EGR冷却温度对重型柴油机性能及排放的影响

以一台配有废气再循环(exhaust gas recirculation,EGR)冷却系统和可变几何截面涡轮增压器的高压共轨重型柴油机作为研究对象,进行了EGR冷却温度对柴油机性能及排放影响的台架试验研究。结果表明:随着EGR冷却温度降低,柴油机燃油消耗率、烟度和NOx排放均持续降低。而EGR冷却温度每降低1℃,柴油机燃油消耗率、烟度和NOx排放在不同转速、负荷下降幅差异明显。燃油消耗率在中等转速、低负荷工况降幅最大,NOx排放和烟度在高转速、低负荷工况下降幅最大;在考虑到EGR冷却系统消耗的能量后,可以通过计算得到理论燃油消耗率。在兼顾燃油消耗率和排放性的原则下得到了各工况下EGR相对最优冷却温度,而所得到的相对最优EGR冷却温度正是各个试验工况下理论燃油消耗率最低的温度。     

废气再循环在增压中冷柴油机上的试验研究

为了降低车用柴油机的NOx排放,分析了不同工况下EGR率对柴油机性能的影响。通过试验了解到,采用EGR可以有效地降低NOx排放,大负荷比小负荷效果显著。并对控制最佳EGR率的电控脉谱系统提出了初步的探讨。     

YC4112ZLQ柴油机电控EGR系统的研究

为了降低柴油机的氮氧化物排放，对YC4112ZLQ增压中冷柴油机进行了电控废气再循环(EGR)技术的研究。试验研究了不同EGR率对发动机各个工况下性能和排放的影响规律，据此针对欧洲Ⅱ号标准优选出了各个工况下的最佳EGR率，并对最佳EGR率下的控制参数进行了电控标定。利用标定结果，设计了一套电子控制系统，用于该柴油机的实际运行。试验结果表明，与原机相比，加入EGR以后，在微粒排放略有增加的情况下，NOx排放下降12．9％，使13工况排放全面达到欧洲Ⅱ号标准的要求。     

增压直喷柴油机EGR系统开发与试验研究

以增压直喷柴油机为研究对象,设计了一套EGR控制系统以降低NOx排放。试验研究了不同EGR率对柴油机性能及排放的影响规律,针对柴油机不同工况的特点,确定了各工况所用的EGR率,并设计了EGR率电控系统。台架试验表明,在保持其它排放物基本不变的情况下,借助EGR系统该柴油机的NOx排放下降了26．4％。     

增压直喷式柴油机EGR率测试及优化研究

针对增压直喷式柴油机,开展了应用废气再循环技术降低NOx排放的研究.研究了不同EGR率对发动机13工况下性能和排放的影响规律,并优选了发动机13工况下EGR率.利用设计的EGR电控系统,实现了发动机EGR率的自动控制,并通过试验对EGR系统进行了验证.     

具有自动控制功能的柴油机EGR系统的研制

研究了与柴油机匹配的电控废气再循环系统,进行了电控EGR系统中的部分硬件、硬件电路设计和软件的编写,EGR的实现方式和EGR系统与柴油机匹配的问题.试验用柴油机在使用了自行设计的电控EGR系统后,实现了整个转速、负荷范围内EGR率的自动控制.13工况排放测试结果表明:采用EGR系统,NOx排放降低26.7 %、微粒总量和HC排放几乎不变、CO排放上升15.5 %.     

利用EGR技术降低涡轮增压柴油机排气污染的研究

以一台增压柴油机为研究对象设计了一套带有文曲利管的并联EGR系统,该系统可以在较小地损失充气效率的情况下,将排气较为容易的引入到进气管,并与之混合,使混合气的静压力在扩压管中得到最大程度的恢复,通过试验找出了达到Tier3排放法规要求的各工况下所需的EGR率,以及各工况下EGR率与NOx、烟度、油耗的关系,得到了各工况下兼顾满足NOx、油耗、颗粒排放等指标的EGR率范围,并研究了冷却EGR对NOx排放的影响,EGR经过冷却后降低NOx的效果更加明显,这些研究成果具有重要的工程应用价值.     

冷EGR技术对柴油机性能及排放的影响

通过在不同转速和负荷工况下进行的冷EGR试验,研究了冷EGR技术对降低柴油机NOx排放的有效性,同时对比分析了EGR开启和关闭时对柴油机性能和排放的影响.试验研究表明:冷EGR技术除了可以有效降低柴油机的NOx排放以外,还将对柴油机的进气流量、燃油消耗率、烟度、排温以及HC,CO等排放物产生影响,且这种影响随着EGR率和工况的不同而变化.     

