Scavenging Ports Research Articles

A methane mode water–oil blended internal combustion engine (ICE)

Abstract In this paper, the authors analyze the combustion mechanism of the methane mode water–oil blended ICE in detail and the optimum water/oil ratio M0, where M 0 =− 4n−m 2 ( mol H 2 O / mol oil )= 9(4n−m) 12n+m+16y ( kg H 2 O / kg oil ) (n refers to the number of carbon atoms of the oil molecule, m refers to the number of hydrogen atoms of the oil molecule, y refers to the number of oxygen atoms of the oil molecule,which is a methane module). The authors recommend two separate injection systems, one of which is the water injection system and the other is the oil injection system. As for the four stroke ICE, the water injection system begins to inject water at the moment when the air inlet valve is closed. As for the two stroke ICE, when the scavenge port closes after the air outlet valve, the water injection starts at the moment when the air inlet valve is closed. When the air outlet valve closes after the scavenge port closes, the water injection starts as soon as the scavenge port is closed. During water injection, its angular duration should be maintained within 30° CA, which will lead to higher combustion efficiency and relatively lower pressure of the water injection system, so that the reliability of the water injection system may be better guaranteed.

Influence of Operating Condition and Geometry on the Oil Film Thickness in Aeroengine Bearing Chambers

Increasing the efficiency of modern jet engines does not only imply to the mainstream but also to the secondary air and oil system. Within the oil system the bearing chamber is one of the most challenging components. Oil films on the chamber walls are generated from oil droplets, ligaments, or film fragments, which emerge from bearings, seal plates and shafts, and enter the bearing chamber with an angular momentum. Furthermore, shear forces at its surface, gravity forces, and the design of scavenge and vent ports strongly impact the behavior of the liquid film. The present paper focuses on the experimental determination of the film thickness in various geometries of bearing chambers for a wide range of engine relevant conditions. Therefore, each configuration was equipped with five capacitive probes positioned at different circumferential locations. Two analytical approaches are used for a comprehensive discussion of the complex film flow.

A Numerical Model for Oil Film Flow in an Aeroengine Bearing Chamber and Comparison to Experimental Data

The work presented forms part of an ongoing investigation, focusing on modeling the motion of a wall oil film present in a bearing chamber and comparison to existing experimental data. The film is generated through the impingement of oil droplets shed from a roller bearing. Momentum resulting from the impact of oil droplets, interfacial shear from the airflow, and gravity cause the film to migrate around the chamber. Oil and air exit the chamber at scavenge and vent ports. A previously reported numerical approach to the simulation of steady-state two-phase flow in a bearing chamber, which includes in-house submodels for droplet-film interaction and oil film motion, has been extended. This paper includes the addition of boundary conditions for the vent and scavenge together with a comparison to experimental results obtained from ITS, University of Karlsruhe. The solution is found to be sensitive to the choice of boundary conditions applied to the vent and scavenge.

小型2サイクルエンジンの掃気形状が燃焼状態に及ぼす影響の解析(機関特性と後処理,内燃機関の燃焼化学と排出物制御)

This paper presents the results of experiments conducted with a 2-cycle engine that was the world's first such engine to comply with the 2000 California emissions regulations for small off-road engine adopted by the U.S. state of California in 2000. This engine is fitted with two scavenging passage that runs around the crankcase and space of between piston and inside of the crankcase before the scavenging port. The aim of this research was to investigate how changes in the quantity of heat transferred to the fresh air as a result of varying the width of the scavenging passage would affect the state of combustion and exhaust gas composition. An ion prove was fitted to the center and end zone of the combustion chamber in order to detect the state of combustion.

Laser Doppler velocimetry measurements of flow within the cylinder of a motored tow-stroke cycle engine-comparison with some computational fluid dynamics predictions

This study was carried out to assess the ability of a computational fluid dynamics (CFD) code to predict the scavenging flow in the cylinder of a two-stroke cycle engine. Predictions were obtained from a CFD simulation of the flow within the cylinder. Due to the apparent sym-metry of the engine port layout, only half of the cylinder volume was modelled. Boundary conditions for the CFD model were obtained from experimentally measured pressure-time histories in the crankcase and exhaust. The two-stroke cycle engine was modified to allow laser Doppler velocimetry (LDV) measurements to be made of the in-cylinder flow. The engine was operated under motoring conditions at 500 r/min with a delivery ratio of 0.7. Although the engine scavenge port layout was geometrically symmetrical, an asymmetrical flow field was identified in the cylinder. As a result of this, a direct comparison of the in-cylinder LDV measured and CFD computed results was not possible. However, LDV and CFD results for the in-cylinder flow are presented to help highlight the dissimilarity between the measured and predicted flow fields. Two-dimensional LDV measurements were made in the cylinder at the transfer ports for a portion of the cycle. A comparison of these LDV measurements with CFD predictions of the in-cylinder velocities at the same locations showed that the CFD model could replicate reasonably well the general trend of the flow. The measured cylinder averaged turbulent kinetic energy was compared with that of the CFD model. The qualitative trend of the overall turbulence generating capacity of the engine was well replicated by the CFD model.

