Lapping vs. Polishing

What is Lapping?

The term "lapping" is used to describe a number of various surface finishing operations where loose abrasive powders are used as the grinding agent at normally low speeds. It is a process reserved for products that demand very tight tolerances of flatness, parallelism, thickness or finish.

Fundamental Lapping Theory

 The basic theory of lapping starts with the components being placed within the confines of conditioning rings directly onto the surface of a rotating lap plate that is coated with a precision film layer of slurry. The components should never come into direct contact with the lap plate surface. Through powered lap plate rotation, the loose and rolling abrasive particles within the slurry layer transfer cutting energy with their sharp cutting edges by penetrating the contact surface of the components removing microscopic chips of material. Concurrently the abrasive is acting on the lap plate via the contact surface of both the components and conditioning rings causing wear that when controlled by adjustable radial ring position will effect spherical curvature changes to maintain a flat lap plate condition.

 

How Does Lapping Work?

One or more parts are machined at the same time in a batch process. The abrasive is usually mixed with a liquid vehicle, either oil or water based. The pieces being lapped are captured in retaining rings. Workholders also called "carriers" may be used to keep the parts separated to prevent damage to their edges. The parts are dragged across the lap plate surface on to which the abrasive is being fed.

Lapping is an averaging process where the greatest material removal occurs where the high points of the surface of the part contact the flat lap plate. The object is to produce parts with a uniformly smooth and usually flat surface.A surface that has been lapped exhibits a dull, non-reflective and multi-directional appearance. This condition is referred to as “matte” finish. There may be slight reflectivity on materials lapped with very small micron size aluminum oxide abrasive. This is especially true if the material is relatively hard and the surface roughness measurement is perhaps 5 (.127 micron) micro-inch and below.

Very light “micro-scratches” may be viewed on lapped surfaces. Abrasive of larger micron size and harder compound will generate more micro-scratches in addition to deeper scratches. Most micro-scratches produced with small micron aluminum oxide abrasive will be less than .000001” (.025 micron) deep and can’t usually be measured with a profilometer. Micro-scratches should not be confused with deeper scratches produced by particles of contamination or other causes.

What Takes Place During The Lapping Process?

• The Surface Finish is modified and is usually improved in surface and sub-surface qualitative values (smoother)
• Geometry (flatness) of the processed surface becomes flat or spherical in contour as a result of Lapping
• Some amount of material is removed from the Lapped surface of the work

The most obvious difference between lapping and the other major machining operations is lapping doesn’t use a single or multiple point cutting tool. Lapping cuts chips by way of a loose abrasive process. One of several different types of precision micro-graded abrasive compound powder is mixed at a specific ratio with cutting fluid and dispensed onto a rotating lap plate.

 The compound material, percentage mixture volume, abrasive particle micron size and applied pressure determine the resulting stock removal rate and surface roughness. The mixture of abrasive and cutting fluid is called “slurry” or “lapping slurry”.The difference in the types of abrasives, as well as the size and cost will vary considerably so it is important to know which abrasive best suits your needs. The material to be lapped determines what type of abrasive is used, and the amount of material to be removed together with the specified surface finish governs the abrasive grain size. 

For example, extremely hard materials such as sapphire, carbides, and some ceramics require diamond or boron carbide. The medium hard materials, which includes harder metals and some aluminas, can be lapped with silicon carbide. Aluminum oxide is widely used in the glass and silicon industry because of its softer cut and lower cost. Keeping in mind that the abrasive charges the surfaces of your lap plates, it is almost always preferable to have your plates softer than the material being lapped, while the abrasive should be as hard as, or harder than the work pieces.

