This article focuses on aspects of an onboard fuel-distilling system aims to curb the belch of hydrocarbons from a cool starting engine. According to an expert, feeding an engine high-volatility fuel during warm-up can halve the hydrocarbon emissions during a 30-minute drive. Ronald Mathews, along with Rudy Stanglmaier, a former University of Texas Austin doctoral student now with the Southwest Research Institute in San Antonio, and two Ford engineers, Wen Dai and George Davis, have patented an on-board distillation system that can refine fast-evaporating species from fuel while the engine is running and set aside the product as a reserve to be used at start-up. Among the key elements of the system is a level sensor in the reserve tanks. If the reserve falls too low, a control system in the engine central processing unit will trigger the distillation while the engine is running warm. The research for the technology, called the onboard distillation system, was supported in part by the Texas Advanced Technology Program, with Ford underwriting the patent application process.
A team of engineers from the University of Texas and Ford has designed a way to take some of the sting out of a cold engine.
Before an engine warms up, its exhaust is rich with unburned hydrocarbons and other unwanted emissions. That's because hydrocarbon fuel has to evaporate before it burns, and a cool engine is no great place to vaporize liquids. At the same time, the catalytic converter hasn't heated up enough to do its job, either.
According to one of the researchers, Ronald Matthews, the Carl J. Eckhardt Fellow of Mechanical Engineering at the University of Texas in Austin, gasoline consists of different species, and some of them, generally consisting of molecules with five or fewer carbon atoms, evaporate more readily than others. The new technology takes advantage of the difference in volatility.
Even at an outdoor Summer temperature as high as 27°C-that is, when the engine valves are 80°Fonly about 20 percent of the gasoline injected onto an engine's intake valves vaporizes and powers the engine, Matthews said.
Extra Fuel Needed
The low rate of evaporation requires extra fuel to feed the engine. And the lower the temperature falls, the more fuel has to be applied and wasted, and the longer the engine takes to warm up.
The unburned fuel puddles in the intake manifold. It will eventually evaporate when the engine gets warm, but then it won't provide power; it becomes a significant part of the engine's emission of unburned hydrocarbons. And curbing the emissions, rather than saving gasoline, is the primary aim of the research.
At 27°C, it's comfortable to go to the beach, and it takes about a minute for an engine to warm up to the point where it will evaporate fuel for efficient combustion, Matthews estimated. It may not seem like such a long time, until it is multiplied by every cold start of every engine in the world.
If the more volatile species of gasoline could be kept in reserve for use at start-up, fewer hydrocarbons would enter the atmosphere.
A dual fuel system is most probably impractical. As consumers to keep their radiators full of water and their tires full of air, much less ask them to fill with two fuels at the gas station."
Matthews, along with Rudy Stanglmaier, a former UT Austin doctoral student now with the Southwest Research Institute in San Antonio, and two Ford engineers, Wen Dai and George Davis, have patented an on-board distillation system that can refine fast-evaporating species from fuel while the engine is running and set aside the product as a reserve to be used at start-up.
Controlling the System
Among the key elements of the system is a level sensor in the reserve tank. If the reserve falls too low, a control system in the engine CPU will trigger the distillation while the engine is running warm.
When the process begins, valves at the end of the fuel rail direct some of the fuel to the distiller. The fuel is heated to a predetermined temperature to evaporate the most volatile compounds. Those vapors are captured and eventually sent to reside as liquid in a reserve tank.
All the hardware together is expected to add about 2 kg to the weight of the engine.
The release of unburned hydrocarbons is very intense during the warmup of an engine. Using the more volatile fuel at start-up can cut hydrocarbon emissions by as much as 50 percent over a 30-minute drive. It is also expected to reduce emissions of exhaust toxics-benzene, 1,3-butadiene, formaldehyde, and acetaldehyde by 80 percent.
Matthews said that the team so far has experimented with E85, a mix of 85 percent ethanol and 15 percent gasoline. If anything, working with 100 percent gasoline will be easier.
To rapidly separate its most volatile fractions, E85 must be heated to somewhere around 70°C. Gasoline will yield a high-volatility reserve after heating to only 50°C, Matthews said.
"Ethanol is very corrosive," he added. That trait means current prototypes must be made of materials that will stand up to the corrosion. Gasoline will allow the manufacture of parts out of cheaper materials.
The current price of the system is about $400, built more or less one at a time to handle the ethanol. The team expects to bring the cost down to around $60 per unit in production.
The research for the technology, called the onboard distillation system, was supported in part by the Texas Advanced Technology Program, with Ford underwriting the patent application process.
Besides the contributions of its engineers to the project, Ford will supply a 2001 Lincoln Navigator as a platform for development of the distillation system for gasoline.
When the system is fully developed, the university and Ford are planning to license it to automakers and share the royalties.