The hottest fuel direct injection combustion techn

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Fuel direct injection combustion technology

gasoline direct injection combustion technology (GDI) can improve the fuel efficiency of internal combustion engines by 20% through actual production. The application of the basic technology of this new technology originated in the 1930s, but it has not been developed for a long time. Only in the past two years, due to the improvement of the performance of electronic technology and other systems, this new concept has made a difference

at present, some automobile manufacturers are putting GDI technology into the actual manufacturing application process. For example, Mercury Marine has developed an engine with dual air-fuel direct injection combustion system for its large engine. Since 1996, Mitsubishi Corporation of Japan has also started the development of GDI engine, and Siemens and Renault have also worked together to apply GDI technology to Renault's Megane vehicles. At the same time, Delphi also announced that it would jointly invest with orbital engine manufacturing company to develop an engine system with spark plug and direct fuel injection. This system only needs a hole to the cylinder combustion chamber

the initial idea of developing direct injection technology is that in most cases, the air-fuel ratio of the engine can be adjusted to a thinner state than the 14.7:1 obtained by chemical calculation method, without causing a negative impact on the engine performance. However, its limitation is that it is difficult to ignite the thin gas mixture, and it will also produce corresponding emissions, the main component of which is nitrogen oxide (NOx)

after adopting direct injection technology, the fuel enters the cylinder in the form of fine drops of mist, rather than in the form of steam. This means that when the fuel droplets absorb heat and become combustible steam, they actually cool the cylinder of the engine. This cooling reduces the engine's need for octane, so its compression ratio can be increased. And just like diesel oil, adopting a higher compression ratio can improve fuel efficiency

another advantage of adopting GDI technology is that it can accelerate the combustion speed of oil-gas mixture, which makes GDI engine better adapt to exhaust gas recirculation process than traditional carburetor injection engine. For example, on the engine of Mitsubishi, if the engine combustion is unstable during idle running, the engine can run smoothly with an air-fuel ratio of 40:1 (if exhaust gas recirculation EGR Technology is adopted, the air-fuel ratio of the engine can be increased to 55:1)

the key to determining a very thin gas mixture is to find a reliable way to ignite it. This requires that the concentration of the mixture near the spark plug gap be large enough to ignite. Since the flame center is much larger than the gap size of the spark plug, once burned, the flame will spread to the rarefied gas area in the combustion chamber. The early development work of GDI focused on the research of mega ignition system that can ignite combustibles under the condition of hot control block for a long time. Although the hot and large spark generated by this system can easily ignite the thin gas mixture, the heat generated by the spark plug greatly reduces the service life of the spark plug electrode

using computers to simulate the flow of fuel and air into and out of the combustion chamber is a breakthrough technology. The shape of combustion chamber and piston, the energy and direction of injection pulse, and the movement of piston and engine heat all affect the position of oil-gas mixture droplets. This technology uses key computer technology to determine the air-fuel flow, the best position of the air-fuel injector and the relevant parameters of the spark plug

two basic systems

when this technology is applied to GDI, two basic systems will be produced, which are HPDI and lpdi respectively. The HPDI system relies on high pressure (100 bar or 100 atmospheric pressure) to force fuel into the already air filled combustion chamber. In Renault's ide engine, Siemens uses a three piston fuel pump to generate the high pressure required for fuel injection. At the same time, due to the use of solenoid controlled valves, the engine control system can determine the timing of the intake and exhaust valves according to the operation needs of the engine

o the periphery of the test box should be sealed. The low pressure direct injection system (lpdi) of rbital company is a further improvement and improvement of the technology of two-stroke engine applied to automobile manufacturing. After adopting lpdi system, a certain amount of fuel is injected into the air chamber located on the top of the oil-gas mixture injection device. A belt or cam driven air compressor is used to supply a pressure of approximately 6.5 bar to the air injection device. When the coil of the air injection device is activated, the air pressure will make fuel and air enter the combustion chamber. The key of this system is that the fuel flow into the combustion chamber should be flammable. A major feature of this system is that because the fuel is not under very high pressure, there is no need to use a special fuel pump, and the risk of cracking and leakage of the fuel supply device is much smaller

Both HPDI and lpdi systems face challenges. First, the fuel injection mode must be very accurate, so that the fuel can be distributed correctly in a layered manner. In HPDI system, this means higher injection pressure and faster injection speed. Siemens claims that it is currently studying a fuel injection system with a pressure of up to 200 bar, which has a high-precision injection device that can ignite in half a millisecond

to obtain a satisfactory stratification of the fuel air mixture means that the shape of the combustion chamber and the top of the piston are very critical. This requires computer modeling and extensive testing of each engine to determine its final shape. This means that GDI technology cannot be simply tied to existing engines. The cylinder and piston need to be changed, and the hardware of the engine's electronic control system also needs to be improved

compared with the traditional engine fuel pump, the fuel pump required by HPDI system is very different. The traditional electric fuel pump needs to let the fuel flow through the pump body to maintain cooling and lubrication. On the other hand, the fuel pump of the high-pressure HPDI system uses a hydraulic pump assembly that is separated from the fuel flow. In order to reduce the possibility of leakage when operating under such high pressure, it is necessary to separate the functions of these two parts. PSA Peugeot Citroen and Siemens have formed a joint venture to produce this new fuel pump specifically for the European market

let the engine burn a very thin mixture of oil and gas, which means that it burns less fuel per combustion stroke, so it produces less power. Mitsubishi's GDI Engine breaks through this limitation by adopting a dual-mode combustion system. Under normal conditions, such as low load driving conditions in urban areas, fuel injection is delayed in the compression stroke, which is the same as that of diesel engines. This method provides an extremely thin stratification of the oil-gas mixture, thereby improving the fuel economy of the engine. When the information from different engine sensors detects that the driver wants to operate the car under high load or high speed, the injection pulse will be injected in advance on the intake stroke

this technology allows the engine to use a normal air-fuel ratio. The key is that the electronic system of the engine can determine when and how the fuel should be injected in real time

gdi technology has a very important impact on engine emissions. As you can imagine, when less fuel is burned in an oxygen rich environment, the production of HC and co will certainly be greatly reduced. On the other hand, the production of NOx is a problem. In order to avoid this problem, Mitsubishi GDI engine adopts an EGR ratio of 30% and a new lean NOx gas catalyst. This kind of catalyst is a kind of storage equipment, which can absorb excess NOx if necessary, and then introduce HC emissions into that part of the catalytic converter to function again. Since this device is located in front of the three-way catalyst, the amount of HC required for excess NOx catalysis should be noted here

this new technology requires at least several sensors to work. A new sensor has been developed to detect the level of excess NOx. This sensor is very similar to the traditional oxygen sensor in many aspects, except that its solid electrode adopts different materials, and it adopts a two chamber design structure. The traditional oxygen sensor does not work for the mixture obtained by non stoichiometric method, so some other things are needed here. A kind of oxygen sensor called UEGO split line developed for ULEV engine can work well under this air-fuel ratio, and is used in Mitsubishi engine system

as you know, GDI engine is very different from the traditional inlet fuel injection engine widely equipped on vehicles at present, and this new engine will undoubtedly be applied in the near future. In fact, Toyota's hybrid car Prius has been equipped with such an engine, and Ford, general motors and Chrysler are developing this new engine. A 70 year old concept is gradually becoming a practical fff3d printer manufacturer and ebaltakunststoffgmbh (a material company) have announced the launch of new polyurethane (PU) materials for 3D printing, which is commendable. All this is attributed to the on-board sensors and electronic control system, as well as the computer modeling system that finally brought the technology to the surface. (end)

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