Design Of Radial Turbine Research Articles

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.

Efficiency Improvement of Small Cryogenic Helium Turbo-expanders in TIPC

An experimental helium liquefier/refrigerator, using ultra high speed cryogenic turbo-expanders is designed and developed in Technical Institute of Physics and Chemistry (TIPC), and liquefaction rate of around 42 L/hr and refrigeration capacity of around 130 W @ 4.5 K is achieved. The turbo-expander constitutes the most critical component of a helium liquefier/refrigerator causing that the turbine efficiency has a great influence on the performance of the whole cryogenic process plant. Inlet Flow Radial (IFR) turbine design is dictated by criteria like velocity ratios. For small flow rate plants the size of the turbine impeller needs to be reduced. In order to reach a high efficiency, the rotational speed must be increased to complete a large specific enthalpy drop. The present article describes the latest technical developments at TIPC, including results obtained during field trials with the TIPC helium liquefier and refrigerator. The motivation of these developments is to improve the efficiency of the machines, and also to widen the range of operation.

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.

A comparative study of mean-line models based on enthalpy loss and analysis of a cavity-structured radial turbine for solar hybrid microturbine applications

Lightweight components are essential for the future of the energy and aerospace fields. This paper presents an innovative radial turbine design that utilizes a cavity structure on the rotor for solar hybrid microturbines. The performance of the cavity-structured radial turbine is studied using mean-line models, computational fluid dynamics (CFD), and finite element analysis (FEA) simulations. The radial turbine is compared using air and supercritical carbon dioxide (sCO2) as the working fluid. The mean-line models based on enthalpy losses from recent literature are validated using commercial code Rital and CFD results. The impact of the isentropic velocity ratio (νs) and absolute flow angle at the rotor inlet (α1) on the optimum design for the rotor radial turbine is also demonstrated. A comparative loss enthalpy breakdown on the rotor is examined, such as incidence loss, passage loss, trailing edge loss, clearance loss, exit loss, and windage loss. The results show that the recent mean-line models based on enthalpy losses can accurately estimate the stage efficiency for both air and sCO2 turbines. By comparing the simulation results obtained from 3D-CFD and mean-line models, the efficiency prediction deviation is within an acceptable range of tolerance for both turbines when comparing the results obtained from 3D-CFD and mean-line models. The FE analysis reveals that the maximum stress decreased significantly for the air and sCO2 turbine after the rotor blade was added using the cavity structure inside. The maximum stress value on the rotor with the cavity structure design is still below the yield strength of the material limits. Furthermore, after the variations of the cavity structure design were added to the rotor blade of both turbines, the results were promising when the dangerous resonance at below 4EO (Engine Order) was minimized. The results of this study provide a promising direction for the development of high-efficiency and lightweight turbines in the energy and aerospace fields.

A Review on the Preliminary Design of Axial and Radial Turbines for Small-Scale Organic Rankine Cycle

Organic Rankine cycle (ORC) is an effective technology to harness low-grade energy. Turbine, as a key component of ORC, takes advantages of its high efficiency and compact size compared with other expanders. Currently, developing suitable turbines with a high performance and a low cost is one of the bottlenecks for wide applications of various ORCs. In this context, technical progress on radial inflow turbines (RITs), axial turbines (ATs), and radial outflow turbines (ROTs) is introduced, and loss models used in the preliminary design are compared, especially for small-scale ORCs. RIT is recommended for medium and small ORCs with an expansion pressure ratio of <10. The power outs and rotational speeds of the designed RITs spanned the ranges of 9.3–684 kW and 3000–114,000 r/min with an efficiency of 56.1–91.75%. In comparison, the power outputs and speeds of ATs were 3–2446 kW and 3000–91,800 r/min with an efficiency of 63–89.1%. AT is suitable for large-scale ORCs with a power output of greater than hundreds of kW. However, AT with impulse stages is feasible for small-scale ORCs when the pressure ratio is high, and the mass flow rate is small. The power outputs of the designed ROTs were relatively small, at 10–400 kW with a speed of 7200–42,700 r/min and an efficiency of 68.7–85%. For organic working fluids with a large expansion pressure ratio, ROT might be employed. Conventional mean-line models may neglect the effects of supersonic flow, which will be encountered in many ORC turbines. Therefore, adequate models for supersonic expansion loss and shock loss need to be added. Meanwhile, a proper multivariable optimization algorithm such as a gradient-based or stochastic search method should be selected. Finally, the challenges and potential research directions are discussed. The outcomes can provide some insights for the development of ORC turbines and the optimization of ORC systems.

