DE202023101859U1 - A system to study the performance of a two-bladed two-stage Savonius-like hydrokinetic turbine at low flow rate conditions - Google Patents

Abstract

A system for studying the performance of a two-bladed two-stage Savonius-like hydrokinetic turbine (SAHT) at low flow rate conditions, the system comprising:
a turbine designed with two blades and a vertical axis double stage; And
an open channel test arrangement enabling the experiment, whereby the developed turbine is immersed in the open channel test arrangement and water flows through it to carry out the experimental investigation.

Description

FIELD OF THE INVENTION

The present disclosure relates to a system for investigating the performance of a two-stage two-stage hydrokinetic Savonius-like turbine (SAHT) at low flow rate conditions. More particularly, the present disclosure relates to a system for investigating the performance of a two-bladed, two-stage, vertical axis SAHT flow-stream turbine by changing the gap/spacing between the stages.

BACKGROUND OF THE INVENTION

The demand for electricity has increased in response to the expansion of human activity, which has also increased the price of conventional energy sources and the level of greenhouse gas emissions around the world. In the 21st century, the world is facing a serious energy problem that fossil fuels alone cannot solve under any circumstances. As a result, the use of renewable energy has increased because it is environmentally friendly, endless and has a significant impact on the formulation of energy regulations.

Globally, the focus of hydropower research has increased on microscale hydropower systems. Savonius-like hydrokinetic turbines (SAHT), Gorlov water turbines (GWT), H-Darrieus water turbines, etc. have all been manufactured in this area, where the kinetic energy of the low-head, low-velocity water flow is converted into mechanical energy. Namely, SAHT is defined as the type of vertical axis turbine that can operate in low flow conditions and no head thanks to improved self-launching capability. For micro-scale power generation with SAHT, low flow velocities in river basins and in canals and canals are large water resources.

However, the biggest problem with SAHT is that it is less effective. As a result, study in this area focuses on the development and use of creative designs to improve the performance of such turbines. Therefore, there is a need to improve its efficiency. It has been observed from the literature that technological advances have been used to improve the performance of the SAHT, including installing baffles in various locations, positioning circular cylinders on the side of the advancing blades, multi-stage Savonius turbines, increasing the number of the blades, changing the shape of the blade, etc.

In view of the above discussion, it is apparent that there is a need for a system for investigating the performance of a two-bladed two-stage Savonius-like hydrokinetic turbine (SAHT) at low flow rate conditions.

SUMMARY OF THE INVENTION

The present disclosure relates to a system for examining the performance of the two-bladed two-stage hydrokinetic Savonius-like turbine (SAHT) at low flow rate conditions. By varying the gap/distance between the stages, the present invention aims to investigate how well a two-bladed, two-stage, vertical-axis SAHT performs as a flow-stream turbine. The stages are positioned on the shaft with a 90° out-of-phase assembly. The distance between the steps can be from 0 to 20 mm, with each millimeter adding 5 mm. The tests are conducted under different load conditions, considering different low flow velocities ranging from 0.4 to 0.6 m/s, which are usually encountered in the perennial rivers. It is found that the performance of the SAHT is affected by the stage gap. The optimal loading condition and the optimal distance between steps were identified based on the experimental results.

The present disclosure seeks to provide a system for examining the performance of the two-bladed two-stage Savonius-like hydrokinetic turbine (SAHT) at low flow rate conditions. The system includes: a turbine designed with two blades and a two-stage vertical axis; and an open channel test assembly facilitating the experiment, wherein the developed turbine is immersed in the open channel test assembly and water is passed through it to conduct the experimental study.

In one embodiment, the open channel experimental setup comprises: an open channel for water flow, the open channel comprising a water inlet and a water outlet, and the open channel having an adjustable base; a plurality of water pumps for supplying water to an open channel, water being supplied by two centrifugal water pumps, further activating an additional water pump when an upgraded Was water speed value is needed while the outflow is changed; an underground water tank for storing water, from which the water is pumped into an open channel by water pumps; an ADV unit for measuring a wide range of water speed, the ADV unit comprising an ADV probe, a computer interface and an ADV field processor connected to the ADV probe using a high capacitance tendon; and an adjustable outlet gate for controlling the water outlet from the open channel by means of a regulator.

