Increasing rate of demanding biodiesel as alternative energy resource, persuade researchers to investigate engine performance of biodiesel-fueled engines, which are highly influenced by ignition delay (ID) and combustion characteristics of such a fuel. This review article introduces a literature review on ignition delay (ID) and combustion characteristics of diesel engine fueled with biodiesel. Slightly difference between combustion characteristics of bio fueled engine and petroleum diesel one recognized as result of carried out investigations. Early start of combustion (SOC) and shorter ID of biodiesel comparing to diesel is reported by most of investigations. Lower compressibility, higher Cetane Number (CN) and fatty acid composition of biodiesel have been recognized as the principle elements of early SOC and shorter ID. It is also revealed that heat release rate (HRR) of biodiesel comparing to diesel is slightly lower because of lower calorific value, shorter ID and higher viscosity.
This paper deals with numerical modeling of water flow which is generated by the break of a dam. The problem is solved by applying a new Incompressible Smoothed Particle Hydrodynamics (ISPH) algorithm based on projection method. The proposed ISPH model has two steps. In the first step, the incompressibility of fluid is maintained regarding to the changes of intermediate and initial particles densities at the first half-time step (stability step). In the second step, by computing the divergence of the intermediate secondary velocity at the second half-time step (accuracy step), the incompressibility is satisfied completely. In fact, by using this method both stability and accuracy are increased. The simulation illustrates the formation and subsequent propagation of a wave over the horizontal plane. It is shown that the model predictions compare well with experimental data.
Turbulent Schmidt number as an important parameter in computational fluid dynamic (CFD) simulations is strongly dependent on height, whereas it is mostly considered to be constant in the literature. This paper presents a new variable turbulent Schmidt number formulation which can calculate the relative concentrations (RCs) in neutral atmospheric conditions more accurately. To achieve this aim, RCs from continuous releases are calculated in different distances by the analytical Gaussian plume mode. CFD simulations are carried out for single stack dispersion on a flat terrain surface and an inverse procedure is then applied so that different turbulent Schmidt numbers are used as inputs to determine the RCs to select the “best-fit” turbulent Schmidt number value. This process is continued for different heights to fit a curve to obtain the new formulation for turbulent Schmidt number varying with height. The values are compared with experimental results. The comparison indicates that the new formulation for turbulent Schmidt number is more accurate and reliable than previous research works.
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