Department of Mechanical Engineering, UET Peshawar

Steam Engine

Presentation by: Muhammad Fahad

Khan Abdul Rizwan Rahat Saeed Fahim Ullah Fazal Haq

Contents

Introduction to Steam EngineTypes of Steam EngineParts of Steam EngineWorking of Steam EngineAdvantages, Disadvantages & Uses of Steam Engine

Outlines Introduction to steam engine Growth of the steam engine

Opening Temple-Doors by Steam Brancas Steam-Engine, A.D. 1629

The Steam Engine as a train mechanism Newcomen's Engine, A. D. 1705

The development of modern steam engine JAMES WATT

The Modern Steam Engine and application to locomotives

Introduction to Steam Engine

Introduction

Steam engine is an external combustion heat engine in which steam is used as a working fluid.

Heat engine works on first law of thermodynamics i.e heat energy is converted to mechanical work.

It is among the ancient Egyptian civilization that we find the first records in the early history of the steam-engine.

Growth of the Steam Engine Opening Temple-Doors

by Steam

HERO, a learned writer in ancient Egyptian civilization

Spherical vessel containing water

A pipe connects the upper part of this sphere with the hollow and air-tight shell.

Fire on the altar, the heated air expands

On extinguishing the fire, the air condenses, the water returns from the bucket to the sphere

Growth of the Steam Engine conti..

Brancas Steam-Engine. A.D. 1629

Metal vessel partly filled with water

Pipe fitted, leading nearly to the bottom, and open at the top

Fire being applied, the steam formed by drove the water out through the vertical pipe

The Steam Engine as a train mechanism

Newcomen's Engine, A. D. 1705

A jet of water was thrown directly into the cylinder, thus effecting for the Newcomen engine

A jet of water from the reservoir, g, enters the cylinder, producing a vacuum by the condensation of the steam

The Development Of Modern Steam Engine “JAMES WATT”

Watt's Experiment

14‑inch diameter and 10 inches long brass surgeon's syringe.

At each end was a pipe leading steam from the boiler, and fitted with a cock to act as a steam valve.

A pipe led also from the top of the cylinder to the condenser.

The Modern Steam Engine

Leopold's Engine, 1720

Two single‑acting cylinders

Receives steam alternately from the same steam‑pipe through a " four‑way cock," and exhausts into the atmosphere.

The alternate action of the steam pistons is secured by turning the four‑way cock into the reverse position

Steam Engine To Locomotives

Newton's Steam‑Carriage,1680

Spherical boiler mounted on a carriage.

Reaction on the carriage, drives the latter ahead.

The driver controls the steam by the handle and cock.

Steam Engine To Locomotives

Read's Steam Carriage, 1790

A A A A are the wheels; B B, pinions on the hubs of the rear wheels .

CO is the boiler.

Cocks, serve to shut off steam from the engine .

Objectives:

Reciprocatory Engines

Single Stage Reciprocatory

Engines

Compound Engines

Turbine Engines

Stationary Engines

Types Of Steam Engine

Classification

Steam engines can be classified in two main ways:

By the technology used

By the application

By The Technology:

Most steam engines use either

Piston Engines

Turbines

By The Application:

By application the steam engines are classified further into two main groups:

Engines providing power, which stop rarely and do not need to reverse i.e. power stations

Engines that frequently stop and reverse i.e. stationary engines

Reciprocatory Engine:

These engines are further divided into two categories:

Single stage Reciprocatory Engines

Compound or multi stage Reciprocatory Engines

Single Stage Reciprocatory Engine:

A reciprocating engine, also often known as a piston engine, is an engine that utilizes one or more pistons in order to convert pressure into a rotating motion.

In single stage all the cylinders must produce same pressure.

Single Stage Reciprocatory Engine:

Working:

Each piston is located inside a cylinder, into which a fuel and air mixture is introduced, and then ignited.

The now hot gases expand, pushing the piston away. The linear movement of the piston is converted to a circular movement via a connecting rod and a crankshaft.

The more cylinders a piston engine has, the more power it is capable of producing.

Compound Engine:

A compound engine unit is a type of steam engine where steam is expanded in two or more phases.

Steam is first expanded in a high-pressure (HP) cylinder, then having given up heat and losing pressure, it exhausts directly into one or more larger volume low-pressure (LP) cylinders.

