A tire pyrolysis oil (TPO) produced from waste tires was tested in a 6-cylinder, compression ignition, turbocharged, 6.9 L heavy-duty engine. The thermodynamic parameters, engine performance and exhaust emissions of the engine fuelled with TPO were benchmarked against results of the engine fuelled with commercial diesel fuel (D2). Experiments were conducted in two operating modes, with and without intercooler, at two different engine speeds and at various loads. Impact of thermodynamic and engine performance parameters on combustion process were systematically analyzed in terms of cause and effect phenomena through mechanisms initiated by the fuel properties. The original contribution of this analysis arises from holistic assessment of combustion phenomena, engine performance and emission characterization of a modern turbocharged CI engine fuelled by the pure TPO. Results indicate that TPO can be efficiently used in turbocharged non-intercooled CI engines at high loads, which opens its use in power generation.
COBISS.SI-ID: 13902363
The paper presents a computationally efficient method for solving the time dependent diffusion equation in a granule of the Li-ion battery's granular solid electrode. The method, called Discrete Temporal Convolution method (DTC), is based on a discrete temporal convolution of the analytical solution of the step function boundary value problem. This approach enables modelling concentration distribution in the granular particles for arbitrary time dependent exchange fluxes that do not need to be known a priori. It is demonstrated in the paper that the proposed method features faster computational times than finite volume/difference methods and Padé approximation at the same accuracy of the results. It is also demonstrated that all three addressed methods feature higher accuracy compared to the quasi-steady polynomial approaches when applied to simulate the current densities variations typical for mobile/automotive applications. The proposed approach can thus be considered as one of the key innovative methods enabling real-time capability of the multi particle electrochemical battery models featuring spatial and temporal resolved particle concentration profiles.
COBISS.SI-ID: 13847835
This paper presents a study of heat transfer in a rotating axial rotor. The study was done on the basis of computational fluid dynamics simulations and validated with an infrared thermocamera experimental setup. The influence of full turbulence vs. Menterʼs boundary layer method was studied in terms of heat transfer and flow phenomena. Additionally it was found out that a thin paint layer has a major influence on heat transfer phenomena and acts as insulation. For comparison of numerical results with experimental, a model of the actual rotor was established. Results were found to be in good agreement, so the effect of rotation on heat transfer was studied. Results are presented in terms of Nusselt number distribution and an empirical model of heat transfer.
COBISS.SI-ID: 13861403
Fan/impact mills are commonly applied in the grinding and dilute-pneumatic transportation of lignite or brown coals with high moisture contents to the furnaces in large steam boilers. Each of the two to eight mills feeds pulverized coal into two or more burner nozzles. An online detection of the pulverized-coal mass flow distribution among the burners is vital for the control of the combustion process. Knowing the distribution, measures for the redistribution of the coal or, alternatively, for the adjustment of the combustion air flow according to the actual distribution can be employed. Determining the characteristics of a gas-solid two-phase flow using an electrostatic principle is a promising online method of measurement because it is robust and inexpensive. Furthermore, due to their better spatial sensitivity, rod sensors are more suitable for large rectangular ducts related to fan/impact mills than ring-, pin-, or arc-shaped sensors. Sets of 1-D and 2-D electrostatic sensor arrays with a corresponding data acquisition system were employed to determine the mass flow distribution in the cross section of the duct that feeds the pulverized lignite to the four burner nozzles. Various operating regimes for the fan/impact mill were tested. The time series of the signals from the electrostatic sensors were analyzed statistically. It was shown that the skewness, kurtosis, and autocorrelation time delay at the characteristic value can indicate different grinding qualities of the coal.
COBISS.SI-ID: 14196507
Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e. below the acoustic driving frequency. The term "acoustic supercavitation" was proposed for this type of cavitation Žnidarčič et al. (2014) [1]. We tested several established hydrodynamic cavitation models on this problem, but none of them was able to correctly predict the flow features. As a specific characteristic of such acoustic cavitation problems lies in the rapidly changing driving pressures, we present an improved approach to cavitation modeling, which does not neglect the second derivatives in the Rayleigh-Plesset equation. Comparison with measurements of acoustic supercavitation at an ultrasonic horn of 20kHz frequency revealed a good agreement in terms of cavity dynamics, cavity volume and emitted pressure pulsations. The newly developed cavitation model is particularly suited for simulation of cavitating flow in highly fluctuating driving pressure fields.
COBISS.SI-ID: 13644827