Radial Turbine Research Articles

A novel analysis framework for the organic Rankine cycle waste heat recovery system: From the viewpoint of turbine design

The turbine is crucial equipment in the ORC system, not only has a significant influence on system efficiency but also dominates the equipment investment costs. In this paper, a novel design framework for the radial inflow turbine is proposed, aiming to promote the standardization or serialization design of the ORC turbine, and the innovativeness of combining it into the system analysis is illustrated. The reliability of the design framework is examined by comparing with CFD simulation, nearly all of the deviations within ±5%. Better prediction accuracy can be achieved when R is close to 0.6, and the suitable value of α4 is 65° to realize a better turbine performance. Some other results reveal that the Ẇout has a positive proportional to r4 and Ma4, but ηts is not sensitive to them. Besides from the viewpoint of thermodynamics, the ηts of the turbine is hardly affected by the type of working fluid. For the case study, the turbine with R236ea has achieved the best matching degree with the heat source, which improves near 10% of the total output power for the MGT-ORC system. This paper gives new ideas for ORC turbine design and system analysis which contributes to promoting its application.

Axial Turbine Turbocharger for Charging a Lean-Burn Gasoline Engine

<div class="section abstract"><div class="htmlview paragraph">A single-stage turbocharger turbine is developed with the objective of enabling a gasoline spark-ignition engine to operate under lean-burn conditions with an air-to-fuel ratio of <b><i>λ</i></b>=2 in the range of the Worldwide Harmonized Light-Duty Vehicles Test Cycle. For this purpose, extensive 1-D engine simulations are performed using a combination of a simple compressor and simple turbine model as well as a combination of the stock compressor and a simple turbine model. The results show that an isentropic turbine efficiency of more than 70% over a wide operating range is required for the desired engine operation - especially with regard to the low-end-torque. Based on the crank-angle-resolved engine simulation data, turbine requirements are determined. Their evaluation shows that an axial turbine is a reasonable alternative to conventional radial turbines for this application. Next, a preliminary axial turbine is designed using 1-D/2-D design approaches. Then, the corresponding performance map is calculated by 3-D CFD simulations showing isentropic total-to-static turbine efficiencies of up to 77% over a wide operating range. Ultimately, the derived turbine performance map is implemented into the 1-D engine model and the valve train settings are optimized for this configuration to enhance the lean-burn performance further. The simulation results show a significantly extended <i>λ</i>=2 operating range in comparison to the stock turbine.</div></div>

Detailed transient assessment of a small-scale concentrated solar power plant based on the organic Rankine cycle

• New procedures for modeling the components of solar-ORC power plant are proposed. • A routine for optimizing the turbine geometry and evaluating its performance is used. • The power plant results are obtained by coupling the accurate components models. • A power plant continuously supplying electricity to remote communities is designed. • The low ODP and GWP refrigerant R1233zd(E) provided the best performance. Motivated by environmental issues and the needs of communities that live far from the electricity grid, this work presents an innovative methodology for modeling a small-scale concentrated solar power plant based on the organic Rankine cycle. An integrated simulation tool, which consists of accurate computational routines of the energy storage tank, parabolic trough collector, plate heat exchanger, finned air-cooled condenser, and inward-flow radial turbine, is developed. The components are modeled according to distributed models and the mean line method for the turbine in homemade codes to account for local property changes. The transient power plant performance is assessed by employing solar irradiation data of three locations that present mean direct normal irradiation rates of 6306, 4712, and 3220 Wh/m 2 .day. The following working fluids were considered: a low GWP and ODP refrigerant (R1233zd(E)), a natural one (R600a), and a high GWP fluid that is currently employed for such applications (R245fa). The smallest configuration that led to annual uninterrupted power production is a 565-m 2 collector and a 90-m 3 storage tank. The R1233zd(E) refrigerant presented the best overall performance by providing about 2% and 30% higher turbine power output, 3% and 29% higher turbine efficiency, and 4% and 36% higher ORC first-law efficiency than R245fa and R600a, respectively. The designed solar power plant generated 48.396 MWh/year of electricity and 80.621 MWh/year of cogeneration energy with R1233zd(E), which is enough to provide electricity and sanitary hot water to about 33 and 64 houses, respectively.

