Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 5 Articles
Increasing demands on the capabilities of engine thermo-??uid dynamic simulation and the ability to accurately predict both\r\nperformance and acoustics have led to the development of several approaches, ranging from fully 3D to simpli??ed 1D models. ?e\r\nquasi-3D approach is proposed as a compromise between the time-demanding 3D CFD analysis and the fast 1D approach; it allows\r\nto model the acoustics of intake and exhaust system components, used in internal combustion engines, resorting to a 3D network\r\nof 0D cells. Due to its 3D nature, the model predicts high-order modes, improving the accuracy at high frequencies with respect\r\nto conventional plane-wave approaches. ?e conservation equations of mass and energy are solved at cell centers, whereas the\r\nmomentum equation is applied to cell connections including speci??c source term to account for the of sound-absorbing materials\r\nand perforated elements. ?e quasi-3D approach has been validated by comparing the predicted transmission loss to measured\r\ndata for a number of standard con??gurations typical of internal combustion engine exhaust systems: a reverse-??ow chamber and\r\nseries chambers with perforates and resistive material....
Based on the transmission and equilibrium relationship of vibration energy in beam-like structures, the Galerkin weighted residual\r\nmethod was applied to equation discretization. An equivalent transformation of feedback element was suggested to develop the\r\nEnergy Finite Element model of a composite piezoelectric cantilever beam driven by harmonic excitation on lateral direction, with\r\nboth systems with and without time delay being studied and the power input estimation of harmonic excitation was discussed for\r\nthe resolution of Energy Finite Element function. Then the energy density solutions of the piezoelectric coupling beam through\r\nEnergy Finite Element Method (EFEM) and classical wave theory were compared to verify the EFEM model, which presented a\r\ngood accordance. Further investigation was undertaken about the influence of control parameters including the feedback gain and\r\narrangement of piezoelectric patches on characteristics of system energy density distribution....
Tunnel ventilation fans, classically, must have the ability to both supply and extract air from a tunnel system, with the operator�s\r\nchoice dependent on the tunnel ventilation system�s operating mode most appropriate at any given point in time. Consequently,\r\ntunnel ventilation fans must incorporate a reversible aerodynamic design which limits the maximum fan pressure rise. This paper\r\npresents three high pressure reversible fan concepts. These comprise a two-stage counter rotating fan, a single-stage high speed\r\nfan, and a two-stage fan with a single motor and impeller on each end of the motor shaft. The authors consider the relative merits\r\nof each concept. The third concept offers the most compact fan, transform, silencer, and damper package size. The authors discuss\r\nthe mechanical design challenges that occur with a two-stage fan with a single motor and impeller on each end of the motor shaft.\r\nThey present and consider a selected motor bearing arrangement and casing design for maintainability. Finally, the authors present\r\nboth prototype fan and full-scale package aerodynamic and acoustic performance, before discussing the challenges presented by\r\nhigh temperature certification in accordance with the requirements of EN 12101-3: 2012....
Church bell ringing as practised in the UK involves large-amplitude motions of both bell and clapper. A simulation model is\r\ndeveloped and validated against experimental measurements. It is shown that the clapper does not hit the bell with a single impact\r\nbut a long series of bounces, and this has important consequences for the decay profile of the bell vibration. Information relevant\r\nto bell-ringers and bell-hangers is collected in a series of design charts derived from the simulation model. These charts can assist\r\nin the diagnosis and correction of faults. Arising from the analysis of the bouncing clapper, a more general result is also presented\r\nrelating to the frequency bandwidth when any structure is excited by a small bouncing impactor, for example an impulse hammer\r\nused in vibration testing....
This paper describes research involving an in-service failure of a ââ?¬Å?variable pitch in motionââ?¬Â fanââ?¬â?¢s blade bearing. Variable pitch in\r\nmotion fans rotate at a constant speed, with the changing blade angle varying the load. A pitch-change mechanism facilitates the\r\nchange in blade angle. A blade bearing supports each blade enabling it to rotate. The author observed that as the fan aerodynamic\r\nstage loading progressively increased, so did the rate of blade-bearing wear. The reported research addressed two separate, but\r\nlinked, needs. First, the ongoing need to increase fan pressure development capability required an increase in fan loading.\r\nThis increase was within the context of an erosive operating regime which systematically reduced fan pressure development\r\ncapability. The second need was to identify the root cause of blade-bearing failures. The author addressed the linked needs using\r\na computational analysis, improving the rotor inflow aerodynamic characteristics through an analysis of the inlet box and design\r\nof inlet guide vanes to control flow nonuniformities at the fan inlet. The results of the improvement facilitated both an increase in\r\nfan-pressure-developing capability and identification of the root cause of the blade-bearing failures....
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