Radial Flow Turbine Research Articles

Electrical performance of radial turbine driven by low temperature heat source: numerical investigation

High-performance Organic Rankine Cycle (ORC) systems are extensively utilized across various industrial sectors. In some applications, radial flow turbines are crucial for low-temperature heat sources. This study aims to enhance the energy and electrical efficiency of small radial turbines in Organic Rankine Cycle (ORC) ORC systems using n-pentane as the working fluid through numerical analysis. Micro-turbines are proposed to maximize performance for ORC applications. To assess the electrical, hydrodynamic and thermodynamic performance, 3D RANS simulations are conducted for five different mass flow rates with an inlet temperature of 450 K. The findings underscore the potential of radial turbines in ORC systems for utilizing low-temperature heat sources effectively. The results conducted on the entropy resulting from the irreversibility of heat transport and the irreversibility of friction. The following ranges contain the significant parameters for which this work has been completed: mass flow rates (0.1–0.5 kg.s-1), 450 k at the inflow.

WR21 marine gas turbine thermodynamic simulator for ship propulsion studies

An original modular mathematical model, based on physical laws, for steady state and dynamics performance simulation of the WR21 gas turbine is presented in the paper. The model, developed in Matlab-Simulink language, is organized in modular form. Each gas turbine component (i.e. compressor, turbine, combustor, heat exchanger) is modelled in a specific simulator block, that simulates the performance of its pertinent component by means of steady state performance maps and/or correlations, time dependent momentum, energy and mass equations, nonlinear algebraic equations. The great application flexibility of the component simulator modules, allows to modelling any gas turbine layout (i.e. axial or radial flow compressor and turbine, rotating shafts number, heat exchangers). The WR21gas turbine, developed mainly for marine propulsion application, is a three shafts gas turbine with thermal regeneration. It is characterized by a high thermodynamic efficiency, which remains high up to 30% of the design power. The WR21 simulator results are validated by comparison with manufacturer or literature data. The WR21 gas turbine main performances are compared to those of the LM 2500 gas turbine, obtained by a previously author paper. The LM 2500 is the gas turbine currently most used in naval propulsion plants. In the article, a comparison between the steady state working data of the two gas turbines is reported in tabular and graphical form and commented.

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.

Intensification of the rate of heat and mass transfer at the wall of a stirred tank reactor by integrating a helical coil turbulence promoter with the tank wall

ABSTRACT The influence of a helical coil turbulence promoter on liquid-solid mass transfer rates in a stirred tank was investigated using a technique that involved measuring the rate of diffusion-controlled copper dissolution in acidified dichromate. The study examined the effects of helical coil tube diameter (d), helical coil pitch (p), impeller rotation speed, impeller geometry (axial and radial), the presence of baffles, and solution physical properties. The presence of the helical coil near the reactor wall significantly enhanced mass transfer rates, with a factor ranging from 1.01 to 2.48. This improvement was accompanied by a corresponding increase in the volumetric mass transfer coefficient (kA), ranging from 2.68 to 4.55, depending on operating conditions. Further analysis revealed that the average mass transfer coefficient increased with decreasing coil tube diameter, while coil pitch had a minimal impact. Additionally, radial flow turbines demonstrated superior mass transfer performance compared to axial flow turbines. The presence of baffles also promoted higher mass transfer rates compared to unbaffled reactors. The experimental data were successfully correlated using dimensionless correlations, emphasizing the significance of these correlations in scaleup and design optimization of catalytic stirred tank reactors with efficient cooling systems.

Experimental mass and heat transfer at a serpentine tube heat exchanger located at the wall of a square stirred tank reactor

