Arrhenius Concept of Acids & Bases
In this Arrhenius acid & base theory is explained in detail. Watch this
video and learn this concept because it will help you to strengthen your
basic chemistry concepts.
https://www.youtube.com/watch?v=55ABAQQWIl4&t=30s
Numerical Methode
Notes for sessional 2.
These notes include all the relative topic.
These notes are hand written and if found any error please ignore it.
Numerical methode.pdf
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Tag :
Numerical Methode,
Turbojet engine
Turbo Jet Engine
Air Intake
Compressor
Combustion Chamber
Turbines
Merits
The turbojet is an air breathing jet engine, typically used in aircraft of a gas turbine with a propelling nozzle. The gas turbine has an air inlet, a combustion chamber and a turbine. The compressed air from the compressed is heated by the fuel in the combustion chamber and then allowed to expand through the turbine. The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high.
It works on the basis of Newton’s third law of motion which stated that “action and reaction are equal in magnitude but opposite in direction”. The high speed thrust produce will act as action and in reaction the airplane moves in the forward direction.
Types of turbo Engines
· Turbojet engine
· Turbofan engine
· Turbo propeller Engine
· Ramjet Engine
· Scramjet Engine
It works on the Brayton Cycle
Air Intake
The air is entered from the intake tube. It is subsonic air having low pressure and temperature which is then entered into the compressor.
Compressor
Compressor squeezes fresh air into engine. Initially the compressor ratio is 1:8 and nowadays the compressor can compress the air by 44:1. In the compressor the temperature and pressure of the air is increases. After leaving the compressor air enters into the combustion chamber.
Combustion Chamber
The hot air from the compressor enters into the combustion chamber where it burns with the fuel and pass through the turbine continuously. The air-fuel mixture exhausted and produces high thrust which in reaction moves the airplane in the forward direction.
Turbines
Exhaust gases passes through the turbine rotating it like a wind mill. These are impulse turbine rotated because if the impact of the hot gas steam. Later stages are convergent ducts that accelerate the gas.
Afterburners
Afterburner is used in supersonic aircraft. It is a combustion chamber which is added to reheat the turbine exhaust gases. The fuel combustion is high typically four times more than that of the main engine.
Merit and Demerits of turbojet engines are given below.
Merits
· Compact them most reciprocating engine
· Very high to power ratio
· Low operating pressure
· High operating speed
· Low lubricating oil cost
· Less parts
Demerits
· High manufacturing cost.
· Longer starter than reciprocating engine
· Less response to changes in power demand compared to reciprocating engines.
Steam Engine
Steam Engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. Steam engine is external combustion engine in which the working fluid is separated from the combustion chambers. The ideal thermodynamics cycle used to analyze this process is called the Rankine Cycle. In this cycle water is heated and changes into steam in a boiler operating at a high pressure. When expanded using pistons or turbines mechanical work is done. The reduced pressure steam is then exhausted to the atmosphere, or condensed and pumped back into the boiler. The main parts of steam engine are Boiler, Motor Unit, Cold Sink, Water pump.
Rankine Cycle:
The Rankine cycle is the fundamental operating cycle of all power plants. The Rankine cycle operates in the following steps.
· 1-2-3 Isobaric Heat Addition.
High pressure liquid enters the boiler from the feed pump and is heated to the saturation temperature. Further addition of energy causes evaporation of the liquid until it is fully converted to saturated steam.
· 3-4 Isentropic Expansion:
The vapor is expanded in the turbine, thus producing work which may be converted to electricity. In practice the expansion is limited by the temperature of the cooling medium and by the erosion of the turbine blades.
· 4-5 Isobaric Heat Rejection:
The vapor liquid mixture leaving the turbine is condensed at low pressure, usually in a surface condenser using cooling water. In well designed and maintained condenser, the pressure of the vapour is well below atmospheric pressure, approaching the saturation pressure of the operating fluid at the cooling water temperature.
· 5-1 Isentropic Compression:
The pressure of the condensate is raised in the feed pump. Because of the low specific volume of liquid, the pump work is relatively small and often neglected in thermodynamics calculations.
