Tesla Turbine Research Articles

Predicting the Parameters of Vortex Bladeless Wind Turbine Using Deep Learning Method of Long Short-Term Memory

From conventional turbines to cutting-edge bladeless turbines, energy harvesting from wind has been well explored by researchers for more than a century. The vortex bladeless wind turbine (VBT) is considered an advanced design that alternatively harvests energy from oscillation. This research investigates enhancing the output electrical power of VBT through simulation of the fluid–solid interactions (FSI), leading to a comprehensive dataset for predicting procedure and optimal design. Hence, the long short-term memory (LSTM) method, due to its time-series prediction accuracy, is proposed to model the power of VBT from the collected data. To find the relationship between the parameters and the variables used in this research, a correlation matrix is further presented. According to the value of 0.3 for the root mean square error (RMSE), a comparative analysis between the simulation results and their predictions indicates that the LSTM method is suitable for modeling. Furthermore, the LSTM method has significantly reduced the computation time so that the prediction time of desired values has been reduced from an average of two and a half hours to two minutes. In addition, one of the most important achievements of this study is to suggest a mathematical relation of output power, which helps to extend it in different sizes of VBT with a high range of parameter variations.

Efficiency based optimization of a Tesla turbine

Tesla turbine is a bladeless, radial turbine which might be suitable for the applications in various energy systems, e.g. in Organic Rankine Cycle or combined heat and power systems if its efficiency improves. The investigations presented in the paper concern efficiency based numerical optimization of a Tesla turbine. Parameters subjected to the optimization process are inlet nozzle height, inter-disc gap, nozzle angle, pressure and rotational velocity. The optimization was conducted using response surface methodology. The first stage of the optimization excluded pressure ratio as neutral to efficiency. The second stage of the optimization allowed determination of the most important parameters: tangential velocity ratio, partial admission coefficient, reaction degree and aspect ratio required for maximization of the turbine's efficiency. Efficiency was improved almost twice with the respect to the nominal model (from 9% to 17%) and validated experimentally. Performance characteristics of the optimized turbine model were calculated using computational fluid dynamics software.

Performance Study of a Bladeless Microturbine

The paper presents a comprehensive numerical and experimental analysis of the Tesla turbine. The turbine rotor had 5 discs with 160 mm in diameter and inter-disc gap equal to 0.75 mm. The nozzle apparatus consisted of 4 diverging nozzles with 2.85 mm in height of minimal cross-section. The investigations were carried out on air in subsonic flow regime for three pressure ratios: 1.4, 1.6 and 1.88. Maximal generated power was equal to 126 W and all power characteristics were in good agreement with numerical calculations. For each pressure ratio, maximal efficiency was approximately the same in the experiment, although numerical methods proved that efficiency slightly dropped with the increase of pressure ratio. Measurements included pressure distribution in the plenum chamber and tip clearance and temperature drop between the turbine’s inlet and the outlet. For each pressure ratio, the lowest value of the total temperature marked the highest efficiency of the turbine, although the lowest static temperature was shifted towards higher rotational speeds. The turbine efficiency could surpass 20% assuming the elimination of the impact of the lateral gaps between the discs and the casing. The presented data can be used as a benchmark for the validation of analytical and numerical models.

Vortex-induced autorotation potentials of bladeless turbine models

ABSTRACT The autorotation and energy harvesting potential of bladeless turbine models are tested in a confined water stream with Reynolds numbers from 20 K to 40 K. Mini bladeless turbine models of various geometrical shapes are 3D-printed using plastic material with low printing density. Experiments were performed using a commercial closed-loop water tank capable of delivering fine incremental speed up to a maximum of 60 cm/s. The cross-cylinder models with low density appear to demonstrate autorotation at high Reynolds numbers. Other turbine models demonstrate either stagnation or oscillation for a wide range of Reynolds numbers. For the cross-cylinder models, the autorotation phenomenon appears to be promoted at lower average flow speed when an upstream asymmetrical obstacle is introduced in the stream. The rotation per minute and energy potential (voltage and current) of the autorotating model are increased with the Reynolds number.

