A combination of electric supercharger and Miller Cycle in a gasoline engine to improve thermal efficiency without performance degradation

This contribution is focused on the fuel economy improvement of the Miller cycle under part-load characteristics on a supercharged DI (Direct Injection) gasoline engine. Firstly, based on the engine bench test, the effects with the Miller cycle application under 3000 rpm were studied. The results show that the Miller cycle has different extents of improvement on pumping loss, combustion and friction loss. For low, medium and high loads, the brake thermal efficiency of the baseline engine is increased by 2.8%, 2.5% and 2.6%, respectively. Besides, the baseline variable valve timing (VVT) is optimized by the test. Subsequently, the 1D CFD (Computational Fluid Dynamics) model of the Miller cycle engine after the test optimization at the working condition of 3000 rpm and BMEP (Brake Mean Effective Pressure) = 10 bar was established, and the influence of the combined change of intake and exhaust valve timing on Miller cycle was studied by simulation. The results show that as the effect of the Miller cycle deepens, the engine’s knocking tendency decreases, so the ignition timing can be further advanced, and the economy of the engine can be improved. Compared with the brake thermal efficiency of the baseline engine, the final result after simulation optimization is increased from 34.6% to 35.6%, which is an improvement of 2.9%.

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Nissan gasoline engine strategy for higher thermal efficiency

Combustion Engines ◽

10.19206/ce-2017-225 ◽

2017 ◽

Vol 169 (2) ◽

pp. 141-145 ◽

Cited By ~ 1

Author(s):

Hideaki MIZUNO

Keyword(s):

Heat Capacity ◽

Energy Loss ◽

Compression Ratio ◽

Thermal Efficiency ◽

Gasoline Engine ◽

Loss Reduction ◽

Miller Cycle ◽

High Compression Ratio ◽

Gasoline Engines ◽

Evolution Trend

Rising highly concern about the environment has led to demands for the improvement of the efficiency of gasoline engines. Engine thermal efficiency will reach about 40% by technologies as boosted EGR, miller cycle and so on. This evolution trend will be continuously required to survive engines for the future. In this background, further improvement based on theoretical thermal efficiency of high compression ratio and specific heat capacity should be promoted. In addition, energy loss reduction such as represented by cooling loss and friction is also very important for the efficient and effective improvement. NISSAN’s challenges will be introduced to solve these propositions.

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A Theoretical Study on the Thermodynamic Cycle of Concept Engine with Miller Cycle

Processes ◽

10.3390/pr9061051 ◽

2021 ◽

Vol 9 (6) ◽

pp. 1051

Author(s):

Jungmo Oh ◽

Kichol Noh ◽

Changhee Lee

Keyword(s):

Compression Ratio ◽

Thermal Efficiency ◽

Engine Performance ◽

Thermodynamic Cycle ◽

Expansion Ratio ◽

Boost Pressure ◽

Miller Cycle ◽

Compression Pressure ◽

Air Mass ◽

Atkinson Cycle

The Atkinson cycle, where expansion ratio is higher than the compression ratio, is one of the methods used to improve thermal efficiency of engines. Miller improved the Atkinson cycle by controlling the intake- or exhaust-valve closing timing, a technique which is called the Miller cycle. The Otto–Miller cycle can improve thermal efficiency and reduce NOx emission by reducing compression work; however, it must compensate for the compression pressure and maintain the intake air mass through an effective compression ratio or turbocharge. Hence, we performed thermodynamic cycle analysis with changes in the intake-valve closing timing for the Otto–Miller cycle and evaluated the engine performance and Miller timing through the resulting problems and solutions. When only the compression ratio was compensated, the theoretical thermal efficiency of the Otto–Miller cycle improved by approximately 18.8% compared to that of the Otto cycle. In terms of thermal efficiency, it is more advantageous to compensate only the compression ratio; however, when considering the output of the engine, it is advantageous to also compensate the boost pressure to maintain the intake air mass flow rate.

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Development of High Efficiency Gasoline Engine with Thermal Efficiency over 42%

10.4271/2017-01-2229 ◽

2017 ◽

Cited By ~ 11

Author(s):

Byeongsoek Lee ◽

Heechang Oh ◽

SeungKook Han ◽

SooHyung Woo ◽

JinWook Son

Keyword(s):

Thermal Efficiency ◽

High Efficiency ◽

Gasoline Engine

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The miller cycle gasoline engine for a light duty truck Naoharu Ueda, Hiroshi Sakai (University of Tokyo), Junso Sasaki, Naohide Iso (Mazda Corporation)

JSAE Review ◽

10.1016/s0389-4304(96)80593-5 ◽

1996 ◽

Vol 17 (4) ◽

pp. 445

Keyword(s):

Gasoline Engine ◽

Miller Cycle ◽

Light Duty ◽

Light Duty Truck

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Experimental Study on the Combustion Process and Performance of Diesel Engines Fueled by Emulsion Diesel With Novel Organic Additives

Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology ◽

10.1115/ht2013-17725 ◽

2013 ◽

Cited By ~ 1

Author(s):

Wenming Yang ◽

Hui An ◽

Jing Li ◽

Amin Maghbouli ◽

Kian Jon Chua

Keyword(s):

Diesel Engine ◽

Diesel Engines ◽

Thermal Efficiency ◽

Gasoline Engine ◽

Combustion Process ◽

Nox Emissions ◽

Organic Additives ◽

Oil Droplets ◽

And Performance ◽

One Year

Transportation is one of the major contributors to the world’s energy consumption and greenhouse gases emissions. The need for increased efficiency has placed diesel engine in the spotlight due to its superior thermal efficiency and fuel economy over gasoline engine. However, diesel engines also face the major disadvantage of increased NOx emissions. To address this issue, three types of emulsion fuels with different water concentrations (5%, 10% and 15% mass water) are produced and tested. Novel organic materials (glycerin and ployethoxy-ester) are added in the fuel to provide extra oxygen for improving combustion. NP-15 is added as surfactant which can help to reduce the oil and water surface tension, activates their surface, and maximizes their superficial contact areas, thereby forming a continuous and finely dispersed droplets phase. The stability of the emulsion fuels is tested under various environmental temperature for one year, and no significant separation is observed. It is better than normal emulsion fuel which can only maintain the state for up to three months. The combustion process and performance of the emulsion fuels are tested in a four-stroke, four cylinder diesel engine. The results indicate that the water droplets enclosed in the emulsion fuel explode at high temperature environment and help to break up the big oil droplets into smaller ones, thereby significantly increase the surface area of the oil droplets and enhance the heat transfer from hot gas to the fuel. As a result, the fuel evaporation is improved and the combustion process is accelerated, leading to an improved brake thermal efficiency (up to 14.2%). Meanwhile, the presence of the water causes the peak temperature of the flame to drop, thereby significantly bringing down the NOx emissions by more than 30%.

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