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排序方式: 共有118条查询结果,搜索用时 15 毫秒
1.
分析了汽油机缸内气体爆震燃烧压力的频率特性并推导了爆震压力共振频率计算公式。研究表明:在爆震工况下,缸内压力在高频域中有几个共振峰,峰的大小表明了汽油机爆震强度。汽油机的表面振动在这些共振频率峰处也出现相应振动峰。表面振动峰与缸力压内峰值近似成正比。汽油机表面振动峰值可作为爆震强度的评价指标,该结论在CA1102汽油机上得到了证实。 相似文献
2.
电控汽油机爆震故障分析和排除方法研究 总被引:1,自引:0,他引:1
针对目前电控汽油机出现爆震故障产生的因素进行研究,对常用的诊断排除故障的方法进行了对比分析,目的是研究解决电控发动机爆震故障的方法。通过对两则典型的汽车爆震故障诊断排除案例,总结归纳出预防和排除两类常见爆震故障的方法和步骤。实践结果表明了文中方法的可行性和实用性。 相似文献
3.
本文设计了一种基于MATLAB技术的鸡蛋破损检测装置,敲击装置采集声音信号,通过A/D转换输入计算机后与数据库中的信号进行比较,从而判断出被测鸡蛋的好坏。 相似文献
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爆震特征提取是汽油机点火闭环控制的前提和基础。基于集合经验模式分解(Ensemble empirical mode decomposition,EEMD),提出一种汽油机爆震特征提取方法。EEMD通过对信号加入有限幅度的高斯白噪声,利用高斯白噪声频率均匀分布的统计特性使信号在不同尺度上保持连续性,有效地抑制经验模式分解(Empirical mode decomposition,EMD)的模式混叠问题。研究了利用EEMD和EMD两种方法分别从汽油机缸内压力信号和缸盖振动信号中提取爆震特征的可行性和有效性。试验结果表明,对于缸内压力信号,EEMD和EMD均能提取出爆震特征;对于缸盖振动信号,EEMD可以提取出爆震特征,而EMD则由于模式混叠的影响,无法提取爆震特征。 相似文献
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In a combined heat and power (CHP) plant, spark ignition engines must operate at their maximum power to reduce the pay back time. Because of environmental and economic concerns, engines are set with high compression ratios. Consequently, optimal operating conditions are generally very close to those of knock occurrence and heavy knock can severely damage the engine piston.There are two main protection techniques: the curative one commonly used by engine manufacturers and well documented in the literature and the preventive one based on a knock prediction according to the quality of the supplied gas. The indicator used to describe gas quality is the methane number (MN). The methane number requirement (MNR) of the engine is defined, for an engine set (spark advance, air-fuel ratio, and load), as the minimum value of MN above which knock free operation is ensured. To prevent knock occurrence, it is necessary to adapt the engine tuning according to variable gas composition. The objective of the present work is to validate the concept of knock preventive protection. First, a prediction of MNR according to engine settings (ES) is computed through a combustion simulator composed of a thermodynamic 2-zone model. Predicted MNR are compared to experimental results performed on a single-cylinder SI gas engine and show good agreement with numerical results (uncertainty below 1 point). Then, the combustion simulator is used to generate a protection mapping. At last, the knock preventive protection was successfully tested. 相似文献
8.
基于单缸试验机研究了过量空气系数对射流点火发动机性能的影响。通过分析发动机性能曲线、缸内燃烧情况及爆震特性探究射流点火最佳运行区间,并与火花点火燃烧方式进行对比。结果表明,射流点火可以有效提升瞬时放热率并拓展发动机稀燃极限,缩短缸内混合气滞燃期与燃烧持续期,同时燃油经济性有一定提升。在稀燃条件下氮氧化物排放极低。爆震方面,随着点火提前角增大,射流火焰的多点点火效应会在缸内产生明显压力震荡,继续增大点火提前角会诱导末端混合气自燃。因此射流点火爆震缸压表现为两阶段压力震荡,爆震因子集中性高。提升过量空气系数可以降低射流点火爆震因子幅值,使发动机工作在轻微爆震或无爆震状态。 相似文献
9.
建立了氢内燃机一维模型,分别仿真分析了废气再循环(exhaust gas recirculation,EGR)技术和米勒循环技术对抑制爆震及氮氧化物(NO_x)排放的效果,最后结合两种技术探索了可达到的最大压缩比和最好的NO_x排放性能。结果显示EGR技术对抑制NO_x排放更有效,米勒循环对抑制爆震更有效,最终在本研究的工况下,可以将内燃机的压缩比从10.0提升到18.4,指示热效率提升了8.0%,达到了44.87%,同时NO_x排放减少了26.2%,达到了1.937g/(kW·h)。 相似文献
10.
Physicochemical effects of varying fuel composition on knock characteristics of natural gas mixtures
The physicochemical origins of how changes in fuel composition affect autoignition of the end gas, leading to engine knock, are analyzed for a natural gas engine. Experiments in a lean-burn, high-speed medium-BMEP gas engine are performed using a reference natural gas with systematically varied fractions of admixed ethane, propane and hydrogen. Thermodynamic analysis of the measured non-knocking pressure histories shows that, in addition to the expected changes arising from changes in the heat capacity of the mixture, changes in the combustion duration relative to the compression cycle (the combustion “phasing”) caused by variations in burning velocity dominate the effects of fuel composition on the temperature (and pressure) of the end gas. Thus, despite the increase in the heat capacity of the fuel–air mixture with addition of ethane and propane, the change in combustion phasing is actually seen to increase the maximum end-gas temperature slightly for these fuel components. By the same token, the substantial change in combustion duration upon hydrogen addition strongly increases the end-gas temperature, beyond that caused by the decrease in mixture heat capacity. The impact of these variations in in-cylinder conditions on the knock tendency of the fuel have been assessed using autoignition delay times computed using SENKIN and a detailed chemical mechanism for the end gas under the conditions extant in the engine. The results show that the ignition-promoting effect of hydrogen is mainly the result of the increase in end-gas temperature and pressure, while addition of ethane and propane promotes ignition primarily by changing the chemical autoignition behavior of the fuel itself. Comparison of the computed end-gas autoignition delay time, based on the complete measured pressure history of each gas, with the measured Knock-Limited Spark Timing shows that the computed delay time accurately reflects the measured knock tendency of the fuels. 相似文献