In-cylinder Flow Characteristics Research Articles

Computational fluid dynamics study of the effects of the re-entrant lip shape and toroidal radii of piston bowl on a high-speed direct-injection diesel engine's performance and emissions

The piston bowl design is one of the most important factors that affect the air-fuel mixing and the subsequent combustion and pollutant formation processes in a direct-injection diesel engine. The bowl geometry and dimensions, such as the pip region, bowl lip area, and toroidal radius, are all known to have an effect on the in-cylinder mixing and combustion process. In order to understand better the effect of re-entrant geometry, three piston bowls with different toroidal radii and lip shapes were investigated using computational fluid dynamics engine modelling. KIVA3V with improved submodels was used to model the in-cylinder flows and combustion process, and it was validated on a high-speed direct-injection engine with a second-generation common-rail fuel injection system. The engine's performance, in-cylinder flow, and combustion, and emission characteristics were analysed at maximum power and maximum torque conditions and at part-load operating conditions. Three injector protrusions and injection timings were investigated at full-load and part-load conditions.

고속 직접분사식 디젤 엔진의 실린더내 유동 해석

고속 직접분사식 디젤 엔진의 실린더내 유동 해석

이색 PIV 기술을 이용한 5밸브 가솔린엔진 연소실 내의 유동특성 분석

A 5-valve(intake 3-valve) engine has been developed to increase engine performance. These engines have a high power caused by the decrease of inertia mass of an intake valve and the increase of intake effective area. In this study, in-cylinder flow patterns were visualized with laser sheet method and velocity profiles at near intake valves were inspected by using a two-color PIV. In addition, steady flow tests were performed to quantify tumble ratio of flow-fields generated by a tumble control valve(TCV). Experimental results of steady flow test show that the cure of tumble ratio in intake 3-valve engine farmed as a S shape with valve lift changes. This tendency is different from the one in intake 2-valve engine. Using laser sheet method and two color PIV method, we can find that the intake flow through upper valve increases and the velocity gradient also slightly increases as valve lift increases. From this study, the in-cylinder flow characteristics around intake valves were made clearly.

New evaluation index for bulk motion of in-cylinder flow through intake port system in cylinder head (II)

The variable intake systems recently tend to be adopted in gasoline engines for fuel economy and emission regulation. In the cases, because both swirl and tumble flows are together induced to the cylinder, in-cylinder flow pattern becomes very complicated so that we cannot decide this flow as one major pattern like swirl or tumble. The purpose of this study is to find new evaluation indexes for in-cylinder flow characteristics instead of a current swirl or a tumble ratio at the end of intake stroke using a steady flow test rig. To do this, port flow rig tests were conducted on the DOHC head varying lift of intake valves. Finally, the angular flow parameter PA and the flow angle (φ) were introduced as new evaluation indexes for in-cylinder angular flow characteristics at the end of intake stroke.

E212 ウォールガイド式直噴ガソリンエンジンの形状特性が燃焼に及ぼす影響

It is necessary to modify port shapes for wall guided gasoline direct injection engine to make stratify mixture distribution. Modification of port shapes affects in-cylinder flow and combustion characteristics. In this study, using PIV method, flow characteristics of a port injection engine, which has two straight ports, shape and direct injection engine, which has a helical and a straight port, compared. Moreover, according to experimental results flow and combustion were calculated for another engine rotation speed. As a result, at medium speed range for DI engine, volumetric efficiency was deteriorated and combustion rate was improved due to increase turbulence intensity.

Investigation of in-cylinder flow patterns in 4 valve S. I. Engine by using single-frame particle tracking velocimetry

The in-cylinder flow field of gasoline engine comprises unsteady compressible turbulent flows caused by the intake port, combustion chamber geometry. Thus, the quantitative analysis of the in-cylinder flow characteristics plays an important role in the improvement of engine performances and the reduction of exhaust emission. In order to obtain the quantitative analysis of the in-cylinder gas flows for a gasoline engine, the single-frame particle tracking velocimetry was developed, which is designed to measure 2-dimensional gas flow field. In this paper, influences of the swirl and tumble intensifying valves on the in-cylinder flow characteristics under the various intake flow conditions were investigated by using this PTV method. Based on the results of experiment, the generation process of swirl and tumble flow in a cylinder during intake stroke was clarified. Its effect on the tumble ratio at the end of compression stroke was also investigated.

Three-dimensional computation of in-cylinder flow and combustion characteristics in diesel engines — Effect of wall impingement models of fuel droplet behavior on combustion characteristics

Abstract A computer code called TurboKIVA was used to perform three-dimensional computations to investigate the effects of fuel spray formation on the combustion and emission characteristics of direct and indirect injection diesel engines. As the first step, the code was modified to facilitate quantitative prediction of soot emissions and to improve prediction accuracy. An investigation was then made of the effects of fuel droplet wall impingement models on combustion characteristics. The results showed that combustion performance was influenced by the models, making it important to select a suitable wall impingement model in predicting NO x and soot emissions based on the operating conditions of IDI diesel engines.

9539185 Three-dimentional computation of in-cylinder flow and combustion characteristics in diesel engines — Effect of wall impingement models of fuel droplets on combustion characteristics Hiroshi Ogawa, Yukio Matsui, Shüji Kimura, Jun-ichi Kawashima (Nissan Motor Co., Ltd.)

9539185 Three-dimentional computation of in-cylinder flow and combustion characteristics in diesel engines — Effect of wall impingement models of fuel droplets on combustion characteristics Hiroshi Ogawa, Yukio Matsui, Shüji Kimura, Jun-ichi Kawashima (Nissan Motor Co., Ltd.)

9435991 Three-dimensional computation of In-cylinder flow and combustion characteristics in a diesel engine: Computation of combustion characteristics in an indirect injection diesel engine: Hiroshi Ogawa, Yukio Matsui, Shuji Kimura, Jun-ichi Kawashima, Nissan Motor Co., Ltd. pp. 1–4, 11 figs., 2 tables, 5 refs

9435991 Three-dimensional computation of In-cylinder flow and combustion characteristics in a diesel engine: Computation of combustion characteristics in an indirect injection diesel engine: Hiroshi Ogawa, Yukio Matsui, Shuji Kimura, Jun-ichi Kawashima, Nissan Motor Co., Ltd. pp. 1–4, 11 figs., 2 tables, 5 refs

Steady and Unsteady Airflow Through the Intake Valve of a Reciprocating Engine

An experimental investigation of the airflow through various axisymmetric intake ports of a motored reciprocating engine is reported. Detailed velocity field measurements obtained by laser Doppler anemometry and for steady and various unsteady flow conditions are presented together with valve discharge coefficients from steady flow tests. The results showed that over the lift range investigated the valve flow exhibited various regimes indicated by the changes in the flow pattern at the valve exit. With a 45-deg seat angle, four regimes were identified compared to three in the case of a 60-deg valve. The overall behavior of the 45-deg valve, however, was found to be generally better. Rounding of the edges of the 45-deg valve reduced the number of flow regimes to two with marked improvements on discharge coefficient. The flow angle at the valve exit depended less on the flow regimes and more on the cylinder confinement, in the absence of which the transition from one regime to another was delayed. The mean flow pattern at the valve exit was found to be insensitive to flow unsteadiness, piston confinement and valve operation and thus could be predicted with reasonable accuracy from steady flow tests. The in-cylinder flow characteristics were also insensitive to valve operation, but strongly depended on piston interaction, flow unsteadiness and residual effects from the previous cycle.