Patent ID: 7975480

Claim:
A method for preventing overspeed of a turbocharger in an internal combustion engine system comprising an internal combustion engine capable of generating an exhaust flow, the method comprising: providing a bypass valve that divides the exhaust flow between a bypass flow and a primary exhaust flow; providing a first turbocharger comprising a high pressure charging stage, the first turbocharger receiving the primary exhaust flow; bypassing the bypass flow around the first turbocharger; providing a second turbocharger comprising a low pressure charging stage, the second turbocharger receiving the bypass flow and the primary exhaust flow; providing a relief valve that vents at least a portion of the primary exhaust flow around the first turbocharger when the relief valve is open, the vented portion of the primary exhaust flow being received by the second turbocharger; and opening the relief valve based on whether a protection indicator meets a threshold; and wherein opening the relief valve based on whether the protection indicator meets a threshold comprises determining an engine transient event indicator, and opening the relief valve based on whether the engine transient event indicator meets an engine transient event threshold; and wherein determining the engine transient event indicator comprises determining at least one of whether an engine speed-load change is greater than an engine speed-load change threshold value, whether a target engine speed-load change is greater than a target engine speed-load change threshold value, and whether a user input request change is greater than a user input request change threshold value.