A study of noise reduction mechanisms of jets with fluid inserts

Prasad, Chitrarth; Morris, Philip J.

doi:10.1016/j.jsv.2020.115331

Cited by 39 publications

(30 citation statements)

References 40 publications

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“…Due to disadvantages, such as delayed convergence and the complexity of the phase shift mechanism, a unique technique was used that does not use secondary path modeling [62] and the sensitivity of noise to system uncertainties [63]. Fluid inserts reduce the convection speed of wave packets in the jet shear layer, resulting in a reduced Mach wave radiation angle [64].…”

Section: Noise Controlmentioning

confidence: 99%

A Critical Review of Supersonic Flow Control for High-Speed Applications

2021

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In high-speed fluid dynamics, base pressure controls find many engineering applications, such as in the automobile and defense industries. Several studies have been reported on flow control with sudden expansion duct. Passive control was found to be more beneficial in the last four decades and is used in devices such as cavities, ribs, aerospikes, etc., but these need additional control mechanics and objects to control the flow. Therefore, in the last two decades, the active control method has been used via a microjet controller at the base region of the suddenly expanded duct of the convergent–divergent (CD) nozzle to control the flow, which was found to be a cost-efficient and energy-saving method. Hence, in this paper, a systemic literature review is conducted to investigate the research gap by reviewing the exhaustive work on the active control of high-speed aerodynamic flows from the nozzle as the major focus. Additionally, a basic idea about the nozzle and its configuration is discussed, and the passive control method for the control of flow, jet and noise are represented in order to investigate the existing contributions in supersonic speed applications. A critical review of the last two decades considering the challenges and limitations in this field is expressed. As a contribution, some major and minor gaps are introduced, and we plot the research trends in this field. As a result, this review can serve as guidance and an opportunity for scholars who want to use an active control approach via microjets for supersonic flow problems.

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Section: Noise Controlmentioning

confidence: 99%

A Critical Review of Supersonic Flow Control for High-Speed Applications

2021

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“…Several technology concepts have been explored, for example the use of bevelled nozzles [87,88] and tabbed nozzles [89]. More favoured recently, principally due to their ability to be switched off to avoid performance losses during flight, are variations of the active control application of 'fluid tabs' [90], successfully applied to supersonic jets by Prasad and Morris [91,92]. Multiple injectors using air bled off the by-pass stream are located in the divergent section of the nozzle.…”

Section: Design For Noise Reductionmentioning

confidence: 99%

Propulsive jet aerodynamics and aeroacoustics

McGuirk

2021

Aeronaut. j.

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Comprehensive understanding of propulsive jet aerodynamics and aeroacoustics is key to engine design for reduced jet noise and infra-red signature in civil and military aerospace, respectively. Illustrated examples are provided of other aerodynamic/aeroacoustic problems involving jet development, including chevron nozzles, increased jet/wing/flap interference (as fan diameter increases), high acoustic environment (and potentially damaging screech) of supersonic jets on carrier decks and the strongly Three-Dimensional (3D) unsteady flow during the in-ground effect operation of Short Take-Off and Vertical Landing (STOVL) aircraft. To date, laboratory/rig test measurements have primarily been used to identify design solutions; increased use of Computational Fluid Dynamics (CFD) would help achieve cost/time reductions, but Reynolds-Average Navier–Stokes (RANS) CFD with statistical turbulence modelling has proven inadequate for such flows. The scenarios described are far removed from flows used to calibrate model constants, and predictive accuracy demands detailed insight into unsteady flow. Large-Eddy Simulation (LES), whilst computationally more demanding, offers a potential solution. Research undertaken to assess LES capability to address the challenges described is reviewed here. This demonstrates that tremendous progress has been made, indicating that LES can provide sufficiently accurate predictions, representing high value for engineering design. A series of validation studies of increasing realism to practical engineering systems is presented to underpin this conclusion. Finally, areas for further work are suggested to support the combined application of RANS and LES that is probably the optimum way forward.

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“…These solutions were proposed for the first time by the Lighthill in 1952 [13], and since then, these were studied and developed, and complex geometries resulted. For example, the fluid chevrons [14,15], stepped nozzles [16], and nozzle are manufactured from smart material [17]. As was mentioned before, these solutions were heavily studied, but there are no studies in which the nozzle with chevrons, to be mounted on a turbojet engine, and the performance influences are assessed [18].…”

Section: Introductionmentioning

confidence: 99%

Impact of Using Chevrons Nozzle on the Acoustics and Performances of a Micro Turbojet Engine

Cican

Deaconu

2021

Applied Sciences

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This paper presents a study regarding the noise reduction of the turbojet engine, in particular the jet noise of a micro turbojet engine. The results of the measurement campaign are presented followed by a performances analysis which is based on the measured data by the test bench. Within the tests, beside the baseline nozzle other two nozzles with chevrons were tested and evaluated. First type of nozzle is foreseen with eight triangular chevrons, the length of the chevrons being L = 10 percentages from the equivalent diameter and an immersion angle of I = 0 deg. For the second nozzle the length and the immersion angle were maintained, only the chevrons number were increased at 16. The micro turbojet engine has been tested at four different regimes of speed. The engine performances were monitored by measuring the fuel flow, the temperature in front of the turbine, the intake air flow, the compression ratio, the propulsion force and the temperature before the compressor. In addition, during the testing, the vibrations were measured on axial and radial direction which indicate a normal functioning of the engine during the chevron nozzles testing. Regarding the noise, it was concluded that at low regimes the noise doesn’t presents any reduction when using the chevron nozzles, while at high regimes an overall noise reduction of 2–3 dB(A) was achieved. Regarding the engine performances, a decrease in the temperature in front of the turbine, compression ratio and the intake air and fuel flow was achieved and also a drop of few percent of the propulsion force.

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A study of noise reduction mechanisms of jets with fluid inserts

Cited by 39 publications

References 40 publications

A Critical Review of Supersonic Flow Control for High-Speed Applications

A Critical Review of Supersonic Flow Control for High-Speed Applications

Propulsive jet aerodynamics and aeroacoustics

Impact of Using Chevrons Nozzle on the Acoustics and Performances of a Micro Turbojet Engine

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