Preliminary Aerodynamic Design of a S-CO2 Axial Turbine

2021 ◽  
Author(s):  
R. Senthil Kumaran ◽  
Dilipkumar B. Alone ◽  
Abdul Nassar ◽  
Pramod Kumar
Keyword(s):  
Mass Flow ◽  
Brayton Cycle ◽  
Cfd Simulations ◽  
Fluid Medium ◽  
Axial Turbine ◽  
Real Gas ◽  
Axial Turbines ◽  
Turbine Design ◽  
Turbomachinery Design ◽  
Line Design

Abstract Axial turbines are gaining prominence in supercritical carbon-di-oxide (S-CO2) Brayton cycle power blocks. S-CO2 Brayton cycle power systems designed for 10 MW and upwards will need axial turbines for efficient energy conversion and compact construction. The real gas behavior of S-CO2 and its rapid property variations with temperature presents a strong challenge for turbomachinery design. Applying gas and steam turbine philosophies directly to S-CO2 turbine could lead to erroneous designs. Very little information is available in the open literature on the design of S-CO2 axial turbines. In this paper, design of a 10 MW axial turbine for a simple recuperated Brayton cycle waste heat recovery system is presented. Three repeating stages with nominal stage loading coefficient of 2.3 and flow coefficient of 0.37 were designed. An axial turbine mean-line design method tuned to S-CO2 real gas fluid medium is discussed. 3D blade design was made suing commercial turbomachinery design software AxSTREAM. The turbine was designed for inlet temperature of 818.15 K, pressure ratio of 2.2, rotational speed of 12000 rpm and mass flow rate of 104.5 kg/s. 3D CFD simulations were carried out using the commercial RANS solver ANSYS CFX 2020 R2 with SST turbulence model for closure. S-CO2 was modelled as real gas with Refrigerant Gas Property tables generated over the appropriate pressure and temperature ranges using NIST Refprop database. CFD studies were carried out over a range of mass flow rates and speeds, covering the design and several off-design conditions. The performance maps generated using 3D CFD simulations of the turbine are presented. The geometrical parameters obtained with the mean-line design matched well with that of the 3D turbine design arrived using AxSTREAM. It was observed that the turbine produced 10 MW power at the design condition while passing the required mass flow. CFD studies also showed that the preliminary turbine design achieved a moderate total-to-total efficiency of 80 % at the design condition. The design has potential for further optimization to obtain improved efficiency and for reducing the number of stages from three to two.

Profile Loss Investigations With a S-CO2 Axial Turbine Aerofoil

2020 ◽  
Author(s):  
R. Senthil Kumaran ◽  
Dilipkumar B. Alone ◽  
Pramod Kumar
Keyword(s):  
Numerical Simulations ◽  
Brayton Cycle ◽  
Cfd Simulations ◽  
Fluid Medium ◽  
Real Gas ◽  
Linear Cascade ◽  
Profile Losses ◽  
Axial Turbines ◽  
Profile Loss ◽  
Flow Deflection

Abstract Axial turbines are being extensively designed for supercritical carbon-di-oxide (S-CO2) Brayton cycle power blocks. But very little information is available in the open literature on the aerodynamics of S-CO2 axial turbines, their aerofoils and loss mechanisms. The understanding of real gas behavior of S-CO2 inside a turbine is still very far from complete. Profile losses contribute to more than 50% of overall losses in a turbine. Hence, estimation of profile losses at the outset of the design process is very important. In the present study, the mean section aerofoil of the first stage of a 5 MWe Brayton cycle high temperature turbine is investigated for profile loss characteristics. The basic aerodynamic characteristics of the aerofoil in a linear cascade were initially studied using CFD simulations and cascade test experiments with air as the fluid medium. The aerofoil cascade is then subjected to numerical simulations with S-CO2 as the fluid medium. CFD simulations were carried out using a commercial RANS solver with SST k-ω turbulence model for closure. Air was modelled as ideal gas and S-CO2 was modelled as real gas with Refrigerant Gas Property tables generated over the appropriate pressure and temperature ranges using NIST Refprop database. Losses are also calculated using Craig and Cox loss model. Experiments were carried out by testing a linear cascade model comprising 12 two dimensional blades, in a high-speed cascade wind tunnel. Cascade tests were carried out over a range of exit Mach numbers and incidence angles with air as the working medium. Losses, flow deflection and blade loading were measured during the experiments. Scaling of the profile losses between air and S-CO2 fluid mediums were examined over a range of Mach numbers, Reynolds numbers and incidence angles. Detailed analysis of data generated from numerical simulations, experiments and loss model (mainly in the transonic regime) are discussed in this paper. Losses with S-CO2 was 1.5% lower than that of air while the flow deflection roughly remained the same.