Effect of disc spacing and pressure flow on a modifiable Tesla turbine: Experimental and numerical analysis

This paper reports on an experimental and numerical investigation of a modifiable Tesla turbine driven by compressed air. To study the impact of geometrical parameters like the rotor’s diameter and space between the rotor and the housing, two Tesla turbine prototypes with diameters of 11.25 and 15 cm were designed and built. For both, a 3 mm space between rotor and housing is considered. In particular, for each turbine the effect of disc spacing and pressure flow in the range of real operating conditions is analyzed. Experimental characterization based on a thermodynamic analysis allows estimating optimum values of 0.9 mm and 103.89 kPa for the disc spacing and pressure flow, respectively. Additionally, values for the efficiency and the stall torque are calculated when the pressure flow is varied in the range of 50 to 327 kPa and of 59.34 to 272.46 kPa, maximum efficiencies of 33% and 50% are obtained, and stall torque measurements reach up to 0.304 N·m and 0.448 N·m, for the turbines with small and large diameters, respectively. 3D simulations performed with the open source CFD library OpenFOAM ®, well reproduced the stall torque measurements. Numerical results show that the loss of isentropic power in the space between the rotor and the housing is up to 36.17% and that the largest wall shear stress values are located on the periphery of the rotor’s disc.

The effect of drag force on the body frequencies and the power spectrum of a bladeless wind turbine

New types of bladeless wind turbines and electricity generation are currently one of the most interesting topics in engineering. Electricity generation using structural vibration due to the resonance phenomenon is the concept behind a vortex bladeless turbine. The present study numerically investigated the effects of the drag force on the body frequency of an oscillating bladeless wind turbine. A two-dimensional numerical simulation was performed for a cylinder with a semi-circular cross-flow cross-section in two different cases. This research was conducted for both uncontrolled and controlled oscillating cylinders. The controlling process was performed using a pair of ring magnets as springs with a variable coefficient. The flow field, vibration, vortex shedding, structural frequencies, and resonance phenomena were studied in this research. Finally, the controlled and uncontrolled frequencies of the cylinder are explored, and the power spectra for various velocities are analyzed in two different states, namely, with and without a tuning system. From the results, it can be concluded that the usage of the controlling system in these turbines can significantly regulate the oscillations and increase the frequency value by limiting the vibration amplitude. According to this principle, it can be inferred that increasing the frequency of fluctuations greatly increases the production capacity of these turbines.

Dynamic balanced hybridization of TENG and EMG via Tesla turbine for effectively harvesting broadband mechanical pressure

Hybrid energy harvesting systems consisting of triboelectric nanogenerators and electromagnetic generators driven by rotation are capable of high voltage and current outputs. Both generators, however, perform best under fast rotate conditions. Thus, in this work, the Tesla turbine design is used along with a hybrid system integrating a triboelectric nanogenerators (TENGs) and an electromagnetic generator (EMG) for high output performance by the input flow of working fluid. For the first time, the dynamic balance is careful analyzed for the rotator part of TENG-EMG to obtain simultaneously high output voltage – current and remaining long operation time of the system after removing the gas supplied. The optimized Tesla turbine TENG-EMG (T3-E) can even convert broadband mechanical energy from low to high input pressure into working fluid energy, result in high rotation and high electric output performance. The DC peak output voltage/current and remaining operation time of the TENG and EMG are 312.5 V/82 μA and 4.2 V/3.3 mA; 20 s and 38 s, respectively. The hybrid system’s output is significantly enhanced to 332 V/3.5 mA with the remaining operation time of 20 s for voltage and 40 s for current output, respectively. This output performance satisfies the energy demands of several portable electric loads. For practical applications, LED lighting by footfall energy harvesting and IoT wireless sensor operation is demonstrated after capacitor charging. This hybrid generator design has significant potential for real-life biomechanical energy scavenging.

Aerothermal Optimization of Bladeless Turbines

Abstract The harnessing of mechanical power from supersonic flows is constrained by physical limitations and substantial aerodynamic losses. Bladeless axial turbines are a viable alternative to extract power in such harsh conditions without restricting the operating conditions. In this paper, we present a shape optimization of the wavy surface of bladeless turbines to maximize the power extraction, while minimizing convective heat flux and pressure losses. First, a baseline geometry was defined and an experimental campaign was carried out on the baseline wavy surface of the bladeless turbine at supersonic conditions. Pressure, heat flux, and skin friction measurements were compared with the Reynolds averaged Navier–Stokes results. Afterward, an evaluation routine which consisted of the geometry and grid generation, solving, and postprocessing was implemented within a multi-objective optimization routine to maximize the pressure force and minimize heat flux and pressure loss. Finally, a three-dimensional assessment in terms of power, heat load, and pressure drop was performed for the best performing geometry with the commercial solver cfd++ of Metacomp.

