Table of Contents

  • ANALYSIS OF A COMBINED CASE OF INTERNAL AND EXTERNAL RESONANCES FOR A QUADRATIC COUPLED PITCH – ROLL SHIP

    pg(s) 10-1

    In the paper, a two-degrees-of-freedom ship model with quadratic coupled pitch and roll modes under sinusoidal harmonic excitation is considered. A straightforward expansion allows for obtaining both the resonant values of external excitation frequency and one internal resonance. The Multiple Scales method yields the first-order expansions for the special resonant case where the excitation frequency is close to the roll frequency. The time series and the frequency – amplitude curves provided by numerical integration are contrasted with those given by the perturbation technique for different combination of system’s parameters. If the parameters are selected within the pre-ordered range, the results of both methods are in excellent or, at least, in pretty good agreement.

  • STABILITY OF NONLINEAR AUTONOMOUS SYSTEMS WITH TWO DEGREES OF FREEDOM. AN ANALYTICAL STUDY

    pg(s) 14-17

    The Thomson-Tait-Chetayev theorem states that “if a system with an unstable potential energy is stabilized with gyroscopic forces, then this stability is lost after the addition of an arbitrarily small dissipation”. The importance of this property in growing number of physical examples and engineering applications in the practice is not well good unified and understood, i.e. the destabilizing effect of dissipation needs to be compensated in various gyroscopic devices by applying accelerating forces.

    In the present paper an analytical study of the stability behaviour of a specific class of nonlinear autonomous dynamic systems (i.e. RHS of the equations is a square polynomial) with two degrees of freedom is developed. Considering the general case, we find that the system is multi-stationary and has several possible equilibria. The system is investigated with analytical tools coming from Lyapunov-Andronov theory, and our analytical calculations predict that soft (reversible) loss of stability takes place.

  • VEGETABLE OILS AS ALTERNATIVE FUEL FOR NEW GENERATION OF DIESEL ENGINES. A REVIEW

    pg(s) 18-22

    One of the primary incentives for expanding the production and use of biofuels worldwide is the potential environmental benefit that can be obtained from replacing petroleum fuels with fuels derived from renewable biomass resources. The use of straight vegetable oil in diesel engines is one of the available alternatives, but its use in existing vehicles usually requires modification of engine or fuel system components. The increased viscosity, low volatility, and poor cold flow properties of vegetable oils lead to severe engine deposits, injector coking, and piston ring sticking. The paper presents a literature review on vegetable oils as alternative fuel for diesel engines.

  • DETERMINING THE EFFECTS OF CANOLA BIODIESEL ON ENGINE PERFORMANCE AND TORQUE RISE

    pg(s) 23-26

    This study aims to determine the effects of canola biodiesel on engine performance characteristics and torque rise. In the experiments, canola biodiesel (B100) and diesel (B0) were used as fuel with mixtures by introducing canola biodiesel into diesel in proportions of 5% (B5), 10% (B10), 20% (B20), 50% (B50), and 80% (B80). These fuels were tested on an air-cooled direct injection four-cylinder diesel engine. Tests were run based methods indicated by the standard No. TS 1231. According to the results of the study, the engine’s torque rise values for diesel (B0), B5, B10, B20, B50, B80 and biodiesel (B100) fuels were 27%, 26%, 25%, 24%, 23%, 22% and 21% respectively. It was found that the increasing ratio of biodiesel in the mixture reduced the torque rise values. It was observed that the difference between the torque rise values of B5 and B0 were insignificant.

  • VIRTUAL TESTING ACCORDING TO ECE R66 AS A TOOL FOR ESTIMATING PASSENGER COMPARTMENT SAFETY ON A SNOW GROOMER VEHICLE

    pg(s) 3-6

    The concept of virtual testing is generally used method for understanding the structures behavior during loading. It can be used as accurate replacement of real tests only if they are correctly modeled and verified. The regulation UNECE R66 is uniform technical prescription concerning the approval of large passenger vehicles with regard to the strength of their super structure. The rollover test is the basic approval test, but virtual tests can be the adequate testing methods of the physical test. The verified computer simulation according to the regulation can be equivalent approval method. There is a need that snow groomer vehicle sometimes accommodates larger number of people (for sport, work or rescue missions). Because of the terrain those vehicles have to pass, there is significant danger of rollover. So far, there are no regulations for testing of such a superstructure. This paper describes the effort and results in the use of virtual testing according to ECE R66 as a tool for estimating the safety of passengers inside such a vehicle. A computer simulation of a rollover test of the snow groomer vehicle was made. The virtual test was conducted according to the ECE R66 which allows this kind of testing. By following the standard guidelines for computer simulation of a rollover test the vehicle superstructure was analyzed. Series of virtual test were carried for meeting the standard requirements and the customer needs. The final snow groomer superstructure had to undertake serious reinforcement considering the passengers surviving area.

  • 1D SIMULATION AS AN ELEMENT OF AN EFFICIENT METHODOLOGY FOR ENGINE CONCEPT DEVELOPMENT

    pg(s) 31-34

    The development of highly efficient combustion concepts for internal combustion engines requires a suitable development methodology. In recent years, the LEC has created LDM (LEC Development Methodology), which is based on the intensive interaction between simulation and experimental investigations on single cylinder research engines. As new engine concepts are developed, many operating parameters are first defined and optimized with a 1D multicylinder engine model. This model illustrates the full complexity of the engine with its geometry, turbocharging and combustion parameters. The design of experiments (DoE) method is used in connection with 1D simulation to find the optimal engine configuration as well as parameters related to the combustion process, i.e. valve timing, compression ratio, ignition timing, excess air ratio. The maximum engine efficiency is found by taking into account the boundary conditions (brake mean effective pressure, turbocharger efficiency), where NOx level and knock limit are constraints.

  • THE INFLUENCE OF VEHICLE OPERATION ON THE BRAKE FLUID BOILING POINT

    pg(s) 35-37

    The possibility to brake is the most important thing in the road transport safety. The effectiveness of the vehicle braking is influenced by brake fluid state – exactly the water volume share in the fluid. The brake fluid boiling point describes water volume in the fluid. By measuring the boiling point, this paper examines how a boiling point decline is influenced by the vehicle operation.

  • DATABASE DESIGN AT SYNTHESIS OF ELECTROMECHANICAL MODULES

    pg(s) 38-41

    In accordance with the global concepts for machine design based on the modular principle, the main modules, which are the same for the different types of working machines, are the electromechanical modules, also called geared-motor modules. Because of the multivariance of the task for their design, a database containing the technical parameters and characteristics of the main constructive units needs to be build.

  • CONSTRUCTIVE SOLUTIONS TO REDUCE THE NOx AND SOx IN THE MARINE BOILER BURNERS

    pg(s) 7-9

    The modern world is facing two challenges – firstly, the energy crisis related to fuel the other – environmental degradation, especially in the form of air pollution and its consequences – climate change. The regulations demand specifically a significant reduction of sulphur oxide combinations (SOx), carbon dioxide (CO2) and nitrogen oxide combinations (NOx).