Effect Of Injection Location On Uniformity Of Heavy-duty CNG Engine

Right now, world economy and the auto industry are developing rapidly, the major problemsthat restricting vehicle development and human progress are energy crisis and environmentalpollution. therefore the whole world is looking for clean alternative energy to meet therequirements of increasingly stringent emission regulations and sustainable development.Natural gas as alternative fuels which most widely used and petroleum, has the advantage oflarge reserves, high calorific value, low price and emissions cleaning, but its flamepropagation is too slow and combustion is not stable enough. How to improve combustionstability and uniformity while ensuring the power, fuel consumption and emissions havebecome a hot research now.The aging of the CNG engine system may cause a significant difference in combustionprocess between these cylinders, which will result in increase of the vibration and emission,at the same time, it will produce a great impact on the engine stability and lifetime. Themethod used in this study is collecting the cylinder pressure signals of each cylinders bycylinder pressure sensors, combined with the data given by the combustion analyzer to studyuniformity problems of these cylinders.In this study, we analyze the CA6SL2-30E3N heavy-duty CNG engine uniformity ofcylinders by ECS13the data of condition test, such as IMEP and combustion rate, gain theuniformity variation with speed and load, We know it by reading the literature that onereason of engine combustion uneven is the uneven of intake amount. Therefore, we changethe location of the intake manifold to front and rear, according to the800-2100r/min full loadtest, compare the engine uniformity under the three intake positions. At the same time,examine the impact of the three intake mode on the engine power, fuel consumption andemissions.Conclusions from analyzing the original test engine ESC13intake condition data are asfollows:1. At low speed conditions, the IMEP deviation ratio under25%and100%loads aresignificantly higher than the other loads, when the load reaches50%,75%and100%,the IMEP deviation ratio increases with the increase of speed.2. In the condition of constant load, standard deviation ratio cylinders’ CA10shows anupward trend with increase of speed;25%load at every speed conditions, the standard deviation ratio of cylinders’ CA50are significantly higher than the other three loads; thestandard deviation ratio of CA50at50%and75%loads has less difference, and thestandard deviation ratio of CA50at100%load is higher than the first two.3. In the full-load tests, the standard deviation ratio of IMEP increased first and thendecreased with the speed increased; When the speed reached1300-1400r/min, the bestuniformity appeared that the standard deviation ratio of IMEP is only0.33%; thestandard deviation ratio of CA10and CA50showed an increasing trend as the speedincreases, the standard deviation ratio of CA90decreased with the speed increasingConclusions from changing the intake mode of engine are as follows:1. the standard deviation ratio of IMEP under the front intake mode is higher than the othertwo intake mode in various speeds, the standard deviation ratio of CA10under the frontand rear intake mode have a same trend with the speed increased, the uniformity arebetter than the original intake mode, the standard deviation ratio of CA50of the threeintake mode have a same trend to CA10with the speed increased, and their standarddeviation ratio of CA90is consistent with the increase of speed.2. When the engine work in low-speed conditions, the torque of three intake mode arebasically the same; when speed continues to increase, the torque of the front intakemode is slightly higher than the other two modes, and the torque of the rear intake modeis lowest.3. When the engine speed is within800-1700r/min, the NOx emissions of three intakemode have less significant differences; when the engine work in high-speed conditions,the NOx emissions of the original intake mode is higher than the other two intake modes,the THC emissions increased and then reduced with an increase in speeds. When thespeed reaches1800r/min or more, the THC emissions of original and the front intakemode had a consistent trend with the speed increased, are slightly higher than the rearintake mode.4. When the speed reached800-1800r/min, the gas consumption of the front intake modewas significantly lower than the other two intake modes; when the engine speedincreased to more than1800r/min, the gas consumption of original and the front intakemode had a consistent trend with the speed increased, are superior to the rear intakemode.5. The COV of the CNG engine increased first and then decreased with the speed increased,the COV of each cylinder under front intake mode relatively small, each cylinder did not exceed8%, regardless of which intake modes, one or two cylinders close to the intakemanifold have the highest COV in the six cylinders.