An insert for engine intake gaseous fuel mixing device. A body defines a longitudinal axis, leading end, trailing end, and exterior surface profile from the leading to the trailing end. Supports extend radially from the body, each support extending parallel to the axis to define separate longitudinal intake passages. The exterior surface profile of the body includes a nose section in which diameter increases from a minimum value at the leading end to a maximum value at a downstream end of the nose section. The nose section is followed by a flat section and a curved tapering section in which the profile converges toward the axis at an increasing rate from the flat section in a direction of the axis toward the trailing end. The diameter at the trailing end is at least 15 percent less than a maximum diameter of the body.

In certain embodiments, a PFI diffuser induction device may use toroidal vortex flow to thoroughly mix H.sub.2 and air in the intake runner and port of a H.sub.2 engine. When H.sub.2 enters a stream of air flow in the form of a toroidal vortex, it may tend to swallow the air into the vortex where a low-pressure region may be formed due to the swirling velocity of the vortex, which may be more effective that the typical mixing via conventional injection methods. Engine test measurements show remarkable improvements in engine combustion stability as well as engine efficiency and power output using a counterflow Toroidal Vortex Induction Diffuser to achieve high levels of fuel mixture homogeneity in combustion engines using hard-to-mix fuels like H.sub.2, CH.sub.3OH, C.sub.2H.sub.5OH and other gaseous and liquid fuels.

An air-fuel mixer includes a body having an inlet, an outlet, and an air passage therebetween. One or more fuel injectors are mounted to the body and positioned to inject fuel into the air passage with little or no space between the injector nozzles and the air passage. The fuel injectors may be inclined in an air-fuel mixer outlet direction whereby they inject fuel into the air passage with momentum in a direction of the outlet. Swirl guides are provided within the air passage. The air-fuel mixer may be installed between an intake manifold and an intercooler. The air-fuel mixer provides good mixing, low resistance to air flow, reduced fuel slip, and crisp responses to throttle up and throttle down commands.

The present invention pertains to a gas mixer for an internal combustion engine for mixing air with at least one admix gas, comprising a first duct segment having a first tube section and a first cone section, and a second duct segment having a second tube section and a second cone section. The first and second duct segments are stackable such that in a stacked state, a main gas conduit is formed by the first and second tube sections and an admix gas conduit is formed between the first cone section and the second duct segment. The present disclosure also pertains to a method for producing a gas mixer, comprising the steps of: for a predetermined mass flow of a gas to be admixed to air, calculating a flow cross section; machining at least one inner surface of an admix gas conduit such that at any position, the admix gas conduit comprises at least the calculated flow cross section; stacking two duct segments to provide the gas mixer. The present disclosure also pertains to a duct segment for being used in the gas mixer.