便携式深纹核桃采果装置气动调频激振器设计与试验

Design and Experiment on Pneumatic Frequency-modulated Vibrator for Portable Deep-grained Walnut Harvesting Device

摘要:

针对现有气动激振器激振频率较高且不可调节，难于应用于便携式深纹核桃采果装置的问题，本文设计了便携式深纹核桃采果装置气动调频激振器，确定了其关键设计参数。基于气体动力学和牛顿第二定律，建立了激振气流及激振活塞运动理论模型。通过激振气压分布、激振力特性及激振频率特性分析和激振试验，证实了便携式深纹核桃采果装置气动调频激振器激振性能。研究结果表明，气动调频激振器最大激振力与气动流量和回程气阻孔径相关，气动流量越大则激振力越大，增大回程气阻孔径可缩短激振活塞回程时间，但会降低最大激振力。气动调频激振器激振频率取决于激振与活塞回程时间、气动供气间隔时间，缩短气动供气间隔时间和增大回程气阻孔径可提高激振频率。对于活塞直径为50 mm与回程气阻孔径1.5 mm的气动调频激振器，激振频率可调范围为2~15 Hz，当气动流量为7.03×10^-3、6.13×10^-3、5.62×10^-3、4.22×10^-3、2.61×10^-3 kg/s时，最大激振力计算值为240.8、212.1、193.4、170.3、126.9 N，最大激振力仿真值为249.3、222.2、204.7、183.2、145.5 N，最大激振力测试值为(243.7±23.7) N、(219.7±14.3) N、(202.1±15.9) N、(180.5±20.8) N和(140.2±37.0) N。

Abstract:

Aiming to address the issue that existing pneumatic vibrators have high, non-adjustable excitation frequencies, which makes them difficult to apply to portable, deep-groove walnut harvesting devices. It presented the design of a frequency-adjustable pneumatic exciter for a harvester, determining its key design parameters in the process. Theoretical models of the excitation airflow and the motion of the excitation piston were developed by using gas dynamics and Newton's second law. Excitation experiments and analysis of the air pressure distribution, force, and frequency characteristics verified the exciter's performance. The research results showed that the maximum excitation force of the pneumatic frequency-modulated exciter depended on the pneumatic flow rate and the diameter of the air resistance orifice during the return-stroke. A higher pneumatic flow rate resulted in a greater excitation force. Conversely, increasing the diameter of the return-stroke air resistance orifice reduced the maximum excitation force, but shortened the return-stroke time of the excitation piston. The exciter's excitation frequency depended on the excitation and piston return times, as well as the pneumatic supply interval. Shortening the supply interval and increasing the orifice diameter can increase the frequency. For a pneumatic frequency-controlled exciter with a piston diameter of 50 mm and return-stroke orifice diameters of 1.5 mm, the adjustable frequency range was 2~15 Hz. When the pneumatic flow rates were 7.03×10^-3 kg/s, 6.13×10^-3 kg/s, 5.62×10^-3 kg/s, 4.22×10^-3 kg/s and 2.61×10^-3 kg/s, respectively, the calculated maximum excitation forces were 240.8 N, 212.1 N, 193.4 N, 170.3 N and 126.9 N, respectively. The corresponding simulated values were 249.3 N, 222.2 N, 204.7 N, 183.2 N and 145.5 N, respectively. The measured values were (243.7±23.7) N, (219.7±14.3) N, (202.1±15.9) N, (180.5±20.8) N and (140.2±37.0) N, respectively.