E5: Select Gas Burners Flashcards
(163 cards)
1
Q
Gas burners can be either?
A
Mechanical or Non-Mechanical
2
Q
What determines the type of gas burner is used?
A
How the combustion air is supplied
3
Q
What’s another name for Non-mechanical gas burner?
A
atmospheric burner
4
Q
What do non-mechanical rely on for combustion air?
A
Atmospheric pressure
5
Q
What is High Fire?
A
max firing rate of a burner
Is the max fuel input / heat output a burner can safely be operated at.
6
Q
Low fire
A
min input of fuel required to keep a burner from flaming out
7
Q
Modulation
A
Vary gas input / vary heat output to a process in order to match heat load requirement / sustain the desired temp
8
Q
What is Turndown ratio? (TURNED DOWN FOR WHAT!)
A
ratio of the max fuel input : min fuel input rate for modulating burner.
9
Q
What is the Turndown ratio used for?
A
To help determine how low a boiler can modulate before it turns off
10
Q
Port loading
A
the amount of gas-air mixture passing through a burner that will create a stable flame
11
Q
What is port loading burner express as?
A
BTUs / square inch of port area
12
Q
How can the port loading be changed?
A
By altering the orifice size or gas pressure (manifold pressure)
13
Q
Port loading (NG) bn 25,000 - 30,000 BTUs / square inch indicates what?
A
Stable flame
14
Q
An atmospheric burner has a venturi that sucks primary air into where?
A
The burner / mixes air and gas before ignition
15
Q
How do Mechanical burners get their supply requirements for air combustion?
A
They use a fan or blower
16
Q
How are Mechanical burners categorized?
A
by:
1) location of the fan / blower in relation to the combustion chamber
2) Air pressure being delivered via burner / where the gas + air are mixed in the burner
17
Q
What are the different kinds of Mechanical burners?
A
1) Forced Draft Burner
2) Induced Draft Burner
3) Balanced draft burner
4) Fan - assisted burner
18
Q
What is a forced draft burner?
A
Combustion air is supplied by a fan or blower at sufficient pressure that overcomes resistance of the burner / appliance
19
Q
How does a forced air burner work?
A
Supplies air to burner / forces products of combustion through the appliance
20
Q
Where is the fan or blower located?
A
Upstream of the combustion zone
21
Q
How does a induced draft burner operate?
A
Uses mechanical draft produced by a fan located downstream / chimney side of combustion zone
22
Q
How is an Induced draft fan designed?
A
to pull in required air supply for combustion / vent products of combustion w/ positive vent pressure
23
Q
How is the Balanced Draft burner different?
A
It’s a combination of forced / induced draft
24
Q
Where are Balanced Draft burners mostly seen?
A
Larger boilers w/ multiple passes where the flue gases have to travel long distances
25
What is a Fan assisted burner?
Is a burner in which the combustion air is supplied by a mechanical device (fan / blower) at sufficient pressure to overcome the resistance of the burner only.
26
Where is the fan located?
upstream: fan assisted conversion burner
downstream: Fan assisted combustion system
27
Fan assisted systems give more precise control over what?
the air entering the combustion chamber
28
Mechanical combustion products are vented how?
Naturally w/ a nonpositive vent stack pressure
29
What is a pre-mix burner?
Mix the required amounts of air / gas before ignition
30
What are 3 types of pre-mix burners?
(MAG)
1) Inspirator or Gas Jet mixer
2) Aspirating Mixer
3) Mechanical Mixer
31
Inspirator burner uses what type of gas?
High pressure gas of 10 psi or more
32
Inspirators can entrain / pre mix up to what % of required combustion air?
100%
33
How does an Aspirating mixer work?
Uses pressurized air, issued at high velocity via venturi to entrain / mix gas
34
Aspirating mixer are common where?
on residential / commercial condensing boilers dt their excellent turndown
35
What does an Aspirating mixer use to mix gas?
