Computational Investigation of Two-Dimensional Ejector Performance

1. Create and Deliver Superior Products Through Innovative Minds Computational Investigation of Two-Dimensional Ejector Performance validation and extension of an experimental investigation Rich Margason Paul Bevilaqua May 21, 2011

2. Objective • Validate 2010 experimental investigation* of a 2-D ejector using computational fluid dynamic solutions of the Navier-Stokes equations • Extend range of selected variables to demonstrate their effect on ejector performance; variables included primary jet blowing configuration, shroud chord length, deflection of the shroud trailing edge • * Bonner, Amie A; A Parametric Variation on a Two-Dimensional Thrust-Augmenting Ejector, M.S. Thesis, California State Polytechnic University, Pomona, 2010

3. Figure 1 Thrust Augmenting Ejector Thrust Augmenting Ejector Suction forces primary jet thrust • An ejector is a jet pump that uses entrainment by an engine exhaust to increase mass flow • An ejector consists of a primary jet and a duct formed by two shroud flaps • The jet thrust is increased by the suction force that the entrained flow induces on the duct inlet • The suction force is determined by flap length C and separation distance W as well as flap deflection angle d Color scale is proportional to velocity

4. NASA Ejector Flap STOL Aircraft (QSRA)

5. XFV-12A Ejector Wing Aircraft

6. Diffuser Area Ratio Momentum Theory Calculation of Ejector Performance Parabolic Flow Assumption Gives Incorrect Results for Large Inlets

7. Predictions of Lifting Surface Theory • Momentum Theory Gives Correct Results for Small Inlets • Lifting Surface Theory Gives Correct Results for Large Inlets • Combined, These Theories Suggest a Performance Envelope Lifting Surface Theory Momentum Theory

8. Ejector Parameters • Primary jet exit area is A0 (centerbody blowing case is shown below) • Ejector throat area A2 is varied by changing the distance W between the flaps • Ejector exit area A3 is varied by the flap angle dand flap length C • Geometric non-dimensional parameters: C/W, A3/A0 , A3/A2 • Thrust augmentation ratio f is the performance parameter d A2 W A3 A0 C

9. Bonner 2-D Ejector Tests Conducted in 2010 Shroud Flap Nozzle

10. Ejector Test Variables Length, C Width, W Area Ratio, A3/A2

11. CFD Centerbody Blowing Axial Velocities

12. Centerbody Blowing Case • Recent experiment/CFD data for three shroud chord lengths C showed the following augmentation ratio f correlation : • 5 & 11.25 shroud inch exp/CFD cases agree • 2D CFD 17.5 inch shroud case was much greater than experiment which may have had flow separation

13. Blowing Centerbody and Shroud

14. Centerbody & Shroud BlowingCFD solution • Centerbody & shroud blowing CFD results are compared with experimental data with centerbody blowing only cases • Total primary thrust was equal for all of these cases • Dividing the primary thrust between the centerbody and shroud increased f by about 0.2

15. Effect of Chord Length and A2/A0 on f CFD solution • Augmentation ratio f increases at low C/W values with A2/A0 (or W) increases • After f reaches a maximum value, there are scrubbing losses on the longer flaps that reduce f • The A2/A0 = 4 case has a small W distance which appears to inhibit entrainment which reduces f

16. Deflected Shroud Trailing Edge with Centerbody & Shroud BlowingCFD Solution

17. Deflected Shroud Trailing Edge with Centerbody & Shroud BlowingCFD Solution • A3/A2 = 1 with zero degrees of shroud trailing edge deflection • A3/A2 > 1 is achieved with increasing width at the ejector exit plane • Shroud trailing edge deflection initially increases f until a maximum value is achieved • Further deflection reduces f • Maximum f increases with increasing shroud chord length

18. Conclusions • Recent experiment/CFD data comparisons for an ejector with centerbody blowing and three shroud chord lengths C showed • agreement for shroud chord lengths of 5 and 11.25 inches • disagreement for a shroud chord length of 17.5 inches; further tests are needed to determine if there is flow separation in the experiment • CFD calculations for the centerbody blowing cases were done for a family of chord lengths and showed how augmentation ratio f increases as ejector width increases • CFD calculations were done with the primary jet blowing split between the centerbody and the shroud • Results showed that f increased about 0.2 compared with blowing only from the centerbody • Further results with deflected shroud trailing edges showed f increases of 0.2 to 0.4 depending on the shroud chord length