Nowadays harmful gas in vehicle exhaust has pollute d air heavily. To prevent the environment from polluting, the request of emissions control legislation becomes more stringent. New legislation prescribes not only th...Nowadays harmful gas in vehicle exhaust has pollute d air heavily. To prevent the environment from polluting, the request of emissions control legislation becomes more stringent. New legislation prescribes not only the emissions limitation of vehicles, but also testing instruments and methods. Test car must be operated on the chassis dynamometer and data must be collect ed and analyzed with prescriptive exhaust analysis system as well. The mass of harmful exhaust gas, containing the concentration and volume of emis sion, which is independent from the model of automobile and engine, can be used as a criterion to evaluate the pollution of an automobile. Constant Volume Sampl e System (CVS) is used to measure vehicle emissions, but it is too expensive to apply extensively. The Vehicle Mass Analysis System(Vmas), a new vehicle exhaust mass analysis system produced in USA late 1990s,is used to test and analyze veh icle exhaust. As a test instrument, it has the virtue of cheapness and easy mana geability. In this paper, Vmas is used to measure the emissions of a light truck CA1020F. A ccording to 15 running modes of Vehicle Exhaust Legislation, the test car is ope rated on the chassis dynamometer and data are collected and analyzed with Vmas. The test results show that it is viable to measure and evaluate automobile emiss ion with Vmas. Most of HC exhaust is produced when the car is decelerating. The major factor that influences the mass of HC emission is the sudden decrease of e ngine load causing incomplete combustion in decelerating mode. Test results indi cate CO and NOx are mainly produced in the process of increasing load. The forme r reason is incomplete combustion and the latter is high burning temperature cau sed by the increasing load. The methods of reducing automobile emission are also discussed in this paper.展开更多
The oxidization resistance of the Ni76Cr19A1Ti alloy was studied by a static oxidization experiment at 600-800℃. The results show that the oxidation behavior of the alloy can be explained by a kinetic equation： （△...The oxidization resistance of the Ni76Cr19A1Ti alloy was studied by a static oxidization experiment at 600-800℃. The results show that the oxidation behavior of the alloy can be explained by a kinetic equation： （△m/S）2 = Kpt ＋ C, where Kp is a kinetic constant of the nickel-base alloy. The higher the experimental temperature, the higher the value of Kp. It is discovered that the microstructure of the oxide scales is compact and the thickness of it is less than 10 μm The oxidization of the alloy is in the first grade. It is also found that the oxide scales are mainly composed of Cr2O3 and TiO2. Chrome and titanium react more easily with oxygen at temperatures under the operating mode.展开更多
Using a relaying system to provide spatial diversity and improve the system performance is a tendency in the wireless cooperative communications. Amplify-and-forward （AF） mode with a low complexity is easy to be imp...Using a relaying system to provide spatial diversity and improve the system performance is a tendency in the wireless cooperative communications. Amplify-and-forward （AF） mode with a low complexity is easy to be implemented. Under the consideration of cooperative communication systems, the scenario includes one information source, M relay stations and N destinations. This work proposes a relay selection algorithm in the Raleigh fading channel. Based on the exhaustive search method, easily to realize, the optimal selection scheme can be found with a highly complicated calculation. In order to reduce the computational complexity, an approximate optimal solution with a greedy algorithm applied for the relay station selection is proposed. With different situations of the communication systems, the performance evaluation obtained by both the proposed algorithm and the exhaustive search algorithm are given for comparison. It shows the proposed algorithm could provide a solution approach to the optimal one.展开更多