Design and numerical simulation of radial inflow turbine of the regenerative Brayton cycle using supercritical carbon dioxide

Carbon dioxide is abundant on earth and has a high density in the supercritical phase so that the turbomachinery size can be small. Thus the turbine, compressor, and alternator can be made compact. The advantage of the Brayton Cycle is using a regenerator on the exit side of the turbine for heat recovery. The S–CO2 radial inflow turbine is suitable for systems ranging from 0.1 MW to 25 MW. Turbomachinery can have high power densities for smaller-scale energy generation because to the low flow rates of the high-density working fluids. Small-modular heliostat fields, thermal storage, and radial inflow turbines with a power output of around 1 MW are appropriate for solar base-load energy systems in rural and isolated places, particularly in Indonesia. However, the experimental research is costly, time-consuming, and may pose security threats, whereas CFD modeling improves the design process and greatly saves time and money.This study aims to design a radial inflow turbine for the Regenerative Brayton Cycle. The turbine has designed to work at 70,000 RPM with a net power target of 40 kW. Regenerative Brayton Cycle with supercritical carbon dioxide working fluid (S–CO2) designed for turbine inlet temperature is 800 K, the compressor inlet temperature is 320 K, and the pressure ratio in turbine 1.63. Based on the cycle's design, the turbine and compressor powers are 113.84 kW and 60.53 kW, respectively. The geometric design has been carried out with an approach by some of the literature related to this research. Computational Fluid Dynamics (CFD) simulations are then performed on the results of the design of the turbine. The CFD simulation results of the radial inflow turbine show that can produced is 113.28 kW, and the total to total turbine efficiency is 81.63% at 70,000 RPM and 2.0 kg/s. However, in this study the turbine's design is targeted in around 40 kW. So, according to CFD simulation results, the net power and the efficiency of the Brayton cycle generated is 53.75 kW and 18.74%, respectively.

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 1: Radial Turbine Modelling and Design

The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the energy of the exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered by means of a properly designed turbogenerator and employed for vehicle propulsion; previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% by employing a 20 kW turbine on a 100 HP rated power thermal unit. The innovative thermal unit here proposed is composed of a supercharged engine endowed with a properly designed turbogenerator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In these two parts, the realistic efficiency of the innovative thermal unit for hybrid vehicle is evaluated and compared to a traditional turbocharged engine. In Part 1, the authors present a model for the prediction of the efficiency of a dedicated radial turbine, based on a simple but effective mean-line approach; the same paper also reports a design algorithm, which, owing to some assumptions and approximations, allows a fast determination of the proper turbine geometry for a given design operating condition. It is worth pointing out that, being optimized for quasi-steady power production, the exhaust gas turbine considered is quite different from the ones commonly employed for turbocharging application; for this reason, and in consideration of the required power size, such a turbine is not available on the market, nor has its development been previously carried out in the scientific literature. In the Part 2 paper, a radial turbine geometry is defined for the thermal unit previously calculated, employing the design algorithm described in Part 1; the realistic energetic advantage that could be achieved by the implementation of the turbogenerator on a hybrid propulsion system is evaluated through the performance prediction model under the different operating conditions of the thermal unit. As an overall result, it was estimated that, compared to a reference traditional turbocharged engine, the turbocompound system could gain vehicle efficiency improvement between 3.1% and 17.9%, depending on the output power level, while an average efficiency increment of 10.9% was determined for the whole operating range.

