Potential of hydrogen/diesel reactivity controlled compression ignition (RCCI) combustion from the perspective of the second law of thermodynamics

2021 ◽  
pp. 146808742110601
Author(s):  
Ming Jia ◽  
Jinpeng Bai ◽  
Huiquan Duan ◽  
Yaopeng Li ◽  
Yikang Cai ◽  
...  
Keyword(s):  
Combustion Temperature ◽  
Initial Pressure ◽  
Second Law Of Thermodynamics ◽  
Chemical Mechanism ◽  
Energy Ratio ◽  
Second Law ◽  
Compression Ignition ◽  
Exergy Destruction ◽  
Reactivity Controlled Compression Ignition ◽  
Combustion Duration

The potential of reactivity controlled compression ignition (RCCI) combustion fueled with hydrogen and diesel (i.e. hydrogen/diesel RCCI) was evaluated using multi-dimensional simulations embedded with a reduced chemical mechanism. In hydrogen/diesel RCCI, the premixed hydrogen is ignited by the diesel, which is directly injected into the cylinder well before the top dead center. To investigate the potential benefits of hydrogen/diesel RCCI, its combustion characteristics were compared with that of gasoline/diesel RCCI from the perspective of the second law of thermodynamics. Meanwhile, the impacts of premixed energy ratio and initial pressure on the exergy distribution for hydrogen/diesel RCCI were explored. The results show that hydrogen/diesel RCCI has an advantage over gasoline/diesel RCCI in the reduction of exergy destruction due to higher combustion temperature, shorter combustion duration, and the distinctive oxidation pathways between hydrogen and gasoline. A higher proportion of exergy output work can be achieved for hydrogen/diesel RCCI under the conditions with the same total input energy and 50% heat release (CA50) point. Moreover, a larger premixed energy ratio (i.e. larger hydrogen proportion) is helpful to elevate exergy output work and reduce exergy destruction owing to higher combustion temperature and the undergoing oxidation pathways of hydrogen with less exergy destruction. A higher initial pressure yields raised exergy destruction because of lower combustion temperature and longer combustion duration, but exergy output work is increased owing to the significantly reduced exergy transfer through heat transfer.

scholarly journals Effect of Syngas Composition on the Combustion and Emissions Characteristics of a Syngas/Diesel RCCI Engine

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 212 ◽  
Author(s):  
Navid Kousheshi ◽  
Mortaza Yari ◽  
Amin Paykani ◽  
Ali Saberi Mehr ◽  
German F. de la Fuente
Keyword(s):  
Carbon Monoxide ◽  
Combustion Temperature ◽  
Nox Reduction ◽  
Combustion Process ◽  
Compression Ignition ◽  
Exergy Destruction ◽  
Reactivity Controlled Compression Ignition ◽  
Constant Energy ◽  
Gasification Process ◽  
The Impact

Reactivity controlled compression ignition (RCCI) strategy uses two different fuels with different reactivities which provides more control over the combustion process and has the potential to dramatically lower combustion temperature and NOX and PM emissions. The objective of the present study is to numerically investigate the impact of syngas composition on the combustion and emissions characteristics of an RCCI engine operating with syngas/diesel at constant energy per cycle. For this purpose, different syngas compositions produced through gasification process have been chosen for comparison with the simulated syngas (mixture of hydrogen and carbon monoxide). The results obtained indicate that using syngas results in more soot, CO and UHC emissions compared with simulated syngas. Even though more NOX reduction can be achieved while operating with syngas, the engine could suffer from poor combustion and misfire at low loads due to the presence of nitrogen in the mixture. In terms of exergy, both syngas mixtures lead to more exergy destruction by the increase of syngas substitution. Nevertheless, the magnitude of exergy destruction for simulated syngas is less than the normal syngas.

