NAMA : M.E. TRIPENSUS H.

NIM : 5133122018

PRODI : 2013

BAHAN BAKAR DAN

PELUMASAN

1. How many kmole of air are needed to burn 1 kmol of carbon?

Jawab: Pembakaran sempurna: C + O2 ⇒ 1 CO2

1 kmole O2 memerlukan CO2 . karna udara memiliki kandungan 21 % O2, ini

berarti bahwa didalam melakukan pembakaran Carbon diperlukan udara (O2)

sebanyak 4,76 kmol.

2. Calculate the theoretical air-fuel ratio on a mass and mole basis for the combustion of

ethanol, C2H5OH ?

Jawab: Reaksi : C2H5OH + VO2(O2 + 3.76N2) ⇒ aCO2+ bH2O + cN2

Penyetaraan C : 2 = a Balance H: 6 = 2b ⇒ b = 3

Penyetaraan O : 1 + 2VO2 = 2a + b = 4 + 3 = 7 ⇒ VO2 = 3

(udara/bahan bakar) mol = VO2(1 + 3.76)/1

= 3 × 4.76

= 14.28

(udara/bahan bakar) massa = (VO2MO2 + VN2 MN2)/MFuel

= (3×31.999 + 11.28×28.013)/46.069

= 8.943

3. A certain fuel oil has the composition C10H22. If this fuel is burned with 150% theoretical

air, what is the composition of the products of combustion?

Jawab: C10H22 + (1/φ) VO2 (O2 + 3.76 N2) → a H2O + b CO2 + c N2 + d O2

Pembakaran sempurna : φ = 1, d = 0,

C disetarakan : b = 10

H disetarakan : a = 22/2 = 11

O disetarakan : 2 VO2 = a + 2b = 11 + 20 = 31

: => VO2 = 15.5

Keadaan sebenarnya : 1/φ = 1.5 => VO2 = 1.5 × 15.5 = 23.25

H disetarakan : a = 11,

C disetarakan : b = 10,

N disetarakan : c = 23.25 × 3.76 = 87.42

O2 disetarakan : d = 23.25 - 10 - 11/2 = 7.75 (kelebihan oksigen)

4. Methane is burned with 200% theoretical air. Find the composition and the dew point of

the products?

Jawab: Persamaan reaksi untuk campuran stokiometri adalah :

CH4 + VO2 (O2 + 3.76 N2)→ a H2O + b CO2 + c N2

C disetarakan : 1 = b

H disetarakan : 4 = 2a

O disetarakan : 2 VO2 = a + 2b = 2 + 2 × 1 => VO2 = 2

N2 disetarakan : 3.76 VO2 = c = 7.52

200% theoretical air: VO2 = 2 × 2 = 4 so now more O2 and N2

CH4 + VO2 (O2 + 3.76 N2)→ a H2O + b CO2 + c N2 + d O2

N2 disetarakan : 3.76 VO2 = c = 15.04

Ekstra oksigen : d = 4 – 1 - 1 = 2

Produk : 2 H2O + 1 CO2 + 15.04 N2 + 2 O2

Fraksi mol uap air : yv=2

1+2+2+15,04=0,0998

Parsial tekanan uap air : Pv = yv Po = 0.0998 × 101 = 9.98 kPa Pg(Tdew)

Pv = 9.98 kPa

Tdew = 45.8oC

5. Ethane (C2H6) is burned with 20 percent excess air during a combustion process.

Determine (a) the air-fuel ratio on mole and massbasis and (b) the product composition?

6. If I burn 1 kmol of hydrogen H2 with 6 kmol air what is A/F ratio on a mole basis and

what is the percent theoretical air?

Jawab: Combustion Eq. stoichiometric:

H2 + VO2(O2 + 3.76 N2) ⇒ 1 H2O + 3.76 VO2 N2

VO2 = 0.5 ; (A/F)S

= VO2 × (1 + 3.76) / 1

= 2.38

6 kmol dari udara adalah : 1.26 O2 + 4.74 N2 .

A/F ratio mol adalah 6, sehingga persen udara teoritis adalah

% teoritis udara ¿( A /F )ac( A / F)S

x 100

¿6

2,38X 100=252 %

7. Acetylene (C2H2) is burned withstoichiometric amount of air during a combustion

process. Asumming complate combustion, determine (a) the air- fuel ratio on a mass and

on a mole basis and (b) composition of product gas ?

Jawab : Pembakaran sempurna C2H2 yaitu :

C2 H 2+a (O2+3,76 N2 ) →2CO2+ H 2O+3,76 a N2

O2 disetarakan : a=2+0,5=2,5

Substitusikan:

C2H2 + 2,5 (O2 + 3,76N2) → 2CO2 + H2O + 9,4N2

a. AF = M (air)M (fuel)

=

(2,5 X 4,76kmol )(29kg

kmol)

(2mol )( 12 kgkmol )+ (1kmol )(2kg /kmol)

= 13,3 kg air / kg

fuel

b. AFmole basis=N air

N fuel

=(2,5 x 4,76)kmol

1 kmol fuel=11,9 kmol

airkmol

fuel

8. Octane (C8H18) is burned with 250 percent theoritical air, which enters the combustions

chamber at 250C. Asumming complate combustion and a total presure of 1 atm,determine

(a) the air-fuel ratio on mole and mass basis, (b) the ER and (c) the product composition?

Jawab: C8H18+2,5ath[O2+3,76N2] → 8CO2+9H2O+1,5athO2+(2,5x3,76)athN2

O2 disetarakan : 2,5ath = 8+4,5+1,5ath → ath= 12,5

Disubstitusikan :

C8H18+31,25[O2+3,76 N2] → 8 CO2+9 H2O+18,75 O2+117,5 N2

AF=mair

mfuel

=(31,25 X 4,76 kmol )(29 kg/mol)

(8 kmol ) (12 kg /mol )+(9mol )(2 kg /kmol)=37,8 k g

airkg

fuel

(b) Pv=¿

(c) Tdp=Tsat5,951 kPa=36,0 °C

9. Propane (C3H8) is burned with 75 percent excess airduring a combustion process.

Assuming complate combustion, determine (a) the air-fuel ratio on mole and mass basis,

(b) the ER and (c) the product composition?

Jawab: C3H8+1,75ath [O2+3,76 N2] → 3 CO2 + 4 H2O + 0,75ath O2 + (1,75X3,76)ath N2

O2 disetarakan : 1,75ath = 3 + 2 + 0,75ath → ath = 5

Disubstitusikan: C3H8+8,75 [O2 + 3,76 N2] → 3 CO2 + 4 H2 O + 3,75 O2 + 32,9 N2

AF=

mair

mfuel

=(8,76 x 4,76 kmol )(29 kg/mol)

(3 kmol )(12kg

mol )+ (4 kmol )(2kg /kmol)=27,5 kg

airkg

fuel

10. One kmol of ethane (C2H6) is burned with an unknown amount of air during a

combustion process. An analytsis of the combustion products reveals that the combustion

is coplate, and there are 3 kmol of free O2 in the products. Determine (a) the air-fuel ratio

and (b) the percentage of theoritical air used during this process?