汽油机掺醇燃烧进气油膜湿壁温度预测

对进气口喷射汽油机进气门处传热过程进行了分析,建立了进气油膜吸附壁面温度模型.通过冷机状态起动试验和温升过程数据分析,对已有模型结构进行了细化和改进,并基于试验数据及MATLAB参数辨识工具箱对模型参数进行了辨识.根据模型结构及试验数据,分析了油膜吸附壁面温度的关键影响因素和影响规律,以及不同掺混比例乙醇汽油下的差异.油膜吸附壁面温度变化规律类似一阶惯性系统特性,其温升时间常数可视为进气流量的单值函数,但稳态项与多个发动机工况参数有关,而不同乙醇汽油下油膜吸附壁面温度则差异不大.改进与辨识后油膜吸附壁面温度模型在纯汽油及掺醇汽油下均具有较高的预测精度,可直接用于油膜动态补偿器设计.     

基于神经网络的气缸压力识别研究

对传统的内燃机气缸压力识别方法存在的问题 ,提出了应用人工神经网络方法进行气缸压力识别的新方法。以 BP网络构造气缸压力识别模型。通过对网络的训练 ,用实测的缸盖振动信号识别气缸压力。结果表明 ,利用神经网络进行内燃机气缸压力识别 ,识别结果的重复性好 ,精度较高     

Estimating the charge burning velocity within a hydrogen-enriched gasoline engine

This paper proposed a feasible method for estimating the turbulent burning velocity of gasoline/hydrogen blends in a spark-ignited (SI) engine based on the cumulative heat release fraction, engine speed and engine geometry. The experiment was conducted on a naturally-aspirated port-injection gasoline engine equipped with a hydrogen injection system. The engine was run at 1400 rpm with different loads and hydrogen volume fractions in the intake gas. The test results showed that the addition of hydrogen benefited increasing the burning velocity and advancing the relevant crank angle for the peak burning velocity, due to the high burning and diffusion velocities of hydrogen. At 1400 rpm, a manifolds absolute pressure of 61.5 kPa and stoichiometric conditions, the peak burning velocity was raised from 11.6 to 12.3 and 14.6 m/s, and the relevant crank angle for the peak burning velocity was advanced from 21.0 to 14.0 and 8.6 ^oCA when the hydrogen volume fraction in the intake increased from 0% to 3% and 6%, respectively. Moreover, the effect of hydrogen addition on enhancing the burning velocity of a gasoline engine was more pronounced at low loads than that at high loads.     

Evaluating the effects of boosting intake-air pressure on the performance and environmental-economic indicators in a hydrogen-fueled SI engine

In this paper, the effects of external supercharger application on in-cylinder combustion, performance parameters, fuel efficiency and environmental-economic indicators are discussed together regarding a hydrogen-fueled spark ignition engine operating under a lean mixture. The engine was operated at an engine speed of 1600 rpm, under four different boosting pressures (between 10 kPa and 40 kPa), by optimized ignition timing and being compared to a normally aspirated condition. Hydrogen was injected at five bars into the inlet-air. The results show that the indicated mean effective pressure and thermal efficiency increased by 38.9% and 14.2%, respectively, with a 40 kPa boosting pressure under an optimized ignition timing condition according to the normally aspirated engine, and that the cyclic variation decreased by 15.5%. In addition, under 40 kPa boosting pressure, NO_x emissions increased by 45.2% and its environmental-social cost increased by 21.8%, while specific fuel consumption and fuel cost were reduced by approximately 18.5%.     

An experimental investigation on the use of EGR in a supercharged natural gas SI engine

The use of lean burn technology in spark-ignition engines has been dominant; however, lean burn technique can not economically satisfy the increasingly restricted future emission standards. Consequently, alternative combustion techniques need to be investigated and developed. In this paper, the use of the stoichiometric air-fuel mixture with exhaust gas recirculation (EGR) technique in a spark-ignition natural gas engine was experimentally investigated. Engine performance and NO emissions were studied for both atmospheric and supercharged inlet conditions. It was found that the use of EGR has a significant effect on NO emissions. NO emissions decreased by about 50% when EGR dilution increased from zero with an inlet pressure of 101 kPa to close to the misfire limit with an inlet pressure of 113 kPa. In addition, the use of EGR effectively suppressed abnormal combustion which occurred at higher inlet pressure. The use of higher inlet pressure in the presence of EGR improved engine performance significantly. Engine brake power increased by about 20% and engine fuel consumption decreased by about 7% while NO emissions decreased by about 12% when 5% of EGR dilution was employed with an inlet pressure of 113 kPa compared to using undiluted stoichiometric inlet mixture with an inlet pressure of 101 kPa.     

