Radial Inflow Research Articles

The urban effects on the planetary boundary layer wind structures of typhoon Lekima (2019)

The urban effects on the planetary boundary layer (PBL) wind structures of landfalling tropical cyclones (TCs) have rarely been explored. In this study, numerical simulations for typhoon Lekima (2019), with and without multilayer building effect parameterization (BEP) and urban surfaces, were executed to investigate the urban effects on TC PBL wind structures. Validations against observations demonstrate that the simulation incorporating BEP and urban surface more accurately replicates the track, intensity and 10-m wind field of Lekima (2019). Based on the comparison between the simulations with and without urban surface, urban effects were analyzed, and the possible mechanisms were examined from the perspective of turbulent transport. Results show that urban surfaces have a deceleration effect on TC wind fields overall. This deceleration effect is most pronounced near the surface and decreases with height under 1 km above ground level. Urban surfaces reduce tangential winds and radial inflow in the near-surface layer, leading to a slight decrease in TC intensity. This is primarily attributed to the enhanced downward transfer of tangential momentum and upward transfer of radial momentum within the PBL, which results in larger magnitudes of negative tangential wind tendencies and positive radial wind tendencies induced by the divergence of subgrid-scale (SGS) momentum fluxes. Additionally, stronger tangential winds and radial outflow above the elevated PBL height correspond well to the increased tangential and radial wind tendencies in nearby areas. The analysis illustrates that turbulent transport provides insights into how urban surfaces affect the PBL wind structures of TCs.

Flow mechanism and back gap windage loss of a sCO2 radial inflow turbine with impeller scallops

Flow mechanism and back gap windage loss of a sCO2 radial inflow turbine with impeller scallops

Distribution of flow characteristics and productivity evaluation of herringbone wells in bottom water reservoirs

Abstract With the characteristics of large drainage area and low drilling cost, the herringbone wells have become an important way to increase the well production, delay the coning and ridge of bottom water and improve the development effect. Due to the complexity of the herringbone wells flow characteristics, results that exists certain gap between the current production prediction and the actual production, so it is of great significance to study the flow and productivity of herringbone wells. In this paper, taking bottom-water reservoir as the research object, considering the interference between branch wellbore and perforations, analysis the flow characteristics and the productivity sensitivity factors of herringbone wells. The results show that the transient flow time in the reservoir is short, the closer to the wellbore, the greater the pressure changes. With the increases of the branches number, branches length and branch angle, the per unit length of the wellbore radial inflow decreases, and the decrease slows down after exceeding 3 branches. In the high anisotropy reservoirs, the phase angle has greater impact on the productivity of the herringbone well when the perforation density is low, at 180°, phase angle is best; when the perforation density exceeds 16 shots/m, the increase of productivity degree decreases. This study provides important guiding significance for the actual application in oil fields to optimizing the herringbone wells shape, rational production allocation, specifying reasonable work systems and enhance oil recovery in the bottom water reservoirs.

Comprehensive Comparison of Seven Widely-Used Planetary Boundary Layer Parameterizations in Typhoon Mangkhut Intensification Simulation

Numerical experiments using the WRF model were conducted to analyze the sensitivity of Typhoon Mangkhut intensification simulations to seven widely used planetary boundary layer (PBL) parameterization schemes, including YSU, MYJ, QNSE, MYNN2, MYNN3, ACM2, and BouLac. The results showed that all simulations generally reproduced the tropical cyclone (TC) track and intensity, with YSU, QNSE, and BouLac schemes better capturing intensification processes and closely matching observed TC intensity. In terms of surface layer parameterization, the QNSE scheme produced the highest Ck/Cd ratio, resulting in stronger TC intensity based on Emanuel’s potential intensity theory. In terms of PBL parameterization, the YSU and BouLac schemes, with the same revised MM5 surface layer scheme, simulated weaker turbulent diffusivity Km and shallower mixing height, leading to stronger TC intensity. During the intensification period, the BouLac, YSU, and QNSE PBL schemes exhibited stronger tangential wind, radial inflow within the boundary layer, and updraft around the eye wall, consistent with TC intensity results. Both PBL and surface layer parameterization significantly influenced simulated TC intensity. The QNSE scheme, with the largest Ck/Cd ratio, and the YSU and BouLac schemes, with weaker turbulent diffusivity, generated stronger radial inflow, updraft, and warm core structures, contributing to higher storm intensity.

