scholarly journals Miller Cycle Analysis Using EGM

2005 ◽  
Author(s):  
Bernardo Ribeiro ◽  
Jorge Martins
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Compression Ratio ◽  
Internal Combustion Engines ◽  
Combustion Engines ◽  
Miller Cycle ◽  
Valve Timing ◽  
Entropy Generation Minimization ◽  
Flow And Heat Transfer ◽  
Variable Valve

The Entropy Generation Minimization (EGM) method is based on the analysis by three sciences (thermodynamics, fluid flow and heat transfer) of the different processes that may occur in a system or in an equipment. Herein the EGM method is applied to internal combustion engines to determine the entropy generation caused by different processes. A model incorporating entropy generation calculations is used to assess various engines configurations. Otto cycle was tested and Variable Valve Timing (VVT) and Variable Compression Ratio (VCR) were applied so thermodynamic benefits could be tested and evaluated. With the referred model, the Miller cycle variables are analyzed in order to establish the best working conditions of an engine under a certain load. The intake and exhaust valve timing, combustion start, compression ratio adjustment and heat transfer are the variables for which a best working condition is determined based on the minimization of the entropy generation of the several engine processes.

scholarly journals Computational studies of the influence of variable valve timing on the performance of a gas engine with Miller’s thermodynamic cycle

2021 ◽  
Vol 2061 (1) ◽  
pp. 012066
Author(s):  
K V Milov
Keyword(s):  
Internal Combustion Engines ◽  
Computer Modelling ◽  
Thermodynamic Cycle ◽  
Valve Lift ◽  
Variable Valve Timing ◽  
Miller Cycle ◽  
Valve Timing ◽  
Gas Engine ◽  
Lift Height ◽  
Variable Valve

Abstract Current development trends in the field of internal combustion engines aim at regulating all processes of the engine and individual units. A converted diesel to gas engine with Miller thermodynamic cycle is more energy efficient at partial loads than a gas engine with Otto thermodynamic cycle. The Miller cycle engine with variable valve timing and valve lift has been investigated to improve performance and energy efficiency across the load range. The aim of the work is to study the influence of the displacement of the valve timing phases of the intake and exhaust camshafts and the valve lift height on the performance of the gas engine with the Miller cycle. Computer modelling was based on data obtained from the full-scale experiment on the gas engine with the Miller thermodynamic cycle.

Effects of Supercharging, EGR and Variable Valve Timing on Power and Emissions of Hydrogen Internal Combustion Engines

2008 ◽  
Vol 1 (1) ◽  
pp. 647-656 ◽  
Author(s):  
Sebastian Verhelst ◽  
Jannick De Landtsheere ◽  
Frederik De Smet ◽  
Christophe Billiouw ◽  
Arne Trenson ◽  
...  
Keyword(s):  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Variable Valve Timing ◽  
Combustion Engines ◽  
Valve Timing ◽  
Variable Valve

Variable Valve-Timing Unit Suitable for Internal Combustion Engines

1972 ◽  
Vol 186 (1) ◽  
pp. 301-306 ◽  
Author(s):  
G. E. Roe
Keyword(s):  
Internal Combustion Engines ◽  
Engine Speed ◽  
Valve Lift ◽  
Specific Power ◽  
Combustion Engines ◽  
Valve Timing ◽  
Specific Power Output ◽  
Torque Curve ◽  
Lift Curve ◽  
Variable Valve

As the specific power output of I.C. engines is increased, the range of engine speed over which useful torque is available is reduced. This ‘power band’ can be widened by having automatically varying valve timing, with the timing being a function of engine speed and/or load. A prototype cyclic phasing unit has been tested which successfully varies the timing of a poppet valve with opening, closing points, and the form of valve lift curve being readily varied independently. The unit is simple mechanically, but ideally one unit is needed for each valve, so principal application is likely to be on engines with a small number of cylinders. In addition to flattening the torque curve, such a unit is likely to give improved fuel consumption and lower exhaust emissions, particularly hydrocarbons.

Optimization of Pin-Fins for a Heat Exchanger by Entropy Generation Minimization and Constructal Law

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Gongnan Xie ◽  
Yidan Song ◽  
Masoud Asadi ◽  
Giulio Lorenzini
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Entropy Generation ◽  
Thermal Energy ◽  
Pin Fin ◽  
Entropy Generation Minimization ◽  
Flow And Heat Transfer ◽  
Constructal Law ◽  
Pin Fins ◽  
Computational Fluid Dynamics Cfd

Pin-fins are considered as one of the best elements for heat transfer enhancement in heat exchangers. In this study, the topology of pin-fins (length, diameter, and shape) is optimized based on the entropy generation minimization (EGM) theory coupled with the constructal law (CL). Such pin-fins are employed in a heat exchanger in a sensible thermal energy storage (TES) system so as to enhance the rate of heat transfer. First, the EGM method is used to obtain the optimal length of pin-fins, and then the CL is applied to get the optimal diameter and shape of pin-fins. Reliable computational fluid dynamics (CFD) simulations of various constructal pin-fin models are performed, and detailed flow and heat transfer characteristics are presented. The results show that by using the proposed system with optimized pin-fin heat exchanger the stored thermal energy can be increased by 10.2%.

