目前国内有关压缩天然气汽车高压管路布置方面的工艺规范较少,对于高压管路布局走向、管路长度、管路直径等设计参数的选择及其对储气的利用率、管路中供气稳定性等方面的影响尚缺乏深入研究。为此,采用计算流体力学数值模拟方法,计算...目前国内有关压缩天然气汽车高压管路布置方面的工艺规范较少,对于高压管路布局走向、管路长度、管路直径等设计参数的选择及其对储气的利用率、管路中供气稳定性等方面的影响尚缺乏深入研究。为此,采用计算流体力学数值模拟方法,计算分析了某型压缩天然气公交车供气管路内天然气的流场特性,发现管路的长度、曲率、半径以及气瓶阀通孔结构是影响流场特性的主要因素。研究结果表明:1气瓶阀内部流场存在涡流;2管路内部压降与管路长度呈线性关系;3不同工况下管路内部流场速度与压降呈正相关关系;4管路内部流场压降随着管路半径的增大而减小;5弯管曲率半径越大,内部流场速度和压力在拐弯处过渡越平顺。据此进行了以下优化设计:1优化气瓶阀内部通孔结构,解决了原气瓶阀内部存在涡流的现象;2缩短管路长度可以有效减小管路内部压力损失;3高负荷不利于提高气瓶中天然气的使用率;4增大管路半径可以有效降低管路内部流场的压力损失。优化后整个CNG公共汽车的高压管路压力损失减小了195.6 k Pa。展开更多
The regulated gaseous emissions from 2 China-V compressed natural gas(CNG)buses and 2 China-V diesel buses were investigated using a portable emissions measurement system(PEMS)under real road driving conditions.Compar...The regulated gaseous emissions from 2 China-V compressed natural gas(CNG)buses and 2 China-V diesel buses were investigated using a portable emissions measurement system(PEMS)under real road driving conditions.Compared to diesel buses,CNG buses emit less NOx pollutants,but more HC and CO pollutants based on the test results obtained in this paper.In order to evaluate the pollutant emission status of CNG buses in Beijing,an instantaneous emission model as a function of vehicle speed and vehicle specific power(VSP)was developed and validated based on emission data taken from one CNG bus.The input of the instantaneous emission model consists of driving cycle,vehicle parameters,road conditions,ambient conditions and accessory use,all of which were used to calculate the instantaneous vehicle specific power(VSP).For the core model,a group of pollutant emission maps represented as functions of vehicle speed and VSP were used to calculate the second by second emission rates.Finally,the instantaneous emission rates,emission factors and fuel consumption over the selected driving cycle could be obtained as the model outputs.The predicted results for the emissions and fuel consumption of the CNG bus were very close to the tested emission data.The prediction errors for emission factors and fuel consumption varied in the range of-1.6 2%to-5.8%.展开更多
A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accompli...A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.展开更多
A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different inject...A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.展开更多
文摘目前国内有关压缩天然气汽车高压管路布置方面的工艺规范较少,对于高压管路布局走向、管路长度、管路直径等设计参数的选择及其对储气的利用率、管路中供气稳定性等方面的影响尚缺乏深入研究。为此,采用计算流体力学数值模拟方法,计算分析了某型压缩天然气公交车供气管路内天然气的流场特性,发现管路的长度、曲率、半径以及气瓶阀通孔结构是影响流场特性的主要因素。研究结果表明:1气瓶阀内部流场存在涡流;2管路内部压降与管路长度呈线性关系;3不同工况下管路内部流场速度与压降呈正相关关系;4管路内部流场压降随着管路半径的增大而减小;5弯管曲率半径越大,内部流场速度和压力在拐弯处过渡越平顺。据此进行了以下优化设计:1优化气瓶阀内部通孔结构,解决了原气瓶阀内部存在涡流的现象;2缩短管路长度可以有效减小管路内部压力损失;3高负荷不利于提高气瓶中天然气的使用率;4增大管路半径可以有效降低管路内部流场的压力损失。优化后整个CNG公共汽车的高压管路压力损失减小了195.6 k Pa。
基金Supported by the National Key Research and Development Plan(2016YFC0208005)the National Natural Science Foundation of China(51576016)
文摘The regulated gaseous emissions from 2 China-V compressed natural gas(CNG)buses and 2 China-V diesel buses were investigated using a portable emissions measurement system(PEMS)under real road driving conditions.Compared to diesel buses,CNG buses emit less NOx pollutants,but more HC and CO pollutants based on the test results obtained in this paper.In order to evaluate the pollutant emission status of CNG buses in Beijing,an instantaneous emission model as a function of vehicle speed and vehicle specific power(VSP)was developed and validated based on emission data taken from one CNG bus.The input of the instantaneous emission model consists of driving cycle,vehicle parameters,road conditions,ambient conditions and accessory use,all of which were used to calculate the instantaneous vehicle specific power(VSP).For the core model,a group of pollutant emission maps represented as functions of vehicle speed and VSP were used to calculate the second by second emission rates.Finally,the instantaneous emission rates,emission factors and fuel consumption over the selected driving cycle could be obtained as the model outputs.The predicted results for the emissions and fuel consumption of the CNG bus were very close to the tested emission data.The prediction errors for emission factors and fuel consumption varied in the range of-1.6 2%to-5.8%.
基金Supported by the National Natural Science Foundation of China(50976012)
文摘A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.
基金Supported by National High Technology Research and Development Program ("863" Program) of China (No.2008AA11A114)
文摘A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.
