generation of electric power from a two stock engine

8/2/2019 Generation of Electric Power From a Two Stock Engine

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PROJECT REPORT

ON

WORKING OF TWO STOCK

This Project Report submitted in the Partial Fulfillment of the

Requirements for the Mechanical Engineering

Submitted To:- Submitted By:-Mr. Sovit Saini Deepchand (0904217111)H.O.D. of Mechanical Deptt. Punit Jain (0904217093)

S.K.P, Kurukshetra Sunny Goyal (0904217074)

Sarvjeet (0904217115)

SHRI KRISHAN POLYTECHNICKURUKSHETRA


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ACKNOWLEDGEMENT

It is our privilege to acknowledge with respect and gratitude, the keenvaluable and ever-available guidance render to us by MR. Pardeep Narwal &

NAVDEEP NAIN Lecturer in Department Of Mechanical Engg. Of SHRI

KRISHAN POLYTECHNIC (DEV BHOOMI), Kurukshetra. We shall

always be grateful to them for providing us strength, perception and patience

to complete this work. The fact remains that it is virtue of their rich

experience and versatile knowledge which enabled us to complete this

project report. At the same time , we will like to give a special thanks to all

my friends for their valuable suggestions . They illuminated many dark

corners of the subject .Above all, we thank almighty , for the light he has

kindled on us, which has led the path we are all on

Submitted By-:

Punit Jain (R. no. 0904217093)

Sarvjeet (R. No. 0904217066)

Sunny Goyal (R. No. 0904217074)Deepchand (R. No. 0904217111)


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CERTIFICATE

This is certified that the project cultivated Power generation byTwoStock Engine is the bonafide of Mr. Punit Jain, Sarvjeet,

Sunny Goyal , Deepchand. This is submitted for partial fulfillment of awards

of diploma in MECHANICAL ENGINEERING the state board of

technical education, Chandigarh Haryana.

It is further certified that he has work for their complete semester for

preparing this project in many opinions, the project report is up to the

required standard and recommended this project might be sent for

evaluation.

Guide By-:

Mr. Pardeep Narwal &

Mr. Navdeep Nain

DEPARTMENT OF MECHANICAL ENGINEERING


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IntroductionMECHANICALLY, the two-stroke engine is very simple, and unfortunately on

too many occasions this apparent simplicity has fooled would-be tuners into believingthat this type of power unit is easy to modify. Just a few hours work with a file in the

exhaust and inlet ports can change the entire character of the engine for the better, but

if you go just 0.5mm too far, you could end up with a device slower than its stock

counterpart.Therefore modifications must be planned carefully, keeping in mind that seldom,

if ever, is the biggest (or most expensive) the best. As you plan your modifications

always tend to be conservative. If necessary, you can go bigger later.

Possibly the worst viewpoint you can start out with is that the manufacturer didn'tknow what he was doing. I started out thinking that way too; but then I began to realise

why the engineers did it that way. Pretty soon I was learning more about what makes a

two-stroke fireand making fewer mistakes.You must keep in mind that all production engines are a compromise, even highly

developed racing engines like the Yamaha TZ250. You can make the TZ churn out

more power, but will you be able to ride it with the power band narrowed right down,and do you have the experience to handle a sudden rush of power at the top end on an

oily or wet track? Also, think about the added wear caused by more rpm and

horsepower; do you have the finances to replace the crankshaft, pistons and cylinder

more frequently now that you are running at 12,500rpm instead of 11,500rpm? Whenyou begin to think about things like this, you start to understand a few of the reasons

why manufacturers make compromise engines and machines. Remember the TZ250

started out as a road racer, so you can imagine some of the problems you could comeup against if you were to modify a single cylinder 125 motocross engine for use in a

road racer.

Obviously the first work you should do is bring the engine up to the

manufacturer's specifications. This is termed blueprinting, and involves accuratelymeasuring everything and then correcting any errors made in production. You will be 9

amazed at the gains to be made, particularly in reliability, and to a lesser extent in

performance, by correcting manufacturing deficiencies. I am convinced manufacturersbolt their road racers together merely to make shipping all the pieces easier, such are

their tolerances.

I have seen engines that have never been started with piston clearances larger than

the manufacturer's serviceable limit. Conrods that vary 0.4mm in centre to centrelength and 20 grams in weight, on the same crank. Crankwheels which are 0.1mm

outside true centre. Cylinder heads with a squish band clearance of 1.7mm, instead of

0.7-1.0mm. Cylinders with port edges so sharp that the side of the piston and ringswould have been shaved away in a few minutes' running. New pistons with cracks. New

cylinder heads that are porous.

Included in blueprinting is cleaning the rough cast out of the ports, and matching

all gaskets so they don't overlap the ports. The transfer ports must be matched to the


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crankcase. The carburettor should coincide with the mounting flange and inlet port.

Anything the manufacturer has not done (presumably to cut costs), you should do.Blueprinting is slow, tedious work, and it can be expensive when crankshafts have

to be separated and then machined and trued, or when cylinder heads have to be

machined to close up the squish band without raising the compression ratio. It is not

very exciting work because when you have finished the engine is stock standard, andtelling your mates all the work you have done won't impress them. But don't let this

put you off, the basis for any serious tuning must begin with bringing the engine up to

the manufacturer's specifications.Most people won't believe how close to standard are the motors used by the

factory racing teams. Other riders are convinced that, because the factory boys are

quicker, they must have more power and lots of trick parts. In truth, the differences arein frame geometry and the ability of the factory rider to ride faster and make the right

choice of tyres, suspension settings, gearing, jetting etc. Plus, of course, they use

blueprinted engines.

