Tesla Turbine Research Articles

Buoyancy Effect on the Unsteady Diffusive Convective Flow of a Carreau Fluid Passed over a Coated Disk with Energy Loss

The unsteady flow of a Carreau fluid over a coated disk under the simultaneous effects of a thermal and concentration field with buoyancy forces is reported. The time-dependent diffusive stream of a Carreau fluid over a conducting coated disk is carried out with energy loss. The time-dependent partial differential equations are first converted into a scheme of ordinary differential equations by the appropriate transformations and are then solved by shooting method. Significant results for speed, hotness and concentration profiles are revealed and deliberated by the graphical outcomes. The numerical values of skin friction suggest that the viscoelastic parameter of the Carreau fluid causes a reduction in the skin friction coefficient due to the coated surface, but the Nusselt and Sherwood numbers increase with the rise of the viscoelastic parameter of the Carreau fluid because of the coated surface. The present model is useful in the field of mechanical engineering to design a tesla turbine for the flow of viscous fluid.

A new type of bladeless turbine for compressed gas energy storage system.

Nowadays, energy storage engineering is an important means to relieve the problem of energy shortage. In this investigation, we design a kind of vaneless turbine originating from a Tesla turbine with a diameter and an air gap of 250 mm and 0.5 mm, respectively. Importantly, such a vaneless turbine removes the feature of an air outlet in the middle and adopts other ways of entering and leaving on both sides, so as to strengthen the rotor, because there is no need for a large hole in the middle of the rotor. Furthermore, the rotor dynamics characteristics of the vaneless turbine are calculated by six different modes. We also obtain the critical speed in different modes. Moreover, the flow field performances, such as the velocity and pressure of fluid (air), are investigated using the finite element simulation method. In addition, the bench test is built to obtain the output characteristics of a vaneless turbine. The maximum output torque is about 5.56 Nm at 992 rpm, and the maximal rotational speed of the vaneless turbine can reach 3200 rpm. Our work provides new ideas and guidance for the design and research of the new generation of the vaneless turbine.

Dynamic Modeling and Investigation of a Tunable Vortex Bladeless Wind Turbine

This paper investigates the dynamics of an electromagnetic vortex bladeless wind turbine (VBWT) with a tunable mechanism. The tunable mechanism comprises a progressive-rate spring that is attached to an oscillating magnet inside an electromagnetic coil. The spring stiffness is progressively adjusted as the wind speed changes to tune the turbine fundamental frequency to match the shedding frequency of the vortex-induced vibration (VIV) due to the wind flow crossing over the oscillating mast. Coupled nonlinear equations of motion of the tunable turbine are developed using the lumped-mass representation and Lagrange formulation. Numerical results show that the tunable turbine performs effectively beyond a threshold wind speed. An analytical expression of the threshold speed is derived based on the mechanical fundamental frequency of the turbine. The analytical results are in reasonable agreement with the numerical evaluations. At a given wind speed past the threshold, the tunable turbine has an optimum spring stiffness at which the output power is maximum. Numerical studies also show that the output power of the 2 m long tunable turbine is tens of times larger in comparison to a conventional bladeless turbine. For example, at a wind speed of 4.22 m/s, the output rms power of the tunable turbine is around 1105 mW versus 17 mW of the conventional VBWT. The power can be further maximized at an optimum external load. This research work demonstrated the feasibility and merits of the proposed tunable mechanism to enhance the overall performance of the bladeless wind turbine.

Influence of operational parameters on the performance of Tesla turbines: Experimental investigation of a small-scale turbine

Tesla turbines can be employed as small-scale turbines to recover waste energy in several industrial applications. However, there is no consensus on the turbine efficiency as experimental studies show significantly lower values than those obtained by analytical and CFD approaches. The present work addresses that question by performing a systematic literature review (SLR) on Tesla turbines, comparing the efficiency values reported by experimental and simulation works. To validate the SLR findings an experimental small-scale air driven Tesla turbine was built. The Design of Experiments (DoE) methodology was applied to understand the effects of selected independent variables on the turbine output power and mechanical efficiency. Inlet air pressure, temperature, and rotational speed were chosen as controllable factors of a Central Composite Design applied to the prototype of < 1 kW output power. The results indicate a 5% efficiency increase when inlet pressure increases 1 bar, on average. In the SLR, the average efficiency of 40%–60% was reported by simulation works, while experimental articles reported maximum efficiencies of 20%, on average. The experimental turbine analyzed in this paper presented a maximum efficiency of 14.2% ± 0.4% at 3 barg and 4,000 rpm, agreeing with other experimental studies.

