scholarly journals Characterization of Aerodynamic Performance of Boundary-Layer-Ingesting Inlet Under Crosswind

2012 ◽  
Author(s):  
Meng-Sing Liou ◽  
Byung Joon Lee
Keyword(s):  
Boundary Layer ◽  
Total Pressure ◽  
Flow Characteristics ◽  
Vortex Generator ◽  
Propulsion System ◽  
Flow Distortion ◽  
Inlet System ◽  
Fuel Savings ◽  
Design Changes ◽  
And Performance

NASA has been studying future transport concepts, envisioned to be technically realizable in the timeframe of 2020–2030, to meet environmental and performance goals. One concept receiving considerable interest involves a propulsion system embedded into a hybrid wingbody aircraft. While offering significant advantages in fuel savings and noise reduction by this concept, there are several technical challenges that are not encountered in the current fleet and must be overcome so as to deliver target performance and operability. One of these challenges is associated with an inlet system that ingests a significantly thick boundary layer, developing along the wingbody surface, into a serpentine diffuser before the flow meeting fan blades. The flow is subject to considerable total pressure loss and distorted at the fan face, much more significantly than in the inlet system of conventional aircraft. In our previous studies [1, 2], we have shown that through innovative design changes on the airframe surface, it is possible to simultaneously increase total pressure recovery and decrease distortion in the flow, without resorting to conventional penalty-ridden flow control concepts, such as vortex generator or boundary layer bleeding/suction. In the current study, we are interested in understanding the following issues: how the embedded propulsion system performs under a crosswind condition by studying in detail the flow characteristics of two inlets, the baseline and another optimized previously under the cruise condition. With the insight, it is hoped that it can help in the follow-on study by devising effective strategies to minimize flow distortion arising from the integration of an embedded-engine system into an airframe to the level acceptable to the operation of engine fan.

Application of Boundary Layer Fences and Vortex Generators in Improving Performance of S-Duct Diffusers

2001 ◽  
Vol 124 (1) ◽  
pp. 136-142 ◽  
Author(s):  
R. K. Sullerey ◽  
Sourabh Mishra ◽  
A. M. Pradeep
Keyword(s):  
Boundary Layer ◽  
Total Pressure ◽  
Static Pressure ◽  
Transverse Velocity ◽  
Pressure Rise ◽  
Vortex Generator ◽  
Substantial Improvement ◽  
Vortex Generators ◽  
Flow Distortion ◽  
Flow Quality

An experimental investigation was undertaken to study the effect of various fences and vortex generator configurations in reducing the exit flow distortion and improving total pressure recovery in two-dimensional S-duct diffusers of different radius ratios. Detailed measurements including total pressure and velocity distribution, surface static pressure, skin friction, and boundary layer measurements were taken in a uniform inlet flow at a Reynolds number of 7.8×105. These measurements are presented here along with static pressure rise, distortion coefficient, and the transverse velocity vectors at the duct exit determined from the measured data. The results indicate that substantial improvement in static pressure rise and flow quality is possible with judicious deployment of fences and vortex generators.

Impact of a Combination of Micro-Vortex Generator and Boundary Layer Suction on Performance in a High-Load Compressor Cascade

2018 ◽  
Author(s):  
Shan Ma ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Chuanle Liu
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Vortex Generator ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Control Methods ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
Micro Vortex Generator

The performance of a compressor cascade is considerably influenced by flow control methods. In this paper, the synergistic effects of combination between micro-vortex generators (MVG) and boundary layer suction (BLS) are discussed in a high-load compressor cascade. Seven cases, which are grouped by a kind of micro-vortex generator and boundary layer suction with three locations, are investigated to control secondary flow effects and enhance the aerodynamic performance of the compressor cascade. The MVG is mounted on the end-wall in front of the passage. The rectangle suction slot with three radial positions is installed on the blade suction surface near the trailing edge. The numerical results show that: at the design condition, the total pressure loss is effectively decreased as well as the static pressure coefficient increase when the combined MVG and SBL method (COM) is used, which is superior to MVG in an aerodynamic performance. At the stall condition, the induced vortex coming from MVG could mix the low-energy fluid and mainstream, which result in the reduced separation, and the total pressure loss decreased by 11.54% when the suction flow ratio is 1.5%. The total pressure loss decreases by 14.59% when the COM control methods are applied.

scholarly journals The Effect of Inlet Boundary Layer Thickness on the Flow Within an Annular S-Shaped Duct

1998 ◽  
Author(s):  
Toyotaka Sonoda ◽  
Toshiyuki Arima ◽  
Mineyasu Oana
Keyword(s):  
Boundary Layer ◽  
Flow Pattern ◽  
Pressure Loss ◽  
Total Pressure ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Vortex Pair ◽  
Separated Flow ◽  
Total Pressure Loss ◽  
Centrifugal Impeller

