EGR flow measurement
AssigneeCaterpillar Inc.
InventorsGurpreet Gambhir, Rammohan Sankar, Travis Barnes, Zenebe Gete
Life of this patent
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Abstract
A system and method for measuring an EGR flow rate for an engine having an EGR valve with a selectable EGR valve position and a venturi sensor situated to take a differential pressure measurement relative to recirculated exhaust gas includes determining an EGR valve effective area based on the EGR valve position, determining a weighting factor based on the effective area, calculating a first EGR flow estimate based on the effective area, and calculating a second EGR flow estimate based on the differential pressure measurement of the venturi sensor. A final EGR flow rate is determined based on the weighting factor, the first EGR flow estimate, and the second EGR flow estimate.
Claims20
A method of measuring an exhaust gas recirculation (EGR) flow rate for an engine having an EGR valve with a selectable EGR valve position and having a venturi sensor situated to take a differential pressure measurement relative to recirculated exhaust gas, the method comprising:
- calculating a first EGR flow estimate based on the EGR valve effective area;
- calculating a second EGR flow estimate based on the differential pressure measurement of the venturi sensor;
- and
- determining a final EGR flow rate based on both the first EGR flow estimate, the second EGR flow estimate, and a weighting factor applied between the first and second EGR flow estimates,
- wherein the weighting factor favors the first EGR flow estimate when the selectable EGR valve position is below a predetermined value, and
- wherein the weighting factor favors the second EGR flow estimate when the selectable EGR valve position is above a predetermined value.
An engine exhaust gas recirculation system comprising:
- an exhaust gas recirculation (EGR) valve for selectively redirecting engine exhaust to an air intake of the engine via a flow path, the EGR valve having a position and a position sensor associated therewith;
- a venturi pressure sensor located in the flow path for sensing a differential pressure based at least in part on the flow of redirected engine exhaust;
- and
- a flow calculator for determining a rate of flow of the redirected engine exhaust, the flow calculator including a position-based estimator for generating a first estimate of the flow based on the position of the EGR valve, a pressure-based estimator for generating a second estimate of the flow based the differential pressure sensed by the venturi pressure sensor, and a weighting module for weighting the first and second estimates of the flow based on the EGR valve position,
- such that the rate of flow of the redirected engine exhaust is determined as the sum of the weighted first and second estimates,
- wherein the weighting factor favors the first estimate of the flow when the position is below a predetermined value, and
- wherein the weighting factor favors the second estimate of the flow when the position is above the predetermined value.
An engine control system for determining an exhaust gas recirculation (EGR) flow in an engine system having an EGR valve with a selectable EGR valve position and having a venturi sensor situated to take a differential pressure measurement relative to the recirculated exhaust gas, the engine control system including a controller executing computer-readable instructions including:
- instructions for determining an EGR valve effective area based on the EGR valve position;
- instructions for determining a weighting factor based on the EGR valve effective area;
- instructions for calculating a first EGR flow estimate based on the EGR valve effective area;
- instructions for calculating a second EGR flow estimate based on the differential pressure measurement of the venturi sensor;
- and
- instructions for determining a final EGR flow rate based on the weighting factor, the first EGR flow estimate, and the second EGR flow estimate;
- wherein the weighting factor favors the first EGR flow estimate, when the EGR valve position is below a predetermined value, and
- wherein the weighting factor favors the second EGR flow estimate when the EGR valve position is above a predetermined value.
Dependencies are inferred from the claim text.