Fuels Solutions

February 26, 2002

As we mentioned last month, our main focus this year is combustion and how to effectively apply new combustion techniques to low-cost, easy-to-construct turbines such as the Tesla design. This in no way constrains us to a strict Tesla system, but merely serves as a starting point for more efficient design strategies.

In order to obtain the best efficiencies from fuel to shaft horsepower we have to look at the entire process -- from fuel in its unburned, raw state, through the transforming of gas kinetic energy into mechanical power, and finally, the exit of hot gas from the machine and the recovery or loss of energy in the entire system.

First of all we have to decide on the combustion mechanism -- do we want a continuous burn or pulse burn? In previous discussions we finalized on pulse burn as a more efficient mechanism for reaching high velocity gas states with the lowest heat loss. A pulse burn mechanism is similar to the constant volume combustion model of the piston engine, rather than the constant pressure system of conventional turbines. While conventional turbines are higher than piston engines in horsepower per pound of engine, they are less efficient (in most applications) in terms of fuel efficiencies.

To obtain good pulse combustion we need an energetic fuel that will burn easily even at low temperatures. Since our operations are located in northern Michigan, we usually have a few months of cold temperatures -- useful for conducting certain cold condition tests.

In Photo A you can see a simple test bed for determining which fuels are best suited to our work. The equipment used was all off-the-shelf and easy for anyone to assemble. The main system consists of an air compressor driving a paint sprayer which atomized the test fluid, spraying it past a spark plug driven by a high voltage furnace coil.

Photo B shows another apparatus we dismantled from a fuel oil furnace. The main difference between the two devices is that the fuel oil gun uses a high pressure pump to drive liquid through a small nozzle for atomization. The paint sprayer uses medium- to low-pressure air to draw liquid from the tank by venturi vacuum, then forces it through an atomizing nozzle.

The advantage of the paint sprayer system is that some fuel/air premixing is done in the sprayer. The advantages of the fuel oil gun are compactness and lower power requirements. As we eventually move towards a final design, we'll use elements of both systems for best overall results.

Fuels

Some of the fuels we experimented with were:

• alcohols
• kerosene
• naphtha
• acetone
• toluene (xylene)
• fuel oil
• white gas (Coleman fuel)
• gasoline (motor fuel)
• soy oil
• mineral spirits

Besides testing these liquids as single component fuels, we also blended various combinations to establish a baseline of characteristics. For instance, the alcohols would not mix with the oil group -- including naphtha, gasoline and mineral spirits. We even tried the gasoline additives designed to remove water from your automobile fuel tank. Although the alcohol and water mix, they in turn do not mix with gasoline -- which is why your car doesn't always perform right.

Using the paint sprayer system, we tested all of the single and multi-component fuels for ignition, burn and smoke characteristics. Some preliminary results demonstrated that:

• Alcohol, acetone and toluene (xylene) would not ignite under cold conditions using our spark arrangement. 
• Kerosene, fuel oil, naphtha, gasoline, white gas, and mineral spirits all ignited easily but burned with more or less energy. 
• Soy oil burned easily in combination with kerosene, naphtha, mineral spirits, but also produced the most smoke.

Of all the components we tested, the overall winner was mineral spirits. Even though mineral spirits is a multi-component fuel with boiling points from 142 degrees C to 187 degrees C, it is more energetic than gasoline (motor fuel) -- which is a blend of hydrocarbons with boiling points from around 90 degrees F to about 435 degrees F. This witch's brew of white gasoline and industrial waste is not only expensive to produce, unstable in storage, mixed with 20% to 25% water during summer sales -- it is also part of the political haggling process in Washington to complicate the country with over 40 unique blends of fuel.

What we have discovered is that all of the price haggling and political intervention and control over motor fuel is really unnecessary. By shifting the country to a simple distillate fuel like mineral spirits, we can eliminate all the various blends of fuels -- which will result in lower prices starting at the cracking plants. To utilize more of the fuels base, simple blends of mineral spirits with kerosene and even soy (and other plant oils) will move the country very quickly towards energy independence.

Now comes the tricky part.

Gasoline piston engines, as they are designed today, do not work well with mineral spirits, fuel oil, or even pure alcohol. Petroleum distillates detonate too easily in today's engines, resulting in rapid destruction of the engine. Slowing down the burn to avoid detonation results in poor fuel economy (as much as 40% of the fuel in your tank is simply blown out the exhaust port), which is why catalytic converters are mandated -- to burn the wasted fuel.

This brings us to the next point. To utilize all of the energy in fuel we have to pre-process the fuel into a near 100% burnable state. Liquids do not burn -- only vapor or gas phase fuels burn! While carburetors and fuel injectors work to convert liquid fuels to vapor state, the fuel still acts as a quasi-liquid even in a hot cylinder.

The only way we can achieve near-perfect combustion is to start with a gas phase or gas state fuel. Photo C shows one of our primary stage components for liquid-to-gas state devices. It's operation is really quite simple; a close-fitting pipe is welded (gas-tight) around a smaller diameter threaded pipe. An inlet and outlet are welded to the outer pipe. As heat from an engine or combustor passes through the center (threaded) pipe, fuel is forced through the outer cavity, transforming it to a vapor/gas phase (dependent on the heat).

Photo D gives us a brief glimpse at a parallel development project in an early construction stage. This fuel processor is designed to convert any liquid-state hydrocarbon into a gas-phase fuel for use in any type of engine -- gasoline piston, diesel piston, all types of rotary & turbine engines, etc.

Well, that's it for this month. Next month we will feature a special test between a strict Tesla disk design versus a proprietary hybrid design of our own, using thin section winglets mounted between the disks. We'll also cover some of the inlet nozzle issues.

Anyone interested in learning more about our fuel processor will want to link over to our PNGinc site. 'Til next time -- keep the motive power revolution rolling!

Ken Rieli

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