Effects of Miller cycle and variable geometry turbocharger on combustion and emissions in steady and transient cold process

Wu, Binyang; Zhan, Qiwei; Yu, Xing; Lv, Guijun; Nie, Xiaokun; Liu, Shuai

doi:10.1016/j.applthermaleng.2017.02.074

Cited by 35 publications

(17 citation statements)

References 18 publications

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“…26 Studies also showed that the Miller cycle combined with higher intake pressure can effectively minimise NOx emissions while increasing the engine performance. 27,28…”

Section: Introductionmentioning

confidence: 99%

Miller cycle combined with exhaust gas recirculation and post–fuel injection for emissions and exhaust gas temperature control of a heavy-duty diesel engine

Guan

Pedrozo

Zhao

et al. 2019

International Journal of Engine Research

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Miller cycle has been shown as a promising engine strategy to reduce in-cylinder nitrogen oxide (NOx) formation during the combustion process and facilitate its removal in the aftertreatment systems by increasing the exhaust gas temperature. However, the level of NOx reduction and the increase in exhaust gas temperature achieved by Miller cycle alone is limited. Therefore, research was carried out to investigate the combined use of Miller cycle with other advanced combustion control strategies in order to minimise the NOx emissions and the total cost of ownership. In this article, the effects of Miller cycle, exhaust gas recirculation, and post-injection were studied and analysed on the performance and exhaust emissions of a single cylinder heavy-duty diesel engine. A cost–benefit analysis was carried out using the corrected total fluid efficiency, which includes the estimated urea solution consumption in the NOx aftertreatment system as well as the fuel consumption. The experiments were performed at a low load of 6 bar net indicated mean effective pressure. The results showed that the application of a Miller cycle–only strategy with a retarded intake valve closing at −95 crank angle degree after top dead centre decreased NOx emissions by 21% to 6.0 g/kW h and increased exhaust gas temperature by 30% to 633 K when compared to the baseline engine operation. This was attributed to a reduction in compressed gas temperature by the lower effective compression ratio and the in-cylinder mass trapped due to the retarded intake valve closing. These improvements, however, were accompanied by a fuel-efficiency penalty of 1%. A further reduction in the level of NOx from 6.0 to 3.0 g/kW h was achieved through the addition of exhaust gas recirculation, but soot emissions were more than doubled to 0.022 g/kW h. The introduction of a post-injection was found to counteract this effect, resulting in simultaneous low NOx and soot emissions of 2.5 and 0.012 g/kW h, respectively. When taking into account the urea consumption, the combined use of Miller cycle, exhaust gas recirculation, and post-injection combustion control strategies were found to have relatively higher corrected total fluid efficiency than the baseline case. Thus, the combined ‘Miller cycle + exhaust gas recirculation + post-injection’ strategy was the most effective means of achieving simultaneous low exhaust emissions, high exhaust gas temperature, and increased corrected total fluid efficiency.

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“…26 Studies also showed that the Miller cycle combined with higher intake pressure can effectively minimise NOx emissions while increasing the engine performance. 27,28…”

Section: Introductionmentioning

confidence: 99%

Miller cycle combined with exhaust gas recirculation and post–fuel injection for emissions and exhaust gas temperature control of a heavy-duty diesel engine

Guan

Pedrozo

Zhao

et al. 2019

International Journal of Engine Research

View full text Add to dashboard Cite

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“…However, reverse relation was observed at higher loads. Wu et al examined the impacts of variable geometry turbocharger and MC engine with two‐stage turbocharger and common rail fuel system on emission formations and combustion characteristics. The results demonstrated that the combination of variable geometry turbocharger and MC decreased NO x and soot emissions with the increasing brake thermal efficiency.…”

