Low pollution natural gas vehicle

Claim 3

A method as set forth in claim 1, wherein under low load conditions the cooling steps for the precompressed charge air are omitted and the fuel/air ratio is adjusted to a relatively lean value to reduce NO x emissions.

Claim 4

A method as set forth in claim 1, wherein the liquid natural gas is produced from well gas that has been stripped of substantially all of its non-methane hydrocarbons to reduce non-methane hydrocarbon emissions from the engine.

Claim 5

A fuel system for reducing NO x emissions from an internal combustion engine comprising a source of liquid natural gas fuel at cryogenic temperature and at a moderate pressure, a charge air delivery system, means for cooling the charge air passing through the delivery system with the heat of vaporization of the fuel whereby the maximum temperature developed in the engine is substantially reduced from that which would occur without the use of the cooling capacity of the fuel and the NO x produced in the combustion of the natural gas is reduced, the delivery system including compressor means for externally precompressing the charge air, an intercooler to reduce the temperature of the precompressed air and a second intercooler downstream of said first intercooler for further cooling the precompressed charge air with cooling by heat exchange with the liquid natural gas fuel.

Claim 6

A fuel system for reducing NO x emissions from an internal combustion engine comprising a source of liquid natural gas fuel at cryogenic temperature and at a moderate pressure, a charge air delivery system, means for cooling the charge air passing through the delivery system with the heat of vaporization of the fuel whereby the maximum temperature developed in the engine is substantially reduced from that which would occur without the use of the cooling capacity of the fuel and the NO x produced in the combustion of the natural gas is reduced, the delivery system including compressor means for externally precompressing the charge air, an intercooler to reduce the temperature of the precompressed air and a second intercooler downstream of said first intercooler for further cooling the precompressed charge air with cooling by heat exchange with the liquid natural gas fuel.

Claim 7

A system as set forth in claim 4, including control means to limit the cooling of the charge air to a temperature not lower than 32° F. to avoid the formation of frost.

Claim 8

A relatively large vehicle such as a passenger bus or truck comprising a chassis, an internal combustion engine for propelling the vehicle, a cryogenically insulated fuel tank for containing LNG at cryogenic temperatures and moderate pressures, a fuel line for conducting natural gas from the tank to the engine, a compressor for supplying pressurized charge air for combustion in the engine, conduit means for conducting the pressurized air from the compressor to the engine, heat exchanger means arranged to cool air compressed by the compressor and entering the engine, the heat exchanger means being arranged to transfer heat from the compressed air to the LNG in the fuel line between the tank and the engine, the reduced temperature of the charge air delivered to the engine being effective to reduce the maximum temperature reached in the combustion process within the engine and thereby reducing the NO x emissions from the engine.

Claim 9

A relatively large vehicle such as a passenger bus or truck comprising a chassis, an internal combustion engine for propelling the vehicle, a cryogenically insulated fuel tank for containing LNG at cryogenic temperatures and moderate pressures, a fuel line for conducting natural gas from the tank to the engine, a compressor for supplying pressurized charge air for combustion in the engine, conduit means for conducting the pressurized air from the compressor to the engine, heat exchanger means arranged to cool air compressed by the compressor and entering the engine, the heat exchanger means being arranged to transfer heat from the compressed air to the LNG in the fuel line between the tank and the engine, the reduced temperature of the charge air delivered to the engine being effective to reduce the maximum temperature reached in the combustion process within the engine and thereby reducing the NO x emissions from the engine.

Claim 10

A vehicle as set forth in claim 6, including control means responsive to low engine load to discontinue cooling of the precompressed air and to adjust the fuel/air ratio to an ultra-lean condition to reduce NO x emissions.