Combustion Development to Achieve Engine Thermal Efficiency of 40% for Hybrid Vehicles

Takahashi, Daishi; Nakata, Kohei; Yoshihara, Yasushi; Ohta, Yukinori; Nishiura, Hiroyuki

doi:10.4271/2015-01-1254

Cited by 66 publications

(19 citation statements)

References 7 publications

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“…The flow and turbulence of a mixture are often made more intense to mitigate a decline in the burning velocity as the mixture is further diluted. 1,2,[8][9][10] Yokomori and colleagues 9,10 realized successful engine operation with a uniquely designed tumble port with an air excess ratio l = 1.9. In their experiment, the flow velocity near the spark plug reached approximately 35 m/s.…”

Section: Introductionmentioning

confidence: 99%

Spark ignition and early flame development of lean mixtures under high-velocity flow conditions: An experimental study

Sayama

Kinoshita

Mandokoro

et al. 2018

International Journal of Engine Research

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This study set out to experimentally investigate spark ignition and the subsequent early flame development of lean airfuel mixtures of A/F = 20-30 under high-velocity flow conditions using a uniquely designed swirl chamber. The swirl chamber realizes a high-velocity flow of 65 m/s at the spark plug gap, as well as internal temperature and pressure histories that are equivalent to those of spark-ignition engines, being equipped with an optically accessible engine. The designed swirl chamber clearly captures the characteristic behavior of the spark channels and flames in the vicinity of the spark plug. The results show that the spark channels stretch downstream following the flow and are subject to short circuits or restrikes. In the case of a high ignition energy of 200 mJ, short circuits of the spark channels occur in the early part of the discharge, while restrikes occur in the later parts. With a decrease in the ignition energy, restrikes occur in the earlier parts of the discharge. With a low ignition energy of 65 mJ, restrikes can occur immediately after the electrical breakdown without any significant spark stretch. At a sufficiently low dilution degree of A/F = 20, flames can hold behind the ground electrode of the spark plug, which significantly suppresses the cycle dispersion while also enhancing the combustion in the early stage. With further air dilution, that is, A/F. 20, flames develop, flowing downstream without flame holding. However, temporal flame attachment to the ground electrode is observed during the discharge duration even at A/F = 30, while the attached flames eventually blow off downstream at the end of the spark discharge.

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Section: Introductionmentioning

confidence: 99%

Spark ignition and early flame development of lean mixtures under high-velocity flow conditions: An experimental study

Sayama

Kinoshita

Mandokoro

et al. 2018

International Journal of Engine Research

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“…Moreover, increased flame speed could aid faster flame development and lower COV at elevated dilution. 58,59 With increase in dilution, exhaust temperature reduces which poses a challenge to maintain high after treatment efficiency. In this study, IMEP below 8 bar was not tested and exhaust temperatures remained above the critical limit of 400°C for ethanol and methanol.…”

Section: Discussionmentioning

confidence: 99%

Alcohol lean burn in heavy duty engines: Achieving 25 bar IMEP with high efficiency in spark ignited operation

Mahendar

Larsson

Erlandsson

2020

International Journal of Engine Research

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Knock is the most crucial limitation in attaining the peak load required at high efficiency in heavy duty (HD) spark ignition (SI) engines. Renewable fuels such as ethanol and methanol have high resistance to autoignition and can help overcome this limitation. To reduce knock and improve efficiency further, dilution can be used to add specific heat capacity and reduce combustion temperature. This work studied diluted combustion and knock characteristics of gasoline, ethanol, and methanol on a HD SI single cylinder engine for a wide load range. Ethanol and methanol displayed excellent knock resistance which allowed a peak gross IMEP of 25.1 and 26.8 bar respectively, compared to gasoline which only reached 8.3 bar at [Formula: see text]1.4 with a compression ratio of 13. Over 18% increase in gross IMEP was possible for gasoline and ethanol when increasing air excess ratio from 1 to 1.4. Methanol achieved the target gross IMEP at [Formula: see text]1 and required no spark retard at [Formula: see text]1.6. A peak indicated efficiency above 48% was recorded for ethanol and methanol at [Formula: see text]1.6 and gross IMEP of approximately 21 bar. At part loads, stable operation was possible until [Formula: see text]1.8 for all fuels. Increase in intake temperature showed a marginal improvement in stability but no increase in lean limit. The concept shows promise as diluted combustion of ethanol and methanol reduced knock and achieved diesel baseline load. With optimization, there is potential to improve efficiency further and possible cost savings compared to commercial diesel engines.

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“…Although the techniques such as the lean-burn and the exhaust gas recirculation (EGR) have been proposed for improving the fuel consumption and the exhaust gas emission, they also give an increase in the combustion fluctuation. Some studies have reported that the reduced combustion fluctuation can decrease the harmful exhaust emissions and increase the fuel efficiency [10][11][12][13][14][15][16]. Consequently, it is expected to develop a new method that consider the reduction of combustion fluctuation.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Combustion Fluctuation Reduction Using In-Cylinder Pressure Estimation in Gasoline Engine

Ichiyanagi

Anggono

Dziemińska

et al. 2018

International Journal of Industrial Research and Applied Engineering

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Gasoline engines needs to reduce its negative emission waste and raise its thermal efficiency. Previous studies have shown an improvement of engines by regulating the ignition timing and retaining the engine at certain air-to-fuel ratio. Additional development of the thermal efficiency is anticipated by reducing the oscillation of pressure due to combustion (referred to as combustion fluctuation) during each cycle. Reducing the combustion fluctuations promotes the generation of a stable combustion field and improves fuel consumption. Since the combustion fluctuations are significantly affected by the in-cylinder pressure at compression top dead center (referred to as TDC pressure), the present study proposes a method to estimate the TDC pressure in the next cycle. The estimation was conducted by measuring the in-cylinder pressure at exhaust valve opening in the given cycle. This study also developed the method to reduce the combustion fluctuations by using the TDC pressure estimation and controlling the ignition timing. In our experiments, it was found that the developed methods reduced the fluctuations of the indicated mean effective pressure (IMEP), the maximum in-cylinder pressure, and the TDC pressure by 62.1%, 51.2%, and 38.5%, respectively.

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Combustion Development to Achieve Engine Thermal Efficiency of 40% for Hybrid Vehicles

Cited by 66 publications

References 7 publications

Spark ignition and early flame development of lean mixtures under high-velocity flow conditions: An experimental study

Spark ignition and early flame development of lean mixtures under high-velocity flow conditions: An experimental study

Alcohol lean burn in heavy duty engines: Achieving 25 bar IMEP with high efficiency in spark ignited operation

Experimental Study of Combustion Fluctuation Reduction Using In-Cylinder Pressure Estimation in Gasoline Engine

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