Download or read book Enhanced Design of Turbo Jet LPT by Separation Control Using Phased Plasma Actuators written by and published by DIANE Publishing. This book was released on 2003 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Enhanced Design of Turbo Jet Lpt by Separation Control Using Phased Plasma Actuators written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-20 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work deals with the documentation and control of flow separation that occurs over turbine blades in the low-pressure turbine stage at low Reynolds numbers that exist at high altitude cruise. We utilize a specially constructed linear cascade that is designed to study the flow field over a generic LPT cascade consisting of Pratt & Whitney 'Pak B' shaped blades. This facility was constructed under a previous one-year NASA Glenn RC initiative. The center blade in the cascade is instrumented to measure the surface pressure coefficient distribution. Optical access allows two-component LDV measurement for boundary layer profiles. Experimental conditions have been chosen to give a range of chord Reynolds numbers from 10 to 100K, and a range of free-stream turbulence levels from u'/U(sub infinity)= 0.08 to 3 percent. The surface pressure measurements were used to define a region of separation and reattachment that depend on the free-stream conditions. The location of separation was found to be relatively insensitive to the experimental conditions. However, reattachment location was very sensitive to the turbulence level and Reynolds number. Excellent agreement was found between the measured pressure distributions and predictions from Euler and RANS simulations. Two-component LDV measurements are presently underway to document the mean and fluctuating velocity components in the boundary layer over the center blade for the range of experimental conditions. The fabrication of the plasma actuator is underway. These are designed to produce either streamwise vortices, or a downstream-directed wall jet. A precursor experiment for the former approach was performed with an array of vortex generators placed just upstream of the separation line. These led to reattachment except for the lowest Reynolds number. Progress has also been made on the proposed concept for a laterally moving wake. This involved constructing a smaller wind tunnel and molding an array of symmetric airfoi
Download or read book Enhanced Design of Turbo jet Lpt by Separation Control Using Phase Plasma Actuators Nasa cr 2003 212294 National Aeronautics and Spac written by United States. National Aeronautics and Space Administration and published by . This book was released on 2003* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Control of Flow Separation from the Deflected Flap of a High lift Airfoil Using Multiple Dielectric Barrier Discharge DBD Plasma Actuators written by Kristine L. McElligott and published by . This book was released on 2010 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: In current wing design, multiple flaps are incorporated into the trailing edge to allow mixing of high and low pressure sides to reduce flow separation. These flaps reduce the efficiency by adding weight and complexity to the aircraft. A single hinged flap would reduce these inefficiencies but is more susceptible to flow separation. Active flow control is a means by which the fluid flow over a body is deliberately altered and can be altered such that it becomes less likely to separate from the object. By energizing the flow, the degree of separation of the flow can be controlled, and this inherently controls lift. Dielectric barrier discharge (DBD) plasma actuators are a form of active flow control. These actuators are created by asymmetrically aligning two electrodes and adding a dielectric layer between the electrodes. When the electrodes are electrically connected, ionized air (plasma) travels from the exposed electrode towards the covered electrode. Collisions occur between the plasma and neutral air over the body, and momentum is transferred to the neutral air, effectively energizing it. The purpose of this study is to examine the lift enhancement and flow control authority that multiple DBD plasma actuators have on a high-lift airfoil when compared to the flow exhibited by non-controlled and single DBD plasma actuator controlled cases. Electrodes were mounted onto a simplified NASA Energy Efficient Transport airfoil near the flap. The airfoil was tested in a closed, recirculating wind tunnel operating at a Reynolds number of 240,000, 20° flap deflection angle and 0° degree angle of incidence. The actuators were independently powered in order to determine the most effective input parameters. Using multiple actuators operated in-phase has increased the lift and has delayed flow separation on the trailing edge flap when compared to baseline and single actuation cases.
