SBIR-STTR Award

Dual Mode, Turbulent Jet Igniters (DM-TJI) are radially directed devices from a pre-chamber which ignite very lean or high-EGR mixtures in the main combustion system. The name Jetfire is trademark pending for the DM-TJI system. In this patented system, fuel and air in the pre-chamber and main chamber are independently controlled. A thermodynamic model has been calibrated using engine experiments conducted in Prototype 2 Jetfire single-cylinder engine. Using these calibrated simulations, we estimate a four-cylinder engine can achieve a brake thermal efficiency (BTE) of greater than 40% over an operating range of road speeds and 4-12 bar loads with a peak efficiency potential exceeding 45%. This engine could be a gasoline, diesel or JP-8 fueled engine as long as we can maintain efficient combustion. In the proposed Phase I effort, we will demonstrate a viable pathway for using JP-8 fuel in an engine with Jetfire ignition control. The proposed JP-8 configuration is viable for a gasoline-fueled engine, using gasoline more efficiently than current models and making it attractive for many commercial applications. The improved fuel economy of the Jetfire system will enhance Army capability, reduce fuel transportation costs and be an economically positive option

Experimental results have concluded that a Jetfire engine can successfully run on heavier F24/JP-8 based fuels and provide a substantial opportunity for reaching fuel efficiency milestones in both military and commercial applications. Detailed analysis has shown that properly mixed F24 distillates combined with proper cooling/heating conditions, and low compression ratios effectively maintain consistent combustion control and stability. The Jetfire engine testing as described in the Phase I effort, demonstrated very lean operating conditions all while managing engine knock and increasing fuel efficiency by more than 30% over a conventional stoichiometric small spark ignition gasoline fueled engine. Of greatest significance, this project demonstrates a methodology that can be implemented in a conversion kit that permits the use of JP-8/F24 fuel in a purpose modified spark ignition engine. Jetfire technology utilizes a conventional main chamber with an additional pre-chamber offering independent control of both fuel and air. Fuel is delivered to the pre-chamber using a standard fuel injector, spark is initiated using a standard spark plug, and pre-chamber air introduced via a poppet valve. Jetfire ignition facilitates knock-free operation while maintaining burn rates required for efficient combustion. In the Jetfire pre-chamber system, the mixed fuel-air charge is directly followed by spark-initiated combustion. As a result, reacting jets which issue from the pre-chamber ignite the main chamber charge via a six-port nozzle intermediate of the pre and main chambers. This Jetfire technology is unique to competitive technologies because of its ability to manage highly dilute fuel-air mixtures within the pre-chamber and its ability to ignite a highly dilute primary charge. In the Phase II effort, MMR will build a metal version of the optical engine configuration that was developed in Phase I. This engine will be capable of operating over a wide range of conditions including those required by Army missions as well as having wide spread civilian applicability. Additive manufacturing will facilitate implementation of the new cylinder head. Also, the refined additive manufacturing methods use in this project may provide a method to upgrade legacy engines in other Army applicaitons where parts are not readily available.