Early pilot lean burn strategy in dual fuel engine using targeted pilot flames
AssigneeCaterpillar Inc.
InventorsBobby John, Jonathan W. Anders
Life of this patent
Estimating the term…
Abstract
Operating a dual fuel engine system includes injecting an early shot and a second shot of a liquid fuel into a cylinder after a late closing timing of an intake valve, and producing a first and a second pilot flame based on ignition of the early shot and the second shot of liquid fuel. The early shot of liquid fuel is targeted such that a distribution of ignition points of the first pilot flame is biased outwardly of a combustion bowl in the piston. Propagation of the first and second pilot flames from geometrically distinct ignition locations rapidly increases pressure and temperature in the cylinder to provide fast combustion of a lean mixture of a gaseous fuel and air in a main charge in the cylinder.
Claims19
A method of operating a dual fuel engine system comprising:
- moving a piston in a cylinder in a dual fuel engine from a bottom dead center (BDC) position to a top dead center (TDC) position;
- injecting an early shot of a liquid fuel into the cylinder prior to completing the moving of the piston to the TDC position;
- producing a first pilot flame based on ignition of the early shot of liquid fuel;
- targeting the early shot of liquid fuel in the cylinder such that a distribution of ignition points of the first pilot flame is biased outwardly of a combustion bowl in the piston;
- producing a second pilot flame that propagates outwardly in the cylinder to merge with the first pilot flame;
- and
- combusting a stoichiometrically lean mixture of a gaseous fuel and air in the cylinder in a manner responsive to the production of the first pilot flame and the second pilot flame.
A method of combustion in a dual fuel internal combustion engine comprising:
- conveying a stoichiometrically lean mixture of a gaseous fuel and air into a cylinder in the dual fuel internal combustion engine;
- injecting an early shot of a liquid fuel into the cylinder targeted at a rim of a piston during a compression stroke of the piston in the engine cycle;
- injecting a second shot of liquid fuel into the cylinder after the injection of the early shot of liquid fuel;
- producing a first pilot flame and a second pilot flame in the cylinder based, respectively, on ignition of the early shot of liquid fuel and the second shot of liquid fuel;
- propagating the first pilot flame and the second pilot flame within the cylinder;
- and
- combusting the stoichiometrically lean mixture of gaseous fuel and air in the cylinder according to a combustion phasing that is based on the propagation of the first pilot flame and the second pilot flame.
A dual fuel internal combustion engine system comprising:
- an engine housing having a cylinder and an intake conduit formed therein;
- a piston movable within the cylinder between a bottom dead center (BCD) position and a top dead center (TDC) position, and having a rim extending circumferentially around a combustion bowl;
- an intake valve movable between an open position and a closed position to fluidly connect and disconnect the cylinder with the intake conduit;
- a gaseous fuel admission valve coupled with the engine housing and structured to admit a gaseous fuel for combustion in a stoichiometrically lean mixture of gaseous fuel and air in the cylinder;
- an electronically controlled variable valve actuator coupled with the intake valve;
- at least one electronically controlled liquid fuel injector structured to directly inject an early shot of a liquid fuel into the cylinder in an engine cycle;
- a combustion control unit coupled with each of the electronically controlled variable valve actuator and the at least one electronically controlled liquid fuel injector, and the combustion control unit being structured to:
- output a variable valve timing command to close the intake valve after commencing moving of the piston from the BDC position to the TDC position in an engine cycle;
- command production of a first pilot flame in the cylinder by outputting a first fuel injection command to inject an early shot of liquid fuel after the closing of the intake valve and prior to completing the moving of the piston to the TDC position in the engine cycle;
- command production of a second pilot flame in the cylinder by out putting a second fuel injection command to inject a second shot of a liquid fuel;
- target the early shot of liquid fuel at the rim of the piston;
- and
- target the second shot of liquid fuel within the cylinder, such that the first pilot flame and the second pilot flame propagate from outward ignition points and inward ignition points, respectively, within the cylinder.
Dependencies are inferred from the claim text.