522 小型 2 サイクルエンジンの混合気加熱が燃焼状態に及ぼす影響の実験的研究

This paper presents the results of experiments conducted with a 2-cyle engine that was the world's first such engine to comply with the emissions regulations applied to small off-road engines by U.S. state of California in 2000. This engine is fitted with a scavenging passage that runs around the crankcase before the scavenging port. The aim of this research was to investigate how changes in the quantity of heat transferred to the fresh air as a result of varying the length of the scavenging passage would affect the state of combustion and exhaust gas composition. Two ion probes were fitted to the combustion chamber in order to detect the state of combustion.

405 低公害・小型 2 サイクルエンジンの実験的研究

This paper presents the results of experiments conducted with a 2-cycle engine that was the world's first such engine to comply with the 2000 California emissions regulations for small off-road engine adopted by the U.S state of in 2000. This engine is fitted with a scavenging passage that runs around the crankcase before the scavenging port. The aim of this research was to investigate how changes in the quantity of heat transferred to the fresh air as a result of varying the length of the scavenging passage would affect the state of combustion and exhaust gas composition.

1708 天然ガス 2 ストローク火花点火機関に対する掃気孔噴射燃焼の評価手法

The objective of the present study is to examine the possibility to realize stratified combustion in a 2-stroke spark-ignition engine fueled with CNG. A two-cylinder racing engine with the stroke volume of 397cc was used. Through a preliminary experiment, utilizing several techniques of flow rate measurement, a reliable measurement of CNG flow rate could be established and some gas dynamic effect in engine was suggested. By applying Scavenging port injection, remarkable improvement of BSFC can clearly be shown in comparison with the homogeneously charge operation with a gas mixer.

K-2009 天然ガス2ストローク火花点火機関の性能改善要因と低圧掃気孔噴射燃焼の可能性(S26-3 天然ガス機関の開発)(S26 新燃料,新燃焼,新原動機)

The objective of the present study is to examine the comparison of performance and exhaust emission characteristics between gasoline and CNG fueled to a 2-stroke spark-ignition engine. A water-cooled vertical in-line two-cylinder marine-racing engine with the stroke volume of 397 cc was used as the test engine. It is shown that as for CNG operation increasing the compression ratio has the effect to decrease the BSFC and expand lean-burn.limit. Furthermore, a trial of scavenging port injection was successfully done and has the possibility to realize stratified combustion, but we need to address several problems to make it more attractive.

Oxygen delivery failure resulting from interference with a Bain breathing system

A critical incident is described where the expiratory (scavenging) port of an obsolete version of a Baintype breathing system valve assembly was inadvertently connected to the common gas outlet of an anaesthetic machine. This resulted in the patient being deprived of a supply of fresh gas. This misconnection was made possible by adding a plastic connector to the valve scavenging port and subsequent wrongful misconnection. The patient fortunately suffered no harm. The case highlights the danger of equipment that has been subjected to unauthorized interference.

