An Experimental Study on the Effect of Stroke-to-Bore Ratio of Atkinson DISI Engines with Variable Valve Timing

Oh, Sechul; Cho, Seokwon; Seol, Eunsu; Song, Chiheon; Shin, Woojae; Min, Kyoungdoug; Song, Han Ho; Lee, Byeongsoek; Son, Jinwook; Woo, Soo Hyung

doi:10.4271/2018-01-1419

Cited by 17 publications

(6 citation statements)

References 16 publications

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“…Despite the largely dispersed values of N eq in Engine D, the average profile, shown in Figure 17(b), follows closely with the other profiles. Therefore, it can be concluded that the factors discussed in Closure of the fully-developed turbulent flame speed have dominant effects on BD1050 in the simulation, and thus, the extent of their effects is intimately related to their exponents in equation (40).…”

Section: Influencing Factors For Bd1050 and Bd5090mentioning

confidence: 94%

“…As for the evolution of the flame thickness used in the previous modeling, for example, the usage of the inner cutoff in equation (40), we stick to the existing approach to reproduce the flame thinning (i.e. thermodynamically quasi-equilibrium process for flame thickness) since there is no quantitative modeling for thinning due to the flame strain rate.…”

Section: Flame/wall Interactionmentioning

confidence: 99%

“…In Closure of the fully-developed turbulent flame speed, we inspected several factors such as velocity ratio u 0 =S 0 L , length ratio l t =e c , and preheat zone temperature T ph , as in equation (40), influencing flame wrinkling. The next question can be, to what extent does the wrinkling factor N approach the value of N eq .…”

Section: Influencing Factors For Bd1050 and Bd5090mentioning

confidence: 99%

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A universally applicable 0D combustion model with a novel analysis of the critical factors affecting combustion in spark-ignition engines

Kim

Song

2023

International Journal of Engine Research

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Notwithstanding the continuous technological development of spark-ignition engines, the physics of in-cylinder phenomena has not been explicitly clarified to date. Furthermore, the advent of diverse engine technologies and in-cylinder compositions has increased the difficulty of understanding these phenomena using existing analysis methods. Under those circumstances, the modeling based on the fundamental combustion behaviors is becoming critical for analyzing combustion. Built upon the zero-dimensional flame surface density model, therefore, the models proposed herein attempt to reproduce a vast majority of combustion behaviors revealed to date, such as differential diffusion, thermo-diffusive instability, cutoff scales, distributed reaction, and flame quenching. As a result, we successfully predicted the combustion of numerous operating points of four different SI engines, including the extremely lean operating points of gasoline/air mixture up to [Formula: see text]. Furthermore, the extensive thermodynamic ranges are explored for the validation of the models with the aid of continuously variable valve timing modules; the pressure and the calculated temperature of the unburned mixture at ignition timing are varied from 4.5 to 28.6 bar and 559–794 K, respectively. In this study, we suggest an expression for a fully-developed turbulent flame speed well-fitted with the explored ranges of chemical and thermodynamic states by inspecting the influencing factors for flame wrinkling. Additionally, we analyze combustion using the developed models and identify several distinctive features of both stoichiometric and lean-burn points. Lastly, this study reveals the importance of flame thickness (or inner cutoff), which has a comparable or more severe effect on early flame propagation compared to planar laminar flame speed.

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Section: Influencing Factors For Bd1050 and Bd5090mentioning

confidence: 94%

Section: Flame/wall Interactionmentioning

confidence: 99%

Section: Influencing Factors For Bd1050 and Bd5090mentioning

confidence: 99%

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A universally applicable 0D combustion model with a novel analysis of the critical factors affecting combustion in spark-ignition engines

Kim

Song

2023

International Journal of Engine Research

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“…A comparative analysis with the experimental data has been planned to validate the predictability of the developed model. The experimental data of Oh et al was chosen for the validation because their experiments cover not only a variety of operating parameters including engine speed, load, and intake/exhaust valve timing, but also different port and chamber geometries [25]. The three engines used in this study have different stroke-to-bore ratios (SBR) while displacement volumes and compression ratio kept equivalent.…”

