Bobjengr, thanks for your clarification. I think most of our readers may have same doubt, when reading an article with respect to natural gas/CNG/LPG. I hope the response from our various members will help them to clarify it.
Hello My Design--Basically, natural gas is methane. Generally 84 to 90 % methane with a heating value ranging from 900 to 1200 Btu/Ft^ 3. LPG is classified as propane or butane. Propane has a heating value of approximately 2500 Btu/Ft^3 where as butane is 3500 Btu/Ft^3. In climates experienced in the United States, butane is not that suitable for most usage. Propane is the LPG of choice. Hope this helps.
"Natural gas is essentially methane, whereas liquefied petroleum (propane and butane) is a hydrocarbon-based gas. It is used in automobiles, but its energy density is lower than that of gasoline, so its fuel consumption is higher."
Murray, thanks for the clarification and I think you are right.
"Many vehicles could be modified to run on natural gas. I have a friend who has traveled extensively in Asia and found lots of natural gas powered vehicles there. '
Naperlou, in our country, for a particular state all the public transport vehicles are using CNG (Compressed Natural Gas) and state government insisted all private vehicles to convert the mode of fuel as CNG. Federal government also has a plan to make it compulsory from 2016.
Direct injection is an interesting concept that might work well with CNG since the pressure is quite high
LP gas is stored as a liquid at around 300PSI
The pressure for CNG in the tank is about 200 atm (14*200 = 2800 PSI).
Usuall pressure in engine is about 12-16 atm (160-260 PSI).
So I don't beleive that direct injection of CNG is practical. However make use of the higher pressure for gas enabled (LPG & CNG) vehicales could be the option.
The technical challenge in this case is how to combile the gas (higher pressure) and gasoline injection in single engine. Most of the cars has two tanks: one for usuall gasoline and another for CNG/LPG.
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