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Kawahara N.,Okayama University | Tomita E.,Okayama University | Ohtsuki A.,Okayama University | Aoyagi Y.,New ACE Institute Company Ltd
Proceedings of the Combustion Institute | Year: 2011

Cycle-resolved residual gas fraction measurements were made inside a heavy-duty diesel engine using an infrared absorption method. An in situ laser infrared absorption method was developed using an optical fiber sensor and a 4.301-μm quantum cascade laser (QCL) as the light source. We discuss the feasibility of obtaining in situ CO2 concentration measurements inside the engine combustion chamber using the newly developed optical fiber sensor system. Lambert-Beer's law can be applied for the case of a single absorption line of CO2, and the dependence of the CO2 molar absorption coefficient on the ambient pressure and temperature of was determined using a constant volume vessel. This coefficient decreased with increasing pressure, indicating almost constant at pressures over 1.0 MPa. CO2 concentration measurements were made in a compression-expansion engine in order to calibrate the measurement system. The feasibility of the optical fiber sensor system was then investigated in a heavy-duty diesel engine. We were able to measure the CO2 concentration inside the combustion chamber under various engine load conditions and were able to determine the internal exhaust gas recirculation (EGR) ratio. This measurement technique proved to be valuable in obtaining the cycle-to-cycle CO2 concentration of the residual gas in a heavy-duty diesel engine. © 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved. Source

Yamaguchi T.,New ACE Institute Company Ltd
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B | Year: 2010

The premixed charge compression ignition combustion (PCCI) can reduce NOx and Smoke simultaneously. And it is one of the strategies to improve exhaust emissions at light load in a diesel engine. In this study, the effect of the injection pressure and the swirl ratio on exhaust gas emissions of PCCI was investigated. And also the effect of ignition timing on pressure rise rate of PCCI was investigated. The experimental results show that the combination of high injection pressure and low swirl ratio is effective to improve exhaust emissions of PCCI. Also, the pressure rise rate of PCCI can be decreased by ignition timing retard without the remarkable deterioration of fuel consumption. Source

Uchida N.,New ACE Institute Company Ltd | Sakata I.,Toyota Motor Corporation | Kitano K.,Toyota Motor Corporation | Okabe N.,Royal Dutch Shell | Sakamoto Y.,Royal Dutch Shell
International Journal of Engine Research | Year: 2014

In recent years, paraffinic fuels have attracted attention because of their potential for reducing diesel exhaust emissions, mainly smoke or particulate matter emissions. One of the paraffinic fuels, a Fischer-Tropsch diesel fuel, was selected to demonstrate the lower exhaust emissions while improving fuel economy in this study. To examine the detailed effects of fuel specifications on diesel combustion and emissions, preliminarily tests for three Fischer-Tropsch fuels and a baseline diesel fuel were carried out with three diesel engines having different engine displacements. In addition, differences in combustion phenomena between Fischer-Tropsch fuels and the baseline diesel fuel were observed by means of a single-cylinder engine with optical access. From these findings, one of the tested engines was modified to improve both exhaust emissions and fuel consumption, simultaneously, dedicated to the use of neat Fischer-Tropsch fuels. The conversion efficiency of an oxides of nitrogen reduction catalyst has also been improved. The desirable properties of Fischer-Tropsch fuels for diesel combustion, namely high cetane number and absence of poly-aromatic hydrocarbon contents, have been fully utilized to enhance the conventional diesel combustion limits to show the possibility to achieve very low exhaust emissions with substantial improvement in fuel economy. The results of this study indicate not only the superior emission characteristics of the Fischer-Tropsch fuels, but also evidence that higher exhaust gas recirculation and lower excess air ratios will be a key concept of both engine and aftertreatment optimization for further fuel consumption improvement. © 2012 IMechE. Source

Okamoto T.,New ACE Institute Company Ltd | Uchida N.,New ACE Institute Company Ltd
SAE International Journal of Engines | Year: 2016

To overcome the trade-offs of thermal efficiency with energy loss and exhaust emissions typical of conventional diesel engines, a new diffusion-combustion-based concept with multiple fuel injectors has been developed. This engine employs neither low temperature combustion nor homogeneous charge compression ignition combustion. One injector was mounted vertically at the cylinder center like in a conventional direct injection diesel engine, and two additional injectors were slant-mounted at the piston cavity circumference. The sprays from the side injectors were directed along the swirl direction to prevent both spray interference and spray impingement on the cavity wall, while improving air utilization near the center of the cavity. Results obtained with a heavy-duty single cylinder engine equipped with multiple injectors indicated that it was possible to achieve the desired heat release rate profile by independent control of injection timing and duration (fuel injection pressure was kept in constant) for each fuel injector. Furthermore, smoke emissions were reduced by improved in-cylinder air utilization, which was possible through a different air-fuel mixture formation process than that found in conventional single-injector diesel engines. Results showed reduced friction loss, heat loss and NOx (nitrogen oxides) emissions, while maintaining indicated thermal efficiency by suppressing the peak cylinder pressure, bulk average temperature, and spray flame impingement to the cavity wall. Additionally, a simultaneous reduction in smoke and NOx emissions was achieved, without any deterioration in CO (carbon monoxide) and THC (total hydrocarbon) emissions, even compared with conventional diesel combustion. “CONVERGE” three-dimensional numerical simulation results also suggested that rapid homogenization of local equivalence ratio by improved mixture formation could result in the simultaneous reduction of smoke and NOx emissions, even with EGR. Copyright © 2016 SAE International. Source

Yamaguchi T.,Kurume Institute of Technology | Aoyagi Y.,New ACE Institute Company Ltd | Osada H.,New ACE Institute Company Ltd | Shimada K.,New ACE Institute Company Ltd | Uchida N.,New ACE Institute Company Ltd
SAE International Journal of Engines | Year: 2013

In heavy duty diesel engines, waste heat recovery systems are remarkable means for fuel consumption improvement. In this paper, Diesel-Rankine combined cycle which is combined diesel cycle with Rankine cycle is studied to clarify the quantitative potential of fuel consumption improvement with a high EGR rate and high boosted diesel engine. The high EGR rate and high boosted diesel engine of a single cylinder research engine was used and it reaches brake specific fuel consumption (BSFC) of 193.3 g/kWh at full load (BMEP=2.0MPa). And its exhaust temperature reaches 370 C. The exhaust gas temperature does not exceed 400 C in high boosted diesel engine even at full load operating condition because of a high excess air ratio. On the other hand, exhaust gas quantity is larger due to a high boosting. So, it is estimated that the thermal energy of exhaust gas is enough for recovery in the high boosted diesel engine, although exhaust gas temperature is not so higher than that of an ordinary diesel engine. In the heat balance of the high boosted research diesel engine at medium engine speed, the exhaust loss is 38 % at full load. From this result, it is possible to recover the exhaust gas energy, when engine is operated above medium load condition. In this predictive study, water, methanol, toluene, HCFC-123, R134a and R245fa are compared as working fluid in Rankine cycle with superheating. As a result of this study, it is found that Diesel-Rankine combined cycle has a potential to improve BSFC for 2.6 - 3.0 % at full load condition. Copyright © 2013 SAE International. Source

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