Thermodynamic analysis of open-air Brayton cycle to predict radial turbine aerodynamic performance

• A novel radial turbine design approach based on blade loss coefficient correction. • A system-turbine coupled evaluation method for the open-air Brayton cycle. • Turbine rotational consideration in turbine performance prediction. • Optimization of correlative coefficients in turbine geometrical design. The separated performance evaluation of the system and turbine leads to low accuracy in overall system performance prediction for the open-air Brayton cycle. To achieve the coupling analysis of system and turbine performance prediction and improve the accuracy of parameters optimization, this paper focuses on the improvement of the system and turbine performance evaluation approach. An improved turbine design approach based on blade loss coefficient correction is proposed to promote accuracy in turbine design. Meanwhile, an improved system-turbine coupled evaluation method for the open-air Brayton cycle is established by coupling the system performance prediction with the improved turbine design approach. The overall system performance analysis of the open-air Brayton cycle is performed to present the superiorities of the improved system-turbine coupled evaluation method. Furthermore, the parameters optimization of turbine design is carried out with the system performance evaluation and the rotational speed consideration to obtain optimum turbine isentropic efficiency. The results indicate that the improved turbine design approach can significantly decrease the relative error of turbine isentropic efficiency in one-dimension design to less than 1.85%. The improved system-turbine coupled method can decrease the relative deviation by 12.96% in system thermal efficiency compared with the conventional approach. In addition, the higher residual velocity loss, the lower disk friction loss, and the higher blade velocity coefficient are caused by the higher turbine rotational speed. Ultimately, the maximum thermal efficiency of the open-air Brayton cycle is 40.35% and the corresponding optimum turbine isentropic efficiency is 89.14% under the given system conditions. It is of great significance for parameter setting and optimization for the open-air Brayton cycle, and offers the support for the energy sustainability utilization.

Preliminary Design of a Mini Gas Turbine via 1D Methodology

To address the increasing interest towards more environmentally friendly naval transportation and the introduction of IMO2020 restrictions on pollutant emissions onboard ships, the present work details the preliminary design of a mini gas turbine engine, i.e., a gas turbine engine with an output power up to 5 MW, for onboard energy generation. In comparison to conventional propulsion systems, gas turbine units benefit from known compactness, which can be further enhanced by employing single-stage uncooled radial machines, according to similar works in the field. As such, the present paper aims to set up a complete procedure that allows a reliable and fast (i.e., requiring a limited computational effort) preliminary design of one-stage centrifugal compressors and radial turbines operating at a high pressure ratio via the use of classical one-dimensional theory. The aerodynamic design outputs in terms of forces and torques are then used to perform a preliminary mechanical design of the shaft by means of a one-dimensional finite element model with commercial software to estimate the corresponding shaft line stress. Despite some necessary geometrical and modeling simplification of the design problem, which results in the unavailability of detailed information on individual components, the employed procedure nevertheless allows a comprehensive overview of the possibilities in terms of maximum machine performance achievable at an early design stage with the associated limited computational requirements. The design procedure and the geometry achieved for the application are presented along with aerodynamic and structural results.

Influences of main design parameters on the aerodynamic performance of a micro-radial inflow turbine

The micro-radial inflow turbine (MRIT) is not only an important component of a micro-gas turbine but also the core part of a vehicle exhaust gas turbocharger and a small-scale organic Rankine circulatory system. Therefore, designing an MRIT with good performance is of great importance. The values of some main turbine design parameters can significantly influence its aerodynamic performance and structural size. In accordance with the structural characteristics of an MRIT, the relationships between the aerodynamic performance of a turbine and the absolute flow angle at the rotor inlet, the relative flow angle at the rotor outlet, the nozzle and rotor blade velocity coefficients, the ratio of the wheel diameter, velocity ratios, and the degree of reaction were examined. This was done through theoretical analysis combined with experience in the design of a conventional radial inflow turbine. On this basis, the influencing laws and degrees of the seven main design parameters on the aerodynamic performance of an MRIT during aerodynamic design were analyzed. The selection principles of these main design parameters were also summarized. The reasonableness of the above-mentioned selection principles was verified through an aerodynamic design case study of an MRIT combined with a 3D numerical simulation. It was found that the 3D numerical simulation results agreed well with the 1D aerodynamic design. The summarized selection principles of the main design parameters can provide a reference for the successful aerodynamic design of an MRIT.

