Variation in the power output is caused by the change in the flow rate of the supply to the turbine and furthermore the change in load introduces serious transients. The automation of the design process is mainly governed by the similarity laws regarding turbines.
Hydrodynamic Drag
Drag Characte ristics in Cavitating Flow
To determine the power of the turbine: the variation of the delivered power with the speed.
AirfoH Data for Blade Design
Diffuser design for small turbi.nes ......................... "
Draft tube performance
The maximum recovery is promoted by the growth and high-angle separation of the turbulent boundary layer along the diffuser wall. It is desirable to minimize swirling flow in the draft tube, as this kinetic energy leads to losses.
Site specific parameters
Consideration had to be given to the complexity of the turbine, its ability to produce power with large changes in flow rate, the need to service the turbine and the frequency at which this should be done, and the final available pressure head combined with Flow. In this case, the remaining factor to consider when choosing this turning angle as a parameter for a pure axial flow turbine is the strength of the blades, which affects the design of the blades, ie.
Piping
Suppl y
The purpose of reducing the diameter of the flow only at the valve is to increase the flow rate, while the supply, which moves at a lower speed, will incur minimal friction losses. An additional reduction in bore diameter is required between the gate valve, nominal bore 600, and the large end of the reducer.
Penstock
The turbine will1 be designed so that the rotor and stator are installed in a nominal bore diameter of 350, reduced by a reducer of nominal bore 400/350.
Diffuser
A typical layout of the turbine site and manufactured turbine components can be seen in drawing 1.
Stuffing Box
Design Options
Since it is river water that will flow through the turbine, abrasion of the paint will be expected. However, the galvanization may not form a uniform coating on the surface of the inner wall and may be problematic when aligning the bushing.
Drive Train
Cast iron, normally used in connection with water, will prove too brittle in this case, bearing in mind that it will be required as a platform for the bearing column. The rationale for the selection process indicates that the best option to pursue is the stainless steel sleeve as it meets all the requirements of the design.
Bearing Selection
The importance of defining the location of the maxmlUm thickness when considering it relative to the C 0 vs . Reynolds number: This provides a basis for comparing machines according to the nature of the flow through them. If Eq.(3.9. 4) is taken into account, it is possible to proceed with the determination of the turbine sales height.
IHs l is chosen taking into account the turbine speed and the nominal and operational heads.
Manufacturing the master patterns
1:1 The space limitation on the hub was partially solved by swapping the roles of the. The rubber matched the temperature tolerance of the wax to be used for molding. Another potential problem area of the induction furnace is that it does not have an automatic controller.
This solidification could adversely affect the surface tolerance of the blades and cause problems with flow dynamics.
The governin g eq uations
It is necessary at this point to remind the reader that segmentation of the blade requires that every calculation performed for the upcoming blade shape design be applied 10 each section. Once the blade angles are determined, they are then used to generate the required roundness of the profile.
Program structure
This now allows for the calculation of the angle at which the stator chord will be positioned, and knowing that the chord length is set to a constant length, the profile shape design of the blade can follow. It is also necessary to stack the blade profiles around a certain point and this will be 30% of the arc length. The calculation of the chord is then divided into two vectors as shown in Figure 4.
The number was chosen simply to show the difference in strength between the different models.
Profile Selection
The cavitation parameter will need to be carefully analyzed due to the difference between the correct design and the existing draft tube design. This is also reflected in the lower vacuum Ps, which measures the vacuum pressure of the suction pipe. The end of the efficiency curve corresponds to the maximum power output in the stop state.
This was not possible due to a restriction on the dynamometer of the no-load speed. It was expected that the efficiency of the turbine would suffer largely from the efficiency of the draft tube. The cause of this leak was an incorrect connection of the diffuser flange to the draft pipe flange.
This is the application of the turbine Lo be designed and the design method will not be adjusted. A vent nipple hole is required in the side of the stuffing box housing.
