Why are ceramic engines still not commercially available
Time: 2019-03-05 Writer: mingrui
Why are ceramic engines still not commercially available?
This technical difficulty is so far unbreakable!
It is beneficial to use ceramics as engine material. The biggest advantage is that ceramics are resistant to high temperature and poor thermal conductivity, which can greatly improve combustion temperature and reduce heat loss, thus improving efficiency.And because adiabatic good, almost can achieve adiabatic combustion, so there is no need to cool the concept of ceramic engine, eliminating the cooling system will also reduce the complexity of the engine, is also an advantage.So it's not a complete disadvantage, otherwise no one would have moved the mind to study.However, the mechanical properties of the ceramics that can be found are not up to standard.The most promising zirconia ceramic materials,
Thermal efficiency is the ratio of the mechanical work produced by an engine to the chemical energy produced by burning fuel.Under the same displacement, the higher the ratio is, the better the dynamic performance of the engine will be, and the lower the fuel consumption and emission will be.At present, the thermal efficiency of mainstream engines in the world is 30-38%, and the thermal efficiency of individual engines can exceed 40%.For example, Toyota's "DynamicForceEngin" four-cylinder 2.5-l direct-injection engine, which is known for its fuel economy, can achieve a thermal efficiency of 41%.
What is a ceramic engine?
In the traditional diesel engine or gas turbine with metal parts, aluminum alloy heat-resistant limit is 350 ℃, steel and cast iron is 450 ℃, the best super heat close and complicate the engine design, increase the weight and cost a lot of power.For a long time, people have been looking for an ideal material to replace the metal material used in engines.The major reform of engine materials is to replace metal parts with high performance ceramic parts gradually until the main parts of the engine. This is what people call ceramic engine.
There are a lot of high performance ceramics is better than that of metal 貹 can, such as high temperature resistance, wear resistance, corrosion resistance, light weight and good heat insulation performance, these special performance can make the traditional engine face many problems such as the low thermal efficiency and structure of the complex to get reasonable solution, and improve engine performance and durability.Therefore, some experts believe that high-performance ceramics are the most encouraging new development of the internal combustion engine, which will finally solve the problem of the engine to work in harsh conditions.In the 21st century, there will be many ceramic engines.Initially, people research and make a lot of ceramic coating and a single whole ceramic engine parts.Ceramic coating technology is mature, low cost, high life, the use of plasma coating zirconia, titanium carbide and titanium dioxide and other ceramics, to obtain a durable coating within 1 mm.To solve the problem of ceramic coating being too thin, monolithic ceramic parts made of zirconia, silicon nitride, silicon carbide and aluminum titanate are studied.In addition, glass ceramics, alumina and other integral ceramic parts are also studied.
Advantages of ceramic engines
1. High hardness and good heat resistance.The hardness of ceramics is above 1500HV, while the general synthetic metal is only about 400HV, this change in strength is disruptive, at the same time, the heat resistance is also much better than the synthetic metal.
2. Thermal efficiency improvement.The car engine with the best thermal efficiency we know at present is the one on camry, whose thermal efficiency reaches an amazing 41%. However, if the piston, connecting rod, cylinder liner, cylinder head and other important parts are made of ceramic materials, the thermal efficiency of the engine will be greatly improved, at least by more than 35%.
3. Low requirement on fuel quality.Ceramic density is small, light, and not easy to oxidize at high temperature, has a good corrosion resistance, so the requirements for fuel is not so high, can choose lower quality fuel.
4. Reduce engine quality.Ceramics can reduce engine mass from two aspects, one is its light weight, and the other is because ceramics can work at about 1400 degrees Celsius can maintain stability, so do not need a huge engine cooling system, this point alone can reduce the engine body 40% of the weight.
5. Low emissions.Environmental protection is becoming more and more important, and the working temperature of the piston of the ceramic engine can be raised to more than 300 degrees Celsius, which can promote the combustion of fuel and air mixture, and at the same time make the combustion more thorough and reduce emissions.
Application of ceramic engine
The application of ceramics is mainly reflected in two aspects.On the one hand, ceramic high temperature resistance, wear resistance, corrosion resistance and light weight and other performance characteristics, mainly replace the metal parts with ceramic parts, better than the performance of metal parts.Japan is more successful in this respect, it studied a large number of ceramic parts, has been put into production and use: turbocharger rotor, electric plug, rocker arm insert, exhaust lining, pre combustion chamber insert, alumina fiber reinforced aluminum connecting rod and ceramic fiber reinforced aluminum alloy piston.A German company adopted silicon nitride piston pin, which simplified the piston design and reduced the cost.On the other hand, in the cylinder liner, piston, cylinder head and into, exhaust door and other parts on the whole or ceramic coating, using its high temperature resistance and heat insulation performance and other heat insulation technology designed into a low heat dissipation ceramic diesel engine, this engine through the use of heat insulation measures to reduce the loss, the use of heat energy into effective work.Such diesel engines are already used in five-ton trucks and three types of civilian vehicles in western developed countries.In the case of automotive diesel engines, the United States USES heat-resistant ceramic coatings.
Difficulties in ceramic engines
Ceramics are very good, but they are very brittle.But nanoferrification can now make ceramics as tough as plastics, significantly improving their strength, hardness and resistance to fatigue and damage.
2. High manufacturing technology.Ceramic engine has become a hot spot in the world automobile research, but the high manufacturing technology is a fatal problem, after all, the automobile needs mass production.
In fact, as early as 1990, China's first waterless ceramic engine was born in Shanghai. It successfully drove from Shanghai to Beijing after 400 hours of bench test and long distance test.During the 724-hour experiment, the fuel consumption efficiency was 213.56g/km.h, far lower than the current 1.5-l direct injection engine of 380 g/km.h, but that was in 1990.Therefore, although ceramic engine cannot be popularized at present, it is indeed a direction in the future
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