Design Of Radial Inflow 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.

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.

Design of Radial-Inflow Turbines for Low-Temperature Organic Rankine Cycle

This study presents the development of a design method that has been extended to the design of radial-inflow turbines operating in organic Rankine cycles (ORC). Both the conventional design method and the circulation method available in the literature have been reviewed. The two main limitations of the current circulation method that make it not suitable for the ORC turbine design are the lack of real gas capability and 3D blades with high stresses. Using the circulation method, the flow field is decomposed into a potential part and a rotational part. The mean velocity field and the periodic velocity field are solved separately. To model the thermodynamic properties of the real gas, NIST REFPROP or CoolProp are used. The blade geometry is then solved iteratively by assuming that the velocity vector is parallel to the blade surface. The blade boundary condition is modified to force the blade camber to be radial-fibred, which is helpful to reduce the centrifugal bending stress on the blade. All the formulations are derived step by step, and the numerical treatments, including grid generation, numerical differentiation, computational scheme, and convergence, are discussed in detail. This method is validated by designing a R245fa ORC turbine rotor. The performance of the rotor design is predicted by CFD and FEA simulations, and it is compared to the results using other methodologies in the literature.

Design and numerical analysis of supersonic radial-inflow turbines for transcritical ORC processes

Radial inflow turbine design was investigated for ORC systems having transcritical and close to critical point expansion. The analysis was carried out by combining the turbine design and turbine loss analysis with a thermodynamic cycle analysis. Six fluids were investigated, including three hydrocarbons and three fluorocarbons. The objective is to investigate in detail the design and efficiency of ORC turbines designed for transcritical cycles and close to the critical point expansions, where the real gas effects and the density changes along the expansion are significant. The results of the efficiency predictions gained by using the existing enthalpy loss correlations were compared against computational fluid dynamics simulations. It was revealed that using supercritical inlet state leads to more compact turbine wheel dimensions, increased turbine power, as well as increased rotational speed, when compared to subcritical processes. On the other hand, higher turbine efficiencies were reached with subcritical turbine inlet conditions. This is mainly because of the increased stator outlet Mach number, increased expansion ratio, and lower blade height at the rotor inlet with supercritical turbine inlet conditions, resulting into higher losses along the expansion.

A Reliable Update of the Ainley and Mathieson Profile and Secondary Correlations

Empirical correlations are still fundamental in the modern design paradigm of axial turbines. Among these, the prominent Ainley and Mathieson correlation (Ainley D. and Mathieson G., 1951, “A Method of Performance Estimation for Axial-Flow Turbines,” ARC Reports and Memoranda No. 2974) and its derivatives, plays a crucial role. In this paper, the underlying assumptions of the aforementioned models are discussed by means of a descriptive review, whilst an attempt is made to enhance their reliability and, potentially, accuracy in performance estimations. Closer investigation reveals an intriguing misuse of the lift coefficient in the secondary loss. In light of this, an enhanced model that, notably, builds upon the Zweifel criterion and the vortex penetration depth concept is developed and discussed. The obtained accuracy is subsequently assessed through CFD computations, employing a database comprising 109 cascades. The results indicate a 50% probability of achieving the ±15% error interval, which is twice as good as the most recent Aungier model (Aungier R., 2006, “Turbine Aerodynamics: Axial-Flow and Radial-Inflow Turbine Design and Analysis”, ASME Press, New York). Furthermore, the reliability of the proposed model is demonstrated by a reconstruction of the Smith chart, on the one hand, and a performance analysis, on the other. The reconstruction exhibits contours that conform to the original. The results of the performance study are compared with the CFD solutions of eight cascades working in off design conditions and confirm the need of the additionally included turbine design parameters, such as the axial velocity and the meanline radius ratios.

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.

