Cold Start Fuel Pressure Control for Otto Engines
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Solution Overview
Problem
Otto engines with direct fuel injection face challenges in starting reliably at low temperatures, particularly with fuel mixtures containing high proportions of alcohol, requiring additional costly measures such as heated injectors or additional gasoline injection, which increase consumption and emissions.
Innovation Solution
A control unit program routine increases the fuel pressure above the typical upper system pressure but below the maximum pressure, allowing for improved mixture preparation and eliminating the need for additional devices like heated injectors by adjusting the starting pressure based on temperature and fuel composition, enabling a reliable cold start without increased costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the fuel pressure is increased above the upper system pressure during cold start, then the fuel atomization and mixture preparation are improved, but the risk of exceeding the maximum system pressure increases
Solution Approach 1:
The pressure limiting valve is designed with a dynamically adjustable opening pressure that adapts to different operating conditions. During cold start, the opening pressure is temporarily increased to allow higher fuel pressure for improved atomization, while during normal operation it maintains the standard maximum pressure limit, thus resolving the contradiction between atomization quality and pressure safety
Solution Approach 2:
The system changes the key parameter of pressure limiting valve opening pressure based on engine operating temperature. At low temperatures, the opening pressure is raised to enable higher fuel pressure injection for better mixture preparation, while at normal temperatures it returns to standard limits, thereby achieving both improved cold start performance and ongoing pressure safety
2Reliability
If additional measures such as heated injectors or additional gasoline injection are used for cold start, then the starting reliability is improved, but the device complexity and cost increase
Solution Approach 1:
Instead of adding physical components, the invention changes the operating parameters of the existing high-pressure injection system. By temporarily increasing the fuel pressure above the normal upper system pressure during cold start conditions, the system achieves reliable cold starting with alcohol-containing fuels without requiring heated injectors or additional injection systems
Solution Approach 2:
The existing high-pressure pump and pressure limiting valve system is utilized to achieve cold start functionality. The pressure limiting valve's ability to adapt its opening pressure allows the system to serve its own cold start needs without external assistance from heated components or additional injection systems, thereby avoiding increased complexity
3Reliability
If the fuel pressure is limited to a maximum pressure by the pressure limiting valve, then the system safety is maintained, but the fuel atomization quality at cold start deteriorates
Solution Approach 1:
The pressure limiting valve transitions from a static pressure limit to a dynamic one that adapts to operating conditions. During cold start, it permits higher pressures for improved injection quality, while during normal operation it maintains safety limits, thus resolving the contradiction between safety and injection quality
Solution Approach 2:
The system prepares for cold start conditions by pre-configuring the pressure limiting valve to allow higher opening pressures when low temperature is detected. This preliminary adaptation of the pressure limit ensures that when cold start occurs, the fuel pressure can be sufficiently high for good atomization while still being protected by the adapted pressure limiting mechanism
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 ensures a reliable cold start of Otto engines at low temperatures without additional costly measures, improving fuel atomization and reducing fuel transfer into engine oil, thus optimizing engine operation and reducing emissions.
Implementation Method 1
a starting pressure, which lies between the upper system pressure and the maximum pressure
Implementation Method 2
the fuel pressure in the high pressure reservoir and in the high pressure system being limited to a maximum pressure by an opening pressure of a pressure limiting valve
Data Source
AI summary
A method and control unit for a start of an Otto engine operated at low temperatures, using ethanol and/or gasoline, having direct injection. The method includes generating by a high pressure pump a fuel pressure in a high pressure system connected to a high pressure reservoir; a sensor monitoring the fuel pressure in the reservoir and the system; injecting the fuel, by an injector, from the reservoir into a cylinder of the engine, the fuel pressure, an injection quantity and a fuel quantity being specified by a control unit based on, sensor the fuel pressure being specified based on the operating point of the engine up to an upper pressure which is below a starting pressure to which the fuel is increased before the fuel injection, and the fuel pressure in the reservoir and the system being limited to a maximum by an opening pressure of a limiting valve.