Monday, January 16, 2017

Computer software for pintle injector design data

Pintle injector designer is a beta version of a small throttleable liquid rocket engine design software. It is currently being beta tested and will be available free of cost within 3 months. Currently,this software is used for Face Shut Off type pintle injector, final product will be capable of providing design data for Slit type as well. Future versions will have results of calculation for dimensions of the injectors in CAD software recognizable format.

Calculating the mass flow rates of a rocket engine is a time consuming process.  Pintle injector design software eases the calculation process. This software reduces mass flow rate and discharge area calculation for a liquid fueld combustion chamber to just 5 minutes.

You can use the current version of pintle injector design software to calculate the mass flow rate and discharge are needed for a pintle injector to be used in liquid rocket engines.

 The resulting data is printed to a file called "myfile.txt".

How to use the pintle injector design software to calculate the mass flow rate and discharge ?
  • STEP 1-Select the thrust and propellants of the rocket engine.
  • STEP 2 -Combustion chamber pressure.
  • STEP 3- Fix the optimum mixture ratio of the rocket engine
  • STEP 4- Find out the Flame Temperature, Molar Mass, Specific heat Ratio and Characteristic velocity(C star) of the exhaust gases in the rocket combustion chamber. These values can be found out using NASA CEA application.
  • STEP 5-Download and open Pintle Injector Design Software
  • STEP 6-Enter the Specific Heat ratio.
  • STEP 7-Exit pressure(Sea level/Vacuum pressure in Pascal)
  • STEP 8-Enter the Inside pressure as the combustion chamber pressure.
  • STEP 9-Enter the thrust of the engine to be designed
  • STEP 10- Flame temperature in the Temperature of Combustion field.
  • STEP 11- Enter the optimum mixture ratio in the mixture ratio field.
  • STEP 12-In Gas Constant field enter the specific gas constant(It is universal gas constant/Molar mass) and submit.

Pintle injector Design software- entering inputs such as Thrust of  rocket engine, Mixture ratio etc
The out put will be shown on the right side of pintle injector design software. Out put includes the thrust co-efficient of the rocket, throat area of the nozzle. Mass flow rate of the fuel and oxidizer required for the selected thrust of the rocket engine. Click on Next button for calculating the discharge area needed to reach the required mass flow rates of propellants.

  • STEP 13- Enter the discharge co-efficients of fuel and oxidizer exits. They can be reasonably approximated to 0.7 or exact value can be found after the fabrication.
  • STEP 14- Enter the pressure drop of fuel and oxidizer in the next. A good approximation is 20% drop from the combustion chamber pressure as noted from SP-125 NASA rocket design book.
  • STEP 15- Enter the Density of fuel and oxidizer in kg/metre cube.

Entering propellant properties in the pintle injector design software

  • STEP 16-Next page is to find the pintle dimensions, just enter the pintle diameter. Outer and inner diamter is used to find the annular gap. This portion is yet to be developed. So enter some junk values and do manual calculation for this data for your design.
  • You can download the pintle injector design software here Download. Please make sure that you have the latest Java version installed on you PC.
    Special thanks to Albin Shaji (Computer Science Department-Karunya University) for writing the code for this software.
    The full data required for the pintle injector will be written to "myfile.txt" file created on the same folder where this software is installed.

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