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INTRODUCTION

Chemistry has played a decisive role in the evolution of the engines especiallyin internal combustion. The chemistry has been charged with investigatingwhat would be the best fuel to mae the engine more e!icient by creatingdi!erent types of molecular combinations. In chemical engineering as well as

help create better engines also used some especially in the food industry orprocessing of raw materials. The engine is particularly important in thetransformation of raw materials such as sugar cane or polyurethane.

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- To investigate the application of motors in chemical engineering- To now the importance of motors in the industry.

 '(()IC'TION O* +OTOR& IN C,$+IC') $N-IN$$RIN-

Combustion or burning is the seuence of e/othermic chemical reactions

between a fuel and an o/idant accompanied by the production of heat and

conversion of chemical species. The release of heat can result in the

production of light in the form of either glowingor a 0ame. *uels of interest

often include organic compounds 1especially hydrocarbons2 in

the gas3 liuid or solid phase.In a complete combustion reaction3 a compound reacts with an o/idi4ingelement3 such as o/ygen or 0uorine3 and the products are compounds of eachelement in the fuel with the o/idi4ing element. *or e/ample5

C,6 7 8 O8 9 CO8 7 8 ,8O 7 energy

 ' simple e/ample can be seen in the combustion of hydrogen and o/ygen3which is a commonly used reaction in rocet engines5

8 ,8 7 O8 9 8 ,8O1g2 7 heat

The result is water vapor.

Complete combustion is almost impossible to achieve. In reality3 as actualcombustion reactions come to euilibrium3 a wide variety of ma:or and minor

species will be present such as carbon mono/ide and pure carbon 1soot orash2. 'dditionally3 any combustion in atmospheric air3 which is ;<percent nitrogen3 will also create several forms of nitrogen o/ides.

Complete combustion is almost impossible to achieve. In reality3 as actual

combustion reactions come to euilibrium3 a wide variety of ma:or and minor

species will be present such as carbon mono/ide and pure carbon 1soot or

ash2. 'dditionally3 any combustion in atmospheric air3 which is ;<

percent nitrogen3 will also create several forms of nitrogen o/ides.

In complete combustion3 the reactant burns in o/ygen3 producing a limited

number of products. =hen a hydrocarbon burns in o/ygen3 the reaction willonly yield carbon dio/ide and water. =hen elements are burned3 the productsare primarily the most common o/ides. Carbon will yield carbon dio/ide3

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nitrogen will yield nitrogen dio/ide3 sulfur will yield sulfur dio/ide3 and ironwill yield iron1III2 o/ide.

Combustion is not necessarily favorable to the ma/imum degree of o/idationand it can be temperature>dependent. *or e/ample3 sulfur trio/ide is notproduced uantitatively in combustion of sulfur. Nitrogen o/ides start to form

above 83<?? @* 1A3B6? @C2 and more nitrogen o/ides are produced at highertemperatures. "elow this temperature3 molecular nitrogen 1N82 is favored. It isalso a function of o/ygen e/cess. 

In most industrial applications and in res3 air is the source of o/ygen 1O82. Inair3 each mole of o/ygen is mi/ed with appro/imately .;E mole of nitrogen.Nitrogen does not tae part in combustion3 but at high temperatures3 somenitrogen will be converted to NOx3 usually between AF and ?.??8F 18ppm2. *urthermore3 when there is any incomplete combustion3 some of carbonis converted tocarbon mono/ide. ' more complete set of euations forcombustion of methane in air is therefore5

C,6 7 8 O8 9 CO8 7 8 ,8O

8 C,6 7 O8 9 8 CO 7 6 ,8O

N8 7 O8 9 8 NO

N8 7 8 O8 9 8 NO8

Incomplete combustion will only occur when there is not enough o/ygen toallow the fuel to react completely to produce carbon dio/ide and water. It alsohappens when the combustion is uenched by a heat sin such as a solidsurface or 0ame trap.

*or most fuels3 such as diesel oil3 coal or wood3 pyrolysis occurs beforecombustion. In incomplete combustion3 products of pyrolysis remain unburntand contaminate the smoe with no/ious particulate matter and gases.(artially o/idi4ed compounds are also a concernG partial o/idation of ethanolcan produce harmful acetaldehyde3 and carbon can produce to/ic carbonmono/ide.

The uality of combustion can be improved by design of combustion devices3such as burners and internal combustion engines. *urther improvements areachievable by catalytic after>burning devices 1such as catalytic converters2 orby the simple partial return of the e/haust gases into the combustion process.&uch devices are reuired by environmental legislation for cars in mostcountries3 and may be necessary in large combustion devices3 such as thermalpower stations3 to reach legal emission standards.

