scholarly journals Numerical investigation of Miller cycle with EIVC and LIVC on a high compression ratio gasoline engine

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110236
Author(s):  
Jiangtao Xu ◽  
Tongjun Guo ◽  
Yong Feng ◽  
Mengxin Sun
Keyword(s):  
Compression Ratio ◽  
Gasoline Engine ◽  
Engine Performance ◽  
High Load ◽  
Total Power ◽  
Miller Cycle ◽  
Indicated Mean Effective Pressure ◽  
Working Cycle ◽  
Total Power Consumption ◽  
Engine Knock

Previous studies have shown that increase compression ratio (CR) is an effective way to improve thermal efficiency of gasoline engine without changing the mechanical structure and working cycle, however, it is limited by engine knock when increasing the intake boosting under high load operation. This study aimed to solve the knock problem of gasoline engine with higher CR by application of Miller cycle, which can be implemented by either early or late intake valve closing (EIVC or LIVC). Therefore, in this paper, based on the engine with CR of 13.5 and electromagnetic valves train (EMVT), a comparative study was carried out to investigate the effects of EIVC and LIVC on engine performance, by theoretical modeling and calculation. The results show that, at high load, EIVC strategy is more preferred than LIVC owing to its lower total power consumption, which can improve the indicated mean effective pressure (IMEP) by 0.0371 bar, while enhance turbulence intensity and improve combustion. And at part load, the advantage for EIVC declines gradually, nevertheless, it can still sensitively adjust the EGR rate and thus reduce NOx. This results of quantitative analysis about two Miller cycles can provide valuable reference for engine designers and researchers.

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

Processes ◽  
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.

Application of Over-Expansion Cycle to a Larger Gasoline Engine With Late-Closing of Intake Valves

2002 ◽  
Author(s):  
Seiichi Shiga ◽  
Kenji Nishida ◽  
Shizuo Yagi ◽  
Youichi Miyashita ◽  
Yoshiharu Yuzawa ◽  
...  
Keyword(s):  
Compression Ratio ◽  
Thermal Efficiency ◽  
Gasoline Engine ◽  
Engine Performance ◽  
Mechanical Efficiency ◽  
Expansion Ratio ◽  
Brake Thermal Efficiency ◽  
Gasoline Engines ◽  
Cylinder Test ◽  
Test Engine

This paper presents further investigation into the effect of over-expansion cycle with late-closing of intake valves on the engine performance in gasoline engines. A larger single-cylinder test engine with the stroke volume of 650 cc was used with four kinds of expansion ratio (geometrical compression ratio) from 10 to 25 and four sets of intake valve closure (I.V.C.) timings from 0 to 110 deg C.A. ABDC. Late-closing has an effect of decreasing the pumping work due to the reduction of intake vacuum, althogh higher expansion ratio increases the friction work due to the average cylinder pressure level. Combining the higher expansion ratio with the late-closing determines the mechanical efficiency on the basis of these two contrastive effects. The indicated thermal efficiency is mostly determined by the expansion ratio and little affected by the nominal compression ratio. The value of the indicated thermal efficiency reaches to 48% at most which is almost comparable with the value of diesel engines. The improvement of both indicated and brake thermal efficiency reaches to 16% which is much higher than ever reported by the authors. A simple thermodynamic calculation could successfully explain the behavior of the indicated thermal efficiency. The brake thermal efficiency could also be improved due to the increase in both mechanical and indicated efficiencies.

scholarly journals Influence of Compression Ratio on Flywheel Dimension for a Naturally Aspirated Spark Ignition Engine: A Numerical Study

2020 ◽  
Vol 3 (2) ◽  
Author(s):  
Aan Yudianto ◽  
Peixuan Li
Keyword(s):  
Compression Ratio ◽  
Numerical Study ◽  
Engine Performance ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Effective Pressure ◽  
Si Engine ◽  
Compression Stroke ◽  
Indicated Mean Effective Pressure ◽  
Proper Design

The proper design of the flywheel undeniably determines in tuning the engine to confirm the better output engine performance. The aim of this study is to mathematically investigate the effect of various values of the compression ratio on some essential parameters to determine the appropriate value for the flywheel dimension. A numerical calculation approach was proposed to eventually determine the dimension of the engine flywheel on a five-cylinder four-stroke Spark Ignition (SI) engine. The various compression ratios of 8.5, 9, 9.5, 10, 10.5, and 11 were selected to perform the calculations. The effects of compression ratio on effective pressure, indicated mean effective pressure (IMEP), dynamic irregularity value of the crankshaft, and the diameter of the flywheel was clearly investigated. The study found that 2.5 increment value of the compression ratio significantly increases the effective pressure of about 41.53% on the starting of the expansion stroke. While at the end of the compression stroke, the rise of effective pressure is about 76.67%, and the changes in dynamic irregularity merely increase by about 1.79%. The same trend applies to the flywheel diameter and width, which increases 2.08% for both.