NOx and Fuel Economy Challenges With EMD Two-Stroke Engines: Variable Injection and Valve Timing

2009 ◽  
Author(s):  
Michael B. Riley ◽  
John C. Hedrick
Keyword(s):  
Fuel Economy ◽  
Simulation Modeling ◽  
Internal Combustion Engines ◽  
Nox Reduction ◽  
Injection Timing ◽  
Combustion Engines ◽  
Valve Timing ◽  
Start Of Injection ◽  
Variable Valve ◽  
The Impact

NOx emissions are a major cause of ozone formation. Several technologies to mitigate NOx in internal combustion engines have been developed, both in-cylinder and aftertreatment. Some of these newer technologies are being implemented on new engines, but older engines, especially large diesel engines, have few options to reduce these emissions substantially. The most common method of NOx reduction is retarding the start of injection timing but this has a penalty in fuel economy. A program has been undertaken on an EMD 645E two-stroke diesel engine to combine a simple mechanical system with both retarded and variable start of injection — to mitigate NOx — with variable valve timing to offset the fuel economy penalty. Simulation modeling and on-engine experimentation have been carried out to quantify the extent of the NOx reduction with the impact on fuel economy.

Influence of High-Frequency Gas-Dynamic Unsteadiness on Heat Transfer in Gas Flows of Internal Combustion Engines

2014 ◽  
Vol 698 ◽  
pp. 631-636 ◽  
Author(s):  
L.V. Plotnikov ◽  
B.P. Zhilkin ◽  
Y.M. Brodov
Keyword(s):  
Heat Transfer ◽  
High Frequency ◽  
Internal Combustion Engines ◽  
Rotation Angle ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Gas Flows ◽  
Combustion Engines ◽  
Instantaneous Values ◽  
Crankshaft Rotation

The results of experimental research of the influence of high-frequency gas-dynamical nonstationarity on the intensity of heat transfer in the intake and exhaust tract of piston engines are presented in the article. Experimental setup and methods of the experiments are described in the article. Dependences of instantaneous values of flow velocity and the local heat transfer coefficient in the intake and exhaust tract of the engine from the crankshaft rotation angle are presented in the article.

Entropy generation due to flow and heat transfer in nanofluids

2010 ◽  
Vol 53 (21-22) ◽  
pp. 4757-4767 ◽  
Author(s):  
Pawan K. Singh ◽  
K.B. Anoop ◽  
T. Sundararajan ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Flow And Heat Transfer

Maximum efficiencies for internal combustion engines: Thermodynamic limitations

2017 ◽  
Vol 19 (10) ◽  
pp. 1005-1023 ◽  
Author(s):  
Jerald A Caton
Keyword(s):  
Heat Transfer ◽  
Internal Combustion Engines ◽  
High Efficiency ◽  
Pressure Rise ◽  
Internal Combustion ◽  
Thermodynamic Evaluation ◽  
Combustion Engines ◽  
Automotive Engine ◽  
Specific Heats ◽  
Cycle Simulation

The thermodynamic limitation for the maximum efficiencies of internal combustion engines is an important consideration for the design and development of future engines. Knowing these limits helps direct resources to those areas with the most potential for improvements. Using an engine cycle simulation which includes the first and second laws of thermodynamics, this study has determined the fundamental thermodynamics that are responsible for these limits. This work has considered an automotive engine and has quantified the maximum efficiencies starting with the most ideal conditions. These ideal conditions included no heat losses, no mechanical friction, lean operation, and short burn durations. Then, each of these idealizations is removed in a step-by-step fashion until a configuration that represents current engines is obtained. During this process, a systematic thermodynamic evaluation was completed to determine the fundamental reasons for the limitations of the maximum efficiencies. For the most ideal assumptions, for compression ratios of 20 and 30, the thermal efficiencies were 62.5% and 66.9%, respectively. These limits are largely a result of the combustion irreversibilities. As each of the idealizations is relaxed, the thermal efficiencies continue to decrease. High compression ratios are identified as an important aspect for high-efficiency engines. Cylinder heat transfer was found to be one of the largest impediments to high efficiency. Reducing cylinder heat transfer, however, is difficult and may not result in much direct increases of piston work due to decreases of the ratio of specific heats. Throughout this work, the importance of high values of the ratio of specific heats was identified as important for achieving high thermal efficiencies. Depending on the selection of constraints, different values may be given for the maximum thermal efficiency. These constraints include the allowed values for compression ratio, heat transfer, friction, stoichiometry, cylinder pressure, and pressure rise rate.

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