Saturday, July 15, 2017

Spark plug working and its construction

Spark plug is used in all automobile engines whether it’s two wheeler, three wheeler, four wheeler or even bigger vehicles. Spark plug is an electrical device which is mounted on cylinder head of internal combustion engines, this electrical spark plug generated a spark which is used to ignites the compressed fuel uses in engines


Spark plug consists of an insulated central electrode which in turn connected through an insulated wire to the ignition coil where ignition is required. This insulated wire may also be connected to the magneto circuit on the outside and form a grounded terminal on the base of the plug. A spark gap in cylinders of and Internal combustion engines is usually divided into:-

(i)            Spark-ignition engines:-
These engines required spark plugs to begin combustion,
(ii)           Compression-ignition engines Known as diesel engines:-
           In these engines air is compressed and then diesel fuel injection is done into the heated compressed air mixture where fuel gets auto ignition.

Compression-ignition engines may use glow plugs to improve cold start characteristics.
There are following functions of Spark plugs:-

There are two primary functions of Spark Plugs
(i)            To ignite the air/fuel mixture.
As discussed earlier electrical spark generated through spark plug , this spark jumps the air gap when voltage applied to spark plug is high enough for crossover of air gap. This spark is used to ignite the air/ fuel mixture in combustion chamber.


(ii)          Removal of heat from Combustion chamber:-
There is misconception that spark plugs create heat but spark plugs are used to remove hear instead. Temperature at the end of spark plug i.e. firing end must be kept low to such levels so as to prevent pre-ignition. Also it should  be kept in  mind that temperature must not be so high so as to prevent unwanted firing.
The heat range of the spark plug must be carefully selected  as if heat range is not correct we will face of troubles. Spark plug firing end temperature is between 900-1,450 degrees. If <900 degrees, carbon polluting is possible. If Temperature is >1500 degree than overheating becomes an issue.
Spark plug acts as a heat exchanged i.e. removes non-useful thermal energy from combustion
chamber and transfers that heat into engine cooling system.
Ability of spark plug to remove heat from spark plug tip and is called as heat range.

Operation of Spark plug :

The spark plug is connected to ignition coil or magneto high voltage generation end. Due to this high voltage at one end there will be potential difference between center of electrode and side electrode. Now due to air gap ignition doesn’t happen now when voltage level reaches to high level then air fuel mixture get ionized and at certain level whole air fuel mixture get ionized and this ionized gas becomes good conductor of electricity and this ignites spark across gap.
Voltage required to generated spark is usually of the level of 20KV-100KV.

When air gap get ionized such that current starts flowing across gap then , temperature level attained will be around 60000 K. This extreme heat causes the expansion of air and fuel mixture to expand more quickly and there will be small explosion.

There are two type of spark plus:-
(i)            Cold Spark plugs
(ii)           Hot spark plugs
Cold Spark Plugs:-
 In these spark plugs heat flow path is short. It is shortened so that there will be faster heat transfer and also you can find small insulator nose on these spark plugs and surface area of this insulator nose is smaller. Due to smaller surface area high heat absorption could not occur in these spark plugs.

Hot Spark Plugs:-
These spark plugs have longer insulator nose so longer heat transfer path. As there is longer heat transfer path so which leads to slower heat transfer to the surroundings cylinder heads.

There are following parts of spark plugs:-
(i)            Insulator
(ii)           Hexagonal
(iii)          Shell & Plating
(iv)         Gasket
(v)          Threads
(vi)         Ground electrode
(vii)        Central electrode
(viii)       Spark plug electrode gap
(ix)         Insulator nose or end tip of insulator
(x)     Terminal nut
(xi)     Resistance

Spark plug parts; functioning of different parts of spark plug


(i)    Insulator: Insulator body is usually made from Aluminum oxide ceramic. Then high pressure dry molding technique is used for construction of insulator. When molding is done then it is fired in kiln to temperature that even exceeds the melting point of steel, by doing this insulator will properties such as high dielectric strength, excellent resistance to shock and very high thermal conductivity. On outer surface of spark plug circles so as to provide grip of spark plug.


(ii)  Hexagonal:-This is provided as to provide grip of fixing the spark plug at required place and tightening of spark plug is done from that point only.

(iii) Shell and Plating:- Shell is just below hexagonal and is made using special cold extrusion process. Now this shell is plated to provide protection against the rust and corrosion.


(iv) Gasket:- These may or may not be used in spark plugs. Where gasket is used in Spark plugs there gasket is having folded steel design that provides a smooth surface for sealing purposes. Spark plugs without gaskets have a tapered seat shell which seals through close tolerance.

