Analysis of the suction chamber of external gear pumps and their influence on cavitation and volumetric efficiency

Hydraulic machines are faced with increasingly severe performance requirements. The need to design smaller and more powerful machines rotating at higher speeds in order to provide increasing efficiencies, has to face a major limitation: cavitation. A two-dimensional numerical approach, by means of Computational Fluid Dynamics (CFD), has been developed for studying the effect of cavitation in the volumetric efficiency of external gear pumps. Several cavitation models and grid deformation algorithms have been studied, and a method for simulating the contact between solid boundaries has been developed. The velocity field in the inlet chamber has also been experimentally measured by means of Time-Resolved Particle Image Velocimetry (TRPIV) and results have been compared to the numerical ones in order to validate the accuracy of the model. Our two-dimensional model is not able to predict the real volumetric efficiency of the pump, since several simplifications are involved in it. Nevertheless, this model shows to be valid to understand the complex flow patterns that take place inside the pump and to study the influence of cavitation on volumetric efficiency. The influence of the rotational speed of the pump has been analyzed, as well as the effect of the geometry of the inlet chamber, the working pressure, the inlet pressure loss factor, and the flow leakage through the radial clearances of the pump between gears and casing

Analysis of the suction chamber of external gear pumps and their influence on cavitation and volumetric efficiency

Hydraulic machines are faced with increasingly severe performance requirements. The need to design smaller and more powerful machines rotating at higher speeds in order to provide increasing efficiencies, has to face a major limitation: cavitation. A two-dimensional numerical approach, by means of Computational Fluid Dynamics (CFD), has been developed for studying the effect of cavitation in the volumetric efficiency of external gear pumps. Several cavitation models and grid deformation algorithms have been studied, and a method for simulating the contact between solid boundaries has been developed. The velocity field in the inlet chamber has also been experimentally measured by means of Time-Resolved Particle Image Velocimetry (TRPIV) and results have been compared to the numerical ones in order to validate the accuracy of the model. Our two-dimensional model is not able to predict the real volumetric efficiency of the pump, since several simplifications are involved in it. Nevertheless, this model shows to be valid to understand the complex flow patterns that take place inside the pump and to study the influence of cavitation on volumetric efficiency. The influence of the rotational speed of the pump has been analyzed, as well as the effect of the geometry of the inlet chamber, the working pressure, the inlet pressure loss factor, and the flow leakage through the radial clearances of the pump between gears and casing.Postprint (published version

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Preliminary study on fluidic actuators. Design modifications

As fluidic actuators have the advantage of lacking moving parts, their use in real applications brings high reliability. This is why, once having overcome their drawbacks, which means being able to provide the appropriate momentum and frequency, they could extensively be used in a wide range of applications. The present paper will present a CFD evaluation of the flow inside a fluidic oscillator. Initially a standard fluidic actuator will be simulated and the results compared with existing experimental data. In a second step, several geometric parameters will be modified; the actuator performance under these new conditions is reported. The paper aims to be an aid for future innovative oscillator designs.Peer ReviewedPostprint (published version

Preliminary study on fluidic actuators. Design modifications

As fluidic actuators have the advantage of lacking moving parts, their use in real applications brings high reliability. This is why, once having overcome their drawbacks, which means being able to provide the appropriate momentum and frequency, they could extensively be used in a wide range of applications. The present paper will present a CFD evaluation of the flow inside a fluidic oscillator. Initially a standard fluidic actuator will be simulated and the results compared with existing experimental data. In a second step, several geometric parameters will be modified; the actuator performance under these new conditions is reported. The paper aims to be an aid for future innovative oscillator designs.Peer Reviewe

Preliminary study on fluidic actuators. Design modifications

As fluidic actuators have the advantage of lacking moving parts, their use in real applications brings high reliability. This is why, once having overcome their drawbacks, which means being able to provide the appropriate momentum and frequency, they could extensively be used in a wide range of applications. The present paper will present a CFD evaluation of the flow inside a fluidic oscillator. Initially a standard fluidic actuator will be simulated and the results compared with existing experimental data. In a second step, several geometric parameters will be modified; the actuator performance under these new conditions is reported. The paper aims to be an aid for future innovative oscillator designs.Peer Reviewe

Research on fluidic amplifiers dimensional modifications via computer simulation (CFD)

When studying active flow control applications, it is already stated that activating the boundary layer via using periodic flow produces better performance than when employing steady blowing or sucking. This is why studying the performance characteristics of devices like fluidic oscillators and zero net mass flow actuators is particularly interesting. In the present paper a particular configuration of fluidic oscillator is carefully analyzed, initially its dynamic performance is compared with experimental results undertaken by previous researchers, then the dimensional internal characteristics are modified in order to obtain how is the dynamic behavior being affected, in a third stage the evaluation of how fluidic oscillators scale is affecting its dynamic performance is also presented. Based on the results obtained it can be concluded that a given actuator working at a given Reynolds number, is capable of producing different frequencies and amplitudes when modifying some dimensional parameters.Peer Reviewe

Research on fluidic amplifiers dimensional modifications via computer simulation (CFD)

When studying active flow control applications, it is already stated that activating the boundary layer via using periodic flow produces better performance than when employing steady blowing or sucking. This is why studying the performance characteristics of devices like fluidic oscillators and zero net mass flow actuators is particularly interesting. In the present paper a particular configuration of fluidic oscillator is carefully analyzed, initially its dynamic performance is compared with experimental results undertaken by previous researchers, then the dimensional internal characteristics are modified in order to obtain how is the dynamic behavior being affected, in a third stage the evaluation of how fluidic oscillators scale is affecting its dynamic performance is also presented. Based on the results obtained it can be concluded that a given actuator working at a given Reynolds number, is capable of producing different frequencies and amplitudes when modifying some dimensional parameters.Peer Reviewe

Fluidic actuator performance variation via internal dimensions modifications

When aimed to modify the downstream vortex shedding of a given bluff body, whether any road vehicle or wing profile, the use of Active Flow Control (AFC) appears to be an efficient technology. Among the different (AFC) methodologies the use of periodic forcing is ment to have better efficiency since it requires less energy to activate the shear layer, the reason behind this efficiency lies on the fact that periodic forcing interacts with the shear layer natural instabilites. In the present paper, one of the devices widely emloyed to generate pulsating flow, is carefully studied via 3D-CFD and using OpenFOAM. Initially the base flow is being determined and compared with previous experimental results, in a second step several internal dimensions of the fluidic actuator are being modified to characterize the output frequency and amplitude variations, among the conclusions obtained it is found that a given fluidic actuator is capable of generating several output frequencies and amplitudes when modifying some internal dimensions while maintaining a constant incoming flow Reynolds number.Postprint (published version