DYNAMIC BEHAVIOR OF TWO ELASTICALLY CONNECTED NANOBEAMS UNDER A WHITE NOISE PROCESS

This paper investigates the almost-sure and moment stability of a double nanobeam system under stochastic compressive axial loading. By means of the Lyapunov exponent and the moment Lyapunov exponent method the stochastic stability of the nano system is analyzed for different system parameters under an axial load modeled as a wideband white noise process. The method of regular perturbation is used to determine the explicit asymptotic expressions for these exponents in the presence of small intensity noises

Combustion characteristics of several types of biofuel in a diesel engine

Interesovanje za alternativna goriva koja bi se koristila za pogon motora sus je veoma veliko u čitavom svetu. Zato se istraživanja vezana za ovu problematiku vrše u mnogim vodećim svetskim laboratorijama za motore. Razlog ovog interesovanja su dostupnost ovakvih goriva, povoljne ekološke karakteristike i pozitivan uticaj na ekonomije zemalja koje ovakva goriva mogu da proizvode. U predmetnom radu se daje deo rezulta veoma kompleksnih i dugotrajnih istraživanja dinamike procesa sagorevanja kod dizel motora pogonjenog metilestrima biljnih ulja i to otpadnog palminog jestivog ulja, sojinog ulja i ulja uljane repice. Poređenje promena u radnom procesu motora, pre svega procesu sagorevanja, je vršeno pri sinhronizovanom radu motora na uobičajenim standardnim dizel gorivom mineralnog porekla. Analizom zakona (toka) sagorevanja svakog pojedinačnog goriva, utvrđeno je da postoje razlike koje nisu velikog karaktera, iz čega se može zaključiti da su goriva proizvedena iz biljnih ulja, a po važećem standardu, veoma kvalitetna goriva za pogon dizel motora. Ovo daje mogućnost naročito poljoprivrednim gazdinstvima da samostalno proizvode deo potrebnog goriva sa sopstvenih zemljišnih parcela uz uslov da poseduju odgovarajuću opremu za proizvodnju biodizela.Alternative propulsion fuels for diesel engines were highlights for a variety of research activities within a large number of R&D labs in the world. Curiosity, as well as basic interest in alternative fuel has been immense because of its reproducibility, renewability, as well as good ecological characteristics. Another reason for this interest is a favorable impact on the economies of the countries engaged in their production, by processing that kind of bio fuel. This paper presents the results of testing and research of the three types of alternative fuel gained from bio oil. Analyses and comparison of the dynamics of combustion process of these alternative fuels were done in relation to the reference diesel fuel. Burning process of methyl esters rapeseed (RME100), soya oil (SME100), waste cooking palm oil (PME100), as well as of regular Euro diesel fuel were investigated. It was found that these fuels were highly usable in diesel engines if they had been produced according to a proper standard procedure under standard EN 14214. The application of bio fuel is also very interesting for the propulsion of agricultural engines and machinery, because it enables the individual farming of bio fuel products necessary for the appropriate own machinery

Spatial flow velocity distribution around an inlet port/valve annulus

An experimental investigation of the airflow through inlet port of a standard production direct injection diesel engine is presented. The investigation comprises mass flow rate and pressure drop measurements at fixed valve lifts, and spatial distributions of mean and r.m.s. velocity components around the port/valve annulus measured under steady flow conditions by special designed miniature hot-wire anemometer X probe. The results show that the velocity field is distributed non-uniformly across the valve gap and around valve periphery. Nonuniformity is more expressed at higher valve lifts. Flow instability in a jet leaving the port (jet flapping) is also evident since the skewness and kurtosis of the velocity probability distribution function depart from the Gaussian form. The presented experimental method, based on the application of miniature multiple hot-wire probes, makes possible investigation of flow performances of an inlet port and poppet valve assembly of a production engine head without any modification for ensuring an optical access within the port/cylinder