Design, Construction and Simulation of Tesla Turbine

Investigations of laminar fluid flow between two moving or stationary plates, and two rotating discs, over the years were geared toward how to increase Tesla-based turbine efficiency. Therefore, this research entails the construction, design and simulation of a Tesla turbine in order to investigate the potential of Tesla turbine for energy generation. Method of solution entails the design and construction of a physical model Tesla turbine from locally sourced materials. The physical model geometry and design parameters were then used to conduct numerical simulation. Performance evaluation was then carried on the physical model and the simulation model. The result showed that voltage, current and power all increase with increase in rev. per minute. The result obtained indicates that for higher power generation, a Tesla turbine design with higher revolution per minute capability will be required. Turbine model simulation showed that radial velocity vector to be concentrated at the discs periphery and outlet.
 The research results are good references for design of larger Tesla turbine for community use.

Self-powered ammonia synthesis under ambient conditions via N2 discharge driven by Tesla turbine triboelectric nanogenerators

Ammonia synthesis using low-power consumption and eco-friendly methods has attracted increasing attention. Here, based on the Tesla turbine triboelectric nanogenerator (TENG), we designed a simple and effective self-powered ammonia synthesis system by N2 discharge. Under the driving of the simulated waste gas, the Tesla turbine TENG showed high rotation speed and high output. In addition, the performance of two Tesla turbine TENGs with different gas path connections was systematically investigated and discussed. A controllable series-parallel connection with the control of gas supply time was also proposed. Taking advantage of the intrinsic high voltage, corona discharge in a N2 atmosphere was simply realized by a Tesla turbine TENG. With the flow of N2, the generated high-energy plasma can immediately react with water molecules to directly produce ammonia. The self-powered system achieved a yield of 2.14 μg h−1 (0.126 μmol h−1) under ambient conditions, showing great potential for large-scale synthesis.

A revised Tesla Turbine concept for 2-phase applications

The Tesla turbine is an original expander working on the principle of torque transmission by wall shear stress. The principle – demonstrated for air expanders at lab scale has some attractive features when applied to two-phase expanders: it is suitable for handling limited flow rates (as is the case for machines in the range from 500W to 5 kW), it can be developed to a reasonable size (rotor of 0.1 to 0.25 m diameters), with acceptable rotational speeds (which range from 500 to 10000 rpm). The original concept was revisited, designing it for two-phase operation and considering not only the rotor configuration but the whole machine. The flow model was developed using complete real fluid assumptions including several new concepts such as bladed channels for the stator, labyrinth seals, and a rotating diffuser. Preliminary design sketches are presented, and results discussed and evaluated.

Design and Analysis of Vortex Bladeless Wind Turbine

Vortex bladeless turbine antiquates the conventional wind turbine and adopts a radically innovative and novel approach to captivate the moving wind energy. This device effectively captures the energy of vorticity, an aerodynamic instability condition. As the wind passes a structure, the flow steers and cyclical patterns of vortices are generated. Once the strength of wind force is suffice, the structure starts vibrating and reaches resonance. Vortex bladeless is a vortex induced vibration resonant power generator. It harnesses wind energy from a phenomenon of vorticity, called vortex shedding effect. Clearly bladeless technology consists of a cylinder fixed vertically on an elastic rod, instead of tower, nacelle and blades which are the crucial parts of a conventional wind turbine. The cylinder oscillates on a specifically mentioned wind range, which then generate electricity through an alternator and a tuning system. In this paper the vortex turbine is designed with certain existing parameters of dimensions in Solidworks and the same is analyzed for different materials and dimensions of mast, which is an important part in the vortex turbine. Also various performance parameters like displacement, frequency etc. are also compared among different models.

Exergo-economic environmental analysis of organic Rankine cycle

The study deals with Energy-Exergy, Economic and Environmental analysis of Organic Rankine system developed for generation of 1KW of energy. The system is designed to work in a tropical climatic condition of Prayagraj India. The system utilizes the solar parabolic trough collector for the heating of R-134a (working fluid) to be expanded in Tesla turbine developed indigenously. The gear pump is used for pumping of liquid working fluid. The condensation is done is off the shelf condenser of window air conditioner. The experimentation is done and efficiency of the cycle was calculated to be around 23%. The overall system efficiency was found to be 9.5% which is higher than the average. The payback period was calculated considering the both energy and economic constraints. The energy payback period was found to be 1.59 years and economic payback was 9.42 years. The Ecological footprint is found to be an effective method of analyzing the effect of any technology on environment and thus ecological footprint is also evaluated to be 0.17 global hectare (gha). The system so develop is found to be feasible on sustainable development goals.

