Chapter 3: Methodology
3.1 Introduction
The methodology section covers information about data collection methods and data analysis. It explains how pressure kinetic energy is converted to useful energy rather than just sending it to the surge tank for storage. For the most part, quantitive data is used to test whether it is possible to use the excess pressure of water hammer even though it often causes damage. The calculation of the water hammer is based on the conservation of mass and momentum. The magnitude of power that causes pipes to burst is measured by mass and velocity. Besides, experimental data is gathered via manipulation and controlling variables.
3.2 Research design
3.2.1 Research questions
What benefits will be gained from reusing the pressure?
Why is the converted power being stored?
How is the converted power going to be used?
Where is the converted power going to be used?
What are the design principles of water hammer control strategies?
What is the machinery used to achieve the proposed solution?
How does the water hammer energy system operate?
Is it possible to harness excess pressure of water hammer to useful work despite its potentially damaging effects?
How can power from the water hammer be determined?
3.2.2 Unit of Analysis
The unit of analysis in this study is the Hydraulic Surge Analysis.
3.3 Data collection-technique that will be used, issues, context
3.3.1 DAQ system
The estimating framework utilized is a 2 x 16 channels DAQ framework to test all the sensors’ signals. Eight channels can test at 50 kHz while the rest at 300 kHz. At 0.05 ms or instead, a sampling frequency of 20 kHz is adequate. At that point, one can resolve a pressure wave, which happens during 1 ms with ten focuses. A LabView program is to be used to collect all the signals. Strain gauges, pressure sensors, and flow meters are the measuring devices.
According to the manufacturer, the frequency response is quantified to 180kHz while the uncertainty is plus or minus 0.25 percent for the pressure sensors. The names of the positions and sensor positions are recorded in the table below. Table 3.1
| Position | Positions’ name |
| The region at the center of the pump and valve | A1 |
| Upstream from the valve | A2 |
| Before the bend of 180 degrees | A3 |
| After the bend of 180 degrees | A4 |
| The area between the tank and the flow meter | A5 |
| The area near the tank before the S-shaped pipe | A6 |
| The area near the tank after the S-shaped pipe | A7 |
| Center of the pipe above | A8 |
Installed after the pump are two electromagnetic flowmeters (Dutta et al., 2020). Regulation of the speed that is generated by the pump is one purpose of the stream meter. The other one is utilized for estimations and, at first, to consider the chance of estimating the transient conduct of the flow. The stream meters have an estimation uncertainty of about 0.5 % as per the ongoing alignment at SP see Appendix C. The speed in the DN50 flow meter is about 1.2 m/s. At stream rates lower than that, the vulnerability in the stream estimation will rise.
| Position | Position’s Name |
| At the center of the pump and | B1 |
| Immediately after B1 | B2 |
3.3.2 Measurement of Surge Tank Oscillations.
Oscillation measurement in surge tanks is done using logarithmic decrement by using a formula; δ = ln (x1 / x2), where δ is the oscillations, ln is the logarithm to the base e, and x represents the amplitude of two successive surges. Equivalently, there is a formula; δ = ln [(a1 + a2) / (a3 + a4)], which gives the same results as that of the logarithmic decrement. In the formula, a is the surge heights that are above and below the initial steady water surface in a sequence.
3.3.3 Water hammer analysis in the presence of a surge tank
The working of a flood tank under various burden conditions in a hydroelectric force plant varies. The surge tank’s primary elements are: Taking up the excess water when the load is diminished and giving additional water when the heap is expanded. Besides, Minimization of water hammer impacts the pipelines driving from penstock to the turbines. Taking up the excess water when the load is diminished and giving additional water when the heap is expanded.
Water hammer analysis without Surge Tank. In this case, the load on the plant was rejected due to the grid failure, and the turbines were shut down as per their regular closing time. Just before the load rejection, both of the two turbine units were working steadily with the discharge of 6.643 m3/sec. When the turbine shut down due to load rejection, the valve closed completely for turbine safety. WH increases after the sudden closure of the valve in an emergency or grid failure conditions.
3.3.4 Water Hammer analysis in the absence of a surge tank
In this case, the load on the plant was dismissed because of the framework disappointment, and the turbines were closed down according to their ordinary shutting time. Not long before the load dismissal, both of the two turbine units were working consistently with the release of 6.643 m3/sec. At the point when the turbine shut down because of load dismissal, the valve shut totally for the safety of the turbine. The expanded WH head after the abrupt conclusion of the valve in crisis or grid failure condition, which was calculated using the Michaud-Alleivi equation.
