Rotary Engine Rotor Offset Peritrochoid Surface

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Solution Overview

Problem

Wankel rotary engines face limitations in compression and expansion ratios due to the maximum desirable recess volume, which restricts the available combustion volume and efficiency.

Innovation Solution

A rotary engine design with a rotor having a peripheral outer surface defined by a peritrochoid inner envelope configuration with a larger eccentricity than the rotor cavity, allowing for an increased minimum volume and reduced recess volume, thereby achieving similar expansion and compression ratios without the need for recesses in the rotor flanks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If recesses are provided in the rotor flanks to adjust compression and expansion ratios, then the combustion volume control is improved, but the device complexity and manufacturing precision requirements increase

Engineering Contradiction:

Improvecombustion volume controlVSAvoid rotor structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent changes the geometric parameters of the rotor peripheral surface by introducing an offset distance between the peritrochoid inner envelope configuration and the actual peripheral outer surface. This parameter modification allows the rotor to achieve desired compression and expansion ratios without requiring complex recess structures, thereby reducing device complexity while maintaining combustion volume control capability

Inventive Principle:

Principle #35Parameter changes

2Power

If recess volume is reduced to increase compression ratio, then the compression ratio is improved, but the minimum combustion volume available decreases

Engineering Contradiction:

Improvecompression ratioVSAvoidcombustion chamber volume

Core Design Contradiction:

PowerVSVolume of stationary object

Solution Approach 1:

The patent moves the solution from modifying the two-dimensional recess geometry on the rotor flank to modifying the three-dimensional spatial relationship between the rotor peripheral outer surface and the peritrochoid inner envelope configuration. By introducing an offset in the radial dimension, the invention achieves compression ratio improvement without compromising the minimum combustion chamber volume

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If the rotor peripheral outer surface follows the peritrochoid inner envelope configuration, then the sealing engagement is improved, but the expansion ratio is limited

Engineering Contradiction:

Improvesealing engagementVSAvoidexpansion ratio

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent applies local quality by maintaining the peritrochoid inner envelope configuration at specific critical locations (apex portions) where sealing engagement is required, while deviating from this configuration in other regions to achieve the desired expansion ratio. This localized application allows the rotor to satisfy both sealing and expansion requirements simultaneously

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP3266980B1Internal combustion engine with rotor having offset peripheral surface

Publication Date: 2020.11.18 PRATT & WHITNEY CANADA CORP

Figure 1
Figure 2A~2B
Figure 3

AI summary

A rotary engine where the rotor cavity (33) has a peripheral inner surface (39) having a peritrochoid configuration defined by a first eccentricity eH and the rotor (34) has a peripheral outer surface (35) having a peritrochoid inner envelope configuration defined by a second eccentricity eR larger than the first eccentricity eH. The engine may have an expansion ratio with a value of at most 8 and may be part of a compound engine system.