Design, Fabrication and Analysis of Bladeless Turbine

A bladeless turbine is capable of using the exhaust gas energy adiabatically by converting most of its energy into shaft power. This bladeless turbine is widely known as Boundary-layer turbine or Cohesion-type turbine. The fundamental physics behind the working of the bladeless turbine is boundary layer effect; boundary layer is the layer of fluid in the immediate vicinity of a bounding surface where the effects of viscosity are significant. The heat energy that is being wasted as exhaust in a four-stroke engine can be utilized by using a bladeless turbine which is capable of converting a fast-moving fluid (exhaust gas) to shaft work. This shaft work can be used for various applications like to run an alternator or a compressor. The prototype model of bladeless Turbine has been designed and tested with different experiments were made under varying mass air flow rate of compressed air.

Simulation of vorticity wind turbines

There are a wide variety of devices behaving essentially as flexible and elastic systems while interacting dynamically with fluids, usually water or air, under normal operating conditions. Interactions of this kind involve a double complexity of the dynamics, as the systems go through large deformation due to the flow actions, and simultaneously, the flow dynamics is strongly influenced by the shape adopted by the systems. The present research adapts mathematical methods, still new to the field, to represent ways of dealing with flows of fluid in bidirectional interactions with those new technologies, and particularly applies them to the exploration of vorticity wind turbines (VWT), a new kind of vertical blade-less turbine that gathers energy from the vortex induced vibrations (VIV) of a relatively short and scalable mast. This research presents a framework for such modeling by coupling the discrete element method (DEM) with the Immersed Boundary Method (IBM), for the representation of VWT; and with the finite volume method (FVM), for solving the Navier-Stokes equations. Simulations show that the VWT achieves the lock-in effect for wind velocities between 9 and 15 m/s, with efficiency values between 20 and 30%. The preliminary results together with logistic and cost-related reasons, make these devices very promising, especially when considering the difficulties of implementing new approaches in developing countries.

Assessment of Performance of Tesla Turbine in Water Distribution Systems for Energy Harvesting

Abstract This article composes a systematic design methodology to obtain optimal parameters of the Tesla turbine, which is applicable in water distribution systems, faced with the need to supply power for wireless sensors and other components used in smart water networks and the challenges associated with the feasibility of Tesla turbine in a small scale. The optimal geometric model is sought by using a theoretical model relating turbine physical properties and flow conditions to power output by solving Navier–Stokes equations for steady laminar incompressible flow between adjacent disks. The model shows that the proposed design with dimensions and flow conditions relevant to water pipe networks can achieve a power output of 1.55 mW using a 2.5-cm diameter turbine given a pressure difference of 140 Pa. At 70 Pa using a 1-cm diameter turbine, a power output of 0.17 mW can be obtained. This study shows a great potential in application of Tesla turbine for energy harvesting in water distribution systems.

Computational investigation of partial admission effects on the flow field of a tesla turbine for ORC applications

Over recent years, the Tesla turbine gained a renewed interest from the scientific community, as its simple structure guarantees low cost and reliability. These are key aspects of the success of an expander suitable for small-distributed energy systems.The reference case for the computational analysis was selected from the available data of an experimental campaign conducted with R1233zd(E) as the working fluid. The analysed turbine has an efficiency of 29% and a power output of 0.57 kW. The fluid dynamics inside the stator, the stator-rotor gap and the rotor was assessed by means of a 3-D computational model. The comprehensive evaluation of the three regions is of paramount importance to determine the machine flow field and the related performance, as they are significantly affected by the interactions amongst the internal components. The effects of the discrete admission to the rotor are relevant in terms of flow field distortion, while the effects on the performance parameters (power and efficiency) are of minor importance. The performance results of the 3-D computational fluid dynamics are in line with those of the analytical 2-D code, which assumes the uniform admission to the rotor. Finally, after that the detailed analysis of the selected test case was conducted, several simulations with different thermodynamic conditions were carried out and compared to the results of the 2-D analytical code and the experiments.