Reduced-Order Through-Flow Design Code for Highly Loaded, Cooled Axial Turbines

2013 ◽  
Author(s):  
Majed Sammak ◽  
Marcus Thern ◽  
Magnus Genrup
Keyword(s):  
Mass Flow ◽  
Rotational Speed ◽  
Design Parameters ◽  
Reduced Order ◽  
Through Flow ◽  
Axial Turbines ◽  
Two Stages ◽  
Turbine Design ◽  
Line Design ◽  
Highly Loaded

The development of advanced computational fluid dynamic codes for turbine design does not substitute the importance of mean-line codes. Turbine design involves mean-line design, through-flow design, airfoil design, and finally 3D viscous modeling. The preliminary mean-line design continues to play an important role in early design stages. The aim of this paper was to present the methodology of mean-line designing of axial turbines and to discuss the computational methods and procedures used. The paper presents the Lund University Axial Turbine mean-line code (LUAX-T). LUAX-T is a reduced-order through-flow tool that is capable of designing highly loaded, cooled axial turbines. The stage computation consists of three iteration loops — cooling, entropy, and geometry iteration loop. The stage convergence method depends on whether the stage is part of the compressor turbine (CT) or power turbine (PT) stages, final CT stage, or final PT stage. LUAX-T was developed to design axial single- and twin-shaft turbines, and various working fluid and fuel compositions can be specified. LUAX-T uses the modified Ainley and Mathieson loss model, with the cooling computation based on the m*-model. Turbine geometries were established by applying various geometry correlations and methods. The validation was performed against a test turbine that was part of a European turbine development program. LUAX-T validated the axial PT of the test turbine, which consisted of two stages with rotational speed 13000 rpm. LUAX-T showed good agreement with the available performance data on the test turbine. The paper presented also the mean-line design of an axial cooled twin-shaft turbine. Design parameters were kept within limits of current practice. The total turbine power was 109 MW, of which the CT power was 55 MW. The CT was designed with two stages with a rotational speed of 9500 rpm, while the PT had two stages with a rotational speed of 6200 rpm. The total cooling mass flow was calculated to 31 kg/s, which corresponds to 23 % of compressor inlet mass flow. LUAX-T proved capable of designing uncooled and cooled turbines.

Sensitivity Study of S-CO2 Compressor Design for Different Real Gas Approximations

2016 ◽  
Author(s):  
Jekyoung Lee ◽  
Seong Kuk Cho ◽  
Jae Eun Cha ◽  
Jeong Ik Lee
Keyword(s):  
Thermodynamic Property ◽  
Critical Point ◽  
Technology Development ◽  
Static Condition ◽  
Sensitivity Study ◽  
Ideal Gas ◽  
Brayton Cycle ◽  
Real Gas ◽  
Compressor Design ◽  
Turbomachinery Design

With the efforts of many researchers and engineers on the Supercritical CO2 (S-CO2) Brayton cycle technology development, the S-CO2 Brayton cycle is now considered as one of the key power technologies for the future. Since S-CO2 Brayton cycle has advantages in economics due to high efficiency and compactness of system, various industries have been trying to develop technologies on the design and analysis of S-CO2 Brayton cycle components. Among various technical issues on the S-CO2 Brayton cycle technology development, treatment of thermodynamic property near the critical point of S-CO2 is very important since the property shows non-linear variation which causes large error on design and analysis results for ideal gas based methodologies. Due to the special behavior of thermodynamic property of CO2 near the critical point, KAIST research team has been trying to develop a S-CO2 compressor design and analysis tool to reflect real gas effect accurately for better design and performance prediction results. The main motivation for developing an in-house code is to establish turbomachinery design methodology based on general equations to improve accuracy of design and analysis results for various working fluids including S-CO2. One of the key improvements of KAIST_TMD which is an in-house tool for S-CO2 turbomachinery design and analysis is the conversion process between stagnation condition and static condition. Since fluid is moving with high flow velocity in a compressor, the conversion process between stagnation and static condition is important and it can have an impact on the design and analysis results significantly. A common process for the conversion is based on the specific heat ratio which is typically a constant from ideal gas assumption. However, specific heat ratio cannot be assumed as a constant for the case of S-CO2 compressor design and analysis because it varies dramatically near the critical point. Thus, in this paper, sensitivity study results on the state condition conversion between stagnation and static conditions with different approaches will be presented and further analysis on impact of the selected approaches on the final impeller design results will be discussed.

scholarly journals Radial Turbine Design for Solar Chimney Power Plants

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 674
Author(s):  
Paul Caicedo ◽  
David Wood ◽  
Craig Johansen
Keyword(s):  
Power Plants ◽  
Reference Frames ◽  
Three Dimensional ◽  
Discrete Ordinates ◽  
Large Area ◽  
Solar Chimney ◽  
Cfd Simulations ◽  
Radial Turbine ◽  
Design Changes ◽  
Turbine Design

