EGR Systems & Components Part 2

EGR Systems & Components Part 2

Similar to EGR systems used in any Euro 3, as well as EPA Tier 1 and Tier 2 Bin 10 applications, the system is conceived of a high pressure loop with a cool EGR configuration. Channeled through an EGR control valve, a portion of the exhaust proceeds to the EGR cooler. From there it flows to a throttle valve   assembly where it is combined with filtered, high pressure, fresh combustion air, which has been cooled by an intercooler in order to recover density. This combination of air and EGR is then inducted into the engine through the intake manifold. It is equipped with a variable geometry turbocharger (VTG), which can create a higher exhaust manifold than intake pressure to drive EGR. The intake throttle is used under certain conditions when it is unable to create a sufficient differential with the VTG. During the early 2000s, there was some belief that future engines with higher EGR rates would require at least some type of EGR pump in order to achieve the necessary engine-out NOx emissions demanded for future emission standards. If an HPL EGR system supplied such high EGR rates, it would result in an unacceptable fuel economy penalty. So rather than a pump, most systems manufactured a hybrid configuration instead, such as the 2.0L Volkswagen TDI engine introduced in North America for MY 2009 EPA Tier 2 Bin 5 applications. Controlled by the HP EGR valve and the turbocharger vane position, the HPL EGR is used at lower engine speeds and loads. When used at higher engine loads and speeds, the eGR supply is able to shift to the LPL EGR system. It also comes equipped with two-stroke low speed engines. The low-speed two-stroke marine engines burn heavy-fuel oil (HFO), making the EGR system itself quite complexing especially with the need to clean the recirculated exhaust has of harmful metals and sulfur, making the need to maintain the exhaust header pressure blow the intake header in order to ensure cylinder scavenging. Its main components are scrubber; cooler; water mist catcher; blower; shut-down valve; changeover valve; water treatment plant (WTP) consisting primarily of the buffer tank; NaOH dosing system; and water cleaning unit. A control system is responsible for controlling the amount of EGR; the scavenge air pressure; the NaOH dosing; scrubber water circulation; and scrubber water discharge. It is equipped with a maximum flow of fresh water through the scrubber of 200 m3/h at MCR. However, as this is around one fifth the flow needed for sea water scrubbing, a reduced fuel consumption penalty will be the added result. ETM



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