Supercharger for Opposed-Piston Engine EGR and Startup Boost
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Solution Overview
Problem
In large turbocharged opposed-piston engines, the separation of in-cylinder air requirements for scavenging from exhaust gas recirculation (EGR) requirements is challenging, leading to higher NOx production and pumping losses, especially during low-load conditions, due to the need for additional pumping devices and the inefficiency of large turbochargers.
Innovation Solution
A turbocharged opposed-piston engine air handling system that integrates a supercharger to perform both boost air delivery during startup and EGR driving after startup, reducing the number of pumping devices and enhancing efficiency by separating mass air flow from EGR, thus minimizing engine size, complexity, and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a large turbocharger is used in large opposed-piston engines, then pumping efficiency is improved, but additional pumping devices are required for startup and EGR, increasing device complexity
Solution Approach 1:
The supercharger is designed to perform multiple functions: providing boost pressure during engine startup and driving EGR during normal operation. This multi-functionality eliminates the need for separate pumping devices for each function, reducing overall device complexity while maintaining high pumping efficiency throughout all operating conditions.
Solution Approach 2:
The air handling system dynamically transitions between different operational modes. During startup, the supercharger provides boost pressure; during normal operation, it drives EGR. This dynamic adaptation allows a single device to replace multiple static devices, reducing complexity while maintaining optimal performance across varying engine loads.
2Device complexity
If mass air flow and EGR are not separated in low-load conditions, then device complexity is reduced, but NOx production increases and pumping losses rise
Solution Approach 1:
The air handling system segments mass air flow and EGR into separate pathways. The supercharger drives EGR through a dedicated recirculation channel while mass air flow proceeds through the intake manifold. This segmentation allows independent control of each flow, enabling NOx reduction through proper EGR rates without unnecessarily increasing device complexity.
Solution Approach 2:
The system changes operational parameters based on engine load conditions. In low-load conditions, the supercharger provides sufficient pressure to drive EGR independently, allowing high EGR rates for NOx reduction. In high-load conditions, the system transitions to turbocharger-driven EGR. This parameter adaptation enables NOx control without requiring complex additional devices across all operating ranges.
3Device complexity
If a supercharger is integrated for both startup and EGR functions, then device count is reduced, but the supercharger must operate across wider operating ranges, potentially reducing efficiency
Solution Approach 1:
The supercharger operates dynamically across different functional modes. During startup, it provides high boost pressure; during normal operation, it drives EGR at lower pressure differentials. This dynamic operation across varying pressure ratios and flow rates allows the supercharger to maintain high efficiency in each mode while performing multiple functions, avoiding the efficiency penalty of operating a single device at all conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces pumping losses, enhances engine mobility, and meets NOx reduction standards by optimizing the air handling system with a supercharger that drives EGR independently during normal operation, improving engine efficiency and reducing the need for auxiliary devices.
Implementation Method 1
a supercharger provides boost during engine startup and drives EGR during normal engine operation
Implementation Method 2
it uses some of the exhaust energy to increase the intake air density to provide a higher mass of trapped air in the cylinder and requires pumping energy only from the exhaust gasses
Data Source
AI summary
The air handling system of a turbocharged opposed-piston engine with uniflow scavenging includes an a supercharger operable to provide boost during startup and to drive EGR during normal engine operation.