US 12,360,083 B1
Method and system for measuring burning rate of propellant based on multi-channel ultrasonic waves
Juan Cui, Shanxi (CN); Yongqiu Zheng, Shanxi (CN); Xiaolong Yan, Shanxi (CN); Wenlong Wei, Shanxi (CN); and Ruizhi Wang, Shanxi (CN)
Assigned to North University of China, Taiyuan (CN)
Filed by North University of China, Shanxi (CN)
Filed on Jan. 8, 2025, as Appl. No. 19/014,175.
Claims priority of application No. 202410757289.5 (CN), filed on Jun. 13, 2024.
Int. Cl. G01N 29/14 (2006.01); G01N 33/22 (2006.01)
CPC G01N 29/14 (2013.01) [G01N 33/22 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A method for measuring the burning rate of a propellant based on multi-channel ultrasonic waves, comprising the following steps:
step 1: opening a noise collection channel and an ultrasonic channel, and transmitting ultrasonic waves to a solid propellant in an engine outer shell via a plurality of ultrasonic transducers arranged on the same circumference of the engine outer shell;
step 2: collecting echo signals and corresponding noise signals of each ultrasonic channel, and pre-processing the echo signals;
step 3: calculating a range of first echo time t3 based on acoustic properties of material being tested;
step 4: acquiring first frame of data, finding two adjacent echoes with the maximum amplitude difference in a current frame and the maximum wave peak of an echo period of the current frame, and calculating a threshold coefficient; a calculation formula of the threshold coefficient A in step 4 being as follows:

OG Complex Work Unit Math
where AMAX represents the maximum wave peak value in the echo period of the current frame, and Ax and Ax+1 respectively represent amplitudes of the two adjacent echoes with the maximum amplitude difference;
step 5: traversing a wavelet basis set to screen an optimal wavelet basis, performing wavelet packet decomposition on echo data of the current frame via the screened optimal wavelet basis, performing denoising processing and signal reconstruction on wavelet packet decomposition signals via a standard deviation of the noise signal collected in step 2, and performing time-frequency analysis on reconstructed signals to obtain a time range of a waveform appearing corresponding to an echo frequency as a range of a second echo time tn; in step 5, a method for screening the optimal wavelet basis being as follows: traversing a set of wavelet basis functions {ω1, ω2 . . . ωi . . . , ωn}, where ω1, ω2 . . . ωi . . . ωn, represent the 1st, 2nd, . . . ith . . . , and nth wavelet bases respectively, calculating an energy concentration degree factor C corresponding to each wavelet basis function, and selecting a wavelet basis function with a value of the energy concentration degree factor C closest to 1 as the optimal wavelet basis, a calculation formula being as follows:

OG Complex Work Unit Math
where MAX/ω[n]2/ represents a square of the maximum amplitude of the nth wavelet basis, and E represents a total energy of the wavelet basis; and
in step 5, when performing denoising processing, a fixed multiple of the standard deviation of the noise signal being selected as a wavelet threshold to perform denoising processing on the wavelet packet decomposition signals;
step 6: determining a range of a final echo time tx according to ranges of the first echo time t3 and the second echo time tn, a range of the final echo time tx being txϵt3∩tn;
step 7: performing time difference extraction within the range of the final echo time tx, and determining a dynamic threshold of the current frame according to the threshold coefficient obtained in step 4, and obtaining an echo moment of the current frame according to the dynamic threshold of the current frame;
step 8: acquiring next frame of data, and repeating the above-mentioned steps 5-7 to obtain an echo moment corresponding to each frame of data; and
step 9: repeating the above-mentioned steps 3-8 for echo data and noise data of each channel to obtain an echo moment corresponding to each frame of data in each channel; and calculating a burning rate according to the echo moment corresponding to each frame of data in each channel.