Performance Assessment of Tesla Expander Using 3D Numerical Simulation

Abstract Bladeless or Tesla turbines consist of several flat parallel disks mounted on a shaft with a narrow gap between them. The analytical solution of Navier-Stokes equations for the flow between disks has been extensively studied in the past. However, there is a significant impact of the stator exit-flow conditions on the performance and flow behavior inside the rotor of the Tesla turbine. There has been limited research on flow characterization and performance evaluation of stator-rotor interaction of the Tesla expander using 3D numerical simulation. The challenge arises due to a very high aspect ratio of the Tesla rotor (diameter to gap ratio &amp;gt; 1000). 3D numerical modeling with a hexahedral mesh of the nozzle/stator with the commercial software is presented. The simulation is performed for a wide range of inlet pressures and rotational speeds. This work focuses on the stator performance, the stator-rotor interaction, the rotor entry losses due to disk tip, the rotor tip velocity ratio and the degree of reaction on the performance of the Tesla expander.The peak efficiency of 58% is predicted for 3 bar inlet pressure and a rotational speed of 30000 rpm for a 3 kW machine with air as a working fluid. The 3D numerical analysis provides insights on flow characterization, mainly stator-rotor interaction and flow between disks at different mass flows. Numerical results are also compared with experimented test results performed on a 100-W and a 3-kW air expander.

Analysis and design of the gas generator multifunctional bulkhead considering the thermal and structural loads

The operation of gas generators brings relatively high thermo-mechanical loads on the gas generator structure. The objective of this article is to determine the operating conditions, in terms of mechanical loads at extremely high temperatures in very limited and narrow space, of a multifunctional bulkhead for application on specific kinds of gas generators with back-to-back rotor concept. The paper contains numerical analysis and experimental investigation for determining the loads and behavior of the structure. Numerical analysis indicates that there is significant influence of the Tesla turbine effect on flow parameters. Also, uneven pressure distribution and significant thermal loads are identified. With experimental investigation and subsequent exploitation tests, it was concluded that the presented methodology identifies the operating conditions, truthfully simulates the bulkhead stress state and deformations and that the presented design solution satisfied all demands. Regarding results obtained by these numerical simulations, the innovative design solution for the multifunctional bulkhead was proposed.

Reimagining Prosthetic Control: A Novel Body-Powered Prosthetic System for Simultaneous Control and Actuation

Globally, the most popular upper-limb prostheses are powered by the human body. For body-powered (BP) upper-limb prostheses, control is provided by changing the tension of (Bowden) cables to open or close the terminal device. This technology has been around for centuries, and very few BP alternatives have been presented since. This paper introduces a new BP paradigm that can overcome certain limitations of the current cabled systems, such as a restricted operation space and user discomfort caused by the harness to which the cables are attached. A new breathing-powered system is introduced to give the user full control of the hand motion anywhere in space. Users can regulate their breathing, and this controllable airflow is then used to power a small Tesla turbine that can accurately control the prosthetic finger movements. The breathing-powered device provides a novel prosthetic option that can be used without limiting any of the user’s body movements. Here we prove that it is feasible to produce a functional breathing-powered prosthetic hand and show the models behind it along with a preliminary demonstration. This work creates a step-change in the potential BP options available to patients in the future.