Pressurized air at high velocity via a venturi
36
How is a Mechanical mixer straight forward?
uses a fan or blower to mix / supply air and gas to burner
37
How do burners create a stable flame?
by balancing the different combustion properties of gas - air mixture
38
What happens when combustion limits are exceeded?
The combustion process won't generate enough heat and flame will go out
39
What are the 4 combustion properties that effect the burner flame?
(LIMM)
1) Limits of flammability
2) Max flame speed
3) Ignition temp
4) Max flame temp
40
What are limits of flammability?
the upper and lower ranges of gas that support combustion
41
What is max flame speed?
The velocity the flame front moves towards the air-gas mixture
42
What is NG burn ratio?
4-15% fuel
43
A stable flame will has a what?
A balanced air-gas flow velocity / flame speed (that keeps the flame front close to burner spot)
44
What is ignition temp?
Is the temp at which an air-gas mixture will initiate / support combustion
45
What is flame temperature?
Max flame temp can only be reached at perfect combustion
46
True or False: Each fuel gas has its own max flame temp.
True
47
What is NG ignition temp?
700C - 1300F
48
What is the ignition temp of Propane?
490C - 920F
49
What is the ignition temp of Butane?
1980C - 3600F
50
What is a flame retention device?
When gas-air mixtures flow into sheltered areas / burns --> generating enough heat to ignite gas/air mixture leaving the burner head
51
What is a flame stabilizing device?
Provides shelter for the air-gas mixture to essentially ignite
52
What is the basics of an atmospheric burner?
a device that requires no fans or electrical supply
burns gas simply / efficiently
53
What are the 2 types of atmospheric burners?
1) Luminous
2) Bunsen burner
54
What does the luminous flame depend on for combustion?
the air around the flame (secondary air)
(it does not premix gas-mix mixture)
55
Why does the luminous flame have a small blue flame / large yellow flame?
Blue flame: hydrogen burns fast
Yellow flame: Carbon burns hot
56
Why does the Bunsen flame more efficient?
It premixes air w/ gas prior to ignition
57
True or False: a stable atmospheric Bunsen burner flame has several colour zones
True
each zone marks a stage in burning of the gas
58
What is the inner cone of a Bunsen flame?
Here gas is burned to form products (aldehydes, alcohols, CO + H)
Is the blue flame
Unburned gas mixture forms the shape of flame
59
What is the Outer cone
Here the secondary air around the flame diffuses into the flame takes part in burning
Inner cone products are completely burned here
60
Where does the highest flame temp occur?
Just above the outer cone tip
61
What is the Outer mantle?
- it's colourless, surrounds outer cone
- contains no unburned gases
- Glows dt combustion products high temps
62
What are the 3 types of Bunsen flames?
(RON)
1) Reducing flame
2) Oxidizing flame
3) Neutral flame
63
What colour of flame will a Bunsen flame have if it's stable?
Blue
64
What is a reducing flame?
Is a flame w/ low oxygen
65
What colour of flame will a reducing flame have?
Yellow dt the presence of unburned carbon (or hydrocarbons)
66
What's the second name for a reducing flame?
Carburizing flame
67
Why is it called a Carburizing flame?
When being brazed or welded carbon is introduced into molten metal...
68
What is an oxidizing flame?
flame produced w/ an excessive amount of oxygen
69
What happens when you increase oxygen in an oxidizing flame?
flame shortens
colour darkens
hisses / roar
70
Is the oxidizing flame good or bad for welding / soldering?
No, it oxidizes the metal's surface
71
What is the neutral flame?
The amount of oxygen is enough for burning
Oxidation / reduction does not occur
72
What colour of flame is the neutral flame?
clear blue due to a good balance of oxygen
73
What happens when a cold surface touches the inner cone of a bunsen burner?
temp decreases / causes incomplete combustion
74
What is an indicator of flame impingement?
Soot forming on the colder surface
75
Can impingement cause incomplete combustion in the occur in the outer cone?
No, this flame is too hot / maintains the temp for combustion
76
Is flow velocity the same at all points across a burner port?
No
77
What is a venturi?