Effects of Surface Layer Physics Schemes on the Simulated Intensity and Structure of Typhoon Rai (2021)

The influences of surface layer (SL) physics schemes on the simulated intensity and structure of Typhoon Rai (2021) are investigated using the WRF model. Numerical experiments using different SL physics schemes—revised MM5 scheme (MM5), Eta similarity scheme (CTL), and Mellor–Yamada–Nakanishi–Niino scheme (MYNN)—are conducted. The results show that the intensity forecast of Typhoon Rai is largely influenced by SL physics schemes, while its track forecast is not significantly affected. All three experiments can successfully capture the movement of Rai, while CTL provides better intensity simulation compared to the other two experiments. The higher ratio of enthalpy exchange coefficient to drag coefficient (CK/CD) in CTL than MM5 and MYNN leads to significantly increased surface enthalpy fluxes, which are crucial for the typhoon intensification of the former. To explore the influence of SL physics on the structural evolution of the typhoon, the azimuthal-mean angular momentum (AM) budget is utilized. The results indicate that asymmetric eddy terms may also largely contribute to the AM tendencies, which are relatively more comparable in the weaker TC for MM5, compared to the stronger TC with the dominant symmetric mean terms for CTL. Furthermore, the extended Sawyer–Eliassen (SE) equation is solved to quantify the transverse circulations of the typhoon induced by different forcing sources for CTL and MM5. The SE solution indicates that the transverse circulation above and within the boundary layer is predominantly induced by diabatic heating and turbulent friction, respectively, for both CTL and MM5, while all other physical forcing terms are relatively insignificant for the induced transverse circulation for CTL, except for the large contribution from the eddy forcing in the upper-tropospheric outflow for MM5. With the stronger connective heating in the eyewall and boundary-layer radial inflow, the linear SE analysis agrees much better with the nonlinear simulation for CTL than MM5.

Numerical Investigation of Track and Intensity Evolution of Typhoon Doksuri (2023)

This study utilized the WRF model to investigate the track evolution and rapid intensification (RI) of Typhoon Doksuri (2023) as it moved across the Luzon Strait and through the South China Sea (SCS). The simulation results indicate that Doksuri has a smaller track sensitivity to the use of different physics schemes, while having a greater intensity sensitivity. Sensitivity numerical experiments with different physics schemes can well capture its northwestward movement in the first two days, but they predict less westward track deflection as the typhoon moves across the Luzon Strait and through the SCS. Moreover, all the experiments successfully simulated Doksuri’s RI, albeit with quite different rates and a time lag of 12 h. Among different combinations of physics schemes, there exists an optimal set of cumulus parameterization and cloud microphysics schemes for track and intensity predictions. Doksuri’s track changes as the typhoon moved across the Luzon Strait and through the SCS were influenced by the topographic effects of the terrain of the Philippines and Taiwan, to different extents. The track changes of Doksuri are explained by the wavenumber-one potential vorticity (PV) tendency budget from different physical processes, highlighting that the horizontal PV advection dominates the PV tendency throughout most of the simulation time due to the offset of vertical PV advection and differential diabatic heating. In addition, this study applies the extended Sawyer–Eliassen (SE) equation to compare the transverse circulations of the typhoon induced by various forcing sources. The SE solution indicates that radial inflow was largely driven in the lower-tropospheric vortex by strong diabatic heating, while being significantly enhanced in the lower boundary layer due to turbulent friction. All other physical forcing terms were relatively insignificant for the induced transverse circulation. The coordinated radial inflow at low levels may have led to the eyewall development in unbalanced dynamics. Intense diabatic heating thus was vital to the severe RI of Doksuri under a weak vertical wind shear.

Understanding the initial conditions contributing to the rapid intensification of typhoons through ensemble sensitivity analysis