• Rates of mass and heat transfer of a serpentine tube heat exchanger were studied. • The serpentine is located at the wall of a square stirred tank reactor. • Variables studied were impeller speed and geometry, tube diameter, and tube pitch. • Dimensionless correlations were developed to design and operate the heat exchanger. • The possibility of using the serpentine tube as a catalyst support was highlighted. Although the study of the heat transfer behavior of stirred tank heat exchangers such as helical coils, vertical tube baffles, and cooling jackets has received much attention, no study has been reported on the heat or mass transfer behavior of serpentine tube heat exchangers, so the present work aims to study rates of mass and heat transfer (by analogy) at the outer surface of a serpentine tube heat exchanger located at the wall of a square stirred tank reactor by the electrochemical technique. Variables studied were impeller rotational speed, impeller geometry, tube diameter, and tube pitch. The mass or heat transfer coefficients were found to increase with increasing impeller speed and decrease with increasing cylinder diameter and pitch. For a given set of conditions, a radial flow turbine produces higher rates of mass transfer than an axial flow turbine. The data were correlated by dimensionless mass transfer correlations which can be used to scale up and operate the heat exchanger. When the mass transfer data at the serpentine tube were compared with those at an active flat wall of equal height, it was found that the mass transfer rate at the serpentine tube is higher than that of the flat wall by an amount ranging from 10% to 210% depending on the operating conditions. The possibility of using the serpentine tube as a catalyst support for conducting diffusion-controlled exothermic immobilized cell biochemical reactions which need rapid cooling to avoid thermal degradation of the biomass was highlighted. The dual-use of the serpentine tubes as a catalyst support and a cooler would reduce the capital and operating costs of immobilized enzyme or cell stirred tank biochemical reactors compared, for instance, with the traditional stirred slurry reactor owing to the elimination of the costly and time-consuming process of separating the final product from the catalyst particles.

Mass and heat transfer at a corrugated wall of a square stirred tank reactor and possible applications

ABSTRACT The electrochemical technique was used to investigate the effect of surface corrugations on the rate of mass and heat transfer (by analogy) in a stirred tank reactor. Impeller rotational speed, impeller shape, corrugation peak to valley height, and corrugation orientation (horizontal or vertical) were among the variables investigated. Depending on the operating conditions, surface corrugation increased the volumetric mass transfer coefficient by a factor ranging from 1.16 to 3.7. Mass transfer data were correlated with dimensionless correlations of an average deviation of ±4.2 and ±5.49 for radial and axial flow turbines, respectively. The significance of the dimensionless equations in determining the rate of heat transfer from the corrugated wall to a cooling jacket was emphasized.

CFD Study of Exhaust Gas Energy Recovery Potential of a Radial Flow Turbine for Electricity Generation

CFD Study of Exhaust Gas Energy Recovery Potential of a Radial Flow Turbine for Electricity Generation

Design and experiment study of a micro radial-flow turbine for a SOFC-MGT turbine hybrid system

Since compact structure and centimeter size of solid-oxide fuel cell system equipped with micro gas turbine (SOFC-MGT), the heat of a micro radial-inflow turbine (RIT) is transferred to compressor through wall heat transfer. In this work, an integrated design method considering wall heat transfer was proposed to develop an efficient micro-RIT applied to c. The one-dimensional design method considering wall heat transfer was established according to theoretical analysis and empirical correlations. The geometric structure of micro-RIT was produced based on the distribution of blade angle, blade thickness and meridional streamline. The structural parameters were optimized by three-dimensional numerical simulation of fluid-thermal-structural coupling to obtain the best geometric model of micro-RIT. A new test method was employed to verify the accuracy of the integrated design method. The results indicate that the integrated design method under adiabatic condition and considering wall heat transfer have the same design accuracy for the mass flow of micro-RIT. However, compared with the integrated design method under adiabatic condition, the integrated design method considering wall heat transfer has better design accuracy for the efficiency of micro-RIT. The maximum error of integrated design method under adiabatic condition is 3.53%, that of integrated design method considering wall heat transfer is 2.71%.

Experimental study on an OWC radial-flow impulse turbine in steady and reciprocating airflows

Self-rectifying air turbines, acting as a power take-off facility, can convert the incident pneumatic power to the shaft torque in the oscillating water column devices. The radial-flow impulse turbine (RFIT) is becoming popular because of its excellent operating performance. A generic RFIT model was designed and tested in constant and reciprocating airflows. The incident and torque coefficients are reported with the scatter diagrams of the turbine efficiencies. The steady-state efficiency in the constant airflow and the average efficiency in the reciprocating airflows peak at 0.48 and 0.49, respectively. The RFIT model has a significant difference in operation performance under the centrifugal and centripetal modes, and the varying frequency of the sinusoidal reciprocating airflows has a more obvious influence on the centripetal mode. In the comparison between two types of airflows with the same pneumatic power, the RFIT model is found to obtain a better performance in the reciprocating airflows.