Lapping Process Basics

• A very passive form of grinding (low pressure, low speed, low removal rate)
• Requires the use of micron-sized Abrasive Particles (not mesh or grit sized abrasive)
• Some amount of movement is required on the part of the tool (lap plate), the workpiece or both
• In most cases, lapping is utilized on flat surfaces, not spherical shapes or contours
• The lap plate is usually softer that the work- piece
• The Conditioning/Retaining Ring is same hardness or harder than the Lap Plate
• Lapping is almost always
• a “wet process”
• The work-piece never contacts the lap plate
• Only a small amount of material (as little as 5 microns or as much as 500 microns) is removed from each side of the work
• Lapping is always a batch loading process 

Factors to consider during the Lapping Process 

• Type of material being processed

In the years Lapmaster Wolters has been serving industry, customers have asked us to process sample components involving just about every common engineering material known to man and some not so common materials. As our sciences and technologies advance, demands for more precise size tolerances, surface flatness and surface roughness become greater. Many of the technological advances are being derived from the use of new material compounds as well as more exotic natural materials. Lapping and polishing is a machining process that is very gentle and produces low stress levels in delicate and brittle materials. Yet these operations have the capability to process the hardest materials on the face of the earth. A small cross section example of the materials processed on Lapmaster machines is shown below.

• Speed of plate 

Depending on the aspect ratio of the component, a lap plate speed must be selected that will not cause the component surface to oscillate, vibrate or depart the lap plate surface in any way. The surface requiring lapping must always register firmly and positively to the lapping or polishing plate surface.

• Pressure on work-piece-

The amount of pressure applied to the components being lapped can effect resulting surface roughness by altering the slurry film thickness. The higher the pressure (3 P.S.I. maximum for conventional lapping) the thinner the film thickness and the greater the chance of “wiping” the components against the lap plate. When lapping to achieve fine surface roughness it is recommended to not exceed 2 P.S.I. for most common applications.

• Plate material
• Size and type of abrasive-

Abrasive compounds (fused and non-fused Al2O3; black and green SiC, B4C, mono-crystalline diamond and polycrystalline diamond) have crystal structure that determine the hardness, shape, number of cutting edges and friability of the material. Friability is the rating of the crystal bond strength that determines the force required for cleaving cutting edges from the crystal. Under the same conditions of PSI load, harder compounds (ex. SiC) penetrate the component material to a greater depth before edge cleavage than softer compounds (ex. Al2O3) thus generating greater surface texture. Flat hexagonal crystal shape has fewer sharp cutting edges and penetrates or gently shaves the component material less deeply than a blocky tetrahedron shape that gouges chips with a large number of protruding cutting edges. More friable abrasives (ex. Al2O3) require less force to break off cutting edges than less friable abrasives (ex. SiC). Another important factor regarding friability is the size of the crystal reduces as cutting edges break off. As the crystal becomes smaller it cuts smaller chips and generates lower surface roughness measurements.

•  Vehicle used & Abrasive to Vehicle Slurry Ratio

The correct ratio must be used when lapping to obtain consistent, repeatable surface roughness. More importantly, the ratio is a factor of film strength and thickness. If the film thickness is too low the component material will tend to wipe closer to the lap plate and greater cutting energy will be transferred through the abrasive particles to the component material causing greater penetration, more severe scratching and higher surface roughness measurements.

• Flatness of plate

An important concept to understand is that the lap plate flatness measured across its diameter doesn’t need to be the same measurement as the component finished flatness specification. This is because the component conforms to a small span of the lap plate geometric spherical radius. The span of the component is its diameter, if circular, or the greatest length across the components lapped surface. In other words, a one inch diameter component will be lapped much flatter than a four inch diameter component when utilizing the same lap plate. The exact flatness required on the lap plate can be mathematically calculated using the trigonometry formula for the determination of cord length.

• Feed system
• Method of charging and conditioning the plate
• Plate temperature

What is Polishing?

• A process to generate a reflective surface
• Normally, the polish is generated by using a fine-micron or sub-micron abrasive particle in combination with a liquid. Polishing is a “wet” process.
• Often the polishing process utilizes a pad to contain the abrasive, so polishing may not be a “loose abrasive process.” The pad is softer than the part.
• Very little material is  removed during the polishing process, normally measured in microns
• The surface finish of the work-piece to be polished must be of a high quality prior to the polishing process taking place, so the pre-polishing process is often a “lapped” surface.

