Numerical Analysis of Labyrinth Seal Performance for the Impeller Backface Cavity of a Supercritical CO_(2) Radial Inflow Turbine

For a radial inflow turbine(RIT),leakage flow in impeller backface cavity has critical impacts on aerodynamic performance of the RIT and axial force acting on the RIT impeller.In order to control this leakage flow,different types of labyrinth seals are numerically studied in this paper based on a supercritical carbon dioxide(S-CO_(2))RIT.The effects of seal clearance and cavity outlet pressure are first analyzed,and the impacts of seal design parameters,including height,number and shape of seal teeth,are evaluated.Results indicate that adding labyrinth seal can improve cavity pressure and hence adequately inhibits leakage flow.Decreasing the seal clearance and increasing the height of seal teeth are beneficial to improve sealing performance,and the same effect can be obtained by increasing the number of seal teeth.Meanwhile,employing seals can reduce leakage loss and improve RIT efficiency under a specific range of cavity outlet pressure.Finally,the influences of seal types on the flow field in seal cavity are numerically analyzed,and results demonstrate that isosceles trapezoidal type of seal cavity has better sealing performance than triangular,rectangular and right-angled trapezoidal seal cavities.

Aerothermodynamic Design and Flow Characteristics for a S-CO_(2) Radial Inflow Turbine

In this paper,a radial inflow turbine is designed for the 150 kW S-CO_(2) Brayton cycle system,and flow characteristics and off-design performances are analyzed.The design results are accurate and high performances can be achieved for the S-CO_(2) power system,and the total-static efficiency of 86%and net output power about 285.2 kW can meet the design requirements of S-CO_(2) cycle system.The results of the flow characteristics show the streamlines of radial inflow turbine distribute uniformly,and the vortexes generated at the shroud of the blade suction surface have little influence on the turbine performances.The off-design performances show the total-static efficiency remains above 80%in the pressure ratio range of 1.6~2.9,and the output power and mass flow rate increase with the pressure ratio increasing.It is indicated that the designed turbine has excellent off-design performances and can meet the operation requirements.The study results can provide guidance for S-CO_(2) radial inflow turbine design and operation.

A Surrogate Model for a CAES Radial Inflow Turbine with Test Data-Based MLP Neural Network Algorithm

It is usually to conduct a full-scale three-dimensional flow analysis for a radial turbine to find a way to increase the efficiency of a Compressed Air Energy Storage(CAES)system.However,long solving time and huge consumption of computing resources become a major obstacle to the analysis.Therefore,in present study,a surrogate model with test data-based multi-layer perceptron(MLP)Neural Network is proposed to overcome the difficulty.Instead of complex flow field solving process,it provides reliable turbine aerodynamic performance and flow field distribution characteristics in a short solution time by“learning the measurement results”.The validation results illustrated that the predicted maximum relative errors of isentropic efficiency,corrected mass flow rate and corrected power are only 0.03%,0.22%and 0.26%respectively.The predicted flow distribution parameters in chamber,shroud cavity and outlet region of rotor are also basically consistent with the experimental results.In the chamber,it can be found that a pressure stagnation point is observed at circumferential angle of 270°when total pressure ratio is decreased.In the shroud cavity,obvious pressure variation is found near outlet of shroud cavity which although labyrinth seals exist.At outlet of rotor,obvious variations of velocity and pressure are found in the 0.0–0.4 and 0.6–0.8 of blade height.At the same time,obvious variations of velocity and pressure are found in the 0.0–0.4 and 0.6–0.8 of blade height and this is because the influence of upper passage vortex,lower passage vortex and end wall secondary flow.The present study can provide further reference for the dynamic performance evaluation of CAES radial inflow 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

A 2 MW gas turbine engine has been developed for the distributed power market.This engine features a 7:1 pressure ratio radial inflow turbine.In this paper,influences of various geometry features are investigated including turbine tip and backface clearances.In addition to the clearances,the effects of the inducer deep scallop and exducer rounded trailing edge are investigated.Finally,geometric features associated with a split rotor(separate inducer and exducer)are studied.These geometry features are investigated numerically using CFD.Part of the numerical results is also compared to experimental data acquired during engine test to validate the CFD results.