Aerodynamic improvement of an aircraft gas-turbine engine fan

This work is concerned with the development of approaches to the aerodynamic improvement of axial-flow compressors for gas-turbine engines. The aim of this work is the aerodynamic improvement of an aircraft gas-turbine engine two-stage fan by numerical simulation of 3D turbulent gas flows. The approach used in this study features: varying the spatial shape of the fan blades for the first- and the second-stage impeller by varying the profile angle along the blade height; formulating quality criteria as the mean integral values of the power characteristics of each impeller of the fan over the operating range of the air flow rate through the impeller; and searching for advisable values of the impeller blade parameters by scanning the independent variable range at points that form a uniformly distributed sequence of small length. The basic tool is a numerical method developed at the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, which simulates 3D turbulent gas flows using the complete averaged Navier¬–Stokes equations and a two-parameter turbulence model. It is shown that varying the profile angle along the blade height for the fan second-stage impeller allows one to increase the air compression ratio in the fan by about 2 percent throughout the operating range of the fan air flow rate without affecting the adiabatic efficiency of the fan. On the whole, by the example of the fan under study, the paper considers the assumption that the aerodynamic improvement of compressors at the initial stage can be made on an impeller by impeller basis. It is shown that in further analysis providing the gas-dynamic stability of the compressor should be accounted for. The results obtained are intended to be used in the aerodynamic improvement of multistage compressors for aircraft gas-turbine engines and various power plant.

Research on aerodynamic characteristics through airflow clearances in compressor blades of gas turbine engine

Reducing the loss in the airflow clearance among the compressor blades of the rotor disk and stationary blades (guide vanes) is an urgent issue. Furthermore, additional losses of airflow through the clearances among the blades and airfoil losses are the main cause of reducing the efficiency of an axial flow compressor, especially the blade height is small. With a view towards the efficiency improvement of a multistage axial compressor with a high-pressure ratio, it is necessary to manufacture a highly economical compressor with a variety of compression stages. Airflow in the circulation clearances alternating among compressor blades has viscosity, unstable compression, and quite complex flow structure. This needs to be researched into the design with the assistance of modern software (ANSYS CFX, FlowER, etc.). Although this is an important step in the current design orientation, it requires additional practical elements to perform, especially the problem of optimizing the outer rim, the level, and the number of compression stages in the whole compressor. In this paper, authors have used the method of creating three-dimensional (3D) models for blade profiles in a compressor based on analyzing the flow in three-dimensional form and studying their parameters. This paper deals with the geometry problems of the row of rotating blades (cascade) by proposing the structural arrangement of stacking blades in the circular direction and the blade profile formed the S-shape. Investigating and calculating the aerodynamic properties of the airflow through clearances of compressor blades by using ANSYS is one of the new methods. The researched result showed the dependence between the camber angle as the rotating blade formed an S-shape profile rotates regarding the stagger angle of the airfoil and the incident angle of airflow. Some characteristics of aerodynamic properties are distributed according to the blade height in conducting with different curved profiles of the rotating blades on the rotor disk and stationary blades.

Time-Resolved Measurements of the Unsteady Boundary Layer in an Annular Low-Pressure Turbine Configuration With Perturbed Inlet

In this study the unsteady behavior of the boundary layers developing on a LPT stator profile and their effect on secondary flow patterns in a 1.5-stage turbine configuration are investigated under the influence of periodic inflow perturbations. The experimental setup previously employed to analyze the unsteady secondary flow in the stator wake has been enhanced by hotfilm sensor arrays placed on the stator profiles at different blade height positions to provide time-resolved data from within the passage. The turbine inflow is perturbed by periodically passing circular bars and a modified T106-profile has been considered for the blading. The modified profile, labeled as T106RUB, was developed for matching the transition and separation characteristics of the original T106 profile at low flow speeds, thus facilitating measurements to be taken in a large-scale test rig with its improved accessibility. The transition phenomena occurring in the profile boundary layers are investigated under both unperturbed and periodically perturbed inflow by means of spectral analysis, the semi-quantitative characterization of the wall-stress system and an evaluation of the statistic quantities. In particular, the periodic changes of the suction side boundary layer flow region towards the trailing edge are studied in detail. Furthermore, time-resolved hot-film measurements at different blade height positions facilitate a detailed comparison of the quasi two-dimensional mid-span profile flow and the near end wall profile flow which is subject to influence of secondary flow structures. These information are employed to assess to which extent the additional turbulence originating from the wakes affects the blade boundary layers and thus the secondary flow structures. Furthermore, the role of the perturbation frequency on the coupled system of boundary layers and secondary flow structures is evaluated.

