Simulation and experimental investigation of swirl-loop scavenging in two-stroke diesel engine with two poppet valves

2020 ◽  
pp. 146808742091608 ◽  
Author(s):  
Zheng Xu ◽  
Fenzhu Ji ◽  
Shuiting Ding ◽  
Yunhai Zhao ◽  
Yan Wang ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Influence Factors ◽  
Engine Performance ◽  
Trapping Efficiency ◽  
Delivery Ratio ◽  
Tracer Gas ◽  
Simulation And Experiment ◽  
Scavenging Efficiency ◽  
Stroke Engine ◽  
Poppet Valves

Scavenging is becoming one of the determinants of two-stroke engine performance. Efficiency of U-type loop scavenging of two-stroke diesel engine with two poppet valves is generally unsatisfactory due to scavenging short-circuiting and large amount of residual burned gas in cylinder, and it is hard to generate the swirl that facilitates fuel spray mixing and combustion. In order to deal with the above issues, a swirl-loop scavenging configuration is proposed to involve swirl and depress short-circuiting. To investigate swirl-loop scavenging performance, this article simulates the scavenging process by numerical method, optimizes the tracer gas method to measure and evaluate the scavenging performance, as well as analyzes the influence factors. The results demonstrate that, compared with U-type loop scavenging, the trapping efficiency and scavenging efficiency of swirl-loop scavenging respectively increase by 8% and 10%. Change of engine speed has an impact on the delivery ratio and trapping efficiency but load does not. Both intake and exhaust valve timings affect scavenging performance and short-circuiting to a large extent. In addition, the accuracy of tracer gas method in measurement of scavenging performance parameters is improved, and the scavenging efficiency deviation between simulation and experiment is decreased from 6% to 2%.

scholarly journals Scavenging Ports’ Optimal Design of a Two-Stroke Small Aeroengine Based on the Benson/Bradham Model

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2739 ◽  
Author(s):  
Yuan Qiao ◽  
Xucheng Duan ◽  
Kaisheng Huang ◽  
Yizhou Song ◽  
Jianan Qian
Keyword(s):  
Optimal Design ◽  
Tilt Angle ◽  
Initial Conditions ◽  
Engine Performance ◽  
Operating Conditions ◽  
Trapping Efficiency ◽  
Slip Angle ◽  
Width Ratio ◽  
Delivery Ratio ◽  
Scavenging Efficiency

The two-stroke engine is a common power source for small and medium-sized unmanned aerial vehicles (UAV), which has wide civil and military applications. To improve the engine performance, we chose a prototype two-stroke small areoengine, and optimized the geometric parameters of the scavenging ports by performing one-dimensional (1D) and three-dimensional (3D) computational fluid dynamics (CFD) coupling simulations. The prototype engine is tested on a dynamometer to measure in-cylinder pressure curves, as a reference for subsequent simulations. A GT Power simulation model is established and validated against experimental data to provide initial conditions and boundary conditions for the subsequent AVL FIRE simulations. Four parameters are considered as optimal design factors in this research: Tilt angle of the central scavenging port, tilt angle of lateral scavenging ports, slip angle of lateral scavenging ports, and width ratio of the central scavenging port. An evaluation objective function based on the Benson/Bradham model is selected as the optimization goal. Two different operating conditions, including the take-off and cruise of the UAV are considered. The results include: (1) Orthogonal experiments are analyzed, and the significance of parameters are discussed; (2) the best factors combination is concluded, followed by simulation verification; (3) results before and after optimization are compared in details, including specific scavenging indexes (delivery ratio, trapping efficiency, scavenging efficiency, etc.), conventional performance indicators, and the sectional views of gas composition distribution inside the cylinder.

scholarly journals CFD Analysis of a Large Marine Engine Scavenging Process

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 141
Author(s):  
Tomislav Senčić ◽  
Vedran Mrzljak ◽  
Vedran Medica-Viola ◽  
Igor Wolf
Keyword(s):  
Engine Performance ◽  
Passive Scalar ◽  
Trapping Efficiency ◽  
Pollutant Emissions ◽  
Delivery Ratio ◽  
Engine Operation ◽  
Marine Diesel ◽  
Operation Parameters ◽  
Scavenging Efficiency ◽  
Charging Efficiency