文曲利管排气再循环系统在涡轮增压柴油机上的应用研究

以一台 D6 114涡轮增压柴油机为研究对象 ,采用了一套带文曲利管的排气再循环系统进行了试验研究。试验结果表明 ,该系统在高工况下能克服平均排气压力低于平均进气压力的困难 ,方便地实现排气再循环。研究了在不同工况下柴油机的 NOx 排放、烟度和比油耗随 EGR率的变化规律以及 EGR的冷却效果对 NOx 排放的影响     

EGR率对M15甲醇柴油燃烧与排放的影响

在不同工况下研究了不同EGR率对增压中冷柴油机燃用M15甲醇柴油混合燃料的燃烧和污染物排放的影响。实验结果表明：随着EGR的增加,最高缸压、最大放热率和缸内温度逐渐降低,所对应的曲轴转角后移,NOx排放大幅度降低,烟度、HC、CO等排放有不同程度的恶化。选择合适的EGR率可以消除柴油机NOx排放和烟度之间的Trade-off关系。     

Improvements in controlled-environment facilities for testing domestic air-to-water heat pumps

A control system is described, based on a microcomputer, which maintains constant temperature and relative humidity in a controlled-environment laboratory used for research on air-to-water heat pumps. The performance of the control system is measured under both steady-state and changing conditions, and optimum values of the control constants are deduced. The temperature can be maintained at the set value to within 0–1°C, and the relative humidity to within 1 per cent, under steady-state conditions. The effects of transients, such as the starting or stopping of the heat pump under test, or the deliberate changing of the controlled conditions, are studied in detail. In addition, a system is described for controlling the temperature of the condenser cooling water, which can be held to within 0–1°C of the set value.     

Optimization of water-cooled chiller system with load-based speed control

This study investigates the energy performance of chiller and cooling tower systems integrated with variable condenser water flow and optimal speed control for tower fans and condenser water pumps. Thermodynamic-behaviour chiller and cooling tower models were developed to assess how different control methods of cooling towers and condenser water pumps influence the trade-off between the chiller power, pump power, fan power and water consumption under various operating conditions. Load-based speed control is introduced for the tower fans and condenser water pumps to achieve optimum system performance. With regard to an example chiller system serving an office building, the optimal control coupled with variable condenser water flow could reduce the annual system electricity use by 5.3% and operating cost by 4.9% relative to the equivalent system using constant speed fans and pumps with a fixed set point for cooling water temperature control.     

Experimental examination of large capacity liFePO4 battery pack at high temperature and rapid discharge using novel liquid cooling strategy

To overcome the significant amounts of heat generated by large‐capacity battery modules under high‐temperature and rapid‐discharge conditions, a new liquid cooling strategy based on thermal silica plates was designed and developed. The superior thermal conductivity of the thermal silica plate combined with the excellent cooling effect of water led to a feasible and effective composite liquid cooling system during long cycle testing. The experimental results showed that the addition of thermal silica plates can greatly improve the cooling capacity that can allow the maximum temperature difference to be controlled at 6.1°C and reduce the maximum temperature of the battery module by 11.3°C, but still outside the optimum operating temperature range. The water flow significantly enhanced the cooling performance/stability, and slight temperature fluctuations were observed during cycling. The cooling performance obviously improved as the flow rate rose. When the velocity reached a critical value, further increase in water flow rate induced a slight influence on the cooling capacity due to the limitation of the materials. The maximum temperature (T_max ) could be reduced to 48.7°C, and temperature difference (?T ) could be maintained within 5°C when the water flow velocity increased to 4 mL/s, which was determined as the best value. The energy consumed by the water pump is only 1.37% of the total energy of the battery module. Overall, these findings should provide novel strategies for the design and optimization of battery thermal management system.     

变容量家庭能源中心单独制热水模式的实验研究

提出了可全年供应空调和热水需要的变容量家庭能源中心系统,并提出单独制热水模式下的性能系数计算方法。通过对该模式瞬时动态特性的研究,指出变容量压缩机可以有效地保证机组的安全可靠运行。实验研究了单独制热水模式在不同环境温度、不同压缩机负荷条件下的性能。结果表明,在同一压缩机负荷条件下,热水性能系数均随环境温度的升高而升高,与传统热泵热水器的变化趋势相同。而压缩机负荷变化对机组热水性能系数的影响在不同的环境温度下呈现不同的规律,因此,可根据不同的环境温度优化控制压缩机负荷,以提高制热水效率,节约能源。     

竖管式蒸馏太阳能苦咸水淡化装置性能研究

针对偏远缺水地区提出一种新型竖管式蒸馏太阳能苦咸水淡化装置,利用嵌套圆管之间小空间形成苦咸水受热蒸发冷凝腔从而生成淡水,该装置具有结构紧凑、节省空间、承压性能好等特点。介绍了竖管式蒸馏太阳能苦咸水淡化装置的结构原理,对装置在不同加热功率下淡水产量及蒸发冷凝温度进行了试验研究,得到了不同运行工况下装置的性能系数,探索了提高装置淡水产量的方法,分别研究了在负压运行工况和套筒外壁面水冷负压运行工况下的装置淡水产量和温度变化。结果表明:装置在输入功率为200 W时,性能系数可以达到0.80;工作压力为75kPa,加热温度为80.00℃时,装置淡水产量为0.259kg/h,比相同加热温度下常压时装置淡水产量提高23.90%;当装置套筒外壁面进行水冷强化,工作压力为75kPa,加热温度为70.00℃时,装置淡水产量为0.690kg/h,是非水冷相同运行工况下装置淡水产量的3.62倍。     

