Mobility and Vehicle Mechanics

1-14

Authors: Barhm Mohamad

Acoustic simulation methods are being increasingly used for practical exhaust system design of automotive. In many practical applications, the sound source emits, partly, a low frequency sound spectrum comprised of superposed discrete tones and partly, a higher frequency broadband spectrum. The turbulent vortices that develop in the boundary layer between the duct wall and the flowing medium are said to generate a self-excited noise, that noise is broadband character. The self-excitation is enhanced when the flow is disturbed by irregularities in the duct wall. Unsteady compressible fluid flow through a duct is often encountered in many engineering applications and has been investigated by many researchers. When a pressure wave generated inside a duct is discharged from an open end of the duct, an impulsive wave that is usually characterized by high sound pressure level of short duration forms at the vicinity of the exit of the duct. Acoustic simulations solve the equations for motion, mass, momentum, and energy and can be divided into two methods, linear and non-linear. Through that literature review, we can analyse the methods and the latest development done on exhaust systems with regard to acoustic performance. The basic theory behind both approaches is explained as well as a source characterization technique that can be used to link the two methods. Some acoustic software tool has been applied to a variety of exhaust systems.

27-43

Authors: Novak Nikolić, Nebojša Lukić, Nikola Milutinović, Aleksandar Nešović

In this paper the energetic and economic performance assessment of residential application of IC engine based cogeneration system in the Serbian climatic conditions using building energy simulation software was performed. The performance of IC based system was compared with the performance of the two other conventional systems for DHW preparation: gas and electric water heater. Comparing the IC based system with gas water heater the period required to return investment costs of IC engine is relatively high (11.7 years). The main barriers for widespread residential application of IC engine cogeneration system are related to the high capital costs and low price of purchased or sold electricity. In this respect, the investment cost reduction in small scale cogeneration systems has to be achieved. In relation to the current price in Serbia the price of purchased and sold electricity (feed-in tariff) should be increased by 37.5% and 67.5%, respectively, in order to achieve the value of payback period of five years. Comparing the IC based system with electric water heater the application of the IC engine is economically feasible since the payback period amounts 3.42 years. According to the simulation results, the IC engine cogeneration system ensured a primary energy saving of 28.81%.

55-68

Authors: Nina Živanović, Gordana Bogdanović

Oscillations of light wheeled vehicle’s centre of gravity, caused by firing weapon integrated on it, are studied through simulation of its axial and angular displacements. Dynamical model of system with three degrees of freedom is used and mathematical model of oscillations is defined using the Lagrange’s equations of second order. Weapon recoil force and resistance force that causes vehicle’s oscillations is calculated according to the internal ballistics data of integrated weapon and chosen system construction. System of differential equations is numerically solved in MATLAB for real firing conditions and vehicle configuration. Coordinates of weapon mount and elevation and azimuth angles are varied and results are analyzed.