Investigation on Interaction between Geometry and Performance and Design of S-CO2 Radial Inflow Turbine’ s Vaneless Inlet Volute

The inlet volute is one of the key components that guide the working fluid into the radial inflow turbine. It has a significant effect on the performance of the radial inflow turbine. The conventional design criteria for the vaneless inlet volute mainly focuses on the ideal gas, which does not apply to real gas cases, such as supercritical carbon dioxide(S-CO2). In this paper, an MW-class S-CO2 radial inflow turbine is studied. Firstly, the inlet volute design of the radial inflow turbine with a vaned stator is completed, and the flow in the whole machine is calculated using CFD simulations. Then, based on the inlet boundary conditions of the impellers, the vaneless inlet volute with different throat areas and cross-sectional area distributions are investigated. The results indicate that the size of the counter rotating vortexes in the vaneless inlet volute increases with the throat area increasing, and is also influenced apparently by the cross-sectional area distribution. The volute throat area has little effect on the circumferential distribution of the outlet airflow angle but changes the average value of the airflow angle. The cross-sectional area distribution of the volute influences the circumferential distribution of the outlet flow angle. The result indicates that volute with a small-scale convex profile has a uniform outlet flow field. Compared to the turbine with the vaned stator, the radial dimension of the vaneless volute turbine obtained in the final design is significantly reduced, and the total-total efficiency at the design point is 85.62%, which meets the design requirements. Moreover, it also has good performance at off-design operating conditions.

Thermodynamic analysis and optimization of organic Rankine cycles based on radial-inflow turbine design

In recent years, high-temperature organic Rankine cycle (ORC) with a heat source temperature over 300 °C has attracted interests, which has wide range of applications from industrial point of view. However, few researchers have focused on the coupled design and optimization of the high-temperature ORC system and radial-inflow turbine (RIT). In this work, a coupled design of the ORC system and RIT with the heat source inlet temperatures of 300, 350 and 400 °C is developed using non-dominated sorting genetic algorithm. The ORC thermal efficiency and turbine performance factor (PF) are introduced as optimization objectives. Two mixtures of siloxanes, seven pure siloxanes and nine pure hydrocarbons are considered as working fluid candidates. In addition, the thermodynamic comparison between mixtures of siloxanes and pure working fluids is presented. Moreover, the influences of the turbine inlet total temperature, total-to-static expansion ratio, and specific speed on the ORC thermal efficiency, turbine performance, and turbine size are investigated. The results show that the turbine power output and cycle thermal efficiency are more sensitive to the expansion ratio while turbine size is more sensitive to the turbine inlet total temperature and specific speed. In addition, PF increases with the rise of the turbine inlet total temperature, expansion ratio and specific speed. Moreover, compared with pure working fluids, mixtures of siloxanes have higher efficiencies, but larger turbine and heat exchanger size. Cyclohexane, toluene, m-xylene and hexane with higher PF and smaller size of turbine and heat exchanger are promising working fluids in applications where the compact turbine and heat exchanger is preferred, such as vehicle waste heat recovery.

Performance analysis of radial-inflow turbine of ORC: New combined approach of preliminary design and 3D CFD study

A new methodology for the aerothermodynamic design of radial-inflow turbines used in organic Rankine cycles is presented. Initially, a fully detailed one-dimensional analysis was performed, where the real gas properties of R123 are calculated using the REFPROP© software. The developed model was validated against the most recent studies. Next, a 3D CFD analysis of the nozzle and the rotor was carried out using ANSYS-CFX® software. The 3D CFD method considered the influence of the rotor shroud curvature, which strongly influences the performance characteristics. The variations of this parameter allowed us to obtain uniform velocity contours, better blade loading and avoided the flow separation observed in the first attempt geometry. A comparison between the 1D mean-line and 3D CFD approach showed good agreement, validating the reliability of the two approaches. Also, an analysis of the 3D flowfield for different pressure ratios was performed to verify the quality of the method. The developed methodology has proven to be an appropriate tool for the radial-inflow ORC turbines design, which integrates uni- and three-dimensional models, for the prediction and improvement of the performance characteristics. The integration of these two approaches results in a novel procedure, since some phenomena associated with the three-dimensional characteristics of flow cannot be analyzed in detail in the one-dimensional analysis and are only possible to detect by a complete 3D CFD study.

