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An Investigation of the Effects of Engine Size and Rotation Speed on Diesel Combustion based on Similarity Rules

Hokkaido University-Yoshimitsu Kobashi, Yuma Tanaka, Gen Shibata, Hideyuki Ogawa
  • Technical Paper
  • 2019-01-2181
Published 2019-12-19 by SAE International in United States
This paper presents a study on the effects of the engine size and rotation speed on diesel combustion characteristics and engine performance of two differently sized diesel engines (85 mm and 135 mm bores). For simplification of the evaluation, the experimental conditions were set based on the similarity rules proposed by Chikahisa. The combustion characteristics and the indicated thermal efficiencies were compared for the small and the large engines at the same engine speed. To examine the effects of the velocities of the in-cylinder gas and the fuel spray on the combustion and the thermal efficiency, the engine speed was changed in the small engine, while maintaining a non-dimensional engine speed.
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Thermal Efficiency Improvements with Split Primary Fuel Injections in Semi-Premixed Diesel Combustion with Multi-Peak Shaped Heat Release

Hokkaido University-Kazuki Inaba, Yosuke Masuko, Yanhe Zhang, Yoshimitsu Kobashi, Gen shibata, Hideyuki Ogawa
  • Technical Paper
  • 2019-01-2170
Published 2019-12-19 by SAE International in United States
To improve the combustion characteristics in semi-premixed diesel combustion, consisting in the first-stage premixed combustion of the primary fuel injection and the second-stage spray combustion of the secondary injection, the effect of splitting the primary injection was investigated in a diesel engine and analyzed with a CFD. The indicated thermal efficiency improves due to reductions in heat transfer losses to the in-cylinder wall and the combustion noise is suppressed with the split primary injections. The CFD analysis showed that the reduction in heat transfer loss with the split primary injections is due to a decrease in the combustion quantity near the combustion chamber wall.
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A Study of a Lean Homogeneous Combustion Engine System with a Fuel Reformer Cylinder

Hokkaido University-Shuntaro Ishiguro, Gen Shibata, Hideyuki Ogawa, Yoshimitsu Kobashi, Yusuke Watanabe
YANMAR Co., Ltd.-Go Asai, Yuki Tokuoka, Thomas Bayer
  • Technical Paper
  • 2019-01-2177
Published 2019-12-19 by SAE International in United States
The Dual-Fuel (DF) combustion is a promising technology for efficient, low NOx and low exhaust particulate matter (PM) engine operation. To achieve equivalent performance to a DF engine with only the use of conventional liquid fuel, this study proposes the implementation of an on-board fuel reformation process by piston compression. For concept verification, DF combustion tests with representative reformed gas components were conducted. Based on the results, the controllability of the reformed gas composition by variations in the operating conditions of the reformer cylinder were discussed.
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Thermal Efficiency Improvement and its Mechanism at Low Load Conditions in Semi-Premixed Diesel Combustion with Twin Peak Shaped Heat Release

Hokkaido University-Kazuki Inaba, Yosuke Masuko, Yanhe Zhang, Yoshimitsu Kobashi, Gen Shibata, Hideyuki Ogawa
Published 2019-04-02 by SAE International in United States
Semi-premixed diesel combustion with a twin peak shaped heat release with the two-stage fuel injection (twin combustion) has the potential to establish efficient, low emission, and low noise operation. However, with twin combustion at low loads the indicated thermal efficiencies are poorer than at medium loads due to the lower combustion efficiencies. In this report, to increase the combustion efficiencies at low loads, the thermal efficiency related parameters were investigated in a 0.55 L single cylinder diesel engine. The results show that the indicated thermal efficiency improves with increases in the intake gas temperatures at low loads. However, at the higher loads where the combustion efficiencies are somewhat higher the indicated thermal efficiencies decrease with increases in the intake gas temperatures due to increases in the cooling losses. At the low load condition below 300 kPa IMEP, the indicated thermal efficiency is higher and the combustion noise is lower in the twin combustion than in the single premixed combustion. Further, the combustion characteristics of twin and single premixed diesel combustion at low loads were analyzed…
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Kinetic Modeling of Ammonia-SCR and Experimental Studies over Monolithic Cu-ZSM-5 Catalyst