Polished Surface Functions

• Enables sealing of high pressure gases and liquids
• Cosmetic purposes
• Enables the use of optical flatness measurement instruments
• Reduces the amount of surface and sub-surface damage
• Provides better uniformity of surfaces requiring epitaxial processes or deposited materials
• Generates sharper edges on cutting tools

 

Types of Polishing

• Soft or hard pads using a conventional or special purpose abrasive slurry
• Soft or hard pads using a diamond abrasive slurry which may be water-base or oil-base
• Hard pads using a diamond compound and lubricant
• Diamond slurry polishing using a composite plate
• Diamond slurry polishing using a metal plate
• Fixed-abrasive films (captured abrasive) and lube

 

Lapping vs. Polishing

Lapping

• Dull, non-reflective surface (matte)
• Multi-directional lay pattern
• Component function (coating)

 

Polishing

• Reflective finish
• Typically 2nd step
• Component function (sealing)
• Cosmetic appeal
• Light-band inspection

How Does Polishing Work?

• Polishing often uses a polishing pad and water-base slurry to generate the reflective or clear surface
• An unblemished, scratch-free surface finish is critical on polished surfaces. To generate the required finishes, the polishing slurries are often caustic. As such, the polishing systems may feature stainless steel exposed components such as the hardware, rings and plates.
• Further to the above, some polishing applications also require thorough water rinsing during the end of the processing cycle, in order to remove the polishing media so it does not “stain” the surface. This is another reason why stainless steel is required.The polishing pads are usually grouped into either “soft” pad or “hard” pad categories. 

Lapping vs. Polishing Systems

• The lapping and polishing systems are quite similar in most aspects
• However, since polishing normally takes place using a pad and slurry, the surface tension is quite high compared to lapping
• In addition, a polished part features a much higher level of surface tension compared to a lapped part
• Based on the above items, polishing systems may feature a higher level of horsepower for the drives

GRINDING vs POLISHING

Grinding is an abrasive cutting action to meet dimensional accuracy and at same time smoother surface.Grinding removes saw marks and levels and cleans the specimen surface.Grinding uses fixed abrasives—the abrasive particles are bonded to the paper or platen—for fast stock removal.

The main purpose of the grinding step is to remove damage from cutting and to remove material approaching the area of interest.

Polishing is an super finishing operation which uses very fine abrasive just to improve roughness .Polishing removes the artifacts of grinding but very little stock.Polishing uses free abrasives on a cloth; that is, the abrasive particles are suspended in a lubricant and can roll or slide across the cloth and specimen.

The main purpose of polishing is to prepare specimen for microstructural analysis. It is the step which is required to completely eliminate previous damage.

basic definitions of fluid mechanics

Density (mass density): The mass per unit volume is defined as density. The unit used is kg/m³.The measurement is simple in the case of solids and liquids. In the case of gases and vaporous is rather involved. The symbol used is ρ. The characteristic equation for gases provides ameans to estimate the density from the measurement of pressure, temperature and volume.

Specific Volume: The volume occupied by unit mass is called the specific volume of the material. The symbol used is v, the unit being m³/kg. Specific volume is the reciprocal of density.In the case of solids and liquids, the change in density or specific volume with changes in pressure and temperature is rather small, whereas in the case of gases and vapours, density will change significantly due to changes in pressure and/or temperature.

Weight Density or Specific Weight: The force due to gravity on the mass in unit volume is defined as Weight Density or Specific Weight. The unit used is N/m³ .

Specific Gravity or Relative Density:  The ratio of the density of the fluid to the density of water—usually 1000 kg/m³ at a standard condition—is defined as Specific Gravity or Relative Density δ of fluids. This is a ratio and hence no dimension or unit is involved.

Compressible fluid -If the density of a fluid varies significantly due to moderate changes in pressure ortemperature, then the fluid is called compressible fluid.

Incompressible fluid-If the change in density of a fluid is small due to changes in temperature and or pressure, then the fluid is called incompressible fluid.

Buoyant force- If an object is immersed in or floated on the surface of fluid under static conditions a force acts on it due to the fluid pressure. This force is called buoyant force.


Archimedes principle -Archimedes principle can be stated as (i) a body immersed in a fluid is buoyed upby a force equal to the weight of the fluid displaced and (ii) a floating body displaces its own weight of the liquid in which it floats.