Optimal design of radial inflow turbine for ocean thermal energy conversion based on the installation angle of nozzle blade

Ocean Thermal Energy Conversion (OTEC), as a new type of renewable energy, has huge development potential. Turbine is the most critical component in the ocean thermal energy conversion system, which directly determines the performance and energy conversion efficiency of the system. Therefore, the optimal design of turbines is very important to improve the efficiency of ocean thermal energy conversion. Based on the full consideration of the small temperature difference application characteristics of ocean thermal energy conversion and the special thermophysical properties of organic working fluids, this paper designs an ammonia working centripetal turbine with a power of 100 kW for OTEC applications, and then analyzes the effect of different geometric parameters on turbine performance. At the same time, the key parameters of the turbine are optimized based on full three-dimensional CFD numerical simulation analysis. It's shown that the nozzle blade installation angle has a very important impact on the performance of the turbine. Through optimization, when the nozzle blade installation angle reaches 30.5°, the efficiency is 91.77%, which is 6.25% points higher than the design value. The internal flow field performance is the best without obvious shock wave and reverse vortex phenomenon, which further improves the efficiency of the turbine and improves the internal flow.

Analysis of radial-outflow turbine design for supercritical CO2 and comparison to radial-inflow turbines

Cycles using supercritical carbon dioxide have been recognized as potential future power technology. However, the turbines in these systems tend to experience very high rotational speeds and entail small physical sizes, which can affect on the overall feasibility. One turbine type having potential to overcome some of the described challenges is the radial outflow turbine. However, its use in supercritical carbon dioxide power systems has not yet been extensively studied since typically axial or radial inflow turbines are considered instead. In this paper, the design of radial-outflow turbines with supercritical carbon dioxide is carried out and the results are compared to the respective radial inflow turbine designs. The analysis was carried out with turbine inlet temperature of 600 °C, inlet pressure of 200 bar and outlet pressure of 78 bar. Designs with four mass flow rates were investigated to study the effect of the power scale on the turbine design and losses. The geometry, efficiency, rotor stress and axial force were defined and analyzed for each design case. The results show that both the investigated turbine types can reach high isentropic efficiencies ranging from about 85% to over 90%. The radial outflow turbines can reach high efficiencies at wider specific speed range whereas the efficiency of radial inflow turbine is reduced more steeply, as the design speed is changed from its optimal value. Radial outflow turbines also reach high efficiencies with lower design speeds and that can be considered advantageous, since it helps to reduce the challenges related to turbomachinery rotordynamic and mechanical design. As a conclusion of the study, it is suggested that the use of radial outflow turbines can increase the feasibility of supercritical carbon dioxide power systems at the examined power scales.

Turbine Design and Optimization for a Supercritical CO2 Cycle Using a Multifaceted Approach Based on Deep Neural Network

Turbine as a key power unit is vital to the novel supercritical carbon dioxide cycle (sCO2-BC). At the same time, the turbine design and optimization process for the sCO2-BC is complicated, and its relevant investigations are still absent in the literature due to the behavior of supercritical fluid in the vicinity of the critical point. In this regard, the current study entails a multifaceted approach for designing and optimizing a radial turbine system for an 8 MW sCO2 power cycle. Initially, a base design of the turbine is calculated utilizing an in-house radial turbine design and analysis code (RTDC), where sharp variations in the properties of CO2 are implemented by coupling the code with NIST’s Refprop. Later, 600 variants of the base geometry of the turbine are constructed by changing the selected turbine design geometric parameters, i.e., shroud ratio (rs4r3), hub ratio (rs4r3), speed ratio (νs) and inlet flow angle (α3) and are investigated numerically through 3D-RANS simulations. The generated CFD data is then used to train a deep neural network (DNN). Finally, the trained DNN model is employed as a fitting function in the multi-objective genetic algorithm (MOGA) to explore the optimized design parameters for the turbine’s rotor geometry. Moreover, the off-design performance of the optimized turbine geometry is computed and reported in the current study. Results suggest that the employed multifaceted approach reduces computational time and resources significantly and is required to completely understand the effects of various turbine design parameters on its performance and sizing. It is found that sCO2-turbine performance parameters are most sensitive to the design parameter speed ratio (νs), followed by inlet flow angle (α3), and are least receptive to shroud ratio (rs4r3). The proposed turbine design methodology based on the machine learning algorithm is effective and substantially reduces the computational cost of the design and optimization phase and can be beneficial to achieve realistic and efficient design to the turbine for sCO2-BC.