Exergy Efficiency and COP Improvement of a CO2 Transcritical Heat Pump System by Replacing an Expansion Valve with a Tesla Turbine

The heat pump system has been widely used in residential and commercial applications due to its attractive advantages of high energy efficiency, reliability, and environmental impact. The massive exergy loss during the isenthalpic process in the expansion valve is a major drawback of the heat pump system. Therefore, the Tesla turbine exergy analysis in terms of transiting exergy efficiency is investigated and integrated with the transcritical heat pump system. The aim is to investigate the factors that reduce exergy losses and increase the coefficient of performance and exergy efficiency. The contribution of this paper is twofold. First, a three-dimensional numerical analysis of the supercritical CO2 flow simulation in the Tesla turbine in three different geometries is carried out. Second, the effect of the Tesla turbine on the coefficient of performance and exergy efficiency of the heat pump system is investigated. The effect of the rotor speed and disk spacing on the Tesla turbine power, exergy loss, and transiting exergy efficiency is investigated. The results showed that at a lower disk spacing, the turbine produces higher specific power and transiting exergy efficiency. In addition, the coefficient of performance (COP) and exergy efficiency improvement in the heat pump system combined with the Tesla turbine are 9.8% and 28.9% higher than in the conventional transcritical heat pump system, respectively.

Energy analysis of a detonation combustor with a bladeless turbine, a propulsion unit for subsonic to hypersonic flight

This paper details an energy conversion unit for the combined power extraction and thrust increase from high subsonic to hypersonic flows. The energy transfer is achieved through a wavy hub surface that promotes shocks and expansion fans. First, a design procedure and the non-dimensional steady-state performance characteristics (the reduced torque, non-dimensional mass flow, and non-dimensional speed) are presented (including an exergetic analysis) at on– and off-design conditions through time-averaged Reynolds Averaged Navier Stokes simulations. A cycle analysis was performed on a Mach 3 vehicle to demonstrate the feasibility of this technology. Second, energy extraction is achieved from the highly unsteady exhaust of rotating detonation combustors without needing an additional intermediate diffuser or nozzle. The rotating boundary conditions were computed from a reactive unsteady simulation. The influence of three shock parameters (pressure ratio across the shock, shock wave Mach number, and the number of waves) is investigated through a sensitivity study to assess the robustness of the new device. Furthermore, depending on the sense of rotation of the bladeless turbine relative to the rotation of the incoming shock and the helix angle, we can define two different modes of operation in which power extraction was achieved, namely, the shock mode and reversed mode.

Waste heat recovery using Tesla turbines in Rankine cycle power plants: Thermofluid dynamic characterization, performance assessment and exergy analysis

• Compressible-turbulent flow physics of wet steam in Tesla turbines is studied to assess power recovery. • Scaling laws are modified by introducing a novel thermal parameter ( Ts ). • Optimal rotor dimensions in terms of rotor and second law efficiencies are determined for different inlet angles. • Maximum power decreases and efficiency increases with decreasing steam quality. The Tesla turbine with insulated rotors has been investigated numerically and analytically for the application in Rankine cycle power plants for waste heat recovery. Simulations are performed for the multiphase, compressible, turbulent flow of wet steam to study the thermofluid dynamics and performance characteristics for a wide range of dimensional and dimensionless parameters. The expansion of steam inside the rotor is verified by density and Mach number contours. The increase in radius and inlet angle seems to increase the power obtained, with the maximum total recoverable power reaching as high as 2 M W using 750 m m rotors for inlet angle 3 ° , keeping in view the efficiency. The efficiency curves are compared with that of the laminar, incompressible flow of air, which seems to follow a similar qualitative nature but with a significant decrease in the effect of inlet angle. Fuel cost estimation of a 2000 M W power plant employing the Tesla turbines that use 20 % bled steam is performed and encouraging preliminary reduction in cost is observed. The previously derived scaling laws have been modified and extended to include thermal similarity characteristics using a new dimensionless parameter ( T s ) . Exergy analysis is performed on the rotors, which show that the second law efficiency seems to follow a decreasing trend with increasing inlet angle similar to the rotor efficiency. Sharp drops in rotor and second law efficiencies are observed when the dynamic similarity number Ds drops or rotor radius increases beyond certain values. The exergy destruction seems to increase exponentially with increasing radius. Impact on the performance by the variation of the dryness fraction of wet-steam has been reported for steam qualities 0.8 - 0.95 . Although the obtainable power decreases with the dryness fraction, the rotor and second law efficiency seem to increase, cementing the previous claims of the ability of Tesla turbines to perform efficiently at poor steam qualities.