Reynolds number -Reynolds number is the ratio of inertia force to viscous force. As inertia force increases Reynolds number increases and the flow becomes turbulent.

Multiple Choice Questions (MCQ) with Answers on Engine Lubrication System

1-Lubricating oil

(A) Minimizes wear in moving parts

(B) Helps in keeping the parts cool

(C) Washes away and carries away dirt

(D) All of the above

(Ans: D)

2-Viscosity index (VI) is a measure for the change of viscosity with change in

(A) Temperature

(B) Pressure

(C) Volume

(D) All of the above

(Ans: A)

3-The following type of Lubrication system is used in two stroke engines

(A) Petroil (mist) system

(B) Wet sump system

(C) Dry sump system

(D) All of the above

(Ans: D)

4-In the following system, lubricating oil is carried in separate tanks from where it is fed to the engine

(A) Mist lubrication system

(B) Wet sump system

(C) Dry sump system

(D) Splash system

(Ans: C)

5-The following type of Lubrication system is used in Aircraft Engines

(A) Mist lubrication system

(B) Wet sump system

(C) Dry sump system

(D) Splash system

(Ans: C)

6-The following type(s) of Oil pump(s) is (are) used in Engine Lubrication system

(A) Gear type

(B) Rotor type

(C) Plunger type

(D) All of the above

(Ans: D)

7-The following is (are) oil pressure gauge(s)

(A) Pressure expansion type

(B) Electric type

(C) both (A) and (B)

(D) None of the above

(Ans: C)

8-The purpose of crankcase ventilation is to

(A) remove harmful particles from the engine

(B) provide proper lubrication to the engine

(C) provide air for combustion to the engine

(D) all of the above

(Ans: A)

9-The following part(s) is(are) lubricated by splash system

(A) Piston and piston rings

(B) Tappets

(C) Cams on camshaft

(D) All of the above

(Ans: D)

10-The following part is not lubricated by Pressure feed system

(A) Timing gears

(B) Valve rods and Push rods

(C) Rocker arms

(D)  Main bearings of crankshaft

(Ans: B)

Why the back wheel in the tractor is bigger than the front wheel?

The word “tractor” is related to words like “traction” and “tractive,” from the Latin word “tractus” meaning drawing (pulling): a tractor is essentially a machine designed to pull things along, usually very slowly and surely.

Reasons for having big wheel at rear and small ones at front:

1.Grip or Traction

Farm tractors spend a lot of their life working in muddy, bumpy fields. If you’ve ever been in car that has driven over a muddy field, you will know that the car slips around on the surface of the mud, or it gets stuck. A large tyre on a tractor has much better grip pads that can ‘bite’ into the ground, as well as a large surface area that distributes weight more evenly which means the traction is a lot better. 

2.Steering

The two smaller wheels at the front have a much better steering radius which means it’s easier to turn sharp corners. This is really important to cover the maximum area of the field while carrying out different jobs like ploughing, sowing and harvesting. Being light weight and small is also really beneficial for ease of control.

3.Visibility

The large rear wheels of the tractor fix the driver’s seat at a higher elevation which ensures good visibility of the nose of the tractor and the corners of the field it ploughs.

4.Cost

Small tyres cost less than larger tyres, and therefore it is much cheaper to replace small tyres that the very expensive big ones! It’s worth noting that because the rear tyres have a much thicker tread that they don’t need to be replaced as often as the front ones.

5.Weight distribution

Having the driving axle higher above the ground means the tractor can pull more weight without the front of the tractor rising up. It works like a lever, where twice the height means twice the maximum pulling force before the tractor tips over.

WHY TWO MOTORBIKES WITH SAME CUBIC CAPACITY BUT DIFFERENT MILEAGE!!

You might have noticed that motorbikes having same cubic capacity gives different mileage. For Example,Bajaj Platina has cubic capacity of 100 CC and it gives mileage of 104 kmpl,on the other hand Hero Splendor is also having same cubic capacity but it gives the mileage of 81kmpl.