While steady improvements have been achieved for the track forecasts of typhoons, there has been a lack of improvement for intensity forecasts. One challenge for intensity forecasts is to capture the rapid intensification (RI), whose nonlinear characteristics impose great difficulties for numerical models. The ensemble sensitivity analysis (ESA) method is used here to analyze the initial conditions that contribute to typhoon intensity forecasts, especially with RI. Six RI processes from five typhoons (Chaba, Haima, Meranti, Sarika, and Songda) in 2016, are applied with ESA, which also gives a composite initial condition that favors subsequent RI. Results from individual cases have generally similar patterns of ESA, but with different magnitudes, when various cumulus parameterization schemes are applied. To draw the initial conditions with statistical significance, sample-mean azimuthal components of ESA are obtained. Results of the composite sensitivity show that typhoons that experience RI in 24 h favor enhanced primary circulation from low to high levels, intensified secondary circulation with increased radial inflow at lower levels and increased radial outflow at upper levels, a prominent warm core at around 300 hPa, and increased humidity at low levels. As the forecast lead time increases, the patterns of ESA are retained, while the sensitivity magnitudes decay. Given the general and quantitative composite sensitivity along with associated uncertainties for different cumulus parameterization schemes, appropriate sampling of the composite sensitivity in numerical models could be beneficial to capturing the RI and improving the forecasting of typhoon intensity.摘要针对台风强度特别是快速增强 (RI) 的预报难点, 本文对2016年5个台风的6次RI过程应用集合敏感性分析 (ESA), 以分析有利于RI的初始条件. 对于不同的个例和积云参数化方案, ESA获得的有利于台风RI的集合敏感性相似但量级存在差异. 复合敏感性揭示了经历RI的台风所需的初始条件, 其有更强的主环流, 更显著的暖心及增加的低层湿度. ESA估计的集合敏感性随预报时长增加而减弱. 通过采样复合敏感性可有望改进集合初始条件及台风强度预报.

Numerical Investigation of Flow Structure and Pressure Drop Prediction for Radial Inflow between Co-Rotating Discs with Negative Effective Inlet Swirl Ratio

Abstract This paper presents a numerical simulation of the flow structure of radial inflow between co-rotating discs with a negative ceff (effective inlet swirl ratio), which may occur in a vortex reducer equipped with deswirl nozzles. When the value of ceff approaches zero, asymmetric flow structure is observed in the cavity, possibly as a result of the ‘Coanda effect’. Besides this, the flow structure inside the disc cavity at ceff < 0 can be divided into a source region, a sink region, an interior core region, and two Ekman layers, which is identical to the situation when 0 < ceff = 1. However, there exist two distinct patterns: the stagnation point on the disc and on the peripheral. According to a theoretical analysis, ceff = -1/8 is used to distinguish between these two patterns. Based on flow structure partitioning, a theoretical model for predicting the swirl ratio radial distribution and pressure drop in a disc cavity with ceff < 0 was established. The model employs the turbulent boundary layer integral method, and von Karman's assumption of velocity profile and wall shear stress for a free disc. The calculation results of the swirl ratio in the cavity are in good agreement with the CFD results except when the negative ceff approaches zero because of the deviation of the radial velocity profile from the ‘1/7’ power law. Furthermore, pressure drop prediction across the cavity by the model has been verified through comparison with public experimental results.

Influences of Background Rotation on Secondary Eyewall Formation of Tropical Cyclones in Idealized f‐Plane Simulations

AbstractThis study investigates the background rotational influences on the secondary eyewall formation (SEF) in tropical cyclones (TCs) in quiescent f‐plane environments. For given initial structures, simulated vortices tend to experience earlier SEF at lower latitudes. Yet the size of the secondary eyewall does not change monotonically with the latitudes. Specifically, ∼20°N provides the optimal amount of background rotation for the largest secondary eyewall size without considering other environmental forcings. Different background rotation rates affect SEF mainly by modulating the outer‐core convection as well as the wind structures. Specifically, the lower rotation rate causes more outer‐core surface fluxes, thus facilitating the outer rainbands (ORBs) at larger radii. Yet the secondary eyewall does not necessarily form at larger radii at lower latitudes since the transition from the ORBs to secondary eyewall is localized in a region of boundary layer (BL) convergence preceded by accelerated tangential winds. Budget analysis reveals that the differences in the acceleration of outer‐core tangential winds among vortices at different latitudes are dominated by the radial flux of absolute vorticity. Due to the non‐uniform influences of background rotation on the BL inflow and absolute vorticity, the most efficient spin‐up of outer‐core tangential winds is achieved at a medium latitude of 20°N, which leads up to SEF at the largest radii. By comparison, for TCs at lower (higher) latitudes, the lower outer‐core absolute vorticity (radial inflow) limits the acceleration of outer‐core tangential winds, thus placing SEF at smaller radii.

