This paper presents numerical and experimental investigation of the performance and internal flow field characteristics of
twin-entry radial inflow turbines at full and extreme partial admission conditions. The turbine is tested on a turbocharger
test facility, which was developed for small and medium size turbochargers. Experimental results show that the lowest efficiency
corresponds to extreme conditions. Therefore, flow field analyzing is employed to consider these conditions. The flow pattern
in the volute and impeller of a twin-entry turbine is analyzed using an in-house fully three-dimensional viscous flow solver.
The computational performance results are compared with the experimental results and good agreement is found. The flow field
at the outlet of the turbine is investigated using a five-hole pressure probe; the numerical results are also compared with
experimental measurements at the outlet of the rotor. For the volute, results show that lowest entropy gain factor corresponds
to the extreme conditions, particularly when shroud side entry is fully closed. At the inlet of the rotor for equal admission
conditions, the incidence angle is mostly in the optimum values. However, large variation in the incidence angle is seen in
the extreme conditions, which lead to larger incidence losses and consequently a lower efficiency. In addition, entropy distribution
contours corresponding to the exit plane are considered. For full admission, the location of low entropy gain factor at this
plane occupies a region near the shroud side of suction surface as well as near the hub side of the pressure surface that
corresponds to a region of high absolute flow angle. However, for the extreme cases, the low entropy gain factor occupies
a relatively larger region near the shroud side than full admission. So, higher loss generation is noted at the extreme cases.
Moreover, this entropy gain factor region is increased when shroud side entry is fully closed. 相似文献
The giant Kerr nonlinearity with reduced linear and nonlinear absorption in a four-level quantum dot by employing the tunnel coupling is investigated. It is shown that by enhancement of tunnel coupling value the Kerr nonlinearity increases and at the same time linear and nonlinear absorption reduces at the long wavelength which is very important for communicational applications. Enhanced of Kerr nonlinearity in a double quantum dots is investigated. It is found that the electron tunneling has an essential role to reducing the linear absorption and increasing the Kerr nonlinearity at long wavelength. 相似文献
Dozens of countries are executing national nanotechnology plans. No rigorous evaluation scheme for these plans exists, although
stakeholders—especially policy makers, top-level agencies and councils, as well as the society at large—are eager to learn
the outcome of these policies. In this article, we recommend an evaluation scheme for national nanotechnology policies that
would be used to review the whole or any component part of a national nanotechnology plan. In this scheme, a component at
any level of aggregation is evaluated. The component may be part of the plan’s overarching policy goal, which for most countries
is to create wealth and improve the quality of life of their nation with nanotechnology. Alternatively, the component may
be a programme or an activity related to a programme. The evaluation could be executed at different times in the policy’s
life cycle, i.e., before the policy is formulated, during its execution or after its completion. The three criteria for policy
evaluation are appropriateness, efficiency and effectiveness. The evaluator should select the appropriate qualitative or quantitative
methods to evaluate the various components of national nanotechnology plans. 相似文献
1. Introduction1.1 Silica nanoparticles and synthesis methods Silica (SiO2) nanoparticles are widely used in industry asan active filler for polymer reinforcement, a rheologicaladditive in fluids, a free flow agent in powders, and anagent for chemical mechanical polishing during IC (inte-grated circuit) fabrication (Sniegowski & de Boer, 2000).Silica powder is also used for producing silicon carbide(Koc & Cattamanchi, 1998) or opaque silica aerosols (Leeet al., 1995). Many methods can … 相似文献
A necessary condition for generation of bright soliton Kerr frequency combs in microresonators is to achieve anomalous group velocity dispersion (GVD) for the resonator modes. This condition is hard to implement in the visible as well as ultraviolet since the majority of optical materials are characterized with large normal GVD in these wavelength regions. We overcome this challenge by borrowing ideas from strongly dispersive coupled systems in solid state physics and optics. We show that photonic compound ring resonators can possess large anomalous GVD at any desirable wavelength, even if each individual resonator is characterized with normal GVD. Based on this concept, we design a mode‐locked frequency comb with thin‐film silicon nitride compound ring resonators in the vicinity of the rubidium D1 line (794.6 nm) and propose to use this optical comb as a flywheel for chip‐scale optical clocks.