Types of Steam Engine
According to the number of working stroke
- · Single acting steam engine
- · Double acting steam engine
According to the number of cylinder
- · Simple steam engine
- · Compound steam engine.
According to the types of exhaust
- · Conducing steam engine
- · Non-conducing steam engine.
According to the speed of crankshaft
- · Slow, medium and high speed engine.
According to the field of application
- · Stationary Engine.
- · Local motive engine.
- Marine Engine.
Limitation of Steam Engine
The major limitations of a steam engine or external combustion engine are given below.
· A steam engine is huge and heavy. Due to its big boiler and furnace a steam is huge, heavy and clumsy. Since the boiler of a steam engine is very heavy, therefore a steam engine cannot be used for running small vehicles like cars and buses.
· A steam engine is unsafe to use. A steam engine is not very safe to use because its boiler can burst to excessive steam pressure,
· A steam engine does not start at once. Before a steam engine can start, we have to build a coal fire to get steam. This process takes a long time and hence a steam engine cannot be started at a moment’s notice.
· A steam engine has low efficiency.
Evaporation and Boiling
Difference between Boiling and Evaporation:
Boiling | Evaporation |
Takes place only at a particular temperature at which the vapour pressure of the liquid becomes equal to the atmospheric pressure.
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Occurs spontaneously at all temperature. In all seasons whether it is winter or summer.
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Involves the formation of bubbles of the vapour throughout the bulk of the liquid.
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Takes place only at the surface of the liquid.
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Also we can saw evaporation is a process in which a substance changes its state from the liquid state to gaseous state.
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Evaporation is a process whereby the water is changing into vapour without boiling.
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It is a quick process.
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It is a slow process.
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Bubbles are formed.
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No bubbles are formed.
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Occurs at a specific temperature.
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Occurs at all temperature.
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Source of energy needed.
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Energy supplied by surrounding.
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Thermodynamics
CHAPTER: Rotodynamics Machinery
BOOK: Applied Thermodynamics by TD Eastop and A McConkey, 5th Edition.
For the complete detail of this chapter download the given slides. The slides consists of complete description, diagrams and derivations.
Rotodynamic Machinery in which a fluid flow freely through impeller or rotor.
BOOK: Applied Thermodynamics by TD Eastop and A McConkey, 5th Edition.
For the complete detail of this chapter download the given slides. The slides consists of complete description, diagrams and derivations.
Rotodynamic Machinery in which a fluid flow freely through impeller or rotor.
- the transfer of energy between fluid and rotor is continuous and
- the change of Angular Momentum of the fluid causes, or is the result of Torque on rotor.
This chapter covers the Basic Theory of Turbines and Compressor used in Steam Plant and Gas Turbine Plant.
Impulse Steam Turbine
- Impulse Turbine
- Takes a high pressure, high-enthalpy fluid.
- Expand it in a Fixed Nozzle.
- Steam coming out through a fixed nozzle at a very high velocity strikes the blades fixed on the periphery of a Rotor.
- Blade change the direction of steam without changing its pressure.
- Force due to change of momentum(by changing the direction) causes the rotation of the turbine shaft.
Fluid flowing through the wheel at a fixed mean radius, then the change of Linear Momentum tangential to the wheel gives a Tangential Force that causes the wheel to rotate.
Assume initially that the fluid is able to enter or leave the wheel passage in the Tangential Direction with an Absolute Velocity at inlet Cai and an Absolute Exit, Cae.
For a fixed blade Cb=0.
For more detail download the given slides the slides consist of complete description and detail of impulse steam turbine.
Petrol's and Diesel Engines
Petrol’s and Diesel Engines:
What is Engine?
An engine is a machine that is
designed to convert one form of energy into mechanical form.
