Engine system using liquid air and combustible fuel

Abstract

An automobile engine runs on liquid air plus a small amount of solid or liquid fossil fuel. The liquid is an efficient method of storing the energy of liquefaction. To get extended range and use of energy effectively some fuel is used to increase the temperature of this gas before it is introduced into the expansion engine. Two methods of using this fuel may be employed--one burns fuel internally in the expansion engine cylinders essentially at constant volume so a liquid form of the fossil fuel must be used; while the second method heats the gaseous working medium at constant pressure external from the expansion engine in a furnace so it can burn a wide range of either liquid or solid fossil fuels. With either system of operation the air/nitrogen as liquid is pumped at the rate of use from the insulated cold storage container up to high intial operation pressure (about 200 atmospheres) then passes through heat exchangers to bring it up to the intial temperature for expansion. Since the liquid and gas is at very low temperature (77.degree. Kelvin - 196.degree. C., - 320.degree. F.) much of this heating energy can be drawn from the ambient air and surrounding equipment. In either system each expansion stage utilizes a properly sized reciprocating piston in a cylinder with exhaust valving and variable cutoff inlet valving (for efficient torque and speed variation). Pistons from all of the several expansion stages are coupled to a common power output. These engine exhaust gases may be employed to warm the intially cold high pressure liquid air in a counter-current heat exchanger.