Paolo Boncinelli

Real Gas Effects in Turbomachinery Flows: A Computational Fluid Dynamics Model for Fast Computations

A numerical model was included in a three-dimensional viscous solver to account for real gas effects in the compressible Reynolds averaged Navier-Stokes (RANS) equations. The behavior of real gases is reproduced by using gas property tables. The method consists of a local fitting of gas data to provide the thermodynamic property required by the solver in each solution step. This approach presents several characteristics which make it attractive as a design tool for industrial applications. First of all, the implementation of the method in the solver is simple and straightforward, since it does not require relevant changes in the solver structure. Moreover, it is based on a low-computational-cost algorithm, which prevents a considerable increase in the overall computational time. Finally, the approach is completely general, since it allows one to handle any type of gas, gas mixture or steam over a wide operative range. In this work a detailed description of the model is provided. In addition, some examples are presented in which the model is applied to the thermo-fluid-dynamic analysis of industrial turbomachines.

Olive Oil Production Chain

In this chapter, Multicriteria Analysis (MCA) and Life Cycle Assessment (LCA) methodologies are applied to investigate a number of aspects of the extra-virgin olive oil production chain. The analysis starts from the definition of a number of possible scenarios concerning all phases of the chain: olive grove characteristics, management and productivity; olive harvesting and transport to the extraction plant (logistics); extraction plant configuration and management. Scenarios are arranged in order to define different configurations of the whole chain. The MCA methodology is then applied to select the most suitable scenario arrangements, according to a number of requirements which are set in advance: main goals to be accomplished, main benefits and drawbacks, a number of evaluation criteria for scenario selection, outcomes and/or scores associated with each scenario for each evaluation criterion. Chain configurations which achieve higher scores are subsequently considered for further evaluation by means of LCA, exploiting the GEMIS software. Results in terms of CO2eq emissions and CER associated with each chain are eventually reported and discussed.

Bowl-Type Diffusers for Low Specific-Speed Pumps: An Industrial Application

In this paper, the aerodynamic design of a bowl-type diffuser for a low specific-speed pump is presented and described in detail. The main goal was to achieve an optimal configuration in terms of diffuser recovery capacity and stage aerodynamic efficiency, while satisfying severe constraints concerning stage size and multistage feasibility. Both geometrical parametrization tools and a fully viscous three-dimensional numerical solver were exploited in the design process. The geometrical parametrization allowed one to control and modify the geometry of the component by changing a limited number of parameters. Computational fluid dynamics analysis was exploited to assess the effectiveness of the geometrical modifications on the performance and to identify critical problems. A number of aerodynamic 1D coefficients with simple physical meanings were also introduced and used as a support to the design to synthesize the main feature of the strongly three-dimensional flow evolving in the component. As a result, a new stage configuration was developed according to the imposed constraints, whose performance is at the same level as standard pumps of the same class.

On Effects of Impeller-Diffuser Interaction in the “Radiver”' Centrifugal Compressor

In the present work, effects of impeller-diffuser interaction were investigated in the “Radiver” centrifugal compressor stage exploiting CFD techniques. Two diffuser geometries, differing in the radial gap between impeller exit and diffuser inlet, were analyzed by means of both steady and unsteady computations at two different operating conditions. Physical mechanisms by which interaction affects the flow field were identified and discussed. Flow unsteadiness was found to marginally affect the stage performance, but to have a relevant impact on the flow field.Copyright

Real Gas Effects in Turbomachinery Flows: A CFD Model for Fast Computations

A numerical model was included in a three-dimensional viscous solver to account for real gas effects in the compressible Reynolds Averaged Navier-Stokes (RANS) equations. The behavior of real gases is reproduced by using gas property tables. The method consists of a local fitting of gas data to provide the thermodynamic property required by the solver in each solution step. This approach presents several characteristics which make it attractive as a design tool for industrial applications. First of all, the implementation of the method in the solver is simple and straightforward, since it does not require relevant changes in the solver structure. Moreover, it is based on a low-computational-cost algorithm, which prevents a considerable increase in the overall computational time. Finally, the approach is completely general, since it allows one to handle any type of gas, gas mixture or steam over a wide operative range. In this work a detailed description of the model is provided. In addition, some examples are presented in which the model is applied to the thermo-fluid-dynamic analysis of industrial turbomachines.© 2003 ASME