An object of the present disclosure is to provide a system for studying the performance of the two-bladed two-stage Savonius-like hydrokinetic turbine (SAHT) at low flow rate conditions.

Another object of the present disclosure is to examine the effects of the gap spacing between the stages of the SAHT on its performance.

Another object of the present disclosure is to study the performance of the two-stage SAHT at low water velocities of perennial rivers.

Another object of the present disclosure is to study the effects of different braking loads on the shaft of the SAHT and then estimate its performance.

Yet another object of the present disclosure is to examine the performance of the SAHT as a prime mover for pumping at a very low TSR (less than 0.2).

In order to further clarify the advantages and features of the present disclosure, the invention will be described in more detail with reference to specific embodiments thereof illustrated in the accompanying drawings. It should be understood that these drawings represent only typical embodiments of the invention and are therefore not to be considered as limiting its scope. The invention will be described and illustrated with additional specificity and detail with the accompanying drawings.

character list

• 1 veranschaulicht ein Blockdiagramm eines Systems zum Untersuchen der Leistung einer zweiblättrigen zweistufigen Savonius-ähnlichen hydrokinetischen Turbine (SAHT) bei Bedingungen niedriger Strömungsgeschwindigkeit gemäß einer Ausführungsform der vorliegenden Offenbarung;
• 2 Zeichnungen der Draufsicht einer zweiblättrigen Doppelzustands-Savonius-Turbine und eine Vorderansicht der zweistufigen SAHT gemäß einer Ausführungsform der vorliegenden Offenbarung veranschaulicht; und
• 3 veranschaulicht ein schematisches Diagramm des entwickelten Versuchsaufbaus mit offenem Kanal gemäß einer Ausführungsform der vorliegenden Offenbarung.

These and other features, aspects and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout the drawings, wherein:

• 1 12 illustrates a block diagram of a system for investigating the performance of a two-bladed two-stage Savonius-like hydrokinetic turbine (SAHT) at low flow rate conditions in accordance with an embodiment of the present disclosure;
• 2 12 illustrates top plan drawings of a two-blade, two-stage Savonius turbine and a front view of the two-stage SAHT, in accordance with an embodiment of the present disclosure; and
• 3 FIG. 12 illustrates a schematic diagram of the open channel experimental setup developed, in accordance with an embodiment of the present disclosure.

Furthermore, those skilled in the art will appreciate that elements in the drawings are presented for simplicity and may not necessarily be drawn to scale. For example, the flowcharts illustrate the method in terms of the salient steps involved to help improve understanding of aspects of the present disclosure. Moreover, with respect to the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may only show such specific details as are relevant to an understanding of the embodiments of the present disclosure around the drawings not to be obscured with details that would be readily apparent to one of ordinary skill in the art benefiting from the description contained herein.

DETAILED DESCRIPTION:

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It should be understood, however, that no limitation on the scope of the invention is intended thereby, contemplating such changes and further modifications to the illustrated system, and such further applications of the principles of the invention illustrated therein, as would normally occur to one skilled in the art to which the invention relates.

Those skilled in the art will understand that the foregoing general description and the following detailed description are exemplary and explanatory are for the invention and are not intended to limit it.

Reference throughout this specification to "an aspect," "another aspect," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure is. Thus, the phrases "in one embodiment," "in another embodiment," and similar phrases throughout this specification may, but need not, all refer to the same embodiment.

The terms "comprising," "comprising," or other variations thereof are intended to cover non-exclusive inclusion such that a process or method that includes a list of steps includes not only those steps but may include other steps not expressly listed or any inherent in such process or procedure. Similarly, without further limitation, one or more devices or subsystems or elements or structures or components preceded by "comprises...a" does not exclude the existence of other devices or other subsystems or other elements or other structures or other components or additional devices or additional subsystems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The system, methods, and examples provided herein are illustrative only and are not intended to be limiting.