The effect of the initial charge temperature under various injection timings on the second law terms in a direct injection SI hydrogen engine

In this study, the effect of the initial charge temperature on the second law terms under the various injection timings in a direct injection spark ignition hydrogen fuelled engine has been performed theoretically during compression, combustion and expansion processes of the engine cycle. The first law analysis is done by using the results of a three dimensional CFD code. The results show a good agreement with the experimental data. Also for the second law analysis, a developed in house computational code is applied. The results reveal that the indicated work availability is more affected by varying hydrogen injection timing in comparison with other second law terms. Also increasing the initial charge temperature causes the heat loss availability and exhaust gas availability be increased and indicated work availability, combustion irreversibility and entropy generation be decreased.     

一种具有超宽禁带的S-CSRR新型电磁带隙结构

研究了高速电路领域电源/ 地平面之间的电源完整性问题,并设计出在电源地平面之间加载的一种新型“S”形互补开口谐振环(S鄄CSRR)电磁带隙结构,用以有效阻止同时开关噪声在电源分配网络上的传播。以抑制深度-30 dB 为标准,能够得到高达9 GHz 的超宽禁带,明显优于传统的“L”桥型电磁带隙结构。在电磁干扰方面,空间辐射电场的实验结果显示,在部分频段,该新型电磁带隙结构相比无电磁带隙结构的参考板具有更低的电磁干扰。此外,文章还探讨了该电磁带隙结构作为电源平面时的信号完整性问题。研究表明,在这种结构上采用差分线传输信号,对信号完整性的影响较小。     

简化自燃模型在发动机爆震预测中的应用

提出一种用于汽油机爆震预测的简化自燃模型,该模型由１３ 种成分、２０ 个反应组成。首先在快速压缩机上对模型进行验证,考察模型对反应参数的敏感性,然后将其并入准维湍流燃烧模型中进行爆震预测,预测通过改变发动机的压缩比实现。在提高实际压缩比以后预测到爆震的发生。计算还表明爆震不仅与压缩机比还与燃烧室结构有关。     

Performance and exhaust emissions of a gasoline engine with ethanol blended gasoline fuels using artificial neural network

The purpose of this study is to experimentally analyse the performance and the pollutant emissions of a four-stroke SI engine operating on ethanol–gasoline blends of 0%, 5%, 10%, 15% and 20% with the aid of artificial neural network (ANN). The properties of bioethanol were measured based on American Society for Testing and Materials (ASTM) standards. The experimental results revealed that using ethanol–gasoline blended fuels increased the power and torque output of the engine marginally. For ethanol blends it was found that the brake specific fuel consumption (bsfc) was decreased while the brake thermal efficiency (η_b.th.) and the volumetric efficiency (η_v) were increased. The concentration of CO and HC emissions in the exhaust pipe were measured and found to be decreased when ethanol blends were introduced. This was due to the high oxygen percentage in the ethanol. In contrast, the concentration of CO₂ and NO_x was found to be increased when ethanol is introduced. An ANN model was developed to predict a correlation between brake power, torque, brake specific fuel consumption, brake thermal efficiency, volumetric efficiency and emission components using different gasoline–ethanol blends and speeds as inputs data. About 70% of the total experimental data were used for training purposes, while the 30% were used for testing. A standard Back-Propagation algorithm for the engine was used in this model. A multi layer perception network (MLP) was used for nonlinear mapping between the input and the output parameters. It was observed that the ANN model can predict engine performance and exhaust emissions with correlation coefficient (R) in the range of 0.97–1. Mean relative errors (MRE) values were in the range of 0.46–5.57%, while root mean square errors (RMSE) were found to be very low. This study demonstrates that ANN approach can be used to accurately predict the SI engine performance and emissions.     

小型 LPG 发动机匹配三效催化器的起燃特性研究

对小型点燃式电控LPG发动机匹配三效催化器的冷起动过程进行了试验研究,测量了冷起动过程排气管不同位置的排温变化,对比了催化器不同安装位置、不同点火提前角下的起燃特性。通过优化催化器安装位置,调整发动机起动后的怠速转速和点火提前角来改变排气温度,从而使催化器快速起燃,降低了冷起动过程HC和CO的排放。