Power Production and Drag of Autorotating Cross Cylinder Turbine Models

The autorotation phenomena of bladeless symmetric objects exposed to fluid flow have promised power generation from the kinetic energy of natural water and air currents. Our past experiments on bladeless turbine models suggest non-linear correlation between the flow speed and power production. This report explores factors such as flow obstacles and turbine’s position that may affect the power generation of such turbines at Reynolds numbers around 10,000 to 50,000. Using a custom-made water flow tank, we tested the power production and generated drag forces of 3D-printed bladeless turbine models under various conditions of flow. Results indicate the significant effect of flow straightener and flow perturbation to the power production. Additionally, the effects of turbine infill density and flow speed on the generated drag and measured rotation-per-minute (rpm) are reported. The minimal effects from the turbine’s weight and position in the water flow on the power production require further exploration

Experimental Characterization of Losses in Bladeless Turbine Prototype

Abstract Multidisk bladeless turbines, also known as Tesla turbines, are promising in the field of small-scale power generation and energy harvesting due to their low sensitivity to down-scaling effects, retaining high rotor efficiency. However, low (less than 40%) overall isentropic efficiency has been recorded in the experimental literature. This article aims for the first time to a systematic experimental characterization of loss mechanisms in a 3 kW Tesla expander using compressed air as working fluid and producing electrical power through a high-speed generator (40 krpm). The sources of losses discussed are stator losses, stator–rotor peripheral viscous losses, end-wall ventilation losses, and leakage losses. After description of experimental prototype, methodology, and assessment of measurement accuracy, the article discusses such losses aiming at separating the effects that each loss has on the overall performance. Once effects are separated, their individual impact on the overall efficiency curves is presented. This experimental investigation, for the first time, gives the insight into the actual reasons of low performance of Tesla turbines, highlighting critical areas of improvement, and paving the way to next-generation Tesla turbines, competitive with state-of-the-art bladed expanders.

Dynamo in tesla turbine, based on recyclable materials, for decentralized energy generation and recharge batteries: system evaluations

Nowadays the search for new forms of energy generation is one of the great challenges of humanity. Decentralized energy production as well as material recycling, in order to obtain low-cost environmental gains, are extremely important points, as they are issues that must be evaluated in parallel with sustainable development, being extremely discussed and disseminated for their relevance and importance, since the main focus certainly corresponds the environmental preservation of the planet. In view of this theme, in the present work, a prototype was built using Tesla turbine and a dynamo couplet, aiming at the decentralized energy generation model, for the recharge of lead-acid batteries concomitantly with the challenge of reaching an innovative and unprecedented device with economic and environmental gains. The developed system was made and structured from the manufacture of various accessories obtained from recyclable materials attached to its structure, through the improvement of the physical model during its manufacture until the performance of experimental tests investigating its functionality. The results show that the projected system responded significantly to what was proposed, where the dynamo generated current for the system, providing 12 V in the physical model, recharging the battery. In view of the results obtained, it is believed that the prototype has great potential, in a characteristic line and direction, where with the improvement of the structure and diversification of components it is possible to become a new proposal, that is, an innovative device that meets expectations at an affordable price, being a decentralized model of energy generation and environmentally friendly.

A Novel Respiratory Control and Actuation System for Upper-Limb Prosthesis Users: Clinical Evaluation Study

