08- Flame Stability

Faculty of Chemical & Natural Resources Engineering

BKG3721

Fuel & Combustion Lab

Experiment 8

Flame Stability & Flame Speed Of LPG Fuel

Name

Matric No.

Group

Program

Section

Date

Sem. 11 - Session 2012/2013

BKG3751 – Fuel and Combustion Lab Sem II-2012/2013

1.0 OBEJECTIVE 1.1 Study on the characteristics of flame stability

1.2 Determination of flame speed based on the cone method.

2.0 GENERAL DESCRIPTION

2.1 Unit Construction

Figure 1: Unit Construction for Flame Propagation & Stability Unit (Model: GE 02)

1. Air Flowmeter 8. Handheld Igniter

2. Gas Flowmeter 9. Panel

3. Ignition Button 10. Ignition Transformer with spark plug

4. Air Control Valve 11. Mixing Block

2

1

2

3

4

5

67

8

12

11

14

13

10

9


5. Gas Control Valve 12. Safety Foot Switch

6. Main Switch 13. Stabilizer Cone

7. Glass Tubes 14. Burner Tubes

2.2 Equipments

a) Air PumpFlow: 50 LPMMax Pressure: 40 kPa

b) Air FlowmeterFlowrate: 0 - 45 LPM

c) Gas FlowmeterFlowrate: 0 - 16 LPM (air)

d) Burner Tubes:Burner 1: OD = 12.5mm, ID = 9mmBurner 2: OD = 16.0mm, ID = 12.5mmBurner 3: OD = 19.0mm, ID = 16.0mmBurner 4: OD = 25.0mm, ID = 22.0mm

3.0 EXPERIMENTAL PROCEDURE

3.1 General Start-up Procedure

1. Switch on the air blower. Open the air control valve and ensure air flow is through to burner block.

2. Place foot on switch pad and open gas control valve and ignite mixture on mixing tube, using a gas lighter.

3. Actual quantities to give good light – up will be found by experience as they vary with different tubes and gases in use.

3.2 General Shut-down Procedure

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1. To extinguish the flame, turn off the gas valve and purge the system with air for a few seconds.

2. When finished with unit, isolate electrical and fuel supplies.

3.3 Flame Stability Test

1. Switch on power for the main unit.

2. Switch on the air blower.

3. Open the air valve and allow the air to flow through the unit for a few minutes.

4. Open the fuel gas valve and ignite the gas mixtures with an igniter.

5. Obtain a stable flame using a 22 mm inner diameter burner.

7. Observe the conditions of yellow tipping (YT), lift off (LO) and light back (LB). Record the corresponding air and fuel flow rates for all 3 conditions. Please refer to the Index section for more information on these 3 conditions.

6. Repeat the experiment by using different burner tube diameters (16mm & 12.5 mm)

3.4 Flame Speed Test

1. Start-up the unit as described in Experiment Flame Stability Test.

2. Obtain a stable flame using a 22 mm diameter burner.

3. Using a ruler, measure the height of the flame cone.

4. Repeat the experiment with different burner diameters (16mm & 12.5 mm).

4.0 Results

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Flame Stability

Burner Tube Diameter

Fuel Flowrate(L/s)

Air Flowrate(L/s) Fuel Air Ratio

mm Height (mm)

Actual YT LB LO YT LB LO

22

16

13

Flame Speed

Burner Tube Diameter Fuel Flowrate Fuel Flowrate

Flame Cone

Height

Clame Cone Area

mm Height (mm) Actual Height (mm) Actual mm mm2

5.0 Analysis & Discussions:

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1. Determine the air/fuel ratio and fuel/cross sectional area of the tube diameter for each condition and sketch the values on a graph paper.

2. Discuss the result obtain from graph paper.

3. Comment on the methods to increase flame stability.

4. Determine the flame speed from the following equation:

Su = Vfl / AF = Uo,m x Atube / AF

In which:

Uo,m = minimum flow velocity in tube (cm/s)

Su = flame speed

Vfl = volumetric flow rate (cm3/s)

AF = surface area of cone (cm2)

Atube = cross section area of tube (cm2)

AF =π r l

Where,r = radiusl = slant height

Air /fuel ratio = ρair (air flow rate)/ ρfuel (fuel flow rate)

5.0 Safety Measures

Unit should be operated in a well ventilated area and sited well away from inflammable or heat sensitive material.

Do not allow the unit to run with the gas control valve open if no flame has been established.

During use of fittings, mixing tubes, etc., will become hot. The use of a heat resistant glove is recommended when handling these items.

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08- Flame Stability