User:OnionsAreNasty7/sandbox/Ceramic Engine

A ceramic engine is a theoretical engine made from technical ceramic material (engineered ceramics made to withstand extreme environments). The engine was a proof-of-concept popularized by successful studies in the early 1980s and 1990s. Under controlled laboratory conditions, ceramic engines outperformed metallic engines in terms of weight, efficiency, and performance. The plan for an all-ceramic engine was seen as the next advancement in future engine technology. However, ceramic engines have not entered the automobile market because of manufacturing and economic problems.

Although an all-ceramic engine is not viable, technical ceramics are still recognized for its beneficial properties. Currently, technical ceramics are reserved for minor components in engines and as thermal coating.

History
Research into more efficient diesel engines occurred after the 1970 Energy Crisis, resulting in a new market for fuel-efficient vehicles. A newly developed gas-turbine engine promised high thermal efficiency, but needed a material that could withstand 2,500°F temperatures. The high heat did not allow for readily available materials like metals, superalloys, and carbon composites to be used. As a result, government-funded research facilities from the United States, Japan, Germany, and the United Kingdom experimented with replacing metal with new ceramic material. Ceramic's high resistance to heat helped pave the way towards the first commercial use of gas-turbine engines. The Nissan Motor Company Ltd. produced the Nissan 300ZX, which was the first automobile to have a ceramic turbocharger (a component within an engine which helps increase energy efficiency). The successes of the gas-turbine engine led to the idea of an all-ceramic engine.

Predictions for an adiabatic turbo-compound engine (a theoretical heat-efficient engine) was seen as plausible with the use of technical ceramic material. A 1987 technical paper by Roy Kamo predicted the mass production of such engines to occur in the year 2000. However, these predictions are estimated with the belief that ceramics would overcome "the design methodology, manufacturing process, machining cost, and mass production quality control needed for high volume production."

Currently, the idea of an all-ceramic engine is not viable in mass production. Large ceramic parts, like a ceramic engine block, would be challenging to manufacture due to ceramic being brittle and stiff.

Technical Ceramic Material
Ceramic is a brittle material widely used in bricks, concrete, and pottery. However, Technical ceramics are a specialized ceramic that are engineered to withstand harsher environments and applications. Technical ceramics (also known as advanced ceramic) can be classified into two groups, oxidized and non-oxidized.

Oxidized ceramics are made with oxide fibers (a thin, threadlike structure) within a clay-mixture. The addition of these fibers help the ceramic in strength reinforcement and resistance to oxidation. Zirconia (ZrO2) is an oxidized ceramic with high thermal insulation and a compression resistance of 2000 M Pa (A unit of pressure). Zirconia was a popular choice of ceramic for ceramic engine experiments.

Non-oxidized ceramics exclude oxide fibers. The exclusion of the fibers allows for higher heat resistance, stronger load capacities, and less weight. Two examples of non-oxidized ceramics include silicon nitride (Si3N4) and silicon carbide (SiC). Both of these materials were considered within ceramic engines for being lightweight, heat-resistant, and tough.

Ceramic vs Metal
Technical ceramic materials have special properties that exceed metal. These properties include the following:


 * Strength
 * A Higher maximum service temperature. This allows for more combustions in the engine, which increases power output.
 * Ceramic has a lower density than most metals. The overall weight of a vehicle decreases, which means the vehicle can travel at faster speeds.
 * High wear resistance, less engine repairs.
 * Reduced friction which allows for less lubrication.

Theoretical Ceramic Engine
The following engine and its beneficial properties were seen as plausible with future improvements in technical ceramic material.

Adiabatic Turbocompound Engine
Note: An adiabatic process (from thermodynamics) is when no heat is gained or lost within a system. Therefore, the idea of an adiabatic engine refers to an engine where all chemical energy produced is converted into mechanical energy. However, this is not possible in the real world. Using the term "adiabatic" when referring to an engine is a misnomer. "Adiabatic" is only used to describe the pursuit towards a 100% heat-efficient engine.

The adiabatic turbocompound engine is a diesel engine with high heat efficiency. Three components are added to the engine to help minimize heat loss. These three components include a turbocharger, a turbine wheel, and insulated combustion chamber (where fuel is burned).


 * 1) A turbocharger uses the exhaust gas (gas produced by combusting fuel) to spin a turbine. This turbine is connected to a second turbine located at the entrance of the intake pipe (pipe that allows air to enter the engine). This second turbine spins and sucks air into the intake pipe for the engine to use for combustion.
 * 2) The turbine wheel is a turbine in the exhaust pipes which spins when exhaust gas travels through. This turbine is connected to the crankshaft (the part of an engine connected to moving pistons to aid in the combustion process) to add more power.
 * 3) The insulated combustion chamber and its components was to be made of high heat-resistant material which allowed for the removal of a water cooling system.

These three components allowed for the following benefits compared to a typical diesel powered engine:


 * Higher Tank-Mileage. Fuel improvements increased by about 15%
 * Lower cost, weight, and size
 * Reduced maintenance with the removal of a cooling system
 * Reduced emissions, smoke, and noise. 60-80% less particulates were produced
 * Lower compression ratio operation

An adiabatic turbocompound engine required technical ceramics in all three components for mass production. The engine needed material that could withstand surface temperatures up to 1000°C and cylinder pressures over 14 M Pa. Piston cylinders within the engine needed resistance to friction, wear, corrosion, and erosion.

Plans for the engine required advancements in production methods and improvements in technical ceramic material.



Manufacturing
Although research and studies in the late 1980's and 1990's have proven the benefits of using ceramic over metal in engines, no mass production of ceramic engines has happened. There are no economically-viable machining (the process of cutting materials) methods.

Current machining methods are not usable on technical ceramics. A technical paper by Alexander Gorin and M.Mohan Reddy explains how: "advanced ceramics are challenging materials for machining by conventional methods such as turning, milling, and grinding due to the brittle nature and high hardness. This leads to poor machinability and sets the main barrier hindering further application."

Current machining methods for technical ceramics include the following:
 * 1) Turning machining methods will require special tools in order to machine ceramics. A diamond cutting tool with liquid nitrogen as a coolant is needed, which will increase production costs.
 * 2) Grinding will require an entire new method compared to metal grinding. Traditional methods will cause strength degradation in the ceramic material overtime.


 * Electrical Discharge Machining
 * Abrasive Water Jet
 * Ultrasonic Machining
 * Laser-Assisted Milling

The 4 machining methods listed above are viable for smaller ceramic components. Mass production of large engine components with these methods are too expensive for the automobile market.

In Engines
Technical ceramics are used within the following engines:

In reciprocating engines:


 * Valve Guides
 * Cam follower rollers
 * Thermal Barrier Coatings
 * Turbocharger rotors
 * Ball Bearings
 * Pump Seals
 * Spark Plug Insulators

In turbine engines:


 * Nozzles
 * Ceramic lining of combustors
 * Turbine Blades

Coating
Ceramic coating is used to combine the properties of ceramic with easily-available metal. Applications of ceramic coating will provide strong thermal resistance to metal parts. Ceramic coating is used on metal cylinder heads, piston crowns, and intake/exhaust ports.