Water Injection High Compression Engine Thermal Efficiency

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Solution Overview

Problem

Internal combustion engines suffer from inefficiencies due to heat loss through cooling systems, limited compression ratios to prevent engine knock, and suboptimal air-fuel ratios, resulting in low thermal efficiency and high emissions.

Innovation Solution

The implementation of liquid water injection systems that allow for elevated compression ratios and lean air-fuel mixtures, combined with direct or port injection of water into the engine cylinder, to control temperature and reduce the need for external cooling, thereby enhancing thermal efficiency and reducing emissions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If compression ratio is increased to improve thermal efficiency, then thermal efficiency is improved, but engine knock occurs

Engineering Contradiction:

Improvethermal efficiencyVSAvoidengine knock

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

Water is injected into the cylinder before compression begins (during the intake stroke or at the start of compression), allowing the cooling effect to be established beforehand. This preliminary cooling action prevents knock during the compression and combustion processes while enabling higher compression ratios for improved thermal efficiency.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Water acts as an intermediary substance introduced into the combustion chamber to mediate between the need for high compression ratios (for efficiency) and the prevention of knock. The water absorbs excess heat during compression, serving as a thermal buffer that allows the engine to operate at higher compression ratios without experiencing knock.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If conventional cooling systems are used to control temperature, then temperature control is achieved, but heat loss to environment increases

Engineering Contradiction:

Improvetemperature controlVSAvoidheat loss

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The engine uses a portion of its own exhaust heat to vaporize the injected water, converting waste heat into a useful cooling function. This self-service approach reduces the need for external cooling systems and minimizes heat loss to the environment while maintaining temperature control.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system exploits the phase transition of water from liquid to vapor during combustion. The injected water absorbs heat and vaporizes, providing internal cooling that reduces the load on external cooling systems and decreases overall heat loss to the environment.

Inventive Principle:

Principle #36Phase transitions

3Reliability

If stoichiometric air-fuel ratio is used for effective ignition, then ignition reliability is improved, but thermal efficiency decreases due to excess heat

Engineering Contradiction:

Improveignition reliabilityVSAvoidthermal efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system changes the air-fuel ratio parameter from stoichiometric to lean mixtures, combined with water injection. The water compensates for the reduced combustion temperature of lean mixtures, maintaining ignition reliability while allowing the engine to operate at leaner ratios that improve thermal efficiency by reducing excess heat.

Inventive Principle:

Principle #35Parameter changes

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 approach significantly increases thermal efficiency, reduces the need for radiators, and lowers emissions by minimizing heat loss and allowing higher compression ratios without engine knock, leading to improved fuel economy and specific power.

Implementation Method 1

The liquid water absorbs compression heat through evaporation

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 2

The liquid water absorbs compression heat through evaporation, reducing the pressure and temperature

Methodology Applied

Scientific EffectLatent heat: Latent Heat

Implementation Method 3

The piston and cylinder walls are water cooled

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

The piston and cylinder walls are water cooled

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentEP3441591B1Internally cooled high compression lean-burning internal combustion engine

Publication Date: 2020.03.18 NOSTRUM ENERGY PTE LTD

Figure 1A~1B
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Figure 3

AI summary

An internally cooled internal combustion piston engine and method of operating a piston engine is provided, with the combination of liquid water injection, higher compression ratios than conventional engines, and leaner air fuel mixtures than conventional engines. The effective compression ratio of the engines herein is greater than 13:1. The engines may employ gasoline or natural gas and use spark ignition, or the engines may employ a diesel-type fuel and use compression ignition. The liquid water injection provides internal cooling, reducing or eliminating the heat rejection to the radiator, reduces engine knock, and reduces NOx emissions. The method of engine operation using internal cooling with liquid water injection, high compression ratio and lean air fuel mixture allow for more complete and efficient combustion and therefore better thermal efficiency as compared to conventional engines.