Effects of Vibration Characteristics on the Atomization Performance in the Medical Piezoelectric Atomization Device Induced by Intra-Hole Fluctuation

Oral inhalation of aerosolized drugs has be widely applied in healing the affected body organs including lesions of the throat and lungs and it is more efficient than those conventional therapies, such as intravenous drip, intramuscular injection and external topical administration in the aspects of the dosage reduction and side effects of drugs. Nevertheless, the traditional atomization devices always exhibit many drawbacks. For example, non-uniformed atomization particle distribution, the instability of transient atomization quantity and difficulties in precise energy control would seriously restrict an extensive use of atomization inhalation therapy. In this study, the principle of intra-hole fluctuation phenomenon occurred in the hole is fully explained, and the produced volume change is also estimated. Additionally, the mathematical expression of the atomization rate of the atomizing device is well established. The mechanism of the micro-pump is further clarified, and the influence of the vibration characteristics of the atomizing film on the atomization behavior is analyzed theoretically. The curves of sweep frequency against the velocity and amplitude of the piezoelectric vibrator are obtained by the Doppler laser vibrometer, and the corresponding mode shapes of the resonance point are achieved. The influence of vibration characteristics on atomization rate, atomization height and atomization particle size are also verified by experiments, respectively. Both the experimental results and theoretical calculation are expected to provide a guidance for the design of this kind of atomization device in the future.

Investigation of effect of atomization performance on lean blowout limit for gas turbine combustors by comparison of utilizing aviation kerosene and methane as fuel

The lean blowout (LBO) limit is crucial for gas turbine combustor in the aero engine. The effect of atomization of liquid fuels on the LBO limit is needed to be further studied. On the other hand, the effects of atomization on the LBO limit can be neglected if gas fuels are utilized in a combustor. Thus, the comparative experiment between liquid fuel and gas fuel can be utilized to study the effects of atomization performance of liquid fuels on the LBO limit. In this paper, the LBO limit for a gas turbine combustor utilizing methane is studied experimentally. Seven kinds of combustor configurations are chosen for the experimental test. The LBO limits are obtained for all the chosen combustors. The variation of the LBO limit with the combustor configuration for both methane and aviation kerosene exhibits the similar tendency, i.e., the LBO limits utilizing methane are slightly larger than those utilizing aviation kerosene for the same combustor. Further, the atomization performance has little effects on the LBO limits for the present combustor configurations at the present operating conditions where the SMD for the fuel atomizer utilizing aviation kerosene is about 10 μm.

Numerical Study on Combustion and Atomization Characteristics of Coaxial Injectors for LOX/Methane Engine

The LOX/methane engine has an admirable performance under a supercritical state. However, the properties of methane change drastically with varying injection temperature. Because the injector can greatly affect the atomization and combustion, this study performed a three-dimensional numerical simulation of atomization, combustion, and heat transfer in a subscale LOX/methane engine to evaluate the effect of the main fluid parameters with different methane injection temperatures and different injectors on atomization performance and combustion performance. The results show that the larger propellant momentum ratio and Weber number can improve the heat flux and combustion stability in shear coaxial injector, while the influence in swirl coaxial injector is relatively small. Moreover, in shear coaxial injector and in swirl coaxial injector, the larger propellant momentum ratio and Weber number can reduce the droplet size, enhance atomization performance, and improve the combustion efficiency. The numerical model provides an economical method to evaluate the main fluid parameters and proposes new design principles of injectors in LOX/methane engine.

Mathematical Model of SMD of Hydrodynamic Ultrasonic Atomizing Nozzle Based on Orthogonal Design

The hydrodynamic ultrasonic atomization nozzle has excellent atomization performance and has a wide range of applications in the field of spray dust reduction. A mathematical model the SMD of the nozzle was established to evaluate the SMD of such nozzles using the custom-designed spraying experiment platform and orthogonal design methods. The interaction between the SMD of the nozzle and the three influencing factors, i.e., air pressure, water pressure and outlet diameter were obtained. Through range analysis, the primary and secondary order of the three parameters affecting SMD of the nozzle is: air pressure > water pressure > outlet diameter. On this basis, a mathematical model was constructed using a multivariate nonlinear regression method to estimate the SMD of the nozzle. The predicted values of the SMD of the nozzle by the multivariate nonlinear regression mathematical model were basically consistent with the experimental results, with an average relative error of only about 5%. Thus the established mathematical model in this paper can be used to predict and calculate the droplet size for hydrodynamic ultrasonic atomizing nozzles.

Reducing Spray Drift and Increasing Spreading Effect of the Thifluzamide Through the Use of Adjuvants and Nozzles

Spray drift, as a practical issue during Unmanned Aerial Vehicle (UAV) spraying, has a negative impact on the environment, and the use of air-induction nozzles or anti-drift adjuvants are the most common recommendations for reducing drift. To screen the adjuvants for favourable atomization performance and anti-drift effect, we evaluated the spray atomization performance of different adjuvants by the droplet size measurement system. From the wind tunnel results, we commented on the relationship among the atomization performance, drift distance and drift deposition, and determined the drift percentage of different nozzles and the surface tension of liquids with different adjuvants. The results showed that the addition of adjuvants would modify the distribution span S, ΦVol<150μm and the volume medium diameter D50; ΦVol<150μm and D50 of the Maifei treatment decreased and increased the most of all the treatments. There were negative correlations between the drift distance, D50 and percentage of drift amount. The adjuvants Maifei and the nozzle IDK120-015 significantly decreased the drift deposition amount. And the anti-drift effect of nozzle IDK120-015 plus Maifei was significantly stronger than that of other nozzles or adjuvants. In addition, the addition of adjuvants could significantly decrease the surface tension, especially for Maifei. These results suggest that the addition of Maifei is an effective way to reduce the spray drift for all nozzle types and lessen the surface tension. These data help to provide a theoretical basis for selecting suitable nozzles and adjuvants for plant protection UAVs.

Preparation and application of a thidiazuron·diuron ultra-low-volume spray suitable for plant protection unmanned aerial vehicles

Spraying of defoliant can promote centralized defoliation of cotton and advance maturity to facilitate harvesting. Modern pesticide application equipment includes plant protection unmanned aerial vehicles (UAVs), which are used widely for spraying defoliants. However, commonly used defoliant formulations are mainly suspension concentrates and water-dispersible granules, which need to be diluted with water when used. These are not suitable for plant protection UAVs with limited load capacity, especially in arid areas such as Xinjiang, China. Therefore, we prepared a thidiazuron·diuron ultra-low-volume (ULV) spray, which can be used directly without dilution in water. We found that ULV sprays had better wettability than the commercially available suspension concentrate, could quickly wet cotton leaves and spread fully. The volatilization rate was lower. ULV sprays also showed better atomization performance and more uniform droplet distribution than the commercially available suspension concentrate. At a dosage of 4.50–9.00 L/ha, the coverage rate on cotton leaves was 0.85–4.15% and droplet deposition densities were 15.63–42.57 pcs/cm2; defoliation rate and spitting rate were also greater than those of the reference product. This study could be contributed to the development of special pesticide formulations suitable for UAVs.