Compression Ratio Mechanism With Orifice Oil Control Against Cavitation
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Solution Overview
Problem
The plunger pump in crosshead type engines experiences rapid oil suction near the bottom dead center, leading to negative supply pressure and potential cavitation.
Innovation Solution
A compression ratio varying mechanism is introduced, featuring a pump cylinder with first and second oil storage chambers, a communication passage, and an orifice, along with a bypass oil passage and check valve, to manage oil flow and pressure, preventing cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the plunger pump quickly sucks working oil near the bottom dead center to change the top dead center position, then the compression ratio can be varied, but the supply pressure becomes negative and cavitation may occur
Solution Approach 1:
The communication passage allows working oil to be preliminarily supplied to the second oil storage chamber before the plunger pump needs to discharge it. This advance preparation ensures that oil is already positioned and pressurized, preventing negative pressure and cavitation during the rapid discharge phase when compression ratio variation is needed
Solution Approach 2:
The second oil storage chamber acts as an intermediary between the plunger pump and the hydraulic chamber. It buffers the oil supply, allowing the pump to discharge oil rapidly for compression ratio variation while the intermediary chamber maintains stable pressure and prevents cavitation
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 configuration effectively suppresses cavitation by controlling oil flow and pressure, ensuring stable operation of the engine.
Implementation Method 1
an orifice provided in the communication passage
Implementation Method 2
a check valve, which is provided in the bypass oil passage, and is configured to limit a flow of working oil from the second oil storage chamber to the first oil storage chamber
Implementation Method 3
The plunger pump supplies working oil to a hydraulic chamber formed between the piston rod and the crosshead pin
Data Source
AI summary
Provided is a compression ratio varying mechanism, including: a discharge oil passage connected to a first hydraulic chamber; a supply oil passage connected to a hydraulic pump; a pump cylinder including a first oil storage chamber connected to the discharge oil passage and the supply oil passage and a second oil storage chamber partitioned from the first oil storage chamber by a plunger; a branch oil passage connected to the second oil storage chamber; and an orifice provided in the branch oil passage.