The main
parts of Engines:
Cam Shaft takes up and down motion of piston and converts it
into rotating motion. Valves there
are two types of value intake and exhaust as from the name intake value are
used to transfer fuel inside the cylinders and exhaust value is used to exhaust
the burning fuel outside to the environment. Engine head is the head of engine on which the spark plug in
mounted. Spark plug is used to
provide the spark in each cycle to burn the petrol (in petrol engine). Injector
it sprays the fuel (used in diesel engine). Cylinders combustion is take place in cylinder. Piston oil control ring. Connecting Rod connects the piston and
crankshaft. Crankshaft is used when
the multiple pistons are used in an engine in order to convert the each piston
up and down movement into rotation. Flywheel
is attached with the gear train and delivers the power. Gear Train is used to increase or decrease the speed.
Important Terminologies we learn.
Internal Combustion Engine? is an engine in which the combustion of a fuel
occurs in a combustion chamber. External
Combustion Engine? Is an engine in which the combustion takes place in an
external source it is also known as heat engine. Top dead Center the furthest point of a piston's travel, at
which it changes from an upward to a downward stroke. Bottom dead
center the furthest point of a piston's near to crankshaft, at which
it changes from downward to upward stroke. Stroke a stroke refers to the full travel of along the cylinder. Intake Stroke this stroke of the piston
begins at top dead center. The piston descends from the top of the cylinder to
the bottom of the cylinder. A mixture of fuel and air is forced by atmosphere
pressure into the cylinder through the intake port. Compression Stroke when both the intake and exhaust valves are
closed, the piston returns to the top of the cylinder compressing the air or
air-fuel mixture. Power Stroke while
the piston is close to top death center, the compressed air-fuel mixture in a
gasoline engine is ignited, by a spark plug. The resulting pressure from the
combustion of the compressed fuel-air mixture forces the piston back down
toward the bottom dead center. Exhaust during
the exhaust stroke piston once again returns to top dead center while the
exhaust valve is open.
Four
functions known as intake, compression,
combustion and exhaust these
four functions are required to produce a final power stroke. Without these
function no internal combustion engine in the world can work whether it is a
two strokes, four strokes or Wankel engine.
2 Stroke Engines is a type of internal combustion engine which
completes a power cycle in only one crankshaft revolution and with two stroke,
or up and down movements, in short it complete the above four functions intake,
compression, combustion and exhaust in two stroke. Intake and compression in
one stroke and combustion and exhaust in second stroke.
4 Stroke Engine is a type of internal combustion engine in which the
piston completes four separate strokes which comprise a single thermodynamics
cycle.
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Two Stroke Engines
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Four Stroke Engines
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It completes power
cycle within two strokes.
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It completes power
cycle within four strokes.
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In two strokes the end of the
combustion stroke and beginning of the compression stroke take place
simultaneously.
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In four strokes the end of the
combustion stroke occurs separately and beginning of the compression stroke
occurs separately.
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Two stroke engines have high power to
weight ratio.
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Four stroke engines have low power to
weight ratio.
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Two stroke engines have a greatly
reduced number of moving parts and so can be more compact.
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It has more parts.
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Don’t have valve. It has
ports.
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Don’t have ports. It has
valve.
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Cheaper to construct.
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Expensive to construct.
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It is not fuel
efficient.
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It is fuel efficient as
compared to two stroke.
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Low life.
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High life.
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Which one is better?
At
the end of the day the winner is probably going to be the one that has had more
money and technology spent on it. In these days of quick and cheap
international production schedules you can’t take it for granted that the 4
stroke will be better. So for a particular application, we should try to line
up the options and make a decision based on what’s available, not based on
lists that miss the key points of difference.
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Petrol Engines
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Diesel Engines
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It works on Otto Cycle.
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It works on diesel
cycle.
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§ In
petrol engine the air and petrol are mixed in carburetor and it enters into
the cylinder.
§
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In diesel engine the fuel is first fed
into the cylinder by a fuel injector and then gets mixed with air inside the
cylinder.
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In petrol engine first the compression
of air and petrol is done and then it is ignited by an electric spark.
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In diesel engine only the charge of
air is compressed and ignition is done by the heat of compressed air.
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Its compression is low.
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Its compression ratio
is high.
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In petrol engine we use
spark plug for ignition.
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In diesel engine we use
injector for ignition.
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Power developed is low due to low
compression ratio.
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Power developed is high due to high
compression ratio.
