In part one of this article, we looked at compressed air as a propellant gas for the Green Dragon. In this part, we will look at carbon dioxide.
Like compressed air, CO2 is also available in a variety of cylinder sizes and types. From a commercial gas dealer there are two types. There are tall, slim cylinders used for welding and shorter, squat cylinders used in the beverage industry. Both types have a CGA-320 fitting. Like air cylinders, you can pay a one-time deposit and a then a fee to have the cylinder refilled or exchanged.
There are also smaller cylinders available which have a pin valve connection. These are used for paintball guns and portable tools. They are relatively inexpensive to purchase (<$30), and can be refilled for under $5 at any paintball game location.
Unlike compressed air which is a gas, CO2 is stored as a mixture of liquid and gas. This liquid / gas system is the same type as found in a propane barbeque cylinder. As long as there is a mixture of liquid and gas in the cylinder, the pressure depends only on the ambient air temperature. At an ambient temperature of 70°F, the pressure in the cylinder is about 850psi.
As gas is used by the launcher, the pressure in the cylinder starts to drop slightly and some of the liquid boils to create more gas and keep the system at a constant pressure. As the liquid boils, it absorbs energy from its surroundings which is the reason why the cylinder gets frosty during use.
As more gas is used, the boiling process continues and the liquid level drops in the cylinder until all of the liquid has been turned into gas. After that, consuming gas causes the pressure to drop just like a compressed air cylinder.
The amount of CO2 in a cylinder is measured by its net weight. Beverage cylinders are available in 5lb, 10lb and 20lb capacities, while the smaller pin type cylinders are available in 9 or 20 oz. Every pound of liquid will boil off to give about 7.5 cubic feet of gas. With the Green Dragon regulator set to 90psi, you could expect about 6000 shots out of a 20lb cylinder.
The size of the cylinder also determines how fast you can operate the launcher. If you try to use a small 9 oz cylinder, it can’t boil the liquid fast enough to run the Green Dragon at high rates of operation. It would be like trying to run a 60,000 BTU barbeque with a one pound bottle of propane designed for a campstove.
As with compressed air systems, you need a regulator to reduce the cylinder pressure before connecting to the Green Dragon. The Green Dragon comes with a cylinder regulator with a CGA-320.
The advantage of CO2 over compressed air is that you can store more energy because the CO2 is in liquid form. For example, a CO2 bottle with a 20lb charge can produce 150 cubic feet of gas at atmospheric pressure versus 80 cubic feet for a SCUBA cylinder of similar dimensions. The disadvantage is that the cylinder must remain upright because if liquid enters the valve system, it will boil off in the valve and cause the valve to freeze. This can be a mounting challenge for some vehicles.
Like compressed air, CO2 is also available in a variety of cylinder sizes and types. From a commercial gas dealer there are two types. There are tall, slim cylinders used for welding and shorter, squat cylinders used in the beverage industry. Both types have a CGA-320 fitting. Like air cylinders, you can pay a one-time deposit and a then a fee to have the cylinder refilled or exchanged.
There are also smaller cylinders available which have a pin valve connection. These are used for paintball guns and portable tools. They are relatively inexpensive to purchase (<$30), and can be refilled for under $5 at any paintball game location.
Unlike compressed air which is a gas, CO2 is stored as a mixture of liquid and gas. This liquid / gas system is the same type as found in a propane barbeque cylinder. As long as there is a mixture of liquid and gas in the cylinder, the pressure depends only on the ambient air temperature. At an ambient temperature of 70°F, the pressure in the cylinder is about 850psi.
As gas is used by the launcher, the pressure in the cylinder starts to drop slightly and some of the liquid boils to create more gas and keep the system at a constant pressure. As the liquid boils, it absorbs energy from its surroundings which is the reason why the cylinder gets frosty during use.
As more gas is used, the boiling process continues and the liquid level drops in the cylinder until all of the liquid has been turned into gas. After that, consuming gas causes the pressure to drop just like a compressed air cylinder.
The amount of CO2 in a cylinder is measured by its net weight. Beverage cylinders are available in 5lb, 10lb and 20lb capacities, while the smaller pin type cylinders are available in 9 or 20 oz. Every pound of liquid will boil off to give about 7.5 cubic feet of gas. With the Green Dragon regulator set to 90psi, you could expect about 6000 shots out of a 20lb cylinder.
The size of the cylinder also determines how fast you can operate the launcher. If you try to use a small 9 oz cylinder, it can’t boil the liquid fast enough to run the Green Dragon at high rates of operation. It would be like trying to run a 60,000 BTU barbeque with a one pound bottle of propane designed for a campstove.
As with compressed air systems, you need a regulator to reduce the cylinder pressure before connecting to the Green Dragon. The Green Dragon comes with a cylinder regulator with a CGA-320.
The advantage of CO2 over compressed air is that you can store more energy because the CO2 is in liquid form. For example, a CO2 bottle with a 20lb charge can produce 150 cubic feet of gas at atmospheric pressure versus 80 cubic feet for a SCUBA cylinder of similar dimensions. The disadvantage is that the cylinder must remain upright because if liquid enters the valve system, it will boil off in the valve and cause the valve to freeze. This can be a mounting challenge for some vehicles.
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