A comparison of turbine mass flow models based on pragmatic identification data sets for turbogenerator model development

The use of turbogenerators as a means of waste heat recovery has gained interest from industry and academia in recent years. Accurate mass flow models of turbogenerators are required for assessing their impact on overall engine performance during design–development. This paper presents the results of an experimental model identification program for a commercially available turbogenerator. The experimental data was categorised into training and validation data sets. Training data sets were selected using a simulation based method to bound data within a region representative of turbocharger turbine operation. A comprehensive review of promulgated models is presented, and the replication and extrapolation performance with respect to the experimental data sets is assessed. A new family of models is proposed which is applicable to a large class of radial flow turbines. Application of a systematic model selection process based on Akaike Information Criteria yields models from this family with improved performance. Furthermore, the robustness of the proposed family of models is assessed using published experimental data sets from a range of turbine designs, demonstrating the versatility of the proposed model family and model selection techniques.

Development of single sensor fast response pressure probes

Multi-sensor fast response pressure probes are often used in turbomachinery investigations. However, the size of multi-sensor probes are often larger than is ideal. This paper describes the development of a single sensor pressure probe that has sufficient sensitivity for the measurements of unsteady 3D flow fields in turbomachines. Because there is only one sensor, the probe can be made much smaller than previous designs. Several types of probe were designed and tested using largescale models in a wind tunnel. Both the steady state and the dynamic response have been investigated. The relationship between the shape of the probe and its yaw and pitch sensitivity has been investigated through measurements of the pressure distribution on the large-scale models and through visualizations of the flow. Dambach and Hodson [3] proposed a new method of data reduction for a single sensor pressure probe. In that work, a single sensor pressure probe with the shape of a triangular prism was fabricated and tested with success in a radial flow turbine where the flow field was mainly 2D. The probe was shown to have only yaw sensitivity while pitch sensitivity is also important in the survey of three dimensional turbomachinery flows. In this paper, the model probes were used to assess the pitch sensitivity of single sensor pressure probes. All the probes have the sensing face at the end of a radially mounted stem so that they can be used for inter bladerow measurements. Through the steady state measurements, the dependency of pitch sensitivity on (1) the shape of the probe stem (e.g., Square, Circular, and Triangular) and (2) the angle of the slanted sensing face at the tip of the probe were investigated. Having assessed all the designs based on the steady state experiments, the dynamic behaviour of selected designs was investigated. The results indicate that a slanted face and appropriate probe tip design can be used to increase the pitch sensitivity of the single sensor probe to acceptable levels.

A methodology for loss and performance assessment of a variable geometry turbocharger turbine through a new meanline FORTRAN program

PurposeVariable geometry turbine (VGT), a key component of modern internal combustion engines (ICE) turbochargers, is increasingly used for better efficiency and reduced exhaust gas emissions. The aim of this study is the development of a new meanline FORTRAN code for accurate performance and loss assessment of VGTs under a wider operating range. This code is a useful alternative tool for engineers for fast design of VGT systems where higher efficiency and minimum loss are being required.Design/methodology/approachThe proposed meanline code was applied to a variable geometry mixed flow turbine at different nozzle vane angles and under a wide range of rotational speed and the expansion ratio. The numerical methodology was validated through a comparison of the predicted performance to test data. The maps of the mass flow rate as well as the efficiency of the VGT system are discussed for different nozzle vane angles under a wide range of rotational speed. Based on the developed model, a breakdown loss analysis was carried out showing a significant effect of the nozzle vane angle on the loss distribution.FindingsResults indicated that the nozzle angle of 70° has led to the maximum efficiency compared to the other investigated nozzle vane angles ranging from 30° up to 80°. The results showed that the passage loss was significantly reduced as the nozzle vane angle increases from 30° up to 70°.Originality/valueThis paper outlines a new meanline approach for variable geometry turbocharger turbines. The developed code presents the novelty of including the effect of the vane radii variation, due to the pivoting mechanism of the nozzle ring. The developed code can be generalized to either radial or mixed flow turbines with or without a VGT system.

Bayesian Optimization Design of Inlet Volute for Supercritical Carbon Dioxide Radial-Flow Turbine

The radial-flow turbine, a key component of the supercritical CO2 (S-CO2) Brayton cycle, has a significant impact on the cycle efficiency. The inlet volute is an important flow component that introduces working fluid into the centripetal turbine. In-depth research on it will help improve the performance of the turbine and the entire cycle. This article aims to improve the volute flow capacity by optimizing the cross-sectional geometry of the volute, thereby improving the volute performance, both at design and non-design points. The Gaussian process surrogate model based parameter sensitivity analysis is first conducted, and then the optimization process is implemented by Bayesian optimization (BO) wherein the acquisition function is used to query optimal design. The results show that the optimized volute has better and more uniform flow characteristics at design and non-design points. It has a smoother off-design conditions performance curve. The total pressure loss coefficient at the design point of the optimized volute is reduced by 33.26%, and the flow deformation is reduced by 54.55%.