(v)  Threads:- Threads are used to mount the spark plug at specified location and these threads are made though rolling process instead of cutting the same.


(vi) Ground electrode: Ground electrodes are made from nickel alloy steel and made into different shapes. Property of ground electrode is that under extreme temperature and pressure conditions ground electrode be resistant to both spark erosion and chemical erosion.

(vii)  Center electrode:- Central electrode also should have same properties as that of ground electrode i.e. it must sustain extreme temperature and pressure conditions.


(viii)  Electrode gap:-The gap between ground electrode and center electrode is known as spark plug electrode gap. Gap should be kept as minimum as possible but could not touch the tip of insulator as required spark will not produce in that case.

(ix)  Insulator nose or end tip of Insulator:-There are carbon deposits with passage of time on insulator tip due to sparks generated during period of operation so spark plug nose shape and size is such that it should be capable of removing carbon content, oil and fuel deposits.

(x)  Terminal Nut:- There are two options available in spark plug for connections i.e. spark plug comes with terminal nut or without terminal nut i.e. with threaded nut and connection type or even both. Terminal nut can be detached from spark plug.


(xi) Resistance:- Resistance is provided to high voltage provided to spark plugs so that current could not be very high. Resistance is also kept in thousands. Resistance vary from 1000- 7000 ohms. 5000 ohm is usually cut of point for because it provides a value between where spark plugs are manufactured and where problems seem to appear with high resistance. Most reports Tempest receives about rough running engines associated with high spark plug resistance involve values of 7000 ohms or more. 

Sunday, July 9, 2017

Turbocharger working principle; Turbocharger

Turbocharger is the word most widely used in automobile sector. Now days its is integral part of cars.
Now days turbochargers are used mainly on diesel engines, but now-days initiatives has been taken to use turbo charging of production petrol engines. Turbochargers are most helpful while using them at high altitudes as air is less dense at high altitudes and by using turbocharger we will enable to get more power.  


There are following advantages of turbochargers :-
1.   By using turbocharger engines will go faster.
2.   Engine performance can be improved
Turbocharger consists of pair of fans that connect waste exhaust power from the back of an engine to force more air into the facade, providing more "energy".
Earlier days there is lot of exhaust fumes coming out of vehicles which causes air pollution. This air pollution leads to lot of waste of energy. This waste energy consists of heat as well kinetic energy which get wasted in atmosphere. By using Turbocharger you can use this waste heat and generate more economy and more kinetic energy.
Car engines works on principle that it consists of cylinders where air enters in every cylinder which get mixed with fuel and fuel burns in presence if air which leads to pushing of pistons, shafts turning and gears which leads to spinning of car wheels. Now when piston comes back to its position then it brings waste air and fuel mixes with waste air and which goes out of vehicle as exhaust. Thus we see that fuel goes out along with exhaust as un-burnt. Power generated by engine is directly proportional to how fast fuel get burnt. So if there are more cylinders then more power will get generated as more fuel get burnt every time. Which will leads to faster movement of vehicle.

So there will two options to generate more power:-
1.   By increasing more cylinders
2.   By using turbocharger.
Out of these two method using turbocharger is cheaper and simpler technology. In sports cars there are 8-12 cylinders instead of 4 cylinders in family cars.
How does a turbocharger work?
Turbocharger works in similar principle to that of jet engines. In turbochargers exhaust gas is used to drive a turbine which spins an air compressor and air compressor drives extra air into the car cylinders, Which will ultimately leads to burning of more fuel each second. Which will results into more power.
Turbocharger consists of two fans also called as impellers or gas pumps which are two in number. These are fitted on same shaft so that these will spin together.
One Fan is called turbine and another is called as compressor.
Turbine is usually mounted on exhaust flow from cylinder when exhaust gases flows out of cylinders than this turbine blades starts rotating and so connected shaft also start rotating.
Compressor also mounted on same shaft that of turbine also starts rotating. It is mounted on intake of vehicle which results into giving more air to cylinders.
Now when air is compressed by compressor than air get heated up and heated air will be lesser dense and which leads to lesser help in fuel burning. Thus it would be effective if air coming from the compressor will be cooled before entering the cylinders so to do this heat exchanger is used to remove heat from air.

