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Broadband Membrane-Type Acoustic Metamaterial Structures with Polymorphic Anti-Resonance Modes

Xi’an Jiaotong University-Guojian Zhou, Jiu Hui Wu
Gissing Tech. Co., Ltd.-Qianqian Zhang, Xiujie Tian, Yuying Jiang, Wei Huang, Keda Zhu
Published 2019-06-05 by SAE International in United States
The researches indicate that rational design of membrane-type acoustic metamaterial (MAM) can make it have a high sound transmission loss (STL) at the anti-resonant frequency. Based on the principle of local resonance of acoustic metamaterials, this paper studied the coupling interactions between sound field and vibration modes, and designed four lightweight MAM structural units with different distributed harmonic oscillators, and then the anti-resonant behaviors of different units within the low frequency were gradually analyzed. The regulation mechanism of continuous polymorphic anti-resonance modes on broadening STL bandwidth was further revealed, and the STL characteristics have been verified within the low-frequency range by numerical simulation and experiments. The results show that the design of a single cross-shaped resonator can increase the diversity of anti-resonance modes and eliminate the node-circular-type resonance mode, then ensure the wider STL bandwidth. Furthermore, four metal platelets set symmetrically between the swing arms based on the unit above increase the local anti-resonance modes of the new unit, which greatly expand the STL bandwidth by shifting its upper limit to the right. In addition,…
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Application Study on a Flexible Rebound-Type Acoustic Metamaterial at Low Frequency

Xi’an Jiaotong University-Jiu Hui Wu
Gissing Tech. Co., Ltd.-Guojian Zhou, Xiujie Tian, Keda Zhu, Wei Huang, Richard E. Wentzel, Melvyn J. Care, Kaixuan Mao
Published 2017-06-05 by SAE International in United States
A flexible rebound-type acoustic metamaterial with high sound transmission loss (STL) at low frequency is proposed, which is composed of a flexible, light-weight membrane material and a sheet material - Ethylene Vinyl Acetate Copolymer (EVA) with uneven distributed circular holes. STL was analyzed by using both computer aided engineering (CAE) calculations and experimental verifications, which depict good results in the consistency between each other. An obvious sound insulation peak exists in the low frequency band, and the STL peak mechanism is the rebound-effect of the membrane surface, which is proved through finite element analysis (FEA) under single frequency excitation. Then the variation of the STL peak is studied by changing the structure parameters and material parameters of the metamaterial, providing a method to design the metamaterial with high sound insulation in a specified frequency range. A group of combined metamaterial is proposed which consist of the metamaterial and felt or PU material, which can avoid some of the resonance frequency points and fill the STL valleys of the pure metamaterial structure. It could achieve light-weight…
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Study on the Laminar Characteristics of Ethanol, n-Butanol and n-Pentanol Flames

Xi’an Jiaotong University-Qianqian Li, Yu Cheng, Wu Jin, Zhaoyang Chen, Zuohua Huang
Published 2015-09-01 by SAE International in United States
Due to serious energy crisis and pollution problem, interest in research of the alternative fuels is increasing over the world. Alcohol fuels are always considered to be promising alternative fuels. Lower alcohols owning high octane number is good octane enhancer for SI (Spark ignition) engine, however is difficult to be used in CI (Compression Ignition) engines. Higher alcohols like pentanol with higher energy content, poor water solubility and higher cetane number are good choice for the CI engines. In this study, laminar flame behaviors of ethanol-air, n-butanol-air and n-pentanol-air mixtures at 393 K and 0.1 MPa are compared and analyzed with the spherical propagating flames. Comparison of the laminar flame speeds measured in the previous studies (Li et al.) show that laminar flame speed of ethanol is the fastest with slower flame speed of n-butanol and n-pentanol at lean mixture. At rich mixture, three alcohols present very close values. The effective Lewis number of n-pentanol is the biggest, and then n-butanol and ethanol. The difference among the three fuels is decreasing with the increase of…
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Combustion and Emissions Performance of a Spark Ignition Engine Fueled with Water Containing Acetone-Butanol-Ethanol and Gasoline Blends

Xi’an Jiaotong University-Jiaxiang Zhang
Central South University-Yuqiang Li, Shengming Liao
Published 2015-04-14 by SAE International in United States
Butanol has proved to be a very promising alternative fuel in recent years. The production of bio-butanol, typically done using the acetone-butanol-ethanol (ABE) fermentation process is expensive and consumes a lot of energy. Hence it is of interest to study the intermediate fermentation product, i.e. water-containing ABE as a potential fuel. The combustion and emissions performance of ABE29.5W0.5 (29.5 vol.% ABE, 0.5 vol.% water and gasoline blend), ABE30 (30 vol.% ABE and gasoline blend) and ABE0 (pure gasoline) were investigated in this study. The results showed that ABE29.5W0.5 enhanced engine torque by 9.6%-12.7% and brake thermal efficiency (BTE) by 5.2%-11.6% compared to pure gasoline, respectively. ABE29.5W0.5 also showed similar brake specific fuel consumption (BSFC) relative to pure gasoline. According to the mass fraction burned (MFB) calculation, ABE29.5W0.5 presented a longer ignition delay and combustion duration, which meant that ABE29.5W0.5 had a lower combustion rate resulted by the reduced combustion temperature due to water addition. Additionally, ABE29.5W0.5 produced a lower nitrogen oxides (NOx) and carbon monoxide (CO), but also increased unburned hydrocarbon (UHC), but showed decreased…
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Effects of Di-(2-ethoxyethyl) Carbonate as an Oxygenated Fuel on Diesel Fuel Properties and Engine Performances

Xi’an Jiaotong University-Shenghua Liu
Xi'an Research Institute of High Tech.-Hejun Guo
Published 2014-04-01 by SAE International in United States
A new oxygenate of di-(2-ethoxyethyl) carbonate was synthesized, and its structure was identified by FT-IR, 1H NMR and GC-MS analyses. The effects of addition of the substance to diesel fuel on fuel properties and engine performance were studied. Results showed that this oxygenate is miscible with individual hydrocarbons in any proportion under normal temperature of 25°C. When di-(2-ethoxyethyl) carbonate is introduced to a diesel fuel, kinematic viscosity does not change notably, smoke point increases linearly. Flash point and solidifying point decline remarkably even at low content level of 5%(v) of the oxygenate, whereas they do not decrease further notably with its content increasing. The compound does not exert corrosion effect on cupric metal. When a diesel engine was fueled with the diesel fuel containing 25%(v) of the oxygenate. CO emissions were decreased by more than 50%, smoke was reduced by up to 83.8%, NOx showed no noticeable change, and unburned HC emissions were reduced by 30% to 60%. At engine speeds of 1800rpm and 2300rpm, fuel consumption respectively increased by 3.3%-7.7% and 2.4%-8.1% at content…
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