Fertigation control system based on the mariotte siphon

This paper adopts the Mariotte siphon to simplify the nutrient solution preparation structure while improving the liquid mixing accuracy for nutrient solution. A liquid mixing model suitable for EC and pH regulation was constructed by combining fuzzy control algorithms, and a set of fertigation nutrient solution control equipment was designed and developed. During the experiment, comparison was made between the Fuzzy-PID algorithm and the traditional PID algorithm in terms of nutrient solution configuration. The results show that the Fuzzy-PID algorithm is smoother and more stable compared to the PID algorithm. Through analysis of the liquid mixing accuracy with the venturi type fertigation machine, it was found that the fertigation machine designed with the Mariotte structure is more accurate for liquid mixing, and can better meet the needs of crop growth.

Optimization of Flow and Mixing in a Venturi Tube Mixer with a Two-Step Method Using Numerical Simulation

To achieve efficient mixing in a Venturi tube mixer (VTM), an optimization with a two-step method for this mixing device based on a Venturi tube (VT) was carried out using numerical simulation. Firstly, the effects of the structural parameters on the flow in VT were revealed, and the optimized configuration was determined for the following VTM. Subsequently, by introducing a jetting tube, the suction capacity, energy consumption and mixing quality were used to evaluate the performance of VTM under various configurations and operating conditions. According to the effects of the structural parameters on the mixing quality of VTM, an empirical formula for mixing quality with structural parameters was proposed. Finally, an optimized VTM was proposed. This work can provide a valid suggestion for the design and optimization of such a mixing device.

Flow of Oil and Water through the Nozzle and Cavitation

Today, the correct understanding of the issue of oil and water cavitation is important due to the growing demands on working conditions in hydraulic systems (pressure and flow rate). This article deals with the measurement and subsequent mathematical modeling of cavitation in a convergent-divergent nozzle of circular cross-section. Cavitation depends on the physical properties of the flowing medium as a function of temperature. Usually, cavitation in water is defined by a two-phase flow of water and vapor, but the air contained in the water significantly affects cavitation. There is usually no vapor cavitation in the oil. Far more often, cavitation in oil is caused by the air it contains. For comparison, cavitation in water and oil was generated in experiments with an identical nozzle. The measurement was used to define boundary conditions in mathematical models and to verify simulations. The problem of cavitation was solved by three variants of multiphase flow, single-phase flow (water, oil), two-phase flow (water–vapor, oil–air) and three-phase flow (water–vapor–air, oil–vapor–air). A turbulent model with cavitation was used for all variants. The verification of simulations shows that for water cavitation it is necessary to use a three-phase model (water, vapor, air) and for oil cavitation a two-phase model (oil, air) is sufficient. The measurement results confirm the importance of the air phase in modeling cavitation in both water and oil.

Design and construction of a simplified, gas-driven, pressure-controlled emergency ventilator

INTRODUCTION

Due to the COVID-19 crisis or any other mass casualty situation it might be necessary to give artificial ventilation to many affected patients. Contrarily, the worldwide availability of emergency ventilators is still a shortage, especially in developing countries.

METHODS

Modes of artificial ventilation were compared and the most safe, easy to use, and lung protecting principle was optimized to fit all requirements of both emergency ventilation and cost-effective mass production.

RESULTS

The presented research results describe a simplified device for a pressure-controlled ventilation which works without electricity according to a known principle. Just pressurized gas and a patient connection is required. The device enables the control of basic ventilator parameters such as peak inspiratory pressure, positive end-expiratory pressure and the ventilation frequency. Further, the device is semiadaptive to the patient's lung stiffness and automatically maintains minute volume through frequency adjustment. The machine can be manufactured by turning, milling and drilling and needs purchased components with costs less than 100 USD. A sterilization and thus a reuse is possible.

DISCUSSION

The presented development does not describe a ready-to-purchase ventilator, it rather outlines a refined working principle for emergency ventilation and its easiest methods of production with a minimum of requirements. The presented research aims on providing an open-source guideline for production of an emergency ventilator using worldwide available methods and thus should inspire local researchers to do a reverse engineering and eventually to put it into operation following country-specific regulations. For long-term ventilation exceeding emergency purposes, a monitoring of alarms for disconnection and violation of desired ventilator parameters should be established. The ventilator is limited to a fixed ratio between PIP and PEEP. Moreover, the ventilation frequency depends on two parameters, which needs some training. Nevertheless, the ventilator provides basic features to enable an emergency ventilation with minimal prerequisites.

Considering the Diffusive Effects of Cavitation in a Homogeneous Mixture Model

Homogeneous mixture models are widely used to predict the hydrodynamic cavitation. In this study, the constant-transfer coefficient model is implemented into a homogeneous cavitation model to predict the heat and mass diffusion. Modifications are made to the average bubble temperature and the Peclet number for thermal diffusivity in the constant-transfer coefficient model. The evolutions of a spherical bubble triggered by negative pressure pulse are simulated to evaluate the prediction of heat and mass diffusion by the homogeneous model. The evolutions of three bubbles inside a rectangular tube are simulated, which show good accuracy of the homogeneous model for multibubbles in stationary liquid.

Special Issue: Smart Flow Control in Micro Scale

Smart control processes have been proposed for many years, while for smart flow control—especially when “smart flow control” comes at the microscale—it turns out that many new innovations and enabling technologies are possible [...]