Common Rail Thermal Isolation in Multi-Cylinder Engines
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Solution Overview
Problem
The common rail in multi-cylinder engines is not sufficiently isolated from the cylinder head, leading to overheating and potential damage due to combustion heat conduction, which poses challenges during both manufacturing and maintenance.
Innovation Solution
The common rail is isolated from the cylinder head by positioning the intake-air distributing passage wall between them, and flange portions are strategically placed above the common rail to intercept falling objects and facilitate cooling with engine-cooling air, reducing the risk of overheating and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the common rail is arranged around the cylinder head for compact design, then the engine structure is more compact, but the common rail is not sufficiently isolated from the cylinder head and is easily damaged by combustion heat
Solution Approach 1:
An insulating member (heat insulating plate) is introduced as an intermediary substance between the cylinder head and the common rail. This plate is made of heat-insulating material and is positioned to cover the surface of the cylinder head that contacts the common rail, thereby blocking heat conduction from the cylinder head to the common rail while maintaining the compact arrangement.
2Area of stationary object
If the common rail is positioned close to the cylinder head for space efficiency, then space utilization is improved, but the common rail is susceptible to damage from falling objects during manufacture and maintenance
Solution Approach 1:
A protective cover is provided that can cover the common rail before damage occurs. The protective cover is positioned above the common rail and extends to cover it, preventing falling objects from directly contacting and damaging the common rail during manufacture, assembly, and maintenance operations.
Solution Approach 2:
The protective cover acts as an intermediary protective barrier between falling objects and the common rail. It absorbs or deflects the impact of falling objects, preventing direct contact with the common rail and thereby protecting it from damage.
3Temperature
If the common rail is isolated from the cylinder head using heat insulating material, then overheating is prevented, but the device complexity increases
Solution Approach 1:
The insulating member is integrated with existing engine components rather than being a completely separate addition. It is positioned to utilize the space between the cylinder head and common rail, and can be combined with the protective cover function, thereby achieving heat insulation without proportionally increasing device complexity.
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 arrangement effectively prevents overheating of the common rail, reduces the likelihood of damage during manufacturing and maintenance, and allows for easier maintenance access while also aiding in the reduction of NOx production by diffusing EGR gas heat into engine-cooling air.
Implementation Method 1
the intake-air distributing passage wall 2 isolates the common rail 10 from the cylinder head 1. Accordingly very little of the combustion heat of the engine is conducted to the common rail 10
Implementation Method 2
if parts, tools or other objects fall in an upper region of the engine, the intake-air flange portion 12 can intercept those substances before they collide with the common rail 10, and thereby reduce the likelihood of damage to the common rail 10
Implementation Method 3
the heat of the EGR gas is diffused from the EGR valve case 8 into the engine-cooling air through the flange portion 14 whereby to lower the temperature of the EGR gas
Data Source
Figure 1
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AI summary
A multi-cylinder engine comprising a cylinder head (1) which has on one side an intake-air distributing passage wall (2) and on another side an exhaust-gas converging passage wall (3), a common rail (10) being arranged around the cylinder head (1). In this multi-cylinder engine, the common rail (10) is arranged immediately laterally of the intake-air distributing passage wall (2), thereby positioning the intake-air distributing passage wall (2) between the cylinder head (1) and the common rail (10). Preferably., an intake-air inlet pipe (11) stand ups at an upper portion of the intake-air distributing passage wall (2) and is provided with an intake-air flange portion (12), which is positioned just above the common rail (10).