Investigation of the radial uniform and variable inflow profiles to improve production in the perforated horizontal wellbore

Investigation of the radial uniform and variable inflow profiles to improve production in the perforated horizontal wellbore

The Role of Turbulence in an Intense Tropical Cyclone: Momentum Diffusion, Eddy Viscosities, and Mixing Lengths

Abstract Improved representation of turbulent processes in numerical models of tropical cyclones (TCs) is expected to improve intensity forecasts. To this end, the authors use a large-eddy simulation (with 31-m horizontal grid spacing) of an idealized category 5 TC to understand the role of turbulent processes in the inner core of TCs and their role on the mean intensity. Azimuthally and temporally averaged budgets of the momentum fields show that TC turbulence acts to weaken the maximum tangential velocity, diminish the strength of radial inflow into the eye, and suppress the magnitude of the mean eyewall updraft. Turbulent flux divergences in both the vertical and radial directions are shown to influence the TC mean wind field, with the vertical being dominant in most of the inflowing boundary layer and the eyewall (analogous to traditional atmospheric boundary layer flows), while the radial becomes important only in the eyewall. The validity of the downgradient eddy viscosity hypothesis is largely confirmed for mean velocity fields, except in narrow regions which generally correspond to weak gradients of the mean fields, as well as a narrow region in the eye. This study also provides guidance for values of effective eddy viscosities and vertical mixing length in the most turbulent regions of intense TCs, which have rarely been measured observationally. A generalized formulation of effective eddy viscosity (including the Reynolds normal stresses) is presented. Significance Statement This study uses a turbulence-resolving simulation of a category 5 tropical cyclone to understand the role of turbulence in intense storms. Results show that turbulence clearly modulates storm structure and intensity. This study provides guidance for the values of turbulent quantities (which are usually parameterized in comparatively coarse operational TC forecast models) in scarcely observed regions of intense storms. Furthermore, a complete formulation of the effective eddy viscosities is proposed, incorporating contributions from typically ignored Reynolds normal stress terms.

Diagnosing Radial Ventilation in Dropsonde Observations of Hurricane Sam (2021)

Abstract This study presents a method to diagnose radial ventilation, the horizontal flux of relatively low-θe air into tropical cyclones, from dropsonde observations. We used this method to investigate ventilation changes over three consecutive sampling periods in Hurricane Sam (2021), which underwent substantial intensity changes over 3 days. During the first and last periods, coinciding with intensification, the ventilation was relatively small due to a lack of spatial correlation between radial flow and θe azimuthal asymmetries. During the second period, coinciding with weakening, the ventilation was relatively large. The increased ventilation was caused by greater shear associated with an upper-level trough, tilting the vortex, along with dry, low-θe air wrapping in upshear. The spatial correlation of the radial inflow and anomalously low-θe air resulted in large ventilation at mid- to upper levels. Additionally, at low to midlevels, there was evidence of mesoscale inflow of low-θe air in the stationary band complex. The location of these radial ventilation pathways and their effects on Sam’s intensity are consistent with previous idealized and real-case modeling studies. More generally, this method offers a way to monitor ventilation changes in tropical cyclones, particularly when there is full-troposphere sampling around and within a tropical cyclone’s core. Significance Statement Ventilation, the injection of relatively dry and/or cool air into a tropical cyclone, may weaken a storm. In contrast, the lack of ventilation is favorable for intensification. The purpose of this study is to present a method to diagnose ventilation using aircraft dropsonde observations. Using dropsonde observations collected in Hurricane Sam (2021), there was a period of increased lateral ventilation in two regions around the storm that coincided with when the storm rapidly weakened. The results suggest that monitoring ventilation from dropsonde observations, when available, may be useful for anticipating ventilation-induced intensity changes in tropical cyclones and further studying ventilation pathways.

Energy loss evaluation of a radial inflow turbine for organic Rankine cycle application using hierarchical entropy production method

To evaluate the location and main sources of energy loss in radial inflow turbines for organic Rankine cycle application, this study proposed a hierarchical entropy production method, which is superior to the traditional pressure drop method. The method includes three levels: local entropy production, split of turbine total entropy production, and split of component entropy production. The energy loss of the radial inflow turbine under design condition and different pressure ratios is presented. The results indicate that the high-entropy production zone is primarily located at the stator trailing edge and the rotor tip clearance. The proportion of turbulent entropy production and wall entropy production in the total energy loss of the turbine is about 77% and 20%, respectively. Among the components of the radial inflow turbine, the energy loss of the rotor and diffuser is the highest, accounting for 71.9% and 13.6% of the total entropy production of the turbine, respectively. However, the stator and rotor have higher volume average entropy generation rate and area average entropy generation rate. The high-entropy production region is mainly located in the stator outlet zone and the rotor tip zone. When the pressure ratio increases from 3 to 5, the turbine efficiency decreases by 13.44%. The pressure ratio has a significant effect on the turbulent entropy production of the rotor. This method can provide insight into the energy loss characteristics of radial inflow turbines for organic Rankine cycle applications.