Effects of grooved vanes on shock wave and forced response in a turbocharger turbine

In radial inflow turbine design, the optimization of turbine geometry for aerodynamic performance improvement is often constrained by the requirement of reliability, thus facing a trade-off. One of the vital challenges for a better trade-off is how to mitigate the forced response of turbine wheel, while maintaining high efficiency, so as to avoid high cycle fatigue failure. In this article, using a grooved surface on nozzle vanes for the forced response reduction was investigated. In light of the fact that the investigation on the high cycle fatigue issue involves both aerodynamic interactions and structural analyses, a customized computer code was developed using MATLAB software to couple computational fluid dynamics simulations with finite element analysis calculations. Partial results were compared against experimental results, respectively, to validate the numerical method. The coupled numerical method reveals that using the grooved surface on the nozzle vane alters the shock wave structure, decreases the peak stress of turbine wheel by 8%, and deteriorates turbine efficiency by 0.05 percentage points.

Preliminary design of radial inflow turbine and working fluid selection based on particle swarm optimization

Organic Rankine cycle (ORC) is an efficient technique to recycle the low temperature heat sources. The design method of the critical component, radial inflow turbine, is a main focus of research. A preliminary design method was developed to optimize eight critical parameters based on particle swarm optimization (PSO) algorithm. The isotropic efficiency was the objective function of the algorithm. Six working fluids were selected to conduct turbine design based on the design method. The turbine with R245fa was determined to be optimal due to its small geometry size, high exergy efficiency (0.929) and high load coefficient (1.1027). The off-design performance of R245fa turbine was investigated with the variation of pressure ratio (PR), stator inlet temperature and power output. The results indicate that the turbine efficiencies increase with the reduction of PR and turbine inlet temperature and the increase of power output. The exergy efficiency and isotropic efficiency drop slightly with the increase of turbine inlet temperature. So the turbine with R245fa exhibited good off-design performance.

Multi-objective optimization of ORC parameters and selection of working fluid using preliminary radial inflow turbine design

Organic Rankine cycles (ORCs) are used to generate power from low temperature heat sources. In this study, 28 hydro carbon (HC), hydro fluorocarbon (HFC) and hydro fluoroolefin (HFO) working fluids are used for three different heat source temperatures (90, 120 and 150 °C). A 1-D radial-inflow turbine (RIT) design with loss calculations is incorporated into the model to add dynamic turbine stage efficiency. The turbine model is run together with the ORC, and real gas properties are used for the entire system. A genetic algorithm multi-objective optimization is used to design an ORC with minimum thermal conductance per net power output and maximum performance factor (PF). The decision variables are specific speed, condensation pressure, pressure ratio at the turbine stage, degree of superheating and pinch point temperature difference (PPTD) in the evaporator. Pareto frontiers are obtained at the end of the study, and a decision-making method (TOPSIS) is used to select an optimum solution for each working fluid. R1234yf, R1234ze(e) and isobutane are found to be the optimum working fluids at 90, 120 and 150 °C heat source temperatures respectively. For each solution, turbine geometry, fluid velocities and impeller rotational speed are calculated.

An Integrated Design and Optimization Approach for Radial Inflow Turbines—Part II: Multidisciplinary Optimization Design

This paper proposes an integrated design and optimization approach for radial inflow turbines consisting of an automated preliminary design module and a flexible three-dimensional multidisciplinary optimization module. The latter was constructed by an evolution algorithm, a genetic algorithm-assisted self-learning artificial neural network and a dynamic sampling database. The 3-D multidisciplinary optimization approach was validated by the original T-100 turbine and the T-100re turbine obtained from the automated preliminary design approach, for maximizing the total-to-static efficiency and minimizing the rotor weight while keeping the mass flow rate constant and stress limitation satisfied. The validation results indicate that the total-to-static efficiency is 89.6%, increased by 1.3%, and the rotor weight is reduced by 0.14 kg (14.6%) based on the T-100re turbine, while the efficiency is 88.2%, increased by 2.2% and the weight is reduced by 0.49 kg (37.4%) based on the original T-100 turbine. Moreover, the T-100re turbine shows better performance at the preliminary design stage and conserves this advantage to the end, though both the aerodynamic performance of the T-100 and the T-100re turbine are improved after 3-D optimization. At the same time, it is implied that the preliminary design plays an essential role in the radial inflow turbine design process, and it is hard for only 3-D optimization to get a further performance improvement.

