Search Results (150)

This study aims to elucidate the mechanisms by which tip seal leakage flow induces steam excitation, thereby enhancing the operational safety of steam turbines. Using numerical simulations, it investigates the detailed characteristics of the flow field in the turbine tip seal cavity. By introducing Boundary Vorticity Flux (BVF) into the tip seal flow field, this research explores the relationship between leakage vortex structures in non-uniform flow fields at the blade tip and the resulting steam excitation forces. The results demonstrate that, during eccentric rotor operation, the extent and intensity of vortices within the seal cavity vary, lead to changes in the BVF distribution along the shroud surface, which in turn alter the tangential forces and induce variations in lateral excitation force at the blade tip. Additionally, the non-uniform flow in the tip seal clearance induces circumferential pressure variations across the shroud, leading to adjustments in radial excitation force at the blade tip. Full article

In order to study the influence of split blades on the turbine force characteristics and fluid–structure coupling characteristics of pumps, this paper selected the IS 80-50-315 centrifugal pump, used as a reverse-acting hydraulic turbine, as the research object, optimized the original pump-acting turbine impeller, and adopted different combinations of long and short blades. Based on the SIMPLE algorithm and RNG k–ε turbulence model, a complete three-dimensional unsteady numerical simulation was conducted on the internal flow field of the pump-turbine. The results show that the split blades reduce the radial and axial forces. The deformation patterns of rotor components in the two pump types used as turbine models were similar, with deformation gradually decreasing from the inlet to the outlet of the impeller. The equivalent stress distribution law of the rotor components of the two pump turbine models has also been found to be similar, with the maximum stress occurring at the connection between the blades and the front and rear cover plates and the minimum stress occurring at the outlet area of the impeller and the maximum shaft diameter of the pump shaft. The maximum deformation and stress of the rotor components in the split blade impeller model were smaller than those in the original impeller model. Full article

Organic Rankine cycles (ORCs) are increasingly employed in power plants to recover waste energy and reduce environmental impacts. The radial turbine, a critical ORC component, experiences flow losses influenced by design parameters such as the rotor blade and stator vane numbers. Traditional empirical correlations developed for air often lack accuracy for ORCs due to differences in fluid properties and flow dynamics. This study uses advanced CFD models to evaluate and refine these correlations for ORC applications. For the ORC, waste heat from the Ha’il Cement Company in Saudi Arabia is used as the heat source. The CFD model was validated with experimental data and showed strong agreement, with a maximum deviation of 5.12% in mass flow rate and 3.97% in turbine outlet temperature. The results show that reducing vane numbers from 17 to 11 increased turbine power, efficiency, and thermal efficiency by 34.8%, 4.17%, and 35.16%, respectively. However, further reduction caused performance deterioration due to high Mach numbers and flow recirculation. Increasing the rotor blade number to 20 improved performance, but numbers beyond 20 caused declines. Among empirical correlations, Rohlik’s correlation with 20 blades achieved optimal outputs of 13.54 kW turbine power, 75% turbine efficiency, and 6.98% thermal efficiency. Further optimization yielded an ORC configuration with 11 vanes and 20 blades, achieving superior performance: 16 kW turbine power, 77% turbine efficiency, and 9% thermal efficiency. Full article

The combustion of hydrogen increases the water content of the combustion products, affecting the aerodynamic performance of turbines using hydrogen as a fuel. This study aims to design a radial turbine using the differential evolution (DE) algorithm to improve its characteristics and optimize its aerodynamic performance through an orthogonal experiment and analysis of means (ANOM). The effects of varying water content in combustion products, ranging from 12% to 22%, on the performance of the radial turbine are also investigated. After optimization, the total–static efficiency of the radial turbine increased to 89.12%, which was 1.59% higher than the preliminary design. The study found that flow loss in the impeller primarily occurred at the leading edge, trailing edge, and the inlet of the suction surface tip and outlet. With a 10% increase in water content, the enthalpy dropped, Mach number increased, and turbine power increased by 4.64%, 1.71%, and 2.41%, respectively. However, the total static efficiency and mass flow rate decreased by 0.71% and 2.13%, respectively. These findings indicate that higher water content in hydrogen combustion products enhances the turbine’s output power while reducing the combustion products’ mass flow rate. Full article