Advantages of using Turbocharger:-
(i)           These can used both for gasoline as well as diesel engines
(ii)          With turbocharger we will get more power output with same size of engine.
(iii)        Turbocharger will leads to better fuel economy as this will leads to savings of 8-10% of fuel.
(i)           Turbocharger will leads to burning of fuel in more oxygen which leads to clean and complete burning of fuel which leads to reduced air pollution.
(ii)          Reduced size of engine with same capacity of engine will leads to lesser fuel consumption.
Disadvantages of Turbochargers:-
(i)           But there is disadvantage with Turbocharger is that these will leads to worse performance of engines in small engines.
(ii)          Turbochargers leads to complexity of engine.Which will leads to increase maintenance cost.
(iii)         Turbocharging principle is getting the power output from same engine. So there will be more temperature developed in engines and high pressure on pistons. Which leads to failure of engine more frequent, which means life span of engine get reduced.

(iv)              It will require more skills to drive cars fitted with turbocharger, as turbochargers are powered through exhaust gases so this will leads to delay between accelerator and the turbo starts.

Sunday, July 2, 2017

Nature of electricity; Electricity Nature

The Nature of Electricity

Electricity is caused by movement of electrons. Lighting is natural source of electricity. Electricity we uses for day to day activities is generated in power plants. There is often question arises that how electricity was get generated and what is nature of electricity.

For knowing nature of electricity you must know about Structure of atom:-

Structure of the atom

Every substance is made of atoms An atom is the smallest particle of an element that still keeps the properties of the element, atoms consists of small particles known as  Electrons, Protons, and neutrons.

Electrons: - These have negative charge
Protons: - These have Positive charge
Neutrons: - These don’t have any charge

The electron is a particle which have very lightweight. Protons are very heavier about 1,840 times heavier than electrons. Electrons are the smallest type of atomic particle.

In Electricity Electrons and Protons plays an important role. Neutrons play no part in electricity. 
Just like solar system where planets orbit around sun, similarly in atoms proton forms the nucleus and electrons orbit around these protons. Atomic number of any element indicates no. of electrons orbiting around proton. These electrons are different distances from nucleus and they revolve around nucleus in layers.  Electrons which were closer to protons were tightly held and farthest electrons are not strongly held.


Nature of electricity

Picture shows drawing of Hydrogen atom which is simplest among all atoms as it contains only one electron and proton. Proton is shown at the center and electron is orbiting around the proton. So all atoms have similar construction only difference is between no. of protons , electrons and neutrons. Hydrogen atom have only one electron and proton so electron is tightly attached to proton so it will be very difficult to dislodge electron from Hydrogen atom.  

Electrons can be removed by different ways one way to remove the electron is when lighting strikes on some substance and another method is to through friction i.e. by rubbing the substance.

When energy is applied to the atom then electrons which were farthest from nucleus will get easily dislodged from the orbit in which they rotate. They electrons will become free electrons and in this way we will get number of free electrons.
These free electrons also known as random electrons that move about the molecular structure of the material are what makes up electricity. 

If it is easy to dislodge electrons from atoms orbit then it is known as good conductor of electricity e.g. Aluminium and copper are good conductors of electricity. Similarly the substance where electrons are very difficult to dislodge are known as bad conductor of electricity.

How Electric Charge Produced
As we have seen that atoms can lose electrons and other atoms can gain these free electrons. So it becomes possible to transfer electrons from one object to another. So there will not be equal distribution of positive and negative charge on object. Thus there will be one object with higher electrons and its polarity will becomes negative and other object which losses electrons becomes Positively charged.
When there are two objects contains the same charge, that is, both positive and both negative, the objects are said to have like charges. When two objects has different charges, that is, one body is positive while the other is negative, they are said to have unlike or opposite charges. The law of electric charges may be states that “Like charges repel each other; unlike charges attract each other”.

Potential difference

The ability of a charge to do work is called its “potential”. When one charge is different from the other, there must be a difference in potential between them. It is this potential difference which leads to flow of current and hence generation of electricity.





Friday, June 23, 2017

Comparison between lean burn and Rich Burn engines

Comparison between lean burn and Rich Burn engines:-
After certain emission calibration levels Lean‐burn gas engines are more economical  and these can even operate at higher loads,
But in rich‐burn engines have lower emission levels with a single after treatment these are more tolerant of broad fuel ranges and ambient conditions, and generally have better transient load capability.


Principle of operation of Rich Burn engines:-
Rich‐burn engines operate at principle of stoichiometric air/fuel ratio (AFR) according to this principle air in exact quantity is supplied to burn all of the fuel.  This will leads to reduction in nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and HAPS (Hazardous Air Pollutants) after certain treatment for all in one i.e. by using catalytic converter used in cars.

