The effect of single-sided ribs on heat transfer and pressure drop within a trailing edge internal channel of a gas turbine blade

Convective cooling in a gas turbine blade internal trailing edge channel is often insufficient at the sharp trailing edge. This study examines convective heat transfer and pressure drop within a simplified trailing edge channel. The internal passage has been modeled as a right triangular channel with a 9° angle sharp corner. Smooth baseline and ribbed copper plates were heated from underneath via a uniform heat flux heater and examined via infrared thermography. Non-uniformity in the heat flux due to conduction is corrected by a RANS conjugate heat transfer calculation, which was validated by the mean velocity, friction factor, and temperature fields from experiments and LES simulations. Nusselt number distributions illustrate that surface heat transfer is increased considerably with ribs, and coupled with the vortices in the flow. Heat transfer at the sharp corner is increased by more than twofold due to ribs placed at the center of the channel, due to secondary flow. The present partially ribbed channel utilizes secondary flow toward the corner, and is presumed to have better thermal performance than a fully ribbed channel. Thus, it is important to set the appropriate rib length within the channel.

Valley Vortex Assisted and Topological Protected Microparticles Manipulation with Complicated 2D Patterns in a Star-Like Sonic Crystal

Arranging microparticles into desired patterns, especially in a complicated pattern with a reliable and tunable manner, is challenging but highly desirable in the fields such as biomedicine and tissue engineering. To overcome these limitations, here, by using the concept of topology in acoustics, the valley vortex is utilized to manipulate particles on a large scale with complicated 2D patterns in the star-like sonic crystals at different frequencies. A topologically protected edge state is obtained at the interface of the crystals with different valley Hall phases, which shows the ability of reliable microparticles control along the sharp corner and the capability of robust particles cluster aggregation in a defective system. The results may provide intriguing resources for future microfluidic systems in a complicated and brittle environment.

None sharp corner localized surface plasmons resonance based ultrathin metasurface single layer quarter wave plate

We report on a non-sharp-corner quarter wave plate (NCQW) within the single layer of only 8 nm thickness structured by the Ag hollow elliptical ring array, where the strong localized surface plasmons (LSP) resonances are excited. By manipulating the parameters of the hollow elliptical ring, the transmitted amplitude and phase of the two orthogonal components are well controlled. The phase difference of π/2 and amplitude ratio of 1 is realized simultaneously at the wavelength of 834 nm with the transmission of 0.46. The proposed NCQW also works well in an ultrawide wavelength band of 110 nm, which suggests an efficient way of exciting LSP resonances and designing wave plates, and provides a great potential for advanced nanophotonic devices and integrated photonic systems.

Structural Design and Tensile Experiment of Connection Node between acrylic and Stainless Steel

Acrylic are widely used as load-bearing structural parts. In this study, the structural design, finite element analysis (FEA) and tensile experiment of the connection node of the acrylic spherical vessel designed for Jiangmen Underground Neutrino Observation (JUNO) are carried out. The acrylic connection node needs to withstand a tensile load of 90 kN for 20 years, and its ultimate bearing capacity is required to be 6 times the working load. Under working load, the stress of the acrylic structure should be less than 3.5 MPa. In the study, a connection node connecting acrylic and stainless steel is designed. By embedding the steel ring in the acrylic structure to connect with the support rod, the acrylic connection node can withstand high loads. A 1/4 symmetric model of connection node is established, and the FEA method is used to solve nonlinear problems such as material nonlinearity and frictional contact. The results of FEA show that the maximum principle stress of the connection node is about 2.92 MPa. By comparing the stress of the FEA results with the experimental results, the relative difference is 7.24 %, indicating that the FEA results are credible. The experiment results also show that the ultimate tensile load of the connection node can reach 1000 kN, which is about 11 times the working load. The breakdown of the connection node occurs at the sharp corner of the groove instead of the maximum stress point. Through the design, simulation and experiment of the connection node, for the brittle materials such as acrylic, the structure should avoid the defects such as sharp corner.

Experimental Evaluation on Corner Accuracy in WEDM for Aluminium 6061 Alloy

An important electro-thermal process known as wire electrical discharge machining (WEDM) is applied for machining of conductive materials to generate most precisely. All cutting inaccuracies of WEDM arise out of the major cause of wire bending. At the time of cutting a sharp corner or cut profile, bending of the wire leads to a geometrical error on the workpiece. Though this type of error may be of a few hundred microns, it is not suitable for micro applications. In this research study, an experimental investigation based on response surface methodology (RSM) has been done on wire EDM of Aluminium 6061 t6 alloy. This chapter studies the outcome of input process variables (i.e., wire feed rate, pulse on time, pulse off time, and gap voltage) on machining output responses (i.e., corner inaccuracy) extensively. Experimental validation of the proposed model shows that corner inaccuracy value may be reduced by modification of input parameters.

Determination of stress intensity factors for elements with sharp corner located on the interface of a bi-material structure or homogeneous material

This paper presents a new universal analytical and numerical method allowing for determination of stress intensity factors (SIFs) for notches and cracks located in both a homogeneous and a heterogeneous material. An advantage of the proposed method is that it does not require knowledge of an analytical description of singular stress/displacement fields or connection of SIFs to energy parameters such as energy release factor. In this method, a universal analytical function has been used, which in combination with data obtained using finite element method (FEM) allows for a direct determination of stress intensity factors. One parameter that is necessary to know when using the proposed method is the eigenvalue $$\lambda $$ λ . The characteristic equation allowing for determination of the eigenvalues for any corner has been given herein. What is more, also a criterion clearly defining the nodes is determined, from which FEM numerical results are implemented to the developed analytical function. In order to verify the proposed method, for a selected group of geometrical and material structures with sharp corner, values of stress intensity factors were determined and compared to data available in the literature. Satisfactory compliance of obtained results with literature ones was found.