Unsteady Film Cooling Performance on the High Pressure Turbine Shroud Under Rotor-Stator Interaction for an Aero-Engine

The turbine rotor inlet temperature of modern aero-engines has continuously increased in order to achieve higher thrust-to-weight ratio and thermal efficiency, which requires higher cooling effectiveness for turbine components. The turbine shroud is exposed to the blade tip leakage flow, and has become a common limiting factor for the turbine stage of advanced aero-engines. The three-dimensional numerical simulation on the unsteady film cooling characteristics of the high-pressure turbine shroud for an aero-engine under the rotor-stator interaction and the high blade rotation speed was conducted. The sliding grid technology was used to realize the relative movement between the turbine blade and the turbine shroud, and the rotor-stator interaction. Effects of the blade rotation, blowing ratios and the film jet direction on the unsteady film cooling performance of the high-pressure turbine shroud were revealed. It is found that the film cooling characteristics of the turbine shroud present an unsteady and periodic phenomenon. The blade tip clearance leakage flow, leakage vortex and mainstream suppression have important effects on the film cooling performance of the high-pressure turbine shroud. More attention should be paid to the insufficient cooling margin of the front row film holes due to coolant jet liftoff from the shroud surface under the high blowing ratio.

A simplified model for transition prediction applicable to wind-turbine rotors

This work aims to develop a simple framework for transition prediction over wind-turbine blades, including effects of the blade rotation and spanwise velocity without requiring fully three-dimensional simulations. The framework is based on a set of boundary-layer equations (BLEs) and parabolized stability equations (PSEs), including rotation effects. An important element of the developed BL method is the modeling of the spanwise velocity at the boundary-layer edge. The two analyzed wind-turbine geometries correspond to a constant airfoil and the DTU 10-MW Reference Wind Turbine blades. The BL model allows an accurate prediction of the chordwise velocity profiles. Further, for regions not too close to the stagnation point and root of the blade, profiles of the spanwise velocity agree with those from Reynolds-averaged Navier–Stokes (RANS) simulations. The model also allows predicting inflectional velocity profiles for lower radial positions, which may allow crossflow transition. Transition prediction is performed at several radial positions through an “envelope-of-envelopes” methodology. The results are compared with the eN method of Drela and Giles, implemented in the EllipSys3D RANS code. The RANS transition locations closely agree with those from the PSE analysis of a 2D mean flow without rotation. These results also agree with those from the developed model for cases with low 3D and rotation effects, such as at higher radial positions and geometries with strong adverse pressure gradients where 2D Tollmien–Schlichting (TS) waves are dominant. However, the RANS and PSE 2D models predict a later transition in the regions where 3D and rotation effects are non-negligible. The developed method, which accounts for these effects, predicted earlier transition onsets in this region (e.g., 19 % earlier than RANS at 26 % of the radius for the constant-airfoil geometry) and shows that transition may occur via highly oblique modes. These modes differ from 2D TS waves and appear in locations with inflectional spanwise velocity. However, except close to the root of the blade, crossflow transition is unlikely since the crossflow velocity is too low. At higher radial positions, where 3D and rotation effects are weaker and the adverse pressure gradient is more significant, modes with small wave angles (close to 2D) are found to be dominant. Finally, it is observed that an increase in the rotation speed modifies the spanwise velocity and increases the Coriolis and centrifugal forces, shifting the transition location closer to the leading edge. This work highlights the importance of considering the blade rotation and the three-dimensional flow generated by that in transition prediction, especially in the inner part of the blade.

Application of the Craig-Bampton method to blade rotation

The Craig-Bampton method has repeatedly shown its effectiveness in modelling the deformable solid body motion and in practical experience of implementing this approach in engineering software. It reduces the motion equations system which is obtained by approximating small elastic displacements of the body finite element model with a set of acceptable modes. The application of this method in engineering improves the computing time performance and requires less computational resources. In this article the effectiveness of using the Craig-Bampton method for the blade rotation is evaluated. The need to consider the inertial relationship between large body displacements and elastic deformations was investigated. As a result of the numerical solution, it was obtained that the method works correctly for the investigated task. It allows us to conclude that the Craig-Bampton method is applicable for the blade rotation process.

An Experimental Investigation of Wake Characteristics and Power Generation Efficiency of a Small Wind Turbine under Different Tip Speed Ratios

We carried out a wind tunnel experiment to examine the power generation efficiency of a stand-alone miniature wind turbine and its wake characteristics at different tip speed ratios (TSRs) under the same mean inflow velocity. Resistors in the electrical circuit were adjusted to control the TSRs to 0.9, 1.5, 3.0, 4.1, 5.2, and 5.9. The currents were measured to estimate the turbine power outputs versus the TSRs and then establish the actual power generation coefficient Cp distribution. To calculate the mechanical power coefficient, a new estimation method of the mechanical torque constant is proposed. A reverse calibration on the blade rotation speed was performed with given electrical voltages and currents that are used to estimate the mechanical power coefficient Cp, mech. In the experiment, the maximum Cp,mech was approximately 0.358 (corresponding to the maximum Cp of 0.212) at the TSR of 4.1. Significant findings indicate that the turbine at the TSR of 5.2 produces a smaller torque but a larger power output compared with that at the TSR of 3.0. This comparison further displays that the turbine at the TSR of 5.2, even with larger power output, still produces a turbine wake that has smaller velocity deficits and smaller turbulence intensity than that at the TSR of 3.0. This behavior demonstrates the significance of the blade-rotation control (i.e., pitch regulation) system to the turbine operation in a large wind farm for raising the overall farm power productivity.

