On the premise of ensuring that the weight and drive efficiency do not change significantly, in order to greatly increase the range of current new energy vehicles, the field of internal combustion engines has become an exploration path that cannot be ignored.
The well-known PHEVs (plug-in hybrids) and REEVs (extended range electric vehicles) focus on gasoline engine technology, however, it seems that in this race for efficiency, the diesel engine has been forgotten.
When it comes to work efficiency, diesel engines can be said to be unique in the field of gasoline engines. In the era of fuel vehicles, taking Volkswagen's TDI and TSI engines as examples, TDI's fuel consumption performance almost crushed TSI. In the case of the same Golf, the diesel version of the Golf consumes less than 5 litres, while the petrol version hovers around 7 litres.
This gap is even more pronounced in the larger models, where the fuel consumption of the diesel version is only about 10 litres, while the petrol version stabilizes at more than 15 litres, taking the big G as an example.
This makes everyone wonder, why does the diesel engine, which has such a high drive efficiency, become a small transparent in today's hybrid car technology?
How the diesel engine works: the miracle of the squeezing force
In 1897, the German Rudolf built the world's first diesel engine, and at the beginning of the 20th century, diesel engines began to be widely used in ships, automobiles, locomotives and electric power. Moreover, the use of diesel engines on submarines during World War I made it play an important role in the war.
It can be said that the diesel engine has largely promoted the development of modern industry. A diesel engine works like a small air pressure pump. Its working process can be broken down into four steps, which we call a "four-stroke": suction, compression, work and exhaust.
Just as we inhale, the piston of a diesel engine moves down inside the cylinder, creating a space into which air is sucked in. The piston then moves upwards to compress the inhaled air, just like when we squeeze a balloon with our hands. This process makes the air very hot.
When the air is compressed to a certain extent, diesel fuel is injected into it. Diesel fuel will spontaneously combust when it encounters high temperature and high pressure air, producing a large amount of heat energy, which pushes the piston downward, just like a balloon that is squeezed and suddenly released, and the expansion force of the gas will push the balloon to fly out.
There are two main properties of diesel fuel involved, high compression ratio and spontaneous ignition characteristics.
The compression ratio refers to the ratio before and after compression, and a high compression ratio means that the diesel engine can be compressed more thoroughly to obtain more energy, mainly because the diesel engine compresses only air when compressed, even if there is a high compression ratio, there will be no premature deflagration.
The spontaneous combustion characteristic means that diesel fuel is more likely to spontaneously ignite in the cylinder, pushing the piston to move, which is also the reason why the efficiency of the diesel engine is about 15% higher than that of the gasoline engine, up to 45%.
Because of this, large motor vehicles are used as internal combustion engines because of their huge size and amazing fuel consumption. If a motor vehicle such as a tractor or a large truck uses a gasoline engine, then our farmer uncle and driver uncle may have to take out a loan to go to work.
The hybrid dilemma: Why are diesel engines abandoned?
At present, in order to solve the problem of battery life, new energy vehicles are equipped with internal combustion engines as range extenders, and use fuel and electric hybrid drives to increase and solve range anxiety.
If it was to increase the range, why did the more efficient diesel engine be abandoned and the gasoline engine was chosen instead?
In the past two decades, the domestic automobile market has been dominated by gasoline engines. Our technical route has been around the development and production of small displacement gasoline engines.
This makes the design and production of small-displacement gasoline engines that match the technical routes of PHEVs and REEVs a relatively low-cost and relatively difficult task. The continuous development of this technological orientation has made small displacement gasoline engines a mainstream choice.
In contrast, producing a reliable, stable, and excellent diesel engine is a huge challenge. The industrial development direction of the mainland is less focused on diesel engine technology suitable for family vehicles, which makes the underlying diesel engine technology relatively underdeveloped.
Today's BYD, Geely, Great Wall and other special hybrid gasoline engines, the efficiency can reach 40%, and the cost is extremely low, mainly because our technology precipitation is enough.
In the eyes of major enterprises, betting on the investment in diesel engine technology route has higher risks than returns, so it has not received much attention.
Overall, Continental is lacking in basic R&D of diesel engine technology and is under pressure to increase production focus on diesel hybrid technology. This technological lag and relatively small market demand make the application of diesel engines in hybrid systems more difficult.
On the other hand, the diesel engine itself is contrary to the word new energy, in the hybrid car, the working time of the internal combustion engine itself is very limited, and the start and stop process of the diesel engine is relatively slow, which contradicts the need for the hybrid system to quickly switch working modes.
Second, the emission of pollutants such as nitrogen oxides (NOx) and particulate matter emitted by diesel engines may lead to a decline in the overall environmental performance of hybrid systems, which is inconsistent with the environmental protection concept of electric vehicles.
In addition, in people's traditional impression, diesel engines are internal combustion engines that only tractors and large trucks will equip with. Because of its unique working principle, it is very noisy when it operates, which reduces the driving comfort to a certain extent. After all, no one wants their land cruisers to become road tractors.
Of course, another very important reason is the supply of diesel. Since most of the large-scale mobile equipment uses diesel engines, diesel has become an important strategic resource.
Compared with the benefits produced by the military, industry, agriculture, transportation and other fields, it is a bit overkill to send a large amount of diesel fuel to domestic cars.
The future of hybrids is a matter of coexistence or obsolescence
Having said that, hybrid vehicles, as a means of exceedance from fuel vehicles to pure electric new energy, do not need to pursue a little more efficiency brought by diesel engines, because most of the time, the use of internal combustion engines is extremely limited.
Although it is an over-the-top measure, this hybrid drive method can actually bring a lot of convenience. For example, hybrid vehicles have smaller battery capacity and motor power than pure electric vehicles, so they are relatively low in cost and weight, and also reduce the requirements for battery technology and power systems.
Hybrid vehicles can adjust the proportion of energy used according to different driving modes to meet different performance and economic needs, for example, in the city at low speeds, you can use the pure electric mode, and on the highway, you can use the direct engine mode.
Therefore, hybrid vehicles can still persist for a long time, and will not be completely replaced by pure electric vehicles in the future, but will coexist and complement pure electric vehicles to form a diversified new energy vehicle market.
epilogue
Therefore, it is not that the diesel engine is bad as a range extender for hybrid vehicles, on the contrary, in terms of effect, it is completely okay, but the gasoline engine is more cost-effective.
After all, electric drive will replace fuel after all, so why bother thanklessly breaking diesel engine technology. And in the future, there may be better energy alternatives, and even battery technology can be put aside.