Exhaust Valve Timing Control for Premixed Compression Ignition Engines
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Solution Overview
Problem
Conventional control apparatuses for four-stroke premixed compression ignition internal combustion engines face challenges in maintaining high fuel efficiency when engine load increases, as they struggle to introduce sufficient air into the combustion chamber without excessively decreasing the lift of the exhaust valve, leading to increased pumping loss.
Innovation Solution
A control apparatus with an intake-valve control portion and an exhaust-valve control portion that manages the opening and closing timings of intake and exhaust valves to allow air introduction during the intake stroke and reintroduction of burned gas through the exhaust port, retarding the second exhaust-valve opening timing as load increases, thereby avoiding the need for extremely small exhaust valve lift and reducing pumping loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the lift of the exhaust valve is decreased to an extremely small value to decrease the amount of burned gas introduced into the combustion chamber, then the amount of burned gas is reduced, but the pumping loss is increased due to resistance against the burned gas
Solution Approach 1:
The exhaust valve operation is divided into two distinct phases: a first exhaust valve open period during the exhaust stroke for normal exhaust gas discharge, and a second exhaust valve open period during the intake stroke for controlled burned gas reintroduction. This segmentation allows independent optimization of each phase's function, enabling burned gas reduction without excessive pumping loss by separating the exhaust and reintroduction operations into distinct time windows with different valve lift requirements.
Solution Approach 2:
The exhaust valve lift is made dynamically adjustable through two different open periods with potentially different lift characteristics. During the first open period, the valve operates with normal lift for efficient exhaust discharge. During the second open period, the valve operates with reduced lift to control burned gas reintroduction. This dynamic adjustment resolves the contradiction by adapting valve lift to the specific operational requirements of each phase.
2Quantity of substance
If the lift of the exhaust valve is decreased to decrease the amount of burned gas introduced into the combustion chamber, then the burned gas amount is reduced, but a sufficient amount of air is not introduced into the combustion chamber when the load is high
Solution Approach 1:
The exhaust valve operation is divided into two distinct phases: a first exhaust valve open period during the exhaust stroke for normal exhaust gas discharge, and a second exhaust valve open period during the intake stroke for controlled burned gas reintroduction. This segmentation allows independent optimization of each phase's function, enabling burned gas reduction without excessive pumping loss by separating the exhaust and reintroduction operations into distinct time windows with different valve lift requirements.
Solution Approach 2:
The exhaust valve lift is made dynamically adjustable through two different open periods with potentially different lift characteristics. During the first open period, the valve operates with normal lift for efficient exhaust discharge. During the second open period, the valve operates with reduced lift to control burned gas reintroduction. This dynamic adjustment resolves the contradiction by adapting valve lift to the specific operational requirements of each phase.
3Quantity of substance
If the exhaust valve is reopened at a fixed timing during the intake stroke to introduce burned gas, then burned gas is introduced when the load is low, but the amount of air introduced is insufficient when the load increases
Solution Approach 1:
The exhaust valve timing is made dynamically adjustable through two different open periods. The first open period occurs during the exhaust stroke at a fixed timing, while the second open period occurs during the intake stroke at a timing that can be adjusted based on engine load. This dynamic timing adjustment allows the system to introduce burned gas at appropriate times for low load conditions while prioritizing air introduction for high load conditions, resolving the contradiction between burned gas introduction and air supply requirements.
Solution Approach 2:
The exhaust valve opening timing is changed as a variable parameter based on engine load conditions. At low load, the second open period is timed to allow burned gas reintroduction. At high load, the timing is adjusted to prioritize air introduction. This parameter change approach allows the system to adapt to different operational requirements, resolving the contradiction between maintaining burned gas introduction and ensuring sufficient air supply.
Data Source
AI summary
A control apparatus for a four-stroke premixed compression ignition internal combustion engine opens an exhaust valve to discharge burned gas from a combustion chamber at a first exhaust-valve opening timing, and reopens the exhaust valve at a second exhaust-valve opening timing that is retarded with respect to the intake-valve opening timing. Thus, burned gas discharged from the combustion chamber flows back into the combustion chamber through the exhaust port. The control apparatus retards the second exhaust-valve opening timing as the load on the engine increases. This obviates the need to decrease the lift of the exhaust valve to decrease the amount of burned gas that is reintroduced into the combustion chamber and prevents increases in the resistance against the flow of burned gas into the combustion chamber.