Common rail

The electronically controlled common rail system presents many advantages, because the injection timing and common rail pressure can be controlled independently. An electronic control unit(ECU) torealize control functions is developed, and serious experiments about the injection system are conducted. The purpose of this project is to study the factors that affect injection characteristics. Theresults indicate that the injector has faster response when the common rail pressure rises, increasing the injection rate. One the other hand, the extension of control pulse width adds the valve opentime, which increases the injection duration. The flexible injection characteristics can be acquired by controlling common rail pressure and pulse width coordinately.

1.INTRODUCTION
With theincreasing concern of the environment and more stringent government regulation on exhaust emissions, the reduction of engine emissions is a major research objective in engine development. In order toimprove the engine’s emission performance, various technologies are adopted such as electronically controlled common rail system, clean alternative fuel, high efficient combustion organization, advancedturbo charging, exhaust gas recirculation(EGR) and advanced after treatment technology. The harmful emissions are generated in combustion process, so realizing ideal injection characteristics is one ofthe key aspects to improve combustion and reduce emissions.
Electronically controlled common rail fuel injection system has been accepted as one leading technology in diesel engines, and this systemhas the following advantages:
(1)The injection pressure and injection quantity can be adjusted and acquired flexibly. With high injection pressure independent of engine load and speed, the NOx andPM emissions can be minimized to meet the requirement of emissions regulation and optimize the engine performance.
(2)The common rail installed between oil pump and injectors functions as a...