Topher925 said:
Propane makes a much better fuel additive then hydrogen. In ideal combustion, the hydrogen will never even be oxidized do to its hire ignition temperature.
Your efficiency doesn't come from burning hydrogen it comes from displacing nitrogen with oxygen. This means less losses at the throttle and less losses due to compression and heating of nitrogen gas which just absorbs heat.
Actually propane is a better primary fuel source. It is already completely gaseous so it does not need extra time to be vaporized like liquid fuels. But nothing ignites easier or burns faster than hydrogen.. Hydrogen is the smallest, lightest, and most reactive element that is why it is at the top left side of the periodic chart of the elements. Hydrogen ignites easier and burns many times faster than any other element. Adding hydrogen to an internal combustion engine is like adding charcoal lighter fluid to your Bar-B-Q, it gets things started faster. This was the conclusion of the JPL and NASA studies from the 70's. Both studies concluded that adding small amounts of hydrogen reduces ignition lag and increases flame speed, which supports much leaner air/fuel mixtures. It does not have anything to do with adding or transferring additional energy to the combustion, the Second Law of Thermodynamics is therefore not being violated.
Without hydrogen injection gasoline is ignited by the spark plug several degrees before the beginning of the combustion/power stroke and is still burning when the piston reaches the bottom of this power stroke. The remaining unburnt fuel is then forced through the exhaust system to the EGR system to be recycled or to the catalytic converter to be incinerated (wasted). With hydrogen injection the combustion is much faster because the hydrogen burns quickly igniting the primary fuel from all sides at once. When proper engine timing and fuel mixture adjustments are made, the peak of the resulting pressure wave created by the combustion is higher (more energetic) and closer to the beginning of the power stroke because of this faster complete burn. Since most of the energy is released when the piston is near the top of the power stroke, more energy is able to be absorbed by the piston and converted to torque. Less energy is lost as heat through the exhaust. There is no unburnt fuel to be recycled by the EGR system or incinerated by the catalytic converter. A faster more efficient burn and less lost energy out the exhaust pipe means more power is converted to torque for power to the wheels, from equal amounts of energy input. This increase in over all system efficiency is the mechanism that creates increased fuel economy.
What the NASA study does show conclusively is that hydrogen injection does reduce ignition lag and increases flame speeds. Therefore, designing systems for optimum fuel efficiency requires the energy released from the combustion to be focused at the very beginning of the power stroke, where the piston has the maximum time and travel to absorb the energy of the resulting pressure wave. In their summary the NASA engineers concluded that this would be possible with fuel reforming systems controlled by a closed loop computerized control system. Unfortunately, they did not have these control systems readily available to them in 1977. But we have this type of technology in common use today. While, electrolysis based hydrogen injection may not be the answer to reach optimal fuel efficiencies, they are the easiest to produce and test. Significant fuel economy gains are being produced by individuals and companies around the world with well designed safe units. But, Steam reforming systems are where near optimal fuel efficiency gains are currently being realized.
Steam reforming systems utilize the waste heat from the exhaust system to produce hydrogen in higher concentrations than electrolysis and reform the gasoline (or any primary fuel) to smaller components that combust much faster. By using the hydrogen to reduce ignition lag to lowest possible time and reforming the fuel to be fully consumed in the shortest period possible, near optimal fuel efficiencies are being reached. At the same time greenhouse gas and hydrocarbon emissions are greatly reduced. While most of the steam reformer systems available are using gasoline, it has been shown that some alternative fuels work even better. Fuels that contain large amounts of water work the best, with the added advantage that they do not require any additional storage/delivery system for water. The water to produce hydrogen and steam for the reforming process is available directly from the fuel.