scholarly journals Power Fan Design of Blended-Wing-Body Aircraft with Distributed Propulsion System

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Yuan Jia ◽  
Jinye Li ◽  
Jianghao Wu
Keyword(s):  
Boundary Layer ◽  
Internal Flow ◽  
Calculation Model ◽  
External Flow ◽  
Low Noise ◽  
Strongly Coupled ◽  
Distributed Propulsion ◽  
Blended Wing Body ◽  
Passenger Aircraft ◽  
Drag Ratio

A blended-wing-body aircraft has the advantages of high lift-to-drag ratio, low noise, and high economy compared with traditional aircraft. It is currently a solution with great potential to become a future civilian passenger aircraft. However, most airplanes with this layout use distributed power, and the power system is on the back of the fuselage, with embedded or back-supported engines. This type of design causes the boundary layer suction effect. The boundary layer ingestion (BLI) effect can fill the wake of the aircraft and improve the propulsion efficiency of the engine. However, it causes huge design difficulties, especially when the aircraft and the engine are strongly coupled. In this paper, an aircraft with a coupled engine configuration is studied. The internal and external flow fields are calculated through numerical simulation. A realistic calculation model is obtained through the coupling of boundary conditions. On the basis of the influence of the external flow on the internal flow under the coupled condition, the influence of the BLI effect on the aerodynamic performance of the fan is investigated.

Dynamics of Slender Tapered Beams With Internal or External Axial Flow—Part 1: Theory

1979 ◽  
Vol 46 (1) ◽  
pp. 45-51 ◽  
Author(s):  
M. J. Hannoyer ◽  
M. P. Paidoussis
Keyword(s):  
Boundary Layer ◽  
Boundary Layer Thickness ◽  
Equations Of Motion ◽  
Axial Flow ◽  
Internal Flow ◽  
External Flow ◽  
High Flow ◽  
Flow Passage ◽  
Flow Part ◽  
Surrounding Fluid

This paper develops a general theory for the dynamics of slender, nonuniform axisymmetric beams subjected to either internal or external flow, or to both simultaneously. The effect of the boundary layer of the external flow is taken into account in the formulation. Typical solutions of the equations of motion are presented for cantilevered conical beams in external flow and for beams with a conical internal flow passage. Such systems lose stability at sufficiently high flow velocity, internal or external, either by flutter or by buckling. The effect of several parameters is investigated. For internal flow, the internal and external shape, whether uniform or conical, and the density of the surrounding fluid have sometimes unexpected effects on stability; e.g., tubular beams lose stability at lower internal flow when immersed in water than when in air. For external flow the effects of conicity, free end shape and boundary-layer thickness are investigated; the latter has a strong stabilizing influence, such that simple theory neglecting this effect results in serious error.

A key design parameter proposal for aerodynamically efficient subsonic blended wing body

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Seyhun Durmus
Keyword(s):  
Aspect Ratio ◽  
Design Parameter ◽  
Low Noise ◽  
Design Stage ◽  
Efficiency Coefficient ◽  
Content Type ◽  
Blended Wing Body ◽  
Wetted Area ◽  
Drag Ratio ◽  
Weight Data

Purpose Blended wing body (BWB) is a very advantageous design in terms of low fuel consumption, low emission and low noise levels. Because of these advantages, the BWB is a candidate to become the commercial passenger aircraft of the future by providing a paradigm shift in conventional designs. This paper aims to propose a key design parameter for wing sizing of subsonic BWB and a performance parameter for calculating the lift/drag ratio values of BWBs. Design/methodology/approach The parameter proposed in the study is based on the square/cube law, that is, the idea that the wetted area is proportional to the power of 2/3 of the weight. Data on the weight, wing area, wingspan, lift-to-drag (L/D) ratio for 19 BWB used in the analyzes were compiled from the published literature and a theoretical methodology was developed to estimate the maximum lift to drag ratio of BWBs. The accuracy of the proposed key design parameter was questioned by comparing the estimated L/Dmax values with the actual values. Findings In the current study, it is claimed that the wingspan/(take-off gross weight)(1/3) parameter provides an L/D efficiency coefficient regardless of aircraft size. The proposed key design parameter is useful both for small-scale BWB, that is unmanned aerial vehicles BWB and for large-scale BWB designs. Therefore, the b/Wg(1/3) parameter offers a dimensionless L/D efficiency coefficient for BWB designs of different scales. The wetted aspect ratio explains how low aspect ratio (AR)-BWB designs can compete with high AR-tube-and-wing designs. The key parameter is also useful for getting an idea of good or bad BWB with design and performance data published in the literature. As a result, reducing the blending area and designing a smaller central body are typical features of aerodynamically efficient BWB. Originality/value As the role of the square/cube law in the conceptual aircraft design stage has not been sufficiently studied in the literature, the application of this law to BWBs, a new generation of designs, makes the study original. Estimation of the wetted area ratio using only wingspan and gross weight data is an alternative and practical method for assessing the aerodynamic performance of the BWB. According to the model proposed in the current study, reducing the take-off gross weight of the BWBs using lighter building materials and designing with a larger wingspan (b) are the main recommendations for an aerodynamically efficient BWB.