Theoretical and Experimental Study and Design Method of Blade Height of a Rotational-Flow Suction Unit in a Wall-Climbing Robot

A wall-climbing robot that uses a rotational-flow suction unit to be non-contact-absorbed onto walls can climb rough walls and overstep obstacles. In the rotational-flow suction unit, the air driven by the blades rotates at a high speed within a chamber, thereby creating and maintaining a negative pressure distribution. This study is focused on the modeling and design of the blade height. First, a theoretical model of the rotation flow, containing two important parameters (i.e., blade height Hb and clearance h), was established and verified experimentally. Furthermore, the computational fluid dynamics (CFD) method was applied to illustrate the secondary flow relative to the blades, revealing that it gives rise to a nonlinear velocity distribution. It was found that an increase in the blade height greatly improves the F–h characteristics; in addition, the relationship between the power consumption and suction force (E˙−F curve) is mainly determined by the clearance h instead of the blade height Hb. Based on these findings, we propose a design method for determining the suitable blade height. According to the characteristic load curves of the suction units (i.e., the T–ω curves) and the motor characteristics, suitable blades can be selected to match the motor operation (i.e., nominal operating state).

Investigation on the aerodynamic performance of high camber turning angle cascade with tubercle leading edge

In order to improve the performance of high-loaded compressor stator with large camber turning angle, a stator cascade blade with tubercle leading edge was designed based on the wavy leading edge of humpback’s flipper, and computational fluid dynamics simulation was carried out. The results show that the tubercle leading edge can effectively improve the aerodynamic performance of the stator cascade at high attack angles, and the total pressure loss coefficient can be reduced by 26.46%. The main reason why the tubercle structure improves the performance is that it makes the radial displacement of airflow appear as a butterfly-like structure at the leading edge of the blade, which restrains the occurrence and development of airflow separation. By comparing the performance of the blades with full-span and part-span tubercle leading edges, it is considered that the tubercle leading edge of 80% blade height in the mainstream region can improve the aerodynamic performance of cascade better, while the one of 50% blade height has the worst effect.

Optimization of Straight-bladed Darrieus type vertical axis wind blade for low wind speed

Straight-bladed Darrieus blade is a type of vertical axis wind turbine that requires low wind speed to operate but is considered less efficient due to conventional blade geometry. To increase its performance by means of dynamic torque, the study used a statistical method, central composite design, through DesignExpert software. The computational fluid dynamics (CFD) through SolidWorks Reynolds-Averaged Navier Stokes Equation (RANS) k – epsilon turbulence model was used to simulate the Design of Experiments. The study was composed of two phases, namely 2D and 3D simulations. The 2D simulation studied the effect of varying the camber, camber location, and thickness to the dynamic torque, while the 3D simulation varied the blade height, rotor radius, and materials. The camber’s optimal conditions, camber location, and thickness in 2D simulations are 4.75%, 45%, and 15.50% of the chord, respectively. These optimal design values could reach the dynamic torque equivalent to 60.6571 Newton-meter. Meanwhile, the blade height and rotor radius of the 3D simulations have optimal design values of 4.41 meters and 4.75 meters, respectively. These optimal values could increase the dynamic torque to 2310.01 Newton-meter. The dynamic torque of the optimal design obtained a 133% significant increase compared to the conventional blade. Thus, the research has proven the increase in the Darrieus Wind turbine’s performance by varying its blade geometry.

Effect of impeller blade curvature on the hydrodynamics and power consumption in a stirred tank

The performance of curved bladed turbines (CBTs) for the agitation of Newtonian fluids in cylindrical tanks is investigated. The efficiency of CBT is compared with that of the standard Rushton turbine. Also, effects of the blade height of the new designed impeller are highlighted. The computational fluid dynamics (CFD) study is performed to observe the axial, radial and tangential components of velocities, flow patterns and power consumption. The obtained results revealed that the increase of blade curvature reduces the power consumption. Also, a slight decrease of power number is observed in the turbulent flow regime within unbaffled tanks. In a comparison between the cases studied, the best axial circulation of fluid is given by the impeller with flat blades. The increase of the height of curved blades has generated a stronger tangential flow and enhanced the axial movement of fluid particles, but with further penalty in power input.

Effect of Savonius blade height on the performance of a hybrid Darrieus-Savonius wind turbine

A vertical hybrid turbine commonly consists of a Darrieus and Savonius rotor where the Savonius is inside Darrieus turbine. This paper describes the experimental study of hybrid Darrieus-Savonius wind turbines by variation in Savonius blade height. In this case, the effect of the blade height of the Savonius blade was studied experimentally in a subsonic wind tunnel. The effect of the height of a Savonius blade relative to that of Darrieus called blade height ratios δ was investigated to know the hybrid turbine performance. The performance is represented by power and torque coefficient. The result shows that the hybrid turbine with height ratio greater than unity δ = 1.4 gives the highest power CP = 0.20 and torque coefficient CT = 0.129. It is investigated that the torque and the power coefficient have a higher value than that of Darrieus turbine, in which the increase in power and torque coefficient are 48% and 29%, respectively. This hybrid wind turbine with a blade height ratio greater than unity can be considered as an important variable in the wind turbine construction.

Correlation of Power Consumption of Double Impeller Based on Impeller Spacing in Laminar Region

Power consumption is an important parameter for the design of mixing equipment. The aim of this study is to develop a new correlation of the power consumption of a double impeller. The effect of impeller spacing on the double-impeller flow pattern and power consumption was investigated in the laminar region. As a result, the effect of impeller spacing on the flow pattern was described based on the ratio of impeller spacing to the impeller blade height. Moreover, the power consumption of a double impeller could be correlated with the same ratio.