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

(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. 

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.

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.

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.

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.