Student name: ChienShin Wu


Project introduction:
Compared to traditional fuel metering system, such as the carburetor and port fuel injection, the direct fuel injection can provide more flexible and precise fuel supply. This helps engineers to design an engine to achieve desired fuel consumption and low emission without compromising the power output. Nowadays, the most popular direct fuel injection system is the common rail system (CRS). Our studies of the CRS focus on the pressure stabilizing in the rail and on the injection rate shaping control.             


Project outline:
Fuel injection system of the internal combustion engine has migrated from a mechanical system, to an electronically controlled mechatronic system. The carburetor that is driven mechanically has no flexibility of controlling injection timing and fuel quantity in real-time. The electronic fuel injector that injects into the intake port has some flexibility of adjusting the injection timing, but could not offer multiple injections per engine cycle. The direct fuel injection system, especially the common-rail injection system allows the fuel to be injected into the combustion chamber directly with flexible timing and number of injections. The main components of the common-rail system include a high pressure pump, a common rail, an electro-hydraulic valve, and fuel injectors. The pump generates high pressure fluid (up to 200Mpa) entering the common rail, and the injectors inject high-speed fluid into the combustion chamber. The high-speed flows in and out of the common rail induce pressure pulsations that can cause injector metering errors, flow rate variation, and noise. The main control challenge is to precisely control the injected flow rate and fuel quantity against the pressure pulsations. Current practice is to control an electro-hydraulic valve to regulate the pressure inside the common-rail. Due to the response time of the valve and the bandwidth of the control system, high frequency pulsations cannot be removed. We investigated the possibility of using a high speed actuator attached to the common rail to absorb or supply high pressure fluid in real-time to compensate the pressure pulsation. To understand the rail pressure dynamics, a one-dimensional (1D) distributed model is constructed for the common rail and the time-varying internal model based control is applied. Simulation results show clear improvement of the pressure pulsations. We are currently working on the design of the actuator.

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CRS model in AMESim


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Pressure stabilizing effect

 

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Piezo-actuator displacement

 

Reference:

  1. Gupta, V., Zhang, Z. and Sun, Z., “Modeling and Control of a Novel Pressure Regulation Mechanism for Common Rail Fuel Injection Systems”, Applied Mathematical Modeling, Vol. 35, pp.3473-3483, 2011.