Study On Inertia Effect And Linkage Control Of Urban Tunnel Ventilation

Many new urban tunnels are being built. They are generally geometrically complex to be linked with road traffic. The pollutant discharging must meet the surrounding air quality standards. So it is urgent for us to accomplish an effective ventilation control method that can discharge the pollutant at fixed points with desirable quantity. Therefore this study is carried out according to3key points of the urban tunnel ventilation system:dynamic characteristics of the flow field; linking and coupling features of series-parallel tunnel system and the optimized quantitative control model that can deal with multiple targets. Specifically,(1) The dynamic response of air flow to jet fan control inside the longitudinally ventilated tunnel is theoretically deduced. The nature of the flow inertia effect is uncovered, i.e., a rebalance process between motivation and resistance. Field verification and case study are conducted. The impact of main parameters of tunnel length, section, resistance coefficient and traffic parameters are studied. The system dynamic nonlinearity and coupling of parameters is quantitatively described.(2) A mathematic model is established, which is used to analyze the linking-coupling features of segmentally ventilated tunnels with ramp. The model can be solved by numerical integration. Take one real urban tunnel as an example, the influence of fan switches in parallel segments and the impact of air volume through the upper vents alone the series segments are mainly analyzed. It is quantitatively revealed that the pressure at parallel segments has balancing feature and the impact of the volume through the upper vents is subjected to conservation law. Moreover, the air flow speed in one segment is mainly subjected to the running fan numbers of itself and its adjacent segments, and this effect is linear with linearization parameters influenced by traffic intensity.(3) Based on the above results, an MIMO flow model is established for such series-parallel system. An optimal pollutant control method based on nonlinear programming is designed using the MIMO model. It aims to meet multi control constraints with minimal number of total running fans in the system. The method is tested easily in the real project by Matlab simulation program which integrates the flow field coupling equations with numerical solving of pollutant transport formula. The importance of the optimized control scheme is verified by the simulation results.