Download or read book Separation Control Using Plasma Actuators Experimental Studies of Plasma Actuator Performance written by DartKen Poon and published by . This book was released on 2011 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Demonstration of Separation Delay with Glow Discharge Plasma Actuators written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-27 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modern low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2 percent) and high (2.5 percent) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control. Hultgren, Lennart S. and Ashpis, David E. Glenn Research Center NASA/TM-2003-212204/REV1, AIAA Paper 2003-1025, E-13807-1/REV1
Download or read book High lift Airfoil Separation Control with Dielectric Barrier Discharge Plasma Actuators written by Jesse Little and published by . This book was released on 2010 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This work examines the performance of dielectric barrier discharge (DBD) plasma actuators for controlling separation from the leading edge and trailing edge flap shoulder of a supercritical high-lift airfoil. DBD plasma actuators driven by both typical AC voltages (AC-DBD) and more developmental nanosecond duration pulses (NS-DBD) are investigated. Characterization of the two actuators shows that very different behavior is created when exciting the plasma discharge using these two waveforms. The AC-DBD plasma actuator functions through electrohydrodynamic effects that introduce zero net mass, but nonzero net momentum into the flow. Conversely, the electrohydrodynamic effects of the NS-DBD are quite weak suggesting thermal effects from rapid localized heating by the plasma are responsible for control authority. The performance of both devices as separation control actuators is tested on a high-lift airfoil system. The AC-DBD is effective for controlling turbulent boundary layer separation from a deflected trailing edge flap between Reynolds numbers of 240,000 and 750,000. Momentum coefficients for the AC-DBD plasma actuator are generally an order of magnitude lower than those usually employed for such studies yet control authority is still realized through amplification of natural vortex shedding from the flap shoulder. The corresponding lift enhancement is primarily due to upstream effects from increased circulation around the entire model rather than full separated flow reattachment to the deflected flap surface. Lift enhancement via instability amplification is found to be relatively insensitive to changes in angle of attack provided that the separation location and underlying dynamics do not change. Control authority decreases with increasing Reynolds number and flap deflection highlighting the necessity for further optimization of AC-DBD plasma actuators for use in realistic takeoff and landing transport aircraft applications. As a whole, these findings compare favorably to studies on a similar high-lift platform using piezoelectric driven zero net mass flux actuation. The NS-DBD plasma actuator is ineffective for controlling separation from the deflected trailing edge flap. However, the device is found to be superior to the tested AC-DBD plasma actuators for controlling leading edge separation and rivals the performance of a passive droop by extending the stall angle by six degrees in the Reynolds number range 750,000-1,000,000. Detailed flow diagnostics show the NS-DBD plasma actuator functions as an active trip for pre-stall incidence angles and generates coherent spanwise vortices that entrain freestream momentum into the separated region at post-stall angles. These structures are generated across all surveyed frequencies, but optimal dimensionless frequencies for controlling separation are in the range four to six depending on the incidence angle. The contrasting performance of the NS-DBD plasma actuator at the leading and trailing edge in comparison to the AC-DBD is discussed and recommendations for future work are provided.
Download or read book Separation Control Using Plasma Actuators in a High Pressure Bend written by Michael J. Arthur and published by . This book was released on 2014 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Plasma Actuators for Separation Control of Low Pressure Turbine Blades written by Junhui Huang and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Robust Feedback Control of Flow Separation Using Plasma Actuators written by Laura Pasquale and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mixing Control in Supersonic Rectangular Jets Using Plasma Actuators written by Robert M. Snyder and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The flow through the exhaust nozzle of a jet engine has been of crucial importance in aerospace applications over the past several decades. A variety of modifications can be made to the nozzles of high-speed jet engines to increase or decrease mixing between the exiting flow and the ambient air; including adding tabs, chevrons, or actuators. Localized arc filament plasma actuators (LAFPA) developed in the Gas Dynamics and Turbulence Laboratory at The Ohio State University have both high amplitude and bandwidth and are suitable for active control of high-speed, high Reynolds number flows. These actuators were implemented on a rectangular nozzle in order to optimize the efficiency of mixing enhancement between the jet and the ambient air. Actuators were tested for a Mach 2.0 flow over a wide range of forcing frequencies and the effects were evaluated using flow visualization techniques. Results show the effects of forcing frequency and other parameters on the development of large-scale structures within the flow. Flow visualization testing over a broad range of forcing frequencies and duty cycles revealed the presence of large coherent structures and thus most favorable mixing enhancement in the 6-8 kHz (StF = 0.15-0.2) range. The m = " 1 (flapping) mode produced a clear pattern of alternating structures within the aforementioned frequency band. It was also observed that the effect of varying duty cycle within this frequency range has little effect on the control authority.
Download or read book DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines written by David E. Ashpis and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of High Reynolds Number Supersonic Jets Using Plasma Actuators written by and published by . This book was released on 2010 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active flow control of jets with Localized Arc Filament Plasma Actuators (LAFPAs) is conducted over a wide range of the fully expanded jet Mach numbers (M(J) or simply jet Mach number). The jet Mach numbers covered in the present research are 0.9 (with a converging nozzle), 1.2 (overexpanded), 1.3 (perfectly expanded), and 1.4 (underexpanded) with a design Mach number 1.3. Additionally, limited experiments are carried out for an M(J) = 1.65 perfectly-expanded jet. The exit diameter is 2.54 cm (1 inch) for all cases and eight LAFPAs are equally distributed on the perimeter of a boron nitride nozzle extension. The jet spreading is strongly dependent on duty cycle, forcing frequency, and azimuthal modes. The performance of LAFPAs for jet spreading is investigated using two-dimensional particle image velocimetry (PIV). There is an optimum duty cycle, producing maximum jet spreading, for each forcing frequency. A relationship between the optimum duty cycle and forcing frequency is determined from the extensive results in the MJ 0.9, and this relation is used for all experiments. The effect of forcing frequency is investigated for a wide range of forcing Strouhal numbers (StDF = f(F)D/U(e), where f(F), D, and U(e), are forcing frequency, nozzle exit diameter, and jet exit velocity respectively), ranging from 0.09 to 3.0. The azimuthal modes (m) investigated are m = 0 - 3, +/-1, +/-2, and +/-4 - this comprises all modes available with eight actuators. The performance of LAFPAs does also strongly depend on the stagnation temperature of the jet and M(J). The effects of stagnation temperature are investigated for 1.0, 1.4, and 2.0 times the ambient temperature in M(J) 0.9 jet for very limited azimuthal modes and St(DF). In an M(J) 1.65 perfectly-expanded jet, the control authority of LAFPAs is investigated for only m = +/-1 and St(DF) tilde 0.3.
