Tapered-Ring EGR Backflow Prevention for Low-Speed High-Torque Engines

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Solution Overview

Problem

Existing engine EGR systems face challenges with gas backflow in the pipeline, particularly at low-speed high-torque conditions, leading to low EGR rates and failure to realize exhaust gas recirculation.

Innovation Solution

The implementation of a backflow preventer featuring tapered rings arranged in the EGR pipeline, which creates different throttling losses based on flow direction, inhibiting reverse flow and promoting forward flow by gradually tapering the flow section along the axial direction, preventing gas from flowing back.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the engine operates at low-speed high-torque conditions, then the intake pressure becomes higher than the turbo front pressure, but gas backflow occurs in the EGR pipeline preventing EGR realization

Engineering Contradiction:

ImproveEGR realization capabilityVSAvoidgas backflow

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The tapered ring is designed with its large end facing the turbo direction and small end facing the engine direction, creating asymmetric flow resistance. This inverted geometry allows easy forward flow (turbo to engine) while blocking reverse flow (engine to turbo) during low-speed high-torque conditions when intake pressure exceeds turbo pressure.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The tapered ring changes the flow resistance parameter asymmetrically based on flow direction. The gradual taper creates low resistance for forward flow while creating high resistance for reverse flow, allowing the system to adapt to different pressure conditions without additional control mechanisms.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If multiple EGR gas intake pipes are arranged in parallel, then more cylinders can be served, but exhaust gas flows back into other pipes lowering the EGR rate

Engineering Contradiction:

ImproveEGR rateVSAvoidcross-pipe backflow

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The EGR system is segmented into multiple independent intake pipes, each equipped with its own tapered ring backflow preventer. This segmentation allows each pipe to independently control flow direction, preventing cross-pipe backflow while maintaining the ability to serve multiple cylinders.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The tapered ring acts as an intermediary device installed in each EGR gas intake pipe, mediating the flow between the turbo and engine cylinders. It allows exhaust gas to flow forward to the engine while preventing backflow into the turbo and other pipes.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a backflow preventer with tapered rings is installed in the EGR pipeline, then gas backflow is prevented, but the device complexity increases

Engineering Contradiction:

Improvebackflow preventionVSAvoidEGR system structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The tapered ring backflow preventer uses simple, inexpensive tapered ring components that can be easily manufactured and installed. Rather than complex mechanical valves or electronic control systems, it employs passive geometric structures that achieve backflow prevention through their shape alone.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The tapered ring structure is self-regulating and requires no external control, power source, or maintenance. It automatically adapts to pressure differences and flow directions, providing backflow prevention through its geometric design without requiring system intervention.

Inventive Principle:

Principle #25Self-service

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

The backflow preventer effectively prevents gas backflow, ensuring successful exhaust gas recirculation under low-speed high-torque conditions and improving EGR rates across various engine operating conditions.

Implementation Method 1

creates different throttling losses based on flow direction, inhibiting reverse flow and promoting forward flow by gradually tapering the flow section along the axial direction

Methodology Applied

Scientific EffectThrottling loss: Pressure Drop

Data Source

PatentUS11041467B2Backflow preventer and engine EGR system

Publication Date: 2021.06.22 WEICHAI POWER CO LTD

AI summary

A backflow preventer, including one or multiple reducing rings that are disposed in a pipeline; the outer edges of the reducing rings are connected to the inner wall of the pipeline; the multiple reducing rings are arranged along the axis of the pipeline; and the actual internal area of the reducing rings are gradually decreased in the axial direction of the reducing rings. Further disclosed is an engine EGR system including the backflow preventer. The backflow preventer can generate, according to different flowing directions in a pipeline, throttling losses of different degrees; when an air flows in a direction (forward direction) in which the actual internal area of the reducing rings decreases, the throttling loss is small; and when then air flows in a direction (reverse direction) in which the actual internal area of the reducing rings increases, the throttling loss is large.