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INTRODUCTION The use of dimethyl ether (DME) as an alterna-tive fuel appears to be a promising approach for si-multaneously minimizing NOx and soot emissionfrom conventional diesel engines. The lowself-ignition temperature of 508 K and the high oxy-gen content of 34.8 percent (mass fraction) are twomajor factors characterizing low soot and unburnedtotal hydrocarbon (THC) emissions. Since the firstintroduction of the concept by Sorenson and Mik-kelsen (19… 相似文献
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Different two-equation k-ε models were used to simulate the gas flow field generated by a new type of circulating fluidized bed reactor with venturi gas distributor. The numerical results were compared with the experimental data. It has been shown that the simulation results from the standard k-ε model have the best match with the experimental data. Based on this model, the gas flow field in the venturi diffuser and riser was analyzed by the concept of velocity nonuniformity and dead zone percentage. Both the nonuniformity of gas velocity and the dead zone percentage reach the maximum at the venturi outlet due to the effect of the vortex. At the same time, it provides a good platform for the further optimization of the inlet configuration of circulating fluidized bed reactor. 相似文献
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The flame structure of gasoline engine is complicated and has the characteristic of fractal geometry. A fractal combustion model was used to simulate the engine working cycle. Based on this model, the fractal dimension and laminar flame surface area of turbulent premixed flames were studied under different working conditions. The experimental system mainly includes an optical engine and a set of photography equipment used to shoot the images of turbulent flame of spark-ignition engine. The difference box-counting method was used to process 2D combustion images. In contrast to the experimental results, the computational results show that the fractal combustion model is an effective method of simulating the engine combustion process. The study provides a better understanding for flame structure and its propagation. 相似文献
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INTRODUCTIONDuetodwindlingfueloilreservesandthedesireforreducedpollutantemissions,naturalgas,whichisdominantlycomposedofmethane,hasbeennowwidelyusedasanalternativefuelininternalcombustionengines .Aconventionaldieselenginecanbeconvertedwithoutexcessiveincr… 相似文献
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The present work used a methane-air mixture chemical kinetics scheme consisting of 119 elementary reaction steps and 41 chemical
species to develop a simplified combustion model for prediction of the knock in dual fuel engines. Calculated values by the
model for natural gas operation showed good agreement with corresponding experimental values over a broad range of operating
conditions.
Project (No. 50106014) supported by the National Natural Science Foundation of China 相似文献
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The combustion performance of hydrogen fuel in a scramjet combustor has been a popular focus for scholars all over the world. In this study, the influence of the jet-to-crossflow pressure ratio on combustion performance in a scramjet combustor was investigated numerically, and the influence of a wall-mounted cavity was evaluated. The simulations were conducted using the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the renormalization group (RNG) k-ε turbulence model and the single-step chemical reaction mechanism. This numerical approach was validated by comparing predicted results with published experimental shadowgraphs and velocity and temperature measurements. When the pressure of the wall-injector increases, the performance of the combustor decreases. At the same inflow condition, this may lead to a scram-to-ram mode transition. The cavity adopted in this study would prevent pre-combustion shock waves from pushing out of the isolator and help to stabilize the flow field, but it would decrease the mixing and combustion efficiencies. 相似文献
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In order to investigate the effects of methyl ester moiety on polycyclic aromatic hydrocarbons (PAHs) and NO x formation in biodiesel combustion, the combined models were developed based on detailed methyl butanoate (MB) oxidation model and n-butane model. Also, PAHs detailed reaction mechanism and NO x formation mechanism were added to the detailed models to form the combined models. The combined models were used to compare the combustion of n-butane and MB in a shock tube simulation to understand the effects of methyl ester moiety. The results indicated that compared with n-butane, the methyl ester moiety in MB leads to different reaction pathways, more CO and CO 2 formation and less formation of PAHs precursors such as ethylene and acetylene. In addition, a better chemical insight into the effects of methyl ester moiety on NO x formation was given, which will help to understand the combustion process of biodiesel. 相似文献
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高浓度厌氧反应器流场的数值模拟 总被引：2，自引：1，他引：1
本文对高浓度搅拌桨厌氧反应器流场进行了数值模拟,计算采用多重参考系法和标准k-ε湍流方程。模拟结果表明,与牛顿流体形成的单循环流动相比,在反应器内的非牛顿流体形成了两个循环流动,这不利于厌氧反应器内的混合。在整个反应器内的湍流特性分布不均匀,局部湍动比较剧烈。在设计高浓度厌氧反应器时应考虑非牛顿流体特性的影响。 相似文献
