【正文】 d 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 Trap retention。本科畢業(yè)設(shè)計(jì)外文文獻(xiàn)及譯文文獻(xiàn)、資料題目 ： Sealed building drainage and vent systems文獻(xiàn)、資料來源 ： 國(guó)道數(shù)據(jù)庫(kù)文獻(xiàn)、資料發(fā)表（出版）日期 ： 院 （部）： 市政與環(huán)境工程學(xué)院專 業(yè) ： 給水排水工程班 級(jí)： 水工122姓 名 ： 楊濤學(xué) 號(hào) ： 20120411048指導(dǎo)教師 ： 譚鳳訓(xùn)翻譯日期 ： 山東建筑大學(xué)畢業(yè)設(shè)計(jì)外文文獻(xiàn)及譯文外文文獻(xiàn)：Sealed building drainage and vent systems—an application of active air pressure transient control and suppressionAbstractThe introduction of sealed building drainage and vent systems is considered a viable proposition for plex buildings due to the use of active pressure transient control and suppression in the form of air admittance valves and positive air pressure attenuators coupled with the interconnection of the network39。s vertical stacks. This paper presents a simulation based on a fourstack network that illustrates flow mechanisms within the pipework following both appliance discharge generated, and sewer imposed, transients. This simulation identifies the role of the active air pressure control devices in maintaining system pressures at levels that do not deplete trap seals. Further simulation exercises would be necessary to provide proof of concept, and it would be advantageous to parallel these with laboratory, and possibly site, trials for validation purposes. Despite this caution the initial results are highly encouraging and are sufficient to confirm the potential to provide definite benefits in terms of enhanced system security as well as increased reliability and reduced installation and material costs. Keywords: Active control。 Transient propagation NomenclatureC+——characteristic equations c——wave speed, m/s D——branch or stack diameter, m f——friction factor, UK definition via Darcy Δh=4fLu2/2Dgg——acceleration due to gravity, m/s2 K——loss coefficient L——pipe length, m p——air pressure, N/m2 t——time, s u——mean air velocity, m/s x——distance, mγ——ratio specific heats Δh——head loss, m Δp——pressure difference, N/m2 Δt——time step, s Δx——internodal length, m ρ——density, kg/m3Article OutlineNomenclature 1. Introduction—air pressure transient control and suppression2. Mathematical basis for the simulation of transient propagation in multistack building drainage networks 3. Role of diversity in system operation 4. Simulation of the operation of a multistack sealed building drainage and vent system 5. Simulation sign conventions 6. Water discharge to the network 7. Surcharge at base of stack 1 8. Sewer imposed transients 9. Trap seal oscillation and retention 10. Conclusion—viability of a sealed building drainage and vent system pressure transients generated within building drainage and vent systems as a natural consequence of system operation may be responsible for trap seal depletion and cross contamination of habitable space [1]. Traditional modes of trap seal protection, based on the Victorian engineer39。s and 300mm in the UK and other international standards dependent upon appliance type. Trap seal retention is therefore defined as a depth less than the initial value. Many standards, recognizing the transient nature of trap seal depletion and the opportunity that exists for recharge on appliance discharge allow 25% depletion. The boundary equation may also be determined by local conditions: the AAV opening and subsequent loss coefficient depends on the local line pressure prediction. Empirical data identifies the AAV opening pressure, its loss coefficient during opening and at the fully open condition. Appliance trap seal oscillation is treated as a boundary condition dependent on local pressure. Deflection of the trap seal to allow an airpath to,or from, the appliance or displacement leading to oscillation alone may both be modelled. Reductions in trap seal water mass during the transient interaction must also be included. 3. Role of diversity in system operationIn plex building drainage networks the operation of the system appliances to discharge water to the network, and hence provide the conditions necessary for air entrainment and pressure transient propagation, is entirely random. No two systems will be identical in terms of their usage at any time. This diversity of operation implies that interstack venting paths will be established if the individual stacks within a plex building network are themselves interconnected. It is proposed that this diversity is utilized to provide venting and to allow serious consideration to be given to sealed drainage systems. In order to fully implement a sealed building drainage and vent system it would be necessary for the negative transients to be alleviated by drawing air into the network from a secure space and not from the external atmosphere. This may be achieved by the use of air admittance valves or at a predetermined location within the building, for example an accessible loft space. Similarly, it would be necessary to attenuate positive air pressure transients by means of PAPA devices. Initially it might be considered that this would be problematic as positive pressure could build within the PAPA installations and therefore negate their ability to absorb transient airflows. This may again be avoided by linking the vertical stacks in a plex building and utilizing the diversity of use inherent in building drainage systems as this will ensure that PAPA pressures are themselves alleviated by allowing trapped air to vent through the interconnected stacks to the sewer network. Diversity also protects the proposed sealed system from sewer driven overpressure and positive transients. A plex building will be interconnected to the main sewer network via a number of connecting smaller bore drains. Adverse pressure conditio