Agricultural and Forestry Mechanization

Wood biomass for energy production, used by 50% of the world’s population, represents an important alternative to other non-renewable energy sources even in industrialized countries. The correctly planned management of wood biomass production could make it a valid alternative energy solution to traditional fossil fuels, since it is a local and widely available resource, it has an almost carbon neutral production balance and its exploitation could trigger processes of environmental and social improvement. However, efficient energy transformation that is environmentally and economically sustainable requires the realization of optimized chains in which each phase is rationally planned. This study was carried out using multicriteria analysis methodology in order to assess the suitability of using this renewable source of energy, taking into account the energy, emissions and economic factors as well as the technologies used. The study took into account the costs of cultivation, harvesting, transportation and transformation of the biomass obtained from short to medium rotation coppice, as well as from salvaged biomass chains. The methodology was applied referring to Italy, making the relevant adjustments.

Oil Palm Farming Chain

This chapter presents an example of Multicriteria analysis (MCA) application and consequent life cycle assessment (LCA). The methodologies are applied to a case in which a number of possibilities must be evaluated for installing an oil palm plantation. The example is not based on a real case but on a hypothetical one in order to show a wider range of variables. The subsequent steps are presented and discussed throughout following some realistic assumptions and a framework is suggested to the reader in order to allow him to adapt it to specific cases and needs. MCA and LCA results are discussed and compared on a methodological point of view.

Energetic Use of Biomass and Biofuels

Olive oil production is one of the most important activities of the agricultural sector in the Mediterranean region. Considering that olive-groves significantly characterise the landscape and that olive pruning requires large labour input and costs, farmers have to organize the pruning operation assuring economical sustainability. For this reason the energetic use of olive pruning has been adopted in many farms, even if the collection and treatment of the residues could imply additional costs in field operations. Therefore, in order to analyze the pros and cons of different alternatives for olive pruning management, a methodological approach able to take into account both the economical and environmental aspects must be implemented. In this chapter, 35 possible scenarios are illustrated and evaluated: based on the chosen criteria, solutions which present limited fuel consumptions, reduced transports and the biomass use in small- or medium-sized combustion plants, are preferred.

CFD Applications to Industrial Centrifugal Compressor Design

The aerodynamic redesign of an industrial transonic centrifugal impeller by means of CFD techniques is presented here. The computational procedure was validated by comparing numerical predictions of efficiency and work input coefficient to data from experimental tests on two different typologies of impellers: a low flow coefficient subsonic radial impeller and a high flow coefficient one. Three–dimensional, fully viscous computations were used to investigate the transonic impeller aerodynamic performance in terms of both the characteristic curves and details of the flow structure, suggesting possible improvements in the design. In order to standardize the redesign process of 3D impellers, a number of geometrical parameters, capable of describing the main features of the geometry, were identified. The original configuration was modified by varying the values of such parameters, and the impact of changes was assessed by means of 3D computations. As a result, the designer would be able to recognize which parameters have greater influence, and understand the physical effect of each change. This made it possible to establish some design rules to be exploited in future design processes.Copyright

Turbomachinery Computations on Parallel Computers Using a Multigrid Method

The parallelization of a multigrid solver for the quasi-3D and 3D RANS equations was implemented on a distributed shared memory parallel-architectured computer by the insertion of compiler directives. Tests performed by varying the number of blocks are presented in terms of speed-up and percentage of achieved parallelism. Typical time-consuming industrial applications which can benefit of this approach are discussed.