The most widely-used active upper-limb (UL) prostheses worldwide are body-powered (BP), which is a two-centuries-old technology. Despite their affordability and functional benefits to users, these devices are prone to poor outcomes for many patients. Additionally, BP devices have witnessed limited improvements compared to their externally-powered counterparts. Literature indicates a strong need for appropriate prosthetic solutions for children and adolescents. Our previous work introduced a first-of-its-kind breathing-powered UL prosthesis (“Airbender”) that can overcome several limitations of the current BP systems (e.g., restricted operation space, user discomfort caused by the harness to which the cables are attached). Users can regulate their breathing, and this controllable airflow is subsequently used to power a small (purpose-built and optimised) Tesla turbine that can accurately control the opening and closing of the prosthetic hand. The current work explores device usability in children and adolescents with a UL difference (n = 15). Further, we gathered feedback, suggestions and satisfaction levels from the study participants and their parents on breathing as a modality of controlling a prosthetic device. The collected responses and study observations were subjected to qualitative and statistical analysis. This study showcases real-world testing of a breathing-powered prosthesis and proves that UL-deficient children and adolescents can indeed operate the device (i.e., volitionally open or close) with their breathing input. The perceived level of difficulty in opening or closing the device tended to be on the ‘easy’ side. We report generally favourable feedback obtained from participants and their parents. Additionally, design suggestions and satisfaction levels concerning different device attributes help us involve the key stakeholders in co-creating and proactively developing a robust product development roadmap. This work is aligned with creating a step-change in the potential BP prosthetics options for patients in the future, propelled by a need-led approach.

Analysis on Inlet Nozzle Design Geometry of Tesla Turbine

Tesla turbine is a bladeless turbine that uses a set of discs arranged at a certain distance to rotate and one of the parameters controlling turbine performance is the inlet parameter. The purpose of this study is to optimize the design of the inlet nozzle and analyse its effects on the flow of the fluid. A total of four nozzle designs have been proposed using CATIA while the Solidworks Flow Simulator is used to analyse the fluid flow at various inlet velocities. Then, the most efficient design is then fabricated via 3D printing and put to test by connecting it with the actual Tesla turbine model. Through the results obtained from the analysis, it is observed that Design 4 is the most efficient of all tested nozzles and the highest RPM and output voltage achieved from the nozzle is 7940 RPM and 13.56 V. The difference in velocity and pressure increases as the area of the nozzle outlet reduces, whereas nozzle efficiency decreases as the inlet velocity increases. The result of this study is a source material for increasing the effectiveness of an alternative power turbine in generating electricity by manipulating the inlet design geometry.

Influence of Outlets Port Design on The Tesla Turbine Performance

The boundary layer turbine known as Tesla Turbine invented long ago but has failed to be commercialized and replaced by bladed turbines. In this paper, two new techniques for improving the turbine have been proposed. A test model of the proposed boundary layer turbine has been fabricated made and tested under different conditions. The design process includes producing a virtual design and simulation of the turbine using computer software. The proposed designs were fabricated and then tested to analyse results such as speed produced, power produced, and the turbine efficiency. From this study, the proposed turbine designs manage to achieve 18% and 69% efficiency. The findings of this study will serve as a reference for future studies in the generation of power through an alternative powered driven turbine.

Topology optimization applied to the design of Tesla-type turbine devices

Tesla-type turbine devices are turbine devices which convert fluid motion into the rotating motion of a rotor, but without the need of any blades. This is possible due to the interaction of the boundary layer with the rotating fluid motion. In order to successfully optimize this type of fluid flow device through the topology optimization method, some relevant aspects need to be considered. The first one is due to its unique configuration, meaning that the 2D swirl flow model may be considered, which is much less computationally expensive than considering a “full” 3D model. Moreover, since higher mesh resolutions may be necessary in the design of Tesla-type turbines from to the possible appearence of smaller disk-like structures, this may increase the overall optimization cost if the traditional Taylor-Hood elements (quadratic finite elements for the velocity) are considered. This additional computational cost may be reduced by considering MINI elements (linear finite elements with bubble enrichment for the velocity) instead. Another modification that may be useful in its design is augmenting the traditional Brinkman model used in topology optimization with an additional inertial term (Brinkman-Forchheimer model), which may lead to better optimized Tesla turbine designs. Another factor to be considered is the multi-objective function, which may be defined to minimize the relative energy dissipation and maximize the power transferred from the fluid. In such case, the power objective function may be augmented with an additional porosity (material model) term. Numerical examples are presented, taking into account some aspects of the design of Tesla-type turbine devices.