Design and optimization of the radial inflow turbogenerator for organic Rankine cycle system based on the Genetic Algorithm

The backdrop of energy-saving and emission-reduction sets a higher demand for low-grade energy utilization which can be realized by Organic Rankine Cycle systems. A 50-kW radial inflow turbogenerator, the crucial heat conversion equipment, with aerostatic bearings for Organic Rankine Cycle system, is designed. It is optimized focusing on the performance of the turbogenerator which uses R245fa as the working fluid. The study employs a one-dimensional thermodynamic model, developed in MATLAB and bolstered by real-time data from Refprop, ensuring the model’s precision and dependability. On this basis, Genetic Algorithm is applied to optimize design parameters and significantly elevate the system’s efficiency, achieving circumferential efficiency of 85.29%. The turbogenerator demonstrates a rated bearing load capacity of 2.43 kN. The research delves into the influence of inlet temperature, inlet pressure, and rotational speed of turbogenerator on its performance. It reveals that an increase in both inlet temperature and inlet pressure lead to a decrease in isentropic efficiency and an increase in output power. The research also shows that an increase in the rotational speed contributes to increases in isentropic efficiency and output power.

Optimization of a radial inflow turbine rotor with splitter blades based on entropy production theory and artificial neural network

The radial inflow turbine is the core component of the organic Rankine cycle, and the application of splitter blades is an effective way to reduce its flow loss. It is helpful to study the energy loss characteristics of radial turbines with splitter blades and the optimal geometrical parameters of splitter blades for further improving their aerodynamic performance. In this paper, an optimization framework based on the combination of back-propagation neural network and non-dominated sorting genetic algorithm II is developed. Considering the turbine efficiency as the objective, the geometric parameters of splitter blades, including relative length of the blade, relative distance of the leading edge, circumferential offset, and outlet angle of the blade, are optimized. In addition, the entropy production method is used to locate and quantitatively evaluate the energy loss of the radial turbine with the optimal splitter blades. The results indicate that the genetic algorithm optimized back-propagation neural network model can accurately predict turbine efficiency with a maximum deviation of 2.47 %. In addition, the optimal geometrical parameters of the splitter blade are related to the turbine geometry. In this case, the optimal splitter blade has a relative blade length of 0.639, a relative leading edge distance of 0.3, a circumferential offset of 0.442, and an outlet angle of 38°. Compared with the original turbine, the efficiency of the radial turbine with optimal splitter blades increases by 4.65 %. The total entropy production of rotor and turbine is reduced by 33.3 % and 44.1 % respectively by the installation of optimal splitter blades. Compared with the case without splitter blades, the turbine with the optimal splitter blades can achieve higher efficiency at a flow rate 40 % higher than the design value, and it expands the efficient working range of the turbine by 60 %. This work can provide guidance for the optimization design of radial inflow turbines.

Auxiliary Heat System Design and Off-Design Performance Optimization of OTEC Radial Inflow Turbine

In this paper, solar energy is used as the auxiliary heat source of the ocean thermal energy radial inflow turbine, and the thermodynamic model of the circulation system is established. In addition, the ejector is introduced into the ocean thermal power generation system, and the process simulation is carried out using Aspen Plus V12. To address performance attenuation of the radial turbine under varying working conditions, shape optimization of a 30 kW OTEC radial turbine was conducted. Finally, the off-design performance variation in the radial inflow turbine is analyzed in the presence of a solar auxiliary heat source. The results show that the use of an auxiliary heat source can effectively improve the cycle efficiency of the system and is also conducive to the stable operation of the radial turbine. Under the condition of auxiliary heat source, the system cycle efficiency is increased by 2.269%.

Modeling and Control of an MR-Safe Pneumatic Radial Inflow Motor and Encoder (PRIME).

