Theoretical and experimental investigations on the radial and axial leakages within a rotary vane expander

Vodička, Vãclav; Novotny, Vaclav; Zeleny, Zbynek; Mascuch, Jakub; Kolovratník, Michal

doi:10.1016/j.energy.2019.116097

Cited by 28 publications

(3 citation statements)

References 19 publications

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“…Fig. 17 and 18 shows the structure of the expander and leakage paths [75]. There are four major leakage paths: leakage into the following chamberaround vane and rotor and across the vane tip (A2); leakage into the leading chamberaround vane and rotor discs (A3); leakage behind the rotor disc (A4) and leakage through the seal arc (A6).…”

Section: Vane Expandermentioning

confidence: 99%

A comprehensive review of micro-scale expanders for carbon dioxide related power and refrigeration cycles

Tian

Pekris

2022

Applied Thermal Engineering

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Section: Vane Expandermentioning

confidence: 99%

A comprehensive review of micro-scale expanders for carbon dioxide related power and refrigeration cycles

Tian

Pekris

2022

Applied Thermal Engineering

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“…Moreover, they are characterized by simple manufacture and lower cost [22]. Nevertheless, volumetric losses are recognized as the main source of efficiency penalization for this device [23,24].…”

Section: Introductionmentioning

confidence: 99%

Development of Dual Intake Port Technology in ORC-Based Power Unit Driven by Solar-Assisted Reservoir

Fatigati,

Cipollone

2024

Energies

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The ORC-based micro-cogeneration systems exploiting a solar source to generate electricity and domestic hot water (DHW) simultaneously are a promising solution to reduce CO2 emissions in the residential sector. In recent years, a huge amount of attention was focused on the development of a technological solution allowing improved performance of solar ORC-based systems frequently working under off-design conditions due to the intermittence of the solar source availability and to the variability in domestic hot water demand. The optimization efforts are focused on the improvement of component technology and plant architecture. The expander is retained as the key component of such micro-cogeneration units. Generally, volumetric machines are adopted thanks to their better capability to deal with severe off-design conditions. Among the volumetric expanders, scroll machines are one of the best candidates thanks to their reliability and to their flexibility in managing two-phase working fluid. Their good efficiency adds further interest to place them among the best candidate machines to be considered. Nevertheless, similarly to other volumetric expanders, an additional research effort is needed toward efficiency improvement. The fixed built-in volume ratio, in fact, could produce an unsteady under- or over-expansion during vane filling and emptying, mainly when the operating conditions depart from the designed ones. To overcome this phenomenon, a dual intake port (DIP) technology was also introduced for the scroll expander. Such technology allows widening the angular extension of the intake phase, thus adapting the ratio between the intake and exhaust volume (so called built-in volume ratio) to the operating condition. Moreover, DIP technology allows increasing the permeability of the machine, ensuring a resulting higher mass flow rate for a given pressure difference at the expander side. On the other hand, for a given mass flow rate, the expander intake pressure diminishes with a positive benefit on scroll efficiency. DIP benefits were already proven experimentally and theoretically in previous works by the authors for Sliding Rotary Vane Expanders (SVRE). In the present paper, the impact of the DIP technology was assessed in a solar-assisted ORC-based micro-cogeneration system operating with scroll expanders and being characterized by reduced power (hundreds of W). It was found that the DIP Scroll allows elaboration of a 32% higher mass flow rate for a given pressure difference between intake and expander sides for the application at hand. This leads to an average power increase of 10% and to an improvement of up to 5% of the expander mechanical efficiency. Such results are particularly interesting for micro-cogeneration ORC-based units that are solar-assisted. Indeed, the high variability of hot source and DHW demand makes the operation of the DIP expander at a wide range of operating conditions. The experimental activity conducted confirms the suitability of the DIP expander to exploit as much as possible the thermal power available from a hot source even when at variable temperatures during operation.

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“…Vodicka et al [18] conducted a theoretical and experimental study of the effect of various leakages on the operating efficiency of a rotary vane expander. A novel experimental method for axial and radial clearance adjustment has been developed.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigations on Leakages in Positive Displacement Machines

Patel

Lakhera

2021

International Journal of Rotating Machinery

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The clearance gaps in positive displacement machines such as compressors, pumps, expanders, and turbines are critical for their performance and reliability. The leakage flow through these clearances influences the volumetric and adiabatic efficiencies of the machines. The extent of the leakage flow depends on the size and shape of clearance paths and pressure differences across these paths. Usually, the mass flow through the gaps is estimated using the isentropic nozzle equation with the flow coefficients applied to correct for the real flow conditions. However, the flow coefficients applied generally do not take into account the shape and size of these leakage paths. For that reason, a proper understanding of the relationship between flow coefficients and shape parameters is crucial for an accurate prediction of leakage flows. The present study investigates the influence of the various dimensionless parameters such as Reynolds number, Mach number, and pressure ratio on the flow coefficients for circular and rectangular clearance shapes. The flow coefficients are determined by comparing the experimental values obtained in an experimental test rig and the flow rates obtained from the isentropic nozzle equation. It is observed that in the case of circular clearances, the mean deviation of the experimental leakage results (in comparison to the analytical results using isotropic nozzle equations) is +9.1%, which is significantly lower than the mean deviation (+20.5%) in the case of rectangular clearance leakages. The study indicates that the isentropic nozzle equation method is more suitable for predicting the leakages through the circular clearances and needs modifications for consideration of the rectangular clearances. Using regression analysis, empirical correlations are developed to predict the flow coefficient in terms of Reynolds number, Mach number, pressure ratio, aspect ratio, and β ratio, which are found to match within ±6.4 percent of the numerical results for the rectangular clearance and within the range of -3.6 percent to +5.1 percent of the numerical result for the circular clearance. The empirical relationships presented in this study can be extended to evaluate the flow coefficients in a positive displacement machine.

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Theoretical and experimental investigations on the radial and axial leakages within a rotary vane expander

Cited by 28 publications

References 19 publications

A comprehensive review of micro-scale expanders for carbon dioxide related power and refrigeration cycles

A comprehensive review of micro-scale expanders for carbon dioxide related power and refrigeration cycles

Development of Dual Intake Port Technology in ORC-Based Power Unit Driven by Solar-Assisted Reservoir

Experimental Investigations on Leakages in Positive Displacement Machines

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