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Chiu M.-C.,ChungChou Institute of Technology
Transactions of the Canadian Society for Mechanical Engineering | Year: 2010

Because of the necessity of maintenance and operation in industries in which the equipment layout is occasionally tight, the space for a muffler is constrained. An interest in maximizing the acoustical performance of mufflers within a limited space is of paramount importance. As mufflers hybridized with reverse-flow ducts may visibly increase acoustical performance, the main purpose of this paper is to numerically analyze and maximize their acoustical performance within a limited space. In this paper, a four-pole system matrix for evaluating the acoustic performance -sound transmission loss (STL)- is derived by using a decoupled numerical method.Moreover, simulated annealing (SA), a robust scheme used to search for the global optimum by imitating the metal annealing process, has been used during the optimization process. Before dealing with a broadband noise, the STL's maximization with respect to a one-tone noise (300 Hz) is introduced for a reliability check on the SA method. Moreover, an accuracy check of the mathematical model is performed. Results reveal that the STL of a muffler with reverse-flow perforated ducts can be maximized at the desired frequency for pure tone elimination; moreover, the noise reduction for a broadband noise can reach 97.5 dB. Consequently, the approach used for the optimal design of the mufflers is simple and effective.


Chiu M.-C.,ChungChou Institute of Technology
Journal of Marine Science and Technology | Year: 2010

Research on new techniques of multi-chamber mufflers equipped with a side inlet and an internal non-perforated tube has been well addressed and developed; however, the research work of multi-chamber mufflers in conjunction with side inlet and internal perforated tubes which may efficiently increase the acoustical performance is rare. Therefore, the main purpose of this paper is to not only analyze the sound transmission loss (STL) of three-chamber side mufflers with a perforated tube but also to optimize their best design shape under a limited space. In this paper, both the generalized decoupling technique and plane wave theory in solving the coupled acoustical problem are used. The four-pole system matrix in evaluating the acoustic performance is also deduced in conjunction with a simulated algorithm (SA). To verify the liability of the SA technique, the noise minimization of muffles at a targeted frequency is exemplified first. To appreciate the acoustical performance of various multi-chamber mufflers with/without inner perforated tube, three kinds of multi-chamber mufflers -a one-chamber side muffler, a two-chamber side muffler hybridized with a non-perforated tube, and a three-chamber side muffler hybridized with a perforated tube are introduced and assessed. In eliminating the broadband exhausted noise emitted from an air compressor's inlet. Before the SA operation can be carried out, the accuracies of the mathematical models have to be checked by experimental data. The result reveals a three-chamber side muffler hybridized with a perforated tube exhibits an excellent acoustical ability beyond the other mufflers. Consequently, the approach used seeking the optimal design of the STL proposed in this study is indeed easy, economical and quite effective.


Chiu M.C.,ChungChou Institute of Technology
Journal of Marine Science and Technology | Year: 2010

Shape optimization on mufflers within a limited space is essential for industry where the equipment layout is occasionally tight and the available space for a muffler is limited for maintenance and operation purposes. To proficiently enhance the acoustical performance within a constrained space, the selection of an appropriate acoustical mechanism and optimizer becomes crucial. A one-chamber muffler hybridized with reverse-flow ducts which can visibly increase the acoustical performance is rarely addressed; therefore, the main purpose of this paper is to numerically analyze and maximize the acoustical performance of this muffler within a limited space. In this paper, the four-pole system matrix for evaluating the acoustic performance -sound transmission loss (STL) -is derived by using a decoupled numerical method. Moreover, a genetic algorithm (GA), a robust scheme used to search for the global optimum by imitating the genetic evolutionary process, has been used during the optimization process. Before dealing with a broadband noise, the STL's maximization with respect to a one-tone noise is introduced for a reliability check on the GA method. Moreover, the accuracy check of the mathematical model is performed. The optimal result in eliminating broadband noise reveals that the one-chamber muffler with reverse-flow perforated ducts is excellent for noise reduction. Consequently, the approach used for the optimal design of the noise elimination proposed in this study is easy and effective.


Chiu M.-C.,ChungChou Institute of Technology
Journal of Marine Science and Technology | Year: 2010

In order to overcome the noise impact emitted from a multi-noise plant, a sound barrier, a popular noise control strategy, has been used in the industrial field for a long time. However, the traditional method in the design of a sound barrier is time-consuming and expensive. To improve acoustical performance efficiently, interest in shape optimization of a four-segment sound barrier in conjunction with optimal equipment allocation around the plant's boundary is rising. In this paper, the novel technique of the genetic algorithm (GA) in conjunction with the theoretical sound propagation model and the method of minimized variation square are applied in the following numerical optimizations. Before a sound barrier is optimized, the sound propagation from one single noise is tested and compared with the experimental data for the purpose of accuracy within the mathematical model. Moreover, three kinds of noise-monitoring system (four-point, twelve-point, and twenty-eight-point) around the plant boundary have been adopted for verifying the deviation of the SPL between the simulated SPL and the specified target SPL. The results reveal that the both the sound barrier and the equipment can be properly shaped and allocated. Moreover, the more monitoring points used in the shape optimization of the sound barrier will result in a smaller area of the sound-barrier. Consequently, this paper may provide an efficient and rapid methodology in the noise minimization of a multi-equipment plant.


Kao F.J.,Ming Chuan University | Chiu Y.S.,Tunghai University | Tsou M.J.,ChungChou Institute of Technology | Chiang W.D.,Tunghai University
LWT - Food Science and Technology | Year: 2012

Carotenoids, lutein, zeaxanthin, and β-carotene, common in many vegetables, have been shown to be important in visual health-promoting. However, cooking practice has a great impact on these bioactive compounds. The objective of this work was to evaluate the effect of three common Chinese domestic cooking methods including boiling, stir-frying, and deep-frying on the composition of lutein, zeaxanthin, β-carotene and their trans/. cis (E/Z) isomers of vegetables. Among the 25 fresh vegetables commonly consumed in Taiwan, it was found that cilantro, Thai basil leaves, sweet potato leaves, and choy sum contained the 1st-4th highest amount of total carotenoids content (TCC), respectively. Boiling preserved the majority of carotenoids, whereas stir-frying and deep-frying significantly decreased TCC and (all- E)-forms of carotenoids. In addition, (all- E) - and (13. Z)-/(13'. Z)-carotenoids exhibited similar trends during boiling, since the boiling time required to reach maximum concentration for (all- E)-carotenoids was almost the same as that for (13. Z) - plus (13'. Z)-isomers. An overall increase of (9. Z)/(9'. Z)-carotenoid isomers was observed in all boiled vegetables, probably because of E/Z isomerization, which could partially result in the formation of more bioactive compounds such as (9. Z)- β-carotene. Boiling may be the preferred practice of domestic cooking methods to preserve carotenoids in vegetables. © 2011 Elsevier Ltd.

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