Pilot Injection Ignition for Gaseous Fuel Engines
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Solution Overview
Problem
Conventional methods for igniting gaseous fuels in Diesel-cycle internal combustion engines, such as natural gas, face challenges due to high auto-ignition temperatures and require additional fuel systems or glow plugs, leading to increased complexity, emissions, and reduced reliability.
Innovation Solution
A method and apparatus that involves heating a space near the fuel injector nozzle to the auto-ignition temperature of the gaseous fuel using a pilot injection, followed by a main fuel injection, where the pilot fuel auto-ignites and ignites the main fuel, with controlled residency and air entrainment to optimize combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pilot injection of gaseous fuel is used to auto-ignite and ignite the main fuel, then combustion efficiency is improved and emissions are reduced, but the complexity of the injection system increases due to multiple injection events
Solution Approach 1:
The fuel injection process is divided into multiple stages: a pilot injection event that introduces a small amount of gaseous fuel to auto-ignite, followed by a main injection event that introduces the bulk of the fuel. This segmentation allows controlled combustion initiation while maintaining a single fuel system architecture, resolving the contradiction between improved combustion efficiency and system complexity.
2Reliability
If glow plugs are used to ignite gaseous fuel, then ignition is achieved, but the reliability decreases due to multiple failure modes and the system complexity increases
Solution Approach 1:
The patent extracts and eliminates the glow plug component entirely, relying instead on the auto-ignition properties of gaseous fuel when injected into the high-temperature compression environment. This removes the reliability issues and complexity associated with glow plugs while maintaining effective ignition capability through the pilot injection strategy.
Solution Approach 2:
The gaseous fuel itself serves as the ignition source through its auto-ignition capability when exposed to compressed hot air. The pilot injection of gaseous fuel self-ignites under compression conditions, eliminating the need for external ignition devices like glow plugs or spark plugs, thereby improving reliability and reducing system complexity.
3Reliability
If diesel fuel is used as a pilot injection to ignite natural gas, then ignition is achieved, but the fuel system complexity increases due to requiring two fuel systems
Solution Approach 1:
The gaseous fuel injection system performs multiple functions: it serves as both the primary fuel source for combustion and the ignition source through pilot injection. By using the same gaseous fuel for both purposes rather than requiring separate diesel and natural gas systems, the patent eliminates the need for dual fuel storage vessels, pumping systems, and injection hardware, thereby reducing complexity while maintaining reliable ignition.
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 enhances combustion efficiency, reduces emissions, and simplifies the fuel system, improving reliability and meeting stringent emission regulations while extending the operating life of ignition components.
Implementation Method 1
A surface at the tip heats when a current passes through the heating element due to its electrical resistance
Implementation Method 2
natural gas does not reliably ignite from the heat of compression like diesel fuel for the range of compression ratios previously mentioned. As a result an ignition source is required to ignite natural gas in a Diesel-cycle engine
Implementation Method 3
using heat from combustion of the pilot amount to ignite the main amount
Data Source
Figure 1
Figure 2a~2c
Figure 3a~3f
AI summary
An apparatus and method for igniting a gaseous fuel directly introduced into a combustion chamber of an internal combustion engine comprises steps of heating a space near a fuel injector nozzle; introducing a pilot amount of the gaseous fuel in the combustion chamber during a first stage injection event; controlling residency of the pilot amount in the space such that a temperature of the pilot amount increases to an auto-ignition temperature of the gaseous fuel whereby ignition occurs; introducing a main amount of the gaseous fuel during a second stage injection event after the first stage injection event; and using heat from combustion of the pilot amount to ignite the main amount.