Lean burn engines working principle:-
In these engines Lean‐burn engines use a lot of excess air. These engines take up to twice the amount needed in rich burn engines for complete fuel combustion. Excess air used in lean burn effectively cools down the peak combustion temperatures in the cylinder, this will reduces the NOx production and allows low engine‐out emissions without the need for an after treatment system in many applications.
In these engines there are advantages of reducing the detonation probability thus it will leads to higher Brake Mean Effective Pressure loads and an optimized combustion phasing. This results in higher power density and usually produces better fuel efficiency.

Emissions in Rich-burn engines:-
Rich‐burn engines have emissions of 12‐16 g/bhph‐hr NOx i.e. “5,000 ‐ 6,500 mg/Nm3@ 5 percent 02 in the exhaust gas “, in most stoichiometric/AFR exhaust gas composition and the increased exhaust gas temperatures allow the use of a three‐way catalyst.
These engines  have high NOx conversation rates i.e. above 99 percent that significantly reduce all three major types of engine‐out emissions ‐ NOx, CO and HC , Since there are low emissions that will destroy inferior but hazardous pollutants like formaldehyde (CH20).
Rich-burn engines emission are below 50 mg/Nm3 NOx and ultra‐low total hydrocarbon emissions, which will leads to decreased overall greenhouse gas footprint.


Emissions in Lean Burn Engines:-
If we have requirement of High power density and we required highest possible efficiency at moderate emission levels of 500 or 250 mg/Nm3 NOx (@ 5 percent 02 in the exhaust gas) lean burn engines have advantage. These engines at an adequate gas quality they deliver BMEP levels of up to 24 bar with electrical efficiencies up to 46.5 percent  without the need for a NOx or THC after treatment system.

To lower the NOx emissions that are reached by rich‐burn engines with a three‐way‐catalyst, lean-burn engines require selective catalytic converters with urea injection.
Oxidation catalysts perform most of the CO reduction in lean‐burn engines but  the fuel gas must be very pure. These catalysts also can reduce CH20 emissions ‐ again, if the gas is pure ‐ but their low exhaust temperature limits hydrocarbon conversion efficiency.

Operational flexibility
Rich burn engines can operate effectively only at clean fuels such as Natural gases. These will not operate at Biogas, Sewage gas or landfill gases as these will poison the three way catalyst. High combustion temperatures restrict specific output and the BMEP, so there is lower efficiency than with lean‐burn engines operating at higher air/fuel ratios. If lean burn engines are calibrated to operate at extremely low NOx levels (ultra‐lean), their efficiency begins to degrade so that the difference between rich‐burn and lean‐burn fuel consumption is minimized. Since lean‐burn engines have a much higher AFR ‐ with about 10 percent excess oxygen in the exhaust ‐ their engine‐out NOx emissions are only 5 percent to 10 percent of the amount discharged by a rich‐burn engine. Lean‐burn engines require selective catalytic reduction (SCR) treatment to obtain the lowest possible NOx emissions levels in the exhaust gas. SCR injects a controlled amount of urea into the catalyst to convert NOx to nitrogen. Being able to operate at a more optimal AFR with an SCR system makes the lean‐burn engine very efficient and allows high break mean effective pressures.


Oxidation catalysts are used to provide most of the CO and NMHC reduction in lean‐burn engines but, as with other catalytic systems, the fuel gas has to be very pure. These catalysts also can reduce CH20 emissions ‐ again, if the gas is pure ‐ but their low exhaust temperature limits hydrocarbon conversion efficiency

Saturday, April 22, 2017

Air conditioner Complete selection and installation guide

Why we need to Know Area of room before selection of air conditioner?

There is often confusion arises in customer mind that what size of air conditioner will be sufficient for their room. Most often everyone get some information from friends or from seller itself. Even other customers just try to explain their own experience and you buy according to their experience, and sellers always try to sell those products from where they get maximum profit.

So it will become very important to know what size of air conditioner should be selected for effective cooling of room, although friends experience gets to arrive at good product. But you should know how to select right capacity of Air conditioner as per requirements.

If you buy an air conditioner with higher capacity from requirements then this will leads to excessive power consumption and if lower capacity air conditioner selected then cooling will not be achieved which will defeat the purpose of air conditioner installation.

Air conditioners server two purposes:-
(i)                  For cooling
(ii)                For Dehumidification

If Air conditioner selected with higher capacity then requirement then it will cools the room and get auto-stop before removing the humidity from air, this will leads to uncomfortable inside room as room is cool and moist air will make you feel damp and clammy. 
Also higher capacity will ultimately leads to reduction in air conditioner efficiency.

