1
HVACR214 – Mechanical for Oil
Oil Nozzles
Air Mixing
2
Oil Nozzle
• The oil nozzle is responsible for delivering the
fuel, in the correct pattern, angle and quantity to
sustain proper combustion.
3
Oil Nozzle
• In order to find the proper nozzle we must know:
– The required gallons per hour
– The spray angle
– The spray Pattern
• Solid
• Hollow
• Semi-Hollow
4
Nozzle Construction
• Nozzles are made of a stainless steel tip,
sometimes the whole body is stainless steel.
• The stainless steel is a highly polished and
reflective surface which prevents gumming.
• Some manufactures use a brass body and a
stainless steel tip.
5
Nozzle Construction
• Inside the nozzle:
– A nozzle stem (or distributor) or a valve stem brings the
oil from the filter to the swirl chamber.
– The nozzle orifice is located at the end of the swirl
chamber which allows the oil to leave the nozzle.
6
Nozzle Construction
• The porous filter is made of brass or steel and
catches any sediment that may have bypassed
the tank filter and the pump strainer.
• The filters purpose is to prevent blockage of the
nozzle orifice.
7
Oil Nozzle Construction
8
Nozzle Functions
• Atomizes fuel oil into tiny droplets
– Results in a quicker vaporization when exposed to heat.
• Meters the fuel (metering device)
– + or -5% of the rated capacity
9
Nozzle Functions
• Delivers the fuel in a specific pattern
• This pattern must match the air delivery pattern
– Solid
– Semi Solid
– Hollow
10
Hollow Pattern
11
Hollow Pattern
• Is used on shell head burners
• The center of the spray is void of oil droplets
• Used for a heavy center air pattern (lots of air in
the middle)
• Used on 2.0 GPH and up nozzles.
12
Solid Pattern
13
Solid Pattern
• Solid spray is used with
– Standard oil burner (With end cone)
– It sends tiny oil droplets through the entire cone.
– Oil is placed directly into the air stream.
14
Semi-Hollow (Semi-Solid)
15
Semi-Solid Spray
• Semi-Solid Spray is used:
– With retention head burners
– When there is a very small space inside the end cone
where there should be no oil droplets and no swirling
air.
16
Spray Pattern
• These are a rule of thumb. With the advent of
newer and higher efficiency systems you must use
the manufacturer recommended nozzles.
17
Nozzle Functions
• Delivers the oil in a specific angle of spray.
– The resulting flame must fit into the combustion
chamber
– It can not hit on (or impinge on) the floor or the side
walls
– It must have a uniform spray angle
18
Impingement
19
Solved Impingement
20
Nozzle Functions
• The nozzle cleans the oil up by the inline strainer.
21
How it works
• The oil enters the swirl chamber at the end of
the nozzle at 100 psi.
• The swirl chamber converts this pressure into
velocity and rotation.
• The swirl chamber creates the:
– Hollow spray pattern
– Solid spray pattern
– Special or semi-solid spray patterns
22
Nozzle Performance
• All nozzles are rated for 100 psi of pressure.
• If the pressure changes the rating is no longer
valid.
23
Low Pressure
• A nozzle at low pressure will have
– A weak spray pattern
– Under fires burner
– Droplets of oil are larger and that lowers efficiency and
increases smoke.
24
High Pressure
• High pressure nozzles:
– Create smaller droplets
– Increase the flow rate
– Are sometimes better for cold oil and ignition problems.
25
Effects of pressure
• Some manufacturers are:
– Using higher pump pressures, up to 300 psi.
– Lowering nozzle size
– Gaining efficiency (makes the burners burn cleaner)
26
Temperature and the nozzle
• The higher the temperature the lower the
viscosity of the oil.
• As the temperature drops:
–
–
–
–
The oil thickens
Less swirl in the chamber
Higher flow
More fuel and larger droplets are created.
• This problem is called “cold oil”
27
Nozzle Spray Angle
• The spray angle of the nozzle is 30 to 90
degrees.
• Most common are:
–
–
–
–
–
–
30
45
60
70
80
90
28
Nozzle Spray Angle
• The nozzle spray needs to fit the combustion
chamber.
– Round or square combustion chambers use a 70-90
degree nozzle.
• With a hollow or semi-solid pattern
– Long and narrow combustion chambers use a 30 - 70
degree nozzle
• With a solid pattern
29
Nozzle Spray Angles
• The spray angle must allow the flame to burn in
suspension, meaning it will not hit any walls or
floor in the combustion chamber.
• If it hits the walls it will cause smoke and soot.
This is called impingement.
30
Nozzle Care and Service
•
•
•
•
Never change the inner parts.
Keep in carton until ready to use.
Keep clean when handling
Clean nozzle line with clean oil (J-Tube or Jet
Tube)
• If you spot oil drops on nozzle tip or chamber
floor this indicates a bad adaptor or nozzle,
change them.
31
Nozzle Care and Service
• Never re-use an old nozzle. They CAN NOT BE
CLEANED!
• In case of a clogged nozzle orifice you can clean
with a toothpick, never use metal. Then you must
change it at first opportunity.
• ALWAYS REPLACE A NOZZLE WITH A NEW
ONE!
32
Nozzle Sizing
• The gallons per hour must be sized correctly.
• Under sizing a nozzle will reduce capacity and
possibly increase smoke.
• Over sizing the nozzle will reduce the life of
equipment by burning out heat exchanges and
combustion chambers.
33
Nozzle Sizing
• Name plate will have the nozzle size or BTU
ratings.
• If missing use the following:
– GPH = BTU INPUT/140,000
• If BTU Input is missing use the output divided by
112,000 (GPH of oil at 80%)
34
Nozzle Sizing
• If the name plate indicates the square feet of
steam convert the square feet of steam to
Output BTU’s by:
– Ft2 Steam X 240
• If the name plate indicates the square feet of
hot water, convert to Output BTU’s by:
– Ft2 of Hot Water x 165
35