Glow Plug Projecting Portion Geometry for Diesel Combustion Noise
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Solution Overview
Problem
Conventional subchamber type combustion chambers for diesel engines experience high fuel consumption rates and combustion noise due to excessive heat loss and abrupt premixed combustion, primarily caused by a large surface area of the projecting portion of the glow plug, leading to inefficient heat retention and delayed ignition.
Innovation Solution
The design modifies the glow plug's projecting portion to have a convex curved surface with a reduced diameter, optimizing the P/D ratio between 3% to 23%, and the S1/S2 ratio of the projecting surface area to the subchamber surface area within specific ranges, along with a controlled extension dimension and compression ratio, to minimize heat loss and promote uniform air-fuel mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the projecting portion of the glow plug has a large surface area (P/D ratio of approximately 50%), then the glow plug can provide sufficient heating surface for cold starting, but combustion heat escapes excessively during engine operation resulting in high fuel consumption rate
Solution Approach 1:
The invention changes the geometric parameters of the glow plug projecting portion by controlling the P/D ratio to be 25% or less. This parameter optimization reduces the surface area of the projecting portion, thereby reducing combustion heat loss during engine operation while maintaining adequate cold starting performance through the optimized dimensional relationship between projection height and diameter.
2Reliability
If the projecting portion of the glow plug has a large surface area (P/D ratio of approximately 50%), then the glow plug provides extensive heating surface, but abrupt premixed combustion occurs due to delayed ignition resulting in high combustion noise
Solution Approach 1:
The invention optimizes the geometric parameters of the glow plug by limiting the P/D ratio to 25% or less. This parameter change accelerates ignition timing by reducing heat loss, thereby preventing abrupt premixed combustion and reducing combustion noise while maintaining cold starting capability.
3Temperature
If the projection dimension P of the glow plug is increased, then the heating surface area increases for better cold starting, but the surface area becomes too large causing excessive heat loss during operation
Solution Approach 1:
The invention optimizes the projection dimension P relative to the diameter D by setting the P/D ratio to 25% or less. This proportional parameter change ensures that the heating surface area is sufficient for cold starting while preventing excessive heat loss during normal operation by maintaining an optimal geometric relationship.
Solution Approach 2:
The invention applies local quality optimization by specifically designing the projecting portion with controlled dimensions (P/D ≤ 25%) to achieve different functional requirements: sufficient heating surface for cold starting versus minimal heat loss for efficient operation. The local geometric configuration is optimized to balance these conflicting requirements.
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 reduces fuel consumption rates and combustion noise while maintaining high cold starting performance by optimizing heat retention and combustion efficiency, as demonstrated through experimental comparisons with engines using values outside the specified ranges.
Implementation Method 1
a glow plug (5) extends into the subchamber (1)... a heat generating portion (6) of the glow plug (5) includes a rod-shaped portion (7) and a projecting portion (8)
Implementation Method 2
the convex curved surface (8a) is reduced in diameter... reduce fuel consumption rate and combustion noise... reduce heat loss
Implementation Method 3
a fuel injection nozzle (4) faces into the subchamber (1)... injected fuel is made uniform, thereby realizing good and gentle combustion
Implementation Method 4
compressed air pushed from the main combustion chamber (2) through the nozzle hole (3)... in a compression stroke
Implementation Method 5
premixed combustion in the subchamber (1)... combusted in the main combustion chamber (2)... combustion efficiency
Data Source
AI summary
A subchamber type combustion chamber for a diesel engine, which reduces fuel consumption rate and combustion noise. To achieve the object, a subchamber type combustion chamber is communicated with a main combustion chamber through a nozzle hole, a fuel injection nozzle faces into the subchamber, and a glow plug extends into the subchamber. A heat generating portion of the glow plug includes a rod-shaped portion and a projecting portion projecting from an end of the rod-shaped portion. The projecting portion is provided with a convex curved surface projecting from a circular peripheral edge at the end of the rod-shaped portion while the convex curved surface is reduced in diameter. The percentage of value P/D obtained by dividing projection dimension P of the projecting portion from the end of the rod-shaped portion by diameter dimension D at the end of the rod-shaped portion is 3% to 23%.