共查询到17条相似文献,搜索用时 171 毫秒
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基于双有机朗肯循环的 CNG 发动机余热回收系统参数优化及工质选择 总被引:1,自引:0,他引:1
为了充分利用 CNG 发动机的余热能量,根据 CNG 发动机的余热能分布特性设计了双有机朗肯循环系统,用来回收 CNG 发动机的排气能量、进气中冷能量以及冷却系统具有的能量。该双有机朗肯循环系统包括高温循环和低温循环,高温循环采用 R245fa 作为工质,用于回收 CNG 发动机排气能量;低温循环分别采用 R245fa , R1234ze 和 R1234yf 作为工质,用于回收进气中冷能量、高温循环冷凝过程中释放的能量以及发动机冷却系统的能量。在 CNG 发动机标定工况下,对双有机朗肯循环系统的参数敏感度进行了分析。结果表明:较高的高温循环蒸发压力和低温循环蒸发温度,较低的高温循环冷凝温度和低温循环冷凝温度可以提升双 ORC 系统的净输出功率和热效率;高、低温循环均选择 R245fa 的方案可以使系统具有较优的热力学性能。 相似文献
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有机朗肯循环作为回收发动机废热的有效手段,在商用车领域受到关注。R245fa是常见的有机朗肯循环工质,随着碳排放标准日趋严格,GWP高于150的制冷剂未来将面临淘汰。本文中提出一种新型低GWP制冷剂R1233zde替代R245应用于有机朗肯循环,物性与R245fa相近,GWP为7。并针对有机朗肯循环,建立了系统仿真模型,比较相同工况下两种工质的性能参数:蒸发温度,泵耗功和循环热效率。分析表明R1233zde泵耗功相比减少约15.05%~17.02%,R1233zde最大热效率比R245fa高7.03%。 相似文献
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工质的合理选择对有机朗肯循环回收柴油机排气余热产生重要影响。通过试验和理论计算,分析某6缸柴油机变工况下排气余热能的分布特性,提出有机工质初选条件,进而对满足条件的8种有机工质进行柴油机排气余热有机朗肯循环系统的热力学性能和经济性能对比分析。结果表明:在8种有机工质的蒸发压力范围内,R420A的系统热效率最大,为6.83%;在柴油机变工况下,R420A的系统总净输出功率、系统最大净输出功率和系统平均净输出功率均高于其他工质,分别为306.81 kW,9.769 kW和2.005 kW;采用R420A的系统初期投资成本较少,仅次于R417A和R437A,但其单位能量产出成本(LEC)最小。 相似文献
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利用设计的有机朗肯循环系统回收某重型车用柴油机的排气能量,通过台架试验,获得了变工况下柴油机排气余热能分布特性。分析了有机工质蒸发压力、过热度以及柴油机工况变化对有机朗肯循环系统性能的影响,以系统净输出功率和热效率为优化目标,确定了适用于有机朗肯循环系统的最佳蒸发压力。研究结果表明,当有机工质蒸发压力为1.8 MPa时,有机朗肯循环系统的净输出功率最大可以达到12.69kW,热效率可以达到11.19%;将有机工质加热至过热状态并不能明显提高有机朗肯循环系统的净输出功率。 相似文献
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汽车制造商在努力制造更节油的车辆时,会考虑采取一切可能的措施来提高内燃机动力系统的效率。其中,48V轻度混合动力技术即是节油措施之一。采用米勒技术的火花点火直喷发动机和从发动机废热中回收能量也是节油措施的一种。研究沃尔沃轿车基于乙醇的有机朗肯循环废热回收系统,围绕4缸2.0L的火花点燃发动机成功构建,运用48V轻度混合动力技术的同时考虑了车辆的安装需求。 相似文献
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对非共沸混合工质的柴油机ORC系统进了研究,提出了一种基于平衡和非平衡权重的热力学高维多目标优化(EMO)方法。研究表明,使用非共沸混合物,可提高换热器中工质和热源的匹配度,苯/甲苯(质量比:60%/40%)的输出功率(Wnet)比纯工质提高5.4%~19.2%。敏感性参数分析表明,随着蒸发温度的增大,Wnet先增大后减小,热效率(ηth)单调增加,总■损(Izon)单调减少。由于Wnet,ηth和Izon相互矛盾,不存在同时满足这三个指标的运行参数,为此开展高维EMO,利用RPD-NSGA-Ⅱ进行多目标优化并通过TOPSIS进行分析。当基于ηth,Wnet和Izon的平衡权重进行选择,最佳ηth,Wnet和Izon分别为24.07%,72.36 kW和44.66 kW,而柴油机废气能量回收率(η 相似文献
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《JSAE Review》2002,23(4):451-457
The authors have developed a capacitor hybrid vehicle equipped with a newly developed capacitor system and a miller cycle CNG engine for low floor urban buses. The CNG engine drives a generator at over 40% thermal efficiency. The newly developed capacitor system, since it has high energy and power density, is able to regenerate almost all the braking energy of a 14-ton bus at over 90% charging efficiency. The internal resistance of the capacitor system is minimized by the capacitor itself and a new capacitor connection. Furthermore, the voltage dispersion of the capacitor cells is minimized by the capacitor charging control system. The fuel economy was improved by 166% compared with the CNG low-floor bus and the vehicle efficiency reached over 45% in the M15 mode test. 相似文献
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Cheol Woong Park Chang Gi Kim Young Choi Sun Youp Lee Sung Won Lee Ui Hyung Yi Jang Hee Lee Tae Min Kim Duk Sang Kim 《International Journal of Automotive Technology》2017,18(6):1061-1066
Natural gas fuel, as an alternative energy source of transportation, has been used widely since it has an advantage of low emission levels. However, new technologies are required in order to meet the reinforced emission regulations. For this purpose, research into the development of hydrogen-compressed natural gas (HCNG) blend engine was carried out to evaluate its feasibility and emission characteristics. The Engine Research Department at the Korea Institute of Machinery and Materials carried out a large number of tests based on various parameter changes that could affect the performance and emission of HCNG engine in different operating conditions. An earlier stage of the research project focused on the lean combustion of a HCNG engine for heavy duty vehicles to meet the EURO-VI standards. An 11-L/6-cylinder CNG engine was used for the test. The effects of the excess air ratio change were assessed based on various content ratios of hydrogen in the natural gas fuel. In the later part of the HCNG research, a stoichiometric mixture operation was suggested to meet reinforced emission regulation without requiring a De-NOx system. Additionally, an exhaust gas recirculation (EGR) system was introduced for the purpose of improving thermal efficiency and durability. The optimal operating conditions were selected to achieve the best thermal efficiency to meet the required emission levels. In this paper, we demonstrate that a HCNG engine can achieve a significant decrease in NOx emissions, as compared to that of a CNG engine, while meeting the requirements of the EURO-VI standards during a transient mode cycle test. EGR can suppress the weakness of stoichiometric mixture combustion strategy, such as the deterioration of the durability and thermal efficiency, while the emission level can be lowered with the use of a three-way catalyst. The possibility of further reduction of emissions and CO2 with EGR was evaluated to access practical application of a HCNG engine in the field. From that evaluation, the HCNG engine with stoichiometric mixture operation for heavy duty vehicles was developed. The emission levels of HCNG engine were 50 % lower when compared to the EURO-VI standards with a greater than 10 % decrease in CO2 compared to that of a natural gas engine. 相似文献
