High-Frequency Pressure Measurements for Unstart Detection in Scramjet Isolators

Donbar, Jeffrey M.; Linn, Graham J.; Afb, Wright-Patterson; Sukumar, Srikant; Akella, Maruthi R.

doi:10.2514/6.2010-6557

Cited by 31 publications

(6 citation statements)

References 24 publications

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“…If the heat release in the combustor is sufficiently large at a given instant in time, the pressure rise cannot be accommodated within the given isolator length. In such an instance, the shock train could be forced upstream out of the isolator and could induce inlet unstart [4]. A cavity could be inserted in the isolator section to control the shock train and to arrest the potential upstream movement of the shock train.…”

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confidence: 99%

Control of High Subsonic Cavity Flow Using Plasma Actuators

et al. 2014

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Localized arc filament plasma actuators were used to control pressure fluctuations in a cavity with a depth of 12.7 mm and length-to-depth ratio of 4.86. The rear wall of the cavity is inclined 30 deg with respect to the upstream flow, and the cavity length is 61.7 mm. Five actuators were uniformly distributed along the span of the cavity, 1 mm upstream of the cavity leading edge. Experiments were conducted in a flow with a Mach number of 0.6 and a Reynolds number based on the cavity depth of 2 × 10 5. Forcing was conducted quasi-two-dimensionally (all actuators operated in phase) and threedimensionally (actuators operated out of phase). The objective of the research was twofold: first, to demonstrate that the peak tone as well as the broadband pressure fluctuations can be suppressed in a strongly resonating cavity, and second, the resonance can be re-established and the peak tone as well as the broadband pressure fluctuations can be amplified in a weakly resonating cavity. Time-resolved pressure and particle-image-velocimetry measurements were used to assess the effectiveness of the actuators and to explore the physics of the flow. Although both quasi-two-dimensional and threedimensional controls were successful in controlling the flow, the control was less sensitive to forcing frequency change in the latter in achieving the first objective. The results also showed that, although there are many forcing frequency options in achieving the first objective, the options are limited to frequencies near the dominant (even though weak) Rossiter modes in re-establishing the feedback in a weakly resonating cavity.

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confidence: 99%

Control of High Subsonic Cavity Flow Using Plasma Actuators

et al. 2014

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“…Instantaneous high thermal energy release in the combustor could significantly increase the backpressure and force the shock train out of the isolator into the inlet. 8 This phenomenon, termed unstart, must be prevented for stable scramjet operation. It has been demonstrated that a resonating cavity can increase the downstream blockage needed to unstart a model isolator (straight duct) 9 ; however, no optimization of the cavity geometry for this purpose was pursued.…”

Section: Introductionmentioning

confidence: 99%

Supersonic Cavity Flow Control for Scramjet Applications

Webb

Samimy

2016

8th AIAA Flow Control Conference

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Cavity flows are present in many aerospace applications. A novel application for cavity flow is to augment the back-pressure margin of a scramjet isolator. Previous work investigated the ability of a cavity to trap an unstart shock generated by a blockage in a Mach 2.24 flow. This work performs a preliminary optimization of the cavity geometry and flow control parameters for this purpose. It was found that the isolator back-pressure margin could be increased 21% by the addition of a cavity. Understanding the drag of a controlled, supersonic cavity is of crucial importance to the proposed application. PIV velocity measurements have been used to calculate the drag penalty of a rectangular, controlled cavity relative to the straight duct used in the back-pressure margin experiments. All cavity cases had higher drag than the straight duct. The results of both the back-pressure margin and drag investigations showed trends in direct contradiction of the working hypothesis of the relevant flow dynamics. More research is needed to determine the appropriate revisions to the working hypothesis.

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“…A large number of studies have been conducted implementing various schemes including summation of pressures, power spectral density change detection algorithms, and other novel approaches. [6][7][8][9][10][11] A final aspect of the unstart problem that has been investigated consists of research into preventing or controlling the unstart process. Investigations into unstart prevention and shock position control have been conducted with varying levels of success.…”

Section: Introductionmentioning

confidence: 99%

Closed-loop Control of Shock Location in Mach 1.8 Direct Connect Wind Tunnel

Ashley

Szmuk

Clemens

et al. 2014

7th AIAA Flow Control Conference

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This paper presents the design and implementation of a closed-loop control scheme to regulate shock location within a Mach 1.8 wind tunnel isolator test section. As part of the feedback controller, the sensing scheme for shock localization utilizes a set of high frequency Kulite pressure transducers to sample the static pressure at various points along the wind tunnel test section. A geometry-based shock localization algorithm is then executed at 250 Hz to determine the location of the shock in real time. The closed-loop controller generates actuation commands for a motorized flap downstream of the test section every 100 ms toward regulating the shock at the desired position. Several forms of closed-loop implementation are addressed including: (a) simple logic-based controllers; (b) Proportional-Integral (PI) controllers, and (c) Proportional-Derivative (PD) controllers. In addition to using the geometry-based shock localization schemes, the paper also describes the implementation of a novel Kalman-filter-based framework for fusing estimates from other shock localization schemes such as standard deviation and sum-of-squares. It also explores important design criteria that should be considered for satisfactory control performance as a function of pressure transducer spacing, shock localization speed, flapmotor's actuation speed and actuator resolution. Experimental results are presented for various test scenarios such as regulation of the shock location in the presence of stagnation pressure disturbances as well as tracking of a time-varying reference input. Performance and robustness analysis of the control system during these tests is discussed. Further areas of improvement for the closed-loop control system in both hardware and software are discussed along with possible applications. Nomenclature DTR= Dense Transducer Region PD = Proportional-Derivative

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High-Frequency Pressure Measurements for Unstart Detection in Scramjet Isolators

Cited by 31 publications

References 24 publications

Control of High Subsonic Cavity Flow Using Plasma Actuators

Control of High Subsonic Cavity Flow Using Plasma Actuators

Supersonic Cavity Flow Control for Scramjet Applications

Closed-loop Control of Shock Location in Mach 1.8 Direct Connect Wind Tunnel

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