Solar chimney power plants (SCPPs) collect air heated over a large area on the ground and exhaust it through a turbine or turbines located near the base of a tall chimney to produce renewable electricity. SCPP design in practice is likely to be specific to the site and of variable size, both of which require a purpose-built turbine. If SCPP turbines cannot be mass produced, unlike wind turbines, for example, they should be as cheap as possible to manufacture as their design changes. It is argued that a radial inflow turbine with blades made from metal sheets, or similar material, is likely to achieve this objective. This turbine type has not previously been considered for SCPPs. This article presents the design of a radial turbine to be placed hypothetically at the bottom of the Manzanares SCPP, the only large prototype to be built. Three-dimensional computational fluid dynamics (CFD) simulations were used to assess the turbine’s performance when installed in the SCPP. Multiple reference frames with the renormalization group k-ε turbulence model, and a discrete ordinates non-gray radiation model were used in the CFD simulations. Three radial turbines were designed and simulated. The largest power output was 77.7 kW at a shaft speed of 15 rpm for a solar radiation of 850 W/m2 which exceeds by more than 40 kW the original axial turbine used in Manzanares. Further, the efficiency of this turbine matches the highest efficiency of competing turbine designs in the literature.

Numerical Simulation of the Performance of an Axial Compressor Operating With Supercritical Carbon Dioxide

2018 ◽  
Author(s):  
Jinlan Gou ◽  
Wei Wang ◽  
Can Ma ◽  
Yong Li ◽  
Yuansheng Lin ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Numerical Simulation ◽  
Supercritical Carbon Dioxide ◽  
Critical Point ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Compressor ◽  
Brayton Cycle ◽  
Supercritical Carbon

Using supercritical carbon dioxide (SCO2) as the working fluid of a closed Brayton cycle gas turbine is widely recognized nowadays, because of its compact layout and high efficiency for modest turbine inlet temperature. It is an attractive option for geothermal, nuclear and solar energy conversion. Compressor is one of the key components for the supercritical carbon dioxide Brayton cycle. With established or developing small power supercritical carbon dioxide test loop, centrifugal compressor with small mass flow rate is mainly investigated and manufactured in the literature; however, nuclear energy conversion contains more power, and axial compressor is preferred to provide SCO2 compression with larger mass flow rate which is less studied in the literature. The performance of the axial supercritical carbon dioxide compressor is investigated in the current work. An axial supercritical carbon dioxide compressor with mass flow rate of 1000kg/s is designed. The thermodynamic region of the carbon dioxide is slightly above the vapor-liquid critical point with inlet total temperature 310K and total pressure 9MPa. Numerical simulation is then conducted to assess this axial compressor with look-up table adopted to handle the nonlinear variation property of supercritical carbon dioxide near the critical point. The results show that the performance of the design point of the designed axial compressor matches the primary target. Small corner separation occurs near the hub, and the flow motion of the tip leakage fluid is similar with the well-studied air compressor. Violent property variation near the critical point creates troubles for convergence near the stall condition, and the stall mechanism predictions are more difficult for the axial supercritical carbon dioxide compressor.

High Resolution Heat Transfer Measurements on the Stator Endwall of an Axial Turbine

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Benoit Laveau ◽  
Reza S. Abhari ◽  
Michael E. Crawford ◽  
Ewald Lutum
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
High Resolution ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Wall Temperature ◽  
Adiabatic Wall ◽  
Axial Turbine ◽  
The Heat Transfer Coefficient

In order to continue increasing the efficiency of gas turbines, an important effort is made on the thermal management of the turbine stage. In particular, understanding and accurately estimating the thermal loads in a vane passage is of primary interest to engine designers looking to optimize the cooling requirements and ensure the integrity of the components. This paper focuses on the measurement of endwall heat transfer in a vane passage with a three-dimensional (3D) airfoil shape and cylindrical endwalls. It also presents a comparison with predictions performed using an in-house developed Reynolds-Averaged Navier–Stokes (RANS) solver featuring a specific treatment of the numerical smoothing using a flow adaptive scheme. The measurements have been performed in a steady state axial turbine facility on a novel platform developed for heat transfer measurements and integrated to the nozzle guide vane (NGV) row of the turbine. A quasi-isothermal boundary condition is used to obtain both the heat transfer coefficient and the adiabatic wall temperature within a single measurement day. The surface temperature is measured using infrared thermography through small view ports. The infrared camera is mounted on a robot arm with six degrees of freedom to provide high resolution surface temperature and a full coverage of the vane passage. The paper presents results from experiments with two different flow conditions obtained by varying the mass flow through the turbine: measurements at the design point (ReCax=7.2×105) and at a reduced mass flow rate (ReCax=5.2×105). The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are derived from measurements at 14 different isothermal temperatures. The experimental data are supplemented with numerical predictions that are deduced from a set of adiabatic and diabatic simulations. In addition, the predicted flow field in the passage is used to highlight the link between the heat transfer patterns measured and the vortical structures present in the passage.

