HOW TO CALCULATE A SINGLE CYCLE GasTurb 12 – Tutorial 1 Copyright © GasTurb GmbH.
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Transcript of HOW TO CALCULATE A SINGLE CYCLE GasTurb 12 – Tutorial 1 Copyright © GasTurb GmbH.
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HOW TO CALCULATE A SINGLE CYCLE
GasTurb 12 – Tutorial 1
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A Jet Engine Example
The Program offers three Scopes that differ in the amount of detail being simulated. The
Basic Thermodynamics
scope is least demanding for the user.
Only simple textbook wisdom is considered.
For professional performance work use the
Engine Design option. Choose Performance
or…
More… if you want to determine the engine
geometry.Let us begin with a jet engine simulation. Select the most
simple engine architecture, a Turbojet.
A click on Performance in the Engine Design button group
begins the calculation
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We Need Some Data…
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Cycle Design Input Data Window
All input is in clear nomenclature - no cryptic abbreviations are
used.
Switching to Imperial Units is easy
Let’s go back to SI Units
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Thermodynamic Station Input
The flow areas at the stations are either a design point input
or are derived from a Mach number. These flow areas
affect only the static pressures and temperatures. The main cycle parameters like thermal
efficiency or thrust, for example are not affected by the input on
the Stations page.
Click here to start the calculation
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Single Cycle Output
On this summary page there is no room for lengthy property names. The international standard nomenclature for performance computer programs is employed. For example, P is total pressure, T total temperature andW is employed for mass flow.
Explanations are at your fingertip: Click a symbol – for example TSFC - and you get a detailed explanation.
Most people are using m for mass flow. When the standard
nomenclature was agreed on the letter M could not be used
because in early FORTRAN programs any property name
beginning with M was an Integer. The letter W for mass flow
reminds of the outdated designationweight flow.
Most people are using m for mass flow. When the standard
nomenclature was agreed on the letter M could not be used
because in early FORTRAN programs any property name
beginning with M was an Integer. The letter W for mass flow
reminds of the outdated designationweight flow.
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Thermodynamic Station Output
Here are all the details at the thermodynamic stations.
The flow areas at all the stations are stored in memory. During off-design simulations the
static pressures and temperatures are calculated from flow area, mass flow, total
pressures and total temperature.
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Getting Additional Output
Open the Composed Values window – a powerful formula
editor.
I need to know a cycle property
which is not listed on the output page.
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Composed Values Editor
Click here to check and evaluate all
composed values.
Compose your additional output values from the input and output quantities. You can even use empirical correlations (Tables) and more than 50 predefined Functions
Example: Calculate the kinetic energy of the nozzle exhaustJetEnergy=W8*V8^2/2Dividing by 1000 yields the Jet Energy in kW
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Output with Composed Value
After closing the Composed Values window run the case again – now you have JetEnergy as additional output.
Next let us have a look at the Enthalpy-Entropy diagram of the cycle
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Enthalpy-Entropy Diagram
Click here to open the slider definition window.
We now freeze this diagram for making comparisons with another
cycle.
The diagram shows real numbers. See how it
changes with compressor pressure ratio
Click to reduce to one
slider only
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Using the Slider…
Move the Slider to the right – this increases
Pressure Ratio.
Now you see how the pressure ratio of the compressor affects the hot section
part of the cycle
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Single Cycle Output
This is again the original cycle. The turbine pressure ratio of 3.178 is easily achievable with a single
stage turbine. In fact, a single stage turbine can work up to a pressure ratio of 4 with an acceptable efficiency.
Let us search for the compressor pressure ratio which yields exactly the turbine pressure ratio of 4. Close this window to proceed.
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Single Cycle Input Data Page
We will vary (iterate) compressor Pressure Ratio in such a way that
Turbine Pressure Ratio is equal to 4.
We open now the Iterations input window.
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Iteration Variable Input
Min and max boundaries for the variable are required for numerical
reasons. The min and max values need not to be accurate, they are for excluding physical meaningless numbers (like very low pressure ratios) from the
calculations.
From all the input Variables we choose Pressure Ratio and drag it from the selection tree to the table.
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Iteration Target Input
From all the output quantities we choose Turbine Pressure Ratio as
Target and drag it from the selection tree to the table.
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Iteration Target Value Input
Enter the target value here…
…and activate the iteration.
Then close the window.
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Single Cycle Input Data Page
Now we are ready to run the case
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The Cycle with Turbine Pressure Ratio = 4
This slide ends the Single Cycle Tutorial