What are the operating parameters of a water turbine?
The basic working parameters of a water turbine include head, flow rate, speed, output, and efficiency.
The water head of a turbine refers to the difference in unit weight water flow energy between the inlet section and the outlet section of the turbine, expressed in H and measured in meters.
The flow rate of a water turbine refers to the volume of water flow passing through the cross-section of the turbine per unit time.
The turbine speed refers to the number of times the main shaft of the turbine rotates per minute.
The output of a water turbine refers to the power output at the shaft end of the water turbine.
Turbine efficiency refers to the ratio of turbine output to water flow output.
What are the types of water turbines?
Water turbines can be divided into two categories: counterattack type and impulse type. The counterattack turbine includes six types: mixed flow turbine (HL), axial-flow fixed blade turbine (ZD), axial-flow fixed blade turbine (ZZ), inclined flow turbine (XL), through flow fixed blade turbine (GD), and through flow fixed blade turbine (GZ).
There are three forms of impulse turbines: bucket type (cutter type) turbines (CJ), inclined type turbines (XJ), and double tap type turbines (SJ).
3. What are counterattack turbine and impulse turbine?
A water turbine that converts the potential energy, pressure energy, and kinetic energy of water flow into solid mechanical energy is called a counterattack water turbine.
A water turbine that converts the kinetic energy of water flow into solid mechanical energy is called an impulse turbine.
What are the characteristics and scope of application of mixed flow turbines?
A mixed flow turbine, also known as a Francis turbine, has water flow entering the impeller radially and flowing out generally axially. Mixed flow turbines have a wide range of water head applications, simple structure, reliable operation, and high efficiency. It is one of the most widely used water turbines in modern times. The applicable range of water head is 50-700m.
What are the characteristics and scope of application of the rotating water turbine?
Axial flow turbine, the water flow in the impeller area flows axially, and the water flow changes from radial to axial between the guide vanes and the impeller.
The fixed propeller structure is simple, but its efficiency will sharply decrease when deviating from the design conditions. It is suitable for power plants with low power and small changes in water head, generally ranging from 3 to 50 meters. The rotary propeller structure is relatively complex. It achieves dual adjustment of the guide vanes and blades by coordinating the rotation of the blades and the guide vanes, expanding the output range of the high-efficiency zone and having good operational stability. At present, the range of applied water head ranges from a few meters to 50-70m.
What are the characteristics and scope of application of bucket water turbines?
A bucket type water turbine, also known as a Petion turbine, does work by impacting the bucket blades of the turbine along the tangential direction of the turbine circumference with the jet from the nozzle. The bucket type water turbine is used for high water heads, with small bucket types used for water heads of 40-250m and large bucket types used for water heads of 400-4500m.
7. What are the characteristics and scope of application of inclined turbine?
The inclined water turbine produces a jet from the nozzle that forms an angle (usually 22.5 degrees) with the plane of the impeller at the inlet. This type of water turbine is used in small and medium-sized hydropower stations, with a suitable head range below 400m.
What is the basic structure of a bucket type water turbine?
The bucket type water turbine has the following overcurrent components, whose main functions are as follows:
(l) The nozzle is formed by the water flow from the upstream pressure pipe passing through the nozzle, forming a jet that impacts the impeller. The pressure energy of the water flow inside the nozzle is converted into the kinetic energy of the jet.
(2) The needle changes the diameter of the jet sprayed from the nozzle by moving the needle, thus also changing the inlet flow rate of the water turbine.
(3) The wheel is composed of a disc and several buckets fixed on it. The jet rushes towards the buckets and transfers its kinetic energy to them, thereby driving the wheel to rotate and do work.
(4) The deflector is located between the nozzle and the impeller. When the turbine suddenly reduces the load, the deflector quickly deflects the jet towards the bucket. At this point, the needle will slowly close to a position suitable for the new load. After the nozzle stabilizes in the new position, the deflector returns to the original position of the jet and prepares for the next action.
(5) The casing allows the completed water flow to be smoothly discharged downstream, and the pressure inside the casing is equivalent to atmospheric pressure. The casing is also used to support the bearings of the water turbine.
9. How to read and understand the brand of a water turbine?
According to the JBB84-74 “Rules for the designation of turbine models” in China, the turbine designation consists of three parts, separated by a “-” between each part. The symbol in the first part is the first letter of the Chinese Pinyin for the type of water turbine, and Arabic numerals represent the characteristic specific speed of the water turbine. The second part consists of two Chinese Pinyin letters, the first representing the layout of the main shaft of the water turbine, and the latter representing the characteristics of the intake chamber. The third part is the nominal diameter of the wheel in centimeters.
