Characterization of Nonequilibrium Condensation of Supercritical Carbon Dioxide in a de Laval Nozzle

Abstract

Carbon capture and storage could significantly reduce carbon dioxide (CO2) emissions. One of the major limitations of this technology is the energy penalty for the compression of CO2 to supercritical conditions. To reduce the power requirements, supercritical carbon dioxide compressors must operate near saturation where phase change effects are important. Nonequilibrium condensation can occur at the leading edge of the compressor, causing performance and stability issues. The characterization of the fluid at these conditions is vital to enable advanced compressor designs at enhanced efficiency levels but the analysis is challenging due to the lack of data on metastable fluid properties. In this paper, we assess the behavior and nucleation characteristics of high-pressure subcooled CO2 during the expansion in a de Laval nozzle. The assessment is conducted with numerical calculations and corroborated by experimental measurements. The Wilson line is determined via optical measurements in the range of 41–82 bar. The state of the metastable fluid is characterized through pressure and density measurements, with the latter obtained in a first-of-its-kind laser interferometry setup. The inlet conditions of the nozzle are moved close to the critical point to allow for reduced margins to condensation. The analysis suggests that direct extrapolation using the Span and Wagner equation of state (S–W EOS) model yields results within 2% of the experimental data. The results are applied to define inlet conditions for a supercritical carbon dioxide compressor. Full-scale compressor experiments demonstrate that the reduced inlet temperature can decrease the shaft power input by 16%.

Carbon dioxide and propane nucleation: the emergence of a nucleation barrier

“…Note that we cannot find overlap with their conditions because of experimental limitations in t and p F . CO 2 nucleation was also studied by Duff 72 in the temperature range between 160 K and 190 K and by Lettieri et al 73 in the range between 260 K and 300 K. These measurements lie far outside our experimental conditions and a comparison is thus not possible. For further analysis, we turn to comparisons with results from nucleation theories.…”

A real gas-based throughflow method for the analysis of SCO2 centrifugal compressors

“…Detailed geometric dimensions of the nozzle can be found in Lettieri et al. 25 There are five groups of experiments: the inlet temperatures are around 310 K, which is slightly above the CP. The inlet pressures range from 59 to 84 bar, indicating that the inlet conditions are gradually approaching the CP from case 1 to case 5.…”

A Discrete Adjoint Method for Two-Phase Condensing Flows Applied to the Shape Optimization of Turbine Cascades

“…Coefficient. Using first principles, for a fixed control volume in which the condensing vapor flows through, the entropy generation Δṡ due to loss mechanisms can be computed as Δs = s out − s in (18) in which…”

“…Specifically, the focus here is on vapor flows condensing at non-equilibrium thermodynamic conditions [16]. This type of flows occur, among others, in the last stages of steam turbines [17] or in centrifugal compressors operating with supercritical carbon dioxide [18] and lead to aero-mechanical performance degradation. For example, droplet formation is a highly irreversible process leading to a work reduction of up to 1-2% for each stage of large steam turbines in which condensation occurs [19].…”

“…Fig 18. Dykas cascade: U 2phase,4 distribution for the optimized profile in case the objective is the minimization of the thermodynamic losses…”