scholarly journals Effects of Shock Wave Phenomenon on Different Convergent Lengths in the Mixing Chamber of the Steam Ejector

2021 ◽  
Vol 03 (01) ◽  
pp. 93-100
Author(s):  
Stefan Mardikus ◽  
Keyword(s):  
Shock Wave ◽  
Wave Phenomenon ◽  
High Speed ◽  
Working Fluid ◽  
Operating Pressure ◽  
Wave Effect ◽  
Primary Flow ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber

The shock wave phenomenon is a phenomenon in a steam ejector that caused when the working fluid has high pressure, and suddenly it turns into low pressure and high speed. The shock wave effect will be investigated to the different convergent length in the mixing chamber to find the highest entrainment ratio as the performance of steam ejector. Operating pressure in the primary flow was in the range 0.68 MPa - 1.39 MPa, and the secondary flow was set 0.38 MPa to 0.65 MPa. The result of this study demonstrated that the highest entrainment ratio occurred in the convergent length of 69 mm.

Computational fluid dynamics simulation of the supersonic steam ejector. Part 2. Optimal design of geometry and the effect of operating conditions on the ejector

2011 ◽  
Vol 226 (3) ◽  
pp. 715-723 ◽  
Author(s):  
L Cai ◽  
H T Zheng ◽  
Y J Li ◽  
Z M Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Optimal Design ◽  
Critical Pressure ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber

The aim of this study is to investigate the use of computational fluid dynamics in predicting the performance and optimal design of the geometry of a steam ejector used in a steam turbine. In the current part, the real gas model was considered using IAPWS IF97 model, and the influences of working fluid pressure and backpressure were investigated. The results illustrate that working critical pressure and backflow critical pressure exist in the flow. Moreover, the entrainment ratio reaches its peak at the working critical pressure. The performance of the ejector was nearly the same when the outlet pressure was lower than the critical backpressure. Effects of ejector geometries were also investigated. The distance between the primary nozzle and the mixing chamber was at optimum, the length of the mixing chamber and the diameter of the throat had an optimal value according to the entrainment ratio. When the length of the diffuser or throat was decreased within a range, the entrainment ratio did not change significantly.

scholarly journals Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector

2021 ◽  
Vol 11 (13) ◽  
pp. 6111
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Jiuxin Ning ◽  
Pengfei Zhang ◽  
Hailong Huang
Keyword(s):  
Flow Structure ◽  
Mass Fraction ◽  
Internal Flow ◽  
Working Fluid ◽  
Physical Parameters ◽  
Entrainment Ratio ◽  
Air Mass ◽  
Steam Ejector ◽  
Primary Fluid ◽  
Mass Fractions

This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system.

Numerical Simulation of Performance of Steam Ejector Influenced by the Distance between Nozzle Outlet and Mixing Chamber Inlet

2011 ◽  
Vol 299-300 ◽  
pp. 970-973
Author(s):  
Xiao Chun Dai ◽  
Guo Jin Liao
Keyword(s):  
Numerical Simulation ◽  
Geometric Parameters ◽  
Experimental Results ◽  
Nozzle Outlet ◽  
Entrainment Ratio ◽  
Optimum Range ◽  
Steam Ejector ◽  
Mixing Chamber ◽  
Throat Diameter

The performance of a steam ejector was simulated using FLUENT. The performance of steam ejector was studied by changing the distance between primary nozzle outlet and mixing chamber inlet (DPM) while operating pressures and other geometric parameters were not varied. The entrainment ratios of the steam ejector with different values of DPM were calculated. The optimum range of DPM was given, which is changed from 1.8 to 2 times of the throat diameter of hybrid diffuser pipe. The errors of the CFD results to the experimental results of the entrainment ratio are not more than 15%.

scholarly journals Simulasi Numerik Aliran Melewati Nozzle Pada Ejector Converging – Diverging Dengan Variasi Diameter Exit Nozzle

