# US 9,038,580 B2 · Method and system for engine dilution control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,038,580 B2 - Document ID: US9038580B2 - Status: Granted - Kind: B2 - Application number: 13/401,713 - Filed: 2012-02-21 - Published: 2013-08-22 - Granted: 2015-05-26 - Earliest claimed: 2012-02-21 - Assignees: Ford Global Technologies, LLC - Applicants: Gopichandra Surnilla; Thomas G. Leone; Brad Alan VanDerWege; Christopher House; Michael Howard Shelby - Inventors: Gopichandra Surnilla; Thomas G. Leone; Brad Alan VanDerWege; Christopher House; Michael Howard Shelby - Web page: https://patentgrep.com/patent/US9038580B2 ## CPC - F02D 41/0025: {Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures} - F02D 41/005: {according to engine operating conditions} - F02D 2021/083: {controlling exhaust gas recirculation electronically} - Y02T 10/40: Engine management systems - F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract Methods and systems are provided for enabling engine dilution control. One or more engine diluents are combined to provide a desired engine dilution, the various diluents selected based on their respective combustion stability limits. A ratio of the various diluents used is further adjusted based on engine operating limitations. ## Claims ### Claim 1 A method of operating an engine, comprising: providing a desired engine dilution by combining a plurality of engine diluents, the diluents and their ratio selected based on respective combustion stability limits, the providing including increasing a first amount of a first diluent while decreasing a second amount of a second diluent, the first and the second amounts based on a determination of knock. ### Claim 2 (depends on 1) The method of claim 1, wherein a combustion stability limit of each diluent is based on a type of the diluent. ### Claim 3 (depends on 2) The method of claim 2, wherein the combustion stability limit of a diluent is based on a concentration of each elemental constituent of the diluent. ### Claim 4 (depends on 1) The method of claim 1, wherein the combining includes, selecting the first diluent with a first higher combustion stability limit to provide at least some of the desired engine dilution; and after the first diluent reaches a first combustion stability limit, selecting the second diluent with a second combustion stability limit lower than the first combustion stability limit to provide a remainder of the desired engine dilution. ### Claim 5 (depends on 4) The method of claim 4, wherein the first diluent includes EGR and wherein the second diluent includes direct injected water. ### Claim 6 (depends on 5) The method of claim 5, wherein the first combustion stability limit of the EGR is based on each of a carbon dioxide concentration, a nitrogen concentration, and a water concentration of the recirculated exhaust gas. ### Claim 7 (depends on 4) The method of claim 4, wherein the ratio of the first diluent and second diluent is further adjusted based on the combustion stability limit of each diluent in the combination. ### Claim 8 (depends on 7) The method of claim 7, wherein the providing the desired engine dilution by increasing a first amount of the first diluent while decreasing a second amount of the second diluent is performed during a first condition, the method further comprising during a second condition, decreasing the first amount of the first diluent while increasing the second amount of the second diluent. ### Claim 9 (depends on 8) The method of claim 8, wherein the first condition includes an engine knocking condition and during the first condition, a first amount of cooled EGR or water injection is increased while a second amount of internal EGR or hot EGR is decreased, and wherein the second condition includes cold start or low load engine operating conditions, and during the second condition, the second amount of hot EGR or internal EGR is increased while the first amount of cooled EGR or water injection is decreased. ### Claim 10 (depends on 1) The method of claim 1, wherein an amount of each selected diluent is adjusted based on the combustion stability limit of each diluent in the combination. ### Claim 11 A method of operating an engine, comprising: recirculating a first amount of exhaust gas from an engine exhaust to an engine intake to provide at least some of a desired engine dilution until a first combustion stability limit of the exhaust gas recirculation is reached; and after reaching the first combustion stability limit, injecting a second amount of engine diluent to provide a remainder of the desired engine dilution, the second amount based on a combustion stability limit of the first amount of exhaust gas, the first and second amounts adjusted to provide the desired engine dilution, the second amount of exhaust gas engine diluent decreased as the first amount of recirculated exhaust gas is increased. ### Claim 12 (depends on 11) The method of claim 11, wherein the first combustion stability limit is higher than a second combustion stability limit of the engine diluent. ### Claim 13 (depends on 11) The method of claim 11, wherein the first combustion stability limit is a wider combustion stability limit range than a second combustion stability limit of the engine diluent. ### Claim 14 (depends on 11) The method of claim 11, wherein the second amount of engine diluent includes one of direct injected water and variable cam timing. ### Claim 15 (depends on 11) The method of claim 11, wherein the desired engine dilution is based on a feed-forward indication of knock, the method further comprising, in response to a feedback indication of knock, injecting a knock control fluid and adjusting a combustion stability limit of each of the recirculated exhaust gas and the engine diluent based on the injected knock control fluid. ### Claim 16 An engine system, comprising: an engine including an intake and an exhaust; an injector configured to direct inject a fluid into an engine cylinder; an EGR passage for recirculating an amount of exhaust gas from the engine exhaust to the engine intake; a controller with computer readable instructions for: in response to a likelihood of knock, recirculating a first amount of exhaust gas via the EGR passage until a first combustion stability limit of the EGR is reached; and after the first combustion stability is reached, direct injecting a second amount of water into the engine cylinder until a second combustion stability limit of the direct injection is reached, wherein the first and second amounts are based on the likelihood of knock and each of the first and second combustion stability limits, the second amount of water decreased as the first amount of exhaust gas recirculation is increased to provide a desired engine dilution. ### Claim 17 (depends on 16) The system of claim 16, wherein the controller includes further instructions for adjusting a ratio of the first and second amounts based on an engine operating limitation, the limitation including one or more of exhaust PM content, exhaust temperature, likelihood of pre-ignition, and torque limitation. ### Claim 18 (depends on 16) The system of claim 16, wherein the adjusting includes, increasing the second amount of direct injected water while decreasing the first amount of exhaust gas in response to a pre-ignition limitation, and increasing the first amount of exhaust gas while decreasing the second amount of direct injected water in response to an exhaust temperature limitation. ### Claim 19 (depends on 16) The system of claim 16, wherein the controller is further configured to, in response to a feedback indication of knock, direct inject a third amount of knock-control fluid into the cylinder; and adjust the first and second combustion stability limits based on the third amount of knock-control fluid.