共查询到20条相似文献,搜索用时 203 毫秒
1.
近年来,包括页岩气在内的天然气在北美获得很大关注,而工业用火花点火发动机可以适应不同的燃料,如汽油、液化石油气(LPG)或天然气。日益收紧的废气排放法规还要求工业用火花点火发动机采用带三效催化转化器的反馈式燃料喷射系统。为了响应客户需求,开发了可以燃用任何汽油、LPG或天然气的双燃料发动机。介绍开发该机型所使用的技术和方法。对新机型的汽油机变型,采用计算流体动力学,对喷射器的位置和带稳压箱的进气歧管设计进行优化,并寻求进气歧管、燃料输送管和插件式点火线圈的优化布置。此外,可燃用LPG或天然气的变型机都配备可以布置在狭小空间中的供气装置。通过这些方法,所有变型机都具有与原柴油机进行互换的特性。排放性能满足瞬态工况法规,可选的小型催化消声器扩展了这种发动机适应各种设备的能力。 相似文献
2.
3.
在怠速时,评价火花点火发动机的进气混合物的循环变动程度和它们对平均指示压力的影响。通过一组进气紊流实验来确定发动机输出参数的灵敏度,然后通过灵敏度矩阵,将怠速时观察到的发动机输出变化转化为进气变化来分析。 相似文献
4.
5.
6.
在电容储能点火系统的基础上,利用火花能量转换原理和能量叠加原理,提出了一种有别于传统发动机点火系的"稀燃快燃点火系"。简要介绍和分析了该点火系的组成及工作原理,对其进行了设计研究,通过试验验证了稀燃快燃点火系比传统点火系具有的优越性。结果表明:该点火系统能够提高点火线圈的次级电压,增加火花持续时间,有效提高点火能量的利用率,改善发动机点火性能。该点火系在进行适当匹配后不仅适用于现代高速、稀燃、高压缩比发动机,而且也适用于传统点燃式发动机。 相似文献
7.
高能点火系统点火能量的模拟计算研究 总被引:5,自引:0,他引:5
点火能量是发动机对高能点火系统设计要求的一个综合性的重要参数,它的数值直接反映了火花电流、火花电压随时间变化的数值关系。本文介绍了现代高能点火系统点火能量的测试方法,提出了考虑初级恒流控制与断电特性在内的以Zener稳压管串为火花负载的次级点火能量的计算模型与计算方法,进行了理论计算与实际测试结果的对比,用所提出的模型进行参数变动,分析了点火系统主要参数对火花能量与初、次级能量转换率的影响。 相似文献
8.
影响汽油发动机使用性能的三大要素是密封性、点火性及空燃比。其中进气系统密封性的影响尤其关键,对电控汽油喷射式发动机而言也不例外。 相似文献
9.
10.
11.
本文论述了用非线性方程全近似格式的多重网格法(FAS方法)研究车用内燃机换气瞬态性能的方法,实测了进气管总管某一截面上气体流动参数,用多重网格法对进气管内的气流运动进行了数值计算,直观地描述了车用内燃机进气管各歧管内气体流动的瞬态过程,为改善车用内燃机的性能提供了有效的研究方法。 相似文献
12.
C. L. Myung K. H. Choi I. G. Hwang K. H. Lee S. Park 《International Journal of Automotive Technology》2009,10(2):161-166
In SI engines, valve events have a major influence on volumetric efficiency, fuel economy and exhaust emissions. Moreover,
swirl and tumble motions in the intake charge also improve combustion speed and quality by stratifying the mixture as well
as intensifying the mixing rate of air and fuel. This paper investigates the behaviors of an engine and the combustion phenomenon
for various intake valve timings and intake charge motions using CVVT system and port masking schemes. Test condition includes
a part load and a cold idle condition inclusive of a cold start of the engine. Time-resolved HC and NOx emissions were also
measured at an exhaust port to examine their formation mechanisms and behaviors with fast response HC/NOx analyzers. In conclusion,
the fast burning of fuel and improved combustion quality by enhanced charge motions reduced unburned HC emissions, and advancing
the intake valve opening reduced HC as well as NOx. Furthermore, HCs during the cold transient phase and idle conditions decreased
with recalibrated start parameters such as lean air-fuel ratio and spark retardation via the enhancement of intake charge
motions. 相似文献
13.
14.
15.
G. S. Jung Y. H. Sung B. C. Choi C. W. Lee M. T. Lim 《International Journal of Automotive Technology》2012,13(3):347-353
Although premixed charge compression ignition (PCCI) combustion engines are praised for potentially high efficiency and clean
exhaust, experimental engines built to date emit more hydrocarbons (HCs) and carbon monoxide (CO) than the conventional machines.
These compounds are not only strictly controlled components of the exhaust gas of road vehicles but are also an energy loss
indicator. The prime objective of this study was to investigate the major sources of the HCs formed in the combustion chamber
of an experimental PCCI engine in order to suggest some effective technologies for HC reduction. In this study, to explore
the dominant sources of HC emissions in both operation modes, a single cylinder engine was prepared such that it could operate
using either conventional diesel combustion or PCCI combustion. Specifically, the contributions of the top-ring crevice volume
in the combustion chamber and the bulk quenching of the lean mixture were investigated. To understand the influence of the
shape and magnitude of the crevice on HC emissions, the engine was operated with 12 specially prepared pistons with different
top-ring crevices installed one after another. The engine emitted proportionally more HCs as the depth of the crevice increased
as long as the width remained narrower than the prevailing quench distance. The top-ring-crevice-originated exhaust HCs comprised
approximately 31% of the total HC emissions in the baseline condition. In a series of tests to estimate the effects of bulk
quench on exhaust HC emissions, intake air was heated from 300K to 400K in steps of 25K. With the intake air heated, HC and
CO emissions decreased with a gradually diminishing rate to zero at 375K. In conclusion, the most dominant sources of HC emissions
in PCCI engines were the crevice volumes in the combustion chamber and the bulk quenching of the lean mixtures. The key methods
for reducing HC emissions in PCCI engines are minimizing crevice volume in the combustion chamber and maximizing intake air
temperature allowed based on the permissible NOx level. 相似文献
16.
