Bi-fuel Engine Using Hydrogen

Abstract

A method is disclosed for making a transition from fueling an engine with hydrogen to another fuel. That other fuel may be gasoline, a gasoline and alcohol mixture, or gaseous fuels, as examples. The other fuel has the capability of providing higher BMEP than the hydrogen because of better air utilization and because the other fuel occupies less volume of the combustion chamber. Because a desirable equivalence ratio to burn hydrogen is at 0.5 or less and a desirable equivalence ratio to burn other fuel is at 1.0, when a demand for BMEP that leads to a transition change from hydrogen fuel to the other fuel, the amount of air supplied to the engine is decreased to provide more torque and vice versa. During a transition in which liquid fuel supply is initiated, it may desirable to continue to provide some hydrogen, not leaner than 0.1 hydrogen equivalence ratio.

Description

FIELD OF THE INVENTION[0001]A method to operate an internal combustion engine which is supplied with both hydrogen fuel and another fuel is disclosed.BACKGROUND[0002]Because of concerns about greenhouse gases that are emitted from carbon-containing fuels, such as gasoline, diesel, and alcohol fuels, there is keen interest in fueling motor vehicles with hydrogen, which produces water upon combustion. Hydrogen-fueled internal-combustion engines suffer from a low power output compared to gasoline or diesel powered engines due to hydrogen being a gaseous fuel which takes up much of the volume in the cylinder, particularly when compared to dense fuels like gasoline or diesel fuel. Furthermore, hydrogen combustion is limited to operating at an equivalence ratio of about 0.5 or less due to increasing combustion harshness and, if it is a concern, rapidly increasing NOx emission. An equivalence ratio of one is a stoichiometric ratio meaning that the proportion of fuel to air is such that all...

AI Technical Summary

Benefits of technology

The present invention proposes a bifuel engine that can operate on both hydrogen and gasoline. The engine can transition between these fuels based on the demand for torque. The use of hydrogen as a fuel has advantages such as its ability to burn at low torque levels with minimal throttling. Gasoline, on the other hand, provides high torque levels. The engine can also use high torque fuels like natural gas or alcohols, either alone or in combination with liquid fuels like methanol or ethanol. The engine uses a normalized torque measurement called BMEP. The transition between fuels is initiated when the demand for torque exceeds a certain threshold. The air supply is decreased and the supply of the second fuel is increased during the transition. The use of hydrogen as a fuel helps reduce greenhouse gas emissions.

Problems solved by technology

Hydrogen-fueled internal-combustion engines suffer from a low power output compared to gasoline or diesel powered engines due to hydrogen being a gaseous fuel which takes up much of the volume in the cylinder, particularly when compared to dense fuels like gasoline or diesel fuel.

Furthermore, hydrogen combustion is limited to operating at an equivalence ratio of about 0.5 or less due to increasing combustion harshness and, if it is a concern, rapidly increasing NOx emission.

Such a limit in equivalence ratio results in about half the fuel delivery as could be consumed by the amount of air in the chamber, and consequently about half of the torque developed by the engine than if at a stoichiometric proportion.

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