As crude oil gets more expensive, research for engines that can use fuel made from biomass is occurring. Some of these fuels are being made or collected today. Producer gas [other names or other similar fuels: town gas, coal gas, hygas, manufactured gas, syngas, SNG, woodgas, holzgas, air gas] (approximate molar analysis ~ 20% H2, 20% CO, 2% CH4, 42% N2, 8% CO2, 8% H20) is made from wood or other organic materials in gasifiers.
Biogas is formed in anaerobic digesters where microscopic organisms in the absence of air act on starches and other organic compounds to produce methane and carbon dioxide (approximate molar analysis 60% CH4, 30% CO2, 10% N2). The proposed engine to burn one of these gases will mechanically be much like the "Dual Pressure Intake Engine". The below diagram and animation describe the operation of this 'Green' engine.
(The engine could be SI or CI)
Biogas or Producer Gas Engine (With Low Pressure Direct Induction Fuel System) In the animation to the right the: Light blue = air intake (at 1 atm) and Navy blue = biogas or producer gas (storage pressure ~ 4 - 10 atm) Using an induction system similar to the Dual Pressure Intake Engine but with the fuel and air in separate intake runners, one can nearly double the volumetric efficiency of a regular Biogas Gas Engine without using a supercharger or turbocharger. This would be accomplished by first filling the cylinder with ambient pressure air and then allowing the biogas or producer gas to top the cylinder to a pressure of about 2 atm. Increasing volumetric efficiency of an engine by taking advantage of the pressurized fuel is important since both biogas and producer gas have a low heat content compared to natural gas for example. Also, the kinetic energy of the fuel/air mix will be high due to the large pressure differential between the induced air (~ 1 atm) and the fuel's storage pressure (4-10 atm). This should help the charge burn quicker and more efficiently. |  |