So that there is no misunderstanding of the two-stroke operating cycle I will

describe what goes on in each cylinder, every revolution of the crankshaft.The first example is the piston-ported Bultaco Matador Mk4 which, like most

modern two-strokes, operates on the loop scavenge principle. As the piston goes up,the inlet port is opened by the piston skirt at 75 before TDC (Top Dead Centre) and

the atmospheric pressure (14.7 psi) forces air/fuel mixture in to fill the crankcase

(FIGURE 1.1). The piston continues to rise to TDC, compressing the fuel/air chargeadmitted on the previous cycle. At 3.2mm before TDC the spark plug fires, sending the

piston down on the power cycle. As the piston continues its descent the inlet port is

closed and the fuel/air mixture is partially compressed in the crankcase. 85 before

BDC (Bottom Dead Centre) the exhaust port is opened by the piston crown and theexhaust gases flow out. After another 22 (63 before BDC) the blow-down period

finishes and the piston crown exposes the transfer ports to admit the fresh fuel/air

charge. This is forced up the transfer passages due to the descending piston reducing

the crankcase volume by the equivalent of the cylinder displacement, in this instance244cc. As the piston begins rising, the mixture continues to flow into the cylinder and

the exhaust gas continues flowing out. The piston continues rising, closing off first the

transfer and then exhaust ports. Next the inlet port opens, to start the cycle over again.10 Rotary valve engines operate on the same loop scavenge principle, but in this case

a disc partially cut away and attached to the end of the crankshaft opens and closes an

inlet port in the side of the crankcase. The Morbidelli 125 twin road racer is a rotaryvalve engine. The inlet port opens 30 after BDC and closes 79 after TDC. The piston

crown opens and closes the exhaust and transfer ports.

The following pages will provide you with the knowledge necessary to develop a

successful two-stroke competition engine, but do keep in mind the principles outlinedin this chapter so that you avoid the most basic pitfalls associated with two-stroke

tuning.


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A -mixture in cylinder is compressed & inlet cycle begins.B-mixture in crankcase is compressed.C- exhaust cycle begins & primary compression continues.

D- transfer cycle begins & exhaust cycle continues.


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Two-stroke engineAtwo-stroke engineis aninternal combustion enginethat completes the process cyclein one revolution of the crankshaft (an up stroke and a down stroke of thepiston,compared to twice that number for afour-stroke engine). This is accomplished by usingthe end of the combustion stroke and the beginning of the compression stroke to perform

simultaneously the intake and exhaust (orscavenging) functions. In this way, two-strokeengines often provide highspecific power, at least in a narrow range of rotational speeds.The functions of some or all of the valves required by a four-stroke engine are usually

served in a two-stroke engine by ports that are opened and closed by the motion of thepiston(s), greatly reducing the number of moving parts. Gasoline (spark ignition) versions

are particularly useful in lightweight (portable) applications, such as chainsaws, and the

concept is also used in dieselcompression ignitionengines in large and weightinsensitive applications, such as ships and locomotives.The first commercial two-stroke engine involving in-cylinder compression is attributed to

Scottish engineerDugald Clerk, who in 1881 patented his design, his engine having aseparate charging cylinder. The crankcase-scavenged engine, employing the area below

the piston as a charging pump, is generally credited to Englishman Joseph Day.

ApplicationsThe two-stroke engine was very popular throughout the 20th century in motorcycles and

small-engined devices, such aschainsawsandoutboard motors, and was also used insome cars, a few tractors and many ships. Part of their appeal was their simple design

(and resulting low cost) and often highpower-to-weight ratio. The lower cost to rebuildand maintain made the two stroke engine incredibly popular, until the EPA mandatedmore stringent emission controls in 1978 (taking effect in 1980) and in 2004 (taking

effect in 2005 and 2010). The industry largely responded by switching to four-stroke

engines, which emit less pollution than two stroke engines[1]. Many designs use total-loss lubrication, with the oil being burned in the combustion chamber, causing "bluesmoke" and other types of exhaust pollution. This is a major reason for two-stroke

engines being replaced by four-stroke engines in many applications.
http://www.epa.gov/nonroad/proposal/r01049.pdfhttp://www.epa.gov/nonroad/proposal/r01049.pdfhttp://www.epa.gov/nonroad/proposal/r01049.pdfhttp://www.epa.gov/nonroad/proposal/r01049.pdf


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Two-stroke engines continue to be commonly used in high-power, handheld applications

such asstring trimmersand chainsaws. The light overall weight, and light-weightspinning parts give important operational and even safety advantages. For example, only

a two-stroke engine that uses a gasoline-oil mixture can power a chainsawoperating inany position.

These engines are still used for small, portable, or specialized machine applications suchasoutboard motors, high-performance, small-capacitymotorcycles,mopeds,underbones,scooters,tuk-tuks,snowmobiles,karts,ultralights,model airplanes(and other model vehicles)andlawnmowers. The two-stroke cycle is used in manydiesel engines, most notablylarge industrial and marine engines, as well as some trucks and heavy machinery.

A number of mainstreamautomobilemanufacturers have used two-stroke engines in thepast, including the SwedishSaaband German manufacturers DKWandAuto-Union. TheJapanese manufacturerSuzukidid the same in the 1970s.Production of two-stroke carsended in the 1980s in theWest, butEastern Bloccountries continued until around 1991,with theTrabantandWartburginEast Germany.Lotusof Norfolk, UK, has a prototype

direct-injection two-stroke engine intended for alcohol fuels called the Omnivore which itis demonstrating in a version of theExige.

Different two-stroke design types

Although the principles remain the same, the mechanical details of various two-stroke

engines differ depending on the type. The design types vary according to the method ofintroducing the charge to the cylinder, the method of scavenging

thecylinder(exchanging burnt exhaust for fresh mixture) and the method of exhaustingthe cylinder.