Geonletric Represent ation
Experimental apparatus
The experimental apparatus used in measurements of the lake from the turbine is a dynarnometer and a computer. The computer results were generated by a PTO tension gauge attached to the dynamometer that fed values to a data collection card. The turbine itself was made in-house and every crucial part was fabricated in the workshop.
These were made to match the size of the outlet from the inlet shut-off valve to the reducer and to match the size of the turbine outlet with the existing diffuser.
Objectives
This effect will have major implications on the efficiency and the level of interpretation of this effect can determine the level of accuracy and precision of the design. Each of these processes will take into account the volume flow rate of the water through the turbine. These measurements will be taken in the form of differential pressure measurements within the nozzle, which is the feed pipe to the turbine.
Water temperature must also be considered as it affects the water vapor pressure, which is critical to the cavitation limit.
Experi. mental procedure
Obtaining results
By adjusting the gate valve under no-load conditions, sufficient flow was allowed through the turbine so that the speed reached the rpm limit of the dynamometer. At this stage, the gate valve was opened further until the dynamometer rpm limit was reached again. The process was repeated until the gate valve was fully opened and the maximum turbine power and torque were measured under fully open gate valve conditions.
It is in the peak torque measurement phase that rpm is measured and recorded as stall rpm.
Experi.mental results
The period between the first and second test included heavy rainfall and some subsidence of the draft tube pipes occurred. The net result is very low draft tube efficiency, as it is not possible to utilize the negative pressure of the draft tube due to the air cavity. Furthermore, the turbine itself will not be flooded, where only the lower half of the blades would receive water.
The reason for this is that the efficiency of the draft tube affects the overall lift of the turbine, which is directly proportional to the power.
Precautions for the analysis
This feature is due to the fact that the flow only recovers to "flooded pipe" conditions after the flow has traveled a length of n diameters and the sudden contraction analysis is no longer appropriate. It was therefore decided to develop a graph of the loss coefficient for the variation in value depending on the degree of valve opening.
Anal ysis of the results
Therefore, the increase in speed was the result of an increase in the mass flow rate, which was determined by setting the gate valve opening, rather than the load on the turbine. The trend of gate valve losses is shown to decrease exponentially with an increase in opening fraction, Figure 5.4. Losses across the rotor, Figure 5.4.7, and stator, Figure 5.4.8, remain a function of the turbulence levels associated with the gate valve opening fraction.
The initial spike in these values is most likely the result of the gate valve losses.
Conclusions about the design •
Unfortunately, this area in particular was not realized due to the existence of the current draft pipe installation. During turbine operation, an unexpectedly high degree of heating of the thrust bearing occurred. It is therefore recommended to place the meters halfway up the side of the pipe.
Due to the difference in the bearing loads, it is advisable to change the bearings when servicing the pump. Since the only two forces acting on the blade are twisting of the flow and drag. Since the values of head, diameter and power have been preset by the location of the turbine site.
Conclusions about the experimental results
Recom. mendations
Further filtering of the water – such as making the grid at the entrance of the inlet pipe slightly finer. A line was tapped from the high-pressure side of the stream, passed through the water jacket and returned to the low-pressure side. The same applies to the manometers, but this applies more to the filling of the meter itself, where it is necessary to let the air escape from the meter.
The final results in Figure 5.4.11 show the overlap of valve, turbine and draft tube efficiencies.
Curtain plate
Since the curtain plate is located along the axis of the arch and subtends only 45°, we can expect the force acting on the curtain plate to be equal A to that acting on the pipe. The plate affects only half of the twist angle of the tube and half of the liquid volume.
Bearing Design
However, in later design stages it was independently determined that the rotational speed of the turbine had to be increased to llOOrpm. The first phase of the design determines the area in which the blades will work. This is predetermined by the constraints set by the project supervisor for the pipe diameter and the required size of the nose cone.
This means that the diameter of the turbine is an issue when designing for best efficiency. The reason for this was to initialize the blade shape programming for the CNC machining process. It is a list of the components involved in the construction of the turbine and does not include the procedures necessary for the manufacture of the individual components.