Embodiments of the present disclosure are described below in detail with reference to the accompanying drawings.

1 12 illustrates a block diagram of a system for investigating the performance of a two-bladed two-stage Savonius-type hydrokinetic turbine (SAHT) at low flow rate conditions, in accordance with an embodiment of the present disclosure. The system (100) comprises a turbine (102) designed with two blades (102a) and a vertical axis double stage (102b).

In one embodiment, an open channel experimental structure (104) is developed to facilitate the experiment, wherein the developed turbine is immersed in the open channel experimental structure (104) and water is passed through it to conduct the experimental study.

In one embodiment, the turbine (102) constructed includes means for changing the gap spacing between stages, wherein two stages (102b) are mounted on a vertical shaft (102c) at 90° out of phase with each other. Each stage has a height of 0.085m and all blades (102a) are mounted on a 0.014m diameter central shaft (102d) by means of a nut and bolt arrangement, with a turbine shaft (102e) mounted on a ball bearing, which is attached to a plate frame below to provide support in water currents.

In one embodiment, the open channel experimental setup (104) comprises: an open channel (104a) for water flow, the open channel (104a) comprising a water inlet and a water outlet, the open channel having an adjustable base; a plurality of water pumps (104b) for supplying water to an open channel (104a), water being supplied by two centrifugal water pumps, further activating an additional water pump when an improved water velocity value is required while the discharge is being changed; an underground water tank (104c) for storing water and from which the water is pumped into an open channel using water pumps; an ADV unit (104d) for measuring a wide range of water speed, the ADV unit (104d) comprising an ADV probe, a computer interface and an ADV field processor connected to the ADV probe using a high capacity tendon connected is; and an adjustable outlet gate (104e) for controlling the exit of water from the open channel by means of a regulator. The length, height and width of the open channel are 12m, 0.505m and 0.9m respectively. The ADV unit (104d) is used to measure a wide range of water speeds using a transmitter head and three receiver arms which integrated with acoustic sensors capable of measuring three components of fluid velocity and the ADV unit further using a PC interface device and collecting the necessary experimental data, further measuring the turbine speed using a digital non-contact tachometer becomes.

In one embodiment, the turbine (102) is placed in the open channel at a position 5.2 m away from the inlet of the open channel, and then preliminary experiments are performed performed to confirm flow stability before hitting the turbine blades.

In one embodiment, the experiments are performed at different water levels, for different low free stream flow rates, and for different braking load conditions, with braking loads being applied by a cable brake dynamometer assembly.

2 12 illustrates top plan drawings of a two-blade, two-stage Savonius turbine and a front view of the two-stage SAHT, in accordance with an embodiment of the present disclosure. A two-bladed, two-stage, vertical-axis Savonius turbine was developed in which the spacing between stages can be adjusted.

The stages are positioned 90 degrees out of phase with each other on the vertical shaft. Aluminum sheets with a thickness of 1.5 mm and a semi-circular cross-section with a chord spacing of 0.14 m are used to manufacture turbine blades. The overall turbine height is 0.17 m, the overall turbine diameter is 0.26 m and the overall turbine aspect ratio is 0.64 as each stage has a height of 0.085 m. Using a nut and bolt configuration, all blades are attached to a 0.014m diameter central shaft, allowing for easy changing of the gap distance between stages. The turbine shaft is supported by a ball bearing attached to a plate frame below for stability when submerged in water.

3 FIG. 12 illustrates a schematic diagram of the open channel experimental setup developed, in accordance with an embodiment of the present disclosure. The top of the manufactured SAHT models was fully immersed in the open channel flow during the experiments (brand: Zephyr Enterprise, India). There is no free surface influence on the turbine stages, which is confirmed by analysis of velocity signatures on the upper water layers. The lack of bottom boundary layer influence on the turbine stages is similarly confirmed by detecting velocity signatures in the lower water layers, which is also supported by velocity distribution plots in different layers. The open channel is 12 meters long, 0.505 meters high and 0.9 meters wide. The ideal value for maintaining the water depth of the canal is 0.2 m, taking into account the total turbine height of 0.17 m. To maintain this water depth, the maximum water flow rate of 90 L/s is maintained in the channel. A dynamic outlet gate alternates the outflow to control water depth. Two centrifugal pumps, the first of which has a power of 15 HP (Brand: Kirloskar Brothers Ltd.) and the other has a power of 20 HP, are used in the open channel arrangement to pump water through the open channel (Crompton Greaves GmbH). The structure has an additional 15 HP pump that can be activated as needed to increase the water velocity value while changing the outflow.