An animation of a double-acting inverted triple-expansion marine engine

inlet

exhaust

Stage one Stage two

Stage three

High pressure stage

Low pressure stage

Compound Engine With Two Pistons

Working

The complete expansion of the steam occurs across multiple cylinders and, as less expansion now occurs in each cylinder, less heat is lost by the steam in each. This reduces the magnitude of cylinder heating and cooling, increasing the efficiency of the engine.

Working of reciprocatory engine

Turbine or Rotary Engines:

A turbine is a rotary engine that extracts energy from a fluid flow.

Moving fluid acts on the blades to spin them and impart energy to the rotor. Early turbine examples are windmills and water wheels.

A turbine operating in reverse is called a compressor or Turbo pump.

Steam Turbine:

Turbine Blades

Stationary Engines

A stationary engine is an engine that does not move. Usually, a stationary engine is used not to propel a vehicle but to drive a piece of immobile equipment such as a pump or power tools.

Stationary engines come in a wide variety of sizes and use a wide variety of technologies.

Examples

Small stationary engines were frequently used on a farm to drive various kinds of power tools and equipment such as circular saws, pumps, and hay elevators.

Power stations of all sizes.

Beam engines used in mills and factories before the widespread use of electric power.

Dry Power Station

Power Station

Parts Of A Steam Engine

• Crank Shaft• Eccentric• Eccentric Rod• Valve Rod• Fly Wheel• Governor• Cross Head• Connecting

Rod

• Frame• Cylinder• Steam Chest• D-Sliding Valve• Inlet & Exit Port• Piston• Piston Rod

Following are the main parts of the Steam Engine:

Frame

Frame

Supports the stationary and moving parts.

Hold the parts in proper position.

Rests on engine foundation.

Cylinder

Cylinder

Cylinder

Cylindrical hollow vessel in which the piston moves to & fro under the pressure of steam.

Steam Chest

Steam Chest

Acts as reservoir of steam for cylinder.

Contains valve system.

D-Sliding Valve

D-Sliding Valve

Moves with simple harmonic motion with in steam chest.

Connected to eccentric.

Provides inlet and exhaust of steam at proper timing.

Piston

Piston

Cylindrical disc, which moves to & fro inside the cylinder under the pressure of steam.

Converts the heat energy of steam ino mechanical work.

Piston Rod

Piston Rod

Circular rod connects the piston with the cross head.

Cross Head

Cross Head

Cross Head

Link Between Piston rod & connecting rod.

Provides guidance to the motion of piston rod.

Connecting Rod

Connecting Rod

One end connected to the connecting rod & other to the crank shaft.

Converts the reciprocating motion of the piston into the rotary motion of the crank shaft.

Eccentric

Eccentric

Eccentric

Fitted to crank shaft.

Provides the reciprocating motion to the slide valve.

Fly Wheel

Fly Wheel

Heavy Cast Iron Wheel mounted on crank shaft.

Prevents the fluctuations of the engine by storing mechanical energy.

Governor

Governor

Keeps the speed of the engine uniform at different load conditions by controlling the amount of steam supplied to the engine.

Governor

The Working of Steam Engine is based on the Rankine Cycle.

Working Of Steam Engine

RANKINE CYCLE

•The Rankine cycle is a thermodynamic cycle which converts heat into work. •Water is used as the working fluid in this cycle.•80% of all electric power used throughout the world is produced using this cycle.•It is named after William Rankine, a Scottish polymath.•It is referred to as a practical Carnot cycle.•A Rankine cycle describes a model of steam operated heat engine.

RANKINE CYCLE(CONTINUED)

The main difference is that heat addition and rejection are isobaric in the Rankine cycle and isothermal in the theoretical Carnot cycle.

A pump is used to pressurize liquid instead of gas. This requires a very small fraction of the energy compared to compressing a gas in a compressor (as in the Carnot cycle).

The efficiency of a Rankine cycle is usually limited by the working fluid.

One of the principal advantages the Rankine cycle holds over others is that during the compression stage relatively little work is required to drive the pump.

Processes of the Rankine cycle

PROCESSES(CONTINUED)

Process 4-1: The working fluid is pumped from low to high pressure, as the fluid is a liquid at this stage the pump requires little input energy.