Experimental and numerical investigations were carried out to gain a better understanding of the flow characteristics within an annular S-shaped duct, including the effect of the inlet boundary layer (IBL) on the flow. A duct with six struts and the same geometry as that used to connect compressor spools on our experimental small two-spool turbofan engine was investigated. A curved downstream annular passage with a similar meridional flow path geometry to that of the centrifugal compressor has been fitted at the exit of S-shaped duct. Two types of the IBL (i.e. thin and thick IBL) were used. Results showed that large differences of flow pattern were observed at the S-Shaped duct exit between two types of the IBL, though the value of “net” total pressure loss has not been remarkably changed. According to “overall” total pressure loss, which includes the IBL loss, the total pressure loss was greatly increased near the hub as compared to that for a thin one. For the thick IBL, a vortex pair related to the hub-side horseshoe vortex and the separated flow found at the strut trailing edge has been clearly captured in the form of the total pressure loss contours and secondary flow vectors, experimentally and numerically. The high-pressure loss regions on either side of the strut wake near the hub may act on a downstream compressor as a large inlet distortion, and strongly affect the downstream compressor performance. There is a much-distorted three-dimensional flow pattern at the exit of S-Shaped duct. This means that the aerodynamic sensitivity of S-Shaped duct to the IBL thickness is very high. Therefore, sufficient carefulness is needed to design not only downstream aerodynamic component (for example centrifugal impeller) but also upstream aerodynamic component (LPC OGV).

scholarly journals Design Approach for an Optimum Prop-Fan Propulsion System

1985 ◽  
Author(s):  
Gerald L. Brines
Keyword(s):  
Short Range ◽  
Propulsion System ◽  
Operating Costs ◽  
Fuel Savings ◽  
Fuel Burn ◽  
Trade Offs ◽  
Counter Rotation ◽  
Medium Range ◽  
And Performance ◽  
Design Options

The predicted potential performance of the Prop-Fan offers a major improvement in the energy efficiency of future, short-range to medium-range transports. This paper describes the approach taken in designing an optimum Prop-Fan propulsion system. Trade-offs in the configuration(s) and performance are discussed, as are the important aspects of integrating the propeller, gearbox, engine, inlet, exhaust, and nacelle. Realizing the impressive potential fuel savings of the Prop-Fan will require very careful engine/airframe integration. Design options that will be compared are: a single-rotation versus counter-rotation arrangement, a tractor versus pusher installation, and wing versus fuselage mounting. In summary, the performance of turbofan powered and Prop-Fan powered, short-haul transports will be compared in detail by using fuel burn, operating costs, and noise as criteria.

Separation Control on a Very High Lift Low Pressure Turbine Airfoil Using Pulsed Vortex Generator Jets

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Ralph J. Volino ◽  
Olga Kartuzova ◽  
Mounir B. Ibrahim
Keyword(s):  
Boundary Layer ◽  
Total Pressure ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Separation Control ◽  
Suction Surface ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Very High

Boundary layer separation control has been studied using vortex generator jets (VGJs) on a very high lift, low-pressure turbine airfoil. Experiments were done under high (4%) freestream turbulence conditions on a linear cascade in a low speed wind tunnel. Pressure surveys on the airfoil surface and downstream total pressure loss surveys were documented. Instantaneous velocity profile measurements were acquired in the suction surface boundary layer. Cases were considered at Reynolds numbers (based on the suction surface length and the nominal exit velocity from the cascade) of 25,000 and 50,000. Jet pulsing frequency, duty cycle, and blowing ratio were all varied. Computational results from a large eddy simulation of one case showed reattachment in agreement with the experiment. In cases without flow control, the boundary layer separated and did not reattach. With the VGJs, separation control was possible even at the lowest Reynolds number. Pulsed VGJs were more effective than steady jets. At sufficiently high pulsing frequencies, separation control was possible even with low jet velocities and low duty cycles. At lower frequencies, higher jet velocity was required, particularly at low Reynolds numbers. Effective separation control resulted in an increase in lift and a reduction in total pressure losses. Phase averaged velocity profiles and wavelet spectra of the velocity show the VGJ disturbance causes the boundary layer to reattach, but that it can reseparate between disturbances. When the disturbances occur at high enough frequency, the time available for separation is reduced, and the separation bubble remains closed at all times.

