# US 8,543,317 B2 · Method for managing the relative humidity in the air path of an internal combustion engine equipped with a low pressure EGR system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,543,317 B2 - Document ID: US8543317B2 - Status: Granted - Kind: B2 - Application number: 13/091,888 - Filed: 2011-04-21 - Published: 2012-02-02 - Granted: 2013-09-24 - Earliest claimed: 2010-04-21 - Assignees: GM Global Technology Operations LLC - Applicants: Paolo Pasero; Alberto Vassallo; Federico Luigi Guglielmone - Inventors: Paolo Pasero; Alberto Vassallo; Federico Luigi Guglielmone - Web page: https://patentgrep.com/patent/US8543317B2 ## CPC - F02D 41/005: {according to engine operating conditions} - F02M 26/28: with liquid-cooled heat exchangers - F02B 29/0406: {Layout of the intake air cooling or coolant circuit} - F02D 41/0007: {for control of turbo-charged or super-charged engines (control of the pumps per se F02B37/12)} - F02D 41/0065: {Specific aspects of external EGR control (constructional details of EGR system F02M26/00)} - F02D 2200/0418: Air humidity - F02M 26/06: Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor - F02M 26/15: in relation to engine exhaust purifying apparatus - 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) - F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF - F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A method is provided for estimating the relative humidity in an intake line of an internal combustion engine provided with an intake manifold connected to the intake line, an exhaust line, and a Low Pressure EGR (LPE) conduit which fluidly connects the exhaust line to a connecting point of said intake line. The method includes, but is not limited to calculating specific humidity in the exhaust line, as a function of the O2 concentration in said exhaust line; determining ambient specific humidity; calculating specific humidity in a portion of the intake line comprised between said connecting point and said intake manifold, as a function of a flow of external air entering into said intake line, a flow of exhaust gases coming from said Low Pressure EGR (LPE) conduit, the specific humidity in said exhaust line and the ambient specific humidity; calculating the relative humidity in said portion of the intake line, as a function of the specific humidity thereof. ## Claims ### Claim 1 A method for estimating a relative humidity in an intake line of an internal combustion engine provided with an intake manifold connected to the intake line, an exhaust line, and a Low Pressure EGR (LPE) conduit that fluidly connects the exhaust line to a connecting point of the intake line, said method comprising: calculating a first specific humidity in the exhaust line as a function of an O2 concentration in said exhaust line; determining an ambient specific humidity; calculating a second specific humidity in a portion of the intake line comprised between said connecting point and said intake manifold as a function of a flow of external air entering into said intake line, a flow of exhaust gases coming from said Low Pressure EGR (LPE) conduit, the first specific humidity in the exhaust line and the ambient specific humidity; and calculating the relative humidity in said portion of the intake line, as a function of the specific humidity. ### Claim 2 (depends on 1) The method according to claim 1, further comprising measuring the O2 concentration in the exhaust line with a lambda sensor. ### Claim 3 (depends on 1) The method according to claim 1, further comprising calculating the specific humidity and the relative humidity in said portion of the intake line upstream of a compressor. ### Claim 4 (depends on 1) The method according to claim 1, further comprising calculation the specific humidity and the relative humidity in said portion of the intake line downstream of a charge air cooler. ### Claim 5 (depends on 1) The method according to claim 1, further comprising estimating the relative humidity in said portion of the intake line at least on a basis of a map correlating ambient humidity to ambient temperature. ### Claim 6 (depends on 1) The method according to claim 1, further comprising: comparing said relative humidity with a first threshold of said relative humidity and in case said relative humidity is above said first threshold; and adjusting an exhaust gas flow into said portion such as to reduce the relative humidity. ### Claim 7 (depends on 6) The method according to claim 6, further comprising: defining a second threshold of said relative humidity, said second threshold lower than said first threshold; and adjusting the exhaust gas flow into said portion to reduce the relative humidity therein below said second threshold. ### Claim 8 (depends on 6) The method according to claim 6, wherein said adjusting a gas flow into said portion of the intake line comprises regulating a ratio of exhaust gas flow circulating in a High Pressure EGR (HPE) conduit with respect to the exhaust gas flow circulating in the Low Pressure EGR (LPE) conduit. ### Claim 9 An internal combustion engine comprising an intake line; an intake manifold connected to the intake line; an exhaust line; a Low Pressure EGR (LPE) conduit that fluidly connects the exhaust line to a connecting point of the intake line; and an Electronic Control Unit (ECU) configured