New ACE Institute Company Ltd

Tsukuba, Japan

New ACE Institute Company Ltd

Tsukuba, Japan
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Kamimoto T.,Tokyo Institute of Technology | Uchida N.,New ACE Institute Co. | Aizawa T.,Meiji University | Kondo K.,Meiji University | Kuboyama T.,Chiba University
International Journal of Engine Research | Year: 2017

This study concerns a quantitative analysis of late-cycle soot oxidation in diesel engines that focuses on two-dimensional KL factor images obtained by the two-color method. The spatially integrated KL factor was converted into the in-cylinder soot mass using a new formula of diesel soot emissivity. This methodology was applied to two combustion systems: a heavy-duty optical engine which was tuned for a higher fuel-air mixing capability and a rapid compression and expansion machine which had a lower mixing performance. The in-cylinder soot mass history during the last stage of soot oxidation phase was converted into a normalized soot mass history and was used for comparison with simulated soot mass history. A model calculation of in-cylinder soot mass history which was based on oxidation of a primary soot particle was performed with the surface-specific soot oxidation rate as a parameter. A value of the surface-specific soot oxidation rate was specified from the curve fitting approach between the experimental and simulated in-cylinder soot mass traces. The resultant soot oxidation rates plotted on the Arrhenius diagram were found to lie in domains with different oxidation mechanisms. The reason for the scattered plots was discussed referring to model predictions of soot oxidation in the literature, and it was concluded that the higher oxidation rates could be attributed to well-mixed soot oxidizer structure. © 2016 IMechE.

Uchida N.,New ACE Institute Co. | Osada H.,New ACE Institute Co.
SAE International Journal of Engines | Year: 2017

To reduce heat transfer between hot gas and cavity wall, thin Zirconia (ZrO2) layer (0.5mm) on the cavity surface of a forged steel piston was firstly formed by thermal spray coating aiming higher surface temperature swing precisely synchronized with flame temperature near the wall resulting in the reduction of temperature difference. However, no apparent difference in the heat loss was analyzed. To find out the reason why the heat loss was not so improved, direct observation of flame impingement to the cavity wall was carried out with the top view visualization technique, for which one of the exhaust valves was modified to a sapphire window. Local flame behavior very close to the wall was compared by macrophotography. Numerical analysis by utilizing a three-dimensional simulation was also carried out to investigate the effect of several parameters on the heat transfer coefficient. From the observation of wall impinged flame, it was revealed that a kind of thermal boundary layer with Zirconia coating was thinner than the baseline, which could be resulted in the increase in heat transfer coefficient. Furthermore, the numerical simulation results suggested that higher wall surface temperature swing with Zirconia coating is not the main cause of thinner boundary layer, but surface roughness and/or porous structure is. To confirm the hypothesis, new pistons with different insulating structures were then experimented. Even though the heat loss was not so improved because of the limited area of insulation, the potential for BTE improvement was confirmed. Copyright © 2017 SAE International.

Osada H.,New A.C.E. Institute Co. | Uchida N.,New A.C.E. Institute Co. | Zama Y.,Gunma University
SAE Technical Papers | Year: 2015

Impingement of a spray flame on the periphery of the piston cavity strongly affects heat loss to the wall. The heat release rate history is also closely correlated with the indicated thermal efficiency. For further thermal efficiency improvement, it is thus necessary to understand such phenomena in state of the art diesel engines, by observation of the actual behavior of an impinging spray flame and measurement of the local temperature and flow velocity. A top-view optically accessible engine system, for which flame impingement to the cavity wall can be observed from the top (vertically), was equipped with a high speed digital camera for direct observation. Once the flame impinged on the wall, flame tip temperature decreased roughly 100K, compared to the temperature before impingement. With higher injection pressure, local flame speed, as determined by the PIV technique was almost the same as that determined by numerical simulation, whereas flame temperature near the wall analyzed by the two-color method showed a relatively smaller increase than the numerical results. The experiment was also carried out with zirconia coated combustion chamber, which resulted in a 100 K lower flame tip temperature drop than the baseline steel piston did, in the impingement region. © 2015 SAE Japan.

