gas_blend
Purpose:
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Compute the ratio of three input gas streams to meet a required Heating Value and Methane Number. The outputs will be the ratios of each input stream, the Heating Value, and Methane Number of the resulting composition.
Enter:
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gas_blend <priority> <interval> <filename> [+c] &
Where:
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priority
Specify the system level task priority.
interval
Specify the time interval or rate to perform the calculations. The value must be one of the values supported by the scheduler as specified in the go script. Specify one of SLO, MED, or FAS.
filename
Specify the spec filename to read that contains the specifications of the gases that are to be blended.
+c
Optional. Specify this flag to indicate a critical watchdog task. The default is to leave the task as non-critical.
Example:
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gas_blend 12 SLO /specs/properties/blend_specs.111 &
The above command sets the priority of the process to be 12 and performs the computations at the rate of once every second. The spec file blend_specs.111 is read to determine the streams to be blended, the output stream composition, and mass flow. The gas_blend task will register it’s name with the filename (not the full pathame), in this case “blend_specs.111”. This name can be used by the ‘re-read’ command to request that it update the specifications by reading the specification file again. This feature allows the specifications to be changed “on-the-fly” without slaying and restarting the app. Note: re-read feature is not available prior to 6.3.30 or 6.4.0.
spec file #########################################
## ** Heating Value Target **
## The heating value target must be specified on EITHER a per unit mass
## basis, units group 20xx or on a per unit standard volume basis, units
## group 66xx. It can be specified as a fixed value with appropriate
## units or as the name of a Cyflex variable with the appropriate units.
## A dash, ‘-‘ must be used for the entry not selected as shown here:
##HV/mass HV/vol
HeatValTar –
## ** Methane Number Target **
## The methane number target must be specified as EITHER rich burn or lean
## burn. Both have units of [none], units group 51xx. The methane number
## can be specified as a fixed value with appropriate units or as the name
## of a Cyflex variable with the appropriate units. A dash, ‘-‘ must be
## used for the entry not selected as shown here:
##rich MN target lean MN target
MN_Tar –
## ** Input Steams and Calculated Mass Fractions **
## Three Cyflex composition variables containing the input stream
## compositions followed by the names of the Cyflex variables where the
## calculated mass fraction of the given stream will be stored that will
## produce the target heating value and methane number. The variables
## should be created by the user with units of mass fraction, units group
## 48xx. The primary stream should be listed first. This will normally
## be natural gas. The gas_prop task may be used independently to
## calculate heating values, methane numbers and other properties of the
## input streams:
##Input Stream Computed mixture mass fraction
ngC. ng_mass_frac
propaneC. c3h8_mass_frac
co2C. co2_mass_frac
## ** Mixed Stream Composition **
## The name of a Cyflex composition variable created by the user to store
## the calculated composition of the mixture that will produce the target
## methane number and heating value combination. The gas_prop task can be
## used independently to calculate heating values, methane numbers and
## other properties using this stream composition:
## Mixed stream composition
target_fuelC.
## ** Minimum and Maximum Methane Number @ Target Heating Value **
## The name of Cyflex variables to contain the minimum and maximum Methane
numbers that are possible for the specified target heating value. The
target methane number must lie between these values to be achievable:
Minimum Methane Number Maximum Methane Number
MN_Min MN_Max
Notes:
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This process computes gas composition by blending on a continuous basis and is normally started via the go script.