A Moore-Greitzer Model for Ducted Fans in Ground Effect

Jin, Yuzhi; Fu, Y F; Qian, Yuping; Zhang, Y.

doi:10.29252/jafm.13.02.30640

Cited by 11 publications

(3 citation statements)

References 13 publications

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“…Han et al [34] conducted experimental measurements and CFD simulations to study the aerodynamic performance of a microscale ducted fan hovering in a confined environment, including the ground, ceilings, and walls. Jin et al [35] estimated the aerodynamic stability of a ducted fan in the ground effect with a modified Moore-Greitzer model. Han et al [36] compared the performance and flowfield characteristics of a ducted fan and an open propeller hovering in the ground effect by means of experiments and CFD simulations.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic Characteristics of a Ducted Fan Hovering and Transition in Ground Effect

2022

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Ducted fans installed on vertical takeoff and landing vehicles experience significant ground effect during takeoff and landing. The aerodynamic characteristics of a ducted fan hovering and transitioning in the ground effect are studied using numerical simulations in this paper. The flowfields are obtained by solving Reynolds Averaged Navier–Stokes equations with the Multiple Reference Frame approach. When a ducted fan hovers in the ground effect, the blade thrust increases due to the combined effect of the increase in the effective angle of attack of the blade and the increase in ambient pressure; the duct thrust decreases due to the combined effect of the decrease in the effective angle of attack of the duct and the increase in ambient pressure. Stall occurs at a certain advance ratio and angle of attack when transitioning in the ground effect. The ground effect delays the occurrence of stall at some advance ratios. The ground effect is hardly detectable at angles of attack less than 30° even if the height drops to 0.5 times the duct exit diameter. At this height and high angles of attack, the different positions and influence regions of the ground vortex at different advance ratios contribute to the different variation trends in the ducted fan performance.

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Section: Introductionmentioning

confidence: 99%

Aerodynamic Characteristics of a Ducted Fan Hovering and Transition in Ground Effect

2022

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“…Thus, centrifugal force contributes to a rapid rise of stress in first stage and the stable high stress in the last two stages. In addition to large centrifugal force, high rotating rate also leads to flow instabilities [26,27], which is another factor causing the high stress. There is circumferential velocity gradient between upper wall and lower wall of clearance, as shown in Figure 13.…”

Section: Mean Stresses Of Runnermentioning

confidence: 99%

Investigation on Dynamic Stresses of Pump-Turbine Runner during Start Up in Turbine Mode

Funan

Ahn

et al. 2021

Processes

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The startup process occurs frequently for pumped storage units. During this process, the rotating rate that changes rapidly and unsteady flow in runner cause the complex dynamic response of runner, sometimes even resonance. The sharp rise of stress and the large-amplitude dynamic stresses of runner will greatly shorten the fatigue life. Thus, the study of start-up process in turbine mode is critical to the safety operation. This paper introduced a method of coupling one dimensional (1D) pipeline calculation and three-dimensional computational dynamics (3D CFD) simulation to analyze transient unsteady flow in units and to obtain more accurate and reliable dynamic stresses results during start up process. According to the results, stress of the ring near fixed support increased quickly as rotating rate rose and became larger than at fillets of leading edge and band in the later stages of start-up. In addition, it was found that dynamic response can be caused by rotor stator interaction (RSI), but also could even be generated by the severe pressure fluctuation in clearance, which can also be a leading factor of dynamic stresses. This study will facilitate further estimation of dynamic stresses in complex flow and changing rotating rate cases, as well as fatigue analysis of runner during transient operation.

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“…Works of Yoon et al [15] as well as Van Helvoirt [13] and De Jager [16] were focused on incorporating the pipeline dynamics and acoustics into the model. The most recent works on the topic include: the development of parameter identification method by Backi et al [17] or a generalization of a Moore-Greitzer model for ducted fans in near ground conditions by Jin et al [18]. Although most attempts to surge modelling are largely based on the Greitzer model, there are other approaches not directly inheriting from it, for example, the one presented by Cousins and Davis in [19].…”

Section: Greitzer Model Of the Surge Phenomenonmentioning

confidence: 99%

Sensitivity Study of Greitzer Model Based on Physical System Parameters of Radial Compressing Units

Jaeschke

Liśkiewicz

2020

Energies

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Centrifugal compressors are key elements of energy systems and industrial installations including fluid flow. Their operating range is strictly limited by the surge phenomenon. The Greitzer model is a known way of simulating the compressor’s behaviour at the surge. In this paper, the parametric study of different versions of the Greitzer model is conducted. There are several versions of this model that include 4 to 2 equation models. The system behaviour depends on the features of the compressor itself as well as of the plenum. In this paper, all terms connected with the compressor were grouped into the “Co” parameter, while those associated with the plenum were grouped into the “Pl” parameter. The study shows how each component influences the system stability. The comparison of analytical data with experimental results allowed to draw conclusions regarding the way of choosing the model parameters that provide the best simulation of the real system behaviour. The study shows that the system is well simulated by a model with relatively large values of the Lc parameter. The length of the compressor parameter Lc=3.57 m was performing well for the machine with impeller radius 0.33 m. Possible explanations of this finding are presented and compared to the state of the art. This result may provide possible help in adjusting the model parameters for other machines and designing reliable anti-surge systems based on the Greitzer model suited to energy conversion systems.

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A Moore-Greitzer Model for Ducted Fans in Ground Effect

Cited by 11 publications

References 13 publications

Aerodynamic Characteristics of a Ducted Fan Hovering and Transition in Ground Effect

Aerodynamic Characteristics of a Ducted Fan Hovering and Transition in Ground Effect

Investigation on Dynamic Stresses of Pump-Turbine Runner during Start Up in Turbine Mode

Sensitivity Study of Greitzer Model Based on Physical System Parameters of Radial Compressing Units

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