Availability analysis on combustion of n-heptane and isooctane blends in a reactivity controlled compression ignition engine

2017 ◽  
Vol 232 (11) ◽  
pp. 1501-1515 ◽  
Author(s):  
Mostafa Mohebbi ◽  
Masoud Reyhanian ◽  
Iraj Ghofrani ◽  
Azhar Abdul Aziz ◽  
Vahid Hosseini
Keyword(s):  
Heat Transfer ◽  
Mass Fraction ◽  
Fossil Fuels ◽  
Utilization Efficiency ◽  
Second Law ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Reactivity Controlled Compression Ignition ◽  
Fuel Mass ◽  
Availability Analysis

Unfortunately, energy demands and destruction of the environment from uncontrolled manipulation of fossil fuels have increased. Climate change concerns have resulted in the rapid use of new, alternative combustion technologies. In this study, reactivity controlled compression ignition (RCCI) combustion, which can simply be exploited in internal combustion (IC) engines, is investigated. To introduce and identify extra insightful information, an exergy-based study was conducted to classify various irreversibility and loss sources. Multidimensional models were combined with the primary kinetics mechanism to investigate RCCI combustion, incorporating the second law of thermodynamics. The n-heptane, a highly reactive fuel, was supplied by direct injection into the cylinder, whereas premixed fuel was supplied through the intake port in an isooctane/ n-heptane RCCI engine. For five n-heptane increments (5%, 7.5%, 15%, 25%, and 40%) and six different exhaust gas recirculation (EGR) rates (0%, 10%, 20%, 30%, 40%, and 50%), accumulation of different exergy terms was calculated. The results show that as EGR introduction increases from 0% to 50%, the exergy destruction increases from 21.1% to 28.9%. Furthermore, the value of exhaust thermomechanical exergy decreases from 18.4% to 14.4% of the mixture fuel chemical exergy. Among the five different high reactive fuel mass regimes, the 40% n-heptane mass fraction has the major heat transfer exergy owing to its advanced CA50 that exerts a unique influence on cylinder charge temperature of heat transfer layer. The utilization efficiency of exhaust in RCCI is less affected by the variation of reactive fuel mass fraction by contrast; it will significantly influence heat transfer availability. This study revealed that with increasing reactive fuel ( n-heptane) from 7.5% to 40% the irreversibility decreased from 28.6% to 25.8% and the second law efficiency first increased from 43.2% to 44.6% at 15% n-heptane then decreased to 42.9% at 40% n-heptane.

Derivation of Entropy and Exergy Transport Equations, and Application to Second Law Analysis of Sugarcane Bagasse Gasification in Bubbling Fluidized Beds

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Gabriel L. Verissimo ◽  
Manuel E. Cruz ◽  
Albino J. K. Leiroz
Keyword(s):  
Sugarcane Bagasse ◽  
Fluidized Beds ◽  
Chemical Species ◽  
Second Law Of Thermodynamics ◽  
Transport Equations ◽  
Second Law ◽  
Exergy Destruction ◽  
Gasification Process ◽  
Second Law Analysis ◽  
Biomass Particles

Abstract In the present work, the transport equations for mass, momentum, energy, and chemical species as given by the Euler–Euler formulation for multiphase flows are used together with the second law of thermodynamics to derive the entropy and exergy transport equations, suitable to the study of gas-particle reactive flows, such as those observed during pyrolysis, gasification, and combustion of biomass particles. The terms of the derived equations are discussed, and the exergy destruction contributions are identified. Subsequently, a kinetic model is implemented in a computational fluid dynamics (CFD) open source code for the sugarcane bagasse gasification. Then, the derived exergy destruction terms are implemented numerically through user-defined Fortran routines. Next, the second law analysis of the gasification process of sugarcane bagasse in bubbling fluidized beds is carried out. Detailed results are obtained for the local destructions of exergy along the reactor. This information is important to help improve environmental and sustainable practices and should be of interest to both designers and operators of fluidized bed equipment.

scholarly journals EXERGY DESTRUCTION AND CHEMICAL IRREVERSIBILITIES DURING COMBUSTION IN SPARK – IGNITION ENGINE USING OXYGENATED AND HYDROCARBON FUELS

2013 ◽  
pp. 7-11
Author(s):  
MUNAWAR NAWAB KARIMI ◽  
SANDEEP KUMAR KAMBOJ
Keyword(s):  
Combustion Engine ◽  
Second Law Of Thermodynamics ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Second Law ◽  
Exergy Destruction ◽  
Efficient Utilization ◽  
Dead State ◽  
Energy Economy ◽  
Volume Entropy