A GEOMETRIC DESIGN METHOD OF RADIAL INFLOW TURBINE FROM 0D TO 3D FOR ORGANIC RANKINE CYCLE MICRO POWER GENERATION

Radial turbine is an essential component of Organic Rankine Cycle system and requires a medium to high specific speed turbine. Radial turbine has a compact structure that can easily be made with current additive manufacturing technology if the 3D geometry of turbine components is known. Current researches only conduct 2D geometry design then import it into third-party software to construct the 3D geometry. This paper will explain design methodology to design radial inflow turbines from 0D until 3D using simple tools. The methods used to determine the geometry were based on Aungier, with modification in determining value of a, b, and c in nozzle design and A1 in Volute design to simplify the design process. The tools used in design were MS Excel and Autodesk Inventor. Rotor design starts with determining the two-dimensional parameters. All parameters are calculated based on the angle and velocities occurring in the velocity triangle at the inlet and outlet of the rotor using equations proposed by Aungier. Then, the straight, radial and quasi-normal lines of the blades are drawn based on governing equations. The transformation from 2D to 3D blade coordinates is done by using vector equations. The nozzle is designed by drawing the camber line profile and calculating the nozzle thickness to get the profile based on the governing equations given by Aungier. The volute dimensions are obtained by calculating the area of volute inlet passage and mean radius from mass and momentum conservation equations. A case study is shown in this paper with R134a as working fluid with the following range inlet conditions: mass flow rate at 1-2 kg/s, inlet pressure at 1.5 to 5 bar, inlet temperature at 80 to 130 °C, and power output target between 20 to 25 kW. The CFD results show that the designed turbine performs well with slight wake flow at the pressure side on the rotor inlet. A further study needs to be done in order to check the validity of this method by conducting analysis through experimental.

A novel variable geometry turbine achieved by elastically restrained nozzle guide vanes. Part II: Experimental evaluation

The current paper presents the performance results of a variable-flow turbocharger turbine, called the “elastically restrained guide vane (ERGV)” turbine, which is intended to provide an improvement over the current state-of-the-art turbochargers, namely, the variable geometry turbocharger (VGT). This paper is a continuation of the previous work and concentrates on the experimental testing of the ERGV turbine performance, as well as the corresponding effects on the mass flow characteristic as a result of operating the turbocharger in its ERGV mode compared with its operation as a traditional VGT. The effects of the ERGV application are demonstrated through the first experimental testing. In this preliminary attempt, the range of the mass flow rate is effectively enlarged, and the new mass flow characteristic lines can pass through the two and three lines separately of the original turbine for the two spring stiffness operations. The results of this study were encouraging with respect to the potential of ERGV to replace the traditional VGT in particular applications. Additionally, this paper compares the experimental mass flow charateristics with the computational fluid dynamics simulations in the radial turbine at the conditions of two spring stiffness. This preliminary comparison between numerical simulation and experimental data shows encouraging results.

Flow Characteristics and Loss Models of the Transonic Radial Turbine

A hydrogen turbo hybrid power system has the significant advantages of zero carbon emissions, high efficiency and high reliability. The need to increase the power density of hydrogen turbo hybrid power systems and improve the adaptability of turbines over a wide range of expansion ratios has encouraged the study of transonic turbines. This paper is aimed at analyzing the flow characteristics and developing the loss models of a transonic turbine. The main losses for a subsonic radial turbine are usually divided into four parts: incidence loss, passage loss, tip clearance loss and trailing edge loss. Nevertheless, when the expansion ratio of a turbine is greater than about 2.6, the turbine will choke and work in transonic conditions. A shock wave will occur at the trailing edge, which will cause a lot of losses. The loss caused by the shock wave at the trailing edge is ignored by previous loss models. This paper develops a shock wave-induced loss model to predict the performance in transonic conditions more accurately. With the developed shock wave-induced loss model, the predicted efficiency deviation in transonic conditions decreases from 10% to 3.5% maximally.

