US 6,463,907 B1 · Homogeneous charge compression ignition dual fuel engine and method for operation

Abstract

A Homogenous Charge Compression Ignition (HCCI) engine and operating method having ignition timing controlled on a cycle to cycle basis by adding to a primary fuel, which is typically greater than 95% and is a gas such as natural gas with a relatively slow burn rate, varying amounts of high cetane number fuel, typically diesel fuel, before or early in the compression stroke. The amount of high cetane fuel that is injected depends on engine speed and load, and is selected to insure that combustion is phased properly with crankshaft position. The ignition delay is thus controlled substantially independently of the burn duration, which is controlled by varying the amount of Exhaust Gas Recirculation (EGR) in conjunction with the air to fuel ratio so as to maintain a near constant crank angle burn duration over a wide range of engine speeds. Because of the relatively slow burn rate of the natural gas after ignition, relatively low EGR levels and high boost levels are practical with the subject HCCI engine so that its power density is greater than that of previous HCCI engines. The load and speed of the subject HCCI engine may be controlled over a wide range by varying the overall air to fuel ratio or the boost pressure. The high cetane liquid fuel may be injected together with the gas and early in the compression stroke so that the gas atomizes the liquid upon injection.

Claims22

Dependent claims

A method for operating a homogeneous charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:

providing in the cylinder a gaseous medium containing oxygen;
forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fluid fuel that is relatively difficult to ignite and a second fluid fuel that is relatively easy to ignite;
and
compressing the combustible mixture with the piston until combustion starts generally simultaneously at a plurality of locations distributed throughout the combustible mixture after an ignition delay determined by the proportion of the first fuel to the second fuel.

1 more element

A method for operating a homogenous charge, compression ignition engine, the engine having a cylinder and a piston moveable in the cylinder, and the method comprising the steps of:

providing in the cylinder a gaseous medium containing oxygen;
forming a combustible mixture by mixing generally homogeneously into the gaseous medium a first fluid fuel that is relatively difficult to ignite and a second fluid fuel that is relatively easy to ignite;
compressing the combustible mixture with the piston until combustion starts generally simultaneously at a plurality of locations distributed throughout the combustible mixture after an ignition delay determined by the proportion of the first fuel to the second fuel;
and
wherein the ignition delay begins when the piston is at a predetermined rotational position relative to top dead center and wherein the method further comprises the step of controlling the ignition delay by varying the ratio of the amount of the first fuel to the amount of the second fuel.

2 more elements

Dependencies are inferred from the claim text.

Homogeneous charge compression ignition dual fuel engine and method for operation

Life of this patent

Homogeneous charge compression ignition dual fuel engine and method for operation

Life of this patent

Abstract

Claims22