# US 9,518,518 B2 · Dual fuel common rail transient pressure control and engine using same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,518,518 B2 - Document ID: US9518518B2 - Status: Granted - Kind: B2 - Application number: 13/866,303 - Filed: 2013-04-19 - Published: 2014-10-23 - Granted: 2016-12-13 - Earliest claimed: 2013-04-19 - Assignees: Caterpillar Inc. - Applicants: Caterpillar, Inc. - Inventors: Dana R. Coldren; Steven Thomas Grant; Frank Lombardi; Daniel R. Puckett - Web page: https://patentgrep.com/patent/US9518518B2 ## 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 19/0694: {operating with a plurality of fuels} - F02D 41/0027: {the fuel being gaseous (non-electrical control F02D19/02)} - F02D 41/3836: {Controlling the fuel pressure} - F02D 19/0605: {to adjust the fuel pressure or temperature} - F02D 19/061: {by controlling fuel injectors} - F02D 19/10: peculiar to compression-ignition engines in which the main fuel is gaseous - F02D 41/3845: {by controlling the flow into the common rail, e.g. the amount of fuel pumped} - F02D 41/403: {with pilot injections} - F02D 2041/3881: {with multiple common rails, e.g. one rail per cylinder bank, or a high pressure rail and a low pressure rail} - F02D 2200/0602: Fuel pressure - Y02T 10/30: Use of alternative fuels, e.g. biofuels - 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 A compression ignition engine is fueled from common rail fuel injectors that predominately inject natural gas fuel that is compression ignited with a small pilot injection of liquid diesel fuel. Before and after a rapid load loss transient, the liquid and gaseous rail pressures are controlled toward respective pressures based upon engine speed and load. During the transient, the liquid rail pressure is controlled relative to the gas rail pressure in order to maintain the liquid rail pressure greater than the gas pressure during the transient to avoid migration gaseous fuel into the liquid fuel side of the system. ## Claims ### Claim 1 A method of operating an engine comprising the steps of: injecting gaseous fuel and liquid fuel directly into an engine cylinder from a gaseous nozzle outlet set and a liquid nozzle outlet set, respectively, of a fuel injector; compression igniting the injected liquid fuel to ignite the gaseous fuel; inhibiting migration of gaseous fuel into liquid fuel within the fuel injector by maintaining a liquid rail pressure greater than a gas rail pressure; the inhibiting step includes executing a first rail pressure control algorithm before and after a transient, and executing a second rail pressure control algorithm during the transient; initiating the transient by changing from a high fuel demand state of a first speed and load to a low fuel demand state of a second speed and load. ### Claim 2 (depends on 1) The method of claim 1 wherein execution of the first rail pressure control algorithm includes: controlling a liquid rail pressure toward a first predetermined target pressure based upon the first engine speed and load, and controlling a gaseous rail pressure toward a first gas pressure that is lower than the first predetermined pressure prior to the transient; and controlling the liquid rail pressure toward a second predetermined target pressure based upon the second engine speed and load, and controlling the gaseous rail pressure toward a second gas pressure that is lower than the second predetermined pressure after the transient; and execution of the second rail pressure control algorithm includes: controlling the liquid rail pressure toward a transient target pressure that equals the gas rail pressure plus a bias pressure, and controlling the gaseous rail pressure toward the second gas pressure during the transient. ### Claim 3 (depends on 1) The method of claim 1 includes a step of closing a shut off valve fluidly positioned between a gaseous fuel rail and a gaseous fuel supply system during the transient. ### Claim 4 (depends on 1) The method of claim 1 including a step of injecting gaseous fuel and liquid fuel into less than all of a plurality of engine cylinders in at least one engine cycle during the transient. ### Claim 5 (depends on 1) The method of claim 1 wherein each liquid injection event during the transient corresponds to a predetermined minimum injection quantity; and allocating a remainder of an engine fuel demand to injection of gaseous fuel during the transient. ### Claim 6 (depends on 1) The method of claim 1 including a step of avoiding venting gaseous fuel from a gaseous fuel rail to atmosphere during the transient. ### Claim 7 (depends on 6) The method of claim 6 wherein execution of the first rail pressure control algorithm includes: controlling a liquid rail pressure toward a first predetermined target pressure based upon the first engine speed and load, and controlling gaseous rail pressure toward a first gas pressure that is lower than the first predetermined pressure prior to the transient; and controlling the liquid rail pressure toward a second predetermined target pressure based upon the second engine speed and load, and controlling gaseous rail pressure toward a second gas pressure that is lower than the second predetermined pressure after the