It is mainly because the bikes like Platina has been made keeping in mind mileage.Parts are light to keep bike weight low.Carburetor is tuned to extract mileage though it puts a strain on engine which you can judge from harsh engine note.If you race it will shudder as it puts strain on engine.Also it gives Low torque, low BHP, and leaner air fuel mixture. Tyres are slim for less friction with road.All this saves you petrol but at a high maintenance cost & low resale value.High maintenance cost can be curtailed with regular servicing but if you give less petrol to engine then wear & tear will be more anyway.

PUMP vs COMPRESSOR

DIFFERENCE BETWEEN PUMP AND COMPRESSOR

Pump and compressor both are hydraulic machines used to increase the energy of fluid. Both of these devices used in industries and for domestic work. Pump is a device which is used to move the fluid (water, liquid and gases) and increase its elevation. It is mostly used to supply fluid from
low elevation to high elevation. A compressor is a device which is a mechanical device just like pump but it increases the potential energy of fluid by compressing it in a closed container.

The main difference between pump and compressor is that the pump is used to increase kinetic energy of fluid which further increases the elevation or pressure energy of it.  It moves the fluid from one place to another. But the compressor is mostly used to increase the potential energy (pressure energy) of fluid by pressuring it into a container. It is used to compress the fluid which increases its density and pressure. There are many other differences which are described below.

Difference between pump and compressor:

TERMS OF INTERNAL COMBUSTION ENGINES

1.)AFTER COOLER – A device used on turbocharged engines to cool air which has undergone compression.

2.)ATDC – After TDC, After top dead centre.

3.)AIR CLEANER – A device mounted on the intake manifold for filtering out unwanted solid impurities such as dirt and dust from air that is being drawn into the engine cylinder through the inlet manifold.

4.)AIR COOLED ENGINE – An engine that is cooled by passage of air around the cylinder, not by passage of a liquid through water jackets.

5.)AIR STANDARD CYCLE – A standard cycle of reference by which the performance of the different internal combustion engines may be compared, and their relative efficiencies calculated.

6.)AKROYD ENGINE – The first compression ignition engine, patented by Akroyd Staurt in 1890.

7.)ALUMINIUM CYLINDER BLOCK – An engine cylinder block cast from aluminium or aluminium alloy, and which usually has cast iron sleeves installed for use as cylinder bores.

8.)ANTIFREEZE – A chemical, added to the coolant (usually ethylene glycol) to lower its freezing point and thereby prevent the coolant from freezing in cold weather.

9.)ANTI ICING SYSTEM – A carburettor unit designed to prevent formation of ice on a surface or in a passage.

10.)ARTICULATED CONNECTING ROD – The auxiliary connecting rods of a radial engine, which work on pins carried by the master rod instead of on the main crankpin. Also called LINK RODS.

11.)BACK PRESSURE – A pressure exerted by a fluid contrary to the pressure producing the main flow. For example, pressure in the exhaust manifold, the higher the back pressure, greater is the resistance to flow of exhaust gases through the exhaust system. This lowers volumetric efficiency.

12.)CLEARANCE VOLUME – The volume remaining above the piston when the piston is at TDC.

13.)COMBUSTION CHAMBER – The space at the top of the cylinder and in the cylinder head or piston or both, in which combustion of fuel and charge takes place. The space enclosed by the piston, when the piston is at TDC.

14.)COMPRESSION RATIO – The ratio between the total volume of the cylinder when the piston is at BDC and the volume when the piston is at TDC.

15.)CONNECTING ROD – The rod made of steel or aluminium alloy usually having an I beam cross-section. A piston pin connects the connecting rod and the piston.

ANTILOCK BRAKING SYSTEM

Requirement of ABS Technology:

We know that when we apply brake, it pushes the brake pad on running drum or disk. For heavy loaded vehicle we need to high braking force
to stop of slow down the vehicle. This braking force generate by some means like hydraulic pressure, Air pressure etc. When the vehicle is running and we want to stop the vehicle we push the brake pedal. Due to excessive braking causes skidding. This skidding jam the wheel but due to inertia the vehicle tends to skid on the road and it became out of control from driver. This is called locking of the wheel.

