Aviation Piston Engine Gear Drive for Torsional Vibration Reduction

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Solution Overview

Problem

Current internal combustion piston engines for aviation face challenges in meeting weight requirements and reliability when burning jet or diesel fuel, particularly due to torsional vibration issues in compression ignition engines, which lead to higher maintenance needs and reduced efficiency.

Innovation Solution

The design incorporates a camshaft that functions as both a power transmission shaft and a propeller drive, with a gear set configured to transfer rotational power from the crankshaft to the camshaft, allowing for gear reduction and torque multiplication, thereby reducing torsional vibration by increasing the power train length and converging dominant harmonic excitation frequencies with the first mode natural frequency at lower rotational speeds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If compression ignition engines are used to burn jet fuel, then fuel efficiency and energy density are improved, but torsional vibration and reliability deteriorate

Engineering Contradiction:

Improvefuel efficiencyVSAvoidengine reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces a camshaft as an intermediary component between the crankshaft and propeller. This camshaft serves as a mediator that absorbs and dampens torsional vibrations generated by the compression ignition engine before they reach the propeller, thereby maintaining both fuel efficiency and reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the propeller drive function from the traditional crankshaft-propeller direct drive system and separates it into a dedicated camshaft system. This separation allows the crankshaft to focus on power generation while the camshaft handles power transmission and vibration damping, resolving the reliability issue

Inventive Principle:

Principle #2Taking out (Extraction)

2Power

If larger displacement engines are used to generate necessary power at lower rpm, then power output is improved, but engine weight increases

Engineering Contradiction:

Improvepower outputVSAvoidengine weight

Core Design Contradiction:

PowerVSWeight of moving object

Solution Approach 1:

The camshaft is designed to perform multiple functions simultaneously: it controls valve timing (traditional camshaft function), transmits power to the propeller, and dampens torsional vibrations. This multi-functionality eliminates the need for separate components, reducing overall engine weight while maintaining power output

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the power transmission function with the valve control function by using the camshaft for both purposes. This consolidation of functions into a single component reduces the number of parts and overall engine weight while achieving the required power output

Inventive Principle:

Principle #5Merging (Combining)

3Object-affected harmful factors

If gear reduction systems are added to reduce torsional vibration, then vibration is reduced, but device complexity increases

Engineering Contradiction:

Improvetorsional vibrationVSAvoidengine complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 significantly reduces torsional vibration, lowers maintenance needs, and achieves the required power output within the 300-350 horsepower range, meeting the weight and power requirements for general aviation aircraft like the Cirrus SR22T, while also applying to other applications such as unmanned aircraft and marine craft.

Implementation Method 1

A gear set is configured to transfer rotational power from the crankshaft to the camshaft and to rotate the camshaft at a velocity that is proportional to the rotational velocity of the crankshaft

Methodology Applied

Scientific EffectGear mechanism: Gear

Implementation Method 2

converging dominant harmonic excitation frequencies with the first mode natural frequency at lower rotational speeds

Methodology Applied

Scientific EffectTorsional vibration reduction through frequency convergence: Resonance

Implementation Method 3

reducing torsional moments, gear hammering due to high amplitude torque reversals and torsional stress

Methodology Applied

Scientific EffectVibration damping: Damping

Data Source

PatentEP3835212A1Internal combustion piston engine for aviation

Publication Date: 2021.06.16 NARDELLA FRANCIS A

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AI summary

An internal combustion engine for use with a propeller driven aircraft includes a power output shaft comprising an internal drive shaft journaled within the crank case housing that rotates a propeller to provide propulsive thrust. A gear set is configured to transfer rotational power from the crankshaft to the power output shaft and to rotate the power output shaft at a velocity that is proportional to the rotational velocity of the crankshaft. The gear set is disposed rearward of the engine housing rearward wall and is configured to rotate the power output shaft in a direction opposite the crankshaft rotation. The length of the power output shaft reduces engine torsional vibration. In one embodiment, the engine is a six-cylinder compression ignition engine having a boxer configuration and can generate a peak output power within a range from about 300 horsepower to about 350 horsepower.