transient; and execution of the second rail pressure control algorithm includes: controlling the liquid rail pressure toward a transient target pressure that equals the gas rail pressure plus a bias pressure, and controlling the gaseous rail pressure toward the second gas pressure during the transient. ### Claim 8 (depends on 7) The method of claim 7 includes a step of closing a shut off valve fluidly positioned between a gaseous fuel rail and a gaseous fuel supply system during the transient. ### Claim 9 (depends on 7) The method of claim 7 including a step of injecting gaseous fuel and liquid fuel into less than all of a plurality of engine cylinders in at least one engine cycle during the transient. ### Claim 10 (depends on 7) The method of claim 7 wherein each liquid injection event during the transient corresponds to a predetermined minimum injection quantity; and allocating a remainder of an engine fuel demand to injection of gaseous fuel during the transient. ### Claim 11 An engine that comprising: an engine housing that defines a plurality of cylinders within which a plurality of respective pistons reciprocate to define a compression ratio greater the 14:1; a gaseous fuel common rail and a liquid fuel common rail fluidly connected to each of a plurality of fuel injectors that each include a gaseous nozzle outlet set and a liquid nozzle outlet set positioned for direct injection into one of the cylinders; means, including electronic controller configured to execute a first rail pressure control algorithm to maintain a liquid rail pressure greater than a gas rail pressure before and after a transient, and execute a second rail pressure control algorithm to maintain the liquid rail pressure greater than the gas rail pressure during the transient, for inhibiting migration of gaseous fuel into liquid fuel within the fuel injector; wherein the transient includes changing from a high fuel demand state of a first speed and load to a low fuel demand state of a second speed and load. ### Claim 12 (depends on 11) The engine of claim 11 wherein the first rail pressure control algorithm is configured to control the liquid rail pressure toward a first predetermined target pressure based upon the first engine speed and load, and control the gaseous rail pressure toward a first gas pressure that is lower than the first predetermined target pressure prior to the transient; and configured to control the liquid rail pressure toward a second predetermined target pressure based upon the second engine speed and load, and control the gaseous rail pressure toward a second gas pressure that is lower than the second predetermined pressure after the transient; and the second rail pressure control algorithm is configured to control the liquid rail pressure toward a transient target pressure that equals the gas rail pressure plus a bias pressure, and control the gaseous rail pressure toward the second gas pressure during the transient. ### Claim 13 (depends on 11) The engine of claim 11 includes a shut off valve fluidly positioned between a gaseous fuel rail and a gaseous fuel supply system. ### Claim 14 (depends on 13) The engine of claim 13 wherein the second pressure control algorithm is configured to close the shut off valve during the transient. ### Claim 15 (depends on 11) The engine of claim 11 wherein the second pressure control algorithm is configured to inject gaseous fuel and liquid fuel into less than all of a plurality of engine cylinders in at least one engine cycle during the transient. ### Claim 16 (depends on 11) The engine of claim 11 wherein the second pressure control algorithm is configured to avoid venting gas from a gaseous fuel rail to atmosphere during the transient. ### Claim 17 (depends on 16) The engine of claim 16 wherein the first rail pressure control algorithm is configured to control a liquid rail pressure toward a first predetermined target pressure based upon the first engine speed and load, and control a gaseous rail pressure toward a first gas pressure that is lower than the first predetermined pressure prior to the transient; and configured to control the liquid rail pressure toward a second predetermined target pressure based upon the second engine speed and load, and control the gaseous rail pressure toward a second gas pressure that is lower than the second predetermined pressure after the transient; and the second rail pressure control algorithm is configured to control the liquid rail pressure toward a transient target pressure that equals the gas rail pressure plus a bias pressure, and control the gaseous rail pressure toward the second gas pressure during the transient. ### Claim 18 (depends on 17) The engine of claim 17 includes a shut off valve fluidly positioned between a gaseous fuel rail and a gaseous fuel supply system. ### Claim 19 (depends on 18) The engine of claim 18 wherein the second pressure control algorithm is configured to close the shut off valve during the transient. ### Claim 20 (depends on 17) The engine of claim 17 wherein the second pressure control algorithm is configured to inject gaseous fuel and liquid fuel into less than all of a plurality of engine cylinders in at least one engine cycle during the transient.