scholarly journals Sensitivity of Supersonic ORC Turbine Injector Designs to Fluctuating Operating Conditions

2015 ◽  
Author(s):  
Elio A. Bufi ◽  
Paola Cinnella ◽  
Xavier Merle
Keyword(s):  
Method Of Characteristics ◽  
Organic Rankine Cycle ◽  
Design Procedure ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Real Gas ◽  
Real Gas Effects ◽  
Nozzle Shape ◽  
Turbine Design ◽  
The Impact

The design of an efficient organic rankine cycle (ORC) expander needs to take properly into account strong real gas effects that may occur in given ranges of operating conditions, which can also be highly variable. In this work, we first design ORC turbine geometries by means of a fast 2-D design procedure based on the method of characteristics (MOC) for supersonic nozzles characterized by strong real gas effects. Thanks to a geometric post-processing procedure, the resulting nozzle shape is then adapted to generate an axial ORC blade vane geometry. Subsequently, the impact of uncertain operating conditions on turbine design is investigated by coupling the MOC algorithm with a Probabilistic Collocation Method (PCM) algorithm. Besides, the injector geometry generated at nominal operating conditions is simulated by means of an in-house CFD solver. The code is coupled to the PCM algorithm and a performance sensitivity analysis, in terms of adiabatic efficiency and power output, to variations of the operating conditions is carried out.

An Integrated Software Procedure to Support Teaching of Radial Inflow Turbine Design

2007 ◽  
Author(s):  
Carlo Cravero ◽  
Martino Marini
Keyword(s):  
Design Analysis ◽  
Design Parameters ◽  
Analysis Tool ◽  
Software Suite ◽  
Computational Tools ◽  
Blade Loading ◽  
Radial Turbine ◽  
Integrated Software ◽  
Turbine Design ◽  
Turbomachinery Design

The authors decided to organize their design/analysis computational tools in an integrated software suite in order to help teaching radial turbine, taking advantage of their research background and a set of codes previously developed. The software is proposed for use during class works and the student can either use a single design/analysis tool or face a complete design loop consisting of iterations between design and analysis tools. The intended users are final year students in mechanical engineering. The codes output are discussed with two practical examples in order to highlight the turbomachinery performance at design and off-design conditions. The above suite gives the student the opportunity of getting used to different concepts (choking, blade loading, performance maps, …) that are encountered in turbomachinery design and of understanding the effects of the main design parameters.

scholarly journals Optimal design to control rotor shaft vibrations and thermal management on a supercritical CO2 microturbine

2021 ◽  
Vol 22 ◽  
pp. 22
Author(s):  
Jun Li ◽  
Hal Gurgenci ◽  
Jishun Li ◽  
Lun Li ◽  
Zhiqiang Guan ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Jet Impingement ◽  
Brayton Cycle ◽  
Cooling Device ◽  
Resonance Amplitude ◽  
Chaotic Mapping ◽  
The Given

Supercritical carbon dioxide (SCO2) Brayton cycle microturbine can be used for the next generation of solar power. In order to comprehensively optimize the supporting system and cooling device parameters of Brayton cycle shafting, the concept of chaos interval is introduced by chaotic mapping, and the CIMPSO algorithm is proposed to optimize the multi-objective rotor system model with nonlinear variables.The results show that the resonance amplitude of the optimized model is effectively attenuated, and the critical speed point is far away from the working speed, which shows the robustness of the optimization algorithm. Finally, based on arbitrary several sets of optimization solutions and empirical parameters, the finite element model of shafting is established for simulation, and the results show that the optimized solution has certain guiding significance for the design of the rotor system.The cooling device is designed and simulated by CFD method based on the optimal solution set. Both the inlet boundary conditions of given pressure (1 MPα) and given mass flow rate (0.1 kg/s) numerical calculations were carried out to characterize the cooling performance, for different jet impingement configurations (Hr/din = 0.0125 ∼ 5).Several sets of analyses show the strong effects of the jet-to-target spacing (Hr/din) on the rotor thermal performance at a given diameter (din) of the nozzle. Average temperature (Tc) at the free end of the rotor show that, as jet-to-target distance decreases (0.0125 ≤ Hr/din ≤ 0.33), the heat dissipation efficiency of the cooling device with the given pressure boundary condition tends to decrease, while the conclusion is opposite when the inlet boundary condition is set to the given mass flow rate. And there is an interval for the optimal combination (Hr/din) to promote the cooling efficiency.

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