Effects of Late Intake Valve Closing Timing on Thermal Efficiency and Emissions Based on a Two-stage Turbocharger Diesel Engine

Wu, Binyang; Yu, Hao; Pak, Pak; Pei, Yiqiang; Su, Weifeng

doi:10.4271/2013-01-0276

Cited by 12 publications

(11 citation statements)

References 9 publications

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“…Further investigations by Kovács et al [31] demonstrated that a very high turbocharger efficiency is needed to minimise the fuel consumption of the Miller cycle operation. Many other works have also shown that a higher boost pressure is the 121 key enabler for Miller cycle operation with EGR to achieve simultaneous high fuel conversion efficiency and low exhaust emissions [32][33][34].…”

Section: Formation 111mentioning

confidence: 99%

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Variable valve actuation–based combustion control strategies for efficiency improvement and emissions control in a heavy-duty diesel engine

Guan

Pedrozo

Zhao

et al. 2019

International Journal of Engine Research

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High nitrogen oxide levels of the conventional diesel engine combustion often requires the introduction of exhaust gas recirculation at high engine loads. This can adversely affect the smoke emissions and fuel conversion efficiency associated with a reduction of the in-cylinder air-fuel ratio (lambda). In addition, low exhaust gas temperatures at low engine loads reduce the effectiveness of aftertreatment systems necessary to meet stringent emissions regulations. These are some of the main issues encountered by current heady-duty diesel engines. In this work, variable valve actuation–based advanced combustion control strategies have been researched as means of improving upon the engine exhaust temperature, emissions, and efficiency. Experimental analysis was carried out on a single-cylinder heady-duty diesel engine equipped with a high-pressure common-rail fuel injection system, a high-pressure loop cooled exhaust gas recirculation, and a variable valve actuation system. The variable valve actuation system enables a late intake valve closing and a second intake valve opening during the exhaust stroke. The results showed that Miller cycle was an effective technology for exhaust temperature management of low engine load operations, increasing the exhaust gas temperature by 40 °C and 75 °C when running engine at 2.2 and 6 bar net indicated mean effective pressure, respectively. However, Miller cycle adversely effected carbon monoxide and unburned hydrocarbon emissions at a light load of 2.2 bar indicated mean effective pressure. This could be overcome when combining Miller cycle with a second intake valve opening strategy due to the formation of a relatively hotter in-cylinder charge induced by the presence of internal exhaust gas recirculation. This strategy also led to a significant reduction in soot emissions by 82% when compared with the baseline engine operation. Alternatively, the use of external exhaust gas recirculation and post injection on a Miller cycle operation decreased high nitrogen oxide emissions by 67% at a part load of 6 bar indicated mean effective pressure. This contributed to a reduction of 2.2% in the total fluid consumption, which takes into account the urea consumption in aftertreatment system. At a high engine load of 17 bar indicated mean effective pressure, a highly boosted Miller cycle strategy with exhaust gas recirculation increased the fuel conversion efficiency by 1.5% while reducing the total fluid consumption by 5.4%. The overall results demonstrated that advanced variable valve actuation–based combustion control strategies can control the exhaust gas temperature and engine-out emissions at low engine loads as well as improve upon the fuel conversion efficiency and total fluid consumption at high engine loads, potentially reducing the engine operational costs.

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Section: Formation 111mentioning

confidence: 99%

“…Many other works have also shown that a higher boost pressure is the key enabler for Miller cycle operation with EGR to achieve simultaneous high fuel conversion efficiency and low exhaust emissions. 32–34…”

Section: Introductionmentioning

confidence: 99%

Variable valve actuation–based combustion control strategies for efficiency improvement and emissions control in a heavy-duty diesel engine

Guan

Pedrozo

Zhao

et al. 2019

International Journal of Engine Research

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“…24 Many research studies have proved that the boost pressure and the power density output can be improved greatly by using a two-stage turbocharger (2TC). 25,26 In this study, based on a series of matching tests, the optimized 1TC and the optimized 2TC for the test engine were set up. The 2TC consists of a smaller high-pressure turbocharger and a larger low-pressure turbocharger, as shown in Figure 1.…”

Section: The Effect Of the Two-stage Turbocharging System On The Engimentioning

confidence: 99%

Strategies for emissions control in heavy-duty diesel engines to achieve low-emissions combustion with a high efficiency

Chen

Shen

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part D:

