Water-air ejector with conical-cylindrical mixing chamber

In the paper, the hydrodynamics of the liquid-gas mixture in the mixing chamber of the ejectors at different spatial positions was analyzed and the comparative study of such ejectors was carried out. It was found that a more ordered mode of movement of the mixture in the mixing chamber is created as a result of the coincidence of the velocity vector of liquid drops and the direction of gravity in the vertical position of the ejectors. This leads to increasing the volume entrainment ratio almost twice. The analysis of the liquid-gas mixture flow in the mixing chamber, evaluation calculations and research allowed to develop and to patent a jet apparatus with a conical-cylindrical (combined) mixing chamber. It was also found that for such ejectors, the volume entrainment ratio is 15–55% higher than for a jet apparatus with a cylindrical mixing chamber due to the reduction of the resistance of the passive flow into the mixing chamber and prevention of the formation of reverse-circulating flows. A study has been conducted on liquid-gas ejectors in the range of the main geometric parameter m (ratio of the mixing chamber area to the nozzle area) 9.4–126.5, which allowed to establish its rational values at which the maximum volume entrainment ratio is achieved (m = 25–40).

Three- dimensional numerical simulation analysis of the influence of structural parameters on the performance of air ejector

Nowadays, CFD technology has become the third tool to study hydrodynamics problems after theoretical analysis and experimental research, especially in dealing with and solving complex engineering problems such as supersonic. In this paper, using the method of control variables, the system studied a type air ejector structure parameters within a certain range changes affect the performance of the work by means of FLUENT, at the same time, the optimal combination of the structural parameters are given, then three dimensional numerical simulation of the optimal combination model, and the simulation value and experiment value has carried on the contrast and analysis, Compared with the two-dimensional and axisymmetric model, Three-dimensional calculation model is more reliable and reasonable.

An experimental investigation of the use of an outlet silencer to quiet ejectors

Ejectors are simple fluid movers and mixers used in a range of industries; however, the attractiveness of their simplicity can be offset by high levels of noise generation. This work experimentally investigates the use of a silencer affixed to the outlet of a subsonic air–air ejector as a means of quieting the ejector. An emphasis is placed on finding a silencer design which has a minimal impact on the mass flow rate exhausting from the ejector (pumping performance). This paper discusses the results of 10 different silencer designs, tested in an attempt to further understand noise generation mechanisms and to find a practical method to reduce the noise of ejectors. It is found that the placement of a perforated cone at the mid-length of the silencer is the only solution tested which provides a significant acoustic advantage with only a small drop in pumping performance. Other solutions tested provide either no acoustic advantage or have too great of a reduction in pumping performance. It is found that the size and shape of the ejector can be designed in such a way to reduce the overlap of natural modes and thus the overall noise levels of the ejector caused by high levels of resonance. The use of acoustic foam to dampen acoustic natural modes proves that the natural modes of the ejector are a significant contributor to the overall noise levels.

Dynamic Processes in Vacuum Contact Devices of Robots for Vertical Motion in the Water Environment

The results of experimental investigation intended to improve movement conditions for pneumatic robots on vertical surfaces under water are discussed. Features of the movement of vacuum contact devices for the simulation of mathematical model of the vacuum contact device with surfaces under water are presented. The experimental studies made it possible to obtain additional data on the dynamics of attachment, to obtain transient processes for air-water flow through ejector and to correct the results obtained earlier. For the purpose of analytical study of dynamic processes occurring in the system of vacuum contact devices, and taking into account the complexity of the description of nonlinearities, linearized simplified models of the system "air ejector — contact device — water environment" were developed. Vacuum contact devices are designed to provide guaranteed contact with vertical surfaces, plane slopes or horizontal surfaces on which the underwater robot performs its movement, carrying out the prescribed technological tasks, for example, in dry wells of nuclear power plants, on the surfaces of ship hulls, on the surfaces of underwater structures. The models took into account the forces of adhesion to the surfaces under water — the forces from the pressure drop, the friction force, the contact and vacuum interaction, the elasticity of suction caps. As a result of the solution of the model problem, the values of mechanical parameters, as well as the values of vacuum and flow in the cavity of variable volume as functions of changing the gap between the end of the corrugated membrane and the surfaces are obtained explicitly. As a result of the study of dynamic processes occurring in simplified models of vacuum contact devices "air ejector — contact surface — water environment", the transient characteristics of the change in the operating forces and pressures over time, as well as the dependence of the normal and tangential components of the forces on the depth of immersion in water were obtained. The variants of the designs of vacuum contact devices with surfaces in the water environment are investigated, and the modernization of the laboratory test bench for testing vacuum contact devices under water is carried out.

MENJAGA KESTABILAN SUHU RUANG EVAPORATOR BERDAMPAK PADA HASIL PRODUKSI AIR TAWAR FRESH WATER GENERATOR

<p><em>Maintaining a Fresh Water Generator from the loss of vacuuming means getting the best fresh water production process. The balance of the heated substance and the heater measurement inside the evaporator could effect on the steam result or even could influence the steam process. There are many factors that could cause the loss or the decreasing of vacuuming when operating Fresh Water Generator, such as system leakage, the lack of sea water volume used for vacuuming, the balance of water ejector capability to maintain the steam volume inside Fresh Water Generator, the brine ejector capability to maintain the unused brine water and condension water being exhaust of Fresh Water Generator. </em></p><p><em><strong>Keywords</strong>: Condenser, Evaporator, Ejector, Ejector Pump</em></p><p>Menjaga serta mempertahankan kondisi Fresh Water Generator dari kevakuman merupakan hal yang harus selalu diperhatikan secara baik,dengan tujuan untuk mendapatkan proses produksi air tawar secara optimal. Pengaturan keseimbangan antara media untuk memanaskan dan media untuk dipanaskan didalam ruang evaporator berdampak pada hasil uap yang diproduksi ataupun justru berpengaruh terhadap proses penguapan. Banyak faktor penyebab hilangnya ataupun turunnya kevakuman pada saat pengoperasian fresh water generator,seperti kebocoran pada sistem,kurangnya kapasitas volume air laut yang digunakan oleh ejector pump untuk proses kevakuman, tidak seimbangnya kemampuan air ejector menjaga jumlah uap yang ada di dalam ruang fresh water generator , kemampuan brine ejector menjaga jumlah air brine dan air kondensasi yang tidak tertampung diruang kondensor untuk di buang keluar dari ruang fresh water generator.</p><p><strong>Kata kunci</strong> : Kondensor, Evaporator, Ejector, Ejector Pump</p>