Multiple CNG Cylinders in Automobiles.

prashantakerkar · 29th January 2014, 09:14 AM

Automobile - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Compressed_natural_gas‎

Is it possible to install Multiple (More than one) CNG Cylinders in Automobiles viz Medium and Heavy Vehicles viz Cars, Jeeps, Trucks, Lorries etc?.

I Feel the advantages would be double the Fuel storage capacity
in a automobile where in case one CNG Cylinder gets exhausted then automatically switching to the other CNG Cylinder as input Fuel source for the automobile.

Limitations could be the space required to fix the other extra CNG cylinder in the automobile ?.

Can this Limitation could be overcome in making space available for installation of another CNG Cylinder in the vehicle ?.

In terms of safety purposes do you recommend to have multiple CNG Cylinders in a automobile ?.

Thanks & Regards,
Prashant S Akerkar

bhvm · 29th January 2014, 04:04 PM

that's an interesting proposition Prashant!
many of us avoid cng because it's not practical for 500-700km one day trips. also cng is not available as readily as petrol .

however additional tanks will bring extra weight and will eat up more space in today's already small cars. perhaps something like that as an optional accessory in standard format will be useful.

Viru · 10th February 2014, 06:06 PM

That is actually a clever idea, especially for larger vehicles who have plenty of spare space or take very long journeys! Although bhvm is right about some of the possible drawbacks.

But if you think about it, rather than multiple tanks, wouldn't you be better off in terms of space, weight, safety, etc. if you just got a bigger tank?

I haven't used CNG so am not sure if various tank sizes are available, but someone might be able to build one if they aren't!

nanhi99 · 12th February 2014, 04:39 PM

yes it is possible to fit multiple cylinders, it depends on knowledge of fitter as stands are required for fitment, I have seen esteem, accent, honda accord, city with 2 cylinders, bigger cars such as innova etc can be fitted with bigger capacity cylinders thus increasing the running distance , fitting is easy.

Viru · 12th February 2014, 06:21 PM

Quote:

Originally Posted by nanhi99

yes it is possible to fit multiple cylinders, it depends on knowledge of fitter as stands are required for fitment, I have seen esteem, accent, honda accord, city with 2 cylinders, bigger cars such as innova etc can be fitted with bigger capacity cylinders thus increasing the running distance , fitting is easy.

Interesting...but is it legal to have multiple cylinders?

Vidhur · 17th February 2014, 01:41 AM

Quote:

Originally Posted by nanhi99

yes it is possible to fit multiple cylinders, it depends on knowledge of fitter as stands are required for fitment, I have seen esteem, accent, honda accord, city with 2 cylinders, bigger cars such as innova etc can be fitted with bigger capacity cylinders thus increasing the running distance , fitting is easy.

I have enquired.

2 cylinders is definitely illegal in any car.

It might also be unsafe. In smaller cars like esteem, accent etc. it is also likely to lead to suspension issues, as the weight of 2 full cylinders would be app. 170 kgs, whereas the boot is designed to carry a weight of only about 50 kgs.

Viru · 17th February 2014, 12:00 PM

IMO there might also be an increase in the risk of leakage!

suresh_gs · 17th February 2014, 05:22 PM

Quote:

Originally Posted by Viru

IMO there might also be an increase in the risk of leakage!

If you see a CNG driven bus, it will definitely have more number of cylinders. Not sure of the count. The reason is as follows. All liquid fuels have high energy density/unit volume. This parameter is of utmost importance as it dictates the driving range. Even though LPG and CNG are stored in liquid form, they are gaseous by nature and have low energy density/unit volume. CNG has energy density about 1/5th of diesel and 1/4th of petrol. That means to say the CNG tank should be at least 4 times bigger than the petrol tank to cover the same driving range. Since it is not feasible to go for a bigger size cylinder, in buses what is done is to have more no.of small cylinders.

