Experimental Study on Acoustic Property of Solid Rocket Motor under Pulse Triggering

doi:10.12382/bgxb.2024.0162

Abstract

Abstract:

In order to study the influence of external excitation on the stability of solid rocket motor,an experimental model system for the acoustic property of solid rocket motor is built,and the axial and radial excitation experiments of solid rocket motor are carried out.The influences of throttle aperture and trigger mode on the experimental results are studied.The natural frequency and attenuation coefficient of each order oscillation are obtained.The acoustic speed in the combustion chamber measured by cross-correlation analysis is 604.2m/s,and the frequency error predicated upon the measured acoustic speed is 10.1%.The oscillation of the system can be divided into two stages according to the attenuation speed.When the throttling aperture increases,the frequency of pressure oscillation input into the motor by a pulser and the oscillation amplitude of each mode increase,and the first-stage attenuation becomes faster,while the second-stage attenuation becomes slower.The oscillation attenuation of the axial excitation is faster than that of the radial excitation on the combustion chamber head in the first stage,and it has stronger nonlinear characteristics.

Key words: solid rocket motor, natural frequency, attenuation coefficient, pulse triggering, cross-correlation analysis

CLC Number:

TJ301

ZENG Jiajin, LI Junwei, LI Qiang, LI Tao, ZHANG Wenhao, LU Jiancheng, WANG Ningfei. Experimental Study on Acoustic Property of Solid Rocket Motor under Pulse Triggering[J]. Acta Armamentarii, 2025, 46(2): 240162-.

Figures/Tables 21

Fig.1 Experimental setup of radial excitation of solid rocket motor

Fig.2 Assembly drawing of motor and pulser (Unit:mm)

Fig.3 Pulse trigger

Fig.4 Physical diagram of trigger excitation experimental system

Table 1 Test cases

工况	激励方式	药量/g	孔径/mm	脉冲器压力/MPa
1	径向	5	5	52.0
2	轴向	5	6	53.0
3	轴向	5	6	51.6
4	轴向	5	4	51.0

Fig.5 Comparison of pressure signals at measuring points P1~P4

Fig.6 Cross-correlation analysis of measuring points P3 and P4 under radial excitation

Fig.7 Frequency characteristics of acoustic cavity in solid rocket motor

Table 2 The mode frequency of oscillation in the motor

模态	测点P₃		测点P₄
模态	频率/Hz	PSD	频率/Hz	PSD
1	475	0.0240	487	0.02620
2	962	0.0100	937	0.01140
3	1462	0.0062	1462	0.01190
4	1950	0.0058	1975	0.00690
5	2450	0.0051	2387	0.00338
6	2925	0.0038

Fig.8 Simulated results of the first-order eigenfrequency

Fig.9 Oscillation signals and attenuation coefficients at combustion chamber head and nozzle inlet

Fig.10 Modal attenuation curves of all orders and their fitting

Fig.11 Attenuation coefficient and oscillation amplitude of each mode in radial excitation experiment

Fig.12 Time-frequency curves at measuring point 2 under different throttling apertures

Fig.13 Pressure oscillation curve in axial excitation experiment

Fig.14 Comparison of power spectral densities

Fig.15 Attenuation coefficient and oscillation amplitude of each order in the axial excitation experiment

Table 3 The ratio of attenuation coefficient to attenuation amplitude in the first stage

测点	工况	触发方向	孔径/mm	p'_max/MPa	α₁/(s^-1)	R₁	Δp'/%	Δt/ms
P₃	2	轴向	6	1.21	-379.37	0.9914	79.00	4.10
	1	径向	5	0.81	-270.26	0.9955	67.26	4.13
	4	轴向	4	0.30	-323.16	0.9781	72.60	4
P₄	2	轴向	6	1.73	-631.67	0.9851	89.01	3.53
	1	径向	5	1.07	-442.28	0.9624	80.16	3.54
	4	轴向	4	0.42	-430.96	0.982	78.00	3.45

Table 4 The ratio of attenuation coefficient to attenuation amplitude in the second stage

测点	工况	触发方向	孔径/mm	α₂/(s^-1)	R₂	Δp'/%	Δt/ms
P₃	2	轴向	6	-58.6	0.9760	92.77	36.66
	1	径向	5	-66.43	0.9950	91.90	36.80
	4	轴向	4	-78.51	0.9790	92.10	36.30
P₄	2	轴向	6	-59.50	0.9703	90.41	36.88
	1	径向	5	-67.43	0.9968	91.91	36.96
	4	轴向	4	-73.09	0.9813	88.42	36.50

Fig.16 Relationship between maximum pressure oscillation amplitude and throttle aperture

Fig.17 Relationship between attenuation coefficient and throttle aperture

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