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催化剂失活的Monte-Carlo模拟 总被引：1，自引：0，他引：1
从微观角度分析焦炭沉积与固体粒子凝聚间的相似性 ,提出一种催化剂积炭失活的微观模型 ,并用 Monte-Carlo方法模拟计算 .结果表明 ,焦炭的沉积形状与沉积机理有很大关系 ,得到了催化剂活性随时间及积炭量的变化关系 .并且 ,此模型虽只有两个参数 ,模拟过程亦十分简单 ,但适用范围广 ,可模拟催化剂的制备过程 ,指导催化剂生产 . 相似文献
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Thebubblecolumnreactor (BCR) ,withbatchfeedandcontinuousgasaerated ,hasobtainedwideapplica tionsinbiochemicalengineering ,chemicalengineeringandwastewatertreatment ,etc .OneimportantfeatureofBCRisthattheconversionandtheyieldofthereactioncanbehighlyincreasedundertheunsteady stateopera tion .Sincethemassandtheheattransferpropertiesinaprocessmainlydependontheflowbehavior ,itisstronglydesirabletoinvestigatetheunsteady stateflowstructurebeforethedesignandscale upofBCRwithhighreactiveconversionsa… 相似文献
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本文对侧伸式高浓度厌氧反应器流场进行了数值模拟,计算采用多重参考系法和标准k-ε湍流方程。模拟结果表明,由于高浓度流体具有牛顿流动特性,流体只在反应器底部形成了循环流动,在整个反应器内的湍流特性分布不均匀。在相同条件下,牛顿流体能够形成整体循环,湍流特性比较均匀。 相似文献
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The occurrence of storm surge disaster is often accompanied with floodplain, overflow, dike breach and other complex phenomena, while current studies on storm surge flooding are more concentrated on the 1D/2D numerical simulation of single disaster scenario(floodplain, overflow or dike breach), ignoring the composite effects of various phenomena. Therefore, considering the uncertainty in the disaster process of storm surge, scenario analysis was firstly proposed to identify the composite disaster scenario including multiple phenomena by analyzing key driving forces, building scenario matrix and deducing situation logic. Secondly, by combining the advantages of k-ω and k-ε models in the wall treatment, a shear stress transmission k-ω model coupled with VOF was proposed to simulate the 3D flood routing for storm surge disaster. Thirdly, risk degree was introduced to make the risk analysis of storm surge disaster. Finally, based on the scenario analysis, four scenarios with different storm surge intensity(100-year and 200-year frequency) were identified in Tianjin Binhai New Area. Then, 3D numerical simulation and risk map were made for the case. 相似文献
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Auto-ignition and heat release correlations for controlled auto-ignition(CAI)combustion were derived from extensive in-cylinder pressure data of a four-stroke gasoline engine operating in CAI combustion mode.Abundant experiments were carried out under a wide range of air/fuel ratio,speed and residual gas fraction to ensure that the combustion correlations can be used in the entire CAI engine operation range.Furthermore,a more accurate method to compute the residual gas fraction was proposed by calculating the working fluid temperature at the exhaust valve close timing in the experiments.The heat release correlation was described in two parts,one is for the first slower heat release process at low temperature,and the other is for the second faster heat release process at high temperature.Finally the heat release correlation was evaluated on the single cylinder gasoline engine running with CAI combustion by comparing the experimental data with the 1-D engine simulation results obtained with the aid of the GT-Power simulation program.The results show that the predicted loads and ignition timings match closely with the measurements. 相似文献
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应用Chemkin化学动力学软件包中的Senkin模块模拟了正庚烷在多孔介质发动机中的燃烧过程．通过修改Senkin程序,结合了Woschni传热模型和多孔介质换热模型,并在正庚烷详细氧化机理中加入氮氧化物的生成机理,将此程序纳入发动机燃烧的零维单区模型．对多种工况参数进行计算,讨论了运行参数对发动机性能的影响．当进气温度、压缩比增大,或过量空气系数降低时,多孔介质发动机着火时刻会明显提前．结果表明：多孔介质对混合气具有预热作用可强化发动机的点火燃烧,多孔介质的初始温度是决定压燃点火的决定性因素． 相似文献
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SMITH Eiamsa-ard PONGJET Promvonge 《浙江大学学报(A卷英文版)》2006,7(8):1406-1415
INTRODUCTION Vortex tube is a device for producing hot and cold air when compressed air flows tangentially into the vortex chamber through the inlet nozzles. This causes the vortex and swirl flow movement inside the vortex tube. The air in the middle region of the tube has lower velocity and lower temperature than the inlet air. So the air near the tube wall has higher ve-locity and higher temperature than the inlet air. The cold air in the core region of the tube flows out through the o… 相似文献
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Ｔｈｅａｃｃｕｒａｔｅｍｅａｓｕｒｅｍｅｎｔｏｆｔｈｅｇａｓ ｌｉｑｕｉｄｉｎｔｅｒｆａ ｃｉａｌａｒｅａｓｉｓｏｆｇｒｅａｔｉｍｐｏｒｔａｎｃｅｔｏｅｓｔｉｍａｔｅｒｅｌｉａｂｌｙｔｈｅｔｒａｙｅｆｆｉｃｉｅｎｃｉｅｓａｎｄｏｐｔｉｍｉｚｅｔｈｅｄｅｓｉｇｎｏｆｄｉｓｔｉｌｌａｔｉｏｎｃｏｌｕｍｎｓ .Ａｖａｒｉｅｔｙｏｆｅｘｐｅｒｉｍｅｎｔａｌａｐｐｒｏａｃｈｅｓｈａｖｅｂｅｅｎｕｓｅｄｔｏｍｅａｓｕｒｅｔｈｅｉｎｔｅｒｆａｃｉａｌａｒｅａｓａｎｄｂｕｂｂｌｅｓｉｚｅｄｉｓ ｔｒｉｂｕｔｉｏｎｓ… 相似文献
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数值模拟试验在岩土工程实验及工程案例教学中的应用 总被引：1，自引：0，他引：1
本文分析常规实验方法的特点及存在的问题,提出将数值模拟试验应用到教学试验中。数值模拟可以模拟常规实验,获得常规实验无法得到的实验数据。也可以模拟大型复杂的工程,这也是常规实验无法做到的。数值模拟试验应用到在岩土工程实验及工程案例教学中教学效果非常好。 相似文献
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A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability. 相似文献
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多热源环状管网的MATLAB仿真优化分析 总被引：1，自引：0，他引：1
在理论研究的基础上,结合仿真模型,利用MATLAB／SIMULINK对动态系统进行建模,分析了多热源环状供热管网的运行状态,通过对多热源环状管网水力工况模拟与仿真,可以比较实验模型数据与仿真模型数据,得出仿真完全符合实际规律的结论,从而确定了仿真的可信性。同时,进一步对无法利用实验进行研究的大型多热源环状管网进行仿真,分析大型环网的具体设计过程,从而指导环网的实际运行及调节。 相似文献