The growing concern for energy, economy and environment calls for efficient utilization of natural resources in developing useful work. Second law of thermodynamics provides different perspective compared with first law. This paper provides an overview of the quantitative levels of exergy destruction and chemical irreversibilities during the combustion. For the adiabatic combustion at constant volume, entropy generation approach with second law of thermodynamics is applied. The result of this study is based on a spark ignition, single cylinder combustion engine with stoichiometric condition. Iso-octane, methane, methanol and ethanol are the fuels examined. This study shows that exergy destruction during combustion decreases with the increase in reactant temperature and compression ratios, for all the fuels. Exergy destruction during combustion using entropy balance approach for compression ratio range of 7 to 11 found to vary between 16.18 to 21.52%. Chemical irreversibilities calculated at the restricted dead state are found to be in the range of 2.99 to 3.6% for different fuels

scholarly journals Application of Second-Law Analysis for the Environmental Control Unit at High Ambient Temperature

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3274
Author(s):  
Ammar M. Bahman ◽  
Eckhard A. Groll
Keyword(s):  
Ambient Temperature ◽  
Environmental Control ◽  
Control Unit ◽  
Second Law Of Thermodynamics ◽  
High Ambient Temperature ◽  
Second Law ◽  
Potential Contribution ◽  
Exergy Destruction ◽  
Ambient Conditions ◽  
Second Law Analysis

This paper assesses the application of the second-law of thermodynamics in a military Environmental Control Unit (ECU) to evaluate the exergy destruction (or irreversibility) in each component when operating at high ambient temperature. Experimental testings were conducted on three ECUs, 1.5 (5.3 kW), 3 (10.6 kW), and 5 (17.6 kW) tons of refrigeration (RT), to assess the potential contribution of each component to enhance the overall energy efficiency of the system, and to determine the feasibility of the thermodynamic model presented herein. The analysis provided for extreme high ambient conditions up to 51.7 °C (125 °F). The results yielded that the highest irreversibility was associated with compressors (32.4% to 42.5%). This is followed by the heat exchanges (19.6% to 32.9%) in the case of 1.5-RT and 3-RT units, whereas for the 5-RT unit, the highest irreversibility was associated with the evaporator followed by the one of the compressors. In the 3-RT ECU, the condenser’s second-law efficiency enhanced due to an additional fan, yet the working refrigerant increased the irreversibility in the expansion device. The second-law analysis recognized the components with the highest exergy destruction and identified the direction to enhance the exergetic efficiency of any ECU operating at high-temperature climate.

Exergy Analysis of a Solar Heating System

1995 ◽  
Vol 117 (3) ◽  
pp. 249-251 ◽  
Author(s):  
Geng Liu ◽  
Y. A. Cengel ◽  
R. H. Turner
Keyword(s):  
Exergy Analysis ◽  
Energy Analysis ◽  
Second Law Of Thermodynamics ◽  
Heating System ◽  
Solar Heating ◽  
Second Law ◽  
Exergy Destruction ◽  
Thermal Systems ◽  
Heating Systems ◽  
Second Law Analysis

Exergy destruction associated with the operation of a solar heating system is evaluated numerically via an exergy cascade. As expected, exergy destruction is dominated by heat transfer across temperature differences. An energy analysis is also given for comparison of exergy cascade to energy cascade. Efficiencies based on both the first law and second law of thermodynamics are calculated for a number of components and for the system. The results show that high first-law efficiency does not mean high second-law efficiency. Therefore, the second-law analysis has been proven to be a more powerful tool in identifying the site losses. The procedure used to determine total exergy destruction and second law efficiency can be used in a conceptual design and parametric study to evaluate the performance of other solar heating systems and other thermal systems.

scholarly journals Exergy Analysis Using a Theoretical Formulation of a Geothermal Power Plant in Cerro Prieto, México

Entropy ◽  
2021 ◽  
Vol 23 (9) ◽  
pp. 1137
Author(s):  
Dario Colorado-Garrido ◽  
Gerardo Alcalá-Perea ◽  
Francisco Alejandro Alaffita-Hernández ◽  
Beatris Adriana Escobedo-Trujillo
Keyword(s):  
Power Plant ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Exergy Destruction ◽  
Theoretical Formulation ◽  
Geothermal Power Plant ◽  
Single Flash ◽  
Geothermal Power ◽  
Cerro Prieto ◽  
Double Flash