Is a short tube w/ a constricted, throat - like passage
78
What does the narrowing passage of a venturi do?
Increases the velocity / creates a negative pressure in relation to the air surrounding the burner
79
What does a negative pressure do?
Sucks atmospheric air in
80
What is Bernoulli's Theorem?
When velocity increases, the pressure decreases
When velocity decreases, the pressure increases
81
What is an air shutter?
its used to adjust the size of air openings to control primary air flow
82
What are the primary air control devices? (WBRS)
- Wing
- Butterfly
- Rotating or sliding disc
- Spoiler screw
83
Is the orifice part of the burner?
No
84
Gas pressure and orifice size controls what?
The volume / velocity of the gas being injected in the burner.
85
What happens if you adjust the manifold (gas supply) pressure?
Change velocity of gas stream / venturi affect = changes primary air amount being drawn in
86
What is a mixing tube?
Portion of the tube that mixes gas and air together
87
What is a burner head?
Where gas/ air mixture enters the burner
Area is greatest - velocity is lowest and pressure is at its highest point
88
Is a burner port an orifice?
Yes
89
What does a burner port do?
1) discharges gas/ air mixture
2) distributes flames
3) spreads flanes
(More ports = more flames = more secondary air)
90
What characteristics should a properly functioning burner have?
- uniform heat
- complete combustion
- stable flames
- ready ignition
- quiet operation
91
What does a small hard blue flame off of burner port indicate?
Too much primary air
Air shutter should be closed
92
What does a soft, blurred or yellow tipped flame off the burner port indicate?
Lack of primary air
Air shutter should be opened
93
What are 2 main categories of atmospheric burners?
(Main pilot in the atmosphere)
Main burner
Pilot burner
94
What are 2 common types of atmospheric main burners?
(Main single multiport)
Single port
Multiport
95
What in a Single port burner?
Has an inshot burner that fires HORIZONTALLY into heat exchanger
96
What is an upshot burner?
Burns vertically
Common in domestic storage type water heaters
97
What is the most common atmospheric burner used in appliances?
Multiport burners
98
What is a burner bed?
When a number of multiport burners are used together
99
What is a pilot burner?
A small flame used to ignite the main burner
100
What are 2 types of pilot burners?
(A-NON)
Aerated pilots
Non-aerated pilots
101
What do aerated pilots do?
They premix air and gas
Have a sharp blue flame
primary air is drawn through a tube or air duct
102
Do aerated pilots have a stable flame?
yes and they produce higher flame temperatures
103
What is the common problem with Aerated pilots?
clogging of the primary air openings due to dust and lint
104
What are non-aerated pilots?
Have a short flame w/ little yellow colouring
Does not have dust / lint problems
105
What are non-aerated pilots affected by?
drafts / main burner variations
106
What are the most common problems w/ atmospheric burners?
- flashback
- Extinction pop
- Flame lift off
- Floating flames
- Waving flames
- Flame roll out
- Yellow tipping
- Fluctuating flames
- Gas odour
107
What happens in flashback?
Gas/ air mixture ignites inside the burner to burn near the orifice
108
What kind of noise does flashback make?
roaring noise like a torch
109
Flashback creates incomplete combustion which produces what?
Carbon monoxide / aldehydes
110
Does flashback produce soot?
Yes due to incomplete combustion
111
What causes flashback?
very lean gas/air mixture
112
What eliminates Flashback?
reduce the primary air to the burner
(without produces yellow-tipped flames)
113
If the burner is underfired (in flashback) what should happen?
Check input rate / adjust in to correct input value (orifice size / manifold pressure)
114
What is extinction pop?
When flashback occurs when the burner is shut off
115
What noise does an extinction pop make?
Bang
116
When does extinction pop occur?
When the gas supply is turned off
117
Is extinction pop dangerous?
No and will not damage appliance
Can blow out pilot light tho
118
What are some remedies for extinction pop?
Reduce primary air supply to the burner
119
Where is extinction pop a common problem?
on long atmospheric burners
120
What is Flame liftoff?
