Steam boiler

Steam boiler is a closed vessel into which water is heated until the water is converted into steam at required pressure. Water is stored inside the vessel and fuel (coal) is bunt in hot furnace to produce hot gas. These hot gas then comes in contact with the vessel. The heat from the hot gas is transferred to the water in the vessel and steam is produced in the boiler. Then this steam is piped to the turbine of thermal power plant.

The efficiency of Steam Boiler is the percentage of total heat exported by outlet steam to the total heat supplied by the fuel. Typical efficiency of steam boiler is 80% to 88%. The efficiency depends upon the size of the boiler used.

Some of the important term of a steam boiler are Boiler Shell, Combustion Chamber, Furnace, Grate,Heating Surface Mounting and Accessories. Boiler shell is made up of steel plates. It should have sufficient capacity to contain water and steam. Below the boiler shell is the Combustion Chamber, meant for burning the fuel. Grate is a platform in the combustion chamber, upon which fuel (coal or wood) is burnt. Above the grate and below the boiler shell is the furnace in which fuel is actually burned.

Heating Surface is the part of boiler surface, which is exposed to fire. Fittings which are mounted on the boiler for the proper functioning are called mountings. Boiler cannot function safely without the mountings. Accessories are devices which are integral part of a boiler, but are not mounted on it. Accessories help in controlling and running the boiler efficiently.

Fire Tube Boiler and Water Tube Boiler are two main types of boiler. Fire tube boiler consists of numbers of tubes through which hot gasses are passed. These hot gas tubes are immersed into water, in a closed vessel. The water in the vessel is heated by the hot gas tubes and is converted into steam. The steam remains in the same vessel. Therefore this boiler cannot produce steam at very high pressure. It can produce maximum of 17.5 kg/cm² and with a capacity of 9 Metric Ton of steam per hour. Water Tube Boilers are opposite of Fire Tube Boilers where water is heated inside tubes and the hot gas surrounds them.

Autonomous Robots

Autonomous robots may be characterized as intelligent machines capable of performing tasks in unstructured environments without explicit or continuous human control over their movements. Concepts range from small insect-like machines to highly sophisticated humanoid robots with social intelligence and awareness of their environment.

An autonomous robot can sense and gain information about its surroundings, work and move either part or all of itself for an extended period without human assistance, and avoid situations that are harmful to people, property, or itself. It may also learn, or gain new capabilities, like adapting to changing conditions or adjusting strategies for accomplishing its tasks.

New categories of autonomous and mobile robots have been developed that can significantly expand the applications of robotics.

Cognitive robots are endowed with artificial reasoning skills to achieve complex goals in complex environments. Cognitive robots can be used in manufacturing and as home helpers, caregivers, or emergency and rescue aids. They are also useful for space missions.

Moving On Their Own – A flying robot stars in a Microsoft video for young people interested in computer science

A number of research projects are focused on cognitive robotic systems, including the European Union’s project CoSy—Cognitive Systems for Cognitive Assistants—aimed at developing robots that are more aware of their environment and better able to interact with humans. Another is provided by the cognitive robot companion in the Cogniron Project of the French National Center for Scientific Research. The project aims at developing a robot that would serve humans in their daily lives. It would exhibit cognitive capabilities for adapting its behavior to changing situations and for various tasks.

Neurorobotics couples neuroscience with robotics. The overall goals of the activity are to develop high-performance, human-centered robotic systems to serve as physical platforms for validating biological models. Current activities are focused on developing robotic devices with control systems that mimic the nervous system, such as brain-inspired algorithms and models of biological neural networks.

The field of evolutionary robotics emerged from the idea of allowing robots to evolve. Although the field shares many of the insights of artificial life, which pioneered the use of genetic algorithms in the 1970s and 1980s, evolutionary robotics is distinguished by its insistence on making the leap from computer animations to physical machines. Evolutionary robotics aims at developing robots that acquire their own skills through close interaction with the environment. Evolutionary computational tools like neural networks, genetic algorithms, and fuzzy logic are used in developing intelligent autonomous controllers for robots.

Types of Turbines

Turbines can be classified according to the direction of the water flow through the blades, e.g. radial, axial or combined flow turbines, or as reaction, impulse or mixed-flow turbines. In reaction turbines there is a change of pressure across the turbine rotor, while impulse turbines use a high velocity jet impinging on hemispherical buckets to cause rotation. 

There are three basic types of turbine broadly related to low, medium or high heads.
Propeller or axial flow turbines are used for low heads in the range from 3 to 30 meters. They can have relatively inexpensive fixed blades, which have a high conversion efficiency at the rated design conditions but a poorer par€-load efficiency, typically 50%, at one third of full rated output.
Alternatively, the more expensive Kaplan turbine has variable-pitch blades which can be altered to give much better part-load efficiency, perhaps 90% at one third of full rated output. The Francis turbine is a mixed-flow radial turbine and is used for medium heads in the range from 5 to 400 m. It has broadly similar performance characteristics to the fixed-blade propeller type and its speed is controlled by adjusting the guide vane angle. The best-known impulse turbine is the Pelton wheel.
Each bucket on the wheel has a centrally placed divider to deflect half the flow to each side of the wheel. It is normally used for heads greater than 50 m and has good performance characteristics over the whole range, very similar to the Kaplan turbine, reaching 60% efficiency at one-tenth of full rated output.
The speed is controlled by a variable inlet nozzle, so that with a constant head, the delivered torque to the generator is proportional to the flowrate and the turbine speed can be held at that required for synchronous generation at the particular grid frequency. This type of installation is known as a constantspeedkonstant- frequency system and optimization of the power output is relatively easy. I1O In smaller installations, optimum power cannot be obtained at constant speed where the hydraulic head is both relatively low and variable over a wide range.
A detailed description of methods which can be used for optimizing electric power from small-scale plant has been given by Levy.”’ He points out that small hydroelectric systems will become more financially attractive through developments of low-cost power converters (from 100 W upwards), special variable-speedkonstant-frequency generators and cheap computing units for on-line power measurement and optimizing control. This means that many run-of-the-river sites that were considered in the past to be unsuitable for electricity generation can now be used