An improved modeling for low-grade organic Rankine cycle coupled with optimization design of radial-inflow turbine

Organic Rankine cycle (ORC) has been proven to be an effective and promising technology to convert low-grade heat energy into power, attracting rapidly growing interest in recent years. As the key component of the ORC system, turbine significantly influences the overall cycle performance and its efficiency also varies with different working fluids as well as in different operating conditions. However, turbine efficiency is generally assumed to be constant in the conventional cycle design. Aiming at this issue, this paper couples the ORC system design with the radial-inflow turbine design to investigate the thermodynamic performance of the ORC system and the aerodynamic characteristics of radial-inflow turbine simultaneously. The constrained genetic algorithm (GA) is used to optimize the radial-inflow turbine with attention to six design parameters, including degree of reaction, velocity ratio, loading coefficient, flow coefficient, ratio of wheel diameter, and rotational speed. The influence of heat source outlet temperature on the performance of the radial-inflow turbine and the ORC system with constant mass flow rate of the heat source and constant heat source inlet temperature is investigated for four kinds of working fluids. The net electrical powers achieved are from few tens kWs to one hundred kWs. The results show that the turbine efficiency decreases with increasing heat source outlet temperature and that the decreasing rate of turbine efficiency becomes faster in the high temperature region. The optimized turbine efficiency varies from 88.06% (using pentane at the outlet temperature of 105°C) to 91.01% (using R245fa at the outlet temperature of 80°C), which appears much higher compared to common values reported in the literature. Furthermore, the cycle efficiency increases monotonously with the growth of the heat source outlet temperature, whereas the net power output has the opposite trend. R123 achieves the maximum cycle efficiency of 12.21% at the heat source outlet temperature of 110°C. Based on the optimized results, the recommended ranges of the key design parameters for ORC radial-inflow turbine are presented as well.

Design of Radial Inflow Turbine for 30 kW Microturbine

Microturbines are small gas turbines that have the capacity range of 25-300 kW. The main components of microturbine are compressor, turbine, combustor and recuperator. This research paper focuses on the design of radial inflow turbine that operates in 30 kW microturbine. In order to operate the 30 kW microturbine with the back work ratio of 0.5, the radial inflow turbine should be designed to produce power at 60 kW. With the help of theory of turbo-machinery and the analytical methods, the design parameters are derived. The design results are constructed in 3D geometry. The 3D fluid-geometry is validated by computational fluid dynamics (CFD) simulation. The simulation results show the airflow path, the temperature distribution, the pressure distribution and Mach number. According to the simulation results, there is no flow blockage between vanes and no shock flow occurs in the designed turbine.

Influence of the radial-inflow turbine efficiency prediction on the design and analysis of the Organic Rankine Cycle (ORC) system

The radial-inflow turbine is a common choice for the power output in the Organic Rankine Cycle (ORC) system. Its efficiency is related to the working fluid property and the system operating condition. Generally, the radial-inflow turbine efficiency is assumed to be a constant value in the conventional ORC system analysis. Few studies focus on the influence of the radial-inflow turbine efficiency selection on the system design and analysis. Actually, the ORC system design and the radial-inflow turbine design are coupled with each other. Different thermal parameters of the ORC system would lead to different radial-inflow turbine design and then different turbine efficiency, and vice versa. Therefore, considering the radial-inflow turbine efficiency prediction in the ORC system design can enhance its reliability and accuracy. In this paper, a one-dimensional analysis model for the radial-inflow turbine in the ORC system is presented. The radial-inflow turbine efficiency prediction in this model is based on the velocity triangle and loss models, rather than a constant efficiency assumption. The influence of the working fluid property and the system operating condition on the turbine performance is evaluated. The thermodynamic analysis of the ORC system with a model predicted turbine efficiency and a constant turbine efficiency is conducted and the results are compared with each other. It indicates that the turbine efficiency selection has a significant influence on the working fluid selection and the system parameter determination.

