Numerical investigation of geometry parameters for design of high performance ejectors

Zhu, Yinhai; Cai, Wenjian; Chen, Wen; Li, Yanzhong

doi:10.1016/j.applthermaleng.2008.04.025

Cited by 271 publications

(81 citation statements)

References 21 publications

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“…Most CFD ejector models have been validated by comparing with experimental data [13], [14], [15] with most authors claiming acceptable agreement with experimental results [16]. In some of these studies, simulations have been within 10% of the experimental data [4], but errors around 20% have been reported in [4].…”

Section: Introductionmentioning

confidence: 98%

CFD Study of a Variable Flow Geometry Radial Ejector

Rahimi¹,

Buttsworth²,

Malpress³

2017

Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17)

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-To achieve higher performance from ejectors at some working conditions, implementations of variable geometry might be possible. While axisymmetric ejectors with axial flow paths have limitations that make practical implementation of variable geometry difficult, radial ejector configurations have a flow path that is conducive to changes in nozzle and ejector throat area during operation. The geometric adjustment of the radial ejector could be made by simply changing the separation of the radial ejector duct walls and/or the separation of the nozzle walls in order to optimize performance over a range of different conditions. The effects of such changes on the performance of a radial ejector have been investigated using a Computational Fluid Dynamic (CFD) analysis with ANSYS FLUENT software. Axisymmetric CFD models were generated to assess performance for a primary nozzle throat area of 8.792 mm 2 and for ejector throat separations of 2.2 mm, 2.4 mm and 3.0 mm, corresponding to ejector throat areas of 497, 543 and 678 mm 2 , respectively. The CFD analysis reveals that changes ejector performance can be achieved by changing the ejector duct's separation. An increase of 34% in entrainment ratio can be achieved by increasing the ejector throat separation from 2.2 mm to 3.0 mm at fixed primary and secondary pressures of 160 kPa and 1.8 kPa, respectively. If an increase in the ejector malfunction pressure is needed, it could be achieved by decreasing the ejector duct separation. An overall malfunction pressure increase of 18% can be achieved by decreasing the ejector throat separation from 3.0 mm to 2.2 mm at primary and secondary pressures of 250 and 1.8 kPa, respectively.

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Section: Introductionmentioning

confidence: 98%

CFD Study of a Variable Flow Geometry Radial Ejector

Rahimi¹,

Buttsworth²,

Malpress³

2017

Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17)

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“…The flow in the ejector is governed by compressible steady flows are uniformly distributed in the radial direction [3]. Recently, a shock circle model has been proposed to tackle the actual non-uniform velocity distribution by introducing a ''shock circle" at entrance of the constant-area mixing chamber [4,5].…”

Section: Governing Equationsmentioning

confidence: 99%

Study of the Configuration and Performance of Air-Air Ejectors based on CFD Simulation

Am¹,

Mh²,

Zm³

et al. 2017

J Aeronaut Aerospace Eng

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This paper describes a numerical study of gas-gas ejector performance for different operating conditions and geometrical configurations. The performance of ejector obtained based on a simulation procedure of linearized and axisymmetric subsonic and supersonic flow using Fluent Package. A conventional finite-volume scheme utilized to solve two-dimensional transport equations with the standard k-ω SST turbulence model. The model is solved in three regions namely, the primary flow nozzle, the secondary flow channel, and the region of interaction between the supersonic nozzle jet and the secondary flow. The effect of gas motive pressure the mixing part and tail section (pipe or diffuser) geometry on the ejector performance are studied. The computational results are validated using published experimental data with acceptable agreements. The numerical results indicate that the ejector geometry has a pronounced effect on the flow parameters (i.e., pressure and gas velocity) and the ejector performance. In addition, predicted numerical results indicate that when the motive-stream velocity exceeds the speed of sound, shock waves are unavoidable inside ejectors and that shock wave pattern in mixing part has a dominant effect on ejector performance. In addition, the results indicate that the shock location inside the nozzle and the separation point are affected by the motive pressure. The results show also that configuration with convergent-divergent mixing section is much better for mixing process than the other tested configurations.

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“…The turbulence model k--RNG is such a model which can accurately handle both the higher and lower Reynolds number (ANSYS FLUENT User's Guide, 2010). Also, in the previous studies this model was chosen and were used effectively (Chen et al 2011;Zhu et al 2009;Bartosiewicz et al 2005). This model relies on the Boussinesq hypothesis.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…ASHRAE (ASHRAE, 1983) and ESDU (ESDU, 1985) have proposed the suction chamber and diffuser angles as 7-10° and 3-4° respectively, however this range is not suitable for all the fluids and operating conditions as well (Zhu et al 2009). Therefore, it is clear that the geometrical parameters, especially the annular area available for the passive steam to start accelerating has the major role in the performance.…”

Section: Introductionmentioning

confidence: 99%

Analytical and Numerical Studies of a Steam Ejector on the Effect of Nozzle Exit Position and Suction Chamber Angle to Fluid Flow and System Performance

Ramesh¹,

Sekhar²

2017

JAFM

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Nozzle exit position [NXP] plays a vital role in the performance of the ejector, but its values are specified in a range for the required operating condition. In this study instead of the range of values, a specific value, named as entrainment diameter is developed and its effect on the performance of the ejector is studied for several combinations of suction chamber angle using numerical method. The effect of the condenser and boiler pressures on the performance of the ejector are also studied to ensure the off-design operating conditions. The entrainment diameter of an ejector is derived analytically by solving one dimensional compressible fluid flow equations using MATLAB. To study the effect of entrainment diameter on the performance of the ejector, CFD technique is employed. Analytical and numerical results are validated with experimental data available in the previous studies. For 7 kW refrigeration capacity, it is inferred that the suction chamber angle of 18° and the corresponding entrainment diameter 90.8 mm with the NXP of 23.62 mm yield the maximum entrainment ratio. The study predicts that the performance of the ejector is highly influenced by the pressure increment at the exit of the nozzle, while the suction chamber angle is between 12° to 21°.

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Numerical investigation of geometry parameters for design of high performance ejectors

Cited by 271 publications

References 21 publications

CFD Study of a Variable Flow Geometry Radial Ejector

CFD Study of a Variable Flow Geometry Radial Ejector

Study of the Configuration and Performance of Air-Air Ejectors based on CFD Simulation

Analytical and Numerical Studies of a Steam Ejector on the Effect of Nozzle Exit Position and Suction Chamber Angle to Fluid Flow and System Performance

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