Simulation Study on Positive Corona Discharge of Receptors on Rotating Wind Turbine Blade Tips under Thundercloud Electric Fields

Recent lightning simulation experiments have not simulated the influence of blade rotation in the long term after corona inception. This study uses a finite element method and considers the adhesion and collision processes of positive ions, aerosol ions, and neutral particles to establish a two-dimensional positive corona discharge model based on a multicomponent diffusion transport equation. The microscopic distribution of these three types of particles and the influence mechanism of charged particles’ migration under electric fields and wind were studied. The results show that ion migration is affected by both electric field and wind speed. The higher the wind speed, the larger is the deviation amplitude of charged particles along the direction of wind. With an increase in wind speed, the corona current on the receptor surface gradually increases. When the wind speed is 30 m/s, the corona current peak value increases by almost six times when compared with that when no wind is present. From this, it can be inferred that blade rotation reduces the concentration of positive ion in the receptor area, thereby facilitating electron avalanche and streamer-leader conversion.

MODIFIKASI DESAIN TRAKTOR TANGAN “TEMBESI” (STUDI KASUS DI PERKEBUNAN “TEMBESI”)

"Tembesi" hand tractor is a tool in the field of agriculture that is used to loosen the soil that is driven by gasoline fuel motor with a driving motor power of 6.5 Hp. From the results of the previous design testing (Rev_00) found a problem, where the tractor is difficult to move and when the rotating blade is then given a load the blade stops rotating. This study aims to improve the design of the "Tembesi" hand tractor which is focused on reducing the number of blade turns to increase the moment value and repair the part of the tractor wheel.From the design modification results, the blade rotation speed is modified from 1333 rpm to 450 rpm. From the plan moment value 6,925 kg.mm, the force produced by the "Tembesi" hand tractor blade is 387,79 Newton. Wheel modification is carried out using a 12-inch diameter (304.8 mm) rubber tire wheel.

Systematic Experimental Evaluations Aimed at Optimizing the Geometry of Axial Casing Groove in a Compressor

Performance and flow measurements are carried out to investigate the impact of varying the geometry of axial casing grooves on the stall margin and efficiency of an axial turbomachine. Prior studies have shown that skewed semi-circular grooves installed near the blade leading edge (LE) have multiple effects on the flow structure, including ingestion of the tip leakage vortex (TLV), suppression of backflow vortices, and periodic variations of flow angle. To determine which of these phenomena is a key contributor, the present study examines the impact of several grooves, all with the same inlet geometry, but with outlets aimed at different directions. The “U” grooves that have circumferential exits aimed against the direction of blade rotation achieve the highest stall margin improvement of well above 60% but cause a 2.0% efficiency loss near the best efficiency point (BEP). The “S” grooves, which have exits aimed with the blade rotation, achieve a relatively moderate stall margin improvement of 36%, but they do not reduce the BEP efficiency. Other grooves, which are aligned with and against the flow direction at the exit from upstream inlet guide vanes, achieve lower improvements. These trends suggest that causing high periodic variations in flow angle around the blade leading edge is particularly effective in extending the stall margin, but also reduces the peak efficiency. In contrast, maintaining low flow angles near the LE achieves more moderate improvement in stall margin, without the maximum efficiency loss. Hence, of the geometries tested, the S grooves appear to have the best overall impact on the machine performance. Velocity measurements and flow visualizations are performed in an axial plane located downstream of the grooves, near the trailing edge of the rotor. Reduced efficiency or performance co-occurs with elevated circumferential velocity in the tip region, but differences in the axial blockage are subtle. Yet, near the BEP, the regions with reduced axial velocity, or even negative velocity between the TLV and the endwall, are wider behind the U grooves compared to the S grooves. The vorticity profiles also show that at low flow rates the TLV is ingested entirely by the grooves, in contrast to the best efficiency point, where a considerable fraction of the TLV rollup occurs downstream of the grooves.

RANCANG BANGUN MESIN PERAJANG PELEPAH SAWIT UNTUK PAKAN TERNAK

The design of the palm frond chopper machine for animal feed is a vocational application. The purpose of making palm frond chopper machines for animal feed is to help the community open a business field, especially the development of livestock production who grow oil palm. It is an expected that the palm frond chopper machine can help the community to improve economic output. This machine has dimensions of 600 mm x 500 mm where the working principle of the machine is to cut using a blade to accelerate the cutting process. Blade rotation is a obtained by using 3 HP motor and using pulley 5 inch as a tool to rotate the knife plate.