Response Surface Methodology (RSM) Approach for Optimizing the Actuator Nozzle Design of Pressurized Metered-Dose Inhaler (pMDI)

Recently, a remarkable scientific interest in the inhalation therapy for respiratory disease was spiked attributed to the growing prevalence of asthma, chronic obstructive pulmonary disease (COPD), and coronavirus disease 2019 (COVID-19) pandemic. A pressurized metered-dose inhaler (pMDI) is the best option by providing fast and efficient symptomatic relief within the lung. However, the rapid development of new inhalation devices could be critical in this competitive environment, and optimizing the inhalation devices could be costly and time-consuming. Therefore, the computational fluid dynamic (CFD) approach was used to shorten the development time. In this study, response surface methodology (RSM) in ANSYS version 19.2 was introduced to discover the optimal design for the actuator nozzle to increase the performance of pMDI. Three (3) parameters (orifice diameter, length, and actuator angle) were optimized, and the best design was selected according to the analysis of particle tracking. The analysis of spray plume was also conducted and compared to analyze the spray plume characteristic produced by three designs. The result showed that RSM generated three (3) models for the new design of the actuator nozzle (Design A, Design B, and Design C). Among three (3) designs, actuator nozzle design C showed the highest injection particle number (232457) and the only one that produced maximum particles velocity magnitude in the acceptable ranges (35.67m/s). All three designs showed a similar pattern as maximum particle velocity magnitude decreased along the axial length until they match the air velocity (0.03-0.04 m/s). Furthermore, the spray plume length, angle, and width were observed to increase linearly with the decreasing maximum particle velocity magnitude. Thus, this study suggested that design C might have the potential as a new actuator nozzle to develop future pMDI to relieve the respiratory condition.

Unveiling the Flow Behavior Inside GDI Engine Cylinder Using High-Speed Time-Resolved Particle Image Velocimetry and CFD Simulation

RICARDO-VECTIS CFD simulation of the in-cylinder air flow was first validated with those of the experimental results from high-speed particle image velocimetry (PIV) measurements taking cognisant of the mid-cylinder tumble plane. Furthermore, high-speed fuel spray measurements were carried out simultaneously with the intake-generated tumble motion at high valve lift using high-speed time-resolved PIV to chronicle the spatial and time-based development of air/fuel mixture. The effect of injection pressure(32.5 and 35.0 MPa) and pressure variation across the air intake valves(150, 300 and 450 mmH2O) on the interaction process were investigated at valve lift 10 mm where the tumble vortex was fully developed and filled the whole cylinder under steady-state conditions. The PIV results illustrated that the intake generated-tumble motion had a substantial impact on the fuel spray distortion and dispersion inside the cylinder. During the onset of the injection process the tumble motion diverted the spray plume slightly towards the exhaust side before it followed completely the tumble vortex. The fuel spray plume required 7.2 ms, 6.2 ms and 5.9 ms to totally follow the in-cylinder air motion for pressure differences 150, 300 and 450 mmH2O, respectively. Despite, the spray momentum was the same for the same injection pressure, the magnitude of kinetic energy was different for different cases of pressure differences and subsequently the in-cylinder motion strength.

Computational fluid dynamic simulation of a pulse-width modulated spray nozzle

Computational fluid dynamics (CFD) is a useful tool used by engineers in many industries to study fluid flow. A relatively new industry to adopt the use of CFD is the agricultural industry. A spray nozzle commonly used in agricultural spraying, the Teejet 110-degree nozzle (TeeJet Technologies, 2020), was simulated. A method was developed to pulse the spray. A user-defined function was used to define the velocity at the inlet of the nozzle to pulse the spray. The domain was then extended to allow the examination of a slice 20 inches below the nozzle. The simulation results were compared to experimental results collected from a sprayer testbed. The effect of frequency was then investigated by changing the frequency of the pulses. Results from these studies show that a userdefined function can be used to pulse the spray. CFD can be used to model spray nozzles, but the validity of the results are strongly related to the computational resources available, and increasing the frequency of the pulses results in a higher concentrated spray toward the center of the spray plume. The simulations were carried out using a commercial code (CD-Adapco, 2019).