The degree of combustion can be measured and analy4ed3 with testeuipment. ,%'C contractors3 remen and engineers use combustionanaly4ers to test the e!iciency of a burner during the combustion process. In

addition3 the e!iciency of an internal combustion engine can be measured inthis way3 and some states and local municipalities are using combustionanalysis to dene and rate the e!iciency of vehicles on the road today

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-enerally3 the chemical euation for stoichiometric burning of hydrocarbon ino/ygen is

*or e/ample3 the burning of propane is

-enerally3 the chemical euation for stoichiometric incompletecombustion of hydrocarbon in o/ygen is as follows5

*or e/ample3 the incomplete combustion of propane is5

The simple word euation for the combustion of a hydrocarbon in

o/ygen is5

If the combustion taes place using air as the o/ygen source3the nitrogen can be added to the euation3as and although itdoes not react3 to show the composition of the 0ue gas5

*or e/ample3 the burning of propane is5

The simple word euation for this type of combustion ishydrocarbon in air5

Nitrogen may also o/idi4e when there is an e/cess of o/ygen. The reaction isthermodynamically favored only at high temperatures.Diesel engines are runwith an e/cess of o/ygen to combust small particles that tend to form withonly a stoichiometric amount of o/ygen3 necessarily producing nitrogen o/ideemissions. "oth the United &tates and $uropean Union have limits to nitrogen

o/ide emissions3 which necessitate the use of a special catalytic converter ortreatment of the e/haust with urea 1see Diesel e/haust 0uid2.

The act of combustion consists of three relatively distinct but overlappingphases5

(reheating phase3 when the unburned fuel is heated up to its 0ash pointand then re point. *lammable gases start being evolved in a processsimilar to dry distillation.

Distillation phase or gaseous phase3 when the mi/ of evolved 0ammablegases with o/ygen is ignited. $nergy is produced in the form of heat and

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light. *lames are often visible. ,eat transfer from the combustion to thesolid maintains the evolution of 0ammable vapours.

Charcoal phase or solid phase3 when the output of 0ammable gases fromthe material is too low for persistent presence of 0ame andthe charred fuel does not burn rapidly and :ust glows and lateronly smoulders.

 'ssuming perfect combustion conditions3 such as complete combustionunder adiabaticconditions 1i.e.3 no heat loss or gain23 the adiabatic combustiontemperature can be determined. The formula that yields this temperature is

based on the rst law of thermodynamics and taes note of the fact thatthe heat of combustion is used entirely for heating the fuel3 the combustion airor o/ygen3 and the combustion product gases 1commonly referred to asthe fue gas2.

In the case of fossil fuels burnt in air3 the combustion temperature depends onall of the following5

the heating valueG

the stoichiometric air to fuel ratio  G

the specic heat capacity of fuel and airG

the air and fuel inlet temperatures.

The adiabatic combustion temperature 1also nown as the adiabatic fametemperature2 increases for higher heating values and inlet air and fueltemperatures and for stoichiometric air ratios approaching one.

+ost commonly3 the adiabatic combustion temperatures for coals arearound 838?? @C 13HH8 @*2 1for inlet air and fuel at ambient temperatures andfor 23 around 83AB? @C 13H?8 @*2 for oil and 83???@C 13E8 @*2 for natural gas.

In industrial red heaters3 power station steam generators3 and large gas>redturbines3 the more common way of e/pressing the usage of more than thestoichiometric combustion air is percent excess combustion air . *or e/ample3

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e/cess combustion air of AB percent means that AB percent more than thereuired stoichiometric air is being used.

Combustion instabilities are typically violent pressure oscillations in acombustion chamber. These pressure oscillations can be as high as A<? d"3and long term e/posure to these cyclic pressure and thermal loads reduces

the life of engine components. In rocets3 such as the *A used in the &aturn % program3 instabilities led to massive damage of the combustion chamber andsurrounding components. This problem was solved by re>designing the fuelin:ector. In liuid :et engines the droplet si4e and distribution can be used toattenuate the instabilities. Combustion instabilities are a ma:or concern inground>based gas turbine engines because of NO/ emissions. The tendency isto run lean3 an euivalence ratio less than A3 to reduce the combustiontemperature and thus reduce the NO/ emissionsG however3 running thecombustion lean maes it very susceptible to combustion instability.

The Rayleigh Criterion is the basis for analysis of thermo acoustic combustion

instability and is evaluated using the Rayleigh Inde/ over one cycle of instability

where is the heat release rate perturbation and p is the pressure0uctuation. =hen the heat release oscillations are in phase with the pressureoscillations3 the Rayleigh Inde/ is positive and the magnitude of the thermoacoustic instability is ma/imi4ed. On the other hand3 if the Rayleigh Inde/ isnegative3 then thermo acoustic damping occurs. The Rayleigh Criterionimplies that a thermo acoustic instability can be optimally controlled by

having heat release oscillations A<? degrees out of phase with pressureoscillations at the same freuency.J;K This minimi4es the Rayleigh Inde/.

CONC)UTION

In conclusion3 the application of motors in the career of chemical engineer

depend on which area is going to wor the engineer3 there are many motors

used in the food industry to transform raw materials :ust to mention a

e/ample. Depend on the industry the motors that will be used. Chemical

engineers besides wor with engines help to develop better fuel in order to

have better engines. The implementation of chemistry to develop better

engines is the most important part of the chemistry in the engine industry.

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