Piston-controlled inlet portPistonport is the simplest of the designs. All functions are controlled solely by thepiston covering and uncovering the ports as it moves up and down in the cylinder. A

fundamental difference from typical four-stroke engines is that thecrankcaseis sealedand forms part of the induction process in gasoline andhot bulb engines. Diesel engineshave mostly aRoots bloweror piston pump for scavenging.
http://en.wikipedia.org/wiki/Pistonhttp://en.wikipedia.org/wiki/Pistonhttp://en.wikipedia.org/wiki/Crankcasehttp://en.wikipedia.org/wiki/Crankcasehttp://en.wikipedia.org/wiki/Crankcasehttp://en.wikipedia.org/wiki/Hot_bulb_enginehttp://en.wikipedia.org/wiki/Hot_bulb_enginehttp://en.wikipedia.org/wiki/Hot_bulb_enginehttp://en.wikipedia.org/wiki/Roots_blowerhttp://en.wikipedia.org/wiki/Roots_blowerhttp://en.wikipedia.org/wiki/Roots_blowerhttp://en.wikipedia.org/wiki/Roots_blowerhttp://en.wikipedia.org/wiki/Hot_bulb_enginehttp://en.wikipedia.org/wiki/Crankcasehttp://en.wikipedia.org/wiki/Piston


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Reed inlet valveACoxBabe Bee 0.049 cubic inch (0.8 cubic cm) reedvalve engine, disassembled, uses glow plug ignition. Themass is 64 grams.

The reed valve is a simple but highly effective form

ofcheck valvecommonly fitted in the intake tract ofthe piston-controlled port. They allow asymmetric intake

of the fuel charge, improving power and economy, while

widening the power band. They are widely used in ATVs

and marine outboard engines.

Rotary inlet valveThe intake pathway is opened and closed by a rotating member. A familiar type sometimes seenon small motorcycles is a slotted disk attached to thecrankshaftwhich covers and uncovers anopening in the end of the crankcase, allowing charge to enter during one portion of the cycle.

Another form of rotary inlet valve used on two-stroke engines employs two cylindrical members

with suitable cutouts arranged to rotate one within the other - the inlet pipe having passage to the

crankcase only when the two cutouts coincide. The crankshaft itself may form one of the

members, as in most glow plug model engines. In another embodiment, the crank disc is arranged

to be a close-clearance fit in the crankcase, and is provided with a cutout which lines up with an

inlet passage in the crankcase wall at the appropriate time, as in theVespamotor scooter.The advantage of arotary valveis it enables the two-stroke engine's intake timing to beasymmetrical, which is not possible with piston port type engines. The piston port type engine's

intake timing opens and closes before and after top dead center at the same crank angle, making it

symmetrical, whereas the rotary valve allows the opening to begin earlier and close earlier.Rotary valve engines can be tailored to deliver power over a wider speed range or higher power

over a narrower speed range than either piston port or reed valve engine. Where a portion of therotary valve is a portion of the crankcase itself, it is particularly important that no wear is allowed

to take place.

Crossflow-scavengedIn a crossflow engine, the transfer and exhaust ports are

on opposite sides of the cylinder, and a deflector on the

top of the piston directs the fresh intake charge into theupper part of the cylinder, pushing the residual exhaust

gas down the other side of the deflector and out theexhaust port.The deflector increases the piston's weightand exposed surface area, and also makes it difficult toachieve an efficient combustion chamber shape. This

design has been largely superseded by the loop

scavenging method (below), although for smaller orslower engines, the crossflow-scavenged design can be

an acceptable approach.
http://en.wikipedia.org/wiki/Cox_Modelshttp://en.wikipedia.org/wiki/Cox_Modelshttp://en.wikipedia.org/wiki/Cox_Modelshttp://en.wikipedia.org/wiki/Check_valvehttp://en.wikipedia.org/wiki/Check_valvehttp://en.wikipedia.org/wiki/Check_valvehttp://en.wikipedia.org/wiki/Crankshafthttp://en.wikipedia.org/wiki/Crankshafthttp://en.wikipedia.org/wiki/Crankshafthttp://en.wikipedia.org/wiki/Vespahttp://en.wikipedia.org/wiki/Vespahttp://en.wikipedia.org/wiki/Vespahttp://en.wikipedia.org/wiki/Rotary_valvehttp://en.wikipedia.org/wiki/Rotary_valvehttp://en.wikipedia.org/wiki/Rotary_valvehttp://en.wikipedia.org/wiki/File:Old_Cox_Babe_Bee_engine_dissasembled.JPGhttp://en.wikipedia.org/wiki/File:Two-stroke_deflector_piston_(Autocar_Handbook,_13th_ed,_1935).jpghttp://en.wikipedia.org/wiki/Rotary_valvehttp://en.wikipedia.org/wiki/Vespahttp://en.wikipedia.org/wiki/Crankshafthttp://en.wikipedia.org/wiki/Check_valvehttp://en.wikipedia.org/wiki/Cox_Modelshttp://en.wikipedia.org/wiki/File:Old_Cox_Babe_Bee_engine_dissasembled.JPGhttp://en.wikipedia.org/wiki/File:Two-stroke_deflector_piston_(Autocar_Handbook,_13th_ed,_1935).jpg


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Loop-scavenged

The Two-stroke cycle

A: intake/scavenging

B: Exhaust

C: Compression

D: Expansion(power)

This method of scavenging uses carefully shaped and positioned transfer ports to direct

the flow of fresh mixture toward the combustion chamber as it enters the cylinder. The

fuel/air mixture strikes thecylinder head, then follows the curvature of the combustionchamber, and then is deflected downward.

