基于模型的DPF主动再生排气温度控制

颗粒物捕集器(DPF)主动再生发生时需要将柴油发动机排气温度提升到500℃以上并维持在较长一段时间内。为减少由于控制对象纯滞后特性、强扰动因素引起的不确定性,降低高排气温度带来的主动再生风险,结合基于模型的控制策略提出了一种优化的再生温度控制算法和控制器结构,并展开了仿真分析、参数优化等研究工作。设计的控制结构考虑实际工程应用需求,采用基于发动机排气温度和排气流量的增益补偿和前馈加反馈控制方案,可兼顾性能和成本因素,并具有较强的适应性和可操作性。仿真和台架试验、车辆道路试验结果均表明,主动再生过程中对实际排温控制的超调量小于3%,在发动机瞬态工况和车辆运行等强扰动工作工况下的稳态控制误差小于25℃。

DPF热再生过程温度控制与试验

柴油机颗粒物捕集器(DPF)热再生发生时,其内部温度受DPF碳载量、排气温度和排气流量等影响,在特殊运行工况下具有较强非受控特性.为避免非受控再生引起的DPF失效风险,确保安全和可靠再生,通过降怠速(DTI)再生方式探讨了一种确定DPF安全再生温度的试验方法,得到安全再生温度曲线.针对DPF热再生过程中温度控制的大滞后特性,研究了一种采用发动机排气温度和排气流量作为增益补偿的优化热再生温度控制结构,并进行了控制算法的仿真分析和整车道路试验验证.结果表明:再生过程中对实际排气温度控制的超调量小于3%,稳态控制误差小于20℃,为促进DPF的安全和高效率再生提供了参考.

Strategic deliberation on development of low-carbon energy system in China

In recent years, there have been considerable developments in energy provision with the growing improvements in energy supply security and support systems in China. However, China's energy system continues to retain a high-carbon feature where coal dominates energy production and consumption, which has led to the rapid growth of greenhouse gas emissions and associated serious environmental pollution. It has therefore become an important task for China to consider how to promote the low-carbon development of energy system. This paper summarized the basic trends and challenges for development of low-carbon energy system in China and studied the primary energy consumption and carbon emissions in different scenarios at 10-year intervals between 2010 and 2050. The analysis showed that controlling coal consumption will have an important influence on the control of total carbon emissions and of carbon emission peaking; promotion of non-fossil fuel energies will offer a growing contribution to a low-carbon transition in the medium and long term; the development of carbon capture, utilization, and storage will play a key role in realizing a deep decarbonization pathway, particularly after 2030; and the establishment of a low-carbon power system is crucial for the achievement of low-carbon energy transition. Finally, the strategic considerations and policy suggestions on the development of low-carbon energy systems in China are explored.

ENSO Variability Simulated by a Coupled General Circulation Model:ECHAM5/MPI-OM

The accurate simulation of the equatorial sea surlhce temperature （SST） variability is crucial for a proper representation or prediction of the El Nino-Southern Os- cillation （ENSO）. This paper describes the tropical variability simulated by the Max Planck Institute （MPI） forr meteorology coupled atmosphere-ocean general circulation model （CGCM）. A control simulation with pre-industrial greenhouse gases is analyzed, and the simulation of key oceanic features, such as SST, is compared with observa- tions. Results from the 400-yr control simulation show that the model＇s ENSO variability is quite realistic in terms of structure, strength, and period. Also, two related features （the annual cycle of SST and the-phase locking of ENSO events）, which are significant in determining the model＇s performance of realistic ENSO prediction, are further validated to be well reproduced by the MPI cli mate model, which is an atmospheric model ECHAM5 （which fuses the EC tbr European Center and HAM for Hamburg） coupled to an MPI ocean model （MPI-OM）, ECHAMS/MPI-OM.

Co-benefits of Local Air Pollutants and Greenhouse Gas Reduction Achieved by Hydropower Development in Xizang(Tibet) Autonomous Region, China

Hydropower development in Xizang(Tibet) Autonomous Region plays a vital role in co-control of local air pollutants and greenhouse gas(GHG) in China. According to emission factors of local air pollutants and GHG of coal-fired power industry in different hydropower service regions, we estimate the effect and synergy of local air pollutants and GHG reduction achieved by hydropower development in Tibet, examine the main factors constraining the effect and synergy, using correlation analysis and multiple regression analysis. The results show that: 1) During the period from 2006 to 2012, the effect of local air pollutants and GHG reduction achieved by hydropower development in Tibet decreased as a whole, while the synergy increased first and decreased afterwards. 2) The effect and synergy of local air pollutants and GHG reduction achieved by hydropower development in Tibet vary significantly across different hydropower service regions. The effect based on emission levels of Central China power grid(CCPG) and Northwest China power grid(NCPG) was more significant than that based on emission level of national power grid(NPG) from 2006 to 2012, and the synergy based on emission levels of CCPG and NCPG was also more significant than that based on emission level of NPG from 2010 to 2012. 3) The main factors constraining the effect and synergy based on emission levels of NCPG and CCPG included SO2 removal rate and NOx removal rate, the effect and synergy based on emission level of NPG was mainly influenced by net coal consumption rate. 4) Transferring hydropower from Tibet to NCPG and CCPG, and substituting local coal-fired power with hydropower can greatly help to co-control local air pollutants and GHG, transform the emission reduction pattern of the power industry and optimize energy structure.

Implications of the extremely hot summer of 2022 on urban ozone control in China

Frequent occurrences of extreme heat are causing severe ozone pollution over China.This study examined the driving factors of urban ozone pollution in China during the extremely hot summer of 2022 and the impact of emission control strategies using surface measurements and the GEOS-Chem model.The results show that ozone pollution was extremely severe in summer 2022,with a significant rebound by 12-15 ppbv in the North China Plain(NCP),Yangtze River Delta(YRD),and Sichuan basin(SCB),compared to 2021.Especially over the NCP,the MDA8(maximum daily 8-hourly average)ozone exceeded 160 ppbv,and the number of ozone exceedances was over 42 days.Based on an IPR(integrated process rate)analysis,the authors found that the net chemical production was the dominant factor contributing to the strong ozone increase in summer 2022.For example,in June over the NCP,the net chemical production resulted in an increase by 3.08 Gg d^(−1)(∼270%)in ozone mass change.Sensitivity simulations showed that both NO_(x)(nitrogen oxides)and VOC(volatile organic compound)reductions were important over the NCP,and NO_(x)reductions were more important than VOCs over southern China.To keep the ozone of 2022 at the same level as 2021,a joint reduction of NO_(x)and VOCs by at least 50%-60%would have been required.This study highlights the urgency to develop effective ozone management since extreme heat will become more frequent.