Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carrie...Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carried out. And the improved attenuation curves were obtained, by which the engine noise was predicted. The effect of fuel injection parameters in combustion noise was investigated during the combustion process. At last, the method combining single variable optimization and multivariate combination was introduced to online optimize the combustion noise. The results show that injection parameters can affect the cylinder pressure rise rate and heat release rate, and consequently affect the cylinder pressure load and pressure oscillation to influence the combustion noise. Among these parameters, main injection advance angle has the greatest influence on the combustion noise, while the pilot injection interval time takes the second place, and the pilot injection quantity is of minimal impact. After the optimal design of the combustion noise, the average sound pressure level of the engine is distinctly reduced by 1.0 d B(A) generally. Meanwhile, the power, emission and economy performances are ensured.展开更多
针对集中绕组永磁电机中二倍频(2 f e)径向电磁力导致的空调压缩机振动与噪声问题,提出一种结合定子磁导偏置及转子谐波注入的抑振技术,实现低阶2 f e径向电磁力有效抑制。首先,基于电磁场理论和有限元分析方法,建立了永磁电机的2 f e...针对集中绕组永磁电机中二倍频(2 f e)径向电磁力导致的空调压缩机振动与噪声问题,提出一种结合定子磁导偏置及转子谐波注入的抑振技术,实现低阶2 f e径向电磁力有效抑制。首先,基于电磁场理论和有限元分析方法,建立了永磁电机的2 f e径向电磁力理论模型,分析了齿槽调制效应以及各阶力波对振动响应产生的影响。其次,提出定子旋转辅助槽创新结构,引入磁导偏置因子,显著降低了3阶2 f e径向电磁力幅值;同时提出了“上升楔形”转子结构,主动引入转子3次谐波,有效抑制了6阶2 f e径向电磁力。最后,通过电机振动测试、压缩机噪声测试以及空调系统噪声实验,分析了定子磁导偏置及转子谐波注入技术对振动噪声的抑制效果,验证了该技术对空调压缩机2 f e振动噪音改善的有效性。展开更多
目的比较两种注射速度(1、1.5 m L/s)钆塞酸二钠(Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid,Gd-EOB-DTPA)增强磁共振(magnetic resonance,MR)肝脏动态增强动脉期图像质量的优劣性。方法回顾性评估本院2012年12月至2...目的比较两种注射速度(1、1.5 m L/s)钆塞酸二钠(Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid,Gd-EOB-DTPA)增强磁共振(magnetic resonance,MR)肝脏动态增强动脉期图像质量的优劣性。方法回顾性评估本院2012年12月至2013年9月接受Gd-EOB-DTPA肝脏MR动态增强检查的患者106例,包括注射速度为1 m L/s患者52例,1.5 m L/s患者54例,对动脉期增强图像进行评估。由2名副高以上诊断医师定量评估所有患者肝脏动脉期腹主动脉、肝总动脉、肝脏实质的信噪比(signal noise ratio,SNR)和强化率(contrast-enhancement ratio,CER)的差异性,定性评估腹主动脉、肝总动脉、肝脏实质、门静脉和图像伪影5个项目得分和总分的差异性。结果 Gd-EOB-DTPA注射速度为1 m L/s组和1.5 m L/s组各部分SNR和CER差异无统计学意义(P>0.05),1 m L/s组腹主动脉、肝总动脉强化评分和总分均高于1.5 m L/s组(P<0.05)。结论 Gd-EOB-DTPA注射速度为1 m L/s的肝脏动脉期图像质量优于注射速度为1.5 m L/s的肝脏动脉期图像质量。展开更多
基金Project(2011BAE22B05)supported by the National Science and Technology Pillar Program during the 12th Five-year Plan of China
文摘Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carried out. And the improved attenuation curves were obtained, by which the engine noise was predicted. The effect of fuel injection parameters in combustion noise was investigated during the combustion process. At last, the method combining single variable optimization and multivariate combination was introduced to online optimize the combustion noise. The results show that injection parameters can affect the cylinder pressure rise rate and heat release rate, and consequently affect the cylinder pressure load and pressure oscillation to influence the combustion noise. Among these parameters, main injection advance angle has the greatest influence on the combustion noise, while the pilot injection interval time takes the second place, and the pilot injection quantity is of minimal impact. After the optimal design of the combustion noise, the average sound pressure level of the engine is distinctly reduced by 1.0 d B(A) generally. Meanwhile, the power, emission and economy performances are ensured.
文摘针对集中绕组永磁电机中二倍频(2 f e)径向电磁力导致的空调压缩机振动与噪声问题,提出一种结合定子磁导偏置及转子谐波注入的抑振技术,实现低阶2 f e径向电磁力有效抑制。首先,基于电磁场理论和有限元分析方法,建立了永磁电机的2 f e径向电磁力理论模型,分析了齿槽调制效应以及各阶力波对振动响应产生的影响。其次,提出定子旋转辅助槽创新结构,引入磁导偏置因子,显著降低了3阶2 f e径向电磁力幅值;同时提出了“上升楔形”转子结构,主动引入转子3次谐波,有效抑制了6阶2 f e径向电磁力。最后,通过电机振动测试、压缩机噪声测试以及空调系统噪声实验,分析了定子磁导偏置及转子谐波注入技术对振动噪声的抑制效果,验证了该技术对空调压缩机2 f e振动噪音改善的有效性。
文摘目的比较两种注射速度(1、1.5 m L/s)钆塞酸二钠(Gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid,Gd-EOB-DTPA)增强磁共振(magnetic resonance,MR)肝脏动态增强动脉期图像质量的优劣性。方法回顾性评估本院2012年12月至2013年9月接受Gd-EOB-DTPA肝脏MR动态增强检查的患者106例,包括注射速度为1 m L/s患者52例,1.5 m L/s患者54例,对动脉期增强图像进行评估。由2名副高以上诊断医师定量评估所有患者肝脏动脉期腹主动脉、肝总动脉、肝脏实质的信噪比(signal noise ratio,SNR)和强化率(contrast-enhancement ratio,CER)的差异性,定性评估腹主动脉、肝总动脉、肝脏实质、门静脉和图像伪影5个项目得分和总分的差异性。结果 Gd-EOB-DTPA注射速度为1 m L/s组和1.5 m L/s组各部分SNR和CER差异无统计学意义(P>0.05),1 m L/s组腹主动脉、肝总动脉强化评分和总分均高于1.5 m L/s组(P<0.05)。结论 Gd-EOB-DTPA注射速度为1 m L/s的肝脏动脉期图像质量优于注射速度为1.5 m L/s的肝脏动脉期图像质量。