to: determine an ambient specific humidity; calculate specific humidity in a portion of the intake line comprised between said connecting point and said intake manifold as a function of a flow of external air entering into said intake line, a flow of exhaust gases coming from said Low Pressure EGR (LPE) conduit, the specific humidity in the exhaust line and the ambient specific humidity; and calculate a relative humidity in said portion of the intake line, as a function of the specific humidity. ### Claim 10 (depends on 9) The internal combustion engine according to claim 9, wherein the ECU is further configured to measure an O2 concentration in the exhaust line with a lambda sensor. ### Claim 11 (depends on 9) The internal combustion engine according to claim 9, wherein the ECU is further configured to calculate the specific humidity and the relative humidity in said portion of the intake line upstream of a compressor. ### Claim 12 (depends on 9) The internal combustion engine according to claim 9, wherein the ECU is further configured to calculate the specific humidity and the relative humidity in said portion of the intake line downstream of a charge air cooler. ### Claim 13 (depends on 9) The internal combustion engine according to claim 9, wherein the ECU is further configured to estimate the relative humidity in said portion of the intake line at least on a basis of a map correlating ambient humidity to ambient temperature. ### Claim 14 (depends on 9) The internal combustion engine according to claim 9, wherein the ECU is further configured to: compare said relative humidity with a first threshold of said relative humidity and in case said relative humidity is above said first threshold; and adjust an exhaust gas flow into said portion such as to reduce the relative humidity. ### Claim 15 (depends on 14) The internal combustion engine according to claim 14, wherein the ECU is further configured to: define a second threshold of said relative humidity, said second threshold lower than said first threshold; and adjust the exhaust gas flow into said portion to reduce the relative humidity below said second threshold. ### Claim 16 (depends on 14) The internal combustion engine according to claim 14, wherein the ECU is further configured to regulating a ratio of exhaust gas flow circulating in a High Pressure EGR (HPE) conduit with respect to the exhaust gas flow circulating in the Low Pressure EGR (LPE) conduit. ### Claim 17 An apparatus for estimating a relative humidity in an intake line of an internal combustion engine provided with an intake manifold connected to the intake line, an exhaust line, and a Low Pressure EGR (LPE) conduit that fluidly connects the exhaust line to a connecting point of said intake line, said apparatus comprising: means for calculating specific humidity in the exhaust line, as a function of an O2 concentration in said exhaust line; means for determining an ambient specific humidity; means for calculating a second specific humidity in a portion of the intake line comprised between said connecting point and said intake manifold, as a function of a flow of external air entering into said intake line, a flow of exhaust gases coming from said Low Pressure EGR (LPE) conduit, the specific humidity in said exhaust line and the ambient specific humidity; and means for calculating the relative humidity in said portion of the intake line, as a function of the specific humidity thereof. ### Claim 18 (depends on 17) The apparatus according to claim 17, further comprising means for measuring the O2 concentration in said exhaust line. ### Claim 19 (depends on 18) The apparatus according to claim 18, wherein the means for measuring is a lambda sensor. ### Claim 20 (depends on 17) The apparatus according to claim 17, wherein the specific humidity and the relative humidity in said portion of the intake line are calculated upstream of a compressor. ### Claim 21 (depends on 17) The apparatus according to claim 17, where the specific humidity and the relative humidity in said portion of the intake line are calculated downstream of a charge air cooler. ### Claim 22 (depends on 17) The apparatus according to claim 17, wherein the estimating of the relative humidity in said portion of the intake line is performed on a basis of a map correlating ambient humidity to ambient temperature. ### Claim 23 (depends on 17) The apparatus according to claim 17, further comprising: means for comparing said relative humidity with a first threshold of said relative humidity and, in case said relative humidity is above said first threshold; and means for adjusting an exhaust gas flow into said portion such as to reduce the relative humidity therein. ### Claim 24 (depends on 23) The Apparatus according to claim 23, wherein a second threshold of said relative humidity is defined that is lower than said first threshold, and wherein the exhaust gas flow into said portion is adjusted such as to reduce the relative humidity therein below said second threshold. ### Claim 25 (depends on 23) The apparatus according to claim 23, wherein adjusting a gas flow into said portion of the intake line comprises regulating a ratio of exhaust gas flow circulating in a High Pressure EGR (HPE) conduit with respect to the exhaust gas flow circulating in the Low Pressure EGR (LPE) conduit.