Electric Resistance Strain Gauges: Working, Position and Location of Installation

Working
Electrical strain gauge is a device which produces an electric signal whenever there is a strain on the object to which they are attached. In strain gauges electrical signal is produce due to the change in the resistance of the strain gauge. Strain gauges consist of single electrical wire which passes through strain gauge body as shown below. When strain is produce in any body the length of this wire of strain gauge is changed and a result the electric resistance of the strain gauge changes. This change in electric resistance is first amplified and then calculated to find the amount of strain produce in the object.

 

What is Single Shaft Turbine and Double Shaft Turbine

Single Shaft Turbines

Single shaft turbines are those which have single shaft running through the whole turbine means through compressor, turbine and generator of gas turbine. The working of such a turbine starts with the introduction of air in compressor section of turbine which has blades to compress the air. That compressed air them moves to the combustion chamber of the turbine where it get mixed with the fuel and burn to produce high temperature and high pressure gasses. Those high pressure and high temperature gasses then moves to turbine/power generation section where power is extracted from the hot gasses by the blades of the turbine. Blades use the hot gasses power to rotate the shaft of the generator or pump to produce the mechanical or electrical power output. All these rotating components like compressor, turbine and generator are made on single shaft.

Double Shaft Turbine

These turbines have two shafts in their system where one shaft moves between compressor and compressor turbine and second shaft moves between power turbine and generator of gas turbine. Working procedure of these shafts is little different from single shaft turbines and its starts with the introduction of air in compressor section of turbine which has blades to compress the air. That compressed air them moves to the combustion chamber of the turbine where it get mixed with the fuel and burn to produce high temperature and high pressure gasses. Those high pressure and high temperature gasses then moves to compression turbine section and from there they move to the turbine/power generation section which absorbs power from gasses. Power is use to rotate the shaft of the power turbine and that shat is attached with the generator which produce electrical or mechanical power output.

What is function of Regeneration and Reheating in gas turbines

Reheating

Reheating in gas turbine is done in order to increase the efficiency of the turbine. For this gas turbine is divided into number of stages and they are classified as high pressure turbine and low pressure turbine. At each stage power is produce based on the temperature and pressure of the gas. Procedure starts with the introduction of gasses at high temperature and high pressure into the turbine section having number of blades. Blades absorb power form gasses and after that gasses are eliminated from that section of gas turbine. When that gas at low temperature and pressure is received from the high pressure stage then it is reheated before it enters the low pressure turbine section. Is reheating is necessary because gas after existing the high pressure stage will be at such a low pressure that it cannot be used in second stage of gas turbine.

Regeneration

According to the working of the gas turbine the gasses for combustion are first get compresses in compressor and they move forwards for combustion. Temperature of gasses when they leave the compressor is lesser then the temperature of the gasses leaving the turbine after combustion and power production. Introduction of gasses in combustion chamber at high temperature will increase the efficiency of the turbine. To increase the temperature of gasses before they enter the combustion chamber, the gasses which are coming out of compressor are heat with the help of gasses which are coming out of the turbine outlet. For this heating purpose heat exchanger is used where hot gasses coming out of turbine flow in tubes and gasses coming out of compressor flow in shell of heat exchanger. During their flow in shell, gasses going into the combustion chamber gain heat through conduction and convection. 

What are Condensing Turbines and Back Pressure Turbines

Condensing Turbine

Condensing turbine get their name from their ability condenses steam in one of their outlet. Condensing turbine has two outlets from which one is used to utilize the medium pressure steam for heating process and other outlet do condensation process by utilize the low pressure steam. At the outlet (where medium pressure steam is utilize to get heating) on control value is present which is used to control the flow of steam over that outlet. By controlling the steam flow over that outlet the production of condensation process can be increased or decreased. The second outlet moves the steam to the condensation chamber where water flow over this steam. When water flow over high temperature steam, it absorb heat from the steam and get condense and then that condense water is moved toward boiler of the condensing turbine. 

The condensing turbine process starts with the entry of the high pressure and high temperature steam into the turbine section where it is utilize by the blades of the turbine to produce power. After the production of power the portion of steam which have moderate pressure is move out through first outlet to be utilized for heating and the portion of the steam whose pressure is to low to be used for any type of power production is move out through second outlet towards the condenser. In condenser water remove heat from steam and condense water is again move towards the boiler of the turbine.

