Building a Better Mouse Trap: Extending the Life of the Internal Combustion Engine

Part 3 - Making the First Jetfire Power Metal Engine

In Part 1 (Introducing Jetfire) & Part 2 (The Benefits of Jetfire Power) I gave an overview of the method patented by MSU and Jetfire Power LLC for extending the operating range of Turbulent Jet Ignition. This method enables significant efficiency improvements through robust combustion of very dilute mixtures for a range of fuels. In this article I will touch on the first execution of Jetfire Power in a “metal” single-cylinder test engine.

For those not familiar with engine development, combustion systems are typically proven out with a “single cylinder” engine configuration. The results are then evaluated and used to either adjust the design, or support going to the next step of building a multi-cylinder version.

For Jetfire Power, the single cylinder executions to date have all been “optical” engines. These setups allow high speed photographs to be taken of the combustion process from the piston’s perspective. Their limitation, however, is that they can only run for a minute or two.  A metal engine can run longer test cycles with varying loads and speeds. This is a needed next step in the progression of Jetfire Power to a commercial application.

If you ever used a Brigs & Stratton powered lawn mower or mini-bike, or ridden on a Norton motorcycle, you know that a single cylinder engine is not the smoothest engine. Even a Harley with two cylinders is not very smooth… A research single cylinder engine typically will have large flywheels, and balance shafts to address primary and secondary vibrations. 

The result is that a research “single cylinder engine” is a massive unit – not what you expect when you think of a single cylinder lawn mower engine… the picture below shows a full setup in MSU’s engine lab. The short block is typically reused or modified with different piston, rod, and stroke combinations. It’s the cylinder head where the primary research takes place!

The block assembly alone, pictured below, weighs 200 kg! 

The balancing system has both primary (first order) and secondary (second order) balancers, pictured below.

The Jetfire Power technology is contained in the cylinder head. As starting point, MSU leveraged the combustion system from General Motors's 2.0L L4 Turbo “LTG” engine. GM provided MSU with a CAD file for a "single cylinder LTG head", and MSU made the necessary design changes to incorporate the Jetfire Power cartridge (see image below). This patented system houses the sparkplug (on the right side), a pre-chamber fuel injector (on the left side), and an air purge valve (in the middle with the red valve spring). A total of four “single cylinder heads” were fabricated for the Jetfire experiments. Funding for this activity largely came from MTRAC (Michigan Translational Research & Commercialization).

As shown in the figure below, the cartridge is integrated into the combustion chamber through the existing LTG sparkplug location (top of combustion chamber, between the intake and exhaust valves). The portion of the cartridge that protrudes into the combustion chamber has tiny holes which deliver the reacting jets, which ignite the main chamber.

The images below are top views of the Jeftire Power metal cylinder head. The air purge valve is operated off the intake camshaft. MSU’s modifications included changes to the intake camshaft (adding a lobe) and respacing the camshaft bearings. MSU also revised the cylinder head above the combustion chamber to allow the Jetfire Power cartridge to be installed in the valley between the two camshaft housings. Air and fuel supplies were also plumbed to the Jetfire Power cartridge. 

The Jetfire Power metal engine was completed in early March but has not had the chance to be run in MSU’s engine lab due to Covid-19 campus closures. It is expected to start running before the end of July. Data will be collected to confirm fuel consumption, emissions, and maximum EGR levels over a range of loads, speeds, and air/fuel ratios. Funding for the tests is being provided by Aramco. 

Technical results should be available in the next 6 – 8 weeks, and the subject of a subsequent post. In the meantime, please feel free to contact me directly with any questions at [email protected]