How are the nominal diameters of various types of water turbines specified?
The nominal diameter of a mixed flow turbine is the maximum diameter on the inlet edge of the impeller blades, which is the diameter at the intersection of the lower ring of the impeller and the inlet edge of the blades.
The nominal diameter of axial and inclined flow turbines is the diameter inside the impeller chamber at the intersection of the impeller blade axis and the impeller chamber.
The nominal diameter of a bucket type water turbine is the pitch circle diameter at which the runner is tangent to the main line in the jet.
What are the main causes of cavitation in water turbines?
The causes of cavitation in water turbines are relatively complex. It is generally believed that the pressure distribution inside the turbine runner is uneven. For example, if the runner is installed too high relative to the downstream water level, the high-speed water flow passing through the low-pressure area is prone to reach the vaporization pressure and produce bubbles. When the water flows into the high-pressure zone, due to the increase in pressure, the bubbles condense, and the water flow particles collide at high speed towards the center of the bubbles to fill the gaps generated by condensation, thereby generating great hydraulic impact and electrochemical effects, causing the blades to be eroded, resulting in pitting and honeycomb like pores, and even being penetrated to form holes.
What are the main measures to prevent cavitation in water turbines?
The consequence of cavitation in water turbines is the generation of noise, vibration, and a sharp decrease in efficiency, which leads to blade erosion, the formation of pitting and honeycomb like pores, and even the formation of holes through penetration, resulting in damage to the unit and inability to operate. Therefore, efforts should be made to avoid cavitation during operation. At present, the main measures to prevent and reduce cavitation damage include:
(l) Properly design the turbine runner to reduce the cavitation coefficient of the turbine.
(2) Improve manufacturing quality, ensure correct geometric shape and relative position of blades, and pay attention to smooth and polished surfaces.
(3) Using anti cavitation materials to reduce cavitation damage, such as stainless steel wheels.
(4) Correctly determine the installation elevation of the water turbine.
(5) Improve operating conditions to prevent the turbine from operating at low head and low load for a long time. It is usually not allowed for water turbines to operate at low output (such as below 50% of rated output). For multi unit hydropower stations, long-term low load and overload operation of a single unit should be avoided.
(6) Timely maintenance and attention should be paid to the polishing quality of repair welding to avoid the malignant development of cavitation damage.
(7) Using an air supply device, air is introduced into the tailwater pipe to eliminate excessive vacuum that may cause cavitation.
How are large, medium, and small power stations classified?
According to current departmental standards, those with an installed capacity of less than 50000 kW are considered small; Medium sized equipment with an installed capacity of 50000 to 250000 kW; An installed capacity greater than 250000 kW is considered large.
What is the basic principle of hydroelectric power generation?
Hydroelectric power generation is the use of hydraulic power (with water head) to drive hydraulic machinery (turbine) to rotate, converting water energy into mechanical energy. If another type of machinery (generator) is connected to the turbine to generate electricity as it rotates, the mechanical energy is then converted into electrical energy. Hydroelectric power generation, in a sense, is the process of converting the potential energy of water into mechanical energy and then into electrical energy.
What are the development methods of hydraulic resources and the basic types of hydropower stations?
The development methods of hydraulic resources are selected according to the concentrated drop, and there are generally three basic methods: dam type, diversion type, and mixed type.
(1) A dam type hydropower station refers to a hydroelectric power station built in a river channel, with a concentrated drop and a certain reservoir capacity, and located near the dam.
(2) A water diversion hydropower station refers to a hydropower station that fully utilizes the natural drop of the river to divert water and generate electricity, without a reservoir or regulating capacity, and is located on a distant downstream river.
(3) A hybrid hydropower station refers to a hydroelectric power station that utilizes a drop of water, partially formed by dam construction and partially utilizing the natural drop of a river channel, with a certain storage capacity. The power station is located on a downstream river channel.
What are flow, total runoff, and average annual flow?
Flow rate refers to the volume of water passing through the cross-section of a river (or hydraulic structure) per unit time, expressed in cubic meters per second;
The total runoff refers to the sum of the total water flow through the section of a river in a hydrological year, expressed in 104m3 or 108m3;
The average annual flow rate refers to the average annual flow rate Q3/S of a river section calculated based on existing hydrological series.