Hokkaido University-Wataru Eijima, Gen Shibata, Yoshimitsu Kobashi, Ryutaro Koiwai, Hideyuki Ogawa, Kenichi Shimizu
Waseda University-Jin Kusaka
Published 2019-01-15 by SAE International in United States
Ammonia-selective catalytic reduction (SCR) systems have been introduced commercially in diesel vehicles, however catalyst systems with higher conversion efficiency and better control characteristics are required to know the actual emissions during operation and the emissions in random test cycles. Computational fluid dynamics (CFD) is an effective approach when applied to SCR catalyst development, and many models have been proposed, but these models need experimental verification and are limited in the situations they apply to. Further, taking account of redox cycle is important to have better accuracy in transient operation, however there are few models considering the cycle. Model development considering the redox reactions in a zeolite catalyst, Cu-ZSM-5, is the object of the research here, and the effects of exhaust gas composition on the SCR reaction and NH3 oxidation at high temperatures are investigated. The simulations are compared with the experimental results of a surrogate gas, a mixture of nitrogen monoxide (NO), oxygen (O2), water vapor (H2O), and nitrogen (N2), and the accuracy of the developed model is validated. To investigate the effects of O2…
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Chemical Reaction Processes of Fuel Reformation by Diesel Engine Piston Compression of Rich Homogeneous Air-Fuel Mixture

SAE International Journal of Engines

Hokkaido University-Yusuke Watanabe, Shuntaro Ishiguro, Gen Shibata, Hideyuki Ogawa, Yoshimitsu Kobashi
YANMAR Co., Ltd.-Go Asai
  • Journal Article
  • 2017-32-0120
Published 2017-11-15 by Society of Automotive Engineers of Japan in Japan
To extend the operational range of premixed diesel combustion, fuel reformation by piston induced compression of rich homogeneous air-fuel mixtures was conducted in this study. Reformed gas compositions and chemical processes were first simulated with the chemistry dynamics simulation, CHEMKIN Pro, by changing the intake oxygen content, intake air temperature, and compression ratio. A single cylinder diesel engine was utilized to verify the simulation results. With the simulation and experiments, the characteristics of the reformed gas with respect to the reformer cylinder operating condition were obtained. Further, the thermal decomposition and partial oxidation reaction mechanisms of the fuel in extremely low oxygen concentrations were obtained with the characteristics of the gas production at the various reaction temperatures.The main reformed products were hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and ethylene (C2H4) and the results indicated that the reforming depends on the maximum temperature in the cylinder, however, the amount of reformed gas is lower than the values predicted by the CHEMKIN simulation.
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An Investigation of the Transient DPF Pressure Drop under Cold Start Conditions in Diesel Engines

Hokkaido Univ.-Yoshimitsu Kobashi, Shun Oooka, Lin Jiang, Jun Goto, Hideyuki Ogawa, Gen Shibata
Published 2017-10-08 by SAE International in United States
To monitor emission-related components/systems and to evaluate the presence of malfunctioning or failures that can affect emissions, current diesel engine regulations require the use of on-board diagnostics (OBD). For diesel particulate filters (DPF), the pressure drop across the DPF is monitored by the OBD as the pressure drop is approximately linear related to the soot mass deposited in a filter. However, sudden acceleration may cause a sudden decrease in DPF pressure drop under cold start conditions. This appears to be caused by water that has condensed in the exhaust pipe, but no detailed mechanism for this decrease has been established. The present study developed an experimental apparatus that reproduces rapid increases of the exhaust gas flow under cold start conditions and enables independent control of the amount of water as well as the gas flow rate supplied to the DPF. The results show that the sudden decrease in the DPF pressure drop is caused by the water in the developed system used here. Observations of the soot cake layers in the DPF show that the…
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Combustion Noise Reduction with High Thermal Efficiency by the Control of Multiple Fuel Injections in Premixed Diesel Engines