This not only prevents the fuel/air mixture from traveling directly out the exhaust port,

but also creates a swirling turbulence which improves combustion efficiency, power and

economy. Usually, a piston deflector is not required, so this approach has a distinctadvantage over the cross-flow scheme (above).

Often referred to as "Schnuerle" (or "Schnrl") loop scavenging after the German

inventor of an early form in the mid 1920s, it became widely adopted in that country

during the 1930s and spread further afield afterWorld War II.Loop scavenging is the most common type of fuel/air mixture transfer used on modern

two-stroke engines. Suzuki was one of the first manufacturers outside of Europe to adoptloop-scavenged two-stroke engines. This operational feature was used in conjunction

with the expansion chamber exhaust developed by German motorcycle manufacturer, MZ

and Walter Kaaden.

Loop scavenging, disc valves and expansion chambers worked in a highly coordinated

way to significantly increase the power output of two-stroke engines, particularly fromthe Japanese manufacturers Suzuki, Yamaha and Kawasaki. Suzuki and Yamaha enjoyed

success in grand Prix motorcycle racing in the 1960s due in no small way to the increasedpower afforded by loop scavenging.An additional benefit of loop scavenging was the piston could be made nearly flat or

slightly dome shaped, which allowed the piston to be appreciably lighter and stronger,

and consequently to tolerate higher engine speeds. The "flat top" piston also has better
http://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T.svghttp://en.wikipedia.org/wiki/Cylinder_headhttp://en.wikipedia.org/wiki/Cylinder_headhttp://en.wikipedia.org/wiki/Cylinder_headhttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T.svghttp://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T.svghttp://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T.svghttp://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T.svghttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/Cylinder_head


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thermal properties and is less prone to uneven heating, expansion, piston seizures,

dimensional changes and compression losses.SAAB built 750 and 850 cc 3-cylinder engines based on a DKW design that proved

reasonably successful employing loop charging. The original SAAB 92 had a two-

cylinder engine of comparatively low efficiency. At cruising speed, reflected wave

exhaust port blocking occurred at too low a frequency. Using the asymmetric three-portexhaust manifold employed in the identical DKW engine improved fuel economy.

The 750 cc standard engine produced 36 to 42 hp, depending on the model year. The

Monte Carlo Rally variant, 750 cc (with a filled crankshaft for higher base compression),generated 65 hp. An 850 cc version was available in the 1966 SAAB Sport (a standard

trim model in comparison to the deluxe trim of the Monte Carlo). Base compression

comprises a portion of the overall compression ratio of a two-stroke engine.

Uniflow-scavenged

The Uniflow Two-stroke cycle

A: Intake(effective scavenging 140-250)

B: Exhaust

C: Compression

D: Expansion(power)

In a uniflow engine, the mixture, or air in the case of a diesel, enters at one endof the cylinder controlled by the piston and the exhaust exits at the other endcontrolled by an exhaust valve or piston. The scavenging gas-flow is therefore inone direction only, hence the name uniflow. The valved arrangement is commonin diesel locomotives (Electro-Motive Diesel) and large marine two-strokeengines (Wrtsil). Ported types are represented by the opposed piston design inwhich there are two pistons in each cylinder, working in opposite directions suchas the Junkers Jumo and Napier Deltic. The once-popular split-single design fallsinto this class, being effectively a folded uniflow. With advanced angle exhausttiming, uniflow engines can be supercharged with a crankshaft-driven (piston orRoots) blower.
http://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T_unidirezionale.svghttp://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T_unidirezionale.svghttp://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T_unidirezionale.svghttp://en.wikipedia.org/wiki/File:Ciclo_del_motore_2T_unidirezionale.svg


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Power valve systems

Many modern two-stroke engines employ a power valve system. The valves are normally

in or around the exhaust ports. They work in one of two ways: either they alter theexhaust port by closing off the top part of the port, which alters port timing, such as Ski-

doo R.A.V.E, Yamaha YPVS, Honda RC-Valve, Cagiva C.T.S. or Suzuki AETCsystems, or by altering the volume of the exhaust, which changes the resonant frequencyof the expansion chamber, such as the Honda V-TACS system. The result is an engine

with better low-speed power without sacrificing high-speed power.

Direct injection

Direct injection has considerable advantages in two-stroke engines, eliminating some of

the waste and pollution caused by carbureted two-strokes where a proportion of the

fuel/air mixture entering the cylinder goes directly out, unburned, through the exhaust

port. Two systems are in use, low-pressure air-assisted injection, and high pressureinjection.

Since the fuel does not pass through the crankcase, a separate source of lubrication isneeded.

Lubrication

Most small petrol two-stroke engines cannot be lubricated by oil contained in their

crankcase and sump, since thecrankcaseis already being used to pump fuel-air mixtureinto the cylinder. Traditionally, the moving parts (both rotating crankshaft and sliding

piston) were lubricated by a premixed fuel-oil mixture (at a ratio between 16:1 and

100:1). As late as the 1960s, petrol stations would often have a separate pump to deliversuch a premix fuel to motorcycles. Even then, in many cases, the rider would carry a

bottle of their own two-stroke oil. Taking care to close the fuel-tap first, he or she wouldmeter in a little oil (using the cap of the bottle) and then put in the petrol, this action

mixing the two liquids.

Modern two-stroke engines pump lubrication from a separate tank of oil. This is still atotal-loss system with the oil being burnt the same as in the older system, but at a lower

and more economical rate. It is also cleaner, reducing the problem of oil-fouling of the

spark-plugs and coke formation in the cylinder and the exhaust. Almost the only motors

still using premix are hand-held two-stroke devices, such as chainsaws (which mustoperate in any attitude) and the majority of model engines.

