The air-turbo-rocket(ATR)engine is a promising propulsion plant for achieving numerous surface and air launched missile missions.The application of lobed mixer in the ATR combustor can promote the mixing of the fuelri...The air-turbo-rocket(ATR)engine is a promising propulsion plant for achieving numerous surface and air launched missile missions.The application of lobed mixer in the ATR combustor can promote the mixing of the fuelrich gas and the air,thus improving the engine performance significantly.The numerical simulation method was conducted to explore the effects of lobe peak-to-trough width ratio on mixing and combustion performance in ATR combustors.Results show that:For a given peak lobe width b1,the combustion efficiency and total pressure loss decrease with the increase of trough lobe width b2;For a given b2,the combustion efficiency and total pressure loss decrease with the increase of b1;The fan-type lobed mixer with smaller b2has a better effect on promoting the combustion efficiency in the region near the ATR combustor center line than that with a pair of parallel side walls.The total pressure recovery coefficient reaches more than 0.99 at the exit of combustor in nonreactive combustion while the total pressure loss reaches more than 4%in the reacting combustion.Compared with the mixing process,more than80%of the total pressure loss is caused during combustion.展开更多
To the problem of the unknown underwater target detection, according to the feature that the underwater target radiated noise contains the stable line spectrum, a weighted method based on the main-to-side lobe ratio ...To the problem of the unknown underwater target detection, according to the feature that the underwater target radiated noise contains the stable line spectrum, a weighted method based on the main-to-side lobe ratio （MSLR） is proposed for broadband beam-forming. This weighted method can be implemented by using the following steps. Firstly, optimize the spatial spectrum of each frequency unit by the second-order cone programming （SOCP）, and obtain the optimized spatial spectrum with lower side lobe. Secondly, construct weighting factors based on the MSLR of the optimized spatial spectrums to from weight factors. Lastly, cumulate the spatial spectrum of each frequency unit via the weight statistical method of this paper. This method can restrain the disturbance of background noise, enhance the output signal-to-noise ratio （SNR）, and overcome the difficulty of traditional four-dimensional display. The theoretical analysis and simulation results both verify that this method can well enhance the spatial spectrum of line spectrum units, restrain the spatial spectrum of background noise units, and improve the performance of the broadband beam-forming.展开更多
Window based Finite Impulse Response filters have the problem that in order to obtain better performance from these filters in terms of minimum stopband attenuation cost has to be paid for half main-lobe width and vic...Window based Finite Impulse Response filters have the problem that in order to obtain better performance from these filters in terms of minimum stopband attenuation cost has to be paid for half main-lobe width and vice-versa. A solution of this contradictory behavior is to increase the length of the window which in turn requires more hardware hence increasing the cost of system. This paper proposes a novel window based on two shifted hyperbolic tangent functions. The proposed window contains an adjustable parameter, with the help of which desired time and frequency domain characteristics may be achieved for relatively shorter window length. The characteristics of the proposed window are compared with those of the two well-known adjustable windows namely Cosh window and Exponential window. MATLAB simulation results show that for the same value of window length, the proposed window provides improved output, and thus it makes a good compromise between minimum stopband attenuation and half main-lobe width compared to the windows mentioned previously.展开更多
基金supported by the National Science and Technology Major Project(No.J2019-Ⅲ-0001-0044)。
文摘The air-turbo-rocket(ATR)engine is a promising propulsion plant for achieving numerous surface and air launched missile missions.The application of lobed mixer in the ATR combustor can promote the mixing of the fuelrich gas and the air,thus improving the engine performance significantly.The numerical simulation method was conducted to explore the effects of lobe peak-to-trough width ratio on mixing and combustion performance in ATR combustors.Results show that:For a given peak lobe width b1,the combustion efficiency and total pressure loss decrease with the increase of trough lobe width b2;For a given b2,the combustion efficiency and total pressure loss decrease with the increase of b1;The fan-type lobed mixer with smaller b2has a better effect on promoting the combustion efficiency in the region near the ATR combustor center line than that with a pair of parallel side walls.The total pressure recovery coefficient reaches more than 0.99 at the exit of combustor in nonreactive combustion while the total pressure loss reaches more than 4%in the reacting combustion.Compared with the mixing process,more than80%of the total pressure loss is caused during combustion.
基金supported by the National Natural Science Foundation of China(Grant No.61372180)the National Key Scientific Instrument Equipment Development Project of China(Grant No.2013YQ140431)
文摘To the problem of the unknown underwater target detection, according to the feature that the underwater target radiated noise contains the stable line spectrum, a weighted method based on the main-to-side lobe ratio （MSLR） is proposed for broadband beam-forming. This weighted method can be implemented by using the following steps. Firstly, optimize the spatial spectrum of each frequency unit by the second-order cone programming （SOCP）, and obtain the optimized spatial spectrum with lower side lobe. Secondly, construct weighting factors based on the MSLR of the optimized spatial spectrums to from weight factors. Lastly, cumulate the spatial spectrum of each frequency unit via the weight statistical method of this paper. This method can restrain the disturbance of background noise, enhance the output signal-to-noise ratio （SNR）, and overcome the difficulty of traditional four-dimensional display. The theoretical analysis and simulation results both verify that this method can well enhance the spatial spectrum of line spectrum units, restrain the spatial spectrum of background noise units, and improve the performance of the broadband beam-forming.
文摘Window based Finite Impulse Response filters have the problem that in order to obtain better performance from these filters in terms of minimum stopband attenuation cost has to be paid for half main-lobe width and vice-versa. A solution of this contradictory behavior is to increase the length of the window which in turn requires more hardware hence increasing the cost of system. This paper proposes a novel window based on two shifted hyperbolic tangent functions. The proposed window contains an adjustable parameter, with the help of which desired time and frequency domain characteristics may be achieved for relatively shorter window length. The characteristics of the proposed window are compared with those of the two well-known adjustable windows namely Cosh window and Exponential window. MATLAB simulation results show that for the same value of window length, the proposed window provides improved output, and thus it makes a good compromise between minimum stopband attenuation and half main-lobe width compared to the windows mentioned previously.