A numerical study for correlating performance versus number of blades and investigating flow characteristics and loss generation of an automotive radial flow turbine

Hybridization of engines is the future technology to overcome the increasing emissions of CO2 and pollutants from internal combustion engines. So far, the current technology, called downsizing, involves reducing engine size while maintaining continuous engine boosting with a turbocharger. It is well known that the radial turbine, an essential component of turbochargers, is a seat of various loss mechanisms such as incidence losses which significantly affect performance. As a contribution for further improving performance and reducing loss generation in radial turbines, this study investigates the effect of the blade number on performance and loss generation within a radial turbine of small scale turbocharger. To this end, six radial turbines were designed with several blade numbers ranging from three up to thirteen. The flow solution was computed by solving the Navier-Stokes equations using a CFD solver. The numerical results were validated against experiments. The results revealed that the impeller of 11 blades provides better performance than the other investigated designs. The results showed a substantial effect of the number of blades on the distribution of flow characteristics and loss generation. The efficiency, mass flow rate, output torque, blade loading, and leakage flow through the clearance gap of the turbine were correlated to the number of blades.

Research on Optimization and Verification of the Number of Stator Blades of kW Ammonia Working Medium Radial Flow Turbine in Ocean Thermal Energy Conversion

Ocean Thermal Energy Conversion (OTEC) is one of the emerging industries of ocean energy and an important link in carbon neutrality. Turbine is a key component of ocean thermal energy conversion, which has an important impact on the performance and energy conversion efficiency of the system. This paper fully considers the application characteristics of ocean thermal energy conversion and the state conversion characteristics of ammonia working fluid. Taking the 100 kW radial inflow turbine in the OTEC application system as an example, based on the design, the turbine is optimized for the key parameters of the turbine stator and the influence of different geometric parameters is analyzed. Subsequently, the optimization results are verified by CFD numerical simulation analysis under different conditions. The results show that the number of stator blades has an important influence on the performance of the turbine. Further optimization studies have shown that through optimization, when the number of stator blades is 33, the internal flow field performance is the best, and the working conditions of the inlet and outlet working fluids are in accordance with the design points without obvious shock wave and reverse flow phenomenon, the efficiency is 89.46%, 3.94% higher than the design value.

Design and Simulation of Radial Flow Turbine Impeller and Investigation Thermodynamic Properties of Flow in LE and TE

Centrifugal (radial flow) turbines are widely used in various industries, including power generation industries, so the study on them is of particular importance. The aim of this study was to investigate the thermodynamic properties of fluid flow in Trailing Edge (TE) and (LE) Leading Edge. For this purpose, first, the rotor (impeller) of the radial flow turbine was designed based on some design data such as flow rate, number of blades, rotational speed, diameter and length of the impeller, and then the designed rotor was simulated in 3D. The simulation done in the pressure based method and the turbulence model is SST and the rotational speed was 140,000(RPM). The results showed that the pressure, temperature and enthalpy in TE are less than LE and the areas close to the hub have the highest pressure. Another phenomenon observed is that in the section LE we see the separation of the flow from the blade surface, which then approaches the blade surface again and follows a relatively regular path,so the entropy in TE is greater than LE. At the end, the results of numerical solution were compared with valid data and the error rate and its reasons were discussed.

Computational Study of a Radial Flow Turbine Operates Under Various Pulsating Flow Shapes and Amplitudes

Abstract Radial flow turbines are extensively used in turbocharging technology due to their unique capability of handling a wide range of exhaust gas flow. The pulsating flow nature of the internal combustion engine exhaust gases causes unsteady operation of the turbine stage. This paper presents the impact of the pulsating flow of various characteristics on the performance of a radial flow turbine. A three-dimensional computational fluid dynamic model was coupled with a one-dimensional engine model to study the realistic pulsating flow. Applying square wave pulsating flow showed the highest degree of unsteadiness corresponding to 92.6% maximum mass flow accumulation due to the consecutive sudden changes of the mass flowrates over the entire pulse. Although sawtooth showed a maximum mass flow accumulation value of 88.9%, the mass flowrates entailed gradual change and resulted in the least overall mass flow accumulation over the entire pulse. These two extremes constrained the anticipated performance of the radial flow turbine that operates under realistic pulsating flow. Such constraints could develop an operating envelope to predict the performance and optimize radial flow turbines’ power extraction under pulsating flow conditions.