All two-stroke engines running on a petrol/oil mix will suffer oil starvation if forced torotate at speed with the throttle closed, e.g. motorcycles descending long hills andperhaps when decelerating gradually from high speed by changing down through the

gears. Two-stroke cars (such as those that were popular in Eastern Europe in mid-20th

century) were in particular danger and were usually fitted withfreewheelmechanisms inthepowertrain, allowing the engine to idle when the throttle was closed, requiring the useof the brakes in all slowing situations.


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Large two-stroke engines, including diesels, normally use a sump lubrication system

similar to four-stroke engines. The cylinder must still be pressurized, but this is not donefrom the crankcase, but by an ancillary supercharger.

Two-stroke reversibility

For the purpose of this discussion, it is convenient to think in motorcycle terms, where

the exhaust pipe faces into the cooling air stream, and the crankshaft commonly spins in

the same axis and direction as do the wheels i.e. "forward". Some of the considerationsdiscussed here apply to four-stroke engines (which cannot reverse their direction of

rotation without considerable modification), almost all of which spin forward, too.

Regular gasoline two-stroke engines will run backwards for short periods and under light

load with little problem, and this has been used to provide a reversing facility

inmicrocars, such as theMesserschmitt KR200, that lacked reverse gearing. Where thevehicle has electric starting, the motor will be turned off and restarted backwards by

turning the key in the opposite direction. Two-strokegolf cartshave used a similar kind

of system. Traditional flywheel magnetos (using contact-breaker points, but no externalcoil) worked equally well in reverse because the cam controlling the points is

symmetrical, breaking contact beforeTDCequally well whether running forwards orbackwards. Reed-valve engines will run backwards just as well as piston-controlled

porting, though rotary valve engines have asymmetrical inlet timing and will not run very

well.There are serious disadvantages to running any engine backwards under load for any

length of time, and some of these reasons are general, applying equally to both two-stroke

and four-stroke engines. Some of this disadvantage is intrinsic, unavoidable even in the

case of a complete re-design. The problem comes about because in "forwards" runningthe major thrust face of the piston is on the back face of the cylinder which, in a two-

stroke particularly, is the coolest and best lubricated part. The forward face of the pistonis less well-suited to be the major thrust face since it covers and uncovers the exhaust portin the cylinder, the hottest part of the engine, where piston lubrication is at its most

marginal. The front face of the piston is also more vulnerable since the exhaust port, the

largest in the engine, is in the front wall of the cylinder. Piston skirts and rings risk being

extruded into this port, so it is always better to have them pressing hardest on the backwall (where there are only the transfer ports) and there is good support. In some engines,

thesmall endis offset to reduce thrust in the intended rotational direction and the forwardface of the piston has been made thinner and lighter to compensate - but when running

backwards, this weaker forward face suffers increased mechanical stress it was notdesigned to resist.

Large two-stroke ship diesels are sometimes made to be reversible. Like four-stroke shipengines (some of which are also reversible) they use mechanically-operated valves, sorequire additional camshaft mechanisms.

On top of other considerations, the oil-pump of a modern two-stroke may not work in

reverse, in which case the engine will suffer oil starvation within a short time. Running amotorcycle engine backwards is relatively easy to initiate, and in rare cases, can be

triggered by a back-fire. It is not advisable.


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Model airplane engines with reed-valves can be mounted in either tractor

orpusherconfiguration without needing to change the propeller. These motors arecompression ignition, so there are no ignition timing issues and little difference between

running forward and running backward.

A Running Two Stroke Engine:A two-stroke in its purest form is extremely simple in construction and operation, as it

only has three primary moving parts (the piston, connecting rod, and crankshaft).However, the two-stroke cycle can be difficult for some to visualize at first because

certain phases of the cycle occur simultaneously, causing it to be hard to tell when one

part of the cycle ends and another begins.

Several different varieties of two-strokes have been developed over the years, and each

type has its own set of advantages and disadvantages. The subject of the animated GIF

(and this dissertation) is known as a case-reed type because induction is controlled by areed valve mounted in the side of the crankcase.

The easiest way to visualize two-stroke operation is to follow the flow of gases through

the engine starting at the air inlet. In this case, the cycle would begin at approximatelymid-stroke when the piston is rising, and has covered the transfer port openings:

As the piston moves upward, a vacuum is created beneath the piston in the enclosedvolume of the crankcase. Air flows through the reed valve and carburetor to fill the

vacuum created in the crankcase. For the purposes of discussion, the intake phase is

completed when the piston reaches the top of the stroke (in reality, mixture continues to

flow into the crankcase even when the piston is on its way back down due to the inertia ofthe fuel mixture, especially at high RPM):

During the down stroke, the falling piston creates a positive pressure in the crankcasewhich causes the reed valve to close. The mixture in the crankcase is compressed until

the piston uncovers the transfer port openings, at which point the mixture flows up into

the cylinder. The engine depicted here is known as a loop-scavenged two-stroke becausethe incoming mixture describes a circular path as shown in the picture below. What is not

readily apparent in the picture is that the primary portion of the mixture is directed

toward the cylinder wall opposite the exhaust port (this reduces the amount of mixture

that escapes out the open exhaust port, also known as short-circuiting):

Mixture transfer continues until the piston once again rises high enough to shut off thetransfer ports (which is where we started this discussion). Let's fast-forward about 25

degrees of crank rotation to the point where the exhaust port is covered by the piston. Thetrapped mixture is now compressed by the upward moving piston (at the same time that a

new charge is being drawn into the crankcase down below):

Somewhat before the piston reaches the top of the stroke (approximately 30 degrees of

crank rotation before top-dead-center), the sparkplug ignites the mixture. This event is


15/23

timed such that the burning mixture reaches peak pressure slightly after top dead center.

