Systems and methods for controlling on-board generation and use of hydrogen fuel mixtures
This is a system for generating hydrogen on-board the vehicle from compressed natural gas (CNG) in select ratios to create hydrogen-enriched CNG (HCNG) fuel for use in internal combustion engines. The on-board generation of hydrogen is comprised of a reforming system of CNG fuel with direct contact with exhaust gases. The reforming system controls for production of HCNG fuel mixtures is based on specific engine operating conditions. The vehicle's engine controls and operating parameters are modified for combustion of selective ratios of HCNG fuel mixtures throughout engine operating cycle. The reforming system controls and engine controls modifications are also used to minimize combustion emissions and optimize engine performance.
1. An engine system using natural gas as a fuel, the system comprising:
a combustion system for combusting natural gas to produce energy and exhaust gas;
a pre-reforming system to receive unreformed natural gas and at least a portion of the exhaust gas from the combustion system, wherein the pre-reforming system is configured to generate a partial oxidation (PDX) reaction between unreformed natural gas and the exhaust gas to provide PDX reaction products;
a reforming system for reforming the PDX reaction products from the pre-reforming system to provide reformed natural gas, the reforming system including a steam reformer, a carbon dioxide reformer, and a first water-gas-shift reformer;
a mixing system for mixing reformed natural gas from the reforming system and unreformed natural gas to be delivered to the combustion system; and
a reforming control system for controlling the delivery of exhaust gas to the pre-forming system, wherein the at least a portion of the exhaust gas from the combustion system is delivered to the pre-reforming system at a first predetermined ratio with unreformed natural gas based on a first engine operating condition and at a second predetermined ratio with unreformed natural gas based on a second engine operating condition.
2. The system of claim 1 , wherein the reforming control system further controls the amount of unreformed natural gas delivered to the pre-reforming system as a ratio with exhaust gas.
3. The system of claim 1 , wherein the reforming control system further controls the amount of unreformed natural gas delivered to the steam reformer and carbon dioxide reformer as a ratio with the PDX reaction products from the pre-reforming system.
4. The system of claim 1 , wherein the reforming control system further controls the amount of unreformed natural gas delivered to the mixing system as a ratio with the products from the reforming system.
5. The system of claim 1 , wherein the first and second engine operating conditions are based on input quality of unreformed natural gas.
6. The system of claim 1 , wherein the first and second engine operating conditions are based on ambient temperature.
7. The system of claim 1 , wherein the first and second engine operating conditions are based on the demand on the engine.
8. The system of claim 1 , the reforming system further comprising a second water-gas-shift reformer.
9. The system of claim 1 , wherein the second water-gas-shift reformer operates at a lower temperature than the first water-gas-shift reformer.
10. The system of claim 1 , wherein the natural gas is natural gas, hydrogen enriched natural gas, or a combination thereof.
11. The system of claim 1 , wherein the combustion system includes a plurality of sensors.
12. The system of claim 11 , wherein the plurality of combustion system sensors detect one or more parameters selected from the group consisting of hydrogen flow rate, excess air to hydrogen ratio in the combustion system, and the temperature of the exhaust gas.
13. The system of claim 1 , wherein the pre-reforming system reduces the oxygen component in the exhaust gas as a result of excess air operating conditions in the engine.
14. The system of claim 1 wherein the pre-reforming system controls additional hydrogen generation based on required hydrogen ratios for engine operation.
15. The system of claim 1 , wherein the product of the reforming system is hydrogen enriched natural gas.
16. The system of claim 1 , further comprising one or more sensors in the reforming system.
17. The system of claim 16 , wherein the one or more sensors is selected from the group consisting of oxygen, temperature, and pressure sensors.
18. The system of claim 1 , wherein the engine system is on-board a vehicle.
19. A method for using natural gas as a fuel in an engine system, the method comprising:
combusting natural gas to produce energy and exhaust gas;
pre-reforming unreformed natural gas and at least a portion of the exhaust gas product from combusting natural gas, wherein pre-reforming generates a partial oxidation (PDX) reaction between unreformed natural gas and the exhaust gas to provide PDX reaction products;
reforming the PDX reaction products to provide reformed natural gas, wherein reforming includes steam reforming, carbon dioxide reforming, and water-gas-shift reforming;
mixing reformed natural gas and unreformed natural gas prior to combustion; and
controlling the delivery of exhaust gas for pre-forming, wherein the at least a portion of the exhaust gas product from combusting natural gas for pre-reforming is at a first predetermined ratio with unreformed natural gas based on a first engine operating condition and at a second predetermined ratio with unreformed natural gas based on a second engine operating condition.
20. The system of claim 19 , wherein the natural gas is natural gas, hydrogen enriched natural gas, or a combination thereof.