This study investigates the performance of a centrifugal radial turbine within an Organic Rankine Cycle (ORC) system, focusing on operation beyond the design point due to variable waste heat sources. With the goal of integrating the turbine into optimal ORC operating conditions, its performance was analyzed using R245fa as the working fluid over three stages with varying numbers of blades. A detailed computational analysis was performed using Ansys CFX software (Version 2020 R2) with the k-ω SST turbulence model using thermodynamic data from the NIST Refprop database. The results showed significant discrepancies when operating beyond the design point. At an inlet pressure of 780 kPa, the turbine internal power was calculated to be 120 kW—double the manufacturer’s maximum of 60 kW—and the mass flow rate exceeded 6 kg/s compared to the design value of 2.72 kg/s. These results highlight the challenges of adapting the turbine to fluctuating waste heat conditions, as factors such as tip clearance, blade geometry, and high outlet pressure have a significant impact on efficiency and system performance. Full article

The worldwide concern regarding the harmful effects of old polluting and toxic propellants has led to increased interest in new, green propellants and higher efficiency thrusters. This fact requires that a new generation of turbopumps, fit for these propellants, is developed. This paper focuses on the design of a radial inflow turbine, which was developed to power a single-shaft turbopump system for a 30 kN upper stage expander cycle thruster engine. The objective was to create a high-efficiency, compact, cheap-to-manufacture, 3D-printable turbine suitable to simultaneously power the methane and Oxygen pumps that feed the thruster. The total power consumed by the pumps for which this turbine was designed is 152 kW. The solution proposed in this paper includes measures such as elimination of the bladed diffuser, which was carried out to reduce the weight and the overall dimensions of the turbine. Comparing it with an axial turbine with the same power output, it has lower overall dimensions because it does not require a direction change at the inlet to the turbine bladed components, it does not require a stator to work, and its casing has a conical shape and is not cylindrical like the axial construction one. The proposed design has been analysed by CFD, which revealed that it can power the pumps. Analysis performed in off-design conditions indicated that the turbine has the best efficiency if the rotation speed and mass flow are varied at the same time. A breadboard model of the turbopump for which the turbine in this paper has been designed has been built using plastic and tested at pressures up to 6 bars using compressed air. The results indicate that above 1.5 bars of inlet pressure the turbine can overcome the internal resistances of the components and the rotor starts to spin. No indication of imbalance of the rotor was observed at maximum test pressure. Two configurations of the seals between the turbine and the adjacent pump have been tested, indicating that labyrinth seals must be doubled by floating ring seals. Full article

Few universities in the world conduct experimental research on high-speed, high-power turbomachinery. The Purdue High-Speed Compressor Research Laboratory has a longstanding tradition of partnering with industry sponsors to perform high-TRL (technology readiness level) experiments on axial and radial compressors for aerospace applications. Early work in the laboratory with Professor Sanford Fleeter and Professor Patrick Lawless involved aeromechanics and the addition of a multistage axial compressor facility to support compressor performance studies. This work continues today under the guidance of Professor Nicole Key. While other universities may operate a single-stage transonic compressor or a low-speed multistage compressor, the Purdue 3-Stage (P3S) Axial Compressor Research Facility provides a unique environment to understand multistage effects at speeds where compressibility is important. Over the last two decades, several areas of important research within the gas-turbine engine industry have been explored: vane clocking, stall/surge inception, tip-leakage/stator-leakage (cavity leakage) flow characterization, and forced response, to name a few. This paper addresses the different configurations of the facility chronologically so that existing datasets can be matched with correct boundary conditions and provides an overview of the different upgrades in the facility as it has developed in preparation for the next generation of small-core compressor research. Full article

In this study, a thorough experimental investigation of the synchronous blade vibrations of a radial turbine is performed for different IGV configurations. First, the blade modes are measured experimentally and calculated numerically. Subsequently, the vibrations are recorded with two redundant measurement systems during real operation. Strain gauges were applied on certain blades, while a commercial blade-tip-timing system is used for the measurement of blade deflections. The experimentally determined vibration properties are compared with numerical estimations. Initially, the vibrations recorded with the “nominal” IGV were presented. This IGV primarily generates nodal diameter (ND) 0 vibrations. Subsequently, the impact of two different IGV configurations is examined. First, a mistuned IGV, which has the same number of vanes as the “nominal” IGV is examined. By intentionally varying the distance between the vanes, additional low engine order excitations are generated. Moreover, an IGV with a higher number of vanes is employed to induce excitations at higher frequency modes and ND6 vibrations. Certain vibrations are consistently measured across all IGV configurations, which cannot be attributed to the spiral turbine casing. In addition, a turbine–compressor interaction has been observed. Full article

