[Vwdiesel] New engine

Mark Shepherd mark at shepher.fsnet.co.uk
Thu Apr 14 21:20:08 EDT 2005

This more detailed description was also on the site.
so far I only have one question:
Does preheating the air through the heat exchanger  have any increased benefit  over using a turbo to add more air in?

StarRotor engine

                   In 1876, Germany's Nikolaus Otto developed the four-stroke internal combustion engine; it is the preferred engine for automotive transportation.   In 1892, Germany's Rudolph Diesel developed the diesel engine; it is the preferred engine for heavy-duty transportation, such as trucks, buses, and trains.  In 1873, America's Brayton developed an engine that predated the German engines; it is the preferred engine for high power density applications, such as turboprop planes and jets.

            Recently, the traditional roles of these engines are being challenged.  For example, General Motors is experimenting with hybrid diesel/electric power plants with the objective of obtaining 80 mpg in full-size automobiles.  Honda and Toyota currently sell (at a loss) hybrid-powered compact cars that obtain about 70 mpg.  Daimler-Chrysler has spent about $1 billion developing fuel-cell-powered automobiles with the intent of lowering emissions and increasing efficiency.  General Motors has leased all-electric vehicles in selected U.S. cities.  Other makers are offering electric-powered vans.  In short, we are at a unique time in history where automobile companies are rethinking their power plants.  

            Although General Motors has had technical success achieving its 80-mpg goal, the cost of the hybrid power plant is too high to be economical, about $20,000. The system is very complex; it contains a small engine, an electric generator, an electric motor, and battery storage.  Similarly, fuel-cell-powered vehicles are complex; they require a fuel reformer, fuel cell, electric motor, and batteries.  The fuel savings from these complex systems cannot be economically justified.
      Recently, researchers at Texas A&M University have invented the StarRotor engine, which has the potential to achieve more than 80 mpg, with low emissions approaching those of fuel cells, at a cost approaching that of a conventional internal combustion engine ($2000 to $5000).  Being a close relative of jet engines, it has a very high power density, meaning it can  pack a lot of power into a light-weight package.  The StarRotor engine volume is about 20 to 75% of a conventional internal combustion engine, and its mass is about 20 to 40%.  (Note: The wide range depends upon the desired efficiency.)  The StarRotor engine has very few moving parts. The StarRotor engine can use any liquid or gaseous fuel, such as gasoline, diesel fuel, kerosene, alcohols, or methane.  Premium high-octane fuels have no benefit to a StarRotor engine, so the least expensive fuel grades can be employed.  

      The researchers at Texas A&M are not the first to consider Brayton engines for automotive power.  In the 1950s and 60s, Chrysler developed a Brayton engine for automobiles, but it had to operate at extremely high speeds making it expensive and slow to accelerate. Further, it could operate efficiently only over a narrow speed range, which is unsuitable for automotive applications.  The StarRotor engine overcomes these problems by employing a gerotor compressor/expander, rather than the traditional vane axial compressor/expander found in a jet engine.  The StarRotor engine operates at "normal" speeds (3,000 to 10,000 rpm).

        The StarRotor engine is designed with a slight clearance between the gerotors, resulting in low friction and low wear.  Consequently, the engine is expected to have an extremely long life, perhaps a million miles.  Also, it will require very infrequent oil changes, perhaps every 100,000 miles.  Because it has very few moving parts, it is expected to be very reliable and require very little maintenance.

        Because the StarRotor engine is perfectly balanced, there will be no engine vibrations.  It should have the smoothness of 12-cylinder engines, such as those found only in the most expensive luxury cars.  Further, the StarRotor engine will be very quiet, even without a muffler.

        The hybrid and electric automobiles employ regenerative braking in which the kinetic energy of the moving vehicle is stored in a battery during braking, rather than rejecting the kinetic energy as waste heat through friction brakes.  During braking, the StarRotor engine can store kinetic energy in the form of compressed air.  During start up, the engine operates from the compressed air giving it about a 30% power boost.  For example, an engine nominally rated at 130 hp will have 170 hp during startup, which is when the power is required.  A cold engine can be started using stored compressed air, thus eliminating the need for a starter motor and large battery, both of which are maintenance headaches.

       Because the StarRotor engine promises to require little maintenance, it is possible to consider a novel marketing concept in which the engine is leased, rather than sold.  The average driver has little interest in the automobile engine.  Most really do not want to own an engine; rather, they are only interested in the service it provides.  Most drivers are primarily interested in body style and interior furnishings and only become aware of their engine when it requires maintenance.  At this point, it becomes a hassle for the driver because he must arrange for alternate transportation during the repairs, which sometimes take more than one day to complete.  In contrast, if the driver leased the engine, rather than owning it, he would simply take his vehicle to the auto dealer where the broken engine would be replaced with a working engine, perhaps taking only 30 minutes to do the replacement.  Then, the engine repair becomes the responsibility of the automaker.    

      As described earlier, the StarRotor engine engine is very efficient.  By simply replacing conventional engines (15-20% efficiency) with a StarRotor engine, fuel economy will double or quadruple.  For example, a conventional luxury car getting about 25 mpg on the highway would get about 75 mpg.  A conventional economy car getting 40 mpg would get about 120 mpg.  Further efficiency gains can be achieved by reducing aerodynamic drag through streamlining the body, or simply smoothing the underside of the vehicle, as is done in GM's electric vehicle.  Reduced aerodynamic drag, plus low-rolling-resistance tires can increase fuel economy even further making it possible for a luxury car to achieve perhaps 100 mpg and an economy car to obtain perhaps 160 mpg.

     Although the discussion above has focused upon automotive applications, the StarRotor engine has many other uses, such as powering trains, trucks, buses, boats, planes, snow mobiles, and lawn mowers.  

     In addition, the StarRotor engine could be employed in distributed electric power applications. Currently, there are three major competitors for generating electricity: gas turbines, combined cycles, and fuel cells. 

     Gas turbines require a relatively low capital investment, but tend to be inefficient (20-35%) and are generally used only for supplying peak power.  

     Combined cycles have state-of-the-art efficiency (60%) by using the waste heat from a gas turbine to make steam for a conventional steam power plant. Because the combined cycle is so complex, it does not scale down very well, it requires large amounts of capital, and it is costly to maintain. 

     Fuel cells have low pollution and high efficiency (50-60%).  This technology is expensive because the fuel must be reformed to hydrogen, the fuel cells employ expensive membranes and catalysts, and the final power must be converted from direct current to alternating current. 

     The StarRotor engine offers the best of the technologies described above.  It has an efficiency comparable to the combined cycle and fuel cell, low pollution similar to the fuel cell, and capital and maintenance costs similar to a gas turbine.  The StarRotor engine can be scaled down to a size suitable for a small housing district, commercial facility, or even individual homes.   

     The StarRotor engine is a proprietary technology owned by Texas A&M University.  Patents have been filed to protect the intellectual property.  Important features have already been approved both by the US and PCT patent offices.

            Please address technical questions to           

            Professor Mark Holtzapple 
            Department of Chemical Engineering 
            Texas A&M University
            College Station, TX  77843-3122
            (979) 845-9708 (phone)
            (979) 845-6446 (fax)


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