Magnetic resonance (MR) conditional actuators and encoders are the key components for MR-guided robotic systems. In this article, we present the modeling and control of our MR-safe pneumatic radial inflow motor and encoder. A comprehensive model is developed that considers the primary dynamic elements of the system, including: 1) motor dynamics, 2) pneumatic transmission line dynamics, and 3) valve dynamics. After model validation, we present a simplified third order model that facilitates design of a first order sliding mode controller (TO-SMC). Finally, the motor hardware is tested in a 7T MRI. No image distortion or artifacts were observed. We posit the MR-safe motor and dynamic model will lower the entry barriers for researchers interested in MR-guided robots and promote wider adoption of MR-guided robotic systems.

Energy loss evaluation in radical inflow turbine based on entropy production theory and orthogonal experiment method

The fluctuation of heat source conditions results in off-design operation of the radial inflow turbines (RIT) in the organic Rankine cycle. However, the flow loss characteristics of RIT under off-design conditions have not been completely revealed. The entropy production theory has the advantage of determining the quantity and location of energy dissipation, which is used to evaluate the energy loss of RIT under different conditions. In addition, the order of operating parameters on the RIT energy loss is determined by the orthogonal experimental method. The results show that each entropy production term and the entropy production of different components increase with the increase in the inlet pressure and inlet temperature, while they decrease with the increase in the outlet pressure of the RIT. Under different operating conditions, the turbulent dissipation and wall dissipation are the main cause of RIT energy loss, which are closely related to vortices and high velocity gradients in the flow field. The rotor and diffuser contribute the main energy loss of RIT. However, the volume-average entropy production and area-average entropy production of the stator and rotor are higher than those of other components. In addition, the wall shear is the main cause of the stator energy loss, while the turbulent dissipation dominants the rotor energy loss. The outlet pressure has the greatest impact on the turbulent entropy production and wall dissipation.

Optimization design of radial inflow turbine combined with mean-line model and CFD analysis for geothermal power generation

It is a considerable challenge to determine the key parameters affecting the efficiency and propose an accurate loss prediction model for radial flow turbine design. In current investigation, a one-dimensional mean-line model combined with particle swarm optimization algorithm and Kriging response surface surrogate model based on 3D numerical results were proposed to optimize radial flow turbines and evaluate performance. The loss model was carried out to analyze the relationship between geometric parameters, operating conditions and turbine performance. CFD numerical simulations were employed to revealed the mechanism of enhancing the turbine performance. The total-static efficiency was increased from 88.5 % to 91.7 %, and the clearance loss and passage loss were reduced by 18.4 % and 35.8 %, respectively,by optimized design. It is attributed to mitigate the curvature-induced boundary layer separation and vortex at the outlet, which reduces the secondary flow losses.The correlation between the predicted values of the Kriging response surface and the numerical results was up to 98.3 %. The results showed that the angle of attack was in the range of -10-0°, the blade has less influence on the flow loss. The current study effectively combined the flow path structure parameters and flow characteristics to realize the efficient optimization of ORC turbine.

Loss Analysis in Radial Inflow Turbines for Supercritical CO2 Mixtures

Abstract Recent studies suggest that CO2 mixtures can reduce the costs of concentrated solar power plants. Radial inflow turbines (RIT) are considered suitable for small to medium-sized CO2 power plants (100 kW to 10 MW) due to aerodynamic and cost factors. This paper quantifies the impact of CO2 doping on RIT design by comparing 1D mean-line designs and aerodynamic losses of pure CO2 RITs with three CO2 mixtures: titanium tetrachloride (TiCl4), sulfur dioxide (SO2), and hexafluorobenzene (C6F6). Results show that turbine designs share similar rotor shapes and velocity diagrams for all working fluids. However, factors like clearance-to-blade height ratio, turbine pressure ratio, and fluid viscosity cause differences in turbine efficiency. When normalized for these factors, differences in total-to-static efficiency become less than 0.1%. However, imposing rotational speed limits reveals greater differences in turbine designs and efficiencies. The imposition of rotational speed limits reduces total-to-static efficiency across all fluids, with a maximum 15% reduction in 0.1 MW CO2 compared to a 3% reduction in CO2/TiCl4 turbines of the same power. Among the studied mixtures, CO2/TiCl4 turbines achieve the highest efficiency, followed by CO2/C6F6 and CO2/SO2. For example, 100 kW turbines achieve total-to-static efficiencies of 80.0%, 77.4%, 78.1%, and 75.5% for CO2/TiCl4, CO2/C6F6, CO2/SO2, and pure CO2, respectively. In 10 MW turbines, efficiencies are 87.8%, 87.3%, 87.5%, and 87.2% in the same order.