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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.

Osada H.,New Ace Institute Co Ltd. | Aoyagi Y.,New Ace Institute Co Ltd. | Shimada K.,New Ace Institute Co Ltd. | Goto Y.,National Traffic Safety And Enviro Laboratory | Suzuki H.,National Traffic Safety And Enviro Laboratory
SAE Technical Papers | Year: 2010

For reducing NOx emissions, EGR is effective, but an excessive EGR rate causes the deterioration of smoke emission. Here, we have defined the EGR rate before the smoke emission deterioration while the EGR rate is increasing as the limiting EGR rate. In this study, the high rate of EGR is demonstrated to reduce BSNOx. The adapted methods are a high fuel injection pressure such as 200 MPa, a high boost pressure as 451.3 kPa at 2 MPa BMEP, and the air intake port that maintains a high air flow rate so as to achieve low exhaust emissions. Furthermore, for withstanding 2 MPa BMEP of engine load and high boosting, a ductile cast iron (FCD) piston was used. As the final effect, the installations of the new air intake port increased the limiting EGR rate by 5%, and fuel injection pressure of 200 MPa raised the limiting EGR rate by an additional 5%. By the demonstration of increasing boost pressure to 450 kPa from 400 kPa, the limiting EGR rate was achieved to 50%. At the same time, BSNOx was reduced to 1.0 g/kWh from 3.5 g/kWh at 2 MPa BMEP with no increase in smoke emission and particulate matter (PM). The technologies developed in this study are not only to reduce exhaust emissions but also useful and available to improve brake-specific fuel consumption for both single-cylinder and multi-cylinder heavy duty diesel engines. Copyright © 2010 SAE International.

Hashimoto M.,New A.C.E. Institute Co. | Aoyagi Y.,New A.C.E. Institute Co. | Kobayashi M.,New A.C.E. Institute Co. | Murayama T.,New A.C.E. Institute Co. | And 2 more authors.
SAE Technical Papers | Year: 2012

Reduction of exhaust emissions and BSFC has been studied using a high boost, a wide range and high-rate EGR in a Super Clean Diesel, six-cylinder heavy duty engine. In the previous single-turbocharging system, the turbocharger was selected to yield maximum torque and power. The selected turbocharger was designed for high boosting, with maximum pressure of about twice that of the current one, using a titanium compressor. However, an important issue arose in this system: avoidance of high boosting at low engine speed. A sequential and series turbo system was proposed to improve the torque at low engine speeds. This turbo system has two turbochargers of different sizes with variable geometry turbines. At low engine speed, the small turbocharger performs most of the work. At medium engine speed, the small turbocharger and large turbocharger mainly work in series. At high engine speed, the small turbocharger does no work at all, but the large turbocharger works mainly using a small turbocharger bypass. The basic engine, with six cylinders in-line and displacement of 10.5 L, is equipped with a high-pressure fuel injection system and a high- and low-pressure loop EGR system for using the high boosting and high EGR rate to reduce BSNOx and PM. Experimentally obtained results show that the sequential and series turbocharging system has 50% higher torque than the conventional, with improved fuel consumption achieved in the low-speed region. Copyright © 2012 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.

Uchida N.,New A.C.E Institute Co. | Fukunaga A.,New A.C.E Institute Co. | Osada H.,New A.C.E Institute Co. | Shimada K.,New A.C.E Institute Co.
SAE Technical Papers | Year: 2014

Heat loss reduction could be one of the most promising methods of thermal efficiency improvement for modern diesel engines. However, it is difficult to fully transform the available energy derived from a reduction of in-cylinder heat loss into shaft work, but it is rather more readily converted into higher exhaust heat loss. It may therefore be favorable to increase the effective expansion ratio of the engine, thereby maximizing the brake work, by transforming more of the enthalpy otherwise remaining at exhaust valve opening (EVO) into work. In general, the geometric compression ratio of a piston cylinder arrangement has to increase in order to achieve a higher expansion ratio, which is equal to a higher thermodynamic compression ratio. It is still necessary to overcome constraints on peak cylinder pressure, and other drawbacks, before applying higher expansion ratios to current high-boost, high brake mean effective pressure (BMEP), and high exhaust gas recirculation (EGR) diesel engines. The purpose of this study was to clarify the possibility of improving the thermal efficiency of a diesel engine by variable valve timing strategies. Experiments were performed on a single-cylinder heavy duty diesel engine equipped with external supercharging system, using various combinations of effective compression and expansion ratios. Results confirmed that improvement in the gross-indicated thermal efficiency was achieved by increasing the effective expansion ratio at a fixed and relatively lower effective compression ratio (compared to expansion ratio.) The gross-indicated thermal efficiency was calculated based on the cycle work by in-cylinder pressure and volume traces only during compression and expansion strokes. The brake thermal efficiency was further improved using a piston cavity having higher geometric compression ratio than the baseline value of 18.0. Copyright © 2014 SAE International.

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