Cold Start Pilot Fuel Injection Pressure Control
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Solution Overview
Problem
Internal combustion engines fueled with gaseous fuel and a pilot fuel face challenges in cold starting due to reduced ignitability and combustion efficiency, as the ambient air temperature lowers, making it difficult to maintain suitable pilot fuel injection pressure and ensure reliable ignition.
Innovation Solution
A method and apparatus that determine whether a normal or cold start condition exists, adjusting the pilot fuel injection pressure and timing by using a controller to introduce pilot fuel at a higher pressure during cold starts, and selectively introducing gaseous fuel, with advanced start of injection timing and increased pilot fuel quantity to enhance ignition, utilizing a pumping apparatus and fuel injectors to manage pressures and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is cold started with gaseous fuel and pilot fuel using conventional compression ignition, then the engine can start under normal conditions, but the ignitability and combustion efficiency are reduced when ambient air temperature is low
Solution Approach 1:
The patent changes the pressure parameter of pilot fuel injection to resolve the cold start problem. During cold start conditions (when ambient temperature is below a threshold), the system increases pilot fuel injection pressure above the normal threshold pressure. This pressure increase ensures adequate pilot fuel delivery despite slower pump operation at low temperatures, enabling reliable ignition and combustion when conventional compression ignition becomes unreliable due to low combustion chamber temperatures.
2Device complexity
If a pump mechanically driven by power take-off is used to pressurize pilot fuel, then the system is simple, but the pump turns slower during cold start causing pilot fuel pressure to drop below injection pressure
Solution Approach 1:
The patent applies dynamics by making the pilot fuel injection pressure threshold dynamic rather than fixed. The control system adjusts the pressure threshold based on operating conditions: during cold start, the threshold is raised to account for the slower pump speed and lower pressure generation. This dynamic adjustment allows the system to maintain adequate injection pressure despite the mechanical pump's reduced performance at low temperatures, while keeping the overall system simple with no additional pressurization hardware.
3Reliability
If more pilot fuel is introduced during cold start to ensure reliable ignition, then combustion reliability improves, but maintaining suitable pilot fuel injection pressure becomes more challenging
Solution Approach 1:
The patent employs feedback control through the controller that monitors pilot fuel pressure and adjusts injection timing and quantity accordingly. During cold start, the controller detects low temperature conditions and adjusts the injection strategy to deliver adequate pilot fuel quantity while maintaining appropriate pressure levels. This feedback mechanism ensures that increased pilot fuel quantity does not compromise pressure maintenance, resolving the contradiction between needing more fuel for reliable ignition and the challenge of maintaining injection pressure with a slower-moving mechanical pump.
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 effectively extends the cold ambient temperature range for starting internal combustion engines, improving the likelihood of successful engine start without unnecessary delays, by maintaining pilot fuel pressure and enhancing combustion efficiency during cold conditions.
Implementation Method 1
a pumping apparatus pressurizes pilot fuel received from the pilot fuel supply
Implementation Method 2
a fuel injector is in fluid communication with the pumping apparatus and is configured to directly introduce pilot fuel into a combustion chamber
Implementation Method 3
The auto-ignition temperature for typical gaseous fuels, such as natural gas, is too high for compression ignition to reliably occur in internal combustion engines employing conventional compression ratios
Implementation Method 4
combustion of the diesel fuel triggers ignition of the gaseous fuel therein
Data Source
AI summary
Starting a gaseous fuelled engine employing a pilot fuel at cold temperatures is challenging due to reduced ignitability and combustion efficiency of the fuel(s), and the increased viscosity of engine oil. A technique for starting a compression ignition, gaseous fuelled internal combustion engine employing a pilot fuel comprises determining one of a normal start condition and a cold start condition; during the normal start condition, introducing the pilot fuel into a combustion chamber of the internal combustion engine when the pilot fuel pressure rises above a first pressure; during the cold start condition, introducing the pilot fuel into the combustion chamber when the pilot fuel pressure rises above a second pressure that is higher than the first pressure; and selectively introducing the gaseous fuel into the combustion chamber.