Modeling of Blow-by in a Small-Bore High-Speed Direct-Injection Optically Accessible Diesel Engine

Zhao, Jia Xue; Lee, Chia-fon F.

doi:10.4271/2006-01-0649

Cited by 16 publications

(3 citation statements)

References 11 publications

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“…In addition, part of these gasses can return to the combustion chamber (blow-back) and be ejected as unburned hydrocarbons. Blow-by has an overall detrimental effect on performances due to the reduction of peak pressure [2], and on lubrication and emissions due to oil transport [3][4][5][6]. Several studies have addressed the phenomenon of blowby.…”

Section: Introductionmentioning

confidence: 99%

Gas escape to crankcase: impact of system parameters on sealing behavior of a piston cylinder ring pack

Delprete

Selmani

Bisha

2019

Int J Energy Environ Eng

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Internal combustion engines are the generators of energy for many transportation applications, but they still have an overall low efficiency due to mechanical and thermal losses. The combustion chamber is the core element of the engine and it ought to be perfectly sealed; however, some of the gas leaks toward the crankcase due to imperfect sealing of the rings. This leakage is known as blow-by and affects efficiency, correct lubrication and emissions. The aim of this paper was to understand, in a more detailed way, how some parameters could affect the sealing efficiency of a ring pack. In particular, ring gaps, ring masses and elastic properties, and ring static twists, were varied from the original and investigated for their influence on the inter-ring dynamics and sealing efficiency. The problem, referred to a turbo diesel engine, was formulated in terms of motion equations for the rings and gas equations for the inter-ring crevices, and solved in © Ricardo RINGPAK solver. The results were compared with the original design and with the reference literature. These results confirm that ring gaps and ring unstable motion have an important role in the phenomenon of gas blow-by. In addition, the second ring emerged to have a more important role on the blow-by reduction with respect to the top ring. However, this phenomenon is complex due to the interaction of several parameters, not all of which were included in this study. Nevertheless, these findings can already be taken into account for further studies or experimental investigations. List of symbols ARing face area subjected to a given pressure, m 2 A gap Gap area, m 2 A p Piston acceleration, m/s 2 BRing radial width, m BDC Bottom dead center * Erjon Selmani

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Section: Introductionmentioning

confidence: 99%

Gas escape to crankcase: impact of system parameters on sealing behavior of a piston cylinder ring pack

Delprete

Selmani

Bisha

2019

Int J Energy Environ Eng

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“…For higher boost as well as larger compression ratios, a significant fraction of the crevice charge is forced into the piston's ringpack (i.e., past the compression ring); this results in a significant time delay for the reemergence of the crevice=ringpack gases into the bulk cylinder volume. To account for this behavior, more detailed modeling is required (e.g., Goldsborough, 2007;Namazian and Heywood, 1982;Zhao & Lee, 2006). Ringpack models are not often used in ROHR analyses however, as they are computationally expensive.…”

Section: Ig Rohr Formulationmentioning

confidence: 99%

On the Rate of Heat Release for High-Boost, Low-Temperature Combustion Schemes: Accounting for Compressibility Effects

Goldsborough

2009

Combustion Science and Technology

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A methodology has been developed to account for compressibility effects (i.e., non-ideal-gas behavior) in the analysis of heat release rates. These effects may be important for advanced, high-boost, low-temperature combustion schemes currently under investigation, as the high pressure and overall lower temperatures can lead to compressibility factors (Z ¼ Pt/RT) that are significantly greater than 1.0. The rate of heat release (ROHR) formulation developed here uses a generalized energy conservation equation where the cylinder is segregated into three distinct regions (i.e., fresh, burned, and mixed); an arbitrary equation of state can be applied to these zones. Crevice/ringpack flows, which can be substantial under high-boost/high-compression ratio (CR) operation, are taken into account using a source/ sink term. The new methodology is demonstrated using pressure-volume traces for six different engine cycles; these traces have been generated using a real gas engine simulator where the heat release is prescribed by a Wiebe-type function. Results are presented using the Redlich-Kwong-Soave equation of state, with comparisons made between the new formulation and conventional ideal gas ROHR results and computed mean gas temperatures. Noticeable differences in ROHR values are seen for cases where Z becomes greater than 1.05; however, computationally significant differences appear important only for very high or extreme CR operation. A real gas equation of state should be used to estimate the mean charge temperature for all boosted LTC operation as the ideal gas temperature can be off by $ 70-300 K under the cases investigated here.

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“…The piston rings main duty is to seal off the combustion chamber, however, their tightness is not perfect and part of the intake gas mixture is lost toward the crankcase. This phenomenon is commonly known as blow-by gas and was recognized to brink negative effects on performances, lubrication and emissions [1][2][3][4][5], in particular Kim et al in [19] found the blow-by gasses to be responsible for 10 to 30 % of the UHC emissions of a SI engine. The initial studies [6][7] have analysed the ring motions in the axial direction, further studies [8][9][10] have also included the motions in the radial direction.…”

Section: Introductionmentioning

confidence: 99%

Engine Speed and Load on the Sealing Capacity of a Piston Ring-Pack

Selmani¹,

Bisha²

2020

EJERS

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The combustion chamber is ought to be perfectly sealed, however, part of the air and fuel mixture can escape from it. Among the several losses there is the gas flow from the inter-ring crevices, which is always present. This leakage is known as blow-by, and affects efficiency, correct lubrication and emissions. The amount of leakage is dependent on many factors, and among the most important are the engine speed and load, which are able to affect the system through the forces applied on it. The aim of this paper was to understand in a more detailed way how the engine speed and load could affect the sealing efficiency of a ring-pack. For this purpose, a complete range of speeds and loads were used in the simulations. The equations of the ring motions and gas dynamics has been implemented and solved in ©Ricardo RINGPAK solver. The results showed that inertia and inter-ring gas pressures drives the sealing behavior of the rings. The blow-by trend showed to decrease with the speed and increase with the load, exception made for the idle condition where the values were different to the other cases, especially at higher speeds. Among the two parameters, the engine speed resulted to affect more significantly the blow-by trend.

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Modeling of Blow-by in a Small-Bore High-Speed Direct-Injection Optically Accessible Diesel Engine

Cited by 16 publications

References 11 publications

Gas escape to crankcase: impact of system parameters on sealing behavior of a piston cylinder ring pack

Gas escape to crankcase: impact of system parameters on sealing behavior of a piston cylinder ring pack

On the Rate of Heat Release for High-Boost, Low-Temperature Combustion Schemes: Accounting for Compressibility Effects

Engine Speed and Load on the Sealing Capacity of a Piston Ring-Pack

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