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[en] Hydro-Quebec has been using CFD to analyze the performance of its existing turbines for many years. Most of those analyses are based on the measurement of a single runner blade. However, due to manufacturing techniques, in-situ modifications or repairs, there are often small differences between individual blades of the same runner. The impact of this non uniformity was not known thus far and was often assumed to be negligible given the size of the runner. This paper highlights the impact of such differences by presenting the CFD analysis of various blades measured on the same runner. Two different geometries are used for demonstration: the AxialT model propeller and a 50-MW Francis turbine. In both cases, about 50% of the blades could not be considered as representative of the whole turbine and using them could lead to wrong conclusions regarding the turbine performance.
[en] The Diesel refrigeration cycle using an ideal quantum gas as the working substance is called quantum Diesel refrigeration cycle, which is different from Carnot, Ericsson, Brayton, Otto and Stirling refrigeration cycles. For ideal quantum gases, a corrected equation of state, which considers the quantum behavior of gas particles, is used instead of the classical one. The purpose of this paper is to investigate the effect of quantum gas as the working substance on the performance of a quantum Diesel refrigeration cycle. It is found that coefficients of performance of the cycle are not affected by the quantum degeneracy of the working substance, which is the same as that of the classical Diesel refrigeration cycle. However, the refrigeration load is different from those of the classical Diesel refrigeration cycle. Lastly, the influence of the quantum degeneracy on the performance characteristics of the quantum Diesel refrigeration cycle operated in different temperature regions is discussed
[en] This paper describes a new ejector refrigeration system with mechanical subcooling which uses an auxiliary liquid-gas ejector to enhance subcooling for the refrigerant from condenser. The new system can have larger subcooling degree when circulating pump consumes a little more power compared with conventional ejector refrigeration system. Based on the built mathematical model, the performance of the new ejector refrigeration system was discussed and compared with that of a conventional ejector refrigeration system for refrigerant R142b. Theoretical analyzing results show that the new system can efficiently improve the coefficient of performance (COP) of ejector refrigeration
[en] This paper presents a general solution to the material performance index for the bending strength design of beams. In general, the performance index for strength design is ρfq/ρ where σf is the material strength, ρ is the material density and q is a function of the direction of scaling. Previous studies have only solved q for three particular cases: proportional scaling of width and height (q=2/3), constrained height (q=1) and constrained width (q=1/2). This paper presents a general solution to the exponent q for any arbitrary direction of scaling. The index is used to produce performance maps that rank relative material performance for particular design cases. The performance index and the performance maps are applied to a design case study
[en] An irreversible cycle model of the quantum refrigeration cycle using an ideal Fermi gas as the working substance is established. The cycle consists of two adiabatic and two isobaric processes and consequently may be simply referred to as the Fermi Brayton refrigeration cycle. The performance of the cycle is investigated, based on the equation of state of an ideal Fermi gas. Expressions for several important performance parameters, such as the coefficient of performance, work input and refrigeration load, are derived. The influence of the quantum degeneracy of the Fermi gas and the irreversibility in the cycle on the performance of the Fermi Brayton refrigeration cycle is analysed. The minimum pressure ratio of the cycle is determined. The optimally operating problems of the cycle and several special cases are discussed in detail. The results obtained here are general and may reveal the general performance characteristics of the Fermi Brayton refrigeration cycle
[en] The performance of refrigerator compressor has a significant influence on the coefficient of performance of the refrigerator. In order to find out the main cause for the variation of the performance, this paper presents a three-dimensional fluid structure interaction (FSI) model of the refrigerator compressor and an experimental investigation to verify the model. To record the p-V indicator diagram, a refrigerator compressor was modified and the pressure sensor was installed. Based on the FSI model, the variation of pressure in the cylinder that influenced the performance of compressor was identified by varying working condition, rotating speed and refrigerant. The FSI model and result could provide useful information for both performance testing and optimization of compressor performance. (paper)
[en] A simulation approach is described for testing the performance of uncertainty calculations based on the Guide to the Expression of Uncertainty in Measurement (GUM) 1st edn (Sèvres, Paris: BIPM Joint Committee for Guides in Metrology). Performance is measured in terms of the long-run success rate of an uncertainty calculation when applied to many simulated independent measurements. An individual calculation is deemed successful if the uncertainty interval obtained covers the measurand used in the simulation. Several examples, including two from the GUM, illustrate the approach. Software implementing the method is described in detail. Simulation is a practical method that can provide useful insights into specific measurement problems when there is any doubt about the validity of GUM calculations
[en] A new type of compact helium cryostat of great flexibility, with vapour cooled shields and a large neck (3.2 cm) is described. It has been successfully used for spectroscopic and astrophysical work in ground level or air-borne experiments. It can reach very low temperatures (1.2 K) and the very rigid internal structure eliminates alignment problems between cold and warm optics. (author)
[en] The industrial butterfly valves have been applied to transport a large of fluid with various fields of industry. Also, these are mainly used a control of fluid flux to the water and waste-water pipeline. Present, butterfly valves are manufacturing for multiplicity shape of bodies and discs with many producers. However, appropriate performance evaluation was not yet accomplished to compare about these valves through experiments. This study is performed the experiment of flow characteristics and performance of manufactured 400A butterfly valves for the water and waste pipeline, and compared experimental results. We performed experiments that were controlled fixed a differential pressure condition (1 psi) and the range of the flow rate conditions (500 m3/hr ∼ 2500 m3/hr), and also opened the disc of valves to a range of angle from 9 degree to 90 degree. We investigated and compared the valve flow coefficient and the valve loss coefficient of results through experiments with each butterfly valve.
[en] Most research in the structural engineering field uses either a simplified data-based model or a physics-based model to describe the dynamic behavior of servo-hydraulic actuators. In either way, the nominal model is typically used for modeling, analysis and control design. However, little effort has been directed to model uncertainties that are inherently associated with any physical system. A robust modeling approach is proposed in this study that can characterize both parametric and non-parametric uncertainties. The combination of this uncertainty with the nominal model provides a powerful tool to analyze the system performance and stability properties. Several control techniques are evaluated experimentally, and an H_∞ robust control design is demonstrated to achieve the best performance as well as good robustness. (paper)