EGR对小型汽油机排放和性能影响的实验研究

实验研究了一款小型汽油机在不同负荷下,使用不同EGR率时,其动力性、经济性和NOx排放特性的变化规律,确定了各个工况下发动机最佳EGR率,得出在较大负荷下,EGR阀开度为30°时可以使动力性、经济性在变化不大的情况下,NO降低60%以上。     

冷水相变能热泵系统的性能系数与经济性分析

冷水相变能热泵系统是一种清洁能源供热供冷系统,性能系数和经济性是冷水相变能热泵系统的主要问题。根据冷水相变能热泵系统的运行原理,采用控制变量法实验分析了冰层厚度、冷水流量以及蒸发冷凝温度对系统能效比的影响,提出了一种冷水相变能热泵系统的运行调控方案并计算其经济性。研究表明：结冰厚度为8 mm时,系统有效能效比最大;系统制热量为744 kW时,相变机结冰期冷水流量应控制在70 t/h,排冰期冷水流量应控制在80 t/h;根据不同时间段的冷热负荷进行系统运行调控,与传统运行方式相比,冬季运行成本降低了4.72%,夏季运行成本降低了29.96%,系统能效比提高了5.6%;系统投资回报率为15.27%,投资回收期为7.67年,具有良好的经济性与节能性。     

瞬态工况下 EGR 率测量方法的研究

稳态工况EGR率的测量通常采用测量CO2浓度的方法,在瞬态工况下CO2分析仪存在响应滞后的问题,提出利用热力学能量守恒原理,通过测量EGR混合前后的气体温度,计算出基于质量比率的EGR率,并对测量精度进行了分析,与目前国内外通用的测量CO2的浓度来计算EGR的方法进行了比较。温度法测量的EGR率基本上可以满足瞬态下EGR率的测量要求。     

电厂水环式真空泵冷却系统的问题及其对机组出力的影响

通过对电厂中常用的水环式真空泵冷却系统运行实际情况的分析研究，指出其运行中存在但常被忽视的问题：由于真空泵冷却水温升高而导致的抽气能力严重降低，使机组背压升高，出力下降。文章提出凝汽器的压力实际受到两个瓶颈的限制：一是循环水的温度，二是真空泵的极限工作压力，而这一点常没有被足够的注意，导致凝汽器压力明显升高。由于凝汽器压力对机组运行的出力和经济性影响很大，文章提出了对真空泵冷却系统改进的建议，即尽量降低真空泵冷却水入口温度，在平时运行时应密切注意真空泵热交换器的运行状况。图3     

Performance of solar assisted heatpump systems in residential applications

In this experimental study, several solar-assisted heating and cooling configurations have beenconsidered for a basic system comprised of a two-speed heat pump, photovoltaic (PV) arrays, solar thermal collectors, and thermal storage. The objective of the study was to determine the performance of the PV arrays at decreased insolation, the effects of air preheat by solar thermal energy on heat pump operation, and cooling system performance under two different configurations. During the entire operation, the PV arrays converted 4.7 per cent (9.5 MWh) of the incident solar insolation to d.c. power, of which 54.6 per cent was used by the residence. This contributed 23.4 per cent of the total house electrical demand. The remaining 45.4 per cent of the output was fed to the utility, indicating the arrays and the heat pump were not properly sized with each other. Based on results from the winter heating operation, it is shown that for the particular heating system consdered, the best performance is attained when the solar heating is used alone. By using the heat pump as a booster, the remaining available solar energy left in the storage tank can be used with good seasonal performance factor. Summer cooling operation consisted of two sequential cooling configurations. In the first cooling test, the heat pump was operated to either the house or storage when the PV array generation level was greater than the energy demand of the heat pump and associated equipment. When the array output level was less than the cooling system demand, the operating strategy was that of an off-peak cooling operation to chill the water storage. Utilization of chilled water storage was not realized in the first cooling test because of the inherent inefficient design of the Tri-X coil. The capacity at low-speed heat pump operation was too small to effect significant cooling of the water loop; whereas high-speed heat pump operation in attempting to chill water (fan operation absent) caused frosting of the coil. The heat pump was utilized only to maintain chilled water storage in the second cooling test, without heat transfer through the Tri-X coil. Cooling system performance obtained in cooling test 2 using the Ametex exchanger was considerably improved over the test 2 performance with the Tri-X coil.