Abstract
Double-cavity shock absorber with high-pressure piston is the core component of the nose landing gear of the carrier-based aircraft, and its fast-extension performance seriously affects the safety of the catapult-assisted takeoff. The design of a carrier-based aircraft in our country is carried out based on the traditional method of fast-extension dynamics, and it is found that the fast-extension capability is larger than designed. This paper analyzes the working principle of the high-pressure piston shock absorber and explains that the high-pressure air cavity pushes the piston rod to extend rapidly, which will cause the cavitation phenomenon in the main oil chamber. Thus, the cavitation in the main oil chamber makes the traditional modeling method of oil-liquid resistance force no longer applicable. Then, the axial force modeling method of shock absorber considering the cavitation effect is proposed. Based on the carrier-based aircraft, the dynamic response of the shock absorber in the process of fast extension is calculated and then it is compared with the calculation results of the traditional dynamic method. It is found that due to the cavitation effect caused by the forced fast extension section of the high-pressure air plug shock absorber, the fast extension work increases by 67.6%, thus, revealing the fast extension mechanism of the double-chamber shock absorber with high-pressure piston and successfully explaining the phenomenon of the fast extension ability exceeding the expectation of the shock absorber.
Highlights
The shock absorber is the key component of the aircraft landing gear
Shin [8] used Adams to establish the dynamic model of single cavity shock absorber landing gear with cavitation effect, which proved that the simulation results were more consistent with the experimental results when the cavitation effect was taken into consideration
Based on the study of the working condition of each cavity of the high-pressure piston shock absorber, it is found that the negative pressure appears in the main oil chamber of the shock absorber during the fast extension process, resulting in the cavitation phenomenon, which leads to the invalidity of some assumptions in the modeling method of force elements such as oil resistance force in the traditional method of fast extension dynamics
Summary
The shock absorber is the key component of the aircraft landing gear. For catapult carrier-based aircraft [1], the shock absorber should meet the landing shock absorber requirements of carrier-based aircraft and the catapult fast-extension performance. Based on the study of the working condition of each cavity of the high-pressure piston shock absorber, it is found that the negative pressure appears in the main oil chamber of the shock absorber during the fast extension process, resulting in the cavitation phenomenon, which leads to the invalidity of some assumptions in the modeling method of force elements such as oil resistance force in the traditional method of fast extension dynamics. The compressed gas in the gas chamber of the conventional shock absorber (Figure 2(b)) compresses the oil in the gas chamber downward, and the oil flows to the main oil chamber through the main oil hole, squeezing the end face of the piston rod, so as to push the piston rod to extend outwards In this process, the oil in the shock absorber remains squeezed, and there will be no negative pressure and cavitation. A negative pressure appears when the pressure of the main chamber drops, which causes the dissolved gas in the oil to expand and form cavitation
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