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The fuel that burns has
high volatility.
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The fuel that burns has
low volatility.
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It used in light weight vehicles like
in cars, motorcycles, scooters etc.
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It used in heavy weight vehicles like
in cars, motorcycles, scooters etc.
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Thermodynamics
In these slides we will cover the following topic in detail so for the complete description download the given slides.
A device that exchanges energy with the fluid, using continuously flowing fluid and rotating blades.
e.g Aircraft Engine, Wind Turbine.
- If the device extract energy from fluid generally called as turbine.
- If the device deliver energy to fluid generally called as pump.
turbo machinery is the generic name of all these machines.
Nozzles?
A nozzle is a duct of smoothly varying cross section area in which a steadily flowing fluid can be made to accelerate by a pressure drop along the duct. Nozzles are used in steam turbines, in rockets,in injector and ejector etc.
Diffuser ?
When a fluid is decelerated in a duct causing a rise in pressure along the steam. e.g centrifugal pump etc.
Description of following topic is available in slides so for the detailed learning download the following slides.
- Nozzles Shape
- Critical Pressure Ratio
- Critical Temperature Ratio
- Critical Velocity
- Maximum Mass Flow
- Nozzle off the designed pressure ratio
- CD Nozzles
- Nozzle Efficency
- Length of Nozzle
- The Steam Nozzle
- Stagnation Conditions
Ch-2 Thermo-II Sp-18-Week5.pdf
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Mechanics of Material 2
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MOM 2,
Thernodynamics 2
In this lecture we will discuss about.Ch-1 Thermo-II Week-3.pdf
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- What is a turbomachine?
- Schematic of Jet Engine.
- Nozzels
As you know nozzle is a duct of smoothly varying cross section area in which a steady flowing fluid can be made to accelerate by a pressure drop along the duct. e.g nozzles are used in steam and gas turbines, in jet engines, in rocket motors etc.
In this lecture we will discuss the nozzle briefly.- Diffuser
When a fluid is decelerated in a duct, causing a rise in pressure along the stream. Its major applications are centrifugal pumps and ramjet.
- We will also discuss diffuser briefly.
- We have a long discussion on Nozzle Shape.
- Convergent Divergent Nozzle.
- Critical Pressure Drop
- Critical Temperature Ratio
- Critical Velocity
- Maximum Mass Flow
- Nozzle Off the design pressure ratio
- Convergent Nozzle
- Convergent Divergent Nozzle
- Nozzle Efficency
- Length of Nozzle
- The Steam Nozzle
All of the above topics are discussed in detail in the above given slides.
Thermodynamics 2
thermo-lab-1.docx
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Thermodynamics
Branch of science that studies changes in energy.
Temperature, Pressure, Volumeare driving forces for energy.
Types of Heat
(1) Latent Heat:
Related to phase change i.e. melting of ice. Boilers, Evaporator.
(2) Sensible Heat:
Heat can be sensed (No phase change) e.g. Heaters. Air conditioners.
Laws of Thermodynamics
First Law of thermodynamics:
Energy can neither be created now destroyed but it can be changed from one form to another.
Also called law of conservation of energy.
ein-eout=constant
ein=eout
ΔU=Q+W
Q= Heat exchanged b/w system.
W=Work done.
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Second Law of thermodynamics:
Entropy of a system also increases never decreases.
Entropy:
Measure of disorder of energy of a system.
Zeroth Law of thermodynamics:
Kelvin Statement
No device can be worked with single reservoir. .e.g. car-engine.
Clauses Statement
Heat cannot be transferred from low to higher reservoir. E.g. refrigerator
Second Law of thermodynamics:
For a pure crystalline structure entropy is zero at absolute zero.
Microscopic Properties:
Study of each atom or molecule separately.
Macroscopic properties:
Study of each atom or molecule as whole average.
System:
Anything under consideration is system.
Surrounding:
Everything except system is surrounding.
Boundary:
The separation b/w system and surrounding is boundary.
Closed System:
A fixed amount of mass is chosen for study.
Open System:
Hitec Mechanical Engineering
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