This is understood by that when we run on the floor and eventually tends to stop we slip down on it. This is exactly true for the vehicle. This type of locking is harmful for driving and may cause accident. So we have to remove it use of a new safety system. This system is called ABS.

Working of ABS Technology:

We have been already explained how locking of road wheels due to excessive braking causes skidding. Modern antilock brake systems not only cause the vehicle to stop without deviating from its straight line path, these also provide directional stability since there is no skidding of the wheels.

Skidding is avoided by releasing the braking pressure just before the wheels lock up, and then reapplying the same. These releasing and reapplying the brakes in succession is what an antilock system does and this process is called pressure modulation. This system can modulate the pressure to the brakes about 15 times per second.  The feel of brake pedal in case of ABS equipped brakes is quite similar to that of conventional power brake system.

An ABS consist of an electronic control unit, one sensor on each wheel, an electrically driven hydraulic pump and a pressure accumulator. Accumulator is used to store hydraulic fluid to maintain high pressure in the braking system and to provide residual pressure for power assisted braking. ECU monitors and controls the antilock function when required. Its function is based on inputs from the wheel speed sensors and feedback from the hydraulic unit to determine whether the ABS is operating precisely and also to decide when the antilock operation is required. In some antilock braking system, a lateral acceleration sensor is also provided to monitor the side movement of the vehicle while taking a turn. This ensures proper braking during turns also.

When the front wheels of vehicle are locked, its maneuverability is reduced, whereas in case of rear wheel locking, the vehicle stability is reduced. ABS calculates the required slip rate of the wheels accurately based on the vehicle speed and the speed of the wheels and then controls the brake fluid pressure to achieve the target slip rate. Although ABS prevents complete locking of the wheel.

ABS is manufactured by Bendix, Delco Moraine, Kelsey-Hayes Lucas Girling, Bosch etc. 

IMPORTANT TECHNICAL TERMS OF AUTOMOTIVE VEHICLES

1.)AERODYNAMIC DRAG– is the air resistance to the motion of the vehicle.This consists of profile drag, induced drag, skin friction drag, interference drag, and cooling and ventilation drag.

2.)AERODYNAMIC LIFT– is the vertical component of the resultant force caused by the pressure distribution on the vehicle body.

3.)AIR BRAKE – A braking system which uses compressed air to supply the effort required to apply brakes.

4.)BOOSTER – Device incorporated in a car system (such as brake and steering),to increase pressure output or decrease amount of effort required to operate or both.

5.)CAMBER ANGLE – The outward (positive) or inward (negative) angle of the wheel centre line to absolute vertical.

6.)CASTER ANGLE – The rearward (positive) or forward (negative) angle of the steering axis to absolute vertical.

7.)CLUTCH PEDAL – A pedal in the drivers compartment that operates the clutch.

8.)CLUTCH SLIPPAGE – A condition in which the engine over revs during shifting or acceleration.

9.)DUAL BRAKE SYSTEM – Tandem or dual master cylinder to provide a brake system that has two separate hydraulic systems, one operating the front brakes, the other operating the rear brakes.

10.)EPICYCLIC GEAR– In the epicyclic gearing, at least one gear not only rotates about its own axis, but also rotates about some other axis.

What are the different uses for gas turbines?

