Diesel Engine Torque Limiting for Emission Control
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Solution Overview
Problem
Existing diesel engines in work machines face challenges in reducing noxious substances like NOx and PM to regulatory levels, especially in wide output power regions, and existing post-treatment methods complicate systems and increase costs.
Innovation Solution
A diesel engine with limited maximum output torque in a lower revolution speed region, allowing for optimized combustion modes like premixed and diffusive combustion, and using an electric motor to assist the hydraulic pump, simplifying the system and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the diesel engine operates in a wide region of engine revolution speed vs. output torque to enable various types of work, then the versatility and adaptability are improved, but the emission of noxious substances (NOx and PM) increases and becomes difficult to control within regulatory limits
Solution Approach 1:
The engine operation region is segmented into multiple zones (first region with higher revolution speeds and second region with lower revolution speeds) with different maximum output torque characteristics. By dividing the operation region and applying different torque limitations in each segment, the engine can maintain versatility across the wide region while controlling emissions in each specific segment through appropriate combustion mode selection.
2Object-generated harmful factors
If post-treatment devices are added to remove noxious substances from exhaust gas, then the emission levels are reduced to regulatory limits, but the system complexity and cost increase significantly
Solution Approach 1:
Instead of adding post-treatment devices to remove harmful emissions, the invention converts the approach by optimizing the combustion process itself to prevent harmful emissions from being generated in the first place. By controlling the engine operation region and combustion modes (diffusive combustion in first region, premixed combustion in second region), the exhaust gas emissions are reduced at the source, eliminating the need for complex post-treatment systems.
3Object-generated harmful factors
If the maximum output torque is limited in the lower revolution speed region, then the combustion can be optimized for lower emissions, but the available power and productivity are reduced
Solution Approach 1:
The engine dynamically switches between different operation modes based on the operating conditions. In the second region (lower revolution speeds), the engine operates with limited maximum output torque and uses premixed combustion for low emissions. The control system monitors the operating region and adjusts the combustion mode and torque output accordingly, allowing the engine to adapt its characteristics to meet both emission requirements and power demands at different operating points.
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 effectively reduces noxious substances to below regulatory levels without the need for complex post-treatment devices, while maintaining operability and reducing costs.
Implementation Method 1
improves the combustion by forming premixed gas in the ignition delay period through oxygen concentration reduction by EGR
Implementation Method 2
In regions where the premixed combustion is unusable, there is no choice but to use diffusive combustion
Data Source
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AI summary
Provided are a work machine, a power unit, and a diesel engine of a work machine that make it possible to reduce emitted noxious substances to levels below reference values stipulated by exhaust gas regulations in advanced countries and regions while also omitting or simplifying a post-treatment device. A hydraulic pump 7 is driven by a diesel engine 1 that limits maximum output torque in a low revolution speed region NL lower than a high revolution speed region NH including a rated revolution speed in such a manner that the maximum output torque has a characteristic Xa of intermediate torque lower than torque of a maximum output horsepower point at the rated revolution speed, and a hydraulic actuator is driven by hydraulic fluid delivered from the hydraulic pump 7.