【正文】 seal water. This overall effect results in each trap displaying an individual water seal retention that depends entirely on the usage of the network. Trap 2 retains 32mm water seal while traps 7 and 15 retain 33mm. Trap 20 is reduced to 26mm water seal. Note that the traps on pipes 7 and 15 were exposed to the same levels of transient pressure despite the time difference in arrival of the sewer transients. Fig. 11(a) and (b) illustrate the oscillations of the trap seal column as a result of the solution of the trap seal boundary condition, Eq. (10), with the appropriate C+ characteristic. This boundary condition solution continually monitors the water loss from the trap and at the end of the event yields a trap seal retention value. In the example illustrated the initial trap seal values were taken as 50mm of water, mon for appliances such as .39。當(dāng)吸氣閥直接反映本地壓力條件時，它們代表了一種控制活性氣壓的解決方法，它們自動打開，使新鮮空氣進入管道系統(tǒng)，從而使系統(tǒng)的壓力得到平衡并保護了冰封[9]。s into the simulation. The air pressure in stack 4 demonstrates a pressure gradient patible with the reversed airflow mentioned above. The air pressure profile in stack 1 is typical for a stack carrying an annular water downflow and demonstrates the establishment of a positive backpressure due to the water curtain at the base of the stack. pressure profile in stacks 1 and 4 illustrating the pressure gradient driving the reversed airflow in pipe 19. The initial collapsed volume of the PAPA installed on pipe 13 was , with a fully expanded volume of 40l, however due to its small initial volume it may be regarded as collapsed during this phase of the simulation. 7. Surcharge at base of stack 1Fig. 6 indicates a surcharge at the base of stack 1, pipe 1 from to 3s obsession with odour exclusion [2], [3] and [4], depend predominantly on passive solutions where reliance is placed on cross connections and vertical stacks vented to atmosphere [5] and [6]. This approach, while both proven and traditional, has inherent weaknesses, including the remoteness of the vent terminations [7], leading to delays in the arrival of relieving reflections, and the multiplicity of open roof level stack terminations inherent within plex buildings. The plexity of the vent system required also has significant cost and space implications [8]. The development of air admittance valves (AAVs) over the past two decades provides the designer with a means of alleviating negative transients generated as random appliance discharges contribute to the time dependent waterflow conditions within the system. AAVs represent an active control solution as they respond directly to the local pressure conditions, opening as pressure falls to allow a relief air inflow and hence limit the pressure excursions experienced by the appliance trap seal [9]. However, AAVs do not address the problems of positive air pressure transient propagation within building drainage and vent systems as a result of intermittent closure of the free airpath through the network or the arrival of positive transients generated remotely within the sewer system, possibly by some surcharge event downstream—including heavy rainfall in bined sewer applications. The development of variable volume containment attenuators [10] that are designed to absorb airflow driven by positive air pressure transients pletes the necessary device provision to allow active air pressure transient control and suppression to be introduced into the design of building drainage and vent systems, for both ‘standard’ buildings and those requiring particular attention to be paid to the security implications of multiple roof level open stack terminations. The positive air pressure attenuator (PAPA) consists of a variable volume bag that expands under the influence of a positive transient and therefore allows system airflows to attenuate gradually, therefore reducing the level of positive transients generated. Together with the use of AAVs the introduction of the PAPA device allows consideration of a fully sealed building drainage and vent system. Fig. 1 illustrates both AAV and PAPA devices, note that the waterless sheath trap acts as an AAV under negative line pressure.Fig. 1. Active air pressure transient suppression devices to control both positive and negative surges.Active air pressure transient suppression and control therefore allows for localized intervention to protect trap seals from both positive and negative pressure excursions. This has distinct advantages over the traditional passive approach. The time delay inherent in awaiting the return of a relieving reflection from a vent open to atmosphere is removed and the effect of the transient on all the other system traps passed during its propagation is avoided. basis for the simulation of transient propagation in multistack building drainage networks.The propagation of air pressure transients within building drainage and vent systems belongs to a well understood family of unsteady flow conditions defined by the St Venant equations of continuity and momentum, and solvable via a finite difference scheme utilizing the method of characteristics technique. Air pressure transient generation and propagation within the system as a result of air entrainment by the falling annular water in the system vertical stacks and the reflection and transmission of these transients at the system boundaries, including open terminations, connections to the sewer, appliance trap seals and both AAV and PAPA active control devices, may be simulated with proven accuracy. The simulation [11] provides local air pressure, velocity and wave speed information throughout a network at time and distance intervals as short as 關(guān)鍵詞：活性氣壓控制，存水彎保持，瞬變傳播。6．排入管網(wǎng)的水7．立管1底部排水8．瞬時氣壓強加于污水管9．水封的振動和保持——密封建筑排水和通氣系統(tǒng)的可行性――瞬時氣壓的控制和抑制作為系統(tǒng)操作的自然結(jié)果，建筑排水系統(tǒng)和通氣系統(tǒng)內(nèi)部產(chǎn)生的氣壓瞬變對于水封破壞和交叉污染的可居住空間來說也是可靠的。mm. In addition, the simulation replicates local appliance trap seal oscillations and the operation of active control devices, ther