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In this paper, the strategies for emission controls to achieve clean and high-efficiency combustion were studied in detail in a common-rail heavy-duty diesel engine coupled with exhaust gas recirculation. The results show that, in comparison with a single-stage turbocharger, a two-stage turbocharger dramatically improves the exhaust gas recirculation recyclability and enhances the air-to-fuel mass flow ratio. Therefore, nitrogen oxide emissions can be reduced to a much lower level, and the nitrogen oxide-brake specific fuel consumption trade-off relationship as well as the nitrogen oxide-soot trade-off relationship can be greatly improved simultaneously at low-speed high-load conditions. However, the peak cylinder pressure increases evidently at high-load conditions for a two-stage turbocharger. The brake specific fuel consumption, the soot emissions and the peak cylinder pressure can be lowered simultaneously by appropriately reducing the compression ratio and optimizing the geometry of the combustion chamber (such as the re-entrant diameter and the bowl depth) as well as using an injector with a tapered nozzle hole. At low-speed high-load conditions, the soot emissions can be reduced obviously without serious penalties in the brake specific fuel consumption when the nitrogen oxide emissions were kept constant by delaying the main-injection timing and reducing the injection pressure. However, it is necessary to employ a higher injection pressure together with a post-injection to reduce the brake specific fuel consumption and the soot emissions at high speeds. The combustion characteristics are mainly dominated by the cetane number of the fuel. With the addition of lower-cetane-number fuel to pure diesel, the ignition delay is prolonged as the exhaust gas recirculation rate increases, thereby also increasing the premixed combustion and reducing the soot emissions sharply. Meanwhile, the crank angle at which there is 50% completion of the accumulated heat release has less influence on the brake thermal efficiency with the addition of lower-cetane-number fuel. 2,5-dimethylfuran, as a novel oxygenated biofuel with a lower cetane number, is superior to gasoline for reducing the soot emissions, which may be a promising and clean alternative in compression ignition engines coupled with exhaust gas recirculation.

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“…Retarding intake valve closing (IVC) timing played a significant role in efficient and clean combustion. [21][22][23][24] Su et al 25 put forward the concept of HD-LTC, which showed great potential of its high thermal efficiency and extremely low engine-out emissions by experimental and numerical study. By retarding IVC timing and raising boost pressure, the in-cylinder charge density is regulated much higher than that of conventional engines.…”

Section: Introductionmentioning

confidence: 99%

Study on transient emission spikes reduction of a heavy-duty diesel engine equipped with a variable intake valve closing timing mechanism and a two-stage turbocharger

Zhou

Liu

Sun

et al. 2018

International Journal of Engine Research

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The overall performance and emission during a speed/torque versus time transient cycle are investigated in a heavy-duty truck engine equipped with an intake valve closing timing mechanism and a two-stage turbocharger system (high-pressure turbine is variable geometry turbine). The performance discrepancy analysis between steady-state and transient operation is completed based on a fairly optimized steady-state baseline. The result shows that during the transient operation, the transient NOx emission can track the steady-state baselines much better than particle matter, and the cumulative NOx in transients is even lower than the cumulative NOx of the steady-state baselines, while the rising particle matter emissions mainly due to appearance in particle matter emission spikes during the cycle. And the transient particle matter spikes appeared almost in two typical transient conditions: sharp acceleration from idling and abrupt load transients. The instantaneous equivalence ratio (F) is found to be the main physical factor governing particle matter spikes formation in transients. Particle matter spikes become prominent when F cannot track the steady-state baseline well or F rises over a critical value of 0.8. The control strategy of intake valve closing timing mechanism-variable geometry turbine-exhaust gas recirculation to bridge the gap of F between the steady-state and the transients has been established, which effectively cut down the emission spikes, reducing particle matter emissions by 32.9% with almost no change in NOx.

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Effects of Late Intake Valve Closing Timing on Thermal Efficiency and Emissions Based on a Two-stage Turbocharger Diesel Engine

Cited by 12 publications

References 9 publications

Variable valve actuation–based combustion control strategies for efficiency improvement and emissions control in a heavy-duty diesel engine

Variable valve actuation–based combustion control strategies for efficiency improvement and emissions control in a heavy-duty diesel engine

Strategies for emissions control in heavy-duty diesel engines to achieve low-emissions combustion with a high efficiency

Study on transient emission spikes reduction of a heavy-duty diesel engine equipped with a variable intake valve closing timing mechanism and a two-stage turbocharger

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