Section: Introductionmentioning

confidence: 99%

Performance analysis of a novel eco‐friendly internal combustion engine cycle

Gonca

Şahi̇n

2019

Int J Energy Res

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Summary The Miller cycle applications have been performed to diminish NOx released from internal combustion engines (ICEs), in recent years. The Miller cycle provides decreased compression ratio and enhanced expansion ratio; hereby, maximum in‐cylinder combustion temperatures diminish, and NOx formations slow down remarkably. Another less‐known method is Takemura cycle application, which provides heat addition into engine cylinder at constant combustion temperatures. In this study, a novel cycle including the Miller cycle and the Takemura cycle has been developed by using novel numerical models and computing methods with seven processes and a novel way to decrease NOx emissions at higher levels compared with the single applications of known cycles. A comprehensive performance examination of the proposed cycle engine in terms of performance characteristics such as effective power (EFP), effective power density (EFPD), exergy destruction (X), exergy efficiency (ε), and ecological coefficient of performance (ECOP) has been conducted. The impacts of engine operating and design parameters on the performance characteristics have been computationally examined. Furthermore, irreversibilities depending on incomplete combustion loss (INCL), exhaust output loss (EXOL), heat transfer loss (HTRL), and friction loss (FRL) have been considered in the performance simulations. The minimum exergy destruction and maximum performance specifications have been observed with 30 of the compression ratio. Maximum effective power values have been obtained at range between 1 and 1.2 of equivalence ratio. The optimum range for exergy efficiency is between 0.8 and 1 of equivalence ratio. Increasing engine speed has provided enhancing effective power. However, an optimum range has been found for the exergy efficiency that is interval of 3000 to 4000 rpm. The results obtained can be assessed by researchers studying on modeling of the engine systems and designs.

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“…To achieve super-high thermal efficiency, it is necessary to attempt several conditions beyond conventional engine limitations. From the view of energy distributions, the exhaust energy can be recycled by the turbocharger 16,17 or waste heat recovery system, 18 and the energy of unburned products is relatively low. Thus, it is crucial for improving the thermal efficiency by reducing heat transfer energy loss (EL).…”

Section: Introductionmentioning

confidence: 99%

Numerical study on the approach for super-high thermal efficiency in a gasoline homogeneous charge compression ignition lean-burn engine

2019

International Journal of Engine Research

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The approach for achieving super-high thermal efficiency in a gasoline homogeneous charge compression ignition lean-burn engine was studied using numerical simulation. A model engine was designed based on the split cycles, including the low-pressure cycle consisted of the turbocharger system and the high-pressure cycle controlled by the variable effective compression ratio ( ε) and the exhaust gas recirculation (EGR). Based on the model engine, load (L) – Φoxy (F) – EGR (E) – ε (E) cooperative control strategy was proposed to optimize the thermal efficiency and its interactive mechanism was clarified. The results revealed that the core of the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy was the simultaneous optimization of the combustion process and the specific heat ratio ( γ) contributing to the piston work maximization. The optimum combustion phase was found in the range of 4°–9° crank angle after top dead center, and highest combustion rate under the rough combustion restriction was also required. Under this precondition, reducing ε to retard the combustion phase appropriately could mitigate the EGR usage to improve the γ. Based on the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy, increasing the load was found to improve the thermal efficiency effectively by reducing the heat transfer loss. The highest brake thermal efficiency of 50% was reached when the gross indicated mean effective pressure was increased to 15 bar under the conventional engine condition. Further increasing the gross indicated mean effective pressure to 35 bar with elevated peak cylinder pressure of 400 bar could improve the brake thermal efficiency to 54% under the enhanced mechanical strength condition. To pursue super-high thermal efficiency, the approach of thermal insulation for the engine was proved to be more effective. It showed the potential to achieve the super-high brake thermal efficiency over 60% and maintain clean combustion by adopting the load (L) – Φoxy (F) – EGR (E) – ε (E) strategy in the model engine with thermal insulation and high mechanical strength.

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Effects of Miller cycle and variable geometry turbocharger on combustion and emissions in steady and transient cold process

Cited by 35 publications

References 18 publications

Miller cycle combined with exhaust gas recirculation and post–fuel injection for emissions and exhaust gas temperature control of a heavy-duty diesel engine

Miller cycle combined with exhaust gas recirculation and post–fuel injection for emissions and exhaust gas temperature control of a heavy-duty diesel engine

Performance analysis of a novel eco‐friendly internal combustion engine cycle

Numerical study on the approach for super-high thermal efficiency in a gasoline homogeneous charge compression ignition lean-burn engine

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