Simulation on Effect of EGR on Oxy-Fuel IC Engine

2011 ◽  
Vol 130-134 ◽  
pp. 790-795 ◽  
Author(s):  
Xiao Yu ◽  
Zhi Jun Wu
Keyword(s):  
Reaction Rate ◽  
Gasoline Engine ◽  
Water Injection ◽  
Combustion Process ◽  
Engine Performance ◽  
Rankine Cycle ◽  
Ic Engine ◽  
Injection Process ◽  
Working Cycle ◽  
Exhaust Heat

Internal combustion Rankine cycle engine uses oxygen instead of air as oxidant during the combustion process in gasoline engine. Recycled fluid is employed to control the reaction rate and recycles the exhaust heat inside the cylinder as well. CO2 could be recaptured after separated from the exhaust gas (CO2 and water vapor) during condensation, and an ultra-low emission working cycle is achieved. Considering the side effects of water injection process, EGR is employed to control the combustion process and thermal efficiency of the oxy-fuel combustion cycle is calculated and optimized in this paper. Results show that the application of EGR could slow down the combustion process effectively, and appropriate EGR rate matched with ignition timing would control the reaction rate and cylinder pressure, therefore enhance the engine performance.

Effects of applying a Miller cycle with split injection on engine performance and knock resistance in a downsized gasoline engine

Fuel ◽  
2018 ◽  
Vol 214 ◽  
pp. 98-107 ◽  
Author(s):  
Haiqiao Wei ◽  
Aifang Shao ◽  
Jianxiong Hua ◽  
Lei Zhou ◽  
Dengquan Feng
Keyword(s):  
Gasoline Engine ◽  
Engine Performance ◽  
Miller Cycle ◽  
Split Injection

Study of Combustion and Emission Characteristics of Gasoline Engine with Miller Cycle

2014 ◽  
Vol 960-961 ◽  
pp. 1411-1415 ◽  
Author(s):  
Jian Wu ◽  
Wei Fan ◽  
Yang Hua ◽  
Yun Long Li ◽  
Shao Zhe Zhang ◽  
...  
Keyword(s):  
Heat Release ◽  
Compression Ratio ◽  
Gasoline Engine ◽  
Control Technology ◽  
Miller Cycle ◽  
High Compression Ratio ◽  
Combustion Heat ◽  
Geometry Compression ◽  
Cam Profile ◽  
Hc Emissions

On the basis of original engine, high compression ratio miller cycle can be realized, through perfecting the inlet cam profile, using higher geometry compression ratio, combining VVT control technology. The results indicate that the miller cycle achieved by VVT control technology can reduce pumping loss, and improve the effect utilization of energy. The combustion heat release rate is lower than the original engine, and combustion heat release are mainly concentrated on TDC later, lower the burning temperature. Compared with the original engine, NOX emissions decrease significantly, but CO and HC emissions increase somewhat.

scholarly journals Influence of Ethanol-Gasoline Fuel Fractions on Variable Compression Ratio Engine

2019 ◽  
Vol 8 (3) ◽  
pp. 2929-2936
Keyword(s):  
Compression Ratio ◽  
Gasoline Engine ◽  
Engine Performance ◽  
Calorific Value ◽  
Mechanical Efficiency ◽  
Spark Ignition Engine ◽  
Brake Thermal Efficiency ◽  
Variable Compression Ratio Engine ◽  
Power Outputs ◽  
Fuel Fraction

Increase in demand of ethanol as blending fuel with gasoline is increasing. For noting the performance of the engine, experimentations are required to be done on engine, fuelled with various percentages of ethanol in gasoline. In this study, fuel fractions of ethanol and gasoline were taken for observing the performance of spark ignition engine. One-cylinder gasoline engine was used for conducting the experiments and to analyse the effects of ethanol-gasoline fuel fraction on performance of the engine. The engine was tested at Full Open Throttle condition. The load on the engine was changed by changing the load on Eddy Current Dynamometer to vary the engine speed from 1300 to 1700 rpm in the interval of 100 rpm. Gasoline is blended with ethanol to make five fuel fractions from 0 % ethanol (E0) to 40 % ethanol (E40) in gasoline at the interval of 10% by volume. Engine performance was observed at various Compression Ratio (CR) of the engine as 7,8,9 and 10. Calorific Value (CV) of the fuel fractions observed decreasing from E0 to E40 as CV of ethanol is less than base gasoline. Increase in Brake Specific Fuel Consumption was not very significant with rise in ethanol percentage. Power outputs in terms of Brake Power (BP) was increasing with increase in speed of the engine and observed decreasing with increase in ethanol percentage at constant CR. However various engine output parameters like BP, Mechanical Efficiency found decreasing with increase in fuel fractions ratio. Brake Thermal Efficiency (BTE) was observed decreasing with increase in fuel fractions. However, BTE was observed increasing with increase in CR.

Sign in / Sign up

Export Citation Format

Share Document