Turbine blades for modern turbomachinery applications often exhibit complex twisted designs that aim to reduce aerodynamic losses, thereby improving the overall machine performance. This results in intricate internal cooling configurations that change their spanwise orientation with respect to the rotational axis. In the present study, the local heat transfer in a generic two-pass turbine cooling channel is investigated under engine-similar rotating conditions ($Ro=\{0\dots 0.50\}$) through the transient Thermochromic Liquid Crystal (TLC) measurement technique. Three different angles of attack ($\alpha =\{-{18.5}^{°};+8^{°};+{46.5}^{°}\}$) are investigated to emulate the heat transfer characteristics in an internal cooling channel of a real turbine blade application at different spanwise positions. A numerical approach based on steady-state Reynolds-averaged Navier–Stokes (RANS) simulations in ANSYS CFX is validated against the experimental method, showing generally good agreement and, thus, qualifying for future heat transfer predictions. Experimental and numerical data clearly demonstrate the substantial impact of the angle of attack on the local heat transfer structure, especially for the radially outward flow of the first passage, owing to the particular Coriolis force direction at each angle of attack. Furthermore, results underscore the strong influence of the rotational speed on the overall heat transfer level, with an enhancement effect for the radially outward flow (first passage) and a reduction effect for the radially inward flow (second passage). Full article

Brush seals are extensively used in rotating equipment, such as gas turbines and compressors, providing effective sealing while accommodating radial, axial, and angular movements between components. In this study, the performance of brush seals with and without clearances was predicted through axisymmetric 2D computational fluid dynamic (CFD) simulations using a porous media model. Because the accurate modeling of a brush seal requires the appropriate porosity to be determined and the flow resistance to be calculated, a porosity correction was performed based on the brush seal’s geometry and pressure ratio. The corrected porosity was then used to calculate the flow resistance and the leakage flow rate was predicted. Based on the results, the corrected porosity significantly improved the accuracy of the previously unreliable leakage flow rate predictions, regardless of the presence of clearances. For cases with a clearance, the blow-down effect was determined through CFD simulations for the given geometry and was compared with experimental data. The leakage flow rate predictions were highly accurate, with a relative error of less than 5% across a pressure ratio range of 1.5–4. Full article

Enhancing thermal efficiency and minimizing weight are prevailing issues in aero engines. Owing to its hollow structure, the twin-web turbine disc exhibits remarkable weight reduction properties, while its enhanced cooling constitutes a novel challenge. In this study, a twin-web turbine disc cavity system is numerically investigated. To enhance the cooling effect and minimize pressure loss, a multi-objective genetic algorithm and Kriging surrogate model are employed to optimize the radial height of the pre-swirl nozzle and receiver hole in the disc cavity system. The results indicate that the overall performance of Opt-3, derived from the Technique for Order Preference by Similarity to the Ideal Solution method within the Pareto frontier, is superior. This configuration achieves a uniform low distribution of rotor temperatures while maintaining moderate pressure losses. Notably, the maximum temperature is reduced by 21.1 K compared to the basic model, with pressure losses remaining largely unchanged. Additionally, an increase in the flow ratio leads to a reduction in both the maximum temperature and average temperature of the back web while simultaneously increasing the temperature of the front web and augmenting pressure losses. However, it is important to note that the degree of variation in these parameters diminishes with increasing flow ratios. Full article

Momentum diffusion and kinetic energy transfer in turbomachinery have always been significant issues, with a considerable impact on the performance of the bladeless Tesla turbine. This radial turbine shows high potential for various energy applications, such as Organic Rankine Cycle or combined heat and power systems. Analyzing the flow inside the gap between the corotating disks of the Tesla turbine presents challenges due to several factors, including submillimeter length scales, variations in flow cross-section, interactions of body forces arising from rotation with turbulence, interactions between the turbine’s inlet nozzles and rotor, and moving walls. General design parameters, e.g., number of nozzles, also pose a challenge in order to achieve the full potential of this turbine. In this research, two different variants of the supply system are considered with six and forty nozzles. To minimize computational expenses, a portion of the entire domain is considered. The flow in each domain, consisting of one inlet nozzle and a segment of one gap between the disks, is examined to reveal the complexity of flow structures and their impact on the Tesla turbine performance. Large Eddy Simulation (LES) with the Smagorinsky subgrid-scale model is used to verify the results of the k-ω Shear-Stress Transport (SST) turbulence model in the first case study with six nozzles. Analyzing the results indicates that the k-ω SST model provides valuable insights with appropriate accuracy. The second case study, with forty nozzles, is simulated using the k-ω SST turbulence model. The research compares flow structure, flow parameters, and their impact on the system’s performance. From the comparison between the k-ω SST turbulence model and LES simulation, it was observed that although the k-ω SST model slightly overestimates the general parameters and damps fluctuations, it still provides valuable insights for assessing flow structures. Additionally, the mesh strategy is described, as the LES requirements make this simulation computationally expensive and time-consuming. The overall benefits of this method are discussed. Full article

