Variable Compression Ratio Diesel Engine Combustion Control
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Solution Overview
Problem
Conventional diesel engines face challenges in achieving efficient power output and controlling nitrogen oxide (NOX) emissions, particularly due to high compression ratios and turbocharging, which lead to elevated combustion temperatures and increased pollutant production, requiring complex and costly after-treatment systems.
Innovation Solution
Implementing a variable compression ratio capability in diesel engines, where a high compression ratio is used for light load, high efficiency operation and a lower compression ratio is employed for higher power conditions, combined with turbocharging and advanced piston crown designs to manage combustion chamber temperatures and reduce NOX formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a high compression ratio is used in a diesel engine, then combustion efficiency and temperature are improved, but nitrogen oxide (NOX) emissions increase
Solution Approach 1:
The patent implements a variable compression ratio system that dynamically adjusts the compression ratio based on operating conditions. The system can switch between a first compression ratio for normal operation and a second, lower compression ratio when high power output is required, thereby optimizing the balance between combustion efficiency and NOX emissions control across different operating regimes
Solution Approach 2:
The invention changes the compression ratio parameter dynamically during engine operation. By varying the compression ratio from a standard high value to a lower value depending on power demands, the system maintains optimal combustion temperatures for efficiency while reducing peak temperatures that generate NOX, thus resolving the contradiction between these two opposing requirements
2Power
If turbocharging is used to increase power output, then power density and efficiency are improved, but combustion chamber temperature and pollutant production increase
Solution Approach 1:
The variable compression ratio system dynamically adapts to turbocharging conditions by adjusting the compression ratio in response to power demands. When turbocharging provides high air density for increased power output, the system can reduce the compression ratio to prevent excessive temperature rise, thereby maintaining the beneficial power output while controlling combustion chamber temperature
3Use of energy by moving object
If a higher compression ratio is used for light load operation, then fuel efficiency is improved, but power output capability is reduced
Solution Approach 1:
The system dynamically switches compression ratios based on load conditions. During light load operation, the engine operates at a high compression ratio to maximize fuel efficiency. When higher power output is required, the system transitions to a lower compression ratio, thereby providing the necessary power capability while maintaining optimal efficiency during normal operating conditions
4Power
If the compression ratio is reduced for higher power conditions, then power output increases, but fuel efficiency decreases
Solution Approach 1:
The variable compression ratio system dynamically adjusts the compression ratio based on real-time power demands. During high power conditions, the system reduces the compression ratio to enable higher power output. The system then recovers efficiency by returning to higher compression ratios during normal operation, thereby optimizing the trade-off between power output and fuel efficiency across varying operating conditions
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 allows for improved power density and reduced NOX emissions by dynamically adjusting compression ratios to maintain optimal combustion temperatures, enabling a smaller, lighter engine with reduced fuel consumption and lower emissions, while avoiding the need for extensive after-treatment systems.
Implementation Method 1
the compression ratio within the combustion chamber is generally maintained above a threshold necessary to create sufficiently high temperatures in the combustion chamber to cause auto-ignition of diesel fuel
Implementation Method 2
The power and efficiency improvements generally result from forcing of more air, and proportionately more fuel, into the combustion chamber or chambers of an engine than atmospheric pressure alone can achieve. The amount by which the intake manifold pressure of a turbocharged engine exceeds atmospheric pressure is generally referred to as a level of boost
Implementation Method 3
create sufficiently high temperatures in the combustion chamber to cause auto-ignition of diesel fuel delivered within the combustion chamber and mixed with compressed gases to form a combustion mixture
Data Source
AI summary
Diesel opposed piston engines, optionally with variable compression ratio and/or turbocharging, can provide improved fuel efficiency by adapting a compression ratio of the engine in accordance with an engine load such that larger compression ratios are used for smaller loads and smaller compression ratios are used for larger loads. Turbocharging can provide improved efficiency at the smaller compression ratio operating conditions. Optionally, one or more current engine parameters can be modified to maintain a peak combustion chamber temperature below a threshold temperature at which an acceptable level of nitrogen oxide pollutants (NOX) is expected to be formed. One or more swirl inducing features can be included on piston crowns in an opposed piston engine. Methods, systems, articles of manufacture, etc. are described.