The pumps are used to pump water from the underground water tank via the open channel. Using a 16 MHz Micro Acoustic Doppler Velocimeter (ADV) (manufactured by SonTek/YSi Inc., USA), the maximum water velocity recorded in this configuration is 0.65 m/s. A single point flow meter that can measure a variety of water velocities is called an ADV. Three receiver arms and a transmitter head with integrated acoustic sensors form the ADV. At a specified distance from the transmitter head, these sensors are able to monitor the three components of liquid (water) velocity. The operating range of the micro ADV is 0.03-2.5 m/s, the sampling frequency is 0.1-50 Hz and the accuracy is ± 1%. The SonTek Horizon ADV program is loaded onto this PC-interfaced device and the necessary experimental data is collected accordingly. A digital non-contact tachometer (Manufacturer Systems) measuring turbine speed has an accuracy of ±1%.

Various parameters are calculated using the data obtained from the experiment conducted using the experimental setup.

The maximum (theoretical) energy possessed by the inflow with a free inflow velocity (U) can be calculated using equation (1). $${\text{P}}_{\text{Max}}=\frac{1}{2}\mathrm{\rho }{\text{AU}}^3$$

The hydrodynamic torque of the turbine is calculated based on the applied load measured using a cable brake dynamometer assembly. It can be expressed mathematically using equation (2) given below, $$\text{T}=\frac{\left(\text{W}-\text{S}\right)\left({\text{R}}_{\text{shaft}}+{\text{i.e}}_{\text{right}}\right)\text{G}}{1000}$$

Where W is the applied load (Nm), S is the residual spring balance (Nm), R _shaft is the shaft radius (m), dr is the diameter of the nylon cord used (m).

The power extracted from the inflow by using the Savonius turbine can be expressed using equation (3) given below. $${\text{P}}_{\text{red}}=T\omega$$

The coefficient of performance (Cp) refers to the fraction of the power extracted using the turbine out of the total water power expressed mathematically as given in Equation (4) below. $${\text{C}}_{\text{p}}=\frac{{\text{P}}_{\text{red}}}{{\text{P}}_{\text{Max}}}$$

Turbine Tip Speed Ratio (TSR) indicates one of the major factors related to the effect of free stream speed on turbine speed. It can be calculated using Equation (5) given below. $$\text{TSR}=0.5\mathrm{\omega }\text{u}$$

Two circulation pumps continuously pump a significant volume of water through the inlet section of the flume into what is considered an open flume. Although the flow of water through the canal is quite turbulent, how intense it is is controllable. The turbine must be properly positioned so that the free flow of water is stable, or in other words, the turbulence intensity of the flow must fall within a respectable range. In general, the incident free stream velocity is inversely related to the calculation of turbulence intensity, while the standard deviation of flow, which accounts for velocity changes in the x, y, and z directions, is directly related. The intensity of turbulence for the flow at a given position can be calculated using the equation given below. $$l=\sqrt{\left(\frac{\left(u_l{}^2+V_l{}^2+W_l{}^2\right)}{3}\right)}\times 1/u$$

The turbine is positioned 5.2 m from the mouth of the flume. Preliminary tests were then carried out (details in the following section) to verify the flow stability before impact with the turbine blades. At this point in the turbine, it was determined that the water turbulence was within acceptable limits.

Another factor that needs to be examined is the blocking rate. The ratio of turbine face area (HD) to duct cross-sectional area (HcW) is known as the clogging ratio (b). It can be calculated mathematically with Eq. (7) as follows: $$\mathrm{\beta }=\frac{\text{H}\times \text{D}}{{\text{H}}_{\text{c}}\times \text{W}}$$

The clogging ratio for the current design, where the manufactured turbine has an aspect ratio of 0.64, is 20.94%. There is no blocking adjustment in this situation because it is less than 30%.