Experimental and Computational Investigations of Low-Pressure Turbine Separation Control Using Vortex Generator Jets

2009 ◽  
Author(s):  
Ralph J. Volino ◽  
Olga Kartuzova ◽  
Mounir B. Ibrahim
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Total Pressure ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Separation Control ◽  
Airfoil Surface ◽  
Low Pressure Turbine ◽  
Vortex Generator Jets

Boundary layer separation control has been studied using vortex generator jets (VGJs) on a very high lift, low-pressure turbine airfoil. Experiments were done under low freestream turbulence conditions on a linear cascade in a low speed wind tunnel. Pressure surveys on the airfoil surface and downstream total pressure loss surveys were documented. Cases were considered at Reynolds numbers (based on the suction surface length and the nominal exit velocity from the cascade) of 25,000, 50,000 and 100,000. Jet pulsing frequency, duty cycle, and blowing ratio were all varied. In all cases without flow control, the boundary layer separated and did not reattach. With the VGJs, separation control was possible even at the lowest Reynolds number. Pulsed VGJs were more effective than steady jets. At sufficiently high pulsing frequencies, separation control was possible even with low jet velocities and low duty cycles. At lower frequencies, higher jet velocity was required, particularly at low Reynolds numbers. Effective separation control resulted in an increase in lift of up to 20% and a reduction in total pressure losses of up to 70%. Simulations of the flow using an unsteady RANS code with the four equation Transition-sst model produced good agreement with experiments in cases without flow control, correctly predicting separation, transition and reattachment. In cases with VGJs, however, the CFD did not predict the reattachment observed in the experiments.

Performance and Design of Straight, Two-Dimensional Diffusers

1967 ◽  
Vol 89 (1) ◽  
pp. 141-150 ◽  
Author(s):  
L. R. Reneau ◽  
J. P. Johnston ◽  
S. J. Kline
Keyword(s):  
Boundary Layer ◽  
Flow Regime ◽  
Flow Characteristics ◽  
Performance Data ◽  
Center Line ◽  
Two Dimensional ◽  
Rational Basis ◽  
Primary Flow ◽  
Wide Range ◽  
And Performance

Performance data and flow characteristics for subsonic, two-dimensional, straight center line diffusers are presented. The four primary flow regimes which can occur are described and presented as functions of overall diffuser geometry. The performance of both stalled and unstalled diffusers is mapped for a wide range of geometries and inlet boundary layer thicknesses. An understanding of the relationships between flow regime and performance leads to a rational basis for diffuser design. The important maxima of performance and their location on the performance maps are presented. Both the range of data and correlations of optima of performance are extended beyond previous results.

The Design and Performance of Axially Symmetrical Contoured Wall Diffusers Employing Suction Boundary Layer Control

1975 ◽  
Vol 97 (1) ◽  
pp. 125-130 ◽  
Author(s):  
C. D. Nelson ◽  
T. Yang ◽  
W. G. Hudson
Keyword(s):  
Boundary Layer ◽  
Performance Prediction ◽  
Flow Characteristics ◽  
Boundary Layer Control ◽  
Gas Turbine Combustor ◽  
High Area ◽  
Straight Wall ◽  
And Performance ◽  
The Stability ◽  
Layer Control

This paper presents a procedure for the design and the performance prediction of axially symmetrical contoured wall diffusers employing suction boundary layer control. An inverse problem approach was used in the potential flow design of the diffuser wall contours. Three short (L/l ≤ 5.15), high area ratio (2.5 and 3) diffusers were tested in the study and were found to have effectiveness values in excess of 90 percent (comparable straight wall diffusers have effectiveness <40 percent) while requiring suction flows of less than 10 percent of the inlet flow. The experimentally observed flow characteristics, the stability of flows within the diffusers, are also described. Because of their high effectiveness and short length these diffusers appear to be ideally suited for use as gas turbine combustor diffusers and as turbine discharge diffusers.

scholarly journals Installed Performance Assessment of an Array of Distributed Propulsors Ingesting Boundary Layer Flow

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Chana Goldberg ◽  
Devaiah Nalianda ◽  
Panagiotis Laskaridis ◽  
Pericles Pilidis
Keyword(s):  
Boundary Layer ◽  
Fuel Consumption ◽  
Flow Characteristics ◽  
Propulsion System ◽  
Accounting System ◽  
Propulsion Systems ◽  
Local Flow ◽  
System A ◽  
Layer Flow

Conventional propulsion systems are typically represented as uninstalled systems to suit the simple separation between airframe and engine in a podded configuration. However, boundary layer ingesting systems are inherently integrated, and require a different perspective for performance analysis. Simulations of boundary layer ingesting propulsions systems must represent the change in inlet flow characteristics, which result from different local flow conditions. In addition, a suitable accounting system is required to split the airframe forces from the propulsion system forces. The research assesses the performance of a conceptual vehicle, which applies a boundary layer ingesting propulsion system—NASA's N3-X blended wing body aircraft—as a case study. The performance of the aircraft's distributed propulsor array is assessed using a performance method, which accounts for installation terms resulting from the boundary layer ingesting nature of the system. A “thrust split” option is considered, which splits the source of thrust between the aircraft's main turbojet engines and the distributed propulsor array. An optimum thrust split (TS) for a specific fuel consumption at design point (DP) is found to occur for a TS value of 94.1%. In comparison, the optimum TS with respect to fuel consumption for the design 7500 nmi mission is found to be 93.6%, leading to a 1.5% fuel saving for the configuration considered.

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