Blade thickness effects on viscous flutter in a radial turbocharger turbine

Transient blade loading limits the lifetime of turbocharger turbine blades. This study investigates the flutter instability of a radial turbocharger turbine blade under pulsating inlet conditions. The viscous Navier-Stokes equations with the SST-kω turbulence model and curvature correction were solved. A time-marching 3D finite volume method was used in the CFX17 CFD solver to model the vibrating blade in a traveling wave mode applying Fourier Transformation. For flutter calculations, moving boundaries with specified modal displacements were used. An area of instability was recognized on the suction-side of the rotor blade. FSI steady-state analysis was then performed to assess the effects of shock position and blade profile on the blade stability in the recognized vulnerable region. The results show that a higher trailing edge radius increases the stability and leads to a significant reduction of flutter risk whereas the maximum thickness and leading-edge radius do not notably affect the flutter occurrences.

Preliminary design and performance analysis of the liquid turbine for supercritical compressed air energy storage systems

• The preliminary design method and experiment of the liquid turbine is presented. • The predicted and experimental performance of the turbine validates the method. • Reasonable parameter ranges for liquid turbines are different from other turbines. Liquid turbines can replace throttling valves to recover waste energy and reduce vaporization in various industrial systems, such as liquefied natural gas, air separation, supercritical compressed air energy storage (SC-CAES) systems, et al. However, there were few studies about differences in the preliminary design method between general radial inflow turbines and liquid turbines. In this paper, a preliminary design method of liquid turbines was presented, and the performance of liquid turbines was predicted using CFD methods which were validated with experimental results. The efficiency of the designed liquid turbine was 92% and the output power was 65.7 kW. The performance of the turbine predicted by the preliminary method could agree with simulation results of prototype and model turbines near the design working condition, while there was a certain deviation when the flow rate was less than 70%. Through analyzing the presented preliminary design method, it could be found that distinctive differences in thermal properties of working fluids caused that typical design parameters for liquid turbines, like ratios of the blade height, the hub radius and the area, should be selected differently from empirical values for gas radial turbines. The results obtained in this paper could help guide the design of liquid turbines for various systems to promote energy conservation and improve system efficiencies significantly.

Choking dynamic of highly swirled flow in variable nozzle radial turbines

This paper presents the results of a computational investigation of the aerodynamic choking mechanism in a variable geometry turbine, which is widely used in automotive turbocharging. RANS and URANS numerical simulations were carried out for two stator vane positions, 10% and 30% opening at different speeds and several other operating conditions to observe the establishment of choked flow and rotor-stator interactions. When the stator vanes are at a closed position and high-pressure ratio, a shock wave is developed on the suction side of the stator vane; moreover, the effective area extends toward the rotor inlet. The shock losses of a fluid particle upstream of the rotor are related to the number of shocks that the particle goes through. The pressure losses are high close to the stator vanes and start to decrease toward the center of the vaneless space until they start to increase close to the rotor. The interaction between the rotor and stator creates shocks waves with an intensity depending on the rotor's leading edge position and the rotational speed. The pressure profile of the rotor blade under this circumstance is also affected, especially at high rotational speeds, when important load fluctuations may affect the integrity of the blades.

