Direct injected gas engine with variable gas pressure control apparatus and method of operation

Claim 1

A fuel system of a direct injected gas engine comprising: a source of pressurized gaseous fuel containing natural gas pressurized to at least about 1,000 psi; an injector arranged to inject fuel directly into a combustion chamber of an engine; a fuel control system controlling pressure of fuel supplied to the injector from the source, said fuel control system being responsive to engine load conditions to reduce the pressure of the fuel at light loads, compared to the pressure of the fuel at full load, and to increase the duration of pulses of the fuel at light loads, compared to the duration of pulses to supply a substantially equivalent quantity of gas at the full load gas pressure, wherein the fuel control system comprises a dome loaded gas pressure regulator and an electronic control module, said electronic control module being arranged to receive input signals relating to engine parameters and to provide output signals, to a control valve controlling a fluid of a hydraulic control loop, that determine the pressure of pulses of fuel supplied to the injector by the regulator.

Claim 12

A method of operating a fuel system of a direct injected gas engine comprising: providing a gaseous fuel at an initial pressure that meets maximum engine requirements at full load; monitoring engine parameters to detect when the engine is operating at less than fuel at an initial pressure that meets maximum engine requirements at full load; monitoring engine parameters to detect when the engine is operating at less than full load; controlling pulse duration and gas pressure of gas pulses injected into the engine during respective combustion cycles including extending the duration and lowering the pressure of pulses when the monitoring indicates the engine is operating at less than full load so that a substantially equivalent quantity of gas is injected meeting engine load requirements as compared to that delivered at the initial pressure whereby pulses of fuel at light loads are extended to a duration at least as long as a characteristic ignition delay period of the engine; and injecting the controlled gas pulses directly into an engine combustion chamber, without premixing with air, during respective combustion cycles, said injecting being initiated when the combustion chamber is under approximate maximum compression.

Claim 13

A method of operating a fuel system of a direct injected gas engine comprising: providing a gaseous fuel at an initial pressure that meets maximum engine requirements at full load; monitoring engine parameters to detect when the engine is operating at less than fuel at an initial pressure that meets maximum engine requirements at full load; monitoring engine parameters to detect when the engine is operating at less than full load; controlling pulse duration and gas pressure of gas pulses injected into the engine during respective combustion cycles including extending the duration and lowering the pressure of pulses when the monitoring indicates the engine is operating at less than full load so that a substantially equivalent quantity of gas is injected meeting engine load requirements as compared to that delivered at the initial pressure whereby pulses of fuel at light loads are extended to a duration at least as long as a characteristic ignition delay period of the engine; and injecting the controlled gas pulses directly into an engine combustion chamber, without premixing with air, during respective combustion cycles, said injecting being initiated when the combustion chamber is under approximate maximum compression.

Claim 15

A method of operating a fuel system of a direct injected gas engine, having a combustion chamber containing an ignition device, comprising: providing a gaseous fuel, that is a natural gas comprising methane, at an initial pressure of at least about 1,000 psi that meets maximum engine requirements at full load; monitoring engine parameters, including engine speed and pressure of fuel injected into the engine and developing a signal representing engine load, to detect when the engine is operating at less than full load; controlling pulse duration and gas pressure of gas pulses injected into the engine combustion chamber during respective combustion cycles including extending the duration and lowering the pressure of pulses when the monitoring indicates the engine is operating at less than full load so that a substantially equivalent quantity of gas is injected meeting engine load requirements as compared to that delivered at the initial pressure, such controlling of gas pulses being performed substantially in accordance with a gas control map relating gas pressure to engine speed and to engine load wherein gas pressure is (a) at a maximum at maximum engine speed and maximum engine load, (b) at a minimum at minimum engine speed and minimum engine load, and (c) gas pressure has intermediate levels between minimum and maximum engine speeds and between minimum and maximum engine loads; and injecting the controlled gas pulses directly into the engine combustion chamber, without premixing with air, during respective combustion cycles.

Claim 16

A method of operating a fuel system of a direct injected gas engine, having a combustion chamber containing an ignition device, comprising: providing a gaseous fuel, that is a natural gas comprising methane, at an initial pressure of at least about 1,000 psi that meets maximum engine requirements at full load; monitoring engine parameters, including engine speed and pressure of fuel injected into the engine and developing a signal representing engine load, to detect when the engine is operating at less than full load; controlling pulse duration and gas pressure of gas pulses injected into the engine combustion chamber during respective combustion cycles including extending the duration and lowering the pressure of pulses when the monitoring indicates the engine is operating at less than full load so that a substantially equivalent quantity of gas is injected meeting engine load requirements as compared to that delivered at the initial pressure, such controlling of gas pulses being performed substantially in accordance with a gas control map relating gas pressure to engine speed and to engine load wherein gas pressure is (a) at a maximum at maximum engine speed and maximum engine load, (b) at a minimum at minimum engine speed and minimum engine load, and (c) gas pressure has intermediate levels between minimum and maximum engine speeds and between minimum and maximum engine loads; and injecting the controlled gas pulses directly into the engine combustion chamber, without premixing with air, during respective combustion cycles.