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A computer model is developed for studying the first- and second-law (availability) balances of a turbocharged diesel engine, operating under transient load conditions. Special attention is paid to the direct comparison between the results from the two laws, for various operating parameters of the engine. The model simulates the transient operation on a degree crank angle basis, using a detailed analysis of mechanical friction, a separate consideration for the processes of each cylinder during a cycle (“multi-cylinder” model) and a mathematical model of the fuel pump. Experimental data taken from a marine duty, turbocharged diesel engine, located at the authors’ laboratory, are used for the evaluation of the model's predictive capabilities. The first-law (e.g., engine speed, fuel pump rack position, engine load, etc.) and second-law (e.g., irreversibilities, heat loss and exhaust gases) terms for the diesel engine cylinder are both computed and depicted in comparison, using detailed diagrams, for various engine operating parameters. It is revealed that, at least for the specific engine type and operation, a thermodynamic, dynamic or design parameter can have a conflicting impact on the engine transient response as regards energy and availability properties, implying that both a first- and second-law optimization is needed for best performance evaluation. 相似文献
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针对强噪声干扰下柴油机失火故障难以诊断的问题,提出一种基于变分模态分解(variational mode decomposition,VMD)与交叉小波变换(cross wavelet transform,XWT)的柴油机失火故障诊断方法。该方法首先通过VMD将缸盖振动信号进行分解、自适应消噪及信号重构,再利用XWT对任意两个连续工作循环信号进行时频相关分析,进一步消除振动信号中的干扰噪声以提取柴油机燃烧特征,最后通过计算时频空间各缸能量占比进行柴油机失火故障诊断。通过对仿真信号分析及柴油机失火故障诊断,结果表明:该方法可以消除强噪声干扰,提取柴油机燃烧周期瞬态振动冲击特征,有效地识别柴油机失火故障。 相似文献
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An experimental study was carried out to investigate the effect of using Exhaust Gas Recirculation (EGR) on various exergy terms of an IDI diesel engine cylinder. In this paper also the effectiveness of total in-cylinder irreversibility on Brake Specific Fuel Consumption (BSFC) in a diesel engine is investigated. To serve this aim an exergy analysis is conducted on the engine cylinder which provides all the availability terms by which the evaluation of in-cylinder irreversibilities is possible. The availability terms including heat transfer, inlet and exhaust gases and work output are presented during the engine operation at different load and speeds. To clarify the effect of using EGR in each case, EGR is introduced to the cylinder at various ratios during the tests. Finally, the dependence of total in-cylinder irreversibility and engine BSFC at particular engine operating conditions is introduced and the variations are compared. The results show that using EGR mostly increases the total in-cylinder irreversibility mainly due to extension of the flame region which reduces maximum combustion temperature. Also, the results revealed that the variations of the total in-cylinder irreversibility and engine BSFC follow the same trend especially at high load conditions. 相似文献
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基于缸盖振动信号的柴油机多工况性能预测 总被引:1,自引:0,他引:1
采用小波分析法和时间序列法从柴油机缸盖表面振动信号识别气缸压力,通过对示功图 进行分析计算得到了相应的放热规律;采用双韦柏函数对放热规律进行拟合,建立了双韦柏参数的多工况变化关系式,实现了放热规律的多工况计算,并与工作过程数值计算相结合,从柴油机缸盖振动信号预测多工况性能。 相似文献
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直喷式柴油机起动过程燃烧分析 总被引:9,自引:0,他引:9
为了快速、定性分析柴油机起动过程中的燃烧状态,在直喷式柴油机上进行冷机与热机起动过程实验,提出用瞬时转速和示功图对柴油机起动进行燃烧分析的方法.实验结果表明,冷机起动过程中有失火现象,用瞬时转速可以判断着火首循环和失火循环.根据示功图形状及燃烧状态,定义了4种燃烧状态以及相对应的4种典型示功图形式,将起动过程划分为4个阶段.热机起动初始期和过渡期很短,而冷机起动有明显的4个阶段.不完全燃烧或失火是柴油机起动过程、燃烧过程控制优化的重点,多出现在起动初始期和过渡期. 相似文献
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建立了某四缸龙门式柴油机气缸体的有限元分析模型,从某四缸龙门式柴油机气缸体的结构动态特性和振动响应进行分析,采用模态试验对有限元模型进行修正,通过有限元、多体动力学手段研究柴油机在额定工况下,以气缸燃气压力、活塞侧压力和主轴承作用力为主要因素,确定了柴油机所受的激励力,利用模态叠加法对柴油机进行了动态响应分析计算,得出了额定载荷下的整机振动烈度,并与整机振动烈度的实测值进行比较,验证了模型的正确性。 相似文献
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建立了某四缸龙门式柴油机气缸体的有限元分析模型,从某四缸龙门式柴油机气缸体的结构动态特性和振动响应进行分析,采用模态试验对有限元模型进行修正,通过有限元、多体动力学手段研究柴油机在额定工况下,以气缸燃气压力、活塞侧压力和主轴承作用力为主要因素,确定了柴油机所受的激励力,利用模态叠加法对柴油机进行了动态响应分析计算,得出了额定载荷下的整机振动烈度,并与整机振动烈度的实测值进行比较,验证了模型的正确性。 相似文献
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柴油机缸套间隙超磨耗标准故障监测诊断研究 总被引:2,自引:0,他引:2