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Jahedul Islam Chowdhury Bao Kha Nguyen David Thornhill 《International Journal of Automotive Technology》2017,18(4):589-601
The supercritical Organic Rankine Cycle (ORC) for the Waste Heat Recovery (WHR) from Internal Combustion (IC) engines has been a growing research area in recent years, driven by the aim to enhance the thermal efficiency of the ORC and engine. Simulation of a supercritical ORC-WHR system before a real-time application is important as high pressure in the system may lead to concerns about safety and availability of components. In the ORC-WHR system, the evaporator is the main contributor to thermal inertia of the system and is considered to be the critical component since the heat transfer of this device influences the efficiency of the system. Since the thermo-physical properties of the fluid at supercritical pressures are dependent on temperature, it is necessary to consider the variations in properties of the working fluid. The wellknown Finite Volume (FV) discretization method is generally used to take those property changes into account. However, a FV model of the evaporator in steady state condition cannot be used to predict the thermal inertia of the cycle when it is subjected to transient heat sources. In this paper, a dynamic FV model of the evaporator has been developed and integrated with other components in the ORC-WHR system. The stability and transient responses along with the performance of the ORC-WHR system for the transient heat source are investigated and are also included in this paper. 相似文献
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Y. Liu S. I. Hwang J. K. Yeom S. S. Chung 《International Journal of Automotive Technology》2014,15(3):353-359
Compressed natural gas (CNG) is regarded as one of the most promising alternative fuels. In the spark-ignition (SI) engine, direct injection (DI) technology can significantly increase the engine volumetric efficiency and reduce “pumping losses” in engines without a throttle valve. DI allows engine operation with the stratified charge which enables relatively higher combustion efficiency. In this study, a combustion chamber with a visualization system is designed. The spray development and combustion propagation process of spark-ignition direct injection (SIDI) CNG were digital recorded and analyzed. The ignition probability was also examined. The results of this study can contribute important data for the design and optimization of the SIDI CNG engine. 相似文献
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G. T. Chala A. R. A. Aziz F. Y. Hagos 《International Journal of Automotive Technology》2017,18(1):85-96
There is an increasing interest in supercharging spark ignition engines operating on CNG (compressed natural gas) mainly due to its superior knock resisting properties. However, there is a penalty in volumetric efficiency when directly injecting the gaseous fuel at early and partial injection timings. The present work reports the combined effects of a small boost pressure and injection timing on performance and combustion of CNG fueled DI (direct injection) engine. The experimental tests were carried out on a 4-stroke DI spark ignition engine with a compression ratio of 14. Early injection timing, when inlet valves are still open (at 300°BTDC), and partial injection timing, in which part of the injection occurs after the inlet valves are closed (at 180°BTDC), were varied at each operating speed with variation of the boost pressure from 2.5 to 10 kPa. A narrow angle injector (NAI) was used to increase the mixing rate at engine speeds between 2000 and 5000 rpm. Similar experiments were conducted on a naturally aspirated engine and the results were then compared with that of the boosting system to examine the combined effects of boost pressure and injection timing. It was observed that boost pressure above 7.5 kPa resulted in an improvement of performance and combustion of CNG DI engine at all operating speeds. This was manifested in the faster heat release rates and mass fraction burned that in turn improved combustion efficiency of the boosting system. An increased in cylinder pressure and temperature was also observed with boost pressure compared to naturally aspirated engine. Moreover, the combustion duration was reduced due to concentration of the heat release near to the top dead center as the result of the boost pressure. Supercharging was also found to reduce the penalty of volumetric efficiency at both the simulated port and partial injection timings. 相似文献