Investigation of the organic Rankine cycle (ORC) system and the radial-inflow turbine design

Energy and environment issue set utilizing low-grade heat noticed. Organic Rankine Cycle (ORC) has been demonstrated to be a promising technology to recover waste heat. As a critical component of ORC system, the turbine selection has an enormous influence on the system performance. This paper carries out a study on the thermodynamic analysis of ORC system and the aerodynamic design of an organic radial turbine. The system performance is evaluated with various working fluids. The aerodynamic design of the organic radial-inflow turbine is focused due to the high molecule weight and the low sound speed of the organic working fluid. An aerodynamic and profile design system is developed. A radial-inflow turbine with R123 as the working fluid is designed and the numerical analysis is conducted. The simulation results indicate that the shock wave caused by the high expansion ratio in the nozzle is well controlled. Compared with the one-dimensional design results, the performance of the radial-inflow turbine in this paper reaches the design requirements.

EFFECT OF FLOW COEFFICIENT AND LOADING COEFFICIENT ON THE RADIAL INFLOW TURBINE IMPELLER GEOMETRY

Before attempting to the design of radial inflow turbine, some of the techniques used to describe and present the effect of coefficient on geometry, need to be appreciated. The user of turbine will generally require parameters which readily describe the overall dimension of the machine so that assessments and comparisons can be easily made. The designer requires parameters which will enable him to select the correct machine and make valid comparisons between competing designs. This allows the designer to compute more easily the dimension of the machine at different coefficient, to assess the performance of a range of geometrically similar machines. A paper describes the basic design parameters and effect of coefficient on radial inflow turbine impeller geometry for 25kW application.

Numerical and Experimental Study of Unsteady Flow Field and Vibration in Radial Inflow Turbines

The blades of turbocharger impellers are exposed to unsteady aerodynamic forces, which cause blade vibrations and may lead to failures. An indispensable requirement for a safe design of radial inflow turbines is a detailed knowledge of the exciting forces. Up to now, only a few investigations relating to unsteady aerodynamic forces in radial turbines have been presented. To give a detailed insight into the complex phenomena, a comprehensive research project was initiated at the Institut fu¨r Thermische Stro¨mungsmaschinen, at the University of Karlsruhe. A turbocharger test rig was installed in the high-pressure, high-temperature laboratory of the institute. The present paper gives a description of the test rig design and the measuring techniques. The flow field in a vaneless radial inflow turbine was analyzed using laser-Doppler anemometry. First results of unsteady flow field investigations in the turbine scroll and unsteady phase-resolved measurements of the flow field in the turbine rotor will be discussed. Moreover, results from finite element calculations analyzing frequencies and mode shapes are presented. As vibrations in turbines of turbochargers are assumed to be predominantly excited by unsteady aerodynamic forces, a method to predict the actual transient flow in a radial turbine utilizing the commercial Navier–Stokes solver TASCflow3d was developed. Results of the unsteady calculations are presented and comparisons with the measured unsteady flow field are made. As a major result, the excitation effect of the tongue region in a vaneless radial inflow turbine can be demonstrated. [S0889-504X(00)01402-1]

Design and Flow Field Calculations for Transonic and Supersonic Radial Inflow Turbine Guide Vanes

The design of radial inflow turbine guide vanes depends very much on the discharge conditions desired, especially if the choking mass flow is reached. Because of the choking mass flow condition and supersonic discharge Mach numbers, an inverse design procedure based on the method of characteristics is presented. Various designs corresponding to different discharge Mach numbers are shown. Viscous and inviscid flow field calculations for varying discharge conditions show the properties of the guide vanes at design and off-design conditions. In a previous paper (Reichert and Simon, 1994), an optimized design for transonic discharge conditions has been published. In the present paper, additional results concerning the optimum design are presented. For this optimum design an advantageous adjusting mechanism for a variable geometry guide vane has been developed. The effect of guide vane adjustment on the discharge conditions has been investigated using viscous flow field calculations.