The purpose of this research is the calculation of the exergy destruction of the single-flash and double-flash cycles of a geothermal power plant located on the ladder of the 233 m Cerro Prieto volcano, on the alluvial plain of the Mexicali Valley, Mexico. The methodology developed in this research presents thermodynamic models for energy and exergy flows, which allows determining the contribution of each component to the total exergy destruction of the system. For the case-base, the results indicate that for the single-flash configuration the efficiency of the first and second law of thermodynamics are 0.1888 and 0.3072, as well as the highest contribution to the total exergy destruction is provided by the condenser. For the double-flash configuration, the efficiency of the first and second law of thermodynamics are 0.3643 and 0.4983. The highest contribution to the total exergy destruction is provided by the condenser and followed by the low-pressure turbine.

Thermodynamic Performance Assessment of Gas Turbine Trigeneration System for Combined Heat Cold and Power Production

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Abdul Khaliq ◽  
Rajesh Kumar
Keyword(s):  
Gas Turbine ◽  
Thermal Energy ◽  
Pressure Ratio ◽  
Energy Ratio ◽  
Second Law ◽  
Exergy Destruction ◽  
Thermodynamic Performance ◽  
Second Law Analysis ◽  
Process Heat ◽  
Gas Turbine Cycle

The thermodynamic performance of the combustion gas turbine trigeneration system has been studied based on first law as well as second law analysis. The effects of overall pressure ratio and process heat pressure on fuel utilization efficiency, electrical to thermal energy ratio, second law efficiency, and exergy destruction in each component are examined. Results for gas turbine cycle, cogeneration cycle, and trigeneration cycle are compared. Thermodynamic analysis indicates that maximum exergy is destroyed during the combustion and steam generation process, which represents over 80% of the total exergy destruction in the overall system. The first law efficiency, electrical to thermal energy ratio, and second law efficiency of trigeneration system, cogeneration system, and gas turbine cycle significantly varies with the change in overall pressure ratio but the change in process heat pressure shows small variations in these parameters. Results clearly show that performance evaluation of the trigeneration system based on first law analysis alone is not adequate and hence more meaningful evaluation must include second law analysis.

Multi-objective optimizations of the boot injection strategy for reactivity controlled compression ignition engines

2018 ◽  
Vol 20 (8-9) ◽  
pp. 889-910 ◽  
Author(s):  
Kaveh Yazdani ◽  
Ehsan Amani ◽  
Hamid Naderan
Keyword(s):  
Injection Rate ◽  
Fuel Vapor ◽  
Second Law ◽  
Base Case ◽  
Compression Ignition ◽  
Swirl Ratio ◽  
Shape Parameters ◽  
Compression Ignition Engine ◽  
Reactivity Controlled Compression Ignition ◽  
Multi Objective

In this study, multi-objective optimizations of a reactivity controlled compression ignition engine are performed. The main focus is the investigation of effects of seven design variables, including swirl ratio, the first and second start of injections (SOI1 and SOI2), and four injection rate-shape parameters, on the objective parameters, namely, gross indicated efficiency, the second-law efficiency, ringing intensity, and emissions. The results show that in the low swirl ratio range (swirl ratio < 1), the emissions decrease by either increasing boot length or decreasing boot velocity. The physical analysis reveals that this is due to the penetration of the high-reactivity fuel vapor in whole squish area and a large portion of the crevice. This is because the more uniform mixture in the squish region slightly mitigates the formation of hot spots and NOx, and the propagation of reaction deeper into the crevice considerably reduces carbon monoxide and unburned hydrocarbons there. The sensitivity analysis manifests that swirl ratio has the strongest effect on all objectives, and besides swirl ratio, SOI2 has the greatest impact on gross indicated efficiency and emission, while SOI1 has the strongest influence on second-law efficiency and ringing intensity. The optimal case with an advance of SOI1 and a slight retard of SOI2, that is, a longer duration between the two injections, a lower swirl ratio (of 0.5) with respect to the base case, and appropriate injection rate-shape parameters (a high boot length and low boot velocity), achieves the gross indicated efficiency of 54% and merit function of 615.

Sign in / Sign up

Export Citation Format

Share Document