Steam Boilers & Engines Exam Questions - Mechanical Engineer

Description

Mechanical engineering is a branch of engineering that applies engineering physics and mathematics to the design, analysis, construction, and maintenance of mechanical systems. It is one of the oldest and most diverse fields of engineering.

Mechanical engineering involves a working knowledge of fundamental subjects such as mechanics, dynamics, thermodynamics, materials science, structural analysis, and electricity.

Steam Boiler

A Steam Boiler is a closed vessel that is used to heat a fluid (usually water). The liquid does not have to boil. The heated or vaporized fluid is then discharged from the boiler for use in a variety of operations or heating applications, including cooking, water or central heating, and boiler-based power generation. Boilers (or, more precisely, steam boilers) are a critical component of thermal energy plants.

Working Principle of Boiler

The boiler's fundamental operation is really straightforward and simple to comprehend. The boiler is essentially a closed vessel that contains water. In a furnace, fuel (usually coal) is burned and hot gases are created.

These heated gases come into contact with a water vessel, where their heat is transferred to the water, resulting in the production of steam in the boiler.

The steam is then delivered to the thermal power plant's turbine. There are numerous varieties of boilers that are used for a variety of functions such as powering a production unit, cleaning an area, sterilising equipment, and warming the surrounding region.

Boilers are classified into two types: water-tube boilers and fire tube boilers.

There are numerous tubes in a fire tube boiler through which hot gases are transferred, and water surrounds these tubes.

Water-tube boilers are the polar opposite of fire tube boilers. In a water tube boiler, water is heated inside tubes, which are surrounded by hot gases.

Steam Engine

A steam engine is a type of heat engine that uses steam as its working fluid to produce mechanical work. The steam engine works by pushing a piston back and forth inside a cylinder using the force generated by steam pressure. This pushing power can be converted to rotational force for work via a connecting rod and flywheel. The word "steam engine" is most commonly used to refer to reciprocating engines, not to the steam turbine. External combustion engines, such as steam engines, separate the working fluid from the combustion products. The Rankine cycle is the optimum thermodynamic cycle utilised to examine this process. The phrase "steam engine" can refer to either whole steam plants (including boilers and other components), such as railway steam locomotives and portable engines, or to the piston or turbine mechanism alone, as in the beam engine and stationary steam engine.

In a steam engine, heated steam, which is typically supplied by a boiler, expands under pressure, converting some of the heat energy to work. The remaining heat may be allowed to escape or, for best engine efficiency, the steam may be condensed at a relatively low temperature and pressure in a separate unit called a condenser. To achieve maximum efficiency, the steam must pass through a wide temperature range as it expands within the engine. Utilizing a low condenser temperature with a high boiler pressure results in the most efficient performance—that is, the maximum production of work per unit of heat supplied. On its way from the boiler to the engine, the steam can be further heated by passing it through a superheater. A common superheater is a collection of parallel pipes exposed to the hot gases in the boiler furnace. Steam can be heated above the temperature at which it is produced by boiling water using superheaters.

A reciprocating engine, often known as a piston and cylinder steam engine, admits steam under pressure into the cylinder via a valve mechanism. Steam expands and pushes the piston, which is typically attached to a crank on a flywheel to generate rotary motion. Steam from the boiler is fed alternately to either side of the piston in a double-acting engine. In a simple steam engine, the steam is expanded in a single cylinder, whereas in a compound engine, the steam is expanded in two or more cylinders of increasing size for greater efficiency; the first and smallest piston is operated by the initial high-pressure steam, while the second and largest piston is operated by the lower-pressure steam exhausted from the first.

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