Suction Position Research Articles

Process investigation of different locations of thermo-compressor suction in MED–TVC plants

The desalting of seawater has been a vital issue in several countries around the world in which water shortage is a serious problem. Through the process of designing desalination systems, with consideration of energy crisis, amount of energy consumption is a very important economical factor. In multi-effect distillation systems with thermal vapor compression (MED–TVC), thermo-compressor plays a main role in energy consumption. The geometry and operating conditions of thermo-compressor can have a significant influence on energy consumption. In this research, the influence of changing the suction position of thermo-compressor on the amount of energy consumption of the plant is analyzed. Results of the study showed that variation in suction pressure of thermo-compressor has considerable effects on the entrainment ratio. However, in order to have the maximum entrainment ratio and consequently reduce energy consumption, integration of MED–TVC with MED desalination must be optimized into the position of thermo-compressor suction. It was found that changing the suction location of thermo-compressor from the last effect to the middle effects or increasing the suction pressure has a valuable role in decreasing the energy consumption of the system. Results showed that the optimum value of compression ratio of thermo-compressor is between 2 and 2.5.

Effects of Boundary Layer Suction on Aerodynamic Performance in a High-load Compressor Cascade

This article is aimed to experimentally validate the beneficial effects of boundary layer suction on improving the aerodynamic performance of a compressor cascade with a large camber angle. The flow field of the cascade is measured and the ink-trace flow visualization is also presented. The experimental results show that the boundary layer suction reduces losses near the area of midspan in the cascade most effectively for all suction cases under test. Losses of the endwall could remarkably decrease only when the suction is at the position where the boundary layer has separated but still not departed far away from the blade surface. It is evidenced that the higher suction flow rate and the suction position closer to the trailing edge result in greater reduction in losses and the maximum reduction in the total pressure loss accounts to 16.5% for all cases. The suction position plays a greater role in affecting the total pressure loss than the suction flow rate does.

공동 공진해석을 이용한 왕복동식 압축기의 기동소음 저감에 관한 연구

This work focuses on finding a method to reduce the noise of a hermetic reciprocating compressor during start-up using an acoustical analysis. The noise of compressor during start-up, which is a higher level than that of a normal operating condition, has transient and non-stationary characteristics. The acoustical analysis of compressor cavity is performed to find an effective method to reduce the noise level. In the acoustical analysis, the shape variations of frequency response function in the neighborhood of resonances are tested for three parameters: the height of remained oil, the suction position of refrigerant and the position of driving part. As a conclusion of this result, to reduce the emission noise of compressor during start-up, the height of remained oil should be kept at 16 mm, the refrigerant should be sucked at the cross point of nodal lines of X and Y directional cavity modes, and the driving part should be positioned in the center of cavity.

First stages of the transition to turbulence and control in the incompressible detached flow around a NACA0012 wing

The present study analyses the successive transition steps in the flow around a high-lift wing configuration, as the Reynolds number increases in the low and moderate range (800–10,000), by the Navier–Stokes approach. The flow system is mainly governed by two kinds of organised modes appearing successively as the Reynolds number increases: the von Kàrmàn and the shear layer mode. A period-doubling scenario characterises the first 2D stages of the von Kàrmàn mode up to Reynolds number 2000, where the shear-layer mode becomes predominant. The successive stages of the 3D transition are also analysed in detail. In a second step, the effect of wall suction has been studied both in 2D and 3D flows around the NACA0012 airfoil at 20° of incidence and a Reynolds number of 800. This study has the objective to optimise the aerodynamic coefficients and to attenuate the mentioned 3D transition effects in the near wake. The receptivity of the flow to the suction is clearly shown and the suction position on the wall has been optimised according to the improvement of the aerodynamics coefficients.

Experiments on control of streamwise streaks

Control of streamwise velocity streaks are studied experimentally in a plane channel flow. High and low-velocity streaks are created by suction through streamwise slots and, further downstream, the secondary instability of the streaks is forced by speakers. The streaks are controlled by localized suction downstream of the disturbance generation. In a modified setup, reactive control is used in order to delay transition of low-velocity regions appearing at known spanwise positions randomly in time. As expected, the growth rate of the secondary instability decreases when localized suction is applied below a low-velocity streak. With control applied, transition is substantially delayed. The suction position and, in the case of reactive control of randomly appearing disturbances, the time instants at which control suction was turned on/off, were varied. The parameter study shows that the control suction has to be applied within a narrow region (10% of a streak width) around the centre of a low-velocity streak. The timing of the control suction is seen to be less critical.

Analysis of an oscillating Joukowski airfoil with surface suction and moving vortices

An attempt is made to enhance the beneficial effects of the trapped vortex by increasing its lingering period on the upper surface of a Joukowski airfoil in oscillating motions. Studies are made on the stability of a trapped free vortex when perturbed away from its equilibrium position with a finite displacement, and on the lingering period of the trapped free vortex in the upper vicinity of the airfoil. The computational results show that a proper combination of oscillation and suction might be an efficient method for trapping a free vortex to generate high lift on an airfoil. It is found that the trailing-edge suction position is more effective in capturing a free vortex for a longer lingering time and the lift increment directly dependent on the strength of the trapped vortex. This result may provide an explanation of the high lift generated by a dragonfly whose back wings are found to flap in a flow containing vortices shed from the front wings.

Gastric Suction in X-Ray Diagnosis: A New Method

In roentgen examination of the upper gastrointestinal tract the gastric secretion dilutes the barium, making the study more or less futile. Because of poor suction or incorrect position of the tube tip, aspiration with the usual stomach pump is often unsuccessful. The secretion may be removed completely, however, by continuous suction and a tube fitted with a steel ball (Figs.1 and 2). The vacuum is regulated by finger-tip control.