓNI, M.: Simulation of parameters 
of internal combustion engines                                          291

MUŠKÁT, P., URBAN, F., PULMANN, M.: Measurements on the physical 
model of the nuclear reactor fuel assembly                              305                                          

Spindle headstock (SH) of the machine tools plays a major role in the fulfilling the required working accuracy and productivity. Radial ball bearings with angular contact are still more and more applied in an arrangement. The spindle-housing system (SHS) complex analysis is very difficult and complicated. The analysis requires deep knowledge of mathematics, mechanics, machine parts, elastohydrodynamic theory, rolling housing technique and also programming skills. Software package (SW) – Spindle Headstock, Rel. 2.8 – carried out at the Department of Production Engineering has been applied for designing of the precise accuracy running spindle onto the lathe SBL 500 CNC.

The objective of this study was to use a mathematical model to carry out the cycle analysis of a four-stroke, four-cylinder gasoline engine equipped with LPG system and to try to approximate the true engine power by using the postulated model. Temperature, pressure, work, and power were determined through simulation for the maximum torque rating of 3000 rpm. The values of experimental engine power and the calculated power were 36.3 kW, with about 1% error. Power was calculated at 2000, 2500 and 5500 rpm to assess the usefulness of the model in estimation of the true engine power, too. Error varied between 2 to 3.7% at these engine speeds, implying the need for further development in the combustion model and in the simulation code for more accurate prediction of the true engine power.

To improve the overall efficiency of turning, it is necessary to have a complete process understanding. To this end, a great deal of research has been performed in order to quantify the effect of various cutting parameters on tool wear. It is impossible to find all of the variables that impact tool wear in turning. This paper presents the experimental investigation of machining Grey Cast Iron (GCI) with uncoated carbide tools. Two models are developed for tool wear estimation, the first model is regression based and the second one is neuro-fuzzy based. These models are capable of estimating the wear rate at different cutting conditions. The results obtained by both the models are compared with the actual experimental results. Finally it was observed that both the models are capable of predicting tool wear with good accuracy but the regression model performed marginally better than the neuro-fuzzy model.

This study involves a model to investigate the effect of mass flow, channel depth and collector length on the thermal performance and pressure drop through solar collectors by using a developed internet based mathematical modelling. The chosen development software tool is Dreamweaver combined with the Active Server Pages (ASP) as an extension environment and VBScript as scripting language. The developed program is capable of handling ambient conditions, collector characteristics, and material thermal properties. The criteria for solar systems in Malaysia were used as an input in the program to simulate the performance of the solar system. The solution procedure is performed for flat plate collector in single and double flow mode. It is concluded that the increase of the thermal efficiency is 10–12% for double flow when compared with single flow, and 8% after using porous media.

The paper deals with numerical simulation of parameters of internal combustion engines. There are shown some virtual models of internal combustion engines that were made at our institute. For simulating the engine processes, especially gas flow in the pipe system, the Lotus Engine Simulation program (LES) has been used by courtesy of Lotus Engineering, UK. The Lotus Engine Simulation program is capable of modelling the combustion and gas flow processes, computing the indicated and brake parameters while considering the influence of the heat transfer and the friction phenomena. Lotus Engine Simulation program represents a powerful tool for optimisation of engine dynamic parameters and processes. In our case, it has been used for comparison of computed values with experimentally measured ones. Comparison of the values calculated by LES with the experimental data shows a good agreement between computed and measured performance parameters of these engines.

The experimental apparatus of the nuclear reactor fuel assembly model was constructed and installed in the laboratory of the Institute of the Thermal Power Engineering of the Slovak University of Technology in Bratislava.

Extensive tests, oriented on the velocity and temperature profiles at the fuel assembly outflow were done with aim to receive the data for improving the computational apparatus for the flow modelling. Some examples of the results are included in this paper.