Monitoring of Ventilation On and Off Cardiopulmonary Bypass

To the Editor: We read the cases described by Thrush et al. [1] with interest. We are in complete agreement with their observations and concerns and agree that the gas flowmeter alone is an inadequate continuous monitor of gas flow to the oxygenator. Venous return tubing oximetry is an available, inexpensive technology that verifies the global adequacy of oxygen delivery. However, we disagree that monitoring exhaust gas for oxygen, carbon dioxide, and anesthetic concentration is technically difficult. If a sidestream sampling gas analyzer is used during conventional ventilation prior to cardiopulmonary bypass, all that is required is to move the gas sampling line from the breathing circuit elbow site (the elbow port can be occluded with a Luer cap or a syringe) to a piece of tubing attached to the oxygenator scavenging port. When this is done, it allows the anesthesiologist to continuously verify that 1) mean expired oxygen concentration is appropriately enriched (i.e., relatively high during normothermia) and that it is lowered when the patient is hypothermic, 2) mean expired CO2 partial pressure is both present (i.e., there is gas flow) and of a reasonable value, and 3) when a potent inhaled anesthetic is used, it is both present when desired and adequately eliminated when not desired just prior to separation from cardiopulmonary bypass [2]. Furthermore, monitoring the oxygenator's mean partial pressure of the inhaled anesthetic also assists in timing the administration of supplemental intravenous drugs for analgesia and amnesia. Obviously, alarm variables can be set for whatever values the user chooses. Some have expressed concern that room air may be entrained via the sampling port. Although possible, this has not been our experience, and one is reassured that entrainment is not an issue by noting that the measured exhaust O2 concentration is within 5% of that set on the O (2) blender. We encourage others to try this inexpensive monitoring adjunct during the care and monitoring of patients undergoing cardiopulmonary bypass. It will make it much more like one standard for monitoring ventilation during cases in which cardiopulmonary bypass is implemented. Emilio B. Lobato, MD Nikolaus Gravenstein, MD Glenn B. Paige, MD Department of Anesthesiology; University of Florida College of Medicine; Gainesville, FL 32610-0254

On the Numerical Analysis of the Scavenging Flow in a Loop-Flow-Type Two-Stroke-Cycle Engine.

In a two-stroke-cycle engine, the scavenging flow plays a very important role in the combustion performance. In this type of engine, the loop-flow scavenging system is superior with regard to maintenance because the engine with this scavenging system has no exhaust valve and so has a simple structure. On the other hand, in this engine, the distance between a scavenging port and an exhaust port is shorter and the short pass flow of fresh air to the exhaust port occurs frequently, hence, the scavenging efficiency is generally inferior to that of a uniflow scavenging type of engine. Many experimental and numerical analyses of the scavenging characteristics of loop-flow type two-stroke-cycle engines have been conducted, but the authors believe that the development of a simulation technique for scavenging flow of this type of engine has not yet been completed. The authors have developed a numerical method for this type of engine. In this report, we present an examination of our numerical method comparing our findings with experimental results.

A Study of Direct Fuel-Injection Two-Stroke Cycle Methanol Engine.

A direct fuel-injection two-stroke cycle engine operated with neat methanol was investigated. The engine performances, combustion and exhaust gas characteristics were analyzed experimentally and were also compared with the results of operations with a carburetor, EFI injection at the intake manifold, and EFI injection at the scavenging port. As a result, the power and the brake thermal efficiency of the direct fuel-injection engine were higher than those of engines operated with a carburetor and the above two EFI methods. The exhausted unburned fuel of the direct fuel-injection engine was lower than that with operation with a carburetor, and holmaldehyde and CO concentration were of the same level as the operations with the carburetor and EFI methods. The NOx concentration of the direct fuel-injection was half the level of the result of carburetor operation. Because a stratified charge using direct fuel-injection activated the combustion of the lean mixture which increases working gas temperature, therefore, the vaporization of injected fuel was promoted by the elevated temperature of the residual gas.

The engine performances and exhaust gas characteristics of methanol-fueled two-cycle engines.

The engine performances and exhaust gas characteristics of methanol-fueled two-cycle engines were investigated. The operating conditions such as engine speed, ignition time, throttle valve opening, air fuel ratio, and compression ratio were widely varied to operate the carbureted methanol engine. Furthermore, the electric-controlled fuel injection nozzle which is installed at the scavenging port was employed to operate the methanol engine. As a result, at the operating field of high engine speed and lean mixture, the brake thermal efficiency with the best ignition time of the two-cycle engine was compared with that of a four-cycle engine, and at the above-mentioned operating conditions, the combustion variations and the harmful exhaust emissions of the two-cycle methanol engine showed relatively low levels.

Airflow in the Cylinder of a 2-Stroke Cycle Uniflow Scavenging Diesel Engine During Compression Stroke

The scavenging process of a 2-stroke cycle engine dominates not only fresh-air charging but also the airflow in a cylinder at the compression end. So, the combustion performance of a 2-stroke cycle diesel engine depends on scavenging efficiency ηs, and the scavenging-air swirl intensity in the cylinder. In this report, first, the scavenging airflow is investigated by operating a 2-stroke cycle engine rig. From the LDV measurement of the air velocity in a cylinder during the compression stroke, it is shown that the scavenging port made by the combination of a large-angle port and a small-angle port has high scavenging ability and sufficient swirl intensity for air-fuel mixing. Secondly, the numerical analysis method of the gas flow in a cylinder during the compression stroke is developed. This method employs an approximation of a 2-D axisymmetrical flow to save computation time, but uses, for the initial condition, the calculated results of a 3-D scavenging flow simulation to ensure the accuracy of the starting swirl-flow pattern which is deeply affected by the port arrangement. Some calculated results are compared with the experimental data, and it is concluded that this method can simulate the flow pattern in a cylinder during the compression stroke with good accuracy.

