Ryoichi S. Amano

Meridional Considerations of the Centrifugal Compressor Development

Centrifugal compressor developments are interested in using optimization procedures that enable compressor high efficiency and wide operating ranges. Recently, high pressure ratio and efficiency of the centrifugal compressors require impeller design to pay attention to both the blade angle distribution and the meridional profile. The geometry of the blades and the meridional profile are very important contributions of compressor performance and structure reliability. This paper presents some recent studies of meridional impacts of the compressor. Studies indicated that the meridional profiles of the impeller impact the overall compressor efficiency and pressure ratio at the same rotational speed. Proper meridional profiles can improve the compressor efficiency and increase the overall pressure ratio at the same blade back curvature.

Numerical Analysis of Heated Soil Vapor Extraction System

An innovative and highly effective technique for remediation of soil has been developed—Heated Soil Vapor Extraction (HSVE), which is one of essential technologies that quickly and effectively remediates soil that is contaminated with organic compounds. The system efficiently uses the principles of heat transfer and diffusion to eliminate organic compounds from the soil. It basically consists of a high temperature heat source and a sink to take away the vaporized compounds in the presence of high temperature in the soil. A numerical study has been conducted to further strengthen the fact that the system is very effective, by actually modeling soil with system. Finite Element Analysis software ANSYS® has been used for the purpose of analysis. Such analysis will help environmental science and give new dimensions to soil remediation processes to clean soil off volatile organic compounds so that they can be carried out quickly, efficiently and economically.© 2002 ASME

Development of Novel Self-Healing Polymer Composites for Use in Wind Turbine Blades

Wind turbine blades undergo fatigue and their performance depletes as time progresses due to the formation of internal cracks. Self-healing in polymers is a unique characteristic used to heal the cracks inherently as they form. In this study, a new method is demonstrated for supplying the monomer (that is quintessential for the healing process) uniformly throughout a fiber reinforced polymer composite. Commercial tubes were used to produce a vascular network for increased accessibility of the healing agent. The tube layouts were varied and their effect on the composite structure was observed. Conventional glass fiber reinforced polymer matrix composites (PMC) without microtubing were tested using dynamic mechanical analysis (DMA) to study the flexural visco–elastic behavior. The vascular network arrangement coupled with DMA data can be used to uniformly supply appropriate amount of healing agent to implement Self-healing in fiber reinforced PMC.

Advances in Horizontal Axis Wind Turbine Blade Designs: Introduction of Slots and Tubercle

Despite being harvested thousands of years ago, wind energy was neglected during the industrial revolution because of the strong dependence on fossil fuels. However, after the alarming decrease in the fossil fuels reserves, many have drawn their attentions back to a renewable energy technology, especially the wind energy. This paper presents some of the new designs that are being tested, including slotted blades and tubercles design models. The experimental results are used to validate the numerical studies that are being conducted parallel to the experiments for better understanding and more detailed results. The new slotted blade design produced more power compared to the straight blade for lower wind speeds, while the tubercle blades showed better power performance in severe wind conditions and a more steady behavior under unsteady and higher wind velocities.

Empirical Design Considerations for Industrial Centrifugal Compressors

Computational Fluid Dynamics (CFD) has been extensively used in centrifugal compressor design. CFD provides further optimisation opportunities for the compressor design rather than designing the centrifugal compressor. The experience-based design process still plays an important role for new compressor developments. The wide variety of design subjects represents a very complex design world for centrifugal compressor designers. Therefore, some basic information for centrifugal design is still very important. The impeller is the key part of the centrifugal stage. Designing a highly efficiency impeller with a wide operation range can ensure overall stage design success. This paper provides some empirical information for designing industrial centrifugal compressors with a focus on the impeller. A ported shroud compressor basic design guideline is also discussed for improving the compressor range.

Study of the Flow in Centrifugal Compressor

Reducing the losses of the tip clearance flow is one of the keys in an unshrouded centrifugal compressor design and development because tip clearances are large in relation to the span of the blades and also centrifugal compressors produce a sufficiently large pressure rise in single stage. This problem is more acute for a low flow high-pressure ratio impeller design. The large tip clearance would cause flow separations, and as a result it would drop both the efficiency and surge margin. Thus a design of a high efficiency and wide operation range low flow coefficient centrifugal compressor is a great challenge. This paper describes a recent development of high efficiency and wide surge margin low flow coefficient centrifugal compressor. A viscous turbomachinery optimal design method developed by the authors for axial flow machine was further extended and used in the centrifugal compressor design. The compressor has three main parts: impeller, a low solidity diffuser and volute. The tip clearance is under a special consideration in this design to allow impeller insensitiveness to the clearance. A patented three-dimensional low solidity diffuser design method is used and applied to this design. The compressor test results demonstrated to be successful to extend the low solidity diffusers to high-pressure ratio compressor. The compressor stage performance showed the total to static efficiency of the compressor being about 85% and stability range over 35%. The test results are in good agreement with the design.

