Performance of Supercritical CO2 Dry Gas Seals Near the Critical Point

Zakariya, Mohd Fairuz; Jahn, Ingo

doi:10.1115/gt2016-56537

Cited by 12 publications

(18 citation statements)

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“…Thus, it does not capture non-traditional velocity profiles that arise between the rotor and stator as a result of large centrifugal and inertial forces caused by the increased gas density [20,21,76] and real gas effect such as supercritical CO2. To date, the design guideline for the dry gas seal operating with ideal gas, are well established.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, these deviations are more significant for the supercritical CO2 ( Figure 3.14) as the operating gap decreases where the centrifugal effect is much stronger due to the higher density of the real gas effect [20,21]. The centrifugal effect will be discussed further in Chapter 4.…”

Section: Near Wall Treatmentmentioning

confidence: 99%

“…profiles with the logarithmic law is increasingly larger as the operating gap decreases. This deviationis attributed to the higher centrifugal effect due to higher density at the lower operating gap [20,21]. This centrifugal force acts radially in the opposite direction (i.e.…”

Section: Near Wall Treatmentmentioning

confidence: 99%

“…The isothermal temperature boundary condition is employed along the rotor and stator, with the assumption that rotor and stator size of the present geometry are highly conductive and thus the generated friction heat is transferred out quickly so that the wall temperatures remain constant, a valid assumption as assumed by previous work [20]. In addition, the isothermal assumption is only applied in Chapter 4 with the intention to study the real gas effect on the performance of the supercritical CO2 dry gas seal using the geometry from the previous work and air as a comparison.…”

Section: Boundary and Operating Conditionsmentioning

confidence: 99%

“…Using a more complex dry gas seals reduce the performances loss and increase the power cycle efficiency due to leakage [13]. Therefore dry gas seal is the preferred choice for supercritical CO2 power cycle applications when the technology is ready [13,20,21]. Cycle efficiency impact of two labyrinth end seals for a utility-scale supercritical CO2 turbine and desired dry gas seal leakage and expected efficiency [18].…”

Section: Why Dry Gas Seal?mentioning

confidence: 99%

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Simulation and development of dry gas seal for supercritical CO2 carbon dioxide

Zakariya¹

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The supercritical CO 2 closed loop Brayton cycle operates at high pressure to achieve higher energy conversion efficiency. One of the important components in turbomachinery of the power cycle plant is the dry gas seals. Dry gas seals are gas-lubricated, mechanical, non-contacting, end-face seals, consisting of a mating (rotating) ring and a primary (stationary) ring. Low leakage dry gas seals are considered as a key enabling technology for achieving the improved thermodynamic cycle efficiency in the supercritical CO 2 power cycle. Alternate seal types, for example, labyrinth seals, suffers from high leakage. Even so there is a growing interest and importance of applying the small length scale dry gas seal in the small to medium scale supercritical closed loop Brayton cycle (1-20 MWe), there are still uncertainties for their operation at supercritical CO 2 conditions. These include the real gas effects near the critical points and the methods of minimizing the deformation of the supercritical CO 2 dry gas seal. In the supercritical region in the vicinity of the critical point (304 K, 7.4 MPa), CO 2 behaves as a real-gas, exhibiting significant and abrupt nonlinear changes in fluid and transport properties and high densities.Comprehensive analysis is performed to simulate the supercritical CO 2 dry gas seal. First, an isothermal simulation assuming rigid sealing ring walls in the gas film is performed using ANSYS Fluent to study the influences of real gas effect on performances of the dry gas seal. Then, conjugate heat transfer simulation is used to optimize the face geometry for a small to median scale supercritical closed loop Brayton cycle (1-20 MWe) using ANSYS Fluent. Finally, the pressure and the thermal outputs from the conjugate heat transfer analysis are used as boundary conditions for one way coupling fluid-structurethermal simulations using ANSYS Static Structural to study the effect of deformation of the sealing rings under applied pressure-loads, thermal-loads, and centrifugal effect.Finding from the simulation results shows, close to critical point the real gas effect is significant, whereas far from the critical point the supercritical fluid resembles an ideal gas. The centrifugal effect is enhanced by the higher density due to the real gas effects, causing a reduction of average pressure in the dam region hence reduces the opening force, and seal leakage.Increasing the groove radius decreases the opening force whereas increasing the spiral angle, increases the opening force. However, the variation is small for all tested cases studies with variation up to 6%. Increasing the groove radius decreases the leakage rate whereas increasing the spiral angle, increases the leakage rate. The variation in changing groove radius is more significant than the spiral angles. The variation in leakage iii is up to 29.2% for all tested cases. In term of the film stiffness, there is no clear pattern when changing the groove radius but the impact of the spiral angle is significant, up to 46.6% for all tested c...

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Section: Discussionmentioning

confidence: 99%

Section: Near Wall Treatmentmentioning

confidence: 99%

Section: Near Wall Treatmentmentioning

confidence: 99%

Section: Boundary and Operating Conditionsmentioning

confidence: 99%