Dual Fuel Engine EGR Temperature Control
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Solution Overview
Problem
Dual fuel engines face challenges in balancing compression ratios to prevent premature self-ignition of natural gas while ensuring adequate diesel ignition, particularly at lean air/fuel ratios, leading to variability in engine operation.
Innovation Solution
A dual fuel engine system that utilizes a three-way EGR valve to control the temperature of recirculated exhaust gas, mixing cooled and un-cooled EGR streams to achieve a predetermined temperature, combined with split direct diesel injection events to manage combustion in the combustion chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high compression ratio is used to ignite diesel pilot, then diesel ignition is improved, but natural gas may prematurely self-ignite
Solution Approach 1:
The patent changes the temperature parameter of the EGR gas to resolve the contradiction. By controlling EGR gas temperature to be between 50°C and 150°C, the system prevents natural gas self-ignition while maintaining diesel ignition reliability. The temperature control is achieved through a cooling system that regulates the EGR gas temperature before it enters the combustion chamber.
Solution Approach 2:
The patent introduces cooled EGR gas as an intermediary substance between the diesel pilot and natural gas mixture. The cooled EGR gas acts as a thermal buffer that prevents premature natural gas ignition while allowing diesel pilot ignition to occur. This intermediary approach resolves the contradiction by mediating the thermal interaction between the ignition source and the fuel mixture.
2Object-affected harmful factors
If low compression ratio is used to avoid self-detonation of natural gas, then premature ignition is prevented, but cylinder temperatures and pressures are insufficient for reliable diesel ignition
Solution Approach 1:
The patent changes the temperature parameter of the recirculated exhaust gas to resolve the contradiction. By controlling EGR gas temperature to be between 50°C and 150°C, the system prevents natural gas self-detonation while maintaining sufficient thermal conditions for diesel ignition. This parameter control allows low compression ratios to be used without sacrificing ignition reliability.
Solution Approach 2:
The patent applies preliminary cooling action to the EGR gas before it enters the combustion chamber. By pre-cooling the exhaust gas to a controlled temperature range, the system prepares the thermal environment in advance to prevent natural gas self-detonation while ensuring adequate conditions for diesel pilot ignition occur when needed.
3Object-affected harmful factors
If cooled EGR is used to prevent natural gas self-ignition, then self-ignition is reduced, but EGR gas temperature control complexity increases
Solution Approach 1:
The patent defines a specific temperature range (50°C to 150°C) for the EGR gas to resolve the contradiction. By establishing this parameter range, the system achieves effective prevention of natural gas self-ignition without requiring overly complex control mechanisms. The controller adjusts the EGR valve positions to maintain the temperature within this range, balancing effectiveness with simplicity.
Solution Approach 2:
The patent employs dynamic control of the EGR system through a controller that adjusts the first and second EGR valves in real-time. This dynamic adjustment allows the system to maintain optimal EGR gas temperature under varying engine operating conditions, preventing natural gas self-ignition while adapting to different loads and speeds without excessive complexity.
4Device complexity
If un-cooled EGR is used to simplify the system, then system complexity is reduced, but natural gas self-ignition risk increases
Solution Approach 1:
The patent introduces a temperature parameter constraint (50°C to 150°C) on the EGR gas to resolve the contradiction. By monitoring and controlling the EGR gas temperature within this range, the system prevents natural gas self-ignition while maintaining relatively simple system architecture. The temperature sensing and control mechanisms add minimal complexity compared to the benefit of preventing harmful self-ignition events.
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 stabilizes engine operation across various load conditions, improving the coefficient of variation of mean effective pressure and allowing for lean air/fuel ratios even at low compression ratios, enhancing engine efficiency and emission control.
Implementation Method 1
An EGR cooler is disposed to cool exhaust gas passing through the second EGR passage
Implementation Method 2
The first and second EGR gas streams are arranged to mix and form a third EGR gas stream during operation of the internal combustion engine
Data Source
AI summary
Systems and methods for operating an engine include controlling a temperature of recirculated exhaust gas to achieve a predetermined recirculated exhaust gas temperature. A mixture of air and temperature-controlled recirculated exhaust gas are admitted in a combustion chamber and a gaseous fuel injector delivers gaseous fuel during an intake stroke. A diesel fuel injector is activated for a first time to deliver a pre-pilot diesel quantity directly into the combustion chamber at an early stage of a compression stroke, and is activated again for a second time to deliver a pilot diesel quantity directly into the combustion chamber at a later stage of the compression stroke. A total air/fuel ratio within the combustion chamber upon completion of the second diesel fuel injector activation is lean. The air/fuel mixture is combusted during a combustion stroke, and combustion products are removed during an exhaust stroke.