Experimental investigation on detonation wave propagation mode in the start-up process of rotating detonation turbine engine

Rotating detonation combustor with pressure-gain capability could be performed as the main combustor of a turbine engine to improve engine performance. In this paper, an experimental structure of a rotating detonation combustor combined with a radial-flow turbine was designed to investigate the start-up process of the rotating detonation turbine engine. The multiple detonation-wave modes of longitudinal pulsed detonation mode, single-wave mode, and multi-wave mode appeared in the combustor with different structures and equivalence ratios. For the guide vane text, the mode evolution process of detonation wave from one wave to several waves appears in the combustion chamber, and the final number of detonation wave increases with the increase of equivalence ratio. For the no guide vane text, the detonation wave in the combustion chamber appears only in the propagation modes of single-wave mode and longitudinal pulsed detonation mode. The longitudinal pulsed detonation mode appears in the range of high equivalence ratio.

A Comparison of Turbine Mass Flow Models Based on Pragmatic Identification Data Sets for Turbogenerator Model Development

The use of turbogenerators as a means of waste heat recovery has gained interest from industry and academia in recent years. Accurate mass flow models of turbogenerators are required for assessing their impact on overall engine performance during design–development. This paper presents the results of an experimental model identification program for a commercially available turbogenerator. The experimental data was categorised into training and validation data sets. Training data sets were selected using a simulation based method to bound data within a region representative of turbocharger turbine operation. A comprehensive review of promulgated models is presented, and the replication and extrapolation performance with respect to the experimental data sets is assessed. A new family of models is proposed which is applicable to a large class of radial flow turbines. Application of a systematic model selection process based on Akaike Information Criteria yields models from this family with improved performance. Furthermore, the robustness of the proposed family of models is assessed using published experimental data sets from a range of turbine designs, demonstrating the versatility of the proposed model family and model selection techniques.

Evaluating the Use of Leaned Stator Vanes to Produce a Non-Uniform Flow Distribution Across the Inlet Span of a Mixed Flow Turbine Rotor

Abstract Current trends in the automotive industry have placed an increased emphasis on downsized turbocharged engines for passenger vehicles. The turbocharger is increasingly relied upon to improve power output across a wide range of engine operating conditions, placing a greater emphasis on turbocharger off-design performance. An off-design condition of significant importance is performance at low turbine velocity ratios, since it is relevant to engine transient response and also to efficient energy extraction from pressure pulses in the unsteady exhaust flow. An increased focus has been placed on equipping turbochargers with mixed flow turbine rotors instead of conventional radial flow turbine rotors to improve off-design performance and to reduce rotor inertia. A recognized feature of a mixed flow turbine is the spanwise variation of flow conditions across the blade leading edge. This is a consequence of the reduction in leading edge radius from shroud to hub, coupled with the increasing tangential velocity of the flow due to conserved angular momentum as the radius decreases. The result is increasingly positive incidence toward the hub side of the leading edge. The resulting region of highly positive incidence at the hub produces separation from the suction surface and generates significant loss within the rotor passage. The aim of this study was to determine if the losses in a mixed flow turbine (MFT) could be reduced by the use of leaned stator vanes, which deliberately created a significant spanwise variation of flow angle between hub and shroud at rotor inlet, to reduce the positive incidence at the hub. The turbine performance with a series of leaned vanes was compared against that of a straight vane using a validated computational fluid dynamics (CFD) model. It was found that increasing vane lean improved turbine performance at all operating points considered. An increase of 3.2 percentage points in stage total-to-static efficiency was achieved at a key off-design operating point. Experimental testing of a set of leaned vanes and the baseline vanes confirmed the advantage of the leaned vanes at all operating points, with an increase in measured efficiency of 2.6 percentage points at the key off-design condition. Unsteady CFD models confirmed the same level of improvement at this operating point. The CFD and experimental results confirmed that the losses in an MFT can be reduced by the use of leaned stator vanes to shape the flow at rotor inlet.