Ejectors Design in the Rolls-Royce 1MW Hybrid System

Bernardi, D.; Bozzolo, Michele; Marsano, Francesco; Tarnowski, Olivier; Agnew, Gerry

doi:10.1115/gt2005-68085

Cited by 7 publications

(5 citation statements)

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“…constraints to be considered [8]. For instance, an anodic ejector has to ensure very high values of the recirculation factor (F) to avoid depositing carbon in the anodic circuit, even at off-design and transient conditions [9], and the main role of the cathodic ejector is to perform the required recirculation without excessive pressure difference between the compressor outlet and turbine inlet [10].…”

Section: Gt2006-90447mentioning

confidence: 99%

“…In previous works [8,10,11] the ejectors for hybrid system applications were studied at steady-state conditions from both theoretical and experimental points of view. In fact, in [11] the authors have shown a new design procedure based on 0-D and 2-D/3-D CFD models, successfully validated with the experimental results obtained with the closed-loop ejector-test rig developed at University of Genoa [3,10].…”

Section: Figure 2 Anodic Ejector Layoutmentioning

confidence: 99%

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Experimental Validation of an Unsteady Ejector Model for Hybrid Systems

Ferrari

Pascenti

Massardo

2006

Volume 4: Cycle Innovations; Electric Power; Industrial and Cogeneration; Manufacturing Materials and Metallurgy

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The aim of this work is the experimental validation of a transient ejector model for hybrid system applications. This is a mandatory step in performing the transient analysis of the whole plant to avoid critical situations and to develop the control system. So, the anodic recirculation test rig already used in previous works to study the ejector design validating the steady-state 0-D and CFD models, was used in this work to perform tests at transient conditions and to validate the ejector transient model.\ud An initial validation was carried out at steady-state conditions, then the ejector transient model was successfully compared with the experimental data, also under unsteady conditions. A second step was carried out to better investigate the whole anodic recirculation system. So, the validated ejector transient model was connected to the components necessary to simulate the pipes, the valves and the anodic volume. Also in this case, the calculated results were successfully compared with the experimental data obtained with the laboratory test rig. The final part of the paper is devoted to the results obtained at impulse conditions. In fact, this work investigates the effects on the anodic ejector and on the whole anodic circuit coming from fuel line impulses caused by possible unsteadiness conditions. The results obtained with impulses at different frequency values were successfully compared with the experimental data

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Section: Gt2006-90447mentioning

confidence: 99%

Section: Figure 2 Anodic Ejector Layoutmentioning

confidence: 99%

Experimental Validation of an Unsteady Ejector Model for Hybrid Systems

Ferrari

Pascenti

Massardo

2006

Volume 4: Cycle Innovations; Electric Power; Industrial and Cogeneration; Manufacturing Materials and Metallurgy

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“…It is composed of a nozzle and a mixing duct (Fig. Recently, ejectors have been also considered for fuel recirculation in fuel cell vehicles [3,4]. Ejectors have several advantages, including its simplicity, reliability, and durability.…”

Section: Introductionmentioning

confidence: 99%

Mixing and Entrainment Characteristics in Circular Short Ejectors

Song

2015

Journal of Fluids Engineering

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Analytical and experimental investigations have been conducted to characterize the performance of "short" ejectors. In short ejectors, the core of primary (motive) flow still exists at the mixing duct exit, and nonuniform mixed flow is discharged from the mixing duct. Due to incomplete mixing, short ejector pumping performance is degraded and cannot be predicted by the existing "long" ejector models. The new analytical short ejector model presented in this paper is based on the control volume analysis and jet expansion model. The secondary (entrained) flow velocity and the corresponding shear layer (between the primary and the secondary flows) growth rate variations along the mixing duct are taken into account. In addition, measurements have been made in ejectors with length ratios (LRs) of two and three for an area ratio (AR) of 1.95; and a LR of two for an AR of 3.08. Velocity profiles at the mixing duct inlet and exit, and static pressure distribution along the mixing duct have been measured with pitot probes and pressure taps. All of the tests have been carried out at a Reynolds number of 420,000. Comparison shows that the new ejector model can accurately predict flow characteristics and performance of short ejectors. For all of the test cases, the velocity profiles at the mixing duct inlet and exit are well predicted. Also, both predictions and measurements show pumping enhancement with increasing mixing duct length. The pumping enhancement is due to the increase in the static pressure difference between the mixing duct inlet and atmosphere as the mixing duct is lengthened. Furthermore, both measured and predicted static pressure distributions along the mixing duct show a kink. According to the analysis, the kink occurs when the outer shear layer reaches the mixing duct wall, and the secondary flow velocity decreases along the mixing duct upstream of the kink and increases downstream of the kink. Thus, the new ejector model can accurately predict not only the integral performance but also different mixing regimes in short ejectors.

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“…The obtained mesh quality was about 0.5. This mesh was selected after some preliminary calculations to obtain a good solution independence from the grid [27,28]. Theses preliminary simulations showed about 13% change in the recirculation ratio (in comparison with the chosen approach) for a mesh composed of 252,000 cells and no significant variations for values higher than 500,000 cells.…”

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confidence: 99%

“…The turbulence model was chosen considering previous CFD calculations on ejectors: in[6] the authors demonstrated (on the basis of a comparison with the Large the Eddy Simulation tool and on results shown in[11]) that the k-epsilon model is an acceptable compromise between the solution accuracy and the calculation time (in agreement with the objectives of this study). For the inlet boundary conditions of the turbulence model, the Fluent default values were used (5% turbulent intensity, 10 turbulent viscosity ratio)[27,28]. According with a preliminary analysis, these values had a negligible effect on the results.…”

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confidence: 99%

Validated ejector model for hybrid system applications

Ferrari

Pascenti

Massardo

2018

Energy

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The aim of this work is the presentation of a new model for ejector performance calculation using a commercial tool. Due to the critical issues in recirculation performance, special attention is devoted to applications in hybrid systems based on high temperature fuel cells. The theoretical activity is supported by an experimental rig able to operate tests on ejectors at different operative conditions, with a layout similar to the fuel cell anodic recirculation. The model validation, operated considering experimental data obtained with this rig, is essential to evaluate the tool performance for design and off-design calculations. This aspect is particularly critical due to important limitations in the recirculation ratio (especially for the anodic side), to avoid unacceptable operative conditions in the fuel cells.The results presented in this work were obtained with this validated model for an ejector applied on the anodic side of a Solid Oxide Fuel Cell (SOFC). A parametric analysis was carried out to show the effects of several parameters on the recirculation performance. The fully independent analysis of the influence of different properties (carried out with a specifically validated model) is an important innovative result for the application of such ejectors on high temperature fuel cells.

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Ejectors Design in the Rolls-Royce 1MW Hybrid System

Cited by 7 publications

References 0 publications

Experimental Validation of an Unsteady Ejector Model for Hybrid Systems

Experimental Validation of an Unsteady Ejector Model for Hybrid Systems

Mixing and Entrainment Characteristics in Circular Short Ejectors

Validated ejector model for hybrid system applications

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