The water currents were measured at different vertical points of the turbine, calculated from the flume bottom, since the free current speed changes for different water depths. The ADV probe measures flow velocities at three different water depths, 0.08 m, 0.10 m and 0.14 m, and average data is taken into account for the analysis. In the channel, the free water surface is 0.03 m above the upper edge of the blades. The average water velocities considered in this work are 0.4, 0.5 and 0.6 m/s, which correspond to the average water flow velocities common in most perennial rivers. The velocity distributions are recorded by placing the ADV probe at different positions between 30 cm and 60 cm upstream of the turbine axis in 5 cm increments. The tests were conducted under different braking load situations, including 100g, 250g, 500g, 750g and 1000g, in the channel that was considered open. The braking loads are applied by a cable brake dynamometer arrangement.

In one embodiment, error analysis is performed to make the data error free. In the present invention, a total of six repeatable tests were performed to guarantee the repeatability of the measurements to allow for human error. Second, to ensure the accuracy and precision of the collected data, measurement errors caused by voltage fluctuations during the experiments were effectively controlled using data reduction and smoothing techniques.

Different instruments are often combined to measure different parameters in an experimental setting. Independent Depending on how well the calibration is done, each of these instruments will deviate to some degree from the true value, commonly referred to as the instrument's accuracy. Standard scoring techniques are used to determine the instrument error, which is the total error of these instruments over a series of tests. In view of this, equation (8) provided below is used to calculate the instrumental errors for the experiments performed in the current study. $${\mathrm{<figure-callout\; id="0"\; label="\psi "\; filenames="DE202023101859U1\_0012.png"\; state="\{\{state\}\}">\psi </figure-callout>}}_0={\left[{\left({\psi }_{Tm}\right)}^2+{\left({\psi }_{ADV}\right)}^2+{\left({\psi }_{SB}\right)}^2\right]}^{1/2}$$

The coefficient of performance (Cp) and torque (T) produced by the turbine are now the two main output parameters considered in the current study. According to Eq. (1)-(5) they are calculated with the corresponding observed parameters. In view of this, the instrument error related to the calculation of Cp is presented as follows. $$\frac{\delta C_p}{C_p}=\sqrt{{\left(\frac{\delta T}{T}\right)}^2+{\left(\frac{\delta w}{w}\right)}^2+{\left(3\frac{\delta u}{u}\right)}^2}$$

Similarly, the instrumental error associated with the calculation of the torque produced by the turbine is expressed as shown below. $$\frac{\delta T}{T}=\frac{\delta S}{S}$$

Based on the data and using equations (9) and (10), the instrumental error associated with the calculated value of Cp and the torque (T) is estimated to be ±8.5% and ±5.7%, respectively.

The results of the investigation conducted in the present disclosure are listed below.

The effect of the variable load on this turbine is such that up to a load condition of 1000g the turbine can produce more hydrodynamic torque and mechanical power; however, the power generated is slightly less than that of torque at higher loads.

The ideal gap distance between the two stages of the two-leaf, two-stage SAHT under consideration is determined to be 5 mm. It has been determined that the ideal braking load for better hydrodynamic performance of the SAHT is a 1000g load.

The SAHT achieves its maximum hydrodynamic torque of 0.0529 Nm at optimal load and gap spacing for a flow rate of 0.4 m/s, but the turbine achieves its maximum power of 0.0507 when the flow rate of 0.5 m/s is maintained under optimal load and gap spacing parameters .

With the ideal braking force and speed ratio (TSR) of 0.1538 for a flow speed of 0.5 m/s, the highest coefficient of performance of 0.0341 is achieved. This is the SAHT's optimum performance, which is also superior to similar turbine designs and corresponds to a lower TSR level.