Energy loss of radial inflow turbine for organic Rankine cycle using mixture based on entropy production method

The radial inflow turbine is the core component of the organic Rankine cycle(ORC) system. Based on the internal flow field of the turbine analyzed by computational fluid dynamics (CFD), the energy dissipation of a radial inflow turbine with variable guide vane is determined by the entropy production analysis method. In the presented work, the mixture of R245fa/R134a is selected as the working fluid, and the effects of tip clearance and mixing ratio on the flow loss characteristics are investigated. The results show that the high entropy production region in the stator is caused by leakage vortex and shock phenomenon, while the passage vortex and leakage vortex are the reasons for the high loss area in the rotor. The total volume entropy production of rotor is mainly composed of the passage zone, which is significantly higher than that of the stator. As the tip clearance increases from 3% to 10%, the total entropy production of stator and rotor increases by 54.5 and 161.7% respectively, and the output power and isentropic efficiency of the turbine decrease by 14.7% and 14.6% respectively. With the increase of R245fa mass fraction, the total volume entropy production of the stator and rotor decreases linearly. Compared with R134a, the turbine isentropic efficiency of R245fa increases by 3.1%.

Turbocharger Radial Turbine Response to Pulse Amplitude

Abstract Under on-engine operating conditions, a turbocharger turbine is subject to a pulsating flow and, consequently, experiences deviations from the performance measured in gas-stand flow conditions. Furthermore, due to the high exhaust gases temperatures, heat transfer further deteriorates the turbine performance. The complex interaction of the aerothermodynamic mechanisms occurring inside the hot-side, and consequently the turbine behavior, is largely affected by the shape of the pulse, which can be parameterized through three parameters: pulse amplitude, frequency, and temporal gradient. This paper investigates the hot-side system response to the pulse amplitude via detached eddy simulations (DES) of a turbocharger radial turbine system including the exhaust manifold. First, the computational model is validated against experimental data obtained in gas-stand flow conditions. Then, two different mass flow pulses, characterized by a pulse amplitude difference of ≈5%, are compared. An exergy-based post-processing approach shows the beneficial effects of increasing the pulse amplitude. An improvement of the turbine power by 1.3%, despite the increment of the heat transfer and total internal irreversibilities by 5.8% and 3.4%, respectively, is reported. As a result of the higher maximum speeds, internal losses caused by viscous friction are responsible for the growth of the total internal irreversibilities as pulse amplitude increases.

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.

A comprehensive review of micro-scale expanders for carbon dioxide related power and refrigeration cycles

• Developments of micro-scale expanders in carbon dioxide cycles are summarized. • Comparison between turbines and volumetric expanders are analysed. • Relations between flow rate, pressure ratio and rotational speed are highlighted. • Challenges and future development directions for expanders outlined. In recent decades, the carbon dioxide cycles, including supercritical carbon dioxide cycle, transcritical carbon dioxide Rankine cycle and refrigeration cycle, have been proven effective due to the high efficiency and compact structure, and received increasing interests. The performance of the expander in the power cycles, particularly in micro-scale applications, is one of the essential components that determine the cycle performance and still remains a significant challenge. This paper presents a critical overview of micro-scale (<200 kW) expanders for carbon dioxide cycles. Five types of expanders, including axial and radial turbines (dynamic expanders), scroll, piston and vane expanders (volumetric expanders), are evaluated from experimental and numerical aspects. Expansion mechanisms, rotational speed, isentropic efficiency, pressure ratio and mass flow rate are considered. The review suggests that the volumetric expanders stand certain advantages in the micro-scale carbon dioxide cycles due to the more suitable rotational speed and potentially less leakage. For all expanders, internal and external leakages remain a vital challenge that greatly reduce their performance and efficiency, which urgently needs to be addressed.

CFD Simulation and Flow Study of a Velocity Compounded Radial Re-Entry Turbine - Elektra

In order to meet the targets set out in the Paris climate agreement of 2015, the energy sector needs to be restructured. In Germany for example the goal is to move out of both nuclear and coal-fired power. In order to fulfil more demanding energy requests alternative sources of energy must be found and made available. One component is the usage of Waste Heat Recovery. This paper deals with the evaluation simulation of an Elektra turbine, which concept is a velocity compounded radial re-entry single wheel turbine. Based on the first turbine design, multiple simulations were carried out in order to maximize the efficiency. With these simulations, optimization opportunities are described and identified. The paper concludes with a comparison of the results achieved by numerical simulation and on the experimental test bench. The main focus for this paper is to analyze the actual flow phenomena to identify possibilities for further improvements. All simulations were calculated with the commercial software FINETM/TURBO 15.1.

