Function of intercooler in supercharged engine

The engine of many cars now has a striking "T", which proves that it is a supercharged engine. As we all know, the turbocharged engine has added a turbine device on the basis of the original engine. During operation, the excess energy generated by the turbine itself must be reasonably transmitted. This requires a device to "neutralize energy" with it, which is the intercooler.
The intercooler will increase the air resistance, reduce the pressure of the charge air, reduce the supercharging effect, and slow the engine response. However, this effect is insignificant compared with the role of the intercooler in increasing the engine power.
Air cooling or water cooling?
There are only two ways to cool the air. One way is to cool down by the cold air when the vehicle is driving, and the other way is to use water cooling. The principle of the former is the same as that of the radiator of our household refrigerators and air conditioners. It is to let the air pass through one pipe to increase the contact area between the pipe and the surrounding air, and then cool it through the surrounding air. An air cooled intercooler placed above the engine.
Water cooling is just the opposite of air cooling. It is to put a cooler into the air inlet pipe to let the pressurized hot air flow through. In the cooler, there is cooling water flowing constantly, which takes away the heat of the charge air.
The solid line represents the flow of air The dotted line represents the flow of cooling water
First of all, let's move on to the previous topic. When the air is compressed through the supercharger, the temperature will rise, which is a basic physical principle. How much will the gas temperature rise after pressurization? This depends on the working condition of the supercharger. The higher the speed, the greater the boost pressure, and the greater the temperature rise. Generally speaking, it can rise about 40-60 degrees. With the original temperature of the air, the pressurized gas is very hot.
The influence of high temperature gas on the engine mainly lies in two points: first, the air volume is larger, which is equivalent to that the engine absorbs less air; The second point is more important. High temperature air is particularly unfavorable for engine combustion, which will reduce power and worsen emissions. Under the same combustion conditions, the engine power will decrease by about 3%~5% for every 10 ℃ increase in the temperature of the charge air. This problem is very serious. The increased power will be offset by the high air temperature. To solve these problems, we need to cool the pressurized air again and send it to the engine. The component that bears this heavy responsibility is the intercooler. The intercooler sounds cool, but its principle and structure are no different from the radiator of our household refrigerators and air conditioners.
Side effect: engine response speed slows down, turbine hysteresis becomes serious, why intercooler
Generally speaking, the larger the intercooler is, the smaller the air flow loss inside it is and the higher the cooling efficiency is. The longer the air flow stays inside the intercooler, the better the cooling effect will be. However, the intercooler is like increasing the volume of the intake pipe. The compressed air produced by the supercharger must first fill this volume, and then the supercharging effect can be produced. If used for turbocharging, the direct performance effect is that the turbine hysteresis becomes serious; Even a supercharged machine will cause the engine to respond slowly.
On the other hand, as the charge air must flow through various pipes, the resistance increases, and the boost pressure will certainly be weakened. However, this weakening is only generated within a short period of time after the accelerator is depressed, because the pressure of the charge air will be weakened and sufficient pressure will be re established in the sealed space between the intercooler and the inlet valve until the pressure relief valve opens. Therefore, the performance is still that the engine response is slow, and the sluggish phenomenon of turbocharging will become serious.
The intercooler will make the turbine lag more obvious, but it must be installed. Therefore, how to balance the cooling efficiency and pressure maintenance is a headache for engineers. The fundamental method is to reduce the volume of the entire intake pipe, reduce the pipe resistance, and shorten the intake pipe. Therefore, the intercoolers we see are often close to the engine, not as far away from the engine as the radiator. High supercharged and large displacement engines often need a large intercooler due to large intake air volume and high temperature. The large intercooler is easily seen on the engine roof, so that we can open an air inlet on the engine compartment lid and use the cold air that crashes head-on to cool down. This method can be seen in many cars, such as Wing Leopard STI and MINICOOPERS. The advantages of being placed above the engine are compact structure and short pipes, which are very suitable for small cars and refitted vehicles. However, this arrangement is too close to the engine and will be affected by the engine heat.
MINICOOPERS and Wing Leopard STI both have openings on the engine hood for intercooler heat dissipation
Another arrangement is to place the intercooler under the front of the car's middle net. This method makes full use of the oncoming cold air for heat dissipation, but the pipe is too long and the layout is more complex. As it is closer to the ground, it is more likely to be damaged by sand and gravel on the ground.
For these two cooling methods, they are both external air cooling, and are suitable for large intercoolers. However, the current trend is low supercharged engines, which do not need too large intercoolers. At the same time, in order to make the engine more compact, many engines now use water cooling. A cooler is put into the air inlet pipe, and the air is cooled as it passes through. The structure is very compact.
Intercooler for Volkswagen 1.4TSI
Intercooler is a very important component in supercharged engine, which can effectively reduce air temperature and improve engine power. In addition to reducing the air temperature, we also need to cool the turbocharger and control the boost pressure.
The familiar Volkswagen 1.4T turbocharged engine uses this method, while Audi's supercharged engine also uses this method for cooling, which is quite compact in structure. Since the intercooler is completely installed inside, it is less damaged by dust and sand.