The expanding mixture drives the piston downward until it begins to uncover the exhaustport. The majority of the pressure in the cylinder is released within a few degrees of

crank rotation after the port begins to open:

Residual exhaust gases are pushed out the exhaust port by the new mixture entering thecylinder from the transfer ports.

That completes the chain of events for the basic two-stroke cycle. The discussion is notcomplete. The animated demonstration has an added device commonly known as an

expansion chamber attached to the exhaust port. The expansion chamber (an improperly

named device) utilizes sonic energy contained in the initial sharp pulse of exhaust gasexiting the cylinder to supercharge the cylinder with fresh mixture. This device is also

known as a tuned exhaust.

Picking up the discussion at the point shown by the exhaust blowdown picture above, an

extremely high energy pulse of exhaust gas enters the header pipe when the piston beginsto open the exhaust port:

The sonic compression wave resulting from this abrupt release of cylinder pressure

travels down the exhaust pipe until it reaches the beginning of the divergent cone, or

diffuser, of the expansion chamber. From the perspective of the sound waves reachingthis junction, the diffuser appears almost like an open-ended tube in that part of the

energy of the pulse is reflected back up the pipe, except with an inverted sign (a

rarefaction, or vacuum pulse is returned). The angle of the walls of the cone determine

the magnitude of the returned negative pressure, and the length of the cone defines theduration of the returning waves:

The negative pressure assists the mixture coming up through the transfer ports, and

actually draws some of the mixture out into the exhaust header. Meanwhile, the originalpressure pulse is still making its way down the expansion chamber, although a

considerable portion of its energy was given up in creating the negative pressure waves.

The convergent section of the chamber appears like a closed-end tube to the pressurepulse, and as such causes another series of waves to be reflected back up the pipe, except

these waves are the same sign as the original (a compression, or pressure wave is

returned). Notice that this cone has a sharper angle than the diffuser, so that a largerproportion of energy is extracted from the already weak pressure pulse:

This pulse is timed to reach the exhaust port after the transfer ports close, but before the

exhaust port closes. The returning compression wave pushes the mixture drawn into theheader by the negative pressure wave back into the cylinder, thus supercharging (a bigger

charge than normal) the engine. The straight section of pipe between the two cones exists

to ensure that the positive waves reaches the exhaust port at the correct time.Since this device uses sonic energy to achieve supercharging, it is regulated by the speed

of sound in the hot exhaust gas, the dimensions of the different sections of the exhaust

system, and the port durations of the engine. Because of this, it is only effective for a very


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narrow RPM range. This explains why two-stroke motorcycles equipped with expansion

chambers have such vicious powerbands (especially in the old days before variableexhaust port timing existed). With the design illustrated here (i.e. a single divergent stage

and a single convergent stage), the powerband of the engine will be akin to a 'light switch'

- once the expansion chamber goes into resonance, there will be a HUGE, almost

instantaneous increase in power. The powerband can be softened somewhat by reducingthe angles on the cones, but this is simply due to a lowerdegree of supercharging. Inorder to get the best of both worlds (a large power increase and a wide powerband), the

cones should consist of several sections, with a different anglefor each section. Properdesign of even a simple expansion chamber is somewhat of a black art, even though

formulae exist that will get you in the ballpark (there is quite a bit more to this than

simply choosing the appropriate angles and lengths based on sonic velocity - everythingabout the pipe comes into play, including the headpipe diameter and length, and the

tailpipe ('stinger') diameter and length). Design of a multi-stage expansion chamber

becomes incredibly difficult - it basically comes down to the old 'cut and try' approach in

the end. This of course is not even considering whether or not the exhaust and transfer

port timings and outlet areas have been optimized for expansion chamber use.

Parts of a 2 Stroke EngineBasicsLike other types of engines, a two-stroke engine has a crankcase that surrounds andprotects all other parts of the engine. Inside, it has a crankshaft, connecting rod andsingle piston. It's also got an intake port, a reed valve, an exhaust port, and acylinder---all in addition to the combustion chamber, where the power is producedthat moves whatever the engine is powering.

CrankshaftThe crankshaft in a two-stroke engine rotates, moving the piston by means of theconnecting rod. These three parts are the only moving parts in a two-stroke engine.

All power produced is a direct result of the action of these three moving parts.

Connecting RodThe connecting rod is connected to the crankshaft at one end, and to the piston at theother. It translates the movement of the crankshaft so that the piston is moved upand down.

PistonThe piston is moved up and down inside the cylinder by the crankshaft, which isconnected to it via the connecting rod. A vacuum is formed as it takes its upwardstroke, drawing air and fuel down through the reed valve. When the piston reaches

the top, the spark plug then lights the air/fuel mixture, burning it and sending thepiston back down. On the downward stroke, the reed valve gets closed because of theincreased pressure of the fuel and air mixture within, which is being compressed.New fuel and air travel via the intake port into the cylinder, ready to be burnt. Theexhaust is expelled through the exhaust port, and an unpleasant side effect is that itusually takes some of the unburned fuel mixture with it.Efficiency


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A two-stroke engine fires once every revolution, unlike a four-stroke engine.Theoretically, this means that two-stroke engines should be more powerful thanfour-stroke engines with the same displacement. However, because some unburnedfuel invariably escapes during the combustion process, they are not as efficient asthey could be.VariationsDifferent two-stroke engines may have different means of transferring exhaust andunburned fuel and air through them, using various ports and valves. This process isreferred to as "scavenge phase," and you can find more information about the mainscavenge phase types by following the "Outdoor Power Equipment" link in References.