konkantrip · 17th February 2014, 05:35 PM

Now in CNG 20 kgs tanks is also available which can store around 17 kgs of gas if the gas is filled at 220 PS pressessure. Secondly Multiple cyclinders can also be atached but it has its own drawbacks such as boot space will be decreased. The weight of the tank is more so the load on your suspensions will increase. Over all weight of the ehicle increases. If car manufaturer can provide some alternate fuel tank insted of pertrol and if goverment increase the CNG outlets in various cites then it can be diffrent picture.

suresh_gs · 17th February 2014, 05:46 PM

Quote:

Originally Posted by konkantrip

Now in CNG 20 kgs tanks is also available which can store around 17 kgs of gas if the gas is filled at 220 PS pressessure. Secondly Multiple cyclinders can also be atached but it has its own drawbacks such as boot space will be decreased. The weight of the tank is more so the load on your suspensions will increase. Over all weight of the ehicle increases. If car manufaturer can provide some alternate fuel tank insted of pertrol and if goverment increase the CNG outlets in various cites then it can be diffrent picture.

But in the case of bigger vehicles like bus, it makes sense to go for more number of cylinders. I remember seeing an Eicher CNG bus that had come to ARAI for testing with a number of cylinders. Not sure of the count though

Viru · 17th February 2014, 11:14 PM

Quote:

Originally Posted by suresh_gs

If you see a CNG driven bus, it will definitely have more number of cylinders. Not sure of the count. The reason is as follows. All liquid fuels have high energy density/unit volume. This parameter is of utmost importance as it dictates the driving range. Even though LPG and CNG are stored in liquid form, they are gaseous by nature and have low energy density/unit volume. CNG has energy density about 1/5th of diesel and 1/4th of petrol. That means to say the CNG tank should be at least 4 times bigger than the petrol tank to cover the same driving range. Since it is not feasible to go for a bigger size cylinder, in buses what is done is to have more no.of small cylinders.

Interesting, never knew that! But do the tanks empty sequentially or are they all kept at the same pressure for a constant drain rate from all of them?

Quote:

Originally Posted by konkantrip

Now in CNG 20 kgs tanks is also available which can store around 17 kgs of gas if the gas is filled at 220 PS pressessure. Secondly Multiple cyclinders can also be atached but it has its own drawbacks such as boot space will be decreased. The weight of the tank is more so the load on your suspensions will increase. Over all weight of the ehicle increases. If car manufaturer can provide some alternate fuel tank insted of pertrol and if goverment increase the CNG outlets in various cites then it can be diffrent picture.

I was considering a similar thing a while ago, but with LPG. Since LPG tanks are much more versatile these days than CNG tanks, why don't car makers offer versions of their cars with just an LPG tank instead of a petrol tank so we don't have to compromise on boot space or sacrifice the spare tyre, while benefitting from the LPG?

nanhi99 · 17th February 2014, 11:40 PM

sure it is illegal to have multiple cylinders but people with long distance running prefer 2 cylinders, both cylinders are connected with each other, so both are filled and consumed with single line.

Viru · 18th February 2014, 12:11 AM

Quote:

Originally Posted by nanhi99

sure it is illegal to have multiple cylinders but people with long distance running prefer 2 cylinders, both cylinders are connected with each other, so both are filled and consumed with single line.

So there's no valve between the tanks? That seems quite dangerous as the gas will always be moving between cylinders to equalize the pressure!

Vidhur · 18th February 2014, 02:16 AM

Quote:

Originally Posted by suresh_gs

That means to say the CNG tank should be at least 4 times bigger than the petrol tank to cover the same driving range.

Most cars have a driving range which is 1/3 to 1/2 of petrol.

Vidhur · 18th February 2014, 02:24 AM

Quote:

Originally Posted by konkantrip

Now in CNG 20 kgs tanks is also available which can store around 17 kgs of gas if the gas is filled at 220 PS pressessure.

The biggest tank available in the market, which does not even fit most cars and can only be used in wide boot cars like honda crv etc. contains no more than 13 kgs of usable gas.