Road Tunnel Ventilation Bypass for Fire-Resilient Fan Operation
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Solution Overview
Problem
Existing ventilation systems for road tunnels face issues with reliability during fires due to resonance frequencies and brittle fractures at high temperatures, inefficient power consumption, and the need for easy implementation and economic competitiveness.
Innovation Solution
A ventilation system with a power supply and actuation apparatus that includes a temperature detection device and a motorized switching unit to switch between ordinary and emergency configurations, using an electrical bypass to maintain operation at high temperatures and reduce power consumption, while ensuring reliable air flow control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If speed variators are used to control fan speed, then power consumption is reduced, but the system becomes vulnerable to resonance frequencies and brittle fracture at high temperatures
Solution Approach 1:
The power supply system is segmented into two independent paths: an electronic control path with speed variator for normal operation, and a direct power supply path for emergency fire conditions. This segmentation allows the system to use the efficient electronic control during normal times while switching to the reliable direct path during fires, eliminating the vulnerability of the speed variator to resonance and temperature effects.
Solution Approach 2:
The system dynamically switches between two operational modes based on temperature conditions. During normal operation, the electronic speed control is active for energy efficiency. When temperature exceeds the threshold (fire detection), the system automatically transitions to direct power supply mode, making the power supply configuration adaptive to environmental conditions.
2Reliability
If fire-resistant cables and redundant power supplies are installed, then reliability during fire is improved, but system complexity and cost increase
Solution Approach 1:
The harmful electronic control components (speed variator, electronic converters) are extracted from the direct power path. The emergency power supply uses a simplified direct connection from the cable to the motor terminals, eliminating complex electronic equipment from the fire-critical path while maintaining reliability.
Solution Approach 2:
Different quality levels are applied to different parts of the power supply system. The normal operation path uses complex electronic control for efficiency, while the emergency path uses simple direct connection for reliability. The system applies appropriate complexity only where needed, avoiding unnecessary complexity in the fire-critical path.
3Ease of manufacture
If aluminum impeller is used, then manufacturing cost is reduced, but the impeller becomes susceptible to brittle fracture under variable-speed conditions at high temperatures
Solution Approach 1:
The system prepares for the brittle fracture risk by providing a backup direct power supply path that can activate when the electronic control becomes unsafe. This prior cushioning ensures that even if the aluminum impeller fails under variable-speed heating, the fan can continue operating in fixed mode or be restarted after cooling.
Data Source
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AI summary
A ventilation system (1) for road tunnels, which comprises at least one fan (90) and a power supply and actuation apparatus (10) which is connected to an electric power supply line (41) and supplies electric power to the fan (90), wherein the power supply and actuation apparatus (10) comprises an electronic control system configured to control the speed and the direction of rotation of the fan (90) and comprises an electrical conversion device (30) interposed between the power supply line (41) and the fan (90); and further comprising at least one temperature detection device; the power supply and actuation apparatus (10) comprises a motorized switching unit (20) which is configured to change, as a function of the temperature detected by the temperature detection device, the configuration of the power supply and actuation apparatus (10) from an ordinary configuration, in which the power supply and actuation apparatus (10) powers the fan (90) by means of the electrical conversion device (30), to an emergency configuration, in which the motorized switching unit (20) isolates the electrical conversion device (30), creating an electrical bypass so as to power the fan (90) directly from the electrical line (41), the electrical bypass being thermally isolated, and vice versa.