The scavenging process is an important part of the two-stroke engine operation. Its efficiency affects the global engine performance such as power, fuel consumption, and pollutant emissions. Slow speed marine diesel engines are uniflow scavenged, which implies inlet scavenging ports on the bottom of the liner and an exhaust valve on the top of the cylinder. A CFD model of such an engine process was developed with the OpenFOAM software tools. A 12-degree sector of the mesh was used corresponding to one of the 30 scavenging ports. A mesh sensitivity test was performed, and the cylinder pressure was compared to experimental data for the analyzed part of the process. The scavenging performances were analyzed for real operation parameters. The influence of the scavenge air pressure and inlet ports geometric orientation was analyzed. The scavenging process is analyzed by means of a passive scalar representing fresh air in the cylinder. Isosurfaces that show the concentration of fresh air were presented. The variation of oxygen and carbon dioxide with time and the axial and angular momentum in the cylinder were calculated. Finally, the scavenging performance for the various operation parameters was evaluated by means of scavenging efficiency, charging efficiency, trapping efficiency, and delivery ratio. It was found that the scavenging efficiency decreases with the engine load due to the shorter time for the process. The scavenging efficiency increases with the pressure difference between the exhaust and scavenging port, and the scavenging efficiency decreases with the increase in the angle of the scavenging ports. It was concluded that smaller angles than the industry standard of 20° could be beneficial to the scavenging efficiency. In the investigation, the charging efficiency ranged from 0.91 to over 0.99, the trapping efficiency ranged from 0.54 to 0.83, the charging efficiency ranged from 0.78 to 0.92, and the delivery ratio ranged from 1.21 to 2.03.

Experimental research on scavenging process of opposed-piston two-stroke gasoline engine based on tracer gas method

2021 ◽  
pp. 146808742110366
Author(s):  
Fukang Ma ◽  
Wei Yang ◽  
Yifang Wang ◽  
Junfeng Xu ◽  
Yufeng Li
Keyword(s):  
Gas Exchange ◽  
Exchange Process ◽  
Delivery Ratio ◽  
Tracer Gas ◽  
Piston Motion ◽  
Trapped Air ◽  
Exchange Performance ◽  
Gdi Engine ◽  
Gas Exchange Process ◽  
Scavenging Efficiency

The scavenging process of two stroke engine includes free exhaust, scavenging, and post intake process, which clears the burned gas in cylinder and suctions the fresh air for next cycle. The gas exchange process of Opposed-Piston Two-Stroke (OP2S) engine with gasoline direct injection (GDI) engine is a uniflow scavenging method between intake port and exhaust port. In order to investigate the characteristics of the gas exchange process in OP2S-GDI engine, a specific tracer gas method (TGM) was developed and the experiments were carried out to analyze the gas exchange performance under different intake and exhaust conditions and opposed-piston movement rule. The results show that gas exchange performance and trapped gas mass are significantly influenced by intake pressure and exhaust pressure. And it has a positive effect on the scavenging efficiency and the trapped air mass. Scavenging efficiency and trapped air mass are almost independent of pressure drop when the delivery ratio exceeds 1.4. Consequently, the delivery ratio ranges from 0.5 to 1.4 is chosen to achieve an optimization of steady running and minimum pump loss. The opposed piston motion phase difference only affects the scavenging timing. Scavenging performance is mainly influenced by scavenging timing and scavenging duration. With the increased phase difference of piston motion, the scavenging efficiency and delivery ratio increased gradually, the trapping efficiency would increase first and decrease then and reaches its maximum at 14°CA.

Simultaneous Reduction of Oxides of Nitrogen and Smoke Emissions by Using EGR Combined With Particulate Trap in a DI Diesel Engine

2006 ◽  
Author(s):  
R. Anand ◽  
N. V. Mahalakshmi
Keyword(s):  
Diesel Engine ◽  
Low Cost ◽  
Direct Injection ◽  
Substantial Reduction ◽  
Load Condition ◽  
Engine Performance ◽  
Trapping Efficiency ◽  
Clay Material ◽  
Oxides Of Nitrogen ◽  
Di Diesel Engine

Exhaust gas recirculation (EGR) combined with particulate trap technology has proven to reduce nitrogen oxides (NOx) and smoke emissions simultaneously at relatively low cost compared to other reduction strategies. An experimental study was conducted on a single cylinder, direct injection (DI) diesel engine to study the effect of EGR on engine performance and emissions under constant speed of 1500 rpm at various loads. In the present work hot and cool EGR were used to control the formation of NOx in a D.I diesel engine. The findings of both hot and cool EGR are discussed and compared at full load condition corresponding to the maximum allowable EGR proportion of 15%. It is found that cool EGR has a substantial reduction in NOx and smoke emissions compared to hot EGR. Based on the above result it is found that suitable particulate trap which is cost effective and high trapping efficiency is needed before the EGR cooler to reduce the smoke emissions to meet the emission standards. In the present study a substrate made of clay material was used in the particulate trap. They were made into spheres and coated with copper and zinc oxide catalyst material. The results have shown that EGR combined with particulate trap simultaneously reduces the NOx and smoke emissions by 63% and 42% respectively where as it increases brake specific fuel consumption by 10% compared to baseline mode.

