Ceramic vs Metal Engines

 
 

THE METAL ENGINE:

  1. Metals (such as iron, steel and aluminium) lose their useful strength well below 1000C.
  2. Metals are also good thermal conductors.
  3. Because fuel combustion is a chemical process requiring high temperatures to be effective, making an IC engine out of a metal needs compromises.
  4. One compromise is to have a water jacket cool the IC engine. Cooling and operating the metal engine at lower temperatures reduces combustion efficiency.
  5. Furthermore the water jacket around the metal engine sucks valuable heat from the combustion chamber due to the thermally conductive metal combustion wall. This reduces combustion efficiency even further.
  6. The result of burning fuel at temperatures lower than 1000C is incomplete combustion which leads to the production of toxic products (such as carbon monoxide).

The water jacket also creates and maintains a cool flame-quenching zone on the inner wall of the metal combustion chamber. This causes the flame front to be doused and extinguished as it approaches the cool combustion chamber wall, a process known as wall quenching (References 1,2,3,4,5). This creates a pool of unburnt fuel at the metal combustion chamber wall.

This pool of unburnt fuel is expelled into the exhaust which is an regrettable waste of expensive fuel. This unburnt fuel is burned in the catalytic converter to reduce pollution.

Such effects reduce engine thermal efficiency by about 60% of the energy contained in the fuel [Reference 6] .

THE CERAMIC ENGINE:

  1. Most ceramics can operate at temperatures well over 1000C.
  2. At temperatures over 1000C fuels burn more completely. 
  3. When fuels burn completely the final combustion products are carbon dioxide and water.
  4. Carbon dioxide and water will partially mix to form carbonic acid which can be absorbed by calcium oxide to form calcium carbonate.
  5. Calcium carbonate can be used as a fertiliser.
  6. A ceramic engine would not need water cooling so no heat would be sucked out of the combustion chamber by a water jacket.
  7. Because zirconia ceramics are thermal insulators an Internal Combustion Engine made out of zirconia ceramic would keep the heat inside the combustion chamber to burn fuel more completely.
  8. No wall quenching of fuel would occur due to the hot inner walls of the zirconia ceramic engine.

In the early 1990s NASA scientists [References 7, 8] found that a zirconia ceramic thermal insulating layer on the inner wall of a metal combustion chamber of a Rotary Engine reduced heat loss resulting in a more complete combustion of fuel [see also Reference 9].

Therefore CRE’s near-adiabatic Ceramic Rotary Engine should (A) be more efficient, (B) be a lot smaller and yet more powerful, (C) be smoother running and (D) be cleaner burning and emitting less pollutants. The Ceramic Rotary Engine’s high temperature capability should enable the use of a greater variety of renewable fuels thus reducing US dependence on foreign sources of fossil fuels.

This means:

  1. The Ceramic Rotary Engine could maintain the pre-eminence of the Internal Combustion Engine for years to come replacing the metal engine in the huge worldwide market for engines. In 2001 it was worth $235 billion and now possibly a lot more.
  2. The Ceramic Rotary Engine’s high temperature capability should enable the use of a larger variety of renewable fuels (such as cellulosic biofuels) offering the possibility of reducing US dependence on foreign sources of fossil fuels.

References: (1) N.Ishikawa PhD Thesis “Studies of Wall Flame Quenching and Hydrocarbon Emissions in a Model Spark Ignition Engine”, Lawrence Berkeley National Laboratory, University of California, USDOE Contract #W7405-Eng-48, August 1978 https://escholarship.org/content/qt9zq5h4w8/qt9zq5h4w8.pdf

(2) M Turcios “Effects of cold wall quenching on unburned hydrocarbon emissions from a natural gas HPDI engine” 2011, https://www.academia.edu/1284176/Effects_of_cold_wall_quenching_on_unburned_hydrocarbon_emissions_from_a_natural_gas_HPDI_engine

(3) M. Sumanth & S. Murugesan “Experimental Investigation of Wall Wetting on Hydrocarbon Emissions in Internal Combustion Engines”, IOP Conf. Ser.: Mater. Sci. Eng.577 012029, 2019 https://iopscience.iop.org/article/10.1088/1757-899X/577/1/012029/pdf

(4) Toyota Automotive Technical Training Series, Engine Performance, OBD-II, h55 Emission#1 – Chemistry of Combustion, Page 5

(5) NPTEL, IIT India Lectures https://nptel.ac.in/content/storage2/courses/112104033/lecture8/8_2.htm

(6) US Dept of Energy [Source: http://www.fueleconomy.gov/feg/atv.shtml].

(7) H.E. Sliney “Composite Bearing and Seal Materials for Advanced Heat Engine Applications to 900C”, NASA Lewis Research Center & US-DOE Inter Agency Agreement DE-A101-85CE50162, August 1990  https://www.osti.gov/servlets/purl/6196168

(8) P.S. Moller  “Evaluation of Thermal Barrier and PS200 Self-Lubricating Coatings in an Air-Cooled Rotary Engine”, NASA Lewis Research Center Contract NAS3-26309, March 1995  https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950016805.pdf

(9) Poola et al “Performance of thin ceramic-coated combustion chamber in a two-stroke SI engine” 1994  https://www.osti.gov/servlets/purl/10194664