Engine with gaseous and/or liquid fuel injector

What is this patent about?

’158 is related to the field of multi-fuel internal combustion engines, specifically those capable of operating on both liquid fuels like gasoline and gaseous fuels like compressed natural gas. In such systems, managing the transition between fuel types is traditionally difficult, often resulting in combustion instability, increased emissions, or the need to temporarily shut down the engine. The background context involves optimizing fuel delivery hardware to allow for rapid, seamless switching between these two states without sacrificing engine performance or power output.

The underlying idea behind ’158 is leveraging the physical properties of fuel phases—specifically the buoyancy of gas relative to liquid—to facilitate faster transitions within a shared delivery path. By orienting the fuel injector so that its inlet faces downward toward the road surface, gaseous fuel naturally rises to the top of the fuel rail and into the injector inlet. This allows the engine to begin injecting gas even before the liquid fuel has been completely purged from the supply lines, using the pressure of the incoming gas to displace the remaining liquid.

The claims of ’158 focus on a control strategy for a dual-injector cylinder that triggers fuel transitions based on the injection rate threshold of a primary direct injector. Specifically, the method involves delivering liquid fuel through a direct injector while selectively switching a second port injector between liquid and gaseous states. The transition is not merely a manual choice but a dynamic response: switching to liquid fuel when the direct injector hits a limit and power is insufficient, or switching to gaseous fuel when the direct injector hits a limit and engine knock is detected.

In practice, the system maintains engine torque during these transitions by dynamically adjusting the pulse width of the direct injector. When the port injector is temporarily paused to purge the lines of a previous fuel type, the direct injector increases its output to compensate for the lost fuel mass. This load-balancing between the two injectors ensures that the driver perceives no change in power, while the hardware uses high-pressure gas to force residual liquid back through a pressure relief valve into the storage tank.

This approach differs from prior solutions that required redundant sets of injectors for each fuel type or suffered from long lag times during fuel purging. By utilizing a gravity-aware orientation of the fuel rail and injectors, the invention minimizes the volume of fuel that must be cleared before a new fuel type becomes effective. Furthermore, using the direct injector as a buffer to mask the transition period provides a level of combustion stability that traditional single-injector or non-compensated multi-fuel systems cannot achieve.