Section: Experimental Datamentioning

confidence: 99%

A New Physics-Based Modeling Approach for a 0D Turbulence Model to Reflect the Intake Port and Chamber Geometries and the Corresponding Flow Structures in High-Tumble Spark-Ignition Engines

Kim

et al. 2019

Energies

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Turbulence is one of the most important aspects in spark-ignition engines as it can significantly affect burn rates, heat transfer rates, and combustion stability, and thus the performance. Turbulence originates from a large-scale mean motion that occurs during the induction process, which mainly consists of tumble motion in modern spark-ignition engines with a pentroof cylinder head. Despite its significance, most 0D turbulence models rely on calibration factors when calculating the evolution of tumble motion and its conversion into turbulence. In this study, the 0D tumble model has been improved based on the physical phenomena, as an attempt to develop a comprehensive model that predicts flow dynamics inside the cylinder. The generation and decay rates of tumble motion are expressed with regards of the flow structure in a realistic combustion chamber geometry, while the effects of port geometry on both charging efficiency and tumble generation rate are reflected by supplementary steady CFD. The developed tumble model was integrated with the standard k-ε model, and the new turbulence model has been validated with engine experimental data for various changes in operating conditions including engine speed, load, valve timing, and engine geometry. The calculated results showed a reasonable correlation with the measured combustion duration, verifying this physics-based model can properly predict turbulence characteristics without any additional calibration process. This model can suggest greater insights on engine operation and is expected to assist the optimization process of engine design and operating strategies.

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“…For passenger car applications with spark-ignited engines, many investigations focus on the part-load operating points, where the engine is operated often but the efficiency is usually poor if no special measures are taken. By applying Miller valve timings [14] (intake valves close early, that is, before bottom dead center) or Atkinson valve timings [15] (intake valves close late, that is, after bottom dead center) to control the cylinder charge instead of the conventional throttle, pumping losses are reduced [16]. Thus, the thermal efficiency is increased due to the extended expansion stroke relative to the compression stroke [17].…”

Section: Introductionmentioning

confidence: 99%

Increased Internal Combustion Engine Efficiency with Optimized Valve Timings in Extended Stroke Operation

et al. 2021

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Spark-ignited internal combustion engines are known to exhibit a decreased brake efficiency in part-load operation. Similarly to cylinder deactivation, the x-stroke operation presented in this paper is an adjustable form of skip-cycle operation. It is an effective measure to increase the efficiency of an internal combustion engine, which has to be equipped with a variable valve train to enable this feature. This paper presents an optimization procedure for the exhaust valve timings applicable to any valid stroke operation number greater than four. In the first part, the gas spring operation, during which all gas exchange valves are closed, is explained, as well as how it affects the indicated efficiency and the blow-by mass flow. In the second part, a simulation model with variable valve timings, parameterized with measurement data obtained on the engine test, is used to find the optimal valve timings. We show that in 12-stroke operation and with a cylinder load of 5 Nm, an indicated efficiency of 34.3% is achieved. Preloading the gas spring with residual gas prevents oil suction and thus helps to reduce hydrocarbon emissions. Measurements of load variations in 4-, 8-, and 12-stroke operations show that by applying an x-stroke operation, the indicated efficiency remains high and the center of combustion remains optimal in the range of significantly lower torque outputs.

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An Experimental Study on the Effect of Stroke-to-Bore Ratio of Atkinson DISI Engines with Variable Valve Timing

Cited by 17 publications

References 16 publications

A universally applicable 0D combustion model with a novel analysis of the critical factors affecting combustion in spark-ignition engines

A universally applicable 0D combustion model with a novel analysis of the critical factors affecting combustion in spark-ignition engines

A New Physics-Based Modeling Approach for a 0D Turbulence Model to Reflect the Intake Port and Chamber Geometries and the Corresponding Flow Structures in High-Tumble Spark-Ignition Engines

Increased Internal Combustion Engine Efficiency with Optimized Valve Timings in Extended Stroke Operation

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