CAJ | 학술논문

　　针对柴油机在低速、大负荷工况下引入EGR（exhaust gas recirculation）气体困难的实际情况，该文采用在中冷器后安装一个文丘里管的方法提高对EGR的引射能力。通过计算初步确定了文丘里管的喉口直径，并设计了3种不同结构尺寸的文丘里管，进行了相关试验。试验结果表明，随着发动机转速的提高，气体流量增加，文丘里管的降压作用增强；EGR阀前与文丘里管喉口的压差随着发动机转速先减小后增加，在1100到1600 r/min转速范围内，该压差为负值，不利于引入EGR气体；在2200 r/min时，随着发动机负荷的增加，EGR阀前压力始终大于文丘里管前压力，即使没有文丘里管，发动机也可以顺利引入EGR，但二者压差随着负荷的增加而减小，导致高负荷时 EGR 率降低；文丘里管的降压作用随发动机负荷的增加而增加，EGR 引射能力随负荷的变化不明显；在试验负荷范围内，文丘里管前后的压力损失始终大于5 kPa；在2200 r/min时，3种喉口直径的文丘里管的EGR 引射能力随着负荷的增加均有增强的趋势，但直径较小的文丘里管 EGR 阀前与喉口压差较大，容易实现较高的EGR率；但在1600 r/min时，3种文丘里管的EGR引射能力均随着负荷的增加而减小；当扭矩超过470 N·m时，随着文丘里管喉口直径的增加，EGR 阀前与文丘里管喉口压差逐渐降低，引入 EGR 气体的难度逐渐增加。研究结果可为增压中冷柴油机废气再循环系统文丘里管的设计和应用提供参考。
　　침대시유궤재저속、대부하공황하인입EGR（exhaust gas recirculation）기체곤난적실제정황，해문채용재중랭기후안장일개문구리관적방법제고대EGR적인사능력。통과계산초보학정료문구리관적후구직경，병설계료3충불동결구척촌적문구리관，진행료상관시험。시험결과표명，수착발동궤전속적제고，기체류량증가，문구리관적강압작용증강；EGR벌전여문구리관후구적압차수착발동궤전속선감소후증가，재1100도1600 r/min전속범위내，해압차위부치，불리우인입EGR기체；재2200 r/min시，수착발동궤부하적증가，EGR벌전압력시종대우문구리관전압력，즉사몰유문구리관，발동궤야가이순리인입EGR，단이자압차수착부하적증가이감소，도치고부하시 EGR 솔강저；문구리관적강압작용수발동궤부하적증가이증가，EGR 인사능력수부하적변화불명현；재시험부하범위내，문구리관전후적압력손실시종대우5 kPa；재2200 r/min시，3충후구직경적문구리관적EGR 인사능력수착부하적증가균유증강적추세，단직경교소적문구리관 EGR 벌전여후구압차교대，용역실현교고적EGR솔；단재1600 r/min시，3충문구리관적EGR인사능력균수착부하적증가이감소；당뉴구초과470 N·m시，수착문구리관후구직경적증가，EGR 벌전여문구리관후구압차축점강저，인입 EGR 기체적난도축점증가。연구결과가위증압중랭시유궤폐기재순배계통문구리관적설계화응용제공삼고。
At present, most high-power diesel engines, a majority of diesel engines for automobiles and quite a large proportion of the high performance gasoline engines have adopted the turbocharged intercooled technology. However, owing to an increase of the oxygen content in the mixture after supercharging, NOx emissions in the exhaust will increase. The exhaust gas recirculation (EGR) technology is still a main method to reduce the NOx emissions. Aiming at the practical circumstances of difficulty in introducing exhaust gas recirculation (EGR) with diesel engines under the operating conditions of low speeds and full loads, a venturi was installed after the intercooler in order to improve its introduction ability of EGR. A throat diameter of a venturi was preliminarily obtained by calculating with the help of related formula, and based on this, three sorts of venturi-tubes with different structural dimensions were designed, and then some experimental research was also carried out. The results indicate that with the increase of engine speeds, the gas flow increased and the function of reducing the throat pressure of a venturi was enhanced. The difference between the pressure upstream of the EGR valve and the pressure of inside the throat of the venturi decreased first and then increased along with the speeds, and at the speed range of from 1 100 r/min to 1 600 r/min, this difference value was negative, so it is unfavorable to introduce EGR. At the speed of 2 200 r/min and along with the increase of the engine loads, the pressure upstream of the EGR valve was always greater than the pressure upstream of a venturi and the engine could introduce EGR easily even without a venturi. However, the difference of both pressures decreased along with the increase of engine loads, which led to a lower EGR rate at high loads. The effects of reducing the throat pressure of a venturi increased and the variation of introduction ability of EGR was not obvious along with the increase of engine loads. The difference between the pressure upstream and downstream of the venturi was invariably greater than 5 kPa throughout the test load range. With the increase of engine loads, the introduction ability of EGR of the venturi with three different throat diameters had a rising trend at the speed of 2 200 r/min, but the difference between the pressure upstream of an EGR valve and the throat pressure of a venturi with a smaller diameter was higher than that of the venturi with a bigger diameter, and it is favorable to realize a high EGR rate;while at the speed of 1 600 r/min. The introduction ability of EGR of the venturi with three different throat diameters decreased along with the increase of engine loads. When the engine torque was above 470 N·m, along with the increase of the throat diameter of a venturi, the difference between the pressure upstream of the EGR valve and the pressure of inside the throat of the venturi decreased gradually, and the difficulty in introducing the EGR increased. The research results provide a reference of design and application of venturi in the EGR system of a turbocharged intercooled diesel engine.