介绍了多缸柴油机(6135G)的超磨耗标准的活塞—缸套间隙进行状态监测及故障诊断的研究。针对多缸柴油机的超磨耗标准缸套间隙进行分析,在此基础上选择与活塞—缸套工作状态有关的监测诊断参数,探讨气缸压力、机体振动、瞬时转速与活塞—缸套工作状态的关系并进行试验,利用各种分析方法,从中提取诊断特征作为状态监测及故障诊断信息。 相似文献
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An experimental analysis is conducted investigating the differences between the variations of overall and local instantaneous heat transfer coefficients, during the engine cycle, in the combustion chamber walls of a direct injection (DI), air-cooled diesel engine located at the authors’ laboratory. For this purpose, a novel experimental installation is developed, which separates the engine transient temperature signals into two parts, namely the long- and the short-term response ones, processed in two independent data acquisition systems. Moreover, a new pre-amplification unit for fast response thermocouples, appropriate heat flux sensors and an object-oriented control code for fast data acquisition have been designed and applied. Experimentally obtained cylinder pressure diagrams are used as a basis for the calculation of the overall heat transfer coefficients, whereas one-dimensional heat conduction theory with Fourier analysis techniques, combined with an iterative procedure between calculated and measured temperature data, are implemented in order to calculate the instantaneous local heat transfer coefficients in the engine cylinder. Analysis of the experimental results reveals interesting aspects of transient engine heat transfer. Significant differences are disclosed between the overall and local heat transfer coefficient variations, with the importance of the latter one on engine design being emphasized. The local heat transfer coefficient on the cylinder head is quantified based on the experimental data. The effect of engine speed and load as well as of the air swirling motion on the heat transfer variations are presented. From the analysis results it is concluded that the instantaneous heat transfer variation is non-uniform, unlike its values calculated from standard correlations that assume spatial uniformity, noting that such information, especially for air-cooled diesel engines, seems to be very scarce in the open literature. 相似文献
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以一款商用车用电控柴油机为研究对象,针对恒转速增转矩工况的燃烧放热特性开展了台架测试和燃烧分析,重点分析了不同过渡时间和不同恒定转速下恒转速增转矩工况的燃烧特性。结果发现,发动机转矩加载过快时,易引起供油量突增,燃料的能量转换效率下降。而当发动机用较长时间平缓加载的过程中,可能因混合气浓度高导致燃料的能量转换效率下降。此外,恒转速增转矩过程中,随着转速的升高,压力急升点提前,燃烧速燃期延长,后燃期缩短,热功转换效率提高。总之,增转矩瞬态过程各个循环的燃烧效率与混合气浓度和各循环的燃烧放热规律密切相关。 相似文献
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采用ANSYS有限元分析法,对S195柴油机机体进行了符合实际情况的Pro/E三维建模,研究了机体的变形和应力状态,探讨了目前S195柴油机机体应力有限元计算中力学模型的合理性,并对机体进行了模态分析,为柴油机轻量化、改进设计提供了有价值的理论依据。 相似文献
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This work presents an experimental analysis which is carried out to study the instantaneous heat fluxes, during the engine cycle, in the cylinder head and exhaust manifold of a direct injection, air‐cooled, four‐stroke diesel engine. For temperature measurements, a new pre‐amplification unit for fast response thermocouples, appropriate heat flux sensors and an innovative, object‐oriented, control code for fast data acquisition have been designed and developed at the authors' laboratory. The experimental installation separates the engine transient temperature signals into two parts; namely the ‘long’‐ and the ‘short’‐term response ones; followed by their discrete processing in two independent data acquisition systems. One‐dimensional heat conduction with Fourier analysis of the raw temperature data are implemented in order to calculate the instantaneous engine combustion chamber and exhaust pipe heat fluxes. This study concentrates on the correct interpretation of the measured temporal variations of heat fluxes and the examination of the effect of engine load and speed on the cylinder head and exhaust manifold heat flux losses. Many interesting aspects of transient engine heat transfer are revealed. The simultaneous presentation of heat fluxes on the cylinder head and exhaust manifold, together with the engine indicator diagram, sheds light into the mechanisms governing transient heat transfer during an engine cycle. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献