A comparative investigation of thermodynamic performance and flow field structure of a modified Collins cycle-based helium turboexpander system

The optimum design of radial expansion turbine and nozzle (turboexpander) have a remarkable effect on the thermophysical performance of gas liquefaction cycles. The present study proposes a new mean-line design, sensitivity analysis, and optimization method to develop three turboexpander systems for a modified Collins cycle-based helium liquefaction system. The proposed method deals with the real gas equation of state to determine the turboexpander configurations and their performance at off-design conditions. The mean-line design approach integrated with different loss correlations has been performed using an in-house code in Matlab® environment. Furthermore, sensitivity analysis and artificial neural network-based optimization process of thirteen design coefficients and non-dimensional variables has been carried out which improves the off-design performance of the turboexpander up to 4.43%, 12.57%, and 16.36% for total-to-static efficiency, total losses, and power output respectively. Applying the aforementioned procedure, three turboexpanders have been designed. After that, a three-dimensional transient blade-row turbulent flow simulations have been carried out to stimulate the rotor-stator interaction at different operating conditions (25 bar & 80 K, 7 bar & 50 K, and 25 bar & 30 K) and rotational speeds (2.84 × 105, 1.61 × 105, and 2.75 × 105 rpm) using k-ω shear stress transport turbulence model. The commercial Navier-Stokes finite volume solver ANSYS CFX® has been used to study a comparative thermodynamic performance and flow field structures at different streamwise and spanwise directions of the entire flow passage. Additionally, the present numerical results have been validated with available experimental and computational data in the open literature. The present design, optimization, and numerical procedure presented herein will be advantageous for the future development of efficient small-scale turboexpander systems subjected to wide operating ranges.

Equation-oriented methods for design optimization and performance analysis of radial inflow turbines

This paper presents methods for design optimization and performance analysis of radial inflow turbines. Both methods are formulated in an equation-oriented manner and involve a single mathematical problem that is solved by an efficient, gradient-based optimization algorithm. In addition, the comparison of the model output with experimental data showed that the underlying mean-line flow model accurately predicts the variation of mass flow rate and isentropic efficiency as a function of the pressure ratio, rotational speed, and nozzle throat area. Moreover, the capabilities of the proposed methods were demonstrated by carrying out the preliminary design and performance prediction of the radial inflow turbine of an organic Rankine cycle. The results indicate that the design optimization method converges to the global optimum solution, regardless of the start values for the independent variables. In addition, the performance maps generated by the performance analysis method are physically consistent and agree with general findings from experimental data reported in the open literature. Considering the accuracy, robustness and low computational cost of the proposed methods, they can be regarded as a powerful tool for the preliminary design and performance prediction of radial inflow turbines, either as a standalone component or as part of a larger system.

Design and loss analysis of radial turbines for supercritical CO2 Brayton cycles

The use of supercritical fluids has been identified as potential solution in realizing highly efficient and compact sized power systems. In this study, the effect of design power scale and specific speed on supercritical CO2 operated radial inflow turbines within the power range of 0.1 MW–3.5 MW is investigated and analyzed. A radial turbine design tool including loss distribution analysis based on loss correlations was developed. In general, the SCO2 radial turbines can be designed to have high efficiency with efficiency ranging from over 80%–87% depending on the turbine design power scale. On the other hand, the turbine dimensions are small and the required rotational speeds are significantly high even at MW scale designs. It was observed that the specific speed and mass flow rate highly affect both the geometry and the turbine loss distribution. Turbine designs with highest isentropic efficiencies were observed with specific speeds ranging from 0.50 to 0.60. With the lowest investigated turbine power outputs from 100 kW to few hundreds of kW the tip clearance loss is the most significant loss whereas the passage, stator and exit kinetic loss are the most significant loss sources at higher power levels.

