Wet Compression Engine Thermal Management via Fine Atomization
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Solution Overview
Problem
Internal combustion engines face limitations in efficiency and engine knock due to large water droplets used in water injection, which cause corrosion, entropy increase, and reduced combustion efficiency, while humid air cycles fail to effectively reduce NOx emissions and maintain high compression ratios.
Innovation Solution
The introduction of small water droplets (<5 microns) during the intake stroke, which act as an intercooler, reducing peak charge air temperature and increasing the isentropic or polytropic index of compression, allowing for improved power density and reduced NOx formation through efficient vaporization and reduced entropy production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If large water droplets are used in water injection, then cooling effect is provided, but corrosion and entropy increase occur reducing combustion efficiency
Solution Approach 1:
The liquid water is segmented into fine droplets with diameter less than 10 micrometers through ultrasonic vibration or other atomization means. This segmentation increases the total surface area of the liquid, enabling complete vaporization during the compression stroke while avoiding the corrosion and entropy problems associated with large droplets. The fine droplets are small enough to be fully vaporized before combustion, eliminating liquid water contact with engine surfaces.
Solution Approach 2:
The invention changes the key parameter of droplet diameter from conventional large sizes to less than 10 micrometers. This parameter change fundamentally alters the vaporization behavior - fine droplets vaporize completely during compression due to their high surface-area-to-volume ratio, whereas large droplets do not vaporize completely and cause corrosion. The parameter change also affects the timing of vaporization, allowing it to occur during compression rather than during combustion.
2Object-generated harmful factors
If humid air cycles are used to reduce NOx emissions, then thermal mass increases, but compression ratio and power density are limited
Solution Approach 1:
The invention utilizes the phase transition of water from liquid to vapor during the compression stroke. This phase change occurs at constant temperature (saturation temperature), absorbing latent heat and cooling the charge air. The resulting vapor then mixes with the air-fuel mixture. This approach provides superior cooling compared to humid air cycles because the phase change occurs during compression, not combustion, allowing higher compression ratios and power density while still reducing peak combustion temperatures and NOx emissions.
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 enhances engine efficiency by reducing engine knock, increasing power density, and lowering NOx emissions, while minimizing corrosion and entropy production, enabling higher compression ratios and advanced ignition timing without the propensity to knock.
Implementation Method 1
The phase change from liquid to vapor consumes relatively large amounts of energy with a relatively small temperature change. Wet compression therefore allows a thermodynamic cycle that efficiently compresses an air/liquid mixture with a lower temperature increase than compressing dry air
Implementation Method 2
Liquids can be used to cool combustion gases in internal combustion engines. The introduction of small water droplets (<5 microns) during the intake stroke, which act as an intercooler, reducing peak charge air temperature
Implementation Method 3
Vapor injection increases the thermal mass of the air/fuel mixture and dilutes the charge air. The larger thermal mass reduces the peak temperatures in the combustion chamber therefore reducing NOx formation
Implementation Method 4
During compression, the air temperature surrounding the droplets increases. As the thermal gradient between the droplet and surrounding air increases, the heat transfer rate increases
Data Source
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AI summary
An apparatus including a reciprocating internal combustion engine with at least one piston and cylinder set and an intake stream; at least one liquid atomizer in fluid communication with the intake stream operable to provide a plurality of liquid droplets with a diameter less than 5 μm to the intake stream; and a controller where the controller is able to adjust an index of compression for the engine by: calculating a wet compression level in response to an engine operating limit and adjusting the at least one liquid atomizer in response to the wet compression level.