Twin-web turbine discs have been the subject of research recently in an effort to lighten weight and boost aeroengine efficiency. In the past, the cooling design of turbine discs was generally constrained to optimizing a single structural parameter, which hindered the enhancement of the optimization impact. Therefore, this article proposes a twin-web turbine disc system with a high radius pre-swirl. Driven by the database produced through the numerical simulation, a backpropagation network surrogate model is constructed, and the angles of the pre-swirl nozzles and receiver holes are optimized by a genetic algorithm to enhance the cooling efficiency of the turbine disc. Evaluation was based on the highest disc temperature, disc temperature uniformity, and Nusselt number. The results demonstrate that the suggested surrogate model effectively optimizes the structural characteristics of the twin-web turbine disc by aiming for the specified cooling performance indexes. The cooling effect of the turbine disc is significantly improved in different operating environments. Specifically, the optimized model produces the largest temperature drop in the disc rim temperature. Both axial and radial temperature uniformity have led to a notable enhancement. The alteration in coolant flow within the cavity results in a notable decrease in the area with low heat transfer efficiency and a substantial increase in the Nusselt number. Full article

As a special type of through-flow device, bulb turbine pumps have been widely used in the Eastern Route of the South-to-North Water Diversion Project due to their compact structure, flexible installation process, easy maintenance, high efficiency, and strong adaptability. Therefore, structural improvements to enhance their safety and stability through fluid–structure interaction analysis have significant engineering value. This paper conducts static and transient fluid–structure interaction analyses of the bulb turbine pump structure. The results show that the rotor structure experiences the greatest deformation under low-flow conditions, with maximum deformation (2.13 mm) occurring at the leading edge of the impeller inlet and decreasing radially along a gradient distribution. The damping effect of water changes the mode shapes of the rotor structure, and although the vibration modes under wet conditions are similar to those in the air, the frequencies decrease to varying degrees. In transient analyses under different conditions, the total deformation of the rotor system is greater than in static analyses, showing significant regularity. Under low-flow conditions, the deformation of the pressure surface at the inlet and outlet of the blade tip is greater than that of the suction surface, with a maximum total deformation of 3.656 mm. The maximum total deformation under design flow is 3.337 mm; under high flow, it is 2.646 mm. The total deformation of the casing mainly occurs on both sides of the internal bulb body bottom support, with a maximum deformation of 2.0355 mm and an equivalent stress maximum of 44.848 MPa. The equivalent stress and total deformation distribution of the support structure are similar, located at the top support and trailing edge, with a maximum value of 22.94 MPa at the trailing edge. The research results provide technical references and theoretical foundations for the structural optimization of bulb turbine pumps. Full article

Due to the existence of an inlet elbow, transmission shaft, and other structural components, the inflow of axial-flow pumps as turbines (PATs) becomes non-uniform, resulting in the complexity of internal flow and adverse effects such as structural vibration. In this paper, numerical methods were employed to explore the non-uniform inflow effects on impeller forces and internal flow field characteristics within an axial-flow PAT. The study results indicated that non-uniform inflow caused uneven pressure distribution inside the impeller, which leads to an imbalance in radial forces and offsetting the center of radial forces. With an increasing flow rate, the asymmetry of radial forces as well as the amplitude of their fluctuations increased. Non-uniform inflow was found to induce unstable flow structures inside the impeller, leading to low-frequency, high-amplitude pressure fluctuations near the hub. Using the enstrophy transport equation, it was shown that the relative vortex generation term played a major part in the spatiotemporal evolution of vortices, with minimal viscous effects. Full article