Further investigation of the performance of SAHT in pumping mode at different water flow velocities with or without a flowmaker at the turbine inlet is necessary. In order to improve current performance, the larger aspect ratio of this developed SAHT must be evaluated at a higher flow rate. Further work on this turbine design may also include fluid dynamics analysis to determine the performance insight of this novel design with different gap distances by visualizing the flow transport across the gap and across the layers within the gap.

The drawings and the above description provide exemplary embodiments. Those skilled in the art will recognize that one or more of the elements described may well be combined into a single functional element. Alternatively, certain elements can be broken down into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Furthermore, the actions of any flowchart need not be implemented in the order shown; also, not all actions have to be performed. Actions that are not dependent on other actions can also be performed in parallel with the other actions. The scope of the embodiments is in no way limited by these specific examples. Numerous variations, whether or not expressly stated in the description, such as differences in structure, dimensions and use of materials, are possible. The scope of the embodiments is at least as broad as indicated by the following claims.

Advantages, other benefits, and solutions to problems have been described above with respect to specific embodiments. However, the benefits, benefits, problem solutions, and components that may cause benefits, benefits, or solutions to occur or become more pronounced are not to be construed as critical, required, or essential features or components of any or all claims.

Reference List

100

A system for studying the performance of a two-stage Savonius-Akin hydrokinetic turbine (SAHT) with two blades.

102

turbine

102a

two blades

102b

Double Stage With Vertical Axis

102d

central shaft

102c

Vertical Wave

102e

turbine shaft

104

Open channel experimental set-up

104a

open channel

104b

Multiple water pumps

104c

water tank

104d

adv unit

104e

An adjustable discharge gate

302

water inflow

304

pump

306

water tank

308

2-blade Savonius turbine

310

Adjustable base

312

computer interface

314

Adv field processor

316

High Capacity Chord

318

controller

320

Adjustable outlet slide

322

water drain

324

Adv probe

326

open channel

Claims (8)

A system for studying the performance of a two-bladed two-stage Savonius-like hydrokinetic turbine (SAHT) at low flow rate conditions, the system comprising: a turbine designed with two blades and a vertical axis double stage; And an open channel test arrangement enabling the experiment, whereby the developed turbine is immersed in the open channel test arrangement and water flows through it to carry out the experimental investigation. system after claim 1 wherein the assembled turbine includes means for varying the gap spacing between stages, two stages being mounted on a vertical shaft at 90° out of phase with each other. system after claim 2 , with each stage having a height of 0.085 m and all blades mounted on a central shaft, which has a diameter of 0.014 m, by means of a nu-bolt arrangement, with a turbine shaft being mounted on a ball bearing fixed at the bottom of a Plate frame is attached to provide support in water flow. system after claim 1 wherein the open channel experimental setup comprises: an open channel for water flow, the open channel including a water inlet and a water outlet, the open channel having an adjustable base; a plurality of water pumps for supplying water to an open channel, water being supplied by two centrifugal water pumps, further activating an additional water pump when an improved water velocity value is required while the discharge is being changed; an underground water tank for storing water, from which the water is pumped into an open channel by water pumps; an ADV unit for measuring a wide range of water speed, the ADV unit comprising an ADV probe, a computer interface and an ADV field processor connected to the ADV probe using a high capacitance tendon; And an adjustable discharge gate to control the water exit from the open channel with the help of a regulator. system after claim 4 , where the length, height, and width of the open channel are 12 m, 0.505 m, and 0.9 m, respectively. system after claim 4 , where the ADV unit is used to measure a wide range of water speeds, this being done with is carried out with the help of a transmitter head and three receiver arms integrated with acoustic sensors capable of measuring three components of liquid velocity, and further using the ADV unit a device with PC interface and collecting the necessary experimental data , further measuring turbine speed using a digital non-contact tachometer. system after claim 1 , where the turbine is placed in the open channel at a position 5.2 m away from the inlet of the open channel, and thereafter preliminary tests are performed to confirm the flow stability before it hits the blades of the turbine. system after claim 1 , the experiments being carried out at different water levels, for different low free-stream current velocities and for different braking load conditions, braking loads being applied by a Seil-Brae type dynamometer arrangement.

Images