1. Technical Field
The present disclosure relates to multiple-cylinder internal combustion engines having a high-pressure common rail fuel system.
2. Background Art
High pressure common rail fuel systems typically include a high pressure fuel pump that delivers fuel to a fuel rail associated with a group of cylinders. The primary purpose of the fuel rail is to maintain sufficient fuel at the required pressure for injection while distributing fuel to the injectors, which all share fuel in the common rail. The rail volume acts as an accumulator in the fuel system and dampens pressure fluctuations from the pump and fuel injection cycles to maintain nearly constant pressure at the fuel injector nozzle.
Fuel system designs can be quite complex and are dependent upon a variety of considerations including connections or fittings to the fuel pump and injectors, connection points for the pressure sensor and regulator, and appropriate sizing to function as an accumulator. In “V” configuration engines, the high pressure fuel pump is often connected to both left and right common rails with each fuel rail associated with a corresponding cylinder bank. A pressure sensor and a pressure or volume control valve are used for closed loop feedback control of the rail pressure in response to commands from an engine or vehicle controller.
When the fuel injectors are actuated to inject fuel into the cylinder, a pressure wave travels from the injector inlet back through the high pressure lines or pipes to the associated fuel rail. This pressure wave may adversely affect the pressure control as well as the accuracy of the quantity of fuel delivered in a subsequent injection for the same cylinder for multiple injections per combustion cycle, and/or for subsequent cylinders in the firing order. Variations in fuel injection quantity and/or timing make it difficult to achieve desired emissions and performance goals. The high accuracy and small tolerances in injection quantity may require an appropriate volume in the fuel system to reduce pressure impulses from the high pressure fuel pump.
Package requirements have also become increasingly important as components are added and/or sized for increased performance, reliability, durability, and fuel economy while reducing emissions over the lifetime of the engine. Particularly for V-configuration diesel engines having a common rail system, multiple rails, fuel lines and connections present challenges for robustness to leaks while maintaining manufacturability.