A study on intake flow characteristics in a two-cycle engine by a fiber laser Doppler Velocimeter.

This paper describes measurement and analysis of intake flow characteristics in a two-cycle engine which have an important effect on engine performance. For a two-cycle engine, there is close correlation between gas flow velocity and pressure. Therefore, it is necessary to elucidate these relations. The gas flows in the intake pipe were measured with a fiber laser Doppler velocimeter (FLDV) which has excellent optical properties. Furthermore, we measured the intake pipe pressure, the exhaust pipe pressure and the scavenging port pressure as well as the intake flow velocity using a developed simultaneous measurement system to clarify their mutual relations. From these measurements, the relations between gas flow velocity and pressure became obvious. In addition, the flow characteristics in the intake pipe were investigated by measuring the velocity at several measurement positions for various operating conditions.

Air flow in cylinder of 2 cycle uniflow scavenging diesel engine at compression stroke. (1st report. Experimental results).

The scavenging process of a 2 stroke cycle engine dominates not only fresh air charging but also the air flow in a cylinder at the compression end. So, the combustion performance of a 2 stroke cycle diesel engine depends on the scavenging efficiency ηs and the scavenging air swirl intensity in the cylinder. In this report the scavenging air flow is investigated by motoring of a 2 cycle engine rig. From the LDV measurement of air velocity in a cylinder at the compression stroke, it is shown that the scavenging port made by the combination of a large angle port and a small angle port has high scavenging ability and sufficient swirl intensity for air-fuel mixing.

Simulation of the Gas Exchange Process of a Two-Stroke Cycle Gasoline Engine

This report deals with a study concerning the scavenging performance of a two-stroke cycle gasoline engine under the following conditions: the throttle of the carburetor is set at variable levels, the delivery ratio is set at a predetermined level, the engine speed is varied, and the scavenging and exhaust ports are set at different heights. If the properly selected factors stipulated for a scavenging model are used, the calculated results can be made as consistent as the measured results of the carburetor set at full throttle, as discussed in the previous reports [1, 2]. The mass diffusion, mixing, and short-circuit factors make up the essential coefficients. The factors represent major characteristics: blow-back, return-blow, and the loss of fresh gases. These phenomena are more clearly illustrated by three-dimensional representations of the gas components in the scavenging passage and exhaust pipe. The analyses of these functions may provide an effective means of improving the scavenging performance, i.e., the delivery ratio, trapping efficiency, and charging efficiency.

Contents, volume 27, 1985

The main drawbacks of two stroke (2S) engines consist in poor engine efficiency and high level of pollutant emissions. The contemporary opening of transfer and exhaust ports during the scavenging process causes the short circuit of fresh air-fuel mixture in case of indirect injection or carbureted engines. Despite the intrinsic strengths such as high power density, simplicity, compactness, lightweight and low production costs, 2S engines have been substituted by four stroke (4S) engines in many applications. Direct injection represents an effective solution to reduce the short circuit of fuel in 2S engines. Usually it is carried out by adopting high-pressure systems but the related increase of complexity and costs is inevitable. In order to maintain the intrinsic simplicity of a 2S engine, the most suitable solution is represented by a Low Pressure Direct Injection (LPDI) system. 2S LPDI engines are characterized by the presence of one or two injectors, working at 5 bar, installed on the cylinder wall. Previous works of the authors have shown the effectiveness of an LPDI system applied to a 300cc single cylinder engine in underpowered version with different ports timing and exhaust system with respect to the full power configuration. In the present paper, the authors show the fine-tuning of a 2S engine in full power configuration provided with two injectors installed on the cylinder and directed towards the exhaust port; the injector nozzles were located above the scavenge ports in order to guarantee the maximum interaction between injected fuel and inlet air flow. The engine has been deeply tested and analyzed at the test bench. Particular attention was paid to definition of the optimal injection timing in order to guarantee the best compromise between performance, efficiency and emissions. The experimental setup and the calibration methodology are discussed in detail. The results show the advantages of the LPDI system in terms of increased engine efficiency and emissions reduction with respect to the original carbureted engine maintaining the same level of performance.

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

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.