Dedicated EGR Cylinders for V8 Engine Exhaust Interference
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Solution Overview
Problem
90 degree V-engine with cross-plane crankshaft and eight or more cylinders experiences exhaust blowdown interference due to high exhaust back pressure and residual in-cylinder exhaust, leading to decreased engine performance.
Innovation Solution
Incorporating dedicated EGR cylinders with specific cylinder firing orders and separate EGR exhaust pipes to reduce exhaust blowdown interference, where the first and second dedicated EGR cylinders are positioned to precede or follow another cylinder in the same bank, allowing for efficient recirculation of exhaust gas directly into the intake manifold, separate from the main exhaust manifolds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional exhaust manifold configuration is used in 90 degree V-engine with eight or more cylinders, then exhaust gas can be collected and treated, but exhaust blowdown interference occurs due to high exhaust back pressure and residual in-cylinder exhaust
Solution Approach 1:
The exhaust system is segmented into separate EGR exhaust pipes for dedicated EGR cylinders, independent from the main exhaust manifolds. This segmentation allows dedicated EGR cylinders to exhaust directly to the intake manifold without interference from other cylinders' exhaust blowdown, resolving the technical contradiction by isolating the EGR function from harmful exhaust interference.
Solution Approach 2:
The EGR function is extracted from the conventional shared exhaust manifold system. Dedicated EGR cylinders are identified and their exhaust paths are separated and extracted into independent EGR exhaust pipes that connect directly to the intake manifold, removing them from the harmful exhaust blowdown environment of the main manifolds.
2Object-affected harmful factors
If dedicated EGR cylinders with separate EGR exhaust pipes are implemented, then exhaust blowdown interference is reduced, but device complexity increases
Solution Approach 1:
The EGR exhaust pipes from dedicated EGR cylinders are merged with the existing intake manifold system, connecting directly to it. This merging approach integrates the new EGR function into the existing engine architecture rather than creating completely separate systems, thereby reducing the increase in device complexity while still achieving reduced exhaust blowdown interference.
3Productivity
If specific cylinder firing order is used with dedicated EGR cylinders, then pumping work and residual exhaust are reduced, but engine configuration complexity increases
Solution Approach 1:
The cylinder firing order is predetermined and optimized in advance to position dedicated EGR cylinders such that they exhaust to the intake manifold at optimal moments in the engine cycle. This preliminary arrangement of firing sequence ensures that EGR exhaust is delivered when it most effectively reduces pumping work and residual exhaust, achieving performance improvement without requiring complex real-time control adjustments.
Data Source
AI summary
A ninety-degree V-engine having eight or more cylinders can include a first pipe that connects an exhaust port of a first dedicated EGR cylinder bank to an intake manifold and a second pipe that connects an exhaust port of a second dedicated EGR cylinder of a different cylinder bank to the intake manifold, the first and second dedicated EGR cylinders each being one of two consecutive cylinders in a corresponding cylinder bank specified by a specific cylinder firing order.