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Design of CNG kit

  1. May 4, 2006 #1
    Dear all!


    i am working on project "design of cng Kit" ,Please help me in this regard.
  2. jcsd
  3. May 4, 2006 #2


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    Staff: Mentor

    Happy to help. Welcome to PF. What's a CNG kit?
  4. May 4, 2006 #3
    basically CNG (compressed Natural Gas) it is now a days used in vehicles instead of Gasoline fuel. CNG kit is a complete system. compressed gas is at 300 bar in storag cylinder. it is brought upto the pressure of 2 bar after passing throug pressure regulator in CNG kit then this gas enters the engine.
    i am working on its design i need help either any reference book any guideline.
  5. May 4, 2006 #4


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    Science Advisor

    A system like this is not a science unto itself. It is comprised of sub topics that one must have a knowledge of in order to work with the design. You are asking a pretty broad question. Do you have any knowledge in areas like pressure vessels, fluid mechanics or even the theory of how a pressure regulator/relief work?

    My suggestion is that you ask very specific questions. We can not/won't help you design the entire system. You need to do the leg work. Ask specific questions and the help will follow.
  6. May 5, 2006 #5
    Thanks for guiding me FredGarvin
    pressure reduces in the pressure regulator of CNG kit when Gas enters the Chamber of it due to Expansion how we can co relate pressure and volume? to reduce pressure from 300 bar to 4 bar and we know the initial volume how we can get the chamber volume.
  7. May 5, 2006 #6
    All I know if that in my CNG pressure regulator, the vacuum from the engine controls a diaphram. This diaphram is connected to a "needle and seat" sort of setup that will regulate how much gas flows into the engine. As for the control unit, they use a motorola MCU that monitors the O2, MAP sensor, etc and then controls the inlet servo and engine timing as required. Sorry I can't really help you anymore there.
  8. May 5, 2006 #7


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    Your flow rate should remain mostly the same through the regulator. Use continuity for your calc.

    The regulator you are describing is refered to as a dome loaded regulator. Again, it doesn't really regulate the amount of flow, but it creates a restriction which either increases or decreases the delta p across it required to maintain flow.
  9. May 7, 2006 #8
    pressure drops in pressure regulator from 300 bar to 4 bar in 1st stage chamber due to expansion how you can corelate pressure volume and temperature as temperature also drops in it
  10. May 8, 2006 #9


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    Gold Member

    These are all basic thermodynamic questions. Perhaps you should read up a little on the subject? Borrow a library text book on Thermodynamics.
  11. May 19, 2006 #10
    i am
    doing my bsc in mechanical engg
  12. May 19, 2006 #11
    plz help me in the design of cng kit
  13. May 20, 2006 #12


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    Gold Member

    You as well?! People here will be willing to help you out, perhaps you should have a look at the advice given earlier on in the thread, or ask a particular question relating to your project?
  14. May 12, 2007 #13
    Hai friends,
    I have a doubt.
    1. What is the pressure value of CNG at the inlet of pressure regulator? ( Is 250 bar or less )

    2. When the level of CNG in cylinder decreases, then there will be decrease in pressure also. Hence, how can the pressure regulator can work for varying pressure of CNG?
  15. Feb 1, 2009 #14
    i'm working on a project about cng. i interviewed an specialist about cng from the department of energy. if the cng tank has the label that its working pressure is 3600 psi.. then if u are refilling and when the pressure gauge has reached 3600 psi, it is now in full tank. if the pressure gauge reads 2600 psi, then ur tank is not full. regarding the pressurre regulator, if its label is inlet: 3600 psi and outlet: 115 psi then the maximum pressure it can recieve is 3600 and can be lower than that and the regulated pressure is 115. now, some cng system uses 2 regulators.. for example the first regulator is inlet inlet: 3600 psi and outlet: 115 psi then you have to use another regultor that can regulate the pressure of the gas fom 115 psi to the pressure that is needed in the system.

    i hope this wont confuse u.. hehe sorry for my grammar. look for the standards regarding cng sytem.. u can search in the web
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