This article presents results of the free surface flow around ship hull on two different types of computational grid. Each type of mentioned grid has its own advantages and disadvantages in particular cases, mostly in one phase simulation. Omitting cases with capitation, there is no free surface involved in one phase simulation. Multiphase simulations are crucial in the ship design process and optimization. Recreating free surface on the triangular mesh causes difficulties, in contrast to the hexahedral meshes, where calculated surface is more aligned to the physical border of the fluids. In this paper, results from the triangular mesh were compared to results from hexahedral mesh. Conclusions about triangular meshes in two phase simulation are presented. The computational fluid dynamic toolbox OpenFOAM is used to perform calculations of the total resistance of work boat in calm water.
This paper due to determine an aerodynamic drag for different ways of tarpaulin fixation, specifically tarpaulin tension and disposition on platform-type body of a HDV. More positions of the tarpaulin were investigated. Determination of the resistances was done by coast down test of the vehicle according to Slovakian technical standard (STN). The aerodynamic drag was calculated from actual vehicle deceleration during the coast down test from the actual velocity changes. The vehicle actual velocity was measured by GPS logging device. Results are values of resistance, which affect the vehicle and their sum represents the actual engine power needed for vehicles driving.
There are also the vehicles among the other vehicles in road traffic that have been modified without being authorised by their producer. These also include modifications such as structural modifications in the vehicle break system. Besides a brake system of road motor vehicles is one of the main factors influencing the active safety of vehicles. The design of the brake system, its technical condition and additional intervention in its construction may have a positive as well as negative impact on the braking distance length and the value of the mean braking deceleration achieved. The paper focuses on the influence of the brake disc diameter of the front axle on the achieved value of the mean braking deceleration and the braking distance length, while the braking system has been modified for several times without being approved by car manufacturer. The introductory part of the paper describes the braking distance sections and it also explains the term of mean braking deceleration. The following part of the paper deals with the measurement methodology, measuring equipment and the vehicle used during the measurements as well as procedures employed. The results obtained from the measurements are processed and presented in tables and also in graphs for greater clarity. The final part of the paper summarizes and evaluates the measured results. The importance of the paper lies in quantification of the influence of brake discs with different diameters on the vehicle active safety in the case of a particular vehicle.
Vegetable oil based fuels significantly enable reducing the costs of fuel purchased. CI engine vehicles with rotary and inline injection pump can be fuelled by vegetable oil based fuels instead of being fuelled by diesel. This is very common, since their price is lower in comparison with diesel. The article focuses on the impact of using fuels made from vegetable oil on selected vehicle characteristics in particular conditions. It includes the measurements of the impact of using fuels such as FAME, fresh oil and used oil on the engine smoke opacity, content of selected emissions in the exhaust gases as well as on the engine power and torque’s course. The measurement results are mutually compared with the results measured when using diesel. In order to secure the measurements to be repeatable, they were performed in laboratory at the cylinder test station MAHA MSR 1050. The vehicle tested during its last 100,000 kilometres driven by vegetable oil based fuel has been selected for these measurements. Therefore, by these measurements, it was also possible to assume partially the impact of long-term using aforesaid fuels on selected vehicle characteristics.
The article deals with the problem of electric power production in terms of environmental impact, in particular the energy efficiency of its production to utilize primary sources. The efficiency of its production directly depends on the composition of primary sources and technologies used. Difference in efficiency by converting various forms of energy into electrical power and their ratio in the use directly affect the resulting efficiency, production of emissions and thus the environmental impact. Electric traction, its production, is burdened less efficient than other types of tractions used in transport, but at the final reconciliation of their consumption in vehicles, this difference decreases or delays because the vehicles themselves work with different conversion efficiency of its traction on mechanical work, vehicle driving.