集料种类和粒径对微波加热效率的影响

根据不同集料种类和粒径对微波加热温升效率的影响,采用微波加热设备,研究加热0～5min时间内,O-5mm、5mm～10mm和10mm-15mm三种粒径的石灰岩集料和铁矿石集料的温度变化规律,计算温升效率。结果表明,相同时间内,铁矿石集料的温升效率明显高于石灰岩集料,最高可达133％;集料粒径明显影响其温升效率,温升效率按照粒径排列为0～5mm〉5mm—10mm〉10mm～15mm,最大差值达18％。     

Combustion and emission characteristics of BD20 reformed by ultrasonic energy for different injection delay and EGR rate in a diesel engine

The purpose of this study is to understand the operational characteristics of a diesel engine that uses BD20 reformed by ultrasonic energy irradiation. In particular we study the effects of tuning injection delay and EGR rate. BD containing about 10% oxygen has attracted attention due to soaring crude oil prices and environmental pollution. This oxygen decreases soot by promoting combustion, but it also increases NOx. To solve this problem, injection timing may be delayed or an EGR system may be applied. These adjustments normally lower engine power and increase exhaust emission but, in using fuel reformed by ultrasonic energy irradiation (which is changed physically and chemically to promote combustion), we may hope to circumvent this problem. To control the duration of the ultrasonic energy irradiation, the capacity of the chamber in an ultrasonic energy fuel supply system was tested at 550cc and 1100cc capacities. As for the results of the experiment, we could identify the optimum EGR rate by investigating the engine performance and the characteristics of exhaust emissions according to the injection timing and the EGR rate while ultrasonically irradiated BD20 was fed to a commercial diesel engine. With UBD20 (at an injection timing of BTDC 16°), the optimum EGR rate, giving satisfactory engine performance and exhaust emissions characteristics, was in the range of 15∼20%.     

Research on Heat Transfer Model of Asphalt Pavements Subjected to Microwave Heating Recycling

In　order　to　assess　temperature　field　in　microwave　heating　for　recycling　asphalt　pavements,a　2D　mathematic　heat　transfer　model　was　developed　based　on　Fourier　heat　transfer　theory　The　microwave　internal　heat?generation　was　researched　by　using　surface　field　of　pyramidal　horn　replacing　approximate　radiation　field　In　addition,the　boundary　conditions　were　built　and　normalization　processing　was　implemented　The　control　volume　based　finite　differential　method　(CV-BDM)　was　used　to　establish　the　implicit　discrete　scheme　of　the　conservation equations,and　the　numerical　value　simulation　was　employed　By　continuous　or　intermittent　 radiation　heating　technique,a　microwave　heating　experimental　system　at　2　145　GHz　was　carried　out　to　investigate　temperature　variation　characteristics　of　asphalt　pavements　along　with　heating　time　The　result　shows　that　(1)　the　increase　of　temperature　of　asphalt　mixture　during　microwave　heating　is　obviously　nonlinear,the　temperature　rises　slowly　in　the　initial　stage　of　the　heating　but　increases　rapidly　in　the　late　heating　period;　(2)　the　temperature　distribution　is　non-uniform　that　the　temperature　in　central　area　of　the　surface　is　higher　while　it　is　lower　on　edge;　(3)　the　uniformity　of　temperature　within　asphalt　mixtures　can　be　improved　by　using　intermittent　heating　technique,and　the　heating　time　must　be　reasonable　The　simulation　results　are　in　preferable　agreement　with　the　experiment