| The occurrence of livestock diseases is usually caused by viruses and bacteria.Immunization as the most important part of poultry epidemic prevention,can be achieved to eliminate the source of infection,cut off the transmission and protect susceptible animals.In poultry epidemic prevention work,subcutaneous injection can be directly to the body,and has the characteristics of maintaining the stability of the drug.However,there is a risk of cross-infection and accidental injury in the hand-held syringes.The existing needleless syringes can overcome the above problems,generally with compression springs,high pressure gas,laser and voice coil as the power source.There are some disadvantages for them that the driving force is difficult to adjust and the pressure requirement is very high.Piezoelectric needleless syringes are small in size,precise in control,but with low injection dose.To this end,this paper proposes a micro-displacement amplifier and an ultrasonic concentrator as a power source for a needleless syringe,and a nozzle structure for the piezoelectric needleless syringe.The main contents of this paper are as follows:（1）By studying the injection mechanism of the needleless syringe,the process of penetrating the skin is analogous to the high pressure free jet cutting process,and the key parameters of the high pressure free jet are extracted.Finally,the piezoelectric needleless syringe model is built based on the continuity equation of the hydrodynamics.（2）The static displacement of micro-displacement amplifier is simulated by finite element software,and the output displacement and output force of micro-displacement amplifier are obtained.At the same time,the sensitivity of structural parameters is analyzed,and six structural parameters are selected to design variables.According to the requirements of output displacement and output force,the micro-displacement amplifier is optimized.The results show that when the peak-to-peak value of DC excitation voltage is 200V,the micro displacement mechanism can produce the output displacement in the Z axis direction of 1.35′10-5m and the output force is 0.78N,which is 38.2%and 110.8%higher than that before optimization.（3）Based on the requirements of ampoule cleaning,the ultrasonic concentrator is designed by ultrasonic cavitation,and its resonant frequency is 25094Hz in the longitudinal mode by means of finite element software.The error with the calculated frequency is less than 1%,indicating that the established finite element model is highly reliable.Finally,the harmonic response analysis is carried out.The numerical simulation results show that it resonates with the sinusoidal alternating voltage of 160V,and the maximum vibration velocity is 119.87m/s and the maximum amplitude is 7.6′10-4m.（4）The fluent software is used to simulate the high pressure free jet of four kinds of nozzles.The results show that the nozzle with cone-shaped structure can obtain symmetrical jet with good controllability.Using the SPSS software to analyze the simulation results,it is found that the length of the central cylinder has a significant effect on the average jet velocity and turbulence intensity of the nozzle.The cone-shaped shrinkage angle has no significant effect on the average injection velocity of the nozzle,but has a significant effect on the average turbulence intensity.The interaction between the length of the cylinder and the conical shrinkage angle has no significant effect on the average injection velocity and the average turbulence intensity of the nozzle.Considering that the conical shrinkage angle is 30°and the length of the intermediate cylinder is 0.2mm,the cone-shaped nozzle can get the best jet characteristics.The average speed of the outlet can reach 6.56m/s and the turbulence intensity is 1.04%.（5）The output characteristics of micro-displacement amplifiers and ultrasonic concentrator prototypes at different drive voltages are studied.Through the construction of the relevant experimental platform,they were applied to drive voltage signal,respectively,to measure the output and output displacement.The results show that the maximum output force of the micro-displacement amplifier is 0.84N and the maximum output displacement is 1.5′10-5m under the DC voltage of 200V.The ultrasonic output device in the excitation frequency of 24.73kHz under the alternating voltage,can produce the maximum output displacement of 7.3′10-4m.（6）According to the test results,if the micro-displacement enlarging mechanism drives the piston,the liquid is ejected from the cone-shaped nozzle.The maximum injection dose is 5.77μL,the maximum injection pressure is 1446.84Pa and the maximum outlet injection rate is 8.8 m/s,driven by the DC voltage of 200V without considering friction and pipe pressure loss. |
PDF Full Text Request