SAE International Journal of Engines

Hokkaido University-Gen Shibata, Hideyuki Ogawa, Yuki Okamoto, Yasumasa Amanuma, Yoshimitsu Kobashi
  • Journal Article
  • 2017-01-0706
Published 2017-03-28 by SAE International in United States
Premixed diesel combustion is effective for high thermal efficiency and reductions of NOx and PM emissions, but a reduction of combustion noise is necessary for medium-high load engine operation. The control of the fuel injection has become more accurate because of the technical progress of the common rail fuel injection system, and the target heat release shape, calculated by computation, can be achieved by control of EGR, boosting, fuel injection timing, and injection quantity of multiple fuel injections.In this paper, the reduction of premixed diesel combustion noise maintaining high thermal efficiency has been investigated by the control of injection timings and heating values of multiple fuel injections. There are two aspects of the combustion noise reduction by multiple fuel injections. One is the reduction of the maximum rate of pressure rise in each combustion cycle, and the other is noise reduction effects by the noise cancelling spike (NCS) combustion.The research was conducted with both engine simulations and experiments. In combustion noise simulations, the heat release history of multiple injections was approximated by Wiebe functions and…
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Impingement and Adhesion on Cylinder Liners with Post Diesel Fuel Injections

Hokkaido University-Gen Shibata, Hideyuki Ogawa, Fukei Sha, Kota Tashiro
Published 2016-10-17 by SAE International in United States
Diesel particulate filters (DPF) are widely used in diesel engines, and forced regeneration is necessary to remove particulate matter (PM) accumulating on the DPF. This may be achieved with fuel injected after the main combustion is complete, the socalled “post fuel injection”, and supplied to the diesel oxidation catalyst (DOC) upstream of the DPF. This increases the exhaust gas temperature in the DOC and the DPF is regenerated with the high temperature gas flow. In most cases, the post fuel injection takes place at 30-90CA ATDC, and fuel may impinge on and adhere to the cylinder liner wall in some cases. Buddie and Pischinger [1] have reported a lubricant oil dilution with the post fuel injection by engine tests and simulations, and adhering fuel is a cause of worsening fuel consumption.In this paper, the impingement and adhesion of post diesel fuel injections on the cylinder liner was investigated by an optical method with a high pressure constant volume chamber (ϕ110mm, 883cm3). The pressure and temperature are increased by the combustion of a spark ignited ethylene-air…
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Performance Improvements in a Natural Gas Dual Fuel Compression Ignition Engine with 250 MPa Pilot Injection of Diesel Fuel as an Ignition Source

Hokkaido University-Hideyuki Ogawa, Gen Shibata, Jun Goto, Lin Jiang
Published 2016-10-17 by SAE International in United States
The engine performance and the exhaust gas emissions in a dual fuel compression ignition engine with natural gas as the main fuel and a small quantity of pilot injection of diesel fuel with the ultra-high injection pressure of 250 MPa as an ignition source were investigated at 0.3 MPa and 0.8 MPa IMEP. With increasing injection pressure the unburned loss decreases and the thermal efficiency improves at both IMEP conditions. At the 0.3 MPa IMEP the THC and CO emissions are significantly reduced when maintaining the equivalence ratio of natural gas with decreasing the volumetric efficiency by intake gas throttling, but the NOx emissions increase and excessive intake gas throttling results in a decrease in the indicated thermal efficiency. Under the 250 MPa pilot injection condition simultaneous reductions in the NOx, THC, and CO emissions can be established with maintaining the equivalence ratio of natural gas by intake gas throttling. Two-stage split pilot injection of diesel fuel effectively reduces the maximum rate of pressure rise and the NOx emissions without deteriorations in the thermal efficiency…
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