What are the main components of a small hydropower station hub project?
It mainly consists of four parts: water retaining structures (dams), flood discharge structures (spillways or gates), water diversion structures (diversion channels or tunnels, including pressure regulating shafts), and power plant buildings (including tailwater channels and booster stations).
18. What is a runoff hydropower station? What are its characteristics?
A power station without a regulating reservoir is called a runoff hydropower station. This type of hydropower station selects its installed capacity based on the average annual flow rate of the river channel and the potential water head it can obtain. The power generation during the dry season sharply decreases, less than 50%, and sometimes even cannot generate electricity, which is constrained by the natural flow of the river, while there is a large amount of abandoned water during the wet season.
19. What is output? How to estimate the output and calculate the power generation of a hydropower station?
In a hydropower station (plant), the power generated by the hydro generator unit is called output, and the output of a certain section of water flow in a river represents the water energy resources of that section. The output of water flow refers to the amount of water energy per unit time. In the equation N=9.81 η QH, Q is the flow rate (m3/S); H is the water head (m); N is the output of the hydropower station (W); η is the efficiency coefficient of the hydroelectric generator. The approximate formula for the output of small hydropower stations is N=(6.0-8.0) QH. The formula for annual power generation is E=NT, where N is the average output; T is the annual utilization hours.
What is the annual utilization hours of installed capacity?
Refers to the average full load operation time of a hydroelectric generator unit within a year. It is an important indicator for measuring the economic benefits of hydropower stations, and small hydropower stations are required to have an annual utilization hour of over 3000 hours.
21. What are daily adjustment, weekly adjustment, annual adjustment, and multi-year adjustment?
(1) Daily regulation: refers to the redistribution of runoff within a day and night, with a regulation period of 24 hours.
(2) Weekly adjustment: The adjustment period is one week (7 days).
(3) Annual regulation: The redistribution of runoff within one year, where only a portion of the excess water during the flood season can be stored, is called incomplete annual regulation (or seasonal regulation); The ability to fully redistribute incoming water within the year according to water usage requirements without the need for water abandonment is called annual regulation.
(4) Multi year regulation: When the reservoir volume is large enough to store excess water during many years in the reservoir, and then allocate it to several dry years for annual regulation, it is called multi-year regulation.
22. What is the drop of a river?
The elevation difference between the two cross-sections of the river section being utilized is called the drop; The elevation difference between the water surfaces at the source and mouth of the river is called the total drop.
23. What is the precipitation, precipitation duration, precipitation intensity, precipitation area, rainstorm center?
Precipitation is the total amount of water that falls on a certain point or area during a certain period of time, expressed in millimeters.
Precipitation duration refers to the duration of precipitation.
Precipitation intensity refers to the amount of precipitation per unit time, expressed in mm/h.
The precipitation area refers to the horizontal area covered by precipitation, expressed in km2.
The rainstorm center refers to a small local area where rainstorm is concentrated.
24. What is an engineering investment estimate? Engineering investment estimation and engineering budget?
Engineering budget is a technical and economic document that compiles all the necessary construction funds for a project in monetary form. The preliminary design budget is an important component of the preliminary design documents and the main basis for assessing economic rationality. The approved overall budget is an important indicator recognized by the state for basic construction investment, and it is also the basis for preparing basic construction plans and bidding designs. Engineering investment estimation is the investment amount made during the feasibility study stage. The engineering budget is the investment amount made during the construction phase.
What are the main economic indicators of hydropower stations?
(1) Unit kilowatt investment refers to the investment required per kilowatt of installed capacity.
(2) Unit energy investment refers to the investment required per kilowatt hour of electricity.
(3) The cost of electricity is the fee paid per kilowatt hour of electricity.
(4) The annual utilization hours of installed capacity are a measure of the utilization level of hydropower station equipment.
(5) The selling price of electricity is the price per kilowatt hour of electricity sold to the grid.
How to calculate the main economic indicators of hydropower stations?
The main economic indicators of hydropower stations are calculated according to the following formula:
(1) Unit kilowatt investment=total investment in hydropower station construction/total installed capacity of hydropower station
(2) Unit energy investment=total investment in hydropower station construction/average annual power generation of hydropower station
(3) Annual utilization hours of installed capacity=average annual power generation/total installed capacity
Post time: Oct-28-2024
