Research On Controllable Bypass Of Exhaust Of Turbo Charging Technology For GDI Engine

Today’s economy is very global, and the economy develops very fast, as a result,the development of economy consumes a lot of oil resources. The oil resources are nonrenewable, in order to avoid using the oil resources excessively, human must take some useful measures in order to avoid using the oil resources excessively, and make the future of humanity can develop sustainably. Every country in the world is taking positive measures to solve this problem. They try to save energy. With the improvement of people’s living standards, a lot of families choose to buy a car, the ownership is bigger and bigger. The cars consume a lot of oil every year, it occupies a large proportion of the entire oil consumption. As the ownership of car is bigger and bigger, the government takes more and more attention to the consumption of cars. So,we should develop the technology of energy-saving of vehicles.In order to carry out energy-saving technology of vehicles, Researchers invented a lot of practical and efficient engine technology. GDI technology and turbocharging technology is more representative and relevant to this article. Comparing to the conventional PFI technology, GDI has some advantages, it has higher thermal efficiency, lower fuel consumption and lower emissions. It is an important direction of the automobile engine technology of the future’s research and application. Under the condition of ensuring the engine power outputting, turbocharging technology can reduce the size of the engine effectively, and improve the performance per liter, at the same time its cost is low. Turbocharger can also utilize the exhaust energy of the engine effectively, all these make turbocharging engine have a better economy and power, it is also the future direction of the engine.This article will use a turbocharged direct injection gasoline engine as an object of studying, try to tap the potential to improve the economy of the engine by studying how to control the exhaust bypass valve reasonably. Turbocharged diesel engine technology has been used for a long time, while the application is still a short time ingasoline engine. Comparing to Turbocharged diesel engine technology, turbocharged gasoline engine technology is very different. Turbocharged gasoline engine is high thermal load, and easy to knock. The load and speed of the gasoline engine can change greatly. Gasoline engine adjusts load by changing the throttle opening.Although the turbocharged gasoline engine development trends have been identified,but there are many details that need to continue to explore.In order to obtain greater torque output, the gasoline engine always use turbocharger to increase the amount of intaking air. However, due to the gasoline engine’s operating conditions are transient, the engine speed can be varied from idle to maximum speed, the load of the engine can also change from small to large.Therefore, the turbocharger of fixed volute and size cannot stay productive in all operating range. If the exhaust gas turbocharger matches to the high speed high load,low speed will cause less torque. And if match to the low speed low load, at high speed and heavy load there will be supercharger and larger exhaust resistance. In order to address these problems, the common solution is to match exhaust turbocharger to low speed to ensure low-speed torque output of gasoline engine.When it comes to high speed high load, it will use exhaust bypass valve to make the excessive exhaust bypass off, to reduce supercharging pressure of compressor.However, when the exhaust gas turbocharger enhance the intake pressure, it also increases the resistance of the engine exhaust. But as it increases the engine’s power output, this loss is often be overlooked. However, most of the time the car with gasoline engine is working at part load conditions, for gasoline volume adjustment for load control, throttle is not fully open for part load, the pressure behind the throttle is often lower than a standard atmospheric pressure. At this moment engine do not need turbocharged air to meet the needs of intake air, so using turbocharger this time will increase the resistance of the engine exhaust, and reduce engine economy at the same time.In this article, the question we want to explore is that when the throttle opening is small, if the turbocharger continues to work, turbocharger provides high pressure before the throttle intake one side, throttle obstruct the intake air on another side asthe throttle opening is small, throttling effect is strong. This will result in high exhaust back pressure, large ventilation loss, increased residual gas in the cylinder and other effects. This will neither use the advantages of the turbocharger effectively but also affect the performance of the engine itself. In order to solve this problem a turbocharged direct injection gasoline engine will be studied in this paper, through simulation and experiment to find out what conditions the turbocharger should be involved in the work and what conditions are not. We control the turbocharger work or not work by controlling the exhaust bypass valve. When exhaust bypass valve is open, a large number of off-gas is bypassed, the turbocharger does not work. When the exhaust bypass valve is closed, a large number of exhaust gas will flow through the turbine, the turbocharger stops working. The specific research work includes the following aspects:1. Building a research platform. Including the building of GT-POWER model of a direct injection turbocharged engine. Build a direct injection turbocharged engine test stand. All these work is to prepare for the follow-up study.2. Getting the best opening degree of the exhaust bypass valve of all conditions through simulating.3. Verifying the above results through experiments and get the best opening degree of the exhaust bypass valve of common conditions. Study the torque boosting problem which is caused by the bypass valve closes.4. Designing a new mechanism to achieve the control method.5. Summarizing and generalizing the problems still exist and Looking to the continue research work in the future.Through the study we find that under different speeds, when the load is small,the exhaust bypass valve should be completely open to reduce exhaust backpressure.This allows the engine to improve the economy and power of about 3%. When the load is big, the exhaust bypass valve should be completely closed to make engine work by turbocharged mode. This article also designs a dual vacuum tank of gasoline engine exhaust gas turbine bypass valve control structure which can meet the demand of controlling.