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In a joint the flow from two gas pipes is united and redirected
through a third pipe. So in principal three fluid elements of type GAS PIPE
have one node in common in a joint. The fluid elements of type BRANCH JOINT represent the
extra energy loss due to the merging of the flows and have to be inserted on
the incoming branches of the joint. This is represented schematically in
Figure 62. The filled circles represent corner nodes of the fluid
elements, the others are the midside nodes. For a joint to work properly the
flow direction must be as indicated in Figure 62. If the
solution of the equation system indicates that this is not the case
appropriate measures must be taken. For instance, if the solution reveals that
there is one inward flow and two outward flows, branch split elements must be selected.
Figure 62:
Element selection for a joint
 |
Several types of geometry are available.
A branch joint of type GE [53], Figure 63, is quite general and allows
arbitary cross sections and angles (within reasonable limits). It
is characterized by the following constants (to be specified in that order on
the line beneath the *FLUID SECTION, TYPE=BRANCH JOINT
GE card):
- label of the gas pipe element defined as branch 0.
- label of the gas pipe element defined as branch 1.
- label of the gas pipe element defined as branch 2.
- cross section
of branch 0.
- cross section
of branch 1.
- cross section
of branch 2.
- angle
(
).
- angle
(
).
- oil mass flow in branch 1 (only if the OIL parameter is used to define
the kind of oil in the *FLUID SECTION card)
- oil mass flow in branch 2 (only if the OIL parameter is used to define
the kind of oil in the *FLUID SECTION card)
Figure 63:
Geometry of a joint fluid section type GE
 |
A branch joint of type Idelchik1, Figure 64, can be used if one of the incoming branches
is continued in a straight way and does not change its cross section [23]. It
is characterized by the following constants (to be specified in that order on
the line beneath the *FLUID SECTION, TYPE=BRANCH JOINT
IDELCHIK1 card):
- label of the gas pipe element defined as branch 0.
- label of the gas pipe element defined as branch 1.
- label of the gas pipe element defined as branch 2.
- cross section
of branch 0.
- cross section
of branch 2.
- angle
(
).
- oil mass flow in branch 1 (only if the OIL parameter is used to define
the kind of oil in the *FLUID SECTION card)
- oil mass flow in branch 2 (only if the OIL parameter is used to define
the kind of oil in the *FLUID SECTION card)
Figure 64:
Geometry of a joint fluid section type Idelchik 1
 |
A branch joint of type Idelchik2, Figure 65, can be used if one of the incoming branches
is continued in a straight way but may change its cross section [23]. It
is characterized by the following constants (to be specified in that order on
the line beneath the *FLUID SECTION, TYPE=BRANCH JOINT
IDELCHIK2 card):
- label of the gas pipe element defined as branch 0.
- label of the gas pipe element defined as branch 1.
- label of the gas pipe element defined as branch 2.
- cross section
of branch 0.
- cross section
of branch 1.
- cross section
of branch 2.
- angle
(
).
- oil mass flow in branch 1 (only if the OIL parameter is used to define
the kind of oil in the *FLUID SECTION card)
- oil mass flow in branch 2 (only if the OIL parameter is used to define
the kind of oil in the *FLUID SECTION card)
Figure 65:
Geometry of a joint fluid section type Idelchik 2
 |
Next: Branch, Split
Up: Fluid Section Types: Gases
Previous: Restrictor, User
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guido dhondt
2009-08-12