Chapter 5 - Normal and Abnormal Combustion and Combustion Parameters

Question 1

List the 6 critical aspects of the combustion process

Answer 1

1. Fuel
2. Air (oxidizer)
3. The correct amount of air/fuel
4. Air/fuel must be mixed well
5. Ignition source
6. No impingement

Question 2

What kind of air do burners incorporate

Answer 2

Primary and secondary air

Question 3

How does a Bunsen burner work? How does it burn?

Answer 3

Burns by mixing air and gas prior to initiating combustion. Finishes off combustion with secondary air.

Question 4

What are benefits to using a Bunsen burner?

Answer 4

Cleaner and more efficient combustion with higher temperatures and a blue flame.

Question 5

What is primary air?

Answer 5

Air that enters into the combustion process upstream of the burner ports

Question 6

Benefits of burning with primary air

Answer 6

Combustion is cleaner and primary air at the burner is easier to control

Question 7

What is secondary air?

Answer 7

Combustion air that enters into the combustion process downstream of the burner ports

Question 8

Why is secondary air needed?

Answer 8

Because it is impossible to get 100% of the needed primary air into a burner using only pressure energy from the fuel source

Question 9

What are transport losses?

Answer 9

Losses associated with too much excess air. (also in previous chapter losses from heating Nitrogen in the combustion air)

Question 10

What are the typical primary aeration rates in atmospheric gas burners? (Primary air %)

Answer 10

30-40% primary air

Question 11

What are the typical secondary aeration rates in atmospheric gas burners? (secondary air %)

Answer 11

80-100% secondary air

Question 12

What is secondary air penetration?

Answer 12

The correct amount of secondary air is in each and every burner port
With good secondary air penetration, total air requirements can be 120-130%. If it’s bad…200-300% range

Question 13

How is secondary air penetration controlled?

Answer 13

through burner design and baffling (inside the tube)

Question 14

How do baffles inside the tube influence the combustion process? (2)

Answer 14

They control the direction and flow of the secondary air
They limit the amount of secondary air that is allowed into the burner box
(Directs the secondary air into every burner port)

Question 15

Define frozen equilibrium

Answer 15

The interruption of the chemical process (combustion)

Question 16

Define impingement

Answer 16

Striking of a cold surface by hot combustion gases

Question 17

What indicates that impingement is taking place?

Answer 17

Presence of CO

Question 18

What is head height?

Answer 18

The amount of space above a burner for the combustion process to be completed

Question 19

How is COAF Calculated

Answer 19

CO x (CO2 ultimate/CO2 measured)

Question 20

What is port loading?

Answer 20

Parameter that shows the BTU/hr per the total burner port area

Question 21

What can port loading be used for?

Answer 21

1. Initial estimation of burner port sizes and the number of ports required
2. Resolving field problems
3. Understanding whether burners are over or underloaded
4. Comparing 2 burners
5. Providing an indication of port stability

Question 22

What is the presence of CO an indication of (2)

Answer 22

Rich mixture or impingement

Question 23

What does CO2 tell you

Answer 23

Can tell you how efficiently your fuel is burning. Higher CO2, the more efficiently the fuel is burning (with less excess air)

Question 24

What does dark blue flame indicate

Answer 24

good, clean combustion. Primary aeration is high, there is enough secondary air to finish the combustion process with clean combustion

Question 25

What does light blue flame indicate

Answer 25

Combustion probably clean but not as good. Primary aeration is good but not as high. Secondary aeration is adequate

Question 26

What does turquoise color indicate

Answer 26

rich burning mixture. flame usually dirty and will fail combustion tests. often accompanied by an aldehyde odor

Question 27

What does yellow tipping indicate

Answer 27

not as good and indicates insufficient primary aeration. Sometimes passes combustion testing Carbon will be deposited on surfaces

Question 28

How does carbon build up cause issues?

Answer 28

It may lead to a blockage

Question 29

What does orange flame indicate

Answer 29

Flame kernels are intense and hard working. Combustion normally clean

Question 30

What does yellow/orange streaked flame indicate

Answer 30

Flame kernels are low in primary aeration. Can indicate that airborne dirt is being burned

Question 31

How does NG burn differently than LP? (color)

Answer 31

NG burns a darker blue than LP

Question 32

Which flame colors require special attention?

Answer 32

Yellow, turquoise and light blue

Question 33

What is dew point?

Answer 33

Temperature at which condensation of the water vapor in the exhaust begins

Question 34

Why is dew point important?

Answer 34

The gas appliance will produce a certain amount of exhaust and potentially a lot of condensation (water) in a short amount of time. This can lead corrosion if certain design parameters and properties are not considered well.