2017 ◽  
Vol 2 (1) ◽  
pp. 19
Author(s):  
Novi Indah Riani ◽  
Syamsuri Syamsuri ◽  
Rungky Rianata Pratama
Keyword(s):  
Operating Conditions ◽  
Vapor Compression ◽  
Cooling Process ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber ◽  
Exit Nozzle ◽  
Flow Phenomena ◽  
Ejector Nozzle ◽  
Simulation Results

In the process of cooling or refrigeration, are required components where capable to flow the fluid to create a cycle of the cooling process. Among some of the vapor compression systems, the usage of ejector is the simplest system. Ejector has three main parts: primary nozzle, mixing chamber and diffuser. Various experiments of steam ejectors developed to increase the value of the COP. Entrainment ratio directly affects to the COP value generated by the system, where the geometric shapes and operating conditions in the steam ejector will affect to the value entrainment ratio. This research was carried out numerical simulations using CFD commercial software with k-epsilon to predict flow phenomena which passes through the ejector nozzle in the ejector converging-diverging which varying exit diameters 3.5 mm; 4mm; 5 mm; and 5.5 mm. Respectively the simulation results showed exit nozzle steam ejector that the smallest diameter of 3.5 mm give the optimum performance because it provide the highest speed of fluidity. While the state of vacuum in mixing chamber increase, it cause the secondary mass flow higher as well as the value of the entrainment ratio.

scholarly journals Windage Power Loss in Gas Foil Bearings and the Rotor-Stator Clearance of High Speed Generators Operating in High Pressure Environments

2009 ◽  
Author(s):  
Robert J. Bruckner
Keyword(s):  
Power Loss ◽  
High Speed ◽  
Working Fluid ◽  
Total System ◽  
Operating Pressure ◽  
Foil Bearings ◽  
Maximum Test ◽  
Long Duration ◽  
System Output ◽  
Starter Generator

Closed Brayton Cycle (CBC) and Closed Supercritical Cycle (CSC) engines are prime candidates to convert heat from a reactor into electric power for robotic space exploration and habitation. These engine concepts incorporate a permanent magnet starter / generator mounted on the engine shaft along with the requisite turbomachinery. Successful completion of the long duration missions currently anticipated for these engines will require designs that adequately address all losses within the machine. The preliminary thermal management concept for these engine types is to use the cycle working fluid to provide the required cooling. In addition to providing cooling, the working fluid will also serve as the bearing lubricant. Additional requirements due to the unique application of these microturbines are zero contamination of the working fluid and entirely maintenance-free operation for many years. Losses in the gas foil bearings and within the rotor-stator gap of the generator become increasingly important as both rotational speed and mean operating pressure are increased. This paper presents the results of an experimental study, which obtained direct torque measurements on gas foil bearings and generator rotor-stator gaps. Test conditions for these measurements included rotational speeds up to 42000 revolutions per minute, pressures up to 45 atmospheres, and test gases of Nitrogen, Helium, and Carbon Dioxide. These conditions provided a maximum test Taylor number of nearly one million. The results show an exponential rise in power loss as mean operating density is increased for both the gas foil bearing and generator windage. These typical “secondary” losses can become larger than the total system output power if conventional design paradigms are followed. A non-dimensional analysis is presented to extend the experimental results into the CSC range for the generator windage.

scholarly journals A Numerical Study on the Supersonic Steam Ejector Use in Steam Turbine System

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Lin Cai ◽  
Miao He
Keyword(s):  
Steam Turbine ◽  
Numerical Study ◽  
Fluid Pressure ◽  
Ideal Gas ◽  
Entrainment Ratio ◽  
Real Gas ◽  
Steam Ejector ◽  
Mixing Chamber ◽  
Cfd Method ◽  
Ideal Gas Model