Coupled in-nozzle flow and spray simulation of Engine Combustion Network Spray-G injector

A coupled Eulerian-Lagrangian approach was employed to Engine Combustion Network (ECN) Spray-G simulations. The Eulerian in-nozzle flow simulation was conducted with a small plenum attached to the nozzles, and the results were fed to the Lagrangian spray simulation. For Eulerian simulation, the homogeneous relaxation model (HRM) coupled with the volume of fluid (VOF) method was used. HRM proved to be good at predicting the phase change phenomena due to vaporization mechanisms, that is, both cavitation and flash boiling. As a one-way coupling, quantities such as rate of injection (ROI), mass injected through each hole, discharge coefficient, spray plume angle and half cone angle predicted from the Eulerian simulations were used as the initial and boundary conditions for the subsequent Lagrangian spray simulations using the blob injection model. Non-flashing (Spray-G1) and flashing (Spray-G2) spray was simulated, and the results were validated quantitatively against the published data in terms of the liquid and vapor penetration lengths, and good agreements were obtained. Furthermore, the simulation predicted the liquid and gas axial velocity and sauter mean diameter for Spray-G1 condition in agreement with the droplet size and particle image velocimetry (PIV) measurements from literature.

Calculation of the radius of the cutting torch when drying liquid heterogeneous systems with complex rheological properties

The value of the radius of the spray torch at different heat-technological parameters of drying and the necessary information for the analysis and optimization of the operation of the spray drying unit, depending on the productivity, its technical characteristics and the physicochemical characteristics of the material being dried, can be quickly obtained using a mathematical calculation algorithm. The calculations were carried out in Microsoft Excel according to the formula of Acad. A.A. Dolinskyi, in which the value of the average volumetric-surface diameter of a droplet in the spray plume is determined by the Fraser formula. The results of calculating the radius of the spray plume are presented on the example of a mushroom suspension, which is characterized by complex rheological properties, obtained using a special technology of the Institute of Technical Thermophysics of the National Academy of Sciences of Ukraine. The calculations were carried out for a small-sized spray dryer with a cylindrical part of the chamber 1.3 m in diameter and a disk atomizer at different parameters: air temperature at the chamber inlet, the unit's capacity for liquid product and its temperature. The dependences obtained from the calculated data demonstrate the possibility of reducing the radius of the spray of a liquid heterogeneous system with a temperature of 50-60 ° C by an average of 20% in comparison with the cooled product, and with an increase in the temperature of the coolant at the inlet to the chamber from 160 ° C to 190 ° C, the productivity of the spray drying unit increases by 25-30%. The high convergence of the calculated data with the experimental ones indicates the advisability of using this mathematical calculation algorithm for a quick and well-grounded determination of the rational dimensions of industrial spray dryers for the production of dry forms of new types of products, taking into account the complex rheological properties of the initial high-humidity heterogeneous systems and the peculiarities of the kinetics of their drying.

Effects of Valve Strokes on Spray Shapes for GDI Injector

The effects of valve strokes on the spray shapes of a GDI injector with six holes were studied. Two kinds of strokes that change the shapes to be either cone-shaped or bell-shaped were selected to investigate the flow characteristics that caused the shapes to change. Fuel-spray behaviors were first observed with an experimental setup; strokes of 100 percent (full stroke) and 26 percent were selected assuming the multiple injection of fuel. The 26 percent stoke was selected as a representative example of narrow stroke. To investigate the flow characteristics that caused the cone and bell shapes, computational fluid simulation was applied to study the fluid flows around the holes and sprays in the air region. It was found that the stroke of 26 percent formed a narrow space upstream of the hole inlets, so the velocity component in the radial direction at the hole inlets increased. The velocity component in the radial direction also increased at the hole outlets, so each spray plume became wider and the spaces between the plumes narrower. Due to the narrower spaces, the mixture of the plumes caused the spray to become bell-shaped. The velocity component in the radial direction at the hole outlets was an important factor that determined the spray shape in the air region.