Process 1-2: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapor.

Process 2-3: The dry saturated vapor expands through a steam engine, generating power. This decreases the temperature and pressure of the vapor, and some condensation may occur.

Process 3-4: The wet vapor then enters a condenser where it is condensed at a constant pressure to become a saturated liquid.

THERMAL EFFICIENCY OF RANKINE CYCLE

Heat Supplied during Process,1-2=QS=h2-h1

Heat Rejected during Process,3-4=QR=h4-h3

Work Input=h4-h1

Useful Work Output=h2-h3

Net Work= (h2-h3) + (h4-h1) Thermal Efficiency= η= Net Work/ QS

= (h2-h3) + (h4-h1)

(h2-h1)

WORKING OF STEAM ENGINE

WORKING(CONTINUED) Steam is generated, under pressure, in a boiler. From the

boiler the steam enters the cylinder at the front of the piston, through the port A. This is called the inlet or steam port.

The pressure of the steam pushes the piston, along the cylinder, in the direction of arrow C.

The steam at the back of the piston, (from the previous stroke), is pushed out through port B. This is called the exhaust port.

As the piston, moves along the cylinder so does the piston rod, which is fixed to the crosshead. The crosshead keeps the piston, and piston rod, moving horizontally.

Also fastened to to the crosshead is one end of the connecting rod. The other end is fastened to the crank.

As the piston and piston rod move backwards and forwards, the connecting rod causes the crank, crankshaft and flywheel to rotate in the direction shown.

VALVE MECHANISM

The admission of steam into the cylinder has to be controlled so that live steam (steam from the boiler) pushes the piston backwards and forwards to obtain a continuous rotary motion to the crank. The mechanism that controls the steam admission is called the valve gear or valve mechanism.

ECCENTRIC

The valve is moved backwards and forwards over the cylinder ports by the action of the eccentric. The eccentric consists of a circular disc, which is fastened to the crankshaft and rotates with it. The centre of crankshaft is made offset (eccentric) to the centre of the disc. Thus, when the crankshaft rotates, a point on the centre of the eccentric disc forms a circle around the crankshaft centre. The diameter of this circle will be twice the offset.

If the slide valve is connected to the eccentric by means of an eccentric rod, then as the crankshaft rotates, the valve will move backwards and forwards by a distance which is twice the offset of the centers. This distance is known as the throw of the eccentric.

ECCENTRIC(CONTINUED)

SLIDE VALVE OPERATION

VALVE OPERATION (CONTINUED)

VALVE OPERATION (CONTINUED)

VALVE OPERATION (CONTINUED)

It is used for driving machinery in factories and mills. Steam-powered transport on both sea and land. Very low power engines are used to power models and speciality application such as

the steam clock. power supplied to the electric grid is predominantly generated

using steam turbine plant. Transport applications

engines have been used to power a wide array of transport appliances:

* Marine: Steamboat, Steamship* Rail: Steam locomotive, Fireless locomotive* Agriculture: Traction engine, Steam tractor* Road: Steam wagon, Steam bus, Steam tricycle, Steam car* Construction: Steam roller, Steam shovel* Military: Steam tank (tracked), Steam tank (wheeled)* Space: Steam rocket

It convert heat from almost any source to mechanical work. Steam engines are no adversely effect by atmospheric pressure . For road vehicles steam propulsion has the advantage of having high torque

from stationary, removing the need for a clutch and transmission. Also a steam train with similar speed and capacity is 50 percent lighter than an

electric or diesel train. Thus, especially rack railways, significantly reducing wear and tear on the track.

improvements like roller bearings, heat insulation, light-oil firing, improved inner streamlining, one-man-driving and so on. These resulted in 60 percent lower fuel consumption per passenger and massively reduced costs for maintenance and handling.

They are noisy and require a lot of fuel. Low efficiency, which means you have to put

more energy in (as compared to other modes)

than you get out. The disadvantages of using a steam train is the efficiency, it is low. Typical steam

engine efficiency cannot reach more than 30%. The other problem is obviously it needs plenty of fossil fuel in order to create

steam for the engine. Fossil fuel will be gone soon if people do not look for alternative.

Its parts were large and difficult to keep in proper alignment. Great power loss through friction because parts are being cast and not properly

machined.