3.4 Data analysis techniques
In hydropower plants, water hammers can be computed by the use of the rigid or elastic theory of water hammer theory. For systems with comparatively lengthy penstocks and tunnels, the elastic liquid column model is utilizing (Salimi el., 2020). The elastic column model assumes elastic pipes and slightly compressible fluid.
The investigative measurements of pressure estimations are shown comparatively with the nearby local pressure at the fixed stream before the water hammer. The positive wave of the water hammer will go upstream until it is mirrored in the reservoir. The wave took more than thirty seconds for the wave to be fully damped. The first positive pressure peak produces a sound that is roughly ±10 %. The source of the sound will be discussed in more detail.
A fundamental water hammer equation by Joukowsky is used to compute pressure waves to obtain a pressure amplitude of ρ·∆V ·c. A lower amplitude is depicted by low sound speed. The elastic water pipe expands because of amplified pressure, causing a wave to appear in the structure. The structural wave is about four times faster as compared to the one in the field. There is an interaction between the structure and the fluid, thus leading to a slow wave speed than the water’s sonic speed.
A comparison between the presence of a water hammering analysis both in the presence of a surge tank power and absence of a surge tank indicates a huge difference in power generation.
3.4.1 Benefits of reusing pressure
Reusing pressure in a water hammering system has various advantages or benefits to the plant. There is a reduction of needs required to run the whole process due to saving energy and raw materials needed hence reducing the total cost of operation. Additionally, reusing pressure will reduce the magnitude of damages caused by the pressure if released from the system because the pressure is stored with the system and then reused without being released outside the system (Zhao et al., 2019).
3.4.2 Machinery used in water hammer systems.
Shell and tube heat exchangers are equipment used to achieve the proposed solution in the water hammering system. At the point when the weight of the equipment drops because of elements such as a decrease in the measure of the item to be warmed or the rising of the item’s temperature, the weight differential between the snare channel and source pressures vanishes, and condensate begins to pool inside the shell. This sensation is known as ‘slow down.’ Depending on back weight, the shell can likewise turn out to be brimming with condensate when the hardware is closed down. When steam is applied to a zone with a significant level of condensation, it immediately consolidates, and water hammer happens. As a rule, this outcomes in little scope impact over a short period, not like the savage effects in steam circulation lines. Other machineries used in this system are Hydraulic ram pumps.
3.4.3 Storage and usage of power converted.
Converted power from water hammering systems is stored in pumped storage stations. Therefore, the storage stations control and regulate the capacity of power transmitted to various electrical companies to avoid high voltage, which may cause damages and loss of life. The electric power produced from the water hammering system is used for residual purposes such as lighting, water heating, computing, industrial use, and transportation.
3.4.4 Design principles of water hammer control strategies.
Huge passing weights may interrupt the general activity of the hydropower plant and harm the framework parts. The following are design approaches used; adjustment of operational systems, Redesign of the flow passage system layout, and the establishment of surge control gadgets.
3.4.4.1 Adjustment of operation systems
Adjustment of operational systems incorporates applicable guidelines of the wicket entryway and runner cutting edge moves in response turbines, and turbine distributor and stream redirector move in drive turbines. Normally a two-speed wicket entryway shutting time work fundamentally improves response turbine safe activity. Opening of sprinter sharp edges during Kaplan or bulb turbine closure brings about positive edge activity, improved over-speed execution, and decreased negative hub water-driven push. The fitting setting of shutting/opening occasions of the shutoff valves adds to these gadgets’ more certain activity in crisis and great working conditions. A draft tube door can be utilized to secure a pivotal turbine against rampant. Also, sluicing activity of the low-head pivotal turbines can constrict open channel waves during transient systems. The constraint of working systems (diminished release) is one more choice. This measure might be considered as the transitory one preceding a more powerful strategy is concocted.
3.4.4.2 Establishment of surge control gadgets.
The establishment of flood control gadgets changes the framework attributes as it abbreviates the dynamic channel length, lessens the fluid compressibility, and increment the turbine unit latency. The defensive gadgets that might be introduced along the delta and source channel or added to the hydropower framework parts include:
(1) air pad flood chamber (requires packed air gracefully),
(2) expanded turbine unit dormancy (adding flywheel to the dynamic conductor length, improves administering steadiness),
(3) break plate (blasts at a set weight, little units expanding the generator latency),
(4) air circulation pipe (weakens water section partition
(5) pressure-managing valve (works simultaneously with the turbine wicket entryways),
(6) pressure-alleviation valve (opens at a set weight, little units
(7) air valve (lessens water segment detachment, decreases negative pivotal water-driven push).
