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In this work complete methodology for calculation and analysis of fluid flow in air ducts is presented. In order to minimize outlet pressure drop and to reduce the duct vibrations the plates with airfoil cross sections are added to duct critical zones. It was observed that airfoil stream plates efficiently contribute to outlet pressure drop, duct vibration and noise reduction. Modern methods such as CFD and FEA can be efficiently deployed in numerical treatise of flow and vibration analysis in air ducts.

Honeycomb core composite plates are becoming more important in the construction of primary aerospace structures. Nowadays, these types of materials are used for construction of fuselage skins, central and outer wing boxes, engine tail cones, landing gear doors, command surfaces like spoilers and ailerons etc. To determine the stress strain field in loaded honeycomb plates elastic coefficients are required. In the present work, a method for determining all required elastic coefficients for the core and plates is presented. Using experimentally obtained values for Nomex paper (type 410) and phenolic resin material model is presented and FEA model of composite plate with honeycomb core is created and three point bend test is simulated. Numerically obtained stress and strain values are compared to the experiment. Good agreement between proposed material model and experimentally obtained values is observed.

Pyrolysis process converts biomass into liquid, gaseous and solid fuels. Chemical kinetics play a key role in explaining the characteristics of pyrolysis reactions and developing mathematical models. Many studies have been undertaken to understand the kinetics of biomass pyrolysis; however, due to the heterogeneity of biomass and the complexity of the chemical and physical changes that occur during pyrolysis, it is difficult to develop a simple kinetic model that is applicable in every case. In this review, different methods to describe biomass primary and secondary pyrolysis with different types of kinetic mechanisms are discussed.

The present paper presents the aeroacoustic calculation methodology for the H-Darrieus wind turbine. The CFD analysis, for different wind turbine blades’ angles of attack, coupled with the noise analysis, based on Lighthill and Prudmann models is performed. This type of turbine is of particular interest since it is insensitive to wind direction and can be used in urban areas. In this study commercial software, ANSYS is used for CFD and aeroacoustic analysis. The required turbulent flow field is calculated based on the standard k-ε model, and required model constants are obtained experimentally in a low-Mach number wind tunnel. The noise levels generated by operating turbine are calculated based on Lighthill and Proudman's aeroacoustic theories. It was found that the methodology presented can be efficiently used in noise analysis of vertical axes wind turbines and due to recent strict noise regulations has to be deployed at the early design stages. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to examine the pressure drop caused by placing an airfoil at different angles of attack in the straight part of the rectangular air duct, as the first step of investigating the possibility of using a staggered cascade of airfoils for gradual deflection of the air-flow in radial elbows of an air supply system used in industrial boilers. The initial problem was approached by using the commercial CFD code based on the finite volume method to numerically simulate a 2-D incompressible turbulent flow and by conducting direct experimental measurements in the wind tunnel. The results of CFD simulations have been compared to experimentally measured data for two considered cases of inlet velocities and five different angles of attack. Numerical solutions show an adequate level of agreement with experimental measurements. The obtained results indicate the possibility of using a staggered cascade of airfoils for gradual deflection of the air-flow. [ABSTRACT FROM AUTHOR]

Different mathematical models can describe coal devolatilization as the part of combustion process. Some models are simple, while others are more complex and take into account coal's complexity and heterogeneity of structure. A chemical percolation devolatilization model for describing the devolatilization process of two Serbian lignites from Kostolac and Kolubara open coal mines was studied. Results of the model were compared to devolatilization measurements obtained from two experimental methods -- a wire mesh reactor and thermogravimetric analysis. Two coal samples with four different granulations were investigated for each lignite under different experimental conditions (different maximum temperatures and heating rates). Total volatile yields obtained from the wire mesh reactor and thermogravimetric analysis together with results predicted by the chemical percolation devolatilization model are presented and compared with literature data. For thermogravimetric analysis simulation, the chemical percolation devolatilization model yielded better results in cases where the kinetic parameters obtained under experimental conditions were used rather than kinetic parameters derived from predefined values in the model itself. For wire mesh reactor, the chemical percolation devolatilization model predictions of devolatilization were mixed and were dependent on temperature. [ABSTRACT FROM AUTHOR]

A mathematical model approach was employed to simulate olive pomace gasification in a bubbling fluidized bed reactor. To validate the model a set of gasification experiments were performed in a 250 kW quasi-industrial gasifier. The cold gas efficiency of the th gasifier and tar production were evaluated to assess the energy potential of olive pomace while determining its most suitable end-use applications. A techno-economic analysis addressing the comparison of two different commercially manufactured gasifying unit sizes (100 kW and 1000 kW) and a Monte-Carlo sensitivity analysis were employed to assess both the feasibility of each application size and also foresee the main investment risks in conducting olive pomace gasification in small rural facilities. Olive pomace gasification showed to be more suitable for personal household purposes. The low cold gas efficiency (around 20%) makes this producer gas more appropriate for small cogeneration facilities applications. The use of olive pomace residues in gasification showed viable economic performance in small cogeneration solutions at a scale of 1000 kW for agriculture waste-to-energy recovery in olive oil agriculture cooperatives, while 100 kW showed to be unable to reach an economically sustainable scenario. Final remarks point out that despite the feasibility of the venture at a scale of 1000 kW special concerns must be considered regarding the study attractiveness to potential investors. [ABSTRACT FROM AUTHOR]

This paper is a review of the state-of-the-art of biomass gasification and the future of using biomass in Serbia and it presents researches within the project "The Development of a CHP Plant with Biomass Gasification". The concept of downdraft demonstration unit coupled with gas engine is adopted. Downdraft fixed-bed gasification is generally favored for CHP, owing to the simple and reliable gasifiers and low content of tar and dust in produced gas. The composition and quantity of gas and the amount of air are defined by modeling biomass residues gasification process. The gas (290-400 m³/h for 0.5-0.7 MW biomass input) obtained by gasification at 800 °C with air at atmospheric pressure contains 14% H2, 27% CO, 9% CO2, 2% CH4, and 48% N2, and its net heating value is 4.8-6 MJ/Nm³. The expected gasifier efficiency is up to 80%. The review of the work on biomass gasification has shown that the development of technology has reached the mature stage. There are CHP plants with biomass gasification operating as demonstration plants and several gasification demonstration units are successfully oriented to biofuel production. No attempt has been made here to address the economic feasibility of the system. Economics will be the part of a later work as firmer data are acquired. [ABSTRACT FROM AUTHOR]