Opposed-piston Two-stroke Diesel Engine Research Articles

Effect of Nozzle Structure Parameters on Steady Emission Characteristics in an Opposed-Piston Two-Stroke Diesel Engine

According to 8-Mode cycle of measurement methods for non-road diesel engine of China III from GB20891-2014, the effects of the injection parameters on steady emission characteristics were researched on an opposed-piston two-stroke(OP2S) diesel engine. Test results show that nozzle-tip-protrusion(NTP) can’t make a big influence on emission characteristics, but all of the CO, NOx and PM emissions decrease obviously with the increase of injector hole diameter. Moreover, there exists an optimal nozzle hole cone angle, which can lead to a least composite rate emission. Compared with the original engine, the gross emissions of NOx and HC decrease approximately by 17.2% for improved OP2S engine after nozzle parameters optimization matching, and the improved OP2S engine is able to meet non-road diesel engine of China III emission requirement.

Effect of Layered-Port VVT on Performance of Opposed-Piston Two-Stroke Diesel Engine

AbstractVariable valve timing (VVT) technology effectively improves the performance of diesel engines. The technology is widely used in traditional four-stroke diesel engines. They use a valve-type...

An investigation of the fuel injector dedicated to the aircraft opposed-piston two-stroke diesel engine

The paper presents the research results of the injector construction with the modified injection nozzle. The injector is designed for a prototype opposed-piston aircraft diesel engine. The measurements were based on the Mie scattering technique. The conditions of the experiment corresponded to maximum loads similar to those occurring at the start. The measuring point was selected in line with the analysis of engine operating conditions: combustion chamber pressure at the moment of fuel delivery (6 MPa) and fuel pressure in the injection rail (140 MPa). The analysis focused on the average spray range and distribution, taking into account the differences between holes in the nozzle. As a result of the conducted research, the fuel spray range was defined with the determined parameters of injection. The fuel spray ranges inside the constant volume chamber at specific injection pressures and in the chamber were examined, and the obtained results were used to verify and optimize the combustion process in the designed opposed-piston two-stroke engine.

Study on the synthetic scavenging model validation method of opposed-piston two-stroke diesel engine

The scavenging process of two stroke engines is a complex phenomenon. In two stroke engines, each outward stroke of the piston is a power stroke. This means the operation of clearing the burned gas in cylinder and obtaining fresh air for next cycle must accomplish at same time. The combined intake and exhaust process in two stroke engine is called scavenging. Nowadays, a synthetic scavenging model is widely used to describe the scavenging process of two stroke engines. It represents the time evolution of the in-cylinder residual gas rate and the exhaust residual gas rate. An opposed two stroke diesel engine’s (OP2S) synthetic scavenging profile is calculated through the changes of gas compositions in-cylinder and exhaust pipe by CFD simulation. To validate the accuracy of this profile, a validation method based on tracer gas technique is proposed. First, scavenging parameters including scavenging efficiency and trapping efficiency are calculated by 1D software using the synthetic scavenging profile as a vital boundary condition. The results reveal that the delivery ratio of the OP2S diesel engine should below 140%. Second, use tracer gas technique to measure the scavenging parameters of OP2S diesel engine. In the experimental process, we find the OP2S diesel engine operates steady only if the delivery ratio is higher 50%. The scavenging parameters from 1D simulation and experiment match well which means the synthetic scavenging model received by CFD simulation performs well and validating its effectiveness through tracer gas technique is available.

Study on the Effect of the Nozzle Diameter and Swirl Ratio on the Combustion Process for an Opposed-piston Two-stroke Diesel Engine

There are great differences between combustion in the opposed-piston two-stroke diesel engine and conventional diesel engine, because of the different injection position and the relative position between the spary and the in cylinder flow. In this paper, CFD models base on AVL-FIRE were established. Effects of the nozzle diameter and swirl ratio on the engine combustion were calculated and studied, and matching criteria of nozzle diameter and swirl ratio were summarized. The results show that,the smaller nozzle diameters means the smaller droplet diameters after collapse; Moreover, a proper swirl ratio can improve the mixing process, but if it is too large, droplets are likely to diverge and then accumulate in a restricted region, resulting in the form of rich mixture regions. The best nozzle diameter is 0.1mm while the best swirl ratio is 1.0.

Piston ring lubrication in a two-stroke diesel engine

Miniature capacitance film thickness transducers were fitted to the cylinder liner of an opposed piston two-stroke diesel engine. The minimum film thickness between the rings and liner was measured and the attitude of the rings as they passed the induction ports was determined.