US 5,553,575 A · Lambda control by skip fire of unthrottled gas fueled engines

Abstract

The performance of a gas-fueled unthrottled internal combustion engine is improved by optimizing excess air ratio (lambda) in the engine. Lambda is optimized by selecting automatically and continuously the optimum fraction of cylinders firing (OFF) as a function of engine operating parameters, eliminating the fuel charge from one or more cylinders to obtain firing in the OFF, and distributing the unused fuel to the OFF, thereby decreasing lambda in the firing cylinders to an optimum level. OFF may be calculated according to mathematically derived and empirically weighted equations, or obtained with reference to suitable look-up tables. In addition, optimum lambda and OFF may be adjusted to take into account the effects of exhaust gas recirculation (egr), engine speed, and/or engine timing. Further lambda adjustment can be performed by suitable control of egr, ignition timing, and/or turbo air bypass (TAB).

Claims34

Dependent claims

A method of optimizing the excess air ratio (.lambda.) for a gaseous fuel-powered internal combustion engine, said engine having a number (N) of cylinders, said method comprising:

(A) ascertaining prevailing engine operating conditions;
(B) determining, based upon said prevailing engine operating conditions, an optimum fraction of cylinders (OFF) required to be fired to cause an actual value of .lambda. to at least approach an optimum value of .lambda. (.lambda..sub.OPT);
then
(C) determining a number (M) of cylinders that the firing of which must be skipped to produce said OFF, M being less than N;
and then
(D) eliminating a firing and fueling cycle in said M number of cylinders only.

3 more elements

A method of optimizing the excess air ratio (.lambda.) for a gaseous fuel-powered internal combustion engine, said engine having a number (N) of cylinders, said method comprising, on a cycle-by-cycle basis:

(A) ascertaining engine operating conditions including
(a) a prevailing indicated mean effective pressure (IMEP),
(b) an air charge temperature (ACT) of an ambient air charge admitted to said intake manifold, and
(c) a prevailing intake manifold absolute pressure (MAP);
then
(B) determining, based upon said engine operating conditions, an optimum fraction of cylinders (OFF) required to be fired to cause an actual value of .lambda. to at least approach an optimum value of .lambda. (.lambda..sub.OPT);
then
(C) determining a number (M) of cylinders the firing of which must be skipped to produce said OFF, M being less than N;
and then
(D) eliminating a firing and fueling cycle in said M number of cylinders only.

7 more elements

An internal combustion engine comprising:

(A) a number N of cylinders;
(B) a gaseous fuel injection system associated with said cylinders;
(C) an intake manifold cooperating with each of said cylinders;
and
(D) a control system which controls the operation of said engine, said control system including
(1) a plurality of sensors, each of which monitors an engine operating condition,
(2) means, responsive to said sensors, for determining an optimum fraction of cylinders (OFF) required to be fired to cause an actual value of an excess air ratio (.lambda.) to at least approach an optimum value of .lambda. (.lambda..sub.OPT),
(3) means for determining a number (M) of cylinders, the firing of which must be skipped to produce said OFF, M being less than N, and
(4) means for controlling said engine to eliminate a firing and fueling cycle in said M number of cylinders only.

6 more elements

An internal combustion engine comprising:

(A) a number N of cylinders;
(B) a gaseous fuel injection system associated with said cylinders;
(C) an intake manifold cooperating with each of said cylinders;
and
(D) a control system which controls the operation of said engine, said control system including
(1) a plurality of sensors monitoring
(a) a prevailing indicated mean effective pressure (IMEP),
(b) an air charge temperature (ACT) of an ambient air charge admitted to said intake manifold, and
(c) a prevailing intake manifold absolute pressure (MAP);
(2) means, responsive to said sensors, for determining an optimum fraction of cylinders (OFF) required to be fired to cause an actual value of .lambda. to at least approach an optimum value of .lambda. (.lambda..sub.OPT),
(3) means for determining a number (M) of cylinders the firing of which must be skipped to produce said OFF, M being less than N, and
(4) means for controlling, on a cycle-by-cycle basis, said engine to eliminate a firing and fueling cycle in said M number of cylinders only.

9 more elements

Dependencies are inferred from the claim text.

Lambda control by skip fire of unthrottled gas fueled engines

Life of this patent

Lambda control by skip fire of unthrottled gas fueled engines

Life of this patent

Abstract

Claims34