Can ceramics be used in engines? Extremely high thermal efficiency?
As we know, the world’s most efficient engine is the one that is mounted on the new Camry, with a displacement of 2.5L and the first engine based on the TNGA platform. The engine has an efficiency of 41%.
So, what technologies does this engine use, and the efficiency is 41%? The main technologies are: intake VVT, exhaust VVT, Atkinson cycle, infinitely variable oil pump, high compression ratio, EGR, porous fuel injection, low friction chain, resin coated bearing, cylinder head integrated exhaust manifold and many more. Basically, the technology that can be currently used has already been put on, and it can be said that it has achieved the ultimate.
At the limit, the efficiency of the engine has to be upgraded one point at a time, which is hard to add. It is like a 100-meter race of the flying Bolt. You want him to increase from 9.58 seconds to 9.4 seconds, which is basically impossible for him because 9.58 The second is already the result of his outbreak of his whole body energy.
At present, the improvement of the efficiency of conventional fuel engines has encountered bottlenecks, especially the current fuel consumption, emission regulations are becoming more and more demanding, and finding a bottleneck breakthrough is imminent.
Is there really no way to continue to improve thermal efficiency? In fact, it may not be.
Ceramic engine is a direction
Since the invention of gasoline and diesel engines in Germany in the late 19th century, car engines were made of metal. This is an inevitable choice because metal was the only choice at that time. The high strength, heat resistance and reliability of the metal make it the perfect choice for engine parts.
But with the continuous development of engine technology, until the bottleneck is encountered. The properties of the metal limit the upward efficiency of the engine.
Why do you say that? The principle of the engine is clear to everyone. It is the combustion of the fuel to release the thermal energy into the expansion gas to push the piston to do work. In this process, only about 1/3 of the fuel’s thermal energy pushes the piston to work. In addition, most of the heat is transferred from the cylinder liner to the coolant and then to the air.
Why do you want to cool it? Because of the nature of the metal, the core components of the engine are the piston linkage, the cylinder block, and the crankshaft. The piston is made of aluminum alloy, the top is added with heat-resistant coating, the crankshaft and the connecting rod are basically cast iron and alloy steel.
The extreme temperature resistance of aluminum alloy is about 350 °C, the cast iron is about 450 °C, and the super temperature resistant alloy is about 1000 °C. Therefore, it is necessary to ensure that the temperature of these metal core parts must be below the limit temperature point, otherwise it will be hot. Deformation, resulting in parts damage and engine scrap.
The ceramic engine solves all the above problems.
And the characteristics of ceramic materials are as follows:
1. The thermal characteristics of ceramic materials, the melting point is very high(above 2000℃), while the melting point of general metal is about 1400 ℃.
It has excellent chemical stability at high temperature, and the thermal expansion coefficient of ceramic is lower than that of metal. When the temperature changes, the ceramic has good dimensional stability.
2. The hardness of the ceramic is 1500 HV or more, while the general synthetic metal is about 400 HV.
Moreover, the thermal insulation of the ceramic is very good. According to this characteristic of ceramics, the use of ceramic materials to make pistons, connecting rods, cylinder liners, cylinder heads and other heavy-duty parts will greatly improve the thermal efficiency of the engine, at least by more than 35%.
Engine efficiency will reach around 70%, leaving the Camry engine 41% efficient.
The principle of efficiency improvement is that the operating temperature of the piston is greatly improved due to the heat-resistant temperature and heat insulation of the ceramic material, and can be increased from about 1000 °C to about 1300 °C, and the thermal efficiency is increased by about 30%.
3.Since the ceramic maintains good stability at temperatures around 1400 °C.
The physical and chemical properties are very good, no deformation, no corrosion. This eliminates the need to cool the piston, cylinder liner, and cylinder head. There is no need for a large engine cooling system, no cooling fans, condensers, radiators, intercoolers, associated connecting lines, and coolant. The removal of these parts can reduce the weight of the vehicle by about 100KG.
The working temperature of the piston is increased by more than 300 °C, which greatly promotes the combustion of the fuel and air mixture, and the combustion is more thorough, which has great advantages for fuel consumption and emissions.
4. Ceramics are low in density and light in weight.
Compared to traditional aluminum alloy pistons, steel connecting rods, ceramics, and piston rods can reduce weight by about double. This is unavoidable, the weight of the connecting rod piston is reduced, and the inertia force of the piston and the connecting rod will be doubled. The operating speed of the piston can be greatly improved, and the power is increased by at least 1/3. This is a very good prospect for F1, which is extremely fast.
5. Ceramics have the characteristics of corrosion resistance, are not easy to oxidize at high temperatures, and have good corrosion resistance to acids, alkalis and salts. From this point of view, the fuel selection range will be greatly improved, and fuel with poor fuel quality can be selected.
From the point of view of ceramic materials, the main component of ceramics is silicate. The main constituent elements are silicon, aluminum and oxygen, accounting for 90% of the total amount of crust elements. The resources are very rich. Iron only accounts for 4.75% of the amount of crust elements.
Is mass production possible?
Since ceramic engines have a greater advantage than traditional metal engines, why are they not popularized and mass-produced?
In 1990, China’s first waterless cold ceramic engine was born in Shanghai. The engine fully utilized the characteristics of ceramic high temperature resistance and wear resistance. It used 11 kinds of ceramic heat insulation parts and ceramic wear parts. After 400 hours of bench test, the long-distance test of the actual vehicle was carried out and Shanghai arrived in Beijing smoothly.
After a total of 724 hours of testing and evaluation, the minimum fuel consumption rate was 213.56 g / km.h, which is quite amazing results. At present, the lowest fuel consumption rate of the 1.5L supercharged direct injection engine with higher thermal efficiency is 380g/km.h. And this is the product of the 90s.
At present, the top of the engine piston also has a ceramic coating, and the connecting rod also has an aluminum connecting rod with a ceramic component, and the hardness and fatigue resistance are increased by 4-5 times. These technologies are all applied on Toyota.
As can be seen from these practical examples, the development of ceramic technology will promote the innovation of engine technology. But the root cause of not being popular is: brittleness. It is a difficult problem that ceramics can’t overcome. The ceramic materials used in the ceramic engines used in the test are all made of high-purity synthetic and fired by precise control technology. The process is complicated, the cost is high, and the brittleness is not fundamentally solved. .
However, there is an emerging technology. Through nanometerization, fragile ceramics can have the same toughness as plastics. In ceramic-based nanocomposites, nanoparticles are mainly dispersed in the matrix or between grains, and their functions can not only improve mechanical properties. Nanocomposite ceramics can increase the strength and toughness of the matrix material by 2-5 times, and can improve hardness, strength, and fatigue resistance.
There are still many key technical problems to be solved in nanoceramics, but the preparation of nanoceramics is relatively mature. New technologies are constantly emerging. I believe that with the deepening of research, nano-ceramics will be more perfect, and the day when metal can be completely replaced is just around the corner. I believe that in the near future, the use of nano-ceramic technology in automobiles will set off a car revolution.
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