It's when part of the flame lifts or dances on the burner port
121
What causes flame liftoff?
when flow velocity of the gas/air mixture from a burner port is greater than the flame burning speed
aka high gas pressure
122
What kind of noise does a lifting flame create?
Roaring
123
What is a concern of flame liftoff?
incomplete combustion may escape flames
124
What are some remedies for lifting flames?
Reduce primary air
Also check, input is correct, orifice size / manifold pressure may need to be reduced first
(do not cause yellow tipping)
125
What is yellow flame due to?
Lack of primary air
126
What are Floating flames?
Are flames that do not have well-defined cones / appear to be reaching for air / roll around in the combustion chamber
flames are lazy looking
127
What kind of odour is present w/ floating flames?
a strong aldehyde odor
128
What do floating flames indicate?
incomplete combustion
129
Are floating flames dangerous?
Yes
130
What are some remedies for Floating flames?
appliance is overfired
2) Flue outlet too small
1) LACK OF SECONDARY AIR
131
What is the cause of Floating flame?
Poor venting
check for blockages at the flue collar
132
What is Waving flame?
is a result of drafts across burners = waving / unstable flame
133
What can cause waving flame?
a cracked heat exchanger
134
What are some remedies for waving flame?
eliminate external drafts across the floor
protect pilot with a suitable shield
135
What occurs in Flame rollout?
When flames rollout of the front of the combustion chamber when the burners are ignited
136
What can happen with Flame rollout?
fire hazard created, scorch appliance, burn wires or damage controls (can lead to flashblack)
137
What are some remedies for flame rollout?
Increase secondary air?
Check for blockages
138
What causes Flame rollout?
lack of combustion air dt over-firing of burners, poor draft or blockages in flue passage.
139
What is Yellow tipping?
when there is not enough primary air
140
What does yellow tipped flames indicate?
Incomplete combustion
141
Does yellow flames produce soot?
Yes
142
If there is a 1/32 build of of soot, this decreases efficiency losses by what?
16%
143
What do red or orange streak indicate?
dirt or dust in the primary air supply
144
What are remedies for yellow tipping?
Slowly open primary air shutter
Check the orifice - clean, realign or replace it if necessary.
145
What are Fluctuating Flames?
flames fluctuate over a period of time w/o adjust the burner.
146
Are fluctuating flames problematic?
No
147
What are some remedies for fluctuating flames?
(The farting hunter)
Faulty oversized hunting regulator or undersized gas piping.
148
What causes Fluctuating flames?
Unsteady gas pressures
149
True or false: normal burner operation has a negative pressure (vacuum) inside the primary air opening that draws air in.
True
150
How do you change input to a burner?
Adjust the manifold pressure or change area of the orifice
151
What is the most common type of a main burner orifice?
Fixed (plug)
152
Which gas range cap orifice has a higher heat value, cap is threaded clockwise = fixed flow through the needle hole?
Propane operation
153
Which gas range cap orifice has a lower heat value, greater flow rate required -- orifice cap is unthreaded counter clock wise, away from needle?
Natural Gas
154
How is vol of gas (flow rate) expressed?
ft3 / hr - input = BTU / h
m3 / hr - input = kW
155
How is the K factor determined?
angle of approach to the orifice
K = 0.9
156
True or False: Heavier gas will flow less easily through an orifice.
True
157
What are the specific gravities of propane, NG and butane?
NG = 0.6
Propane = 1.5
Butane = 2.0
158
What does DMS mean?
Drill manufactured size
159
True or False: Always choose the smaller orifice so that the appliance is not overfired.
True
160
What is combustion air made of?
Primary air - 1/3 - mixed w/ gas
Secondary - 2/3 - Air around flame
161
Where is excess air?
on the outlet side =
5ft3 / 1000BTU
162
Draft control
is Dilution air
15ft3 / 1000BTU
163
What is combustion air rated as?
10ft3/ 1000 BTUs
Requires 80% N2 / 20% O2