为研究废气再循环气体(exhaust gas recirculation,EGR)和进气方式对当量燃烧的天然气发动机燃烧特征的影响,通过发动机台架测试分别探究了EGR气体和EGR所含水汽以及5、6缸位置进气(右侧进气)与3、4缸位置进气(中间进气)对当量燃烧天然...为研究废气再循环气体(exhaust gas recirculation,EGR)和进气方式对当量燃烧的天然气发动机燃烧特征的影响,通过发动机台架测试分别探究了EGR气体和EGR所含水汽以及5、6缸位置进气(右侧进气)与3、4缸位置进气(中间进气)对当量燃烧天然气发动机各缸燃烧一致性的影响规律。试验结果表明:在右侧进气方式下,EGR气体的引入是影响当量天然气发动机各缸燃烧一致性的重要因素,特别是EGR气体中的水汽在各缸的分配。EGR气体除水汽后,各缸最大缸压偏差值由原来的9.5%降低为4.1%,当不引入EGR气体时,各缸最大缸压偏差值降低为2.3%。基于右侧进气方式在引入EGR气体后存在的问题,采用新设计的中间进气方式有效改善了各缸EGR气体的分配,从而显著提高了各缸燃烧一致性,各缸最大缸压偏差值由原右侧进气方式的9.5%降低为2.0%,有效解决了右侧进气在引入EGR时带来的各缸燃烧不一致性问题。展开更多
文摘Nowadays harmful gas in vehicle exhaust has pollute d air heavily. To prevent the environment from polluting, the request of emissions control legislation becomes more stringent. New legislation prescribes not only the emissions limitation of vehicles, but also testing instruments and methods. Test car must be operated on the chassis dynamometer and data must be collect ed and analyzed with prescriptive exhaust analysis system as well. The mass of harmful exhaust gas, containing the concentration and volume of emis sion, which is independent from the model of automobile and engine, can be used as a criterion to evaluate the pollution of an automobile. Constant Volume Sampl e System (CVS) is used to measure vehicle emissions, but it is too expensive to apply extensively. The Vehicle Mass Analysis System(Vmas), a new vehicle exhaust mass analysis system produced in USA late 1990s,is used to test and analyze veh icle exhaust. As a test instrument, it has the virtue of cheapness and easy mana geability. In this paper, Vmas is used to measure the emissions of a light truck CA1020F. A ccording to 15 running modes of Vehicle Exhaust Legislation, the test car is ope rated on the chassis dynamometer and data are collected and analyzed with Vmas. The test results show that it is viable to measure and evaluate automobile emiss ion with Vmas. Most of HC exhaust is produced when the car is decelerating. The major factor that influences the mass of HC emission is the sudden decrease of e ngine load causing incomplete combustion in decelerating mode. Test results indi cate CO and NOx are mainly produced in the process of increasing load. The forme r reason is incomplete combustion and the latter is high burning temperature cau sed by the increasing load. The methods of reducing automobile emission are also discussed in this paper.
文摘The oxidization resistance of the Ni76Cr19A1Ti alloy was studied by a static oxidization experiment at 600-800℃. The results show that the oxidation behavior of the alloy can be explained by a kinetic equation： （△m/S）2 = Kpt ＋ C, where Kp is a kinetic constant of the nickel-base alloy. The higher the experimental temperature, the higher the value of Kp. It is discovered that the microstructure of the oxide scales is compact and the thickness of it is less than 10 μm The oxidization of the alloy is in the first grade. It is also found that the oxide scales are mainly composed of Cr2O3 and TiO2. Chrome and titanium react more easily with oxygen at temperatures under the operating mode.
基金supported by National Science Council under Grant No.101-2221-E-029-020-MY3
文摘Using a relaying system to provide spatial diversity and improve the system performance is a tendency in the wireless cooperative communications. Amplify-and-forward （AF） mode with a low complexity is easy to be implemented. Under the consideration of cooperative communication systems, the scenario includes one information source, M relay stations and N destinations. This work proposes a relay selection algorithm in the Raleigh fading channel. Based on the exhaustive search method, easily to realize, the optimal selection scheme can be found with a highly complicated calculation. In order to reduce the computational complexity, an approximate optimal solution with a greedy algorithm applied for the relay station selection is proposed. With different situations of the communication systems, the performance evaluation obtained by both the proposed algorithm and the exhaustive search algorithm are given for comparison. It shows the proposed algorithm could provide a solution approach to the optimal one.
文摘为研究废气再循环气体(exhaust gas recirculation,EGR)和进气方式对当量燃烧的天然气发动机燃烧特征的影响,通过发动机台架测试分别探究了EGR气体和EGR所含水汽以及5、6缸位置进气(右侧进气)与3、4缸位置进气(中间进气)对当量燃烧天然气发动机各缸燃烧一致性的影响规律。试验结果表明:在右侧进气方式下,EGR气体的引入是影响当量天然气发动机各缸燃烧一致性的重要因素,特别是EGR气体中的水汽在各缸的分配。EGR气体除水汽后,各缸最大缸压偏差值由原来的9.5%降低为4.1%,当不引入EGR气体时,各缸最大缸压偏差值降低为2.3%。基于右侧进气方式在引入EGR气体后存在的问题,采用新设计的中间进气方式有效改善了各缸EGR气体的分配,从而显著提高了各缸燃烧一致性,各缸最大缸压偏差值由原右侧进气方式的9.5%降低为2.0%,有效解决了右侧进气在引入EGR时带来的各缸燃烧不一致性问题。