Two-stroke BasicsThis is what a two-strokeengine looks like:You find two-stroke engines insuch devices aschainsawsand jet skis because

two-stroke engines have threeimportant advantages overfour-stroke engines:Two-stroke engines do nothave valves, which simplifiestheir construction and lowerstheir weight.Two-stroke engines fire onceevery revolution, while four-stroke engines fire once everyother revolution. This gives

two-stroke engines asignificant power boost.Two-stroke engines can workin any orientation, which canbe important in something likea chainsaw. A standard four-stroke engine may haveproblems with oil flow unlessit is upright, and solving thisproblem can add complexityto the engine.

These advantages make two-stroke engines lighter, simplerand less expensive to

manufacture. Two-stroke

engines also have the potential topack about twice the power into

the same space because there are

twice as many power strokes per
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revolution. The combination of light weight and twice the power gives two-stroke

engines a greatpower-to-weight ratiocompared to many four-stroke engine designs.You don't normally see two-stroke engines in cars, however. That's because two-stroke

engines have a couple of significant disadvantages that will make more sense once we

look at how it operates.

The Two-stroke CycleThe following animation shows a two-stroke

engine in action. You can compare this animation

to the animations in thecar engineanddieselenginearticles to see the differences. The biggestdifference to notice when comparing figures is

that thespark-plug fires once everyrevolutionin a two-stroke engine.

This figure shows a typicalcross flowdesign. You

can see that two-stroke engines are ingenious littledevices that overlap operations in order to reduce the

part count.

Sparks FlyYou can understand a two-stroke engine by

watching each part of the cycle. Start with the

point where the spark plugfires. Fuel and air inthe cylinder have been compressed, and when the

spark plug fires the mixture ignites. The

resultingexplosion drives

thepistondownward. Note that as the pistonmoves downward, it is compressing the air/fuelmixture in the crankcase. As the piston

approaches the bottom of its stroke, theexhaustportis uncovered. Thepressurein the cylinderdrives most of the exhaust gases out of cylinder,

as shown here:

Fuel IntakeAs the piston finally bottoms out, theintake portis uncovered. The piston's movement

haspressurizedthe mixture in the crankcase, so it rushes into thecylinder,displacingthe remaining exhaust gases and filling the cylinder with a freshcharge of fuel, as shown here:

Note that in many two-stroke engines that use a cross-flow design, the piston is shaped sothat the incoming fuel mixture doesn't simply flow right over the top of the piston and out

the exhaust port.
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The Compression StrokeNow the momentum in the crankshaft starts driving

the piston back toward the spark plug for

thecompression stroke. As the air/fuel mixture inthe piston is compressed, avacuumis created in the

crankcase. This vacuum opens thereed valveandsucks air/fuel/oil in from thecarburetor.Once the piston makes it to the end of the

compression stroke, the spark plug fires again to

repeat the cycle. It's called a two-stoke engine

because there is acompression strokeand thenacombustion stroke. In a four-stroke engine,there are separate intake, compression, combustionand exhaust strokes.

You can see that the piston is really doing three

different things in a two-stroke engine:

On one side of the piston is thecombustionchamber, where the piston is compressing theair/fuel mixture and capturing the energy released by

the ignition of the fuel.

On the other side of the piston is thecrankcase,where the piston is creating a vacuum to suck in

air/fuel from the carburetor through the reed valveand then pressurizing the crankcase so that air/fuel is

forced into the combustion chamber.

Meanwhile, the sides of the piston are acting

likevalves, covering and uncovering the intake and

exhaust ports drilled into the side of the cylinder wall.It's really pretty neat to see the piston doing so many different things! That's what makes

two-stroke engines so simple and lightweight.

If you have ever used a two-stroke engine, you know that you have to mix specialtwo-stroke oilin with the gasoline. Now that you understand the two-stroke cycle you cansee why. In a four-stroke engine, the crankcase is completely separate from thecombustion chamber, so you can fill the crankcase with heavy oil to lubricate the

crankshaft bearings, the bearings on either end of the piston's connecting rod and the

cylinder wall. In a two-stroke engine, on the other hand, the crankcase is serving as

apressurization chamberto force air/fuel into the cylinder, so it can't hold a thickoil. Instead, you mix oil in with the gas to lubricate the crankshaft, connecting rod and

cylinder walls. If you forget to mix in the oil, the engine isn't going to last very long!

Disadvantages of the Two-stroke

You can now see that two-stroke engines have two important advantages over four-stroke

engines: They are simpler and lighter, and they produce about twice as much power. So

why do cars and trucks usefour-stroke engines? There are four main reasons:
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Two-stroke engines don't last nearly as long as four-stroke engines. The lack of a

dedicated lubrication system means that the parts of a two-stroke engine wear a lot faster.

Two-stroke oil is expensive, and you need about 4 ounces of it per gallon ofgas. Youwould burn about a gallon of oil every 1,000 miles if you used a two-stroke engine in a

car.

Two-stroke engines do not use fuel efficiently, so you would get fewer miles per gallon.Two-stroke engines produce a lot of pollution -- so much, in fact, that it is likely that you

won't see them around too much longer. Thepollutioncomes from two sources. Thefirst is the combustion of the oil. The oil makes all two-stroke engines smoky to some

extent, and a badly worn two-stroke engine can emit huge clouds of oily smoke. The

second reason is less obvious but can be seen in the following figure:Each time a new charge of air/fuel is loaded into the combustion chamber, part of

itleaks outthrough the exhaust port. That's why you see a sheen of oil around any two-stroke boat motor. The leaking hydrocarbons from the fresh fuel combined with the

leaking oil is a real mess for the environment.

