Fuel Tank Volume Modifying Element for Diurnal Loss Reduction
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Solution Overview
Problem
Current motor vehicle tank systems face challenges in minimizing gaseous fuel emissions, particularly 'diurnal losses' and operational emissions, due to vapor pressure equilibrium, which are regulated by stringent zero-emission standards, and existing solutions like flexible air bags or storage units are either expensive or inefficient.
Innovation Solution
A tank system with a volume change element connected to the environment through a storage unit for gaseous fuel components, allowing controlled exchange of air to manage pressure fluctuations and retain gaseous fuel components, using a controllable valve unit to manage pressure limits and incorporate a low-bleed emission activated carbon filter for efficient emission control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a flexible air bag is provided in the fuel tank to compensate for volume changes, then pressure fluctuations are reduced, but gaseous fuel components can still escape into the environment
Solution Approach 1:
A controllable valve unit is introduced as an intermediary between the flexible air bag compensating volume and the environment. This valve selectively controls when gaseous fuel components can be discharged, allowing volume compensation while preventing harmful emissions under normal operating conditions.
Solution Approach 2:
The system changes the operational parameters of the flexible air bag by controlling its connection to the environment through the valve unit. The valve responds to pressure parameter changes, opening only when necessary to maintain pressure equilibrium while minimizing emissions.
2Object-generated harmful factors
If pressure tanks are used to maintain high overpressure and prevent vapor escape, then gaseous fuel emissions are reduced, but the system becomes very expensive
Solution Approach 1:
Instead of maintaining high overpressure throughout the entire tank system, the invention applies partial pressure control only to the flexible air bag compensating volume. The valve unit maintains slight positive pressure in the compensating volume only when necessary, reducing the overall system complexity and cost while still preventing emissions.
Solution Approach 2:
The system dynamically changes pressure parameters in the compensating volume based on operating conditions. The valve unit adjusts pressure levels rather than maintaining constant high overpressure, reducing the need for expensive pressure-resistant tank construction while still preventing vapor escape.
3Stress or pressure
If the controllable valve unit is opened frequently to discharge gaseous fuel components, then pressure equilibrium is maintained, but more gaseous fuel emissions occur
Solution Approach 1:
The controllable valve unit incorporates feedback control based on pressure differential detection. The valve opens only when the pressure differential between the compensating volume and environment exceeds a predetermined threshold, maintaining pressure equilibrium while minimizing the frequency of openings and associated emissions.
Solution Approach 2:
The valve unit is designed to open rapidly when pressure thresholds are exceeded, allowing quick pressure equalization in a single controlled event rather than prolonged or repeated openings, thereby minimizing total emissions while maintaining equilibrium.
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
The system effectively reduces gaseous fuel emissions by maintaining a stable pressure environment within the tank, allowing the volume change element to compensate for volume changes while minimizing the escape of gaseous fuel components, thus meeting stringent emission regulations with reduced complexity and cost.
Implementation Method 1
the loss of gaseous fuel components or the amount of gaseous hydrocarbon emissions that occur when the motor vehicle is stationary for a long time due to temperature fluctuations (e.g. resulting from the change between day and night)
Implementation Method 2
these emissions that do not occur when the fuel tank is filled are temporarily stored in an activated carbon filter or the like, which is generally referred to here as a storage unit for gaseous fuel components
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a tank system of a motor vehicle comprising a volume modifying element (11) which is provided in the inner chamber of the fuel tank (1) and which is used to equalize the vapor pressure and said compensation volume is connected to the surrounding area (U). The only connection between the volume modifying element (11) and the surrounding area is formed by a storage unit (8) of the gaseous fuel components and the inner chamber of the fuel tank (1) is connected to the surrounding area (U) by means of a valve unit (7), which is normally open when filling the fuel tank (1) and when exceeding or falling below the pressure limits in the inner chamber of the tank, and is otherwise closed, and the storage unit (8) is connected to said valve unit (7) used for gaseous fuel components. Said volume modifying element (11) and the valve unit (7) are designed in such a way that vehicles which are parked for several days do not undergo "diurnal losses" due to the changes in temperature of the surroundings, due to the fact that the vapour pressure equilibrium in the fuel tank (1) can be maintained by the automatic supply and removal of ambient air in the or from the volume modifying element (11) as long as the valve unit (7) remains closed.