Effect Of Variable Geometry Research Articles

Design Optimization and Variable Geometries Implementation of a High Bypass Three-Shaft Turbofan Engine for EIS2050

Abstract This paper aims to develop an advanced three-shaft turbofan engine with ultrahigh bypass ratio (BPR) for entry-into-service (EIS)2050. The boundary approaching method is utilized to obtain the optimal engine for a series of engines with different fan diameters. Furthermore, the flight mission analysis was carried out to fully consider the engine performance and weight penalty. The optimum engine employs a 3.26 m fan diameter with ultrahigh BPR reaching 21.39. The corresponding specific fuel consumption (SFC) is 11.42 (g/s)/kN, which is 3.88% lower than the 2.95 m fan diameter engine. However, the weight penalty has offset part of the benefits, and the block fuel reduction is 2.5%. Sensitivity analysis results reveal that the low-pressure turbine (LPT) efficiency plays a dominant role in engine performance. Afterwards, the effects of variable geometry are investigated including the blow-off valve (BOV), variable inlet guide vane (VIGV), and bypass variable area nozzle (VAN). Results show that combining the three measures would boost engine performance and save fuel. The designed schedule for the combination of VIGV, BOV, and VAN has generated a reduction in block fuel, NOx, CO2, and H2O reaching 3.36%, 5.55%, 2.47%, and 2.53%, respectively.

Effect of Tip Configurations on Aerodynamic Performance of Variable Geometry Linear Turbine Cascade

Abstract The variable geometry turbine (VGT) has been widely used in different fields due to its higher efficiency and lower fuel consumption at part-load. However, the flow field in a VGT is characterized by the leakage flow through the radial clearance of rotational vane compared with a general fixed vane turbine. Numerical simulations are conducted on a linear turbine cascade to reduce the leakage flow based on passive control method. The aerodynamic performances and flow fields are compared for four kinds of tip configuration firstly. Then, the effect of variable geometry on the linear turbine cascade aerodynamic performance is investigated for five installation angles ranging from –5 to 5 deg. In addition, the development patterns and trends of the tip leakage vortex and the passage vortex are analyzed. The results show that the squealer tip and the rotating axis have a significant impact on suppressing leakage flow. The leakage flow rate has a tendency to decrease, and the total pressure coefficient is gradually increased when installation angle ranges from –5 to 5 deg. The interactions between tip leakage vortex and passage vortex leads to the different trends on leakage flow at various installation angles and axial sections.

Effect of Variable Geometry on Springback of High Strength Steel Materials

Springback is the phenomenon in which the material strip unbends itself after forming process. It is caused by the geometrical, mechanical properties or other process parameters. This paper focused on finite element simulation investigation on effects of geometrical parameters on the springback amount of the High Strength Steel (HSS). Two geometrical parameters, punch radius (Rp) and die opening (Wo) were selected and their effect on springback studied. Finite element simulation of U-bending test was performed using Simufact.formingTM with material database (MatILDa) and the level of the springback was measured. The result of the simulation shows that different values of punch radius (Rp) and die opening (Wo) are significant to the springback effect. 3 variable values of (Rp) and (Wo) selected in this studied are (2mm, 4mm, 6mm) and (30mm, 36mm, 48mm) respectively. The findings of the simulation could be used to accurately and reliably predict springback behavior of the tested material. The value of the springback increases, as the value of the die opening (Wo) increases. Meanwhile, the increasing value of the punch radius (Rp) will lead to decreasing springback value. From this finding, a proper prevention method can be taken to eliminate springback, achieve improvement in the forming process as well as reduce processing time and cost.

Dynamic analysis of variable-geometry electrostatic microactuators

This paper investigates the dynamic behavior of a microbeam-based electrostatic microactuator. The cross-section of the microbeam under consideration varies along its length. A mathematical model, accounting for the system nonlinearities due to mid-plane stretching and electrostatic forcing, is adopted and used to examine the microbeam dynamics. The differential quadrature method (DQM) and finite difference method (FDM) are used to discretize the partial–differential–integral equation and generate frequency-response curves for various microstructure geometries and different voltages. We show that the use of the DQM, with a few grid points, in conjunction with the FDM applied to the space derivatives and time derivatives, respectively, yields excellent convergence of the dynamic solutions. The stability of these solutions is examined using Floquet theory. Results are presented to display the dynamics and the effect of variable geometry on the frequency-response curves of the microstructure. We first demonstrate convergence of the DQM–FDM discretized dynamics model as the number of grid points is varied from 5 to 13, while the number of time steps in one time period is fixed at 100. The proposed DQM–FDM discretized dynamic model is then compared to recently reported models. We show that the shape of the frequency-response curves of the microbeam, excited near its first natural frequency, is very sensitive to the approximations employed in the construction of the model. Finally, we examine the effect of varying the gap size and the microbeam thickness and width on its frequency-response curves for hardening-type and softening-type behaviors.