CAJ | 학술논문

为研究重型车用稀燃天然气发动机碳氢排放规律及影响因素,提供碳氢排放基础数据,提出控制稀燃天然气发动机碳氢排放的方法,该文利用对比试验的方法对进气总管单点混合增压中冷重型车用稀燃天然气发动机的燃烧特性及外特性、负荷特性碳氢排放进行了研究.试验结果表明:发动机在节气门全开的外特性工况运行时,随发动机转速从1000增加到2000 r/min,以曲轴转角计算的速燃期从28°增加到41°;转速保持在2000 r/min 时,负荷从0到100%,速燃期从52°缩短到41°.外特性的甲烷性碳氢(CH4)排放比例较高,占总碳氢(total hydrocarbon, THC)排放的95%以上;推迟点火提前角碳氢排放降低,外特性运行时点火提前角推迟6°,在转速1400~2000 r/min范围内,THC 排放降低了10.1%~15.4%,CH4排放降低了10.9%~16.5%.从空载到75%负荷率范围内,点火提前角推迟6°后,THC 排放在不同负荷点降低的平均幅度为24%左右,CH4降低的平均幅度为33.1%左右.在转速1000~2000 r/min 范围内,随着发动机负荷的提高碳氢排放量增多.标定转速随负荷的增加 CH4排放占 THC 排放的比例升高.该研究为增压中冷单点喷射车用稀燃天然气发动机的碳氢排放控制提供了理论依据.
위연구중형차용희연천연기발동궤탄경배방규률급영향인소,제공탄경배방기출수거,제출공제희연천연기발동궤탄경배방적방법,해문이용대비시험적방법대진기총관단점혼합증압중랭중형차용희연천연기발동궤적연소특성급외특성、부하특성탄경배방진행료연구.시험결과표명:발동궤재절기문전개적외특성공황운행시,수발동궤전속종1000증가도2000 r/min,이곡축전각계산적속연기종28°증가도41°;전속보지재2000 r/min 시,부하종0도100%,속연기종52°축단도41°.외특성적갑완성탄경(CH4)배방비례교고,점총탄경(total hydrocarbon, THC)배방적95%이상;추지점화제전각탄경배방강저,외특성운행시점화제전각추지6°,재전속1400~2000 r/min범위내,THC 배방강저료10.1%~15.4%,CH4배방강저료10.9%~16.5%.종공재도75%부하솔범위내,점화제전각추지6°후,THC 배방재불동부하점강저적평균폭도위24%좌우,CH4강저적평균폭도위33.1%좌우.재전속1000~2000 r/min 범위내,수착발동궤부하적제고탄경배방량증다.표정전속수부하적증가 CH4배방점 THC 배방적비례승고.해연구위증압중랭단점분사차용희연천연기발동궤적탄경배방공제제공료이론의거.
In order to provide emission performance basic data and find a method of controlling hydrocarbon (HC) emissions of the lean-burn natural gas engine, a turbocharged inter-cooled heavy vehicle natural gas engine was studied experimentally to investigate the regularity and influence factors of HC emission. The research was carried on a 6 cylinder turbocharged inter-cooled heavy vehicle natural gas engine. The cylinder diameter of the tested engine is 126 mm, the stroke is 130 mm, the compression ratio is 11 and the rated speed is 2 000 r/min. The intake mode of the engine is intake duct single point electronic controlled injection with supercharge and intercooler. The engine indicator diagram, HC emissions and coefficient of excess air were collected in three different kinds of ignition advance angle cases. The experimental results were statistically analyzed. The method of contrast test was adopted to study the effects of engine speed, engine load rate and ignition advance angle on indicator diagram, heat release rate and HC emission performance of the heavy lean-burn natural gas engine. The combustion heat release rate of external characteristic and load characteristic was analyzed, the proportion of CH4 to THC (total hydrocarbon) and the effect of running conditions on the proportion for the intake duct single point electronic controlled injection lean-burn natural gas engine were specially investigated. The experimental results show that the combustion duration period based on the calculation of crank angle is lengthened along with the increase of speed when running at external characteristic. The rapid combustion period based on the calculation of crank angle increases from 28oto 41owhen the speed increases from 1 000 to 2 000 r/min. The combustion duration period shortens with the increase of load at a certain speed. The rapid combustion period shortens from 52oto 41oin the range of 0 to 100% load rate at the speed of 2 000 r/min. More than 95% of THC is CH4 when the engine running at external characteristic because of the CH4 leakage phenomenon existing in the scavenging process. The emissions of HC at middle and high speed are more than that at low speed when the engine running at external characteristic. The HC emissions rise with the increase of ignition advance angle. The effect of ignition advance angle on HC discharge at large torque speed is the most significant. The HC emissions increase with the improvement of load in the range of speed from 1 000 to 2 000 r/min, and the ratio of CH4 to THC rises with the increase of load at rated speed. For this engine a large proportion of CH4 discharge comes from CH4 leakage existing in the scavenging process, so the optimization of the valve timing and proper reduction of the valve overlap angle through designing new cam profile can be adopted to decrease the leakage of CH4 and then to control the HC emissions of the heavy vehicle natural gas engine. Simulating combustion chambers with different structural parameters by 3D numerical simulation technique and optimizing combustion chamber pit depth, diameter and the squish area can improve the in-cylinder turbulent kinetic energy and increase the burning rate, and then effectively control the engine emissions. Appropriately increasing the compression ratio and increasing the lean burn degree can control the HC emissions and ensure the economy. In addition, refining the calibration of the ignition advance angle according to real-time acquisition of emission data can reduce HC emissions. The study provides a theoretical basis to control HC emissions of the turbocharged inter-cooled single point injection vehicle lean-burn natural gas engine.