Back Pressure Turbine

The back pressure steam turbine is one in which steam at high pressure and high temperature enters the turbine and that steam is used to rotate the turbine blades for power production. Back pressure steam turbine is also called the condensing steam turbine and reason for that is this turbine does not have condenser at its outlet and it has only one outlet. 

Working of back pressure steam turbine start with the entry of the high pressure steam into turbine power generation section where blades are present. Blades absorb power from steam and use it to product rotation in shaft of turbine. After providing power for shaft rotation, steam at low pressure and temperature exit the turbine from the outlet into the atmosphere and this is also the main difference between condensing and back pressure turbines. In back pressure turbine the outlet pressure of steam is so low that it cannot be used for any work. This outlet pressure depends on the load on turbine. 

Function of Turbocharger and Intercooler in Internal Combustion Power unit Performance

Turbocharger

Turbocharger is a name given to the device which is similar in working and components to the air compressor and it is being used in internal combustion power units to increase the efficiency of the internal combustion power unit. Turbocharger consists of a compressor housing which hold the compressor wheel inside it, turbine housing which hold turbine wheel inside it and one shaft which have both compressor wheel and turbine wheel mounted on it.

Working of turbocharger starts from the rotation of turbine which takes power form the hot gasses flowing out of the engine. Turbine uses this power to rotate the compressor wheel of the turbocharger because both of the wheels are mounted in the same wheel. Compressor compresses the outside air and forces it into the intake of the compressor. This increase in the inflow of air into the engine combustion chamber will increase the efficiency of the engine because the air fuel mixture will have more oxygen in it than the normal operation. Extra oxygen means effective combustion of fuel and this means more power with the same amount of the fuel used.

Intercooler

Explanation of the turbocharger has been explained in the above section and its main function is to provide the engine with the some air at high pressure. According to the principles of the thermodynamics at constant volume if pressure of the air is increase then its temperature will also increase. This increase in temperature of the air will result in decrease of engine efficiency so the air must be cooled before it enters the engine. For this purpose intercooler is used which is just a simple heat exchanger whose main function is to decrease the temperature of the air passing through its tubes. For cooling purpose fluid main be present in the pipes of the intercooler or low temperature air may flow over the fins of the heat exchanger, it’s all depends on the types of the heat exchanger used for this work. 

Second Law of thermodynamics With Heat Engine Example

Clausius Statement of Second Law of thermodynamics

According to the second law of thermodynamics it is impossible to have a thermodynamics system in which only the transfer of heat energy from cooler to hotter body is done.

Kelvin Planck Statement of Second Law of thermodynamics

According to the second law of thermodynamics it is not possible for any machine which work in close thermodynamic cycle and convert the energy obtain from the single heat source and convert it into work done on to its surrounding. 

Heat Engine

Heat engine is an energy conversion device which is design to convert the heat energy into mechanical energy. Heat engine convert the heat energy into mechanical energy by bringing the heat energy from high potential reservoir to low energy reservoir. According to this statement of second law that heat cannot flow from colder region to hotter region with the aid to external work, helps to determine the direction of flow of energy in heat engine. According to the other statement of second law that there is no device which only convert heat into energy, helps to determine the efficiency of the heat engine. 

Five Dangers Associated With The Air Compressors

Following are the five dangers associated with the air compressors

• Rupture
• Oil Leaks
• Foreign Particles
• Overheating
• Part failure

Rupture

One of the biggest dangers associated with the air compressors is the rupture of the air compressor under high pressure. Air compressors are made of heavy metals sheets and when air compressors will blast then it will break into small pieces of metal. Each one they will be able to kill any person which came under its range. 

Oil Leak

Lubrication is used to run the different parts of compressor smoothly but when proper care is not taken then this oil can leak into the compressor. If the compressor is being used in any workshop where fire or torch is being used then this oil leakage can very dangerous as it can cause explosion in the case both came in contact.

Foreign Particles

Any kind of unwanted particles which can go inside the compressor are very dangerous for the compressors and people working near the compressors. Foreign particles can cause explosion if they are flame able and came in contact with fire or they can block the outlet of compressor thus causing explosion due to high pressure.

Overheating

Filling the compressor with any gas under high pressure cause increase in temperature of the compressor and gas it is known that metal and gasses expand on heating. So of temperature of compressor increase more than it can handle the it can compressor failure which can cause fire at work place.

Part failure

In the case when proper maintenance is not done then ay part of the compressor can fail under ay condition. Part failure can be extremely dangerous for the worker working nearby because air in air compressor is at such a high pressure that its thin stream can create a hole in human body or can damage any sensitive part like eyes or ears