Download or read book Separation Control on High Angle of Attack Airfoil Using Plasma Actuators written by Martiqua L. Post and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines written by David E. Ashpis and published by . This book was released on 2011 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Investigation of Plasma Actuator Configurations for Flow Separation Control at Multiple Angles of Attack written by Thomas Kelsey West and published by . This book was released on 2012 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The primary objective of the study presented in this thesis was to analyze the effectiveness of aerodynamic plasma actuators as a means of active flow control over a low speed airfoil at multiple angles of attack each corresponding to two different flow separation mechanisms (i.e., laminar separation bubble and turbulent flow separation at stall conditions). Detailed parametric studies based on steady and unsteady Navier-Stokes simulations, modified to include the body force term created by the plasma actuator, were performed for a NACA 0012 airfoil at a chord Reynolds number of 105. In particular, parametric studies were performed to investigate the influence of the number, the location, the imposed body force magnitude (power input) and steady vs. unsteady operation of plasma actuators on the flow control effectiveness. First, the effectiveness of plasma actuators was studied when applied to the airfoil at a relatively low angle of attack, which involved the development of a laminar separation bubble (LSB). Next, the effectiveness of plasma actuators was analyzed at a high angle of attack where the stall of the airfoil occurs with a fully turbulent flow assumption. The results show that plasma actuators can provide significant improvement in aerodynamic performance for the flow conditions considered in this study. For LSB control, as much as a 50% improvement in the lift to drag ratio was observed. Results also show that the same improvement can be achieved using an unsteady or multiple actuators, which can require as much as 75% less power compared to a single, steady actuator. For the stalled airfoil case, as much as a 700% improvement in L/D was observed from a single, steady actuator. Note that this was achieved using a power input eight times higher than what was used for LSB control. Also, unsteady and multiple actuator configurations do not provide the same enhancement as the single, steady actuators. This was found to be due to the nature of the turbulent separation (trailing edge separation) at the stall condition that occurs for the selected airfoil and Reynolds number"--Abstract, leaf iii.
Download or read book Effects of Pulsation Frequency on Trailing Edge Plasma Actuators for Flight Control written by Frederick William Hamlin and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis details the aerodynamic testing of a dielectric barrier discharge (DBD) plasma actuator operating over a separation step created at the trailing edge of a modified NACA 0012 aerofoil. The work focuses specifically on the use of pulsed or interrupted plasma actuation as opposed to continuously driven actuation, to increase the change in the lift produced by activating the system. The behaviour of the actuation system is characterised in a lamina flow regime at a Reynolds number of 1.33 x 105 using force balance measurements. At zero incidence the actuator produced a peak change in CL of approximately 0.015. However, this result is sensitive to changes in the interruption frequency of the plasma, by changing the plasma drive waveform the system was able to produce both positive and negative changes in lift. A relationship was identified between the change in CL produced and the ratio of the plasma interruption frequency to the natural vortex shedding frequency. This effect was investigated using both time averaged particle image velocimetry (PIV) and instantaneous phase locked PIV images captured in sequence throughout the plasma interruption cycle. The phase locked images showed how variation in the pulsation frequency was able to produce bi-directional actuation by either constructively or destructively interfering with the vortex formation from the back of the separation step. This interference in turn altered the level of separation which was occurring, altering the degree of upwash in the wake and therefore the lift generated by the aerofoil. PIV images were also gathered for device operation at a Reynolds number of 2.3 x 104; this produced a much higher ratio of DBD jet energy to that of the freestream. These conditions showed modified actuator behaviour due to the increased authority over the flow. However, the data still showed a strong interdependence on the reinforcement or destruction of the vortex street by the actuator interruption. Furthermore, work was undertaken to develop an actuator topology based on thin metallised films along with a dielectric which was hardened against the chemical and electrical stresses present in a functioning DBD device. The failure mechanisms of metallised film actuators were investigated, and actuators with lifetimes exceeding 8 hours were demonstrated. A manufacture method for a silicon polymer (PDMS) - Kapton® laminate is detailed; this is shown to be highly resistant to both electrical breakdown and chemical attack by the oxygen plasma.