Check your Room size appropriately:-

It is often practice to measure room size in Square feet’s.  For rooms are square and rectangular in shape than simply multiply the length into width. For Triangular rooms multiply Length and breadth and divide the area calculated by two to arrive at size of room. If room shapes are complex then you have to calculate room size accordingly or take help from sales executives to arrive at exact area.

Cooling capacity according to room size
Cooling capacity requirements will be calculated with help of BTU per hour i.e. British Thermal units. Now from BTU size of air conditioner can be calculated. For taking out heat of 12000 BTU/Hour size of air conditioner required is 1 ton so by using this air conditioner size can be chosen. Below table will help you out in selection of air conditioner according to BTU/Hour
Area To Be Cooled (square feet)
Capacity Needed (BTUs per hour)
Air conditioner size
100 up to 150
5,000
 0.5 ton
150 up to 250
6,000
0.5 ton
250 up to 300
7,000
0.75 ton
300 up to 350
8,000
0.75 ton
350 up to 400
9,000
0.75 ton or next higher size 1 ton
400 up to 450
10,000
1 ton
450 up to 550
12,000
1 ton
550 up to 700
14,000
1.25 ton or 1.5 ton if 1.25 not available
700 up to 1,000
18,000
1.5 ton
1,000 up to 1,200
21,000
1.75 ton or 2 ton of 1.75 ton not available
1,200 up to 1,400
23,000
2 ton
1,400 up to 1,500
24,000
2 ton
1,500 up to 2,000
30,000
2.5 ton
2,000 up to 2,500
34,000
3 ton

There are following parameters which will also be considered or taken care:-

(i)                  If room is considerably shaded than reduce your air conditioner requirement by 10%
(ii)                If room is front facing of sun then increase the capacity of air conditioner by 10%
(iii)           If there are persons more than 2 in a room then add 600 BTU per person in capacity addition i.e. increase of 5% capacity.
(iv)           If you are needed to add this unit into Kitchen then you should add heat generated during cooking i.e. add capacity of 4000-5000 BTUs in your capacity i.e. increase the capacity by at-least 30%
Location of Indoor and outdoor unit in room:-
(i)            Following points might be considered while installation of air conditioner in room
(ii)          Indoor Unit installation points:
(iii)         Air conditioner should be installed at location where air will be evenly distributed in whole room.
(iv)        Air conditioner should be installed at appropriate height. Usually height of air conditioner should not be more than 7-9 feet as if height is more than that than air conditioner mere serve the purpose of cooling your roof only. 
(v)          Try to install air conditioner above bed so that effective cooling can be obtained. Few don’t like air directly on body so you can install air conditioner on wall which is towards your feet or you can change direction of air using louvers

Outdoor Unit location:
         i.        Outdoor unit should be installed in open space i.e. terrace of house or if terrace isn’t available than you can hand the same external wall of house. It should be always installed were free flow of air is available so that air can flow above compressor and condenser.
       ii.            Outdoor unit location should be easily accessible so that easy maintenance can be carried out.
      iii.            One very important point should be considered while installation of outdoor unit is that outdoor unit should always be installed above the position of indoor unit so that free flow of refrigerant can be achieved and compressor can function to full capacity. If outdoor unit location is below indoor unit then some of compressor capacity is utilized in pumping the refrigerant to indoor unit. This will leads to overall lower performance of compressor.
     iv.            Last but foremost important point of installation of outdoor unit is that distance between indoor and outdoor unit. In tubing refrigerant at very low temperature flows inside tubing between indoor and outdoor unit. There is always loss of some refrigerant to atmosphere from tubing so it is always advisable to install outdoor unit as closer to indoor unit as possible to reduce the loss of the cooling effect. The maximum distance between the indoor and the outdoor units can be about 15 meters.
Dif      
           Difference between single Stage and Two Stage compressor Air conditioners:-   
          Difference between these two air conditioners are basically levels of operation in air conditioners
          Single Stage air conditioners compressors only works on single level of operation i.e. only for cooling the area, but two stage air conditioners compressors have two levels of operation i.e. they cool the room at full level as in case of single stage air conditioner compressors and provide mild cooling when temperature outside is not very high.
            So dual stage compressor technology provides comfortable cooling as per requirements.
           So there are following benefits of dual stage compressor technology in air conditioners
            As these air conditioners provided cooling as per requirements and don't always operate at full level as in case of single stage compressor air conditioners so these leads to energy savings , which will leads to lower down your electricity bill.
           Second most important advantage is that they provide comfortable cooling.

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