Experimental Fluid Dynamics Applications in Radial Turbomachines: Inlet Recirculation in Centrifugal Compressor, Rotating Stall and Flow in Vaneless Diffuser, and Improvement in Accuracy of CFD for Predicting Flow Fields in a Radial Turbine Rotor

Performance of a turbomachine strongly depends on its internal flow. CFD (Computational Fluid Dynamics) is now an essential tool obtaining information on such internal flow as well as its performance. However, when CFD is taken into a design process, the accuracy and feature of a CFD code must be understood. CFD requires EFD (Experimental Fluid Dynamics) for validating and ensuring its accuracy. Besides, EFD provides some empirical rules and models to complex phenomena that CFD needs high computational costs and long turnaround time and that are difficult to be integrated in a design work. Since CFD and EFD are complementary to each other, EFD with CFD or CFD with EFD serves as a powerful tool to understand flow phenomena in turbomachines. So, EFD is still important and frequently applied in industries to design and develop radial turbomachines. Examples of EFD conducted during the design of centrifugal compressors and radial turbines in the author’s affiliation are introduced here.

Aerodynamic design and computational fluid dynamic analysis of radial outflow turbines for steam Rankine cycle and supercritical carbon dioxide Brayton cycle

The first part of this paper presents the design of a radial outflow steam turbine for a micro steam power pump block of 200 kW capacity based on a unique Ljungstrom turbine design methodology. Computational fluid dynamic (CFD) simulations were carried out for the 18-stage radial outflow steam turbine at design and off-design points, and results proved the validity of the undertaken design methodology. The design point CFD simulation showed a total to total efficiency of 74.4% for the steam turbine. Specific speed and specific diameter values for the radial outflow steam turbine stages were calculated and superimposed on the Balje's specific speed-specific diameter chart, thus identifying a unique radial outflow turbine zone in the chart. The second part of this paper presents a new design methodology based on specific speed and specific diameter values for designing a supercritical carbon dioxide radial outflow turbine for a 1 MW supercritical carbon dioxide (SCO2) Brayton cycle. CFD simulations were carried out at design and off-design points for the SCO2 turbine. The total to total efficiency from the CFD simulation at the design point for the SCO2 turbine is 84.6%.

Aerodynamic design and computational fluid dynamic analysis of radial outflow turbines for steam Rankine cycle and supercritical carbon dioxide Brayton cycle

The first part of this paper presents the design of a radial outflow steam turbine for a micro steam power pump block of 200 kW capacity based on a unique Ljungstrom turbine design methodology. Computational fluid dynamic (CFD) simulations were carried out for the 18-stage radial outflow steam turbine at design and off-design points, and results proved the validity of the undertaken design methodology. The design point CFD simulation showed a total to total efficiency of 74.4% for the steam turbine. Specific speed and specific diameter values for the radial outflow steam turbine stages were calculated and superimposed on the Balje's specific speed-specific diameter chart, thus identifying a unique radial outflow turbine zone in the chart. The second part of this paper presents a new design methodology based on specific speed and specific diameter values for designing a supercritical carbon dioxide radial outflow turbine for a 1 MW supercritical carbon dioxide (SCO2) Brayton cycle. CFD simulations were carried out at design and off-design points for the SCO2 turbine. The total to total efficiency from the CFD simulation at the design point for the SCO2 turbine is 84.6%.

Investigation of a Radial Turbine Design for a Utility-Scale Supercritical CO2 Power Cycle

This paper presents the design procedure and analysis of a radial turbine design for a mid-scale supercritical CO 2 power cycle. Firstly, thermodynamic analysis of a mid-range utility-scale cycle, similar to that proposed by NET Power, is established while lowering the turbine inlet temperature to 900 ∘ C in order to remove cooling complexities within the radial turbine passages. The cycle conditions are then considered for the design of a 100 MW t h power scale turbine by using lower and higher fidelity methods. A 510 mm diameter radial turbine, running at 21,409 rpm, capable of operating within a 5% range of the required cycle conditions, is designed and presented. Results from computational fluid dynamics simulations indicate the loss mechanisms responsible for the low-end value of the turbine total-to-total efficiency which is 69.87%. Those include shock losses at stator outlet, incidence losses at rotor inlet, and various mixing zones within the passage. Mechanical stress calculations show that the current blade design flow path of the rotor experiences tolerable stress values, however a more detailed re-visitation of disc design is necessitated to ensure an adequate safety margin for given materials. A discussion of the enabling technologies needed for the adoption of a mid-size radial turbine is given based on current advancements in seals, bearings, and materials for supercritical CO 2 cycles.