COMB - Lecture notes 1-5 PDF

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COMBUSTION ENGINEERING (FME19)ILLUSTRATIVE PROBLEMS – CONCEPT OF FUELSEXAMPLE 1:A diesel engine consumes 650 liters of fuel at 26oC in 24 hours with 28oAPI. Determine the fuel rate in kg per hour. Answer: 23 kg/hourSolution:Given: Volume rate at 26oC = 650 liters/24 hours = 27 lit/hr API rating = 28...

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COMBUSTION ENGINEERING (FME19) ILLUSTRATIVE PROBLEMS – CONCEPT OF FUELS EXAMPLE 1: A diesel engine consumes 650 liters of fuel at 26oC in 24 hours with 28oAPI. Determine the fuel rate in kg per hour. Answer: 23.83 kg/hour Solution: Given:

Volume rate at 26oC = 650 liters/24 hours = 27.083 lit/hr API rating = 28

Required:

mass flow rate of fuel (m)

Computation:

based on fuel temperature of 26oC m = ρ26 x V 26 ρ26 = SG26 x ρwater ρwater = 1000 kg/m3 where: SG26 = SGs x Ct 141.5 141.5 SGs = = = 0.8871 131.5+ API 131.5 + 28 Ct = 1 – 0.0007 (tf – 15.6) = 1 – 0.0007 (26 – 15.6) = 0.9927 Then, SG26 = (0.8871) (0.9927) = 0.8806 ρ 26 = (0.8806) (1000 kg/m3) = 880.6 kg/m3

finally , m = (880.6 kg/m3) (27.083 lit/hr) (1 m3/1000 lit) = 23.85 kg/hr (answer) =================================================================

EXAMPLE 2: A cylindrical tank 3 m long and 2 m diameter is used for fuel storage. How many days can the tank supply the engine having 27oAPI with fuel consumption of 60 kg/hour? answer: 5.84 days Solution: Given: Fuel, Required:

cylindrical tank, D=2m o API = 27 mṁ = 60 kg/hr

L=3m

Number of days to supply fuel 1

Computation:

Since the fuel temperature is not given, it is based on standard temperature of 15.6oC

Number of days (to supply fuel) = Solving for mass of fuel, m: ρ15.6 = SGS x

where:

total mass of fuel mass flow rate m = ρ 15.6 x V 15.6

ρwater

=

SGs =

m 60 kg / hr

141.5 131.5+ API

=

141.5 131.5 + 27

=

0.8927 ρ15.6 = (0.8927) (1000 kg/m3) = 892.7 kg/m3 π (2)2 m2 (3m) = 9.425 m3 4 m = (892.7 kg/m3) (9.425 m3) = 8413.499 kg

V = V 15.6 = V TANK then,

=

8413.499 kg 60 kg /hr = 140.225 hrs = 5.84 days (answer) ================================================================= finally,

Number of days (to supply fuel) =

EXAMPLE 3: A diesel power plant uses fuel oil that has a density of 892.74 kg/m3 at 15.6oC. Find the heating value of the fuel in KJ/kg using the ASME formula.(answer: 44,899.31 KJ/kg) Solution: Given:

Required:

fuel temperature (standard), t = 15.6oC ρ15.6 = 892.74 kg/m3 Heating value of the fuel, QH

Computation: Using ASME Formula, Q H =41,130+139.6( API ) , KJ/kg Solving for the oAPI rating of the fuel: 141.5 ρ15.6 = SGS x also, SGs = 131.5+ API 892.74 kg /m 3 SGs = 1000 kg/m 3 141.5 , oAPI = 27 Then, 0.89274 = 131.5+ API Finally,

Q H =41,130+139.6(27) = 44,899.2 KJ/kg

ρwater = 0.89274

(answer)

2

====================================================================== EXAMPLE 4: A certain coal supplied to a coal thermal plant has the following ultimate analysis: C = 69% H2 = 2.5% O2 = 3.5% N2 = 5% S = 7% Ash = 5% Moisture = 8% Determine the total heating value of one ton fuel. Solution: Given:

m = 1 ton = 1000 kg Ultimate analysis of fuel: C = 69.00% H2 = 2.50% O2 = 3.50% N2 = 5.00% S = 7.00% Ash = 5.00% Moisture = 8.00% _______ 100% Required: Heating value of the fuel, QH Computation: Solving for the total heating value of fuel, Q Q = mass of fuel x heating value of fuel = m x QH where:

solving for the higher heating value (QH) Using Dulong’s Formula, O Q H =33,820C +144,212 H 2− 2 +9,304 S , KJ /kg 8 0.035 Q H =33,820(0,69 )+ 144,212 0.025− +9,304(0.07), KJ /kg 8 QH = 29,961.45 KJ

(

)

(

Finally,

)

Q = (1000 kg) (29,961.45 KJ/kg) = 29,961,450 KJ

(answer)

====================================================================== ASSIGNMENTS – CONCEPTS OF FUELS: ASSIGN. #1: 1. A diesel engine consumed 945 liters of fuel per day at 30oC. If the fuel was purchased at 15.5oC and 30oAPI at P50.00 per liter, determine the cost of fuel to operate the engine per day. ans. P46,772 2. A cylindrical tank 5 m long and 3 m diameter is used for fuel storage. If the fuel has a 30oAPI rating, find the total heating value of the fuel contained in this tank in KJ. 3

ASSIGN. #2: 1. An engine uses fuel with a heating value of 45,038.8 KJ/kg. Find the density of the fuel at 30oC. answer: 0.878 kg/lit 2. A bituminous coal has the following composition: C = 71.5% H2 = 5% O2 = 7% N2 = 1.3% S = 3.6% Ash = 8.2% Moisture = 3.4% Determine the lower heating value of the fuel in KJ/kg.

4...