These disadvantages mean that two-stroke engines are used only in applications where

the motor is not used very often and a fantastic power-to-weight ratio is important.In the meantime, manufacturers have been working to shrink and lighten four-stroke

engines, and you can see that research coming to market in a variety of new marine andlawn-care products.

Automotive batteryAnautomotive batteryis a typeofrechargeable batterythat supplies electric

energy to anautomobile.Usually this refers toanSLI battery(starting, lighting, ignition) topower thestarter motor, the lights, andtheignition systemof a vehiclesengine.

Automotive SLI batteries are usuallylead-acidtype, and are made of sixgalvaniccellsinseriesto provide a 12voltsystem. Eachcell provides 2.1 volts for a total of 12.6 volt at

full charge. Heavy vehicles such as highway

trucks or tractors, often equipped withdiesel

engines, may have two batteries in series for a 24volt system, or may have parallel strings of batteries.

Lead-acid batteries are made up of plates ofleadand separate plates oflead dioxide,which are submerged into anelectrolytesolution of about 35%sulfuric acidand65%water.This causes achemical reactionthat releaseselectrons, allowing them to flowthroughconductorsto produceelectricity. As the batterydischarges, the acid of theelectrolyte reacts with the materials of the plates, changing their surface tolead sulfate.When the battery isrecharged, the chemical reaction is reversed: the lead sulfate reforms
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into lead oxide and lead. With the plates restored to their original condition, the process

may now be repeated.

Battery recyclingof automotive batteries reduces resources required for manufacture ofnew batteries and diverts toxic lead from landfills or improper disposal.

Storage

Batteries last longer when stored in a charged state. Leaving an automotive batterydischarged will shorten its life, or make it unusable if left for a long time (usually several

years);sulfationeventually becomes irreversible by normal charging. Batteries instorage may be monitored and periodically charged, or attached to a "float" charger to

retain their capacity. Batteries are prepared for storage by charging and cleaning deposits

from the posts. Batteries are stored in a cool, dry environment for best results since hightemperatures increase the self discharge rate and plate corrosion.

Changing a batteryWhen changing a battery, battery manufacturers recommend disconnecting the negativeground connection first to prevent accidental short-circuits between the battery terminal

and the vehicle frame. Conversely the positive cable is connected first. A study by the

National Highway Traffic Safety Association estimated that in 1994 more than 2000people were injured in the United States while working with automobile batteries.

The majority of automotive lead-acid batteries are filled with the appropriate electrolyte

solution at the manufacturing plant, and shipped to the retailers ready to sell. Decadesago, this was not the case. The retailer filled the battery, usually at the time of purchase,

and charged the battery. This was a time-consuming and potentially dangerous process.

Care had to be taken when filling the battery withacid, as acids are highly corrosive andcan damage eyes,skinand mucous membranes. Fortunately, this is less of a problemthese days, and the need to fill a battery with acid usually only arises when purchasing a

motorcycle or ATV battery.

Charge and dischargeIn normal automotive service the vehicle's charging system powers the vehicle's electricalsystems and restores charge used from the battery during engine cranking. When

installing a new battery or recharging a battery that has been accidentally discharged

completely, one of several different methods can be used to charge it. The most gentle of

these is calledtrickle charging. Other methods include slow-charging and quick-charging, the latter being the harshest.

The voltage regulator of the charge system does not measure the relative currents

charging the battery and for powering the car's loads. The charge system essentiallyprovides a fixed voltage of typically 13.8 to 14.4 V (Volt), adjusted to ambient

temperature, unless the alternator is at its current limit. A discharged battery draws a highcharge current of typically 20 to 40 A (Ampere). As the battery gets charged the charge

current typically decreases to 25 A. A high load results when multiple high-powersystems such as ignition, radiator fan, heater blowers, lights and entertainment system are

running. In this case, the battery voltage will begin to decrease unless the engine is

running at a higher rpm and the alternator/generator is delivering at least enough currentto power the load.
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Some manufacturers include a built-inhydrometerto show the state of charge of thebattery, a transparent tube with a float immersed in the electrolyte visible through awindow. When the battery is charged, the specific gravity of the electrolyte increases

(since all the sulfate ions are in the electrolyte, not combined with the plates), and the

colored top of the float is visible in the window. When the battery is discharged, or the

electrolyte level is too low, the float sinks and the window appears yellow (or black). Thebuilt-in hydrometer only checks the state of charge of one cell and will not show faults in

the other cells. In a non-sealed battery each of the cells can be checked with a portable or

hand-held hydrometer.

In emergencies a vehicle can bejump startedby thebattery of another vehicle or by a portable battery

booster.

Whenever the car's charge system is inadequate to fully

charge the battery, a battery charger can be used.Simple chargers do not regulate the charge current, and

the user needs to stop the process or lower the chargecurrent to prevent excessive gassing of the battery.

More elaborate chargers, in particular those

implementing the3-step chargeprofile, also referred to asIUoU, charge the battery fullyand safely in a short time without requiring user intervention.Desulfatingchargers arealso commercially available for charging all types of lead-acid batteries.
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1. Engine Rotate The Motor opp. Side with Help of Belt.

2.Opp. Rotation Generate The Electric Power.3.Electric Power On The CFL.

4.As U Know Engine have inbuilt Charger.

5.The Charger Charge The Battery.

6.And When the Engine Was Start CFL Work With The Help of Motor.

7.And When The Engine Off CFL Work With The Help of Battery.

8.Dont Forget When The Engine Was on Start the Switch No.2 And off TheSwitch No. 1.

9.And When The Engine Was off Start The Switch No.1 And Off The

Switch No. 2.

generation of electric power from a two stock engine

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