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

2021 ◽  
Vol 11 (11) ◽  
pp. 5158
Author(s):  
Grigore Cican ◽  
Marius Deaconu ◽  
Daniel-Eugeniu Crunteanu
Keyword(s):  
Noise Reduction ◽  
Compression Ratio ◽  
Test Bench ◽  
Jet Noise ◽  
Equivalent Diameter ◽  
Normal Functioning ◽  
Fuel Flow ◽  
Turbojet Engine ◽  
Propulsion Force ◽  
Chevron Nozzles

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.

Noise analysis of the turbojet and turbofan engine tests

2013 ◽  
Vol 228 (13) ◽  
pp. 2414-2423
Author(s):  
Jingjing Huang ◽  
Longxi Zheng
Keyword(s):  
Power Spectrum ◽  
Noise Reduction ◽  
Spectrum Analysis ◽  
Test Bench ◽  
Power Spectrum Analysis ◽  
Noise Power ◽  
Far Field ◽  
Turbofan Engine ◽  
Turbojet Engine ◽  
Field Noise

Aerogine noise leads to environment pollution largely when aerogine is tested. In this paper, the power spectrum analysis method of the aeroengine test noise was discussed, and the noise measurement and analysis experiments of a turbojet engine and a turbofan engine tests were carried out. The noise level, main noise resource, and noise characteristics of the two turbojet and turbofan engines were analyzed. Meanwhile, the indoor noise and far-field noise of the turbojet engine were both measured, the noise spread characteristics were analyzed and the noise reduction performance of the test bench was evaluated. The noise generated by the turbojet engine test had the discrete characteristic of high frequency. The higher frequencies when peak values occurred were the blade passage frequencies and the noises with lower frequencies were the broad band noises, especially the jet noise, and the maximum of the peak values occurred at the basic frequencies or harmonic frequencies of the compressor. Meanwhile, the noises generated by the turbofan engine, focused on the high frequencies and the peak values corresponded to the rotation noise of the fan blades. The experimental results were consistent with the theory basically, which indicated that the aeroengine operating status information could be identified by the noise power spectrum analysis. In addition to the aeroengine noise reduction research, the noise power spectrum analysis could also be used to diagnose the fault of the aeroengine structure and performance. On the other hand, the indoor and far-field noise measurement experimental results implied that the noise was suppressed from 136 dB to 85 dB and could provide the reference to the noise reduction design of the aeroengine test bench.

Effect of Chevron Nozzles on Turbojet Engine Performance and Jet Noise

2017 ◽  
Vol 2017.54 (0) ◽  
pp. H044
Author(s):  
Gakuyo TAMADA ◽  
Makoto MIYAKE ◽  
Toshiaki TSUCHIYA
Keyword(s):  
Engine Performance ◽  
Jet Noise ◽  
Turbojet Engine ◽  
Chevron Nozzles

Analysis of Jet-Noise-Reduction Concepts by Large-Eddy Simulation

2007 ◽  
Vol 6 (3) ◽  
pp. 243-285 ◽  
Author(s):  
Michael L. Shur ◽  
Philippe R. Spalart ◽  
Michael Kh. Strelets ◽  
Andrey V. Garbaruk
Keyword(s):  
Noise Reduction ◽  
Low Cost ◽  
Jet Noise ◽  
Physical Models ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Chevron Nozzles ◽  
Automatic Activation ◽  
Computational Resources ◽  
Flux Limiters

The paper outlines the latest improvements to a CFD/CAA numerical system developed by the authors starting in 2001, and presents its application to the evaluation of three noise-reduction concepts. The improvements include a two-step RANS-LES approach to represent complex nozzles much more faithfully, and an accurate algorithm for shock capturing in LES, now based on local automatic activation of flux-limiters. The noise-reduction concepts considered are: beveled nozzles, dual nozzles with fan-flow deflection, and chevron nozzles. The simulations are carried out on PC clusters with at most six processors and on rather modest grids (2–4 million nodes). Nonetheless, in most cases the system is close to the 2–3 dB target accuracy both in terms of directivity and spectrum, while limited in terms of frequency (to a diameter Strouhal number that ranges from 2 to 4, depending on the grid used and the flow regime). Although this limitation is significant, especially for chevron nozzles, the overall message of the paper is that the available CFD/CAA numerical and physical models, properly combined, are capable of predicting the noise of rather complex jets with affordable computational resources, and already today can be helpful in the rapid low-cost analysis of noise-reduction concepts.

Study of Jet Noise Reduction on Separated Exhaust System Using Chevron Nozzles

2014 ◽  
Vol 1078 ◽  
pp. 228-234
Author(s):  
Wan Ren Shao ◽  
Xi Hai Xu ◽  
Jing Yu He ◽  
Fei Wu
Keyword(s):  
Noise Reduction ◽  
Jet Noise ◽  
Exhaust System ◽  
Scale Model ◽  
Low Frequencies ◽  
Chevron Nozzles ◽  
Field Noise ◽  
Bypass Ratio ◽  
Computational Predictions ◽  
Noise Spectra

The jet noise reduction of chevron nozzles was investigated on high bypass ratio turbofan engine separated exhaust system using both computational predictions and scale model experiments. Six different exhaust nozzles are designed including one baseline nozzle and five different chevron nozzles. The jet noise experiments were carried out in the anechoic chamber. Tam and Auriault’s jet noise prediction theory and MGBK theory were used to predict the noise spectra of different exhaust nozzles. The results show that the far-field noise spectra as well as the noise reduction benefits of chevrons are predicted correctly by the two theories although some discrepancies occur at the high frequency range, and Tam and Auriault’s jet noise theory can give relatively more accurate prediction results. chevron nozzles reduce jet noise at the low frequencies, but increase it at high frequencies.

Experimental Analysis for Jet Noise Reduction of Chevron Pylon-Based Nozzles

2014 ◽  
Vol 1078 ◽  
pp. 183-186 ◽  
Author(s):  
Jing Yu He ◽  
Ying Bo Xu
Keyword(s):  
Noise Reduction ◽  
Experimental Analysis ◽  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Jet Noise ◽  
Separate Flow ◽  
Frequency Noise ◽  
Chevron Nozzle ◽  
Chevron Nozzles

The experimental analysis is conducted for jet noise reduction of separate flow chevron pylon-based nozzles at takeoff condition. The experimental results indicate that the pylon makes a noise reduction at low-frequency but produces an increase at high-frequency, together with an overall sound pressure reduction below the pylon. Compared to chevron nozzle without pylon, the adding of a pylon reduces noise benefit of chevron nozzles found in the isolated nozzle without a pylon. The best low-frequency noise reduction is located below the pylon where peak noise reduction is as high as about 1.3dB on frequency spectrum.

Sign in / Sign up

Export Citation Format

Share Document