Optimal Development of an Intake Throttle LP EGR Valve for Passenger Car Diesel Engines

A low pressure exhaust gas recirculation system (LP EGR system) enables the expansion of the EGR operating area than that of the widely used high pressure EGR system. As a result, fuel consumption and emissions can be improved. In order to meet the EU 5 emissions regulations, an exhaust throttle LP EGR system was used. The EU5 vehicles developed using this system have greater merits than other vehicles. However, because the exhaust throttle LP EGR valve is installed adjacent to the after-treatment system, the material of the LP EGR valve itself must be stainless steel in order to withstand the thermal stress, consequently, the cost is increased. Therefore, in order to achieve cost rationalization for EU6 vehicles, an intake throttle LP EGR system is developed and applied to replace the exhaust throttle LP EGR system. In order to apply the intake throttle LP EGR system, the EGR valve is installed in front of the turbo charger compressor. Under this condition, a wider material selection (e.g. Al, steel) is enabled. As a result, the intake throttle LP EGR valve simultaneously realizes cost reductions and weight reductions. In this paper, the design procedure for the LP EGR valve is described and it maintains the air intake performance, mounting and connection stability, thermal reliability, and vibrational strength. First, the flap shape effectiveness is investigated in order to ensure the air intake performance. Second, an appropriate mounting structure for the LP EGR valve is investigated. With these investigations, the development target of the air intake performance, thermal stress, and vibrational strength are achieved. Therefore, the design optimization of the intake throttle LP EGR valve and its mounting structure can be obtained.