Research on Hydraulic Free Piston Engine with High Scavenging Efficiency

2015 ◽  
Vol 779 ◽  
pp. 187-191
Author(s):  
Hao Ling Ren ◽  
Tian Liang Lin ◽  
Hai Bo Xie
Keyword(s):  
Diesel Engine ◽  
Fuel Injection ◽  
Injection System ◽  
Fuel Injection System ◽  
Piston Engine ◽  
Free Piston ◽  
The Poor ◽  
Free Piston Engine ◽  
Scavenging Efficiency ◽  
Stroke Engine

The poor scavenging process of the hydraulic free piston engine which uses two-stroke engine as its driver was presented. A two-cylinder, four-stroke diesel engine was proposed to drive the single-piston hydraulic free piston engine to improve the scavenging process. The intake and release valves mechanism and fuel injection system were redesigned to adapt the performance of the single-piston hydraulic free piston engine. Feasibility and reliability of this new structure are verified through simulation.

Improving the Performance of a Crankcase-Scavenged Two-Stroke Engine with a Fluid Diode

1982 ◽  
Vol 196 (1) ◽  
pp. 23-34 ◽  
Author(s):  
E Sher
Keyword(s):  
Theoretical Model ◽  
Gas Exchange ◽  
Theoretical Analysis ◽  
Exchange Process ◽  
Engine Performance ◽  
Delivery Ratio ◽  
Engine Torque ◽  
Model Equations ◽  
Gas Exchange Process ◽  
Stroke Engine

A fluid diode was installed at the inlet port of a crankcase-scavenged two-stroke engine. Experiments on the fired engine showed that the engine torque was significantly improved at low engine speeds. A theoretical model to simulate the gas exchange process, including the flow inside the diode, was developed. The model equations were solved numerically. Theoretical analysis showed that with the diode, backflow was prevented, the delivery ratio was increased and the scavenging mechanism and efficiency were improved. It was concluded that a further improvement in engine performance may be achieved by installing an additional fluid diode at the scavenge port.

Development of the Tracer Gas Method for Large Bore Natural Gas Engines—Part II: Measurement of Scavenging Parameters

2002 ◽  
Vol 124 (3) ◽  
pp. 686-694 ◽  
Author(s):  
D. B. Olsen ◽  
G. C. Hutcherson ◽  
B. D. Willson ◽  
C. E. Mitchell
Keyword(s):  
Natural Gas ◽  
Operating Conditions ◽  
Trapping Efficiency ◽  
Pollutant Emissions ◽  
Boost Pressure ◽  
Tracer Gas ◽  
Gas Industry ◽  
Natural Gas Engines ◽  
Natural Gas Industry ◽  
Scavenging Efficiency

In this work the tracer gas method using nitrous oxide as the tracer gas is implemented on a stationary two-stroke cycle, four-cylinder, fuel-injected large-bore natural gas engine. The engine is manufactured by Cooper-Bessemer, model number GMV-4TF. It is representative of the large bore natural gas stationary engine fleet currently in use by the natural gas industry for natural gas compression and power generation. Trapping efficiency measurements are carried out with the tracer gas method at various engine operating conditions, and used to evaluate the scavenging efficiency and trapped A/F ratio. Scavenging efficiency directly affects engine power and trapped A/F ratio has a dramatic impact on pollutant emissions. Engine operating conditions are altered through variations in boost pressure, speed, back pressure, and intake port restriction.

scholarly journals The Trapping Efficiency Measurement of Two Stroke Cycle Diesel Engine by Tracer Gas Method

1963 ◽  
Vol 6 (23) ◽  
pp. 524-531 ◽  
Author(s):  
Sigeo ISIGAMI ◽  
Yosihiro TANAKA ◽  
Masakazu TAMARI
Keyword(s):  
Diesel Engine ◽  
Efficiency Measurement ◽  
Trapping Efficiency ◽  
Tracer Gas ◽  
Stroke Cycle
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