if you want to know, What are the different uses for gas turbines then you came to right place because this gas turbine power plant lecture is about applications of gas turbine. The continued developments in gas turbine materials toward increasing the turbine inlet temperature and improving the components efficiency over the past decade has enlarged the spectrum of gas turbine applications to area such as power generation, utility industry, space, marine, automotive propulsion etc.. The main reasons of such a wide popularity being employed by the gas turbine is its advantages of simplicity, high power/weight ratio, smooth running, less maintenance, multi-fuel capability for combined cycle and reliability. The gas turbine applications can be divided in the following categories: 1) For electric power generation: The gas turbine are very popular for electric power generation because of the ability of starting and brought up-to full load quickly less cost of installation and maintenance. - Majority of the gas turbine power plants are used for peak load service with other types of power plants(steam and hydro power plants) - A large number of gas turbine power plants is also used as stand by power plants in hydro electric power plants. - Gas turbine power plants are also used as base load power plants where fuel oil or natural gas are cheap and easily available, water supply is scarce and load factor is very low(15-18%) - Now a day gas turbine plants are used to operate as combustion plants with steam plants, called as combined cycle power plant. 2) For jet propulsion engine: Every turbojet and turbo-propeller engine has a gas turbine. The turbine supplies power only to drive the air compressor in the turbojet engines while in the turbo propeller engines they may drive the propeller in addition to the compressor. 3) For supercharging: A small gas turbine run by the hot exhaust gases which is used to run supercharger(compressor) for aviation gasoline engines and for heavy duty diesel engines. 4) For marine field: A gas turbine can be also used for propulsion of ships or power generation on the ships. 5) Railway and road transport: Gas turbine can be also used for rail propulsion and high speeds road vehicles like racing cars. 6) Industry: Gas turbine are also employed for industrial applications like blast of air for blast furnace in steel industries, oil and other chemical industries. Gas turbine is also used to supply preheated combustion air, hot gases for an industrial process in petrochemical industries.

working principle of gas turbine power plant

working principle of gas turbine power plant :

in a gas turbine first air is obtained from the atmosphere and compressed in an air compressor. this high prsuure air is then pased into the combustion chamber, where it is heated due to  combustion of fuel. The product of combustion(hot gases) of high pressure and temperature passes through the passages formed by the stationary and rotating blades of gas turbine. Ajet of hot gases is made to flow over ring of blades imparting rotary motion to the shaft of turbine. A large part of power developed by the turbine rotor is consumed for a driving a compressor which supplies air under pressure of combustion chamber, while remaining power is utilized for doing the external work.

Gas turbine engines derive their power from burning fuel in a combustion chamber and using the fast flowing combustion gases to drive a turbine in much the same way as the high pressure steam drives a steam turbine. A simple gas turbine is comprised of three main sections a compressor, a combustor, and a power turbine. The gas-turbine operates on the principle of the Brayton cycle, where compressed air is mixed with fuel, and burned under constant pressure conditions. The resulting hot gas is allowed to expand through a turbine to perform work.

In an ideal gas turbine, gases undergo four thermodynamic processes: an isentropic compression, an isobaric (constant pressure) combustion, an isentropic expansion and heat rejection. Together, these make up the Brayton cycle.

In a real gas turbine, mechanical energy is changed irreversibly (due to internal friction and turbulence) into pressure and thermal energy when the gas is compressed (in either a centrifugal or axial compressor). Heat is added in the combustion chamber and the specific volume of the gas increases, accompanied by a slight loss in pressure. During expansion through the stator and rotor passages in the turbine, irreversible energy transformation once again occurs. Fresh air is taken in, in place of the heat rejection.

MEANING OF RTR IN TVS APACHE

RTR in Apache means Racing Throttle Response .

Throttle response or vehicle responsiveness is a measure of how quickly a vehicle's prime mover, such as an internal combustion engine, can increase its power output in response to a driver's request for acceleration. Throttles are not used in diesel engines, but the term throttle can be used to refer to any input that modulates the power output of a vehicle's prime mover. Throttle response is often confused with increased power but is more accurately described as time rate of change of power levels.

Formerly, gasoline/petrol engines exhibited better throttle response than diesel engines. This results from higher specific power output and higher maximum engine power, as well as the fact that lower-powered diesel engines were disproportionately heavier. Recently diesel engines became able to outperform similar-sized petrol engines. Most naturally aspirated gasoline engines have better responsiveness than supercharged or turbocharged engines for engines with similar peak power outputs. However, factors such as improper maintenance, fouled spark plugs or bad injectors can reduce throttle response. Diesel engines are less likely to lose throttle response, since their power comes from self-igniting fuel. Older diesel engines directly connect the accelerator pedal to the injection pump resulting in instant response.

Several tuning factors can affect engine responsiveness.Throttle response in manual cars can be enhanced by dropping to a lower gear before accelerating. This action is often used in smaller cars to aid in overtaking.