Computer simulation of heated soil vapor extraction system for effective remediation

Soil remediation using heated soil vapor extraction system has gained a significant attention in recent years. The process, developed by Advanced Remedial Technology, comprises of a heat well (heat source) and an extraction well (sink). These wells are pipes, which are implanted in the soil. Heating is accomplished by circulating hot oil through the heat exchange units in heat well. The extraction well has a blower, which sucks the air, and other volatile gases that are evaporated due to heating. An analysis aimed at improving the predictability of the process using numerical tools has been carried out. The key parameters in the process can be identified as the distance between the wells, the temperature that has to be maintained in the heat well and the time required vaporizing the gases and taking them off the soil. These parameters are strongly dependent on the properties of the soil and properties of the chemical pollutants present in the soil. An attempt has been made to model the real process of heating the soil and vaporizing the chemicals in the soil. Such comprehensive analysis is very much helpful in predicting the different parameters as discussed above and result in increase in effectiveness and efficiency of the process.

Design of Solid Rocket Engine

This paper presents both experiment and simulation of alumina molten flow in a solid rocket motor (SRM), when the propellant combusts, the aluminum is oxidized into alumina (Al2O3) which, under the right flow conditions, tends to agglomerate into molten droplets, impinge on the chamber walls, and then flow along the nozzle wall. Such agglomerates can cause erosive damage. The goal of the present study is to characterize the agglomerate flow within the nozzle section by studying the breakup process of a liquid film that flows along the wall of a straight channel while a high-speed gas moves over it. We have used an unsteady-flow Reynolds-Averaged Navier-Stokes code (URANS) to investigate the interaction of the liquid film flow with the gas flow, and analyzed the breakup process for different flow conditions. The rate of the wave breakup was characterized by introducing a breakup-length-scale for various flow conditions based on the Volume Fraction (VF) of the liquid, which is an indicator of a two-phase flow liquid breakup level. A smaller breakup-length-scale means that smaller drops have been created during the breakup process. The study covers the breakup and fluid behaviors based on different gas-liquid momentum flux ratios, different surface tension and viscosity settings, different Ohnesorge numbers (Oh), and different Weber numbers. Both water and molten aluminum flows were considered in the simulation studies. The analysis demonstrates an effective method of correlating the liquid breakup with the main flow conditions in the nozzle channel path.Copyright

Computational Analysis of Scroll Tongue Shapes to Compressor Performance by Using Different Turbulence Models

A scroll is used to collect and transport swirling fluid produced by impeller or diffuser. Scroll or volute is one of the key components of centrifugal compressors. Design of the scroll not only impacts compressor efficiency but also influences operating range of the compressor. In this study, navier-stokes equations combined with both an zero-equation turbulence model and the k-e turbulence model were used to simulate the flows inside a single stage compressor. Detailed flow simulations for a large cut back tongue scroll were presented and discussed. Studies showed that a large cut back rounded tongue scroll provided good operating range without dropping compressor peak efficiency dramatically. The turbulence model influences to the calculation were discussed and some suggestions for scroll flow modeling were made. The numerical results obtained using two turbulence models were compared and showed agreement reasonably well with experiments. Although the k-e model behaves well inside the boundary layer, it was not decisively better than the zero-equation model for the performance predictions.Copyright

Study of Air Bubble Creation for Aerospace Applications

This paper addresses a study of air bubble creation and contact angle effect on bubble size through an investigation by using computational fluid dynamic (CFD), which were validated to experimental results. Contact angle was also investigated for the air, water interface at a rubber surface, Teflon coated surfaces and polytetrafluoroethylene (PTFE).coated surface to find the contact angle for air exiting rubber membrane and the tested coating. The results show very good comparison with the experimental results. Nomenclature qp m . = mass transfer from phase q to phase p (kg/s) pq m . =mass transfer from phase p to phase q (kg/s) th q =volume fraction of one (or more) of the phases (m3) q Sα =source term f U =volume flux through the face, based on normal velocity (m3/s) V =volume of cell (m3) Symbols q α =face value of the th q volume ρ =Density (kg/m3) �0 = equilibrium contact angle Superscripts