scholarly journals Aspect Ratio Driven Relationship between Nozzle Internal Flow and Supersonic Jet Mixing

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 78
Author(s):  
Kalyani Bhide ◽  
Kiran Siddappaji ◽  
Shaaban Abdallah
Keyword(s):  
Boundary Layer ◽  
Aspect Ratio ◽  
Nozzle Exit ◽  
Supersonic Jet ◽  
Internal Flow ◽  
Shear Stresses ◽  
Loss Mechanism ◽  
Potential Core ◽  
Jet Mixing ◽  
Aspect Ratios

This work attempts to connect internal flow to the exit flow and supersonic jet mixing in rectangular nozzles with low to high aspect ratios (AR). A series of low and high aspect ratio rectangular nozzles (design Mach number = 1.5) with sharp throats are numerically investigated using steady state Reynolds-averaged Navier−Stokes (RANS) computational fluid dynamics (CFD) with k-omega shear stress transport (SST) turbulence model. The numerical shadowgraph reveals stronger shocks at low ARs which become weaker with increasing AR due to less flow turning at the throat. Stronger shocks cause more aggressive gradients in the boundary layer resulting in higher wall shear stresses at the throat for low ARs. The boundary layer becomes thick at low ARs creating more aerodynamic blockage. The boundary layer exiting the nozzle transforms into a shear layer and grows thicker in the high AR nozzle with a smaller potential core length. The variation in the boundary layer growth on the minor and major axis is explained and its growth downstream the throat has a significant role in nozzle exit flow characteristics. The loss mechanism throughout the flow is shown as the entropy generated due to viscous dissipation and accounts for supersonic jet mixing. Axis switching phenomenon is also addressed by analyzing the streamwise vorticity fields at various locations downstream from the nozzle exit.

scholarly journals Numerical Simulation and Experimental Study on Flow Field in a Swirl Nozzle

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Yicheng Sun ◽  
Yufan Fu ◽  
Baohui Chen ◽  
Jiaxing Lu ◽  
Wanquan Deng
Keyword(s):  
Flow Field ◽  
Velocity Distribution ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Low Pressure ◽  
External Flow ◽  
Droplet Velocity ◽  
Inlet Pressure ◽  
Outlet Section ◽  
Local Pressure

In order to study the internal flow characteristics and external droplet velocity distribution characteristics of the swirl nozzle, the following methods were used: numerical simulations were used to study the internal flow characteristics of a swirl nozzle and phase Doppler particle velocimetry was used to determine the corresponding external droplet velocity distribution under medium and low pressure conditions. The distributions of pressure and water velocity inside the nozzle were obtained. Meanwhile, the velocities of droplets outside the nozzle in different sections were discussed. The results show that the flow rate in the swirl nozzle increases with the increase in inlet pressure, and the local pressure in the region decreases because of the excessive velocity at the internal outlet section of the swirl nozzle, resulting in cavitation. The experimental results show that under an external flow field, the minimum droplet velocity occurs in the axial direction; starting from the axis, the velocity first increases and then decreases along the radial direction. Swirling motion inside the nozzle and velocity variations in the external flow field occur under medium and low pressure conditions. The relationship between the inlet pressure and the distributions of water droplets’ velocities was established, which provides a reference for the research and development of the swirl nozzle.

Secondary Flow Loss Reduction Method by Use of Endwall Contouring in Gas Turbine Cascade Using Optimization Method

2021 ◽  
Author(s):  
Kazuki Yamamoto ◽  
Ryota Uehara ◽  
Shohei Mizuguchi ◽  
Masahiro Miyabe
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Cross Flow ◽  
Internal Flow ◽  
Optimization Method ◽  
Loss Reduction ◽  
Turbine Cascade ◽  
Flow Loss ◽  
Endwall Contouring

Abstract High efficiency is strongly demanded for gas turbines to reduce CO2 emissions. In order to improve the efficiency of gas turbines, the turbine inlet temperature is being raised higher. In that case, the turbine blade loading is higher and secondary flow loss becomes a major source of aerodynamic losses due to the interaction between the horseshoe vortex and the strong endwall cross flow. One of the authors have optimized a boundary layer fence which is a partial vane to prevent cross-flow from pressure-side to suction-side between blade to blade. However, it was also found that installing the fence leads to increase another loss due to tip vortex, wake and viscosity. Therefore, in this paper, we focused on the endwall contouring and the positive effect findings from the boundary layer fence were used to study its optimal shape. Firstly, the relationship between the location of the endwall contouring and the internal flow within the turbine cascade was investigated. Two patterns of contouring were made, one is only convex and another is just concave, and the secondary flow behavior of the turbine cascade was investigated respectively. Secondly, the shape was designed and the loss reduction effect was investigated by using optimization method. The optimized shape was manufactured by 3D-printer and experiment was conducted using cascade wind tunnel. The total pressure distributions were measured and compared with CFD results. Furthermore, flow near the endwall and the internal flow of the turbine cascade was experimentally visualized. The internal flow in the case of a flat wall (without contouring), with a fence, and with optimized endwall contouring were compared by experiment and CFD to extract the each feature.

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