Engines may use Gasoline Direct Fuel Injection (GDI) systems to deliver fuel over a wide range of operating conditions to increase the combustion efficiency and decrease emissions. However, under certain operating conditions, vapor formation may occur in the fuel delivery system, which in turn may degrade engine combustion efficiency.
Various approaches have been used to decrease vapor formation. For example, in U.S. Pat. No. 7,438,051, a control strategy for decreasing the vapor in a fuel delivery system downstream of a high pressure pump is disclosed. In particular, the control strategy involves monitoring the response curve of a pressure regulator in the fuel delivery system to detect formation of vapor bubbles downstream of a high pressure pump, and subsequently adjusting the fuel delivery system to reduce the vapor in the fuel delivery system downstream of the high pressure pump.
However, the inventors herein have recognized several issues with the above approach. For example, the above approach takes mitigating action only after fuel vapor formation has occurred, and thus only after at least some degradation in combustion efficiency. Furthermore, vapor may form not only downstream of the high pressure pump, but also upstream of the pump. However, because of the positioning of the pressure regulator in the '051 reference, the pressure regulator's response curve provides no indication of such upstream vapor formation.
As such, in one approach, a fuel delivery system and method for an internal combustion engine are provided. A method for a fuel delivery system coupled to an engine is disclosed, the fuel delivery system including a lower pressure pump (LPP) fluidly coupled upstream of a higher pressure pump (HPP). The method may include during operation of both the HPP and LPP, adjusting operation of the LPP in response to pressure fluctuations at an inlet of the HPP.
Specifically, the inventors herein have recognized that pressure fluctuations at the inlet of the high pressure pump, specifically an amplitude of pressure pulsations within a certain frequency range, may be indicative of vapor formation, where a higher amplitude indicates less vapor formation, and vice versa.
In this way, the amplitude of fluctuation may serve as an indicator of vapor formation within or upstream of the higher pressure pump. Therefore, the output of the lower pressure pump may be decreased, thereby decreasing the energy consumed by the lower pressure fuel pump while decreasing the likelihood of fuel vapor development within the fuel delivery system. In particular, the method may decrease the wear on the higher pressure pump due to vaporization of fuel within and/or upstream the higher pressure pump (e.g. step-room). In some example, such as when an electronic return-less fuel system is used, the method may be implemented utilizing existing components, requiring no extra cost to implement.
It should be understood that the background and summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.