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Improved method for shot particle velocity measurement within a shotblasting chamber
Aleš Hribernik, Gorazd Bombek, 2006, izvirni znanstveni članek

Opis: This paper presents the application of two axially-spaced impact detecting sensors for correlation-based shot velocity measurement. The sensors were placed directly into the flow of shot particles for sensing the particles' impact. The implementation of cross-correlation for phase shift determination, however, was not an easy task. Several extensive improvements were necessary, before the original measurement system, already presented in this journal in December 2003, was capable of reliable velocity measurements. This paper presents the development of the system and optimisation of its components. The construction of a sensor built from a small microphone encapsulated in a metal housing and placed under a protective shield was optimised for a high ratio of frontal to side impact signal alteration. High vibration damping was also necessary. It was achieved by the combination of a well-weighted design for supporting elements and by a careful selection of used materials. These measures improved the similarity of the signals generated by the particlesć impact, significantly, and allowed the use of cross-correlation. The accuracy of the obtained results increased drastically by the application of cross-correlation, signal filtering was unnecessary and the signal processing was much faster.
Ključne besede: velocity measurements, shotblasting
Objavljeno: 30.05.2012; Ogledov: 1223; Prenosov: 65
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Non-destructive method for inward leakage detection of a plate evaporator
Aleš Hribernik, 2007, izvirni znanstveni članek

Opis: A new non-destructive method was developed for the detection of refrigerant leakage at an evaporator`s inflow. Nitrogen and oxygen gas were successively blown through the evaporator. A gas analyser was applied at the outflow of the evaporator and the oxygen concentration measured. It was possible to detect any leakage by investigating the oxygen concentration-time history diagram.
Ključne besede: refrigeration, refrigerant leakage, plate evaporator, measurements, non-destructive method
Objavljeno: 31.05.2012; Ogledov: 1026; Prenosov: 49
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Influence of biodiesel fuel on the combustion and emission formation in a direct injection (DI) Diesel engine
Aleš Hribernik, Breda Kegl, 2007, izvirni znanstveni članek

Opis: This paper studies the influence of biodiesel fuel on the combustion and emission formation of two different direct-injected diesel engines, both employing different combustion processes. The research was focused on determining the influence of the specific combustion process on measurement results to ascertain if a generalization of the results is possible or whetherthey have to be interpreted as specific for specific engines. Standard D2 diesel fuel and commercial 100% biodiesel fuel were used. Tests were executed using both fuels under the same conditions, and exhaust emissions andengine performance were measured and compared. In-cylinder pressure was also acquired, and the rate of heat release curves were computed by means of azero-dimensional, one-zone combustion model. Some macroparameters of the combustion process were obtained from the heat-release-rate curves. The results obtained for both engines showed that findings regarding the influenceof biodiesel fuel on the combustion process and emission formation could not be generalized and had to be interpreted as specific for the particular engine.
Ključne besede: internal combustion engines, diesel engines, biodiesel fuel, combustion, emissions
Objavljeno: 31.05.2012; Ogledov: 1001; Prenosov: 43
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Investigation into the effect of different fuels on ignition delay of M-type diesel combustion process
Dževad Bibić, Ivan Filipovič, Aleš Hribernik, Boran Pikula, 2008, izvirni znanstveni članek

Opis: An ignition delay is a very complex process which depends on a great number of parameters. In practice, definition of the ignition delay is based on the use of correlation expressions. However, the correlation expressions have very often limited application field. This paper presents a new correlation which has been developed during the research project on the direct injection M-type diesel engine using both the diesel and biodiesel fuel, as well as different values of a static injection timing. A dynamic start of injection, as well as the ignition delay, is defined in two ways. The first approach is based on measurement of a needle lift, while the second is based on measurement of a fuel pressure before the injector. The latter approach requires calculation of pressure signals delay through the fuel injection system and the variation of a static advance injection angle changing. The start of a combustion and the end of the ignition delay is defined on the basis of measurements of an in-cylinder pressure and its point of separation from a skip-fire pressure trace. The developed correlation gives better prediction of the ignition delay definition for the M-type direct injection diesel engine in the case of diesel and biodiesel fuel use when compared with the classic expression by the other authors available in the literature.
Ključne besede: ignition delay, diesel engine, M-type, biodiesel
Objavljeno: 31.05.2012; Ogledov: 1007; Prenosov: 190
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Performance and exhaust emissions of an indirect-injection (IDI) diesel enginewhen using waste cooking oil as fuel
Aleš Hribernik, Breda Kegl, 2009, izvirni znanstveni članek

Opis: A study was carried out on the influence of waste cooking oil (WCO) and its blends with D2 fuel on the performance, exhaust emissions, combustion and fuel injection processes of an indirect injected diesel engine. Tests were carried out using different fuels, under the same conditions. Exhaust emissions and engine performance were measured and compared. Combustion chamber pressure was also acquired, and the rate of heat-release curves were computed by means of a zero-dimensional one-zone combustion model. Some macro-parameters of the combustion process were obtained from the heat-release-rate curves. The injection system was separated from the engine and tested on a special test bench. The injected fuel quantity was measured, and the injection pressure and injector needle lift time history were acquired. The injection-rate curves were then computed, and some macro-parameters of the injection process were obtained and analyzed.
Ključne besede: diesel engine, waste cooking oil, exhaust emissions
Objavljeno: 31.05.2012; Ogledov: 926; Prenosov: 46
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