CFD investigation on the performance analysis of Tesla turbine

A Tesla turbine is a bladeless turbine in which fluid flows in the direction of the centripetal path. It uses fluid properties such as Boundary layer & adhesion of fluid on a series of discs keyed to a shaft. The initial cost and maintenance cost of the Tesla turbine is very low. Our project’s main motive is to improve the performance of a Tesla turbine by changing various parameters such as disc diameter and disc rotating speed through the CFD simulation software using water as a working fluid. The CAD model is designed using Ansys design modeler, meshing is performed using Ansys meshing and post processing is carried out in Ansys fluent. The numerical simulations were carried out using Ansys Fluent which is based on the finite volume method and the changes that occurred in the pressure and velocities are investigated. The parametric study is performed by varying the turbine disc speed. By performing CFD simulations, total pressure contour and velocity magnitude contours are plotted and it is found that pressure and velocity are maximum when the clearance between disc and turbine casing is lesser and at higher turbine disc speeds. The power output of the Tesla turbine is also plotted for various rpm where higher rpm gives maximum power output. The results from the present study would be useful in designing an efficient Tesla turbine with improved performance.

Harvesting the Potential of CO2 before it is Injected into Geological Reservoirs

To store CO2 in geological reservoirs, expansion valves have been used to intentionally release supercritical CO2 from high-pressure containers at a source point to lower-pressure pipelines and transport to a selected injection site. Using expansion valves, however, has some shortcomings: (i) the fluid potential, in the form of kinetic energy and pressure which can produce mechanical work or electricity, is wasted, and (ii) due to the Joule-Thomson cooling effect, the reduction in the temperature of the released CO2 stream might be so dramatic that it can induce thermal contraction of the injection well causing fracture instability in the storage formation. To avoid these problems, it has been suggested that before injection, CO2, should be heated to a temperature slightly higher than that of the reservoir. However, heating could increase the cost of CO2 injection. This work explores the use of a Tesla Turbine, instead of an expansion valve, to harvest the potential of CO2, in the form of its pressure and kinetics, to generate mechanical work when it is released from a high-pressure container to a lower-pressure transport pipeline. The goal is to avoid throttling losses and to produce useful power because of the expansion process. In addition, due to the friction between the gas and the turbine disks, the expanded gas temperature reduction is not as dramatic as in the case when an expansion valve is used. Thus, as far as CO2 injection is concerned, the need for preheating can be minimized.

Numerical assessment of a two-phase Tesla turbine: Parametric analysis

• Tesla turbine performance analysis in two-phase condition via CFD and analytical model. • The phase change model is adapted to R404a based on saturation temperature. • 1D-homogeneous analytical model estimation is comparable with 3D nonhomogeneous model. • The surface roughness effect is more pronounced at lower gaps between the disks. • The two-phase tesla turbine produced ~ 0.8 W and torque of 3.6 mN-m at 2000 RPM. The scenarios on the future energy systems invariably point to heat pumps as an emerging technology to reach efficiency goals alongside energy and CO 2 reduction targets. Moreover, they may progressively foster the use of chillers and refrigeration units. In this study, a technology that could enhance the efficiency of systems based on inverse cycles is analysed. Particularly, the two-phase flow behaviour of a Tesla turbine is numerically investigated. The main objectives are to clarify the role of the second phase, the actual operating range, and examine the flow mixing. Two computational approaches are developed, relying on a customised home-built mathematical model and CFD analyses carried out with a commercial software. The calculations are performed for two-phase R404a fluid over significant ranges of rotational speed, plate gap size, and plate roughness. All the critical liquid–vapour interactions are determined and discussed utilising the CFD solution of the Eulerian-Eulerian approach with a frame motion technique. The other model is a homogeneous finite-difference solution, and the mass transfer is directly determined based on the phase diagram of the fluid neglecting other phase-interaction parameters. The two approaches are compared to some available experimental results from the literature, revealing an excellent agreement. The results show the average power output of 0.8 W with a delivered torque of 3.6 mN-m at a rotational speed of about 2000 RPM. The numerical analysis explains the different effects of the two-phase conditions on the turbine efficiency, paving the way to an accurate design of boundary layer turboexpanders operating under these conditions.