(8) resistors (to retain unnecessary force),
(9) flood tank in headrace or potentially tailrace.
3.4.4.3 Restructure of the flow channel system arrangement
Redesign of the stream entry framework plan incorporates:
(1) the difference in channel measurements (length, diameter);
(2) the distinctive situation of framework parts (valve)
(3) the difference in water movement profile (high point);
Operational, well-being, and monetary components are definitive for determining insurance against the unfortunate water hammer impacts. Various choices should be explored before the final plan. The most helpful water hammer control strategy in the hydropower plant is the adjustment of operational systems. It is costly to introduce extra flood control gadgets in the framework, aside from the principal strategy. It is infrequently possible to overhaul the proposed stream section framework. Water hammer control gadgets ought to work easily in ordinary working conditions. These conditions incorporate load decrease, the turbine fire up, load acknowledgment, load decrease, and load dismissal (speedy mechanical stop, electrical crisis closure). Crisis conditions are load dismissals in which the sprinter cutting edges (pivotal and corner to corner turbines) neglect to work or partial control happens. The turbine runaway is considered a disastrous transient system. Water hammer examination should be performed for ordinary, crisis, and disastrous working conditions.
3.4.5 Operation of water hammer energy system.
A water hammer regularly happens in a steam framework when a portion of the steam gathers into the water in an even part of the funneling. The remainder of the steam gets the water, shaping a “slug,” and throws this at high speed into a conduit fitting, making a noisy pounding commotion and enormously focusing on the conduit. Water siphons are fit for working as turbines for power production. With the appropriate adjustment, slam siphons are no exemption. By supplanting the conveyance line and compression vessel with an open hydrant viably making a basic flood tank upstream of an occasionally shutting valve, it is conceivable to utilize the thought behind a slam to catch any overabundance pressure at the chamber. The water hammer itself will give the heft of this weight. Anyway, the water in the chamber will also waver with the flood because of the protection of mass.
3.4.6 Determination of power produced from water hammer system.
The size of the plant determines the capacity of power produced in the water hammer system. Huge power plants usually use advanced and heavy machinery in the production of power. Therefore, they can produce a high capacity of power compared with small power plants (Zhang et al., 2019). Alternatively, the amount of power can be determined by the users’ demand, where if the demand is high, more power will be produced and vice versa.
3.4.7 Harness of excess pressure of water hammer.
The water hammer happens when a liquid is exposed to an unexpected change in force and is a type of temperamental stream described by sharp ascents in pressure. It ordinarily happens in pipelines during valve tasks, where it can cause issues, for example, cavitation, noise, and even pipe breakdown in extraordinary cases. In this way, the water hammer is viewed regularly as risky, and most current line frameworks utilize flood tanks, slow shutting valves, or other protection structures to limit its size or magnitude of damage.
3.4.8 Conversion of pressure KE to useful energy instead of sending it to surge tank only for accommodating.
The pressure produced in the water hammer system is used in the generation of heat energy. The heat energy produced is used for various heating and cooking purposes instead of stored in a surge tank.
3.5 Methodological limitations
Mistakes may be made during mathematical computations. Therefore, the results may be inaccurate. Measures used to correct data may be misleading or inaccurate. Also, during data collection, wrong data may be filled, and that would result in wrong results.
3.6 Summary of the chapter.
Water hammer in hydropower plants is caused by turbine load acknowledgment and decrease, load dismissal under lead representative control, crisis closure and undesirable runaway, and conclusion and opening of the security shutoff valve. It prompts pressure rise or drops in water-driven frameworks, rotational speed variety in pressure-driven turbomachinery (siphons and water turbines), and level change in flood tanks and air chambers. The paper presents plan standards of water hammer control methodologies (alleviation of unreasonable loads), including operational situations (shutting and opening laws), flood control gadgets (flywheel, flood tank, managing valve, air valve, and so on), and upgrade of the pipeline parts. Old style hypothetical water hammer models and arrangements are quickly talked about in the light of their ability and accessibility.
Reference
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