The physics of pressure variation in microchannels within corotating or static discs

Guha, Ayan; Sengupta, Sayantan

doi:10.1063/1.4963370

Cited by 6 publications

(6 citation statements)

References 32 publications

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“…The power input per channel increases because of the increase in the overall pressure drop Δpio which is mainly attributed to the fact that the centrifugal component of the overall pressure drop increases with increasing Ω. 20 The power output per channel (W·) versus Ω curves (Figure 12), for each fixed value of Nnozzle, are of the shape of an inverted bucket. The existence of the optimum values of Ω for maximum W· can be explained from a simple theory.…”

Section: Implications Of the Nozzle–rotor Interaction On The Turbine mentioning

confidence: 99%

“…is described in McGarey and Monson. 18 Previous theoretical studies 8,[19][20][21][22][23][24] considered that the flow field within the narrow inter-disc spacing of a Tesla disc turbine is axisymmetric which may be realized either by increasing the number of inlet nozzles or by using a plenum chamber arrangement at the inlet of the rotor. The assumption, axisymmetry, makes it possible to achieve simplified theoretical models or less-expensive computational solutions.…”

Section: Introductionmentioning

confidence: 99%

“…In our previous theoretical studies and computational investigations, 2,19,20,23,24,37 we dealt with Tesla turbines under axisymmetric inflow condition. Theoretical work of other researchers also assumed axisymmetric inflow condition.…”

Section: Introductionmentioning

confidence: 99%

“…The present paper shows how the results of nonaxisymmetric simulations approach those of axisymmetric analysis as the number of discrete inflows is progressively increased, and establishes an important new conclusion that in order to achieve the best possible efficiency of the Tesla disc turbine it is necessary to achieve axisymmetric inflow to the rotor, thus retaining the usefulness of the physical understanding developed in our previous axisymmetric studies. 2,19,20,23,24,37 The complex interaction of the discrete multiple inflows within the small radial clearance space between the shroud and the rotor, the interesting spatial evolution during the subsequent flow through the rotor-rotor cavity, the attainment of a nearly axisymmetric distribution towards the outlet, and the critical role of axisymmetry on the performance of a Tesla turbine have been investigated in this paper. We examine the effects of the number of nozzles N nozzle , the rotational speed of the discs (), the radial clearance between the rotor and the shroud (Á rc ), the finite disc thickness (d t ), the shape of the disc edge, and the partial admission on the fluid dynamics and Figure 2.…”

Section: Introductionmentioning

confidence: 99%

Figure 2.Results obtained for a Tesla turbine operated under an axisymmetric inflow condition, and their comparison and validation: (a) power output predicted by the analytical model 23 versus the power output found in the experiment 17 with a 9-disc-rotor; (b) a comparison of power output/channel: CFD simulations 2 versus the analytical model, 23 (c) a comparison of pressure on the middle ( z -) plane of an inter-disc-spacing: CFD simulations 37 versus the analytical model, 23 (d) a comparison of pathlines on the middle ( z -) plane of an inter-disc-spacing: CFD simulations 37 versus the analytical model. 23 (All results correspond to ri=0.025 m, ro=0.0132 m, dt/b=0, Δrc = 0 and air as working fluid.…”

Section: Introductionmentioning

confidence: 99%

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Inflow-rotor interaction in Tesla disc turbines: Effects of discrete inflows, finite disc thickness, and radial clearance on the fluid dynamics and performance of the turbine

Sengupta

Guha

2018

Proceedings of the Institution of Mechanical Engineers, Part A:

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The article establishes the physics of the complex interaction of discrete multiple inflows with the stationary shroud and the rotating channel of a Tesla disc turbine. Using a large number (150) of separate, fully three-dimensional computational fluid dynamic simulations, we demonstrate the (sometimes dramatic) role of four important input parameters, namely the number of nozzles (N nozzle ), rotational speed of the discs (), radial clearance between the rotor and the shroud (Á rc ), and disc thickness (d t ), in the fluid dynamics and performance of a Tesla turbine. An increase in N nozzle or Á rc assists in the attainment of axisymmetric condition at rotor inlet. influences significantly the distribution of radial velocity including the fundamental shape of its z-profile (parabolic, flat or W-shaped). The paper demonstrates the existence of an optimum Á rc for which the efficiency of the rotor () is maximized. Present computational fluid dynamics simulations for many combinations of N nozzle and establish that the versus curves, for each fixed value of N nozzle , are of the shape of an inverted bucket. With increasing N nozzle , the operable range of decreases, the buckets become more peaky and the maximum possible increases substantially (by a factor of 2 in the example calculation shown). The present systematic work thus demonstrates quantitatively, for the first time, that an axisymmetric rotor inflow condition represents the best possible design for the rotor. It is further shown that, as the disc thickness is increased, the efficiency may decrease substantially (even dramatically) and its maxima occur at lower rotational speeds. Chamfering of the disc edge or partial admission decreases the turbine efficiency. Thus, small disc thickness, flat disc edge, full nozzle opening, optimum radial clearance, and inlet condition as close to axisymmetry as is possible are recommended for the design of an efficient Tesla disc turbine.

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