Aoyagi Y.,New ACE Institute Company Ltd | Yamaguchi T.,New ACE Institute Company Ltd | Osada H.,New ACE Institute Company Ltd | Shimada K.,New ACE Institute Company Ltd | And 2 more authors.
International Journal of Engine Research | Year: 2011

The combination of high boosting and high exhaust gas recirculation (EGR) is a practical and effective strategy to achieve simultaneous reductions of fuel consumption and exhaust emissions in diesel engines. To obtain further improvements of fuel efficiency and emissions, the effects of engine parameters including compression ratio, peak cylinder pressure, and the timing of the start of combustion are investigated using a single-cylinder diesel engine under conditions of high boost pressure of 400 kPa and fuel injection pressure of 200 MPa, focusing particularly on the peak cylinder pressure. The experiments show that when the peak cylinder pressure is raised to 28MPa by adjusting the timing of the start of combustion at -3°after top dead centre (ATDC) at a compression ratio of 18, the lowest specific fuel consumption rate of 185.6 g/kW h, which corresponds to the brake thermal efficiency of 45.2 per cent, is obtained. When the effective compression ratio is lowered by using a variable valve timing system while maintaining the peak cylinder pressure at 28 MPa, the minimum specific fuel consumption of 181.2 g/kW h, which corresponds to a brake thermal efficiency of 46.3 per cent, is obtained. © Authors 2011.

Kobayashi M.,New Ace Institute Co. | Aoyagi Y.,New Ace Institute Co. | Adachi T.,New Ace Institute Co. | Murayama T.,New Ace Institute Co. | And 3 more authors.
SAE Technical Papers | Year: 2011

Reduction of exhaust emissions and BSFC was studied for high pressure, wide range, and high EGR rates in a Super-clean Diesel six-cylinder heavy duty engine. The GVW 25-ton vehicle has 10.52 L engine displacement, with maximum power of 300 kW and maximum torque of 1842 Nm. The engine is equipped with high-pressure fuel injection of a 200 MPa level common-rail system. A variable geometry turbocharger (VGT) was newly designed. The maximum pressure ratio of the compressor is about twice that of the previous design: 2.5. Additionally, wide range and a high EGR rate are achieved by high pressure-loop EGR (HP-EGR) and low pressure-loop EGR (LP-EGR) with described VGT and high-pressure fuel injection. The HP-EGR can reduce NOx concentrations in the exhaust pipe, but the high EGR rate worsens smoke. The HP-EGR system layout has an important shortcoming: it has great differences of the intake EGR gas amount into each cylinder, worsens smoke. The system layout can eliminate large differences of intake EGR gas amounts into each cylinder. The improved HP-EGR system layout achieves a wide range and high EGR more than the previous system. For engine speed of 1200 rpm and 40% load (BMEP0.83 MPa), the combined EGR of HP-EGR and LP-EGR can increase about twice EGR rate compared with the case of HP-EGR only and improve NOx to around half without BSFC deterioration. This system was evaluated practically to improve exhaust emissions in both steady-state and transient test conditions. Finally, the super-clean diesel engine is used with this system and checked experimentally using the JE05 transient test mode to meet the target performance. Copyright © 2011 SAE International.

Yamaguchi T.,Kurume Institute of Technology | Aoyagi Y.,New Ace Institute Co Ltd | Osada H.,New Ace Institute Co Ltd | Shimada K.,New Ace Institute Co Ltd | Uchida N.,New Ace Institute Co 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.

Kawahara N.,Okayama University | Tomita E.,Okayama University | Ohtsuki A.,Okayama University | Aoyagi Y.,New A.C.E. Institute CO.
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.

Yamaguchi T.,NEW A. C. E Institute Co.
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.

Osada H.,New Ace Institute Co. | Uchida N.,New Ace Institute Co. | Shimada K.,New Ace Institute Co. | Aoyagi Y.,New Ace Institute Co.
SAE Technical Papers | Year: 2013

As a technology required for future commercial heavy-duty diesel engines, this study reexamines the potential of the multiple injection strategy for improving the thermal efficiency while maintaining low engine-out exhaust emissions with a high EGR rate of more than 50% and high boost pressure of 276.3 kPa abs under medium load conditions. The experiments were conducted with a single cylinder research engine. The engine was operated at BMEP of 0.8 MPa at a medium speed. Using multiple injections, the temporal and spatial in-cylinder temperature distribution was changed to investigate the effect on fuel consumption and exhaust emissions. The results showed that the multiple injection strategy combined with higher EGR rate could improve fuel consumption by about 3% due to the reduction of heat loss from the wall. Combustion visualization analysis and 3D simulation proved that the major factors in reducing the heat loss are optimization of the spatial flame distribution near the wall and reduction of flame temperature by a higher EGR rate. Copyright © 2013 SAE International.

Okamoto T.,New Ace Institute Co. | Uchida N.,New Ace Institute Co.
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.

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