涡轮增压柴油机可变谐振进气系统的计算研究 总被引:1,自引:0,他引:1
为节省涡轮增压可变谐振进气系统设计的时间和费用,本文研究了该系统模拟计算方法,其中进排气采用一维非定常流动模型,控制阀采用节流孔板模型,计算与试验结果的对比表明模拟计算方法是可行的。通过模拟计算分析了控制阀泄漏和开度对充量系数的影响。 相似文献
17.
A. J. Torregrosa J. Galindo C. Guardiola O. Varnier 《International Journal of Automotive Technology》2011,12(3):359-367
This paper presents a methodology for diesel engine intake line analysis that combines specific element tests and modeling.
The purpose of this methodology is to determine the impact of intake lines, or newly designed intake elements, on the volumetric
efficiency of internal combustion engines while avoiding expensive on-engine tests. For this research, the intake system is
divided into several elements which are individually characterized using flow and impulse test rigs. Next, individual systems
are modeled using a one-dimensional code. Finally, these component models are coordinated to provide an evaluation of the
volumetric efficiency. Intake lines coming from two turbocharged diesel engines are used to illustrate the method. The model
is validated by comparing the model results with the actual system performance evaluated in engine test cells. Discussions
of the feasibility of the technique and on the impact of element model inaccuracies on the overall system model are provided. 相似文献
18.
本文基于并行工程的思想,把循环仿真,CAD建模,快速原型制造和计算机辅助实验等各种先进的设计计算,分析,先进制造技术和实验方法用于内燃机进排气系统的开发过程中的向个环节,使其紧密结合起来,建立了以“软原型”为核心的快速开发环境,并对某内燃机的电子控制喷油谐振进气系统的开发进行了有益的探索。 相似文献
19.
Homogeneous charge compression ignition (HCCI) engines have the potential to raise the efficiency of reciprocating engines during partial load operation. However, the performance of the HCCI engine at high loads is restricted by severe knocking, which can be observed by the excessive pressure rise rate. This is due to the rapid combustion process occurring inside the cylinder, which does not follow the flame propagation that is seen in conventional engines. In this study, a low compression ratio of 9.5:1 for a gasoline engine was converted to operate in HCCI mode with the goal being to expand the stable operating region at high loads. Initially, pure n-heptane was used as the fuel at equivalence ratios of 0.30 to 0.58 with elevated intake charge temperatures of 180 and 90 °C, respectively. The n-heptane HCCI engine could reach a maximum performance at an indicated mean effective pressure (IMEP) of 0.38 MPa, which was larger than the performance found in the literature. To reach an even higher performance, a dual-fuel system was exploited. Methanol, as an anti-detonant additive, was introduced into the intake stream with various amounts of n-heptane at fixed equivalence ratios in the range of 0.42 to 0.52. It was found that the methanol addition cooled the mixture down prior to combustion and resulted in an increased coefficient of variation (COV). In order to maintain stable combustion and keep the pressure rise rate below the limit, the intake charge temperature should be increased. Introduction of 90% and 95% (vol/vol) hydrous methanol showed a similar trend but a lower thermal conversion efficiency and IMEP value. Therefore, a dual fuel HCCI engine could maintain a high thermal conversion efficiency across a wide load and enhance a 5% larger load compared to a pure n-heptane-fuelled HCCI engine. The hydrocarbon (HC) and carbon monoxide (CO) emissions were lower than 800 ppm and 0.10%, respectively. They were less at higher loads. The nitrogen oxides (NO x ) emissions were below 12 ppm and were found to increase sharply at higher loads to a maximum of 23 ppm. 相似文献
20.
Extensive usage of automobiles has certain disadvantages and one of them is its negative effect on environment. Carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx), sulphur dioxide (SO2) and particulate matter (PM) come out as harmful products during incomplete combustion from internal combustion (IC) engines. As these substances affect human health, regulatory bodies impose increasingly stringent restrictions on the level of emissions coming out from IC engines. This trend suggests the urgent need for the investigation of all aspects relevant to emissions. It is required to modify existing engine technologies and to develop a better after-treatment system to achieve the upcoming emission norms. Diesel engines are generally preferred over gasoline engines due to their undisputed benefit of fuel economy and higher torque output. However, diesel engines produce higher emissions, particularly NOx and PM. Aftertreatment systems are costly and occupy more space, hence, in-cylinder solutions are preferred in reducing emissions. Exhaust gas recirculation (EGR) technology has been utilized previously to reduce NOx. Though it is quite successful for small engines, problem persists with large bore engines and with high rate of EGR. EGR helps in reducing NOx, but increases particulate emissions and fuel consumption. Many in-cylinder solutions such as lower compression ratios, modified injection characteristics, improved air intake system etc. are required along with EGR to accomplish the future emission norms. Modern combustion techniques such as low temperature combustion (LTC), homogeneous charge compression ignition (HCCI), premixed charge compression ignition (PCCI) etc. would be helpful for reducing the exhaust emissions and improving the engine performance. However, controlling of autoignition timing and achieving wider operating range are the major challenges with these techniques. A comprehensive review of diesel engine performance and emission characteristics is given in this paper. 相似文献