Daniel Convissor's Website

Vehicles

Stirling Auto Engine

The contract of the Mod I engine went to Mechanical Technology, Inc. [in Latham, NY.] The company's goals, as MTI vice president Gene Mannella explained to me are to achieve a 30 percent fuel economy advantage over equivalent spark-ignition engines, low exhaust emissions, and ability to use a variety of fuels with easy changeover.

Sealed-in hydrogen working fluid shuttles back and forth between hot and cold sides of adjacent cylinders. Combustion of almost any fuel in external chamber heats gas in tubes, causing expansion that drives pistons down. Gas contracts in water-jacketed cold side, adding negative pressure until increasing volume o compressed gas reverses piston motion. Regenerators, through which gas passes in both directions, trap heat as gas goes to cold side and return it on the way back. Cooling water surrounds both cylinder bottoms and regenerators, is circulated to large regenerators, is circulated to large radiator to maintain engine's high efficiency. Cylinders are paired to turn two crankshafts, which are geared together to power a single drive shaft.

Frankly, if they'd left the driving to me, I'd have waited for the car coming from our left to clear before pulling out of the driveway and onto the road. The timing and distance were just a bit tight. Besides, the engine under the hood of our car didn't even sound as if it were running.

But my driver... kicked down hard on the gas. I heard gravel spin out from under the tiers as we shot out of the driveway and across the road with a smoothly fluid sweep. Oddly enough, I still didn't hear much from the engine - - no exhaust roar, vibration, or other symptoms of a floorboarded takeoff.

But no oil is permitted inside the cylinders, how are the piston rings lubricated? "They're PTFE materials," Ernst said, using the chemical designation for the slippery material commonly called Teflon. "They run with no lube. A film builds up on the cylinder walls, and the rings don't wear. We've operated them for thousands of hours with no wear," he said.

If the problem is close to solution, what about the tow other difficulties caused by hydrogen's unique properties? The gas can also leak by diffusion, actually penetrating the metal structure by sneaking between the molecules. An apparent solution to this problem was stumbled upon when some impure gas found its way into MTI's lab. "When the hydrogen is doped with carbon monoxide or carbon dioxide, an oxide coating builds up on the walls of the working-gas chambers and passages," Ernst explained. Apparently these thin coatings are more effective hydrogen barriers than metal alone.

Unfortunately,... government cutbacks have placed the third phase of the NASA program in doubt Although the Mod I engine is well on its way to demonstrating all it was expected to and more, its planned successor, Mod II, is presently condemned to remain a "paper' engine. Perhaps a car manufacturer will pick up on it and carry on. If not, a great deal of successful research may languish half finished. After seeing the performance of the NASA Stirling at this stage, I'd hate to see that happen.

--E.F. Lindsley, "Stirling Auto Engine -- a lot of progress, but...," Popular Science, January 1983.

The front-wheel-drive TPC is powered by an aluminum three-cylinder, 0.8-liter (48.8 cu. in.) gasoline engine linked to a five speed transaxle.

GM has no plans to market the car. However, some of its features could show up in future vehicles.

--Charles Miller, "95-mpg Commuter Car From GM," Popular Science, January 1983.

EPA Test Results

Components (g/bhphr)            NGV Bus          EPA Stndrd. 1991

Hydrocarbons                      1.2               1.3
Carbon Monoxide                  10.6              15.5
Nitrogen Oxides                   1.4               5.0
Particulates                      0.02              0.1

At the Environmental Protection Agency, Charles Gray, director of the emission control technology division, said methanol could burn more cleanly if mixed with large amounts of air. Gasoline engines cannot run with such a rich air mixture, so engines converted to methanol do not allow optimum combustion conditions.

--Mathew Wald, "When Methanol Is in the Tank," New York Times, May 17, 1989.

Conversion involves installing three cylinders capable of holding 15 gallons of compressed natural gas, enough to drive 60 to 80 miles on city streets, within the daily range of a United Parcel truck in an urban area. The system requires regulators to reduce the pressure of the gas as it is fed first into with air and then into the truck's standard gasoline engine.

In the Brooklyn test, each of the 10 vehicles cost $3,000 to $3,500 to convert to natural gas, with the bulk of the cost paid by Brooklyn Union Gas, Mr DeGasperis said.

Natural gas costs about 25 percent less per mile than gasoline.

Based on its test program in Brooklyn, which began a year ago, United Parcel said use of natural gas significantly reduced emissions of the gases that cause smog. Emissions of carbon monoxide were reduced by 85 percent, nitrogen oxide by 25 percent, carbon dioxide by 23 percent and hydrocarbons by 13 percent.

--Richard Stevenson, "United Parcel to Alter Its Trucks In Los Angeles to Use Natural Gas," New York Times, July 11, 1990

The TEVan could increase the demand for EVs by more than 75% to 283,000 vans - - nearly 80% of all vans in the surveyed fleets.

--Electric Power Research Institute, 3412 Hillview Av., POB 10412, Palo Alto, CA., 94303. 415/855-2168.