Supersonic steam ejector is widely used in steam energy systems such as refrigeration, wood drying equipment, papermaking machine, and steam turbine. In this paper the Computational Fluids Dynamics (CFD) method was employed to simulate a supersonic steam ejector, SST k-w turbulence model was adopted, and both real gas model and ideal gas model for fluid property were considered and compared. The mixing chamber angle, throat length, and nozzle exit position (NXP) primary pressure and temperature effects on entrainment ratio were investigated. The results show that performance of the ejector is underestimated using ideal gas model, and the entrainment ratio is 20%–40% lower than that when using real gas model. There is an optimum mixing chamber angel and NXP makes the entrainment ratio achieve its maximum; as throat length is decreased within a range, the entrainment ratio remains unchanged. Primary fluid pressure has a critical value, and the entrainment ratio reaches its peak at working critical pressure; when working steam superheat degree increases, the entrainment ratio is increased.

scholarly journals Visualization of Shock Wave Phenomenon around a Sharp Cone Model at Hypersonic Mach Number in a Shock Tunnel using High Speed Schlieren Facility

2019 ◽  
Vol 12 (2) ◽  
pp. 461-468
Author(s):  
M. Saiprakash ◽  
C. Senthil Kumar ◽  
G. K. Sunil ◽  
S. P. Rampratap ◽  
V. Shanmugam ◽  
...  
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Wave Phenomenon ◽  
High Speed ◽  
Shock Tunnel ◽  
Cone Model ◽  
Sharp Cone

Analysis of Flow Field in an Ejector With Steam as Working Fluid

2004 ◽  
Author(s):  
Haijun Li ◽  
Shengqiang Shen
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Pressure ◽  
Navier Stokes ◽  
Working Fluid ◽  
Complex Flow ◽  
Entrainment Ratio ◽  
Navier Stokes Equations ◽  
Saturated Water ◽  
Steam Ejector

Two-dimensional Navier-Stokes equations were solved to obtain local distributions of pressure, temperature and Mach number of the complex flow field in a steam ejector. From the computational results, we obtain that there is a critical discharging pressure for given motive pressure and suction pressure. The effects of motive fluid pressure, motive fluid overheat, suction fluid pressure and discharge fluid pressure on the entrainment ratio and critical discharging pressure were concluded in detail. Analysis was also done to comprehend the reason of shocks emerging, their positions, and their effects on ejector performance. Phase transition phenomenon occurred in the ejector when using steam as working fluid was obtained through calculating the percent of saturated water in the mixture. The effect of the ejector’s geometrical structure on its performance is further studied and high COP of the ejector is gained by optimizing its structure.

CFD Analysis of Refrigeration Cycle Ejector

2021 ◽  
Author(s):  
Franz X. Forster ◽  
Alexander E. Deravanessian ◽  
Matthew J. Nazarian ◽  
Mariano Rubio ◽  
Kevin R. Anderson
Keyword(s):  
Peak Performance ◽  
Chamber Pressure ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Working Fluids ◽  
Mixing Chamber ◽  
Computational Fluid Dynamics Cfd ◽  
R 134A ◽  
Ejector Cycle ◽  
Pressure Boundary Conditions

Abstract The use of ejector cycles for increased performance and efficiency is becoming more prevalent in industry. The goal of this study is to evaluate an ejector using Computational Fluid Dynamics (CFD) to evaluate flow patterns, perform trade studies varying the type of refrigerant, and determine the entrainment ratio for each working fluid, over a range of boundary condition pressures, set at points along the ejector’s flow path. The 2012 Toyota Prius V is one of the first automobiles using an ejector cycle in their internal cabin refrigeration system. The DENSO Corporation ejector hardware was used as the basis for the creation of geometry for the CFD mode of the ejector. Three working fluids were simulated, R-134a, R-245fa, and R-1235yf. The primary findings of this study were as follows. The CFD study here indicates that R-245fa performs the best out of the three working fluids, when examining their entrainment ratios (ratio of secondary to primary flow rates in the ejector). For all three working fluids, the entrainment ratio was seen to peak performance at an ejector inlet pressure of 1.75 × 105 Pa. The ejector mixing chamber pressure and ejector outlet pressure boundary conditions also witnessed a rise in entrainment ratios, during an increase of their respective pressure values.

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