Control of injection pressure for high pressure direct injection systems
A computer-implemented method for controlling direct injection of hydrogen fuel into an engine cylinder of a vehicle from a hydrogen tank via an injector system. The method includes determining a present hydrogen pressure in the hydrogen tank; determining a present requested engine torque and speed; determining a target injection pressure for injecting hydrogen into the engine combustion chamber using a model the target injection pressure is the injection pressure that, according to the model, minimizes the mechanical work of the compressor, that provides an in-cylinder pressure sufficient for the engine to provide the requested engine torque and speed, that provides NOx emission below a predetermined maximum NOx emission level, and that reduces engine fuel consumption, and adjusting the injector pressure according to the determined target injection pressure.
1. A computer-implemented method for controlling direct injection of hydrogen fuel into an engine cylinder of a vehicle from a hydrogen tank via an injector system, the method comprising:
determining a present hydrogen pressure in the hydrogen tank;
determining a present requested engine torque and speed;
determining a target injection pressure for injecting hydrogen into the engine combustion chamber using a model that includes at least:
a mapping of engine fuel consumption as a function of injection pressure;
a mapping between NOx emission as a function of injection pressure,
a mapping of in-cylinder pressure as a function of engine torque and speed;
a mapping of compressor mechanical work required to eject and compress hydrogen from the hydrogen tank as a function of injection pressure;
wherein, the target injection pressure is the injection pressure that, according to the model, minimizes the mechanical work of the compressor, that provides an in-cylinder pressure sufficient for the engine to provide the requested engine torque and speed, that provides NOx emission below a predetermined maximum NOx emission level, and that reduces engine fuel consumption,
wherein the method further comprises:
adjusting the injector pressure according to the determined target injection pressure.
2. The computer-implemented method according to claim 1 , wherein each mapping has an associated weighting factor to adjust the relative importance between the maps, at least two of the weighting factors being different from each other.
3. The computer-implemented method according to claim 1 , wherein the model includes assigned boundaries for each mapping.
4. The computer-implemented method according to claim 1 , wherein the model further includes a mapping between a diesel pressure used for hydrogen ignition and injection pressure, wherein a further constraint for determining the target injection pressure is set by a required diesel pressure.
5. The computer-implemented method according to claim 4 , wherein a further constraint is the hydrogen injection pressure is lower than the required diesel pressure.
6. The computer-implemented method according to claim 1 , comprising determining a present engine aftertreatment system temperature, wherein when the method is only operative when the engine aftertreatment system temperature exceeds a threshold indicating that the engine aftertreatment system is operative.
7. The computer-implemented method according to claim 1 , comprising determining that the pressure in the hydrogen tank is below a pressure threshold, and only use the model for determining the target injection pressure when the pressure in the hydrogen tank is below a pressure threshold.
8. The computer-implemented method according to claim 7 , wherein the pressure threshold is the in-cylinder pressure.
9. The computer-implemented method according to claim 1 , wherein the model includes a self-learning algorithm configured to adapt the injector pressure based on the amount of fuel in the tank.
10. The computer-implemented method according to claim 1 , wherein the model is configured to collect data of compressor usage, and to further adapt the injector pressure based on average usage of the compressor.
11. The computer-implemented method according to claim 1 , wherein the target injection pressure is the injection pressure that provides the lowest amount of fuel needed to fulfil an engine torque request with the lowest efficiency loss in a compressor providing the injection pressure.
12. The computer-implemented method according to claim 1 , wherein the model is predetermined and loaded on a memory of the vehicle.
13. The computer-implemented method according to claim 1 , wherein the target injection pressure depends on a given driving condition of the vehicle.
14. The computer-implemented method according to claim 1 , wherein adjusting the injector pressure is performed by controlling an operation of a compressor arranged to control the injector pressure.
15. A control unit for controlling direct injection of hydrogen fuel into an engine cylinder of a vehicle from a hydrogen tank via an injector system, the control unit being configured to perform the steps of the method according to claim 1 .
16. An injector system for direct injection of hydrogen into an engine cylinder of a vehicle from a hydrogen tank, the system comprising:
an injector;
a hydrogen tank connected to the injector with a transfer line to supply hydrogen gas to the injector, and
a control unit according to claim 15 .
17. A vehicle comprising the injector system according to claim 16 .
18. A computer program product comprising program code for performing, when executed by the processor device, the method of claim 1 when the program is run on a computer.
19. A non-transitory computer-readable storage medium comprising instructions, which when executed by a processor device, cause the processor device to perform the method of claim 1 .