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.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ И ЧИСЛЕННАЯ ОЦЕНКА ДОЛГОВЕЧНОСТИ РАДИАЛЬНЫХ РАБОЧИХ КОЛЕС ТУРБОМАШИН

The radial blade discs are nominally designed to be cyclically symmetrical. But the vibration characteristics of all the ra-dial blades on the disc are slightly different due to manufacturing tolerances, variations in material properties and wear during operation. These small changes break the cyclic symmetry, break the pairs of eigenvalues and affect the durability of the radial impellers of turbomachines. In further work, the designs of such systems may fail before the estimated resource or service life. Therefore, when designing, manufacturing, and operating turbomachines, it is necessary to understand the effect of parameter mistuning to manage the resource and ensure the required level of strength, reliability, and durability of radial turbomachines. This study proposes a technique for mathematical modeling and prediction of high-cycle fatigue life of radial wheels tur-bines, taking into account dynamic loading. Numerical assessment of durability was performed on the example of a radial wheel with 10 blades manufactured by Schiele (Germany). The results were obtained when calculating the dynamic load in the MATLAB program and high-cycle fatigue in the ANSYS program.

Numerical Investigation on the Effect of Cold Climate on the Thermodynamic Behavior and Exergy Distribution in the Two-Stage Radial Turbine

Numerical Investigation on the Effect of Cold Climate on the Thermodynamic Behavior and Exergy Distribution in the Two-Stage Radial Turbine

Effects of Various Geometric Features on the Performance of a 7:1 Pressure Ratio Deeply Scalloped and Split Radial Turbine in a Gas Turbine Engine

Effects of Various Geometric Features on the Performance of a 7:1 Pressure Ratio Deeply Scalloped and Split Radial Turbine in a Gas Turbine Engine

Numerical Analysis of the Effects of Different Rotor Tip Gaps in a Radial Turbine Operating at High Pressure Ratios Reaching Choked Flow

Numerical Analysis of the Effects of Different Rotor Tip Gaps in a Radial Turbine Operating at High Pressure Ratios Reaching Choked Flow

Numerical and Experimental Investigation of a Velocity Compounded Radial Re-Entry Turbine for Small-Scale Waste Heat Recovery

The energy industry must change dramatically in order to reduce CO2-emissions and to slow down climate change. Germany, for example, decided to shut down all large nuclear (2022) and fossil thermal power plants by 2038. Power generation will then rely on fluctuating renewables such as wind power and solar. However, thermal power plants will still play a role with respect to waste incineration, biomass, exploitation of geothermal wells, concentrated solar power (CSP), power-to-heat-to-power plants (P2H2P), and of course waste heat recovery (WHR). While the multistage axial turbine has prevailed for the last hundred years in power plants of the several hundred MW class, this architecture is certainly not the appropriate solution for small-scale waste heat recovery below 1 MW or even below 100 kW. Simpler, cost-effective turbo generators are required. Therefore, the authors examine uncommon turbine architectures that are known per se but were abandoned when power plants grew due to their poor efficiency compared to the multistage axial machines. One of these concepts is the so-called Elektra turbine, a velocity compounded radial re-entry turbine. The paper describes the concept of the Elektra turbine in comparison to other turbine concepts, especially other velocity compounded turbines, such as the Curtis type. In the second part, the 1D design and 3D computational fluid dynamics (CFD) optimization of the 5 kW air turbine demonstrator is explained. Finally, experimentally determined efficiency characteristics of various early versions of the Elektra are presented, compared, and critically discussed regarding the originally defined design approach. The unsteady CFD calculation of the final Elektra version promised 49.4% total-to-static isentropic efficiency, whereas the experiments confirmed 44.5%.