Geometry definition and performance assessment of Tesla turbines for ORC

The Tesla turbine - also known as friction, viscous or bladeless turbine - is a peculiar expander, which generates power through viscous entrainment. In the last years, it has gained a renewed appeal due to the rising of distributed power generation applications. Indeed, this expander is not suitable to large size power generation, but it could become a breakthrough technology in the low power ranges, due to its characteristics of low cost and reliability. The current study presents a design approach to the Tesla turbine, applied to organic working fluids (R1233zd(E), R245fa, R1234yf, n-Hexane). Three fundamental geometric parameters are identified (rotor channel width/inlet diameter ratio, rotor outlet/inlet diameter ratio, throat width ratio) and their effects on the performance are analysed. The geometry of the turbine has been defined and the assessment of the performance potential is run, applying a 2D code for the viscous flow solution, considering real compressible fluid properties. For all the investigated working fluids, an efficiency higher than 60% has been achieved, with the defined geometry, under suitable thermo fluid-dynamic conditions.

CFD modelling and exergy analysis of a heat pump cycle with Tesla turbine using CO2 as a working fluid

The transcritical carbon dioxide heat pump cycle has been drawing much research interest due to its environmental friendliness and the thermodynamic features of carbon dioxide. However, there is one concerning issue, which is the huge exergy loss associated with the isenthalpic process in the expansion valve. In the current study, a new transcritical carbon dioxide heat pump cycle is proposed, where a Tesla turbine replaces the expansion valve. The Tesla turbine is a bladeless turbine that works with any two-phase fluid, which is the case for the expansion of supercritical CO2. A 3D computational fluid dynamics model is first developed to simulate the flow of carbon dioxide within a Tesla turbine, and then the extracted results are used as data for subsequent thermodynamic modeling of the heat pump cycle. The Tesla turbine power production and exergy losses, as well as the proposed heat pump cycle coefficient of performance are investigated in terms of the turbine rotor angular velocity and the gas cooler and evaporator pressures. It is demonstrated that the coefficient of performance of the cycle where a Tesla Turbine is integrated is up to 16.3% higher than the traditional cycle with the expansion valve. In addition, at rotor angular velocity equals to 1000 rad/s, the turbine power is maximum and increasing the inlet pressure leads to the higher torque and consequently higher turbine power. At lower inlet pressure, the coefficient of performance of the heat pump cycle is higher. A thermodynamic trade-off is illustrated between the power production from the Tesla turbine and the vapor quality at the outlet of the Tesla turbine, as a function of rotor angular velocity. It is numerically proven that the optimum rotor angular velocity corresponds to the maximum exergy efficiency of the Tesla turbine, which in turn leads to the maximum coefficient of the performance of the whole cycle.

Experimental investigation of an Organic Rankine Cycle Tesla turbine working with R1233zd(E)

The increasing interest in micro power generation is pushing the research world to find new solutions for increasing the efficiency of micro Organic Rankine Cycles. One of their main issues is the efficiency and the reliability of the expander. The Tesla turbine is an old/new expander, which has found a renewed interest in the last years because of the increasing appeal towards distributed micro generation, where this expander becomes competitive.This peculiar technology seems adapted to micro generation in Organic Rankine Cycle thanks to its main characteristic, which is its simple structure that allows for high reliability and cheapness. In recent years, this expander has been analytically and numerically assessed when working with organic fluids. In this study, the experimental investigation of a Tesla turbine working with R1233zd(E) is presented. One of the main achievements was the assessment of the blockage effect of disks edges when the pressure drop through the machine is relevant as in case of Organic Rankine Cycles (e.g. higher than 3–4 bars), resulting into a relatively large amount of flow deviation through the clearances between the rotor disks package and the case, which implies a throttling effect thus resulting into a relevant performance loss. This effect was accounted by a model that well fitted the experimental data.The achieved results confirmed the validity and the large applications potential of this emerging technology, especially in the fields of micro power generation, low inlet temperature and low expansion ratios. A maximum net power output of 371 W was obtained, proving the feasibility of utilizing Tesla turbines in Organic Rankine Cycle applications. A maximum shaft efficiency of 9.62% and a maximum adiabatic efficiency of 30% were achieved. The results and the developed model of disks edge losses effects represent an important step ahead, in physical depiction of the phenomenology, over the currently available literature, fundamental for the improvement of the design procedure of Tesla turbines for Organic Rankine Cycles.