Homogeneous Charge Compression Ignition Engine Research Articles

Numerical Investigation of the Effect of Equivalence Ratio on Start of Combustion and Emissions in Homogeneous Charge Compression Ignition Engine Fuelled with Natural Gas

Numerical Investigation of the Effect of Equivalence Ratio on Start of Combustion and Emissions in Homogeneous Charge Compression Ignition Engine Fuelled with Natural Gas

Numerical Study on the Effect of Fuel Rich n-Heptane on In-Cylinder Fuel Reforming Characteristics in an HCCI Engine

The effect of in-cylinder fuel reforming on an n-heptane homogenous charge compression ignition engine has been studied. A dedicated cylinder without a complex control system is proposed for fuel enrichment reforming, which can provide part of the power for the engine. The effects of different reforming species on engine performance and chemical reaction have been simulated by a numerical study. By comparing the combustion characteristics of n-heptane with different equivalence ratios in the reformer cylinder, the optimal n-heptane equivalence ratio has been determined. The enrichment of n-heptane produces sufficient hydrogen (H2) and carbon monoxide (CO), while the hydrocarbon content of the reforming species was low. It was found that the addition of reforming species retards the combustion phase of n-heptane, thereby providing a means of controlling engine performance. In addition, the laminar flame speed and the adiabatic flame temperature of n-heptane increased by adding H2 and CO. Fuel reforming reduced the emission of ethylene, propyne, allene, propylene, butadiene, and nitrogen oxide, but it increased the emissions of acetylene and CO. Moreover, chemical, dilution, and thermodynamic effects of the reforming gas have been studied. The results showed that the chemical effect of the reforming species was less significant than the dilution and thermodynamic effects. These simulation results showed that in-cylinder fuel reforming can effectively improve engine performance and thereby reduce emissions.

Investigation of a Combined Refrigeration and Air Conditioning System Based on Two-Phase Ejector Driven by Exhaust Gases of Natural Gas Fueled Homogeneous Charge Compression Ignition Engine

Abstract A natural gas-fueled homogeneous charge compression ignition (HCCI) engine is coupled to an exhaust gas operated turbine driven two-phase ejector cycle to generate power and cooling energy, simultaneously. By establishing a thermodynamic model, the simulation of the proposed system and its parametric analyses are conducted. Energetic and exergetic investigations are carried out to study the role of equivalence ratio, engine speed, condenser temperature, refrigeration evaporator temperature, air-conditioning evaporator temperature, and ejector nozzle efficiency on the thermodynamic performance parameters of the combined cycle. The analysis of two-phase ejector cooling cycle using three working fluids including R717, R290, and R600a is conducted. Results reveal that the thermal efficiency of HCCI engine is increased from 47.44% to 49.94%, and for the R600a operated combined cycle it is increased from 60.05% to 63.26% when the equivalence ratio is promoted from 0.3 to 0.6. Distribution of fuel exergy results show that out of 100% exergy input, in case of R717 operated combined cycle, 139.79 kW (38.72%) is the total exergy output, and 164.21 kW (45.49%) and 57 kW (15.79%) are the values for exergy destruction and exergy losses. It is further shown that change in refrigerant minorly influence the percentages of exergy distribution.

Numerical study for influence of ozone on the combustion of biodiesel surrogates in a homogeneous charge compression ignition engine

Biodiesel is a potential fuel for homogeneous charge compression ignition (HCCI) engines. The impacts of ozone on the combustion of biodiesel were investigated to achieve better performance in HCCI engines with ozone addition. By considering methyl decanoate (MD), methyl-9-decenoate (MD9D) and n-heptane as the surrogates, a skeletal biodiesel mechanism was constructed for predicting combustion process with ozone addition. On one hand, the influences of ozone addition on the two-stage ignition for HCCI engines fueled with biodiesel were studied on a variety of conditions, including initial temperatures, equivalence ratio and compositions ratio of surrogates. On the other hand, the enhancements of these conditions on promoting effects of ozone were analyzed. Compared to thermal and dilution effects, the chemical effect of ozone on the ignition plays a more important role. The H-abstraction reaction of n-heptane by O atom shows higher sensitivity to ozone and the ignition of n-heptane was promoted most. Results reveal the importance of H-abstraction reaction of fuel via O atom in the combustion of multi-components with ozone seeding. In addition, the initial temperature, equivalence ratio and blended fuel that is sensitive to ozone could be considered as auxiliary adjustments for ozone assisting to control combustion.

An experimental and kinetic modeling study of NOx sensitization on methane autoignition and oxidation

An experimental and kinetic modeling study of the influence of NOx (i.e. NO2, NO and N2O) addition on the ignition behavior of methane/‘air’ mixtures is performed. Ignition delay time measurements are taken in a rapid compression machine (RCM) and in a shock tube (ST) at temperatures and pressures ranging from 900–1500 K and 1.5–3.0 MPa, respectively for equivalence ratios of 0.5–2.0 in ‘air’. The conditions chosen are relevant to spark ignition and homogeneous charge compression ignition engine operating conditions where exhaust gas recirculation can potentially add NOx to the premixed charge. The RCM measurements show that the addition of 200 ppm NO2 to the stoichiometric CH4/oxidizer mixture results in a factor of three increase in reactivity compared to the baseline case without NOx for temperatures in the range 600–1000 K. However, adding up to 1000 ppm N2O does not show any appreciable effect on the measurements. The promoting effect of NO2 was found to increase with temperature in the range 950–1150 K, while the sensitization effect decreases at higher pressures. The experimental results measured are simulated using NUIGMech1.2 comprising an updated NOx sub-chemistry in this work. A kinetic analysis indicates that the competition between the reactions ĊH3 + NO2 ↔ CH3Ȯ + NO and ĊH3 + NO2 (+M) ↔ CH3NO2 (+M), the former being a propagation reaction and the latter being a termination reaction governs NOx sensitization on CH4 ignition. Recent calculations by Matsugi and Shiina (A. Matsugi, H. Shiina, J. Phys. Chem. A. 121 (2017) 4218–4224) for the nitromethane formation reaction CH3 + NO2 (+M) ↔ CH3NO2 (+M), together with the recently calculated rate constants for HONO/HNO2 reactions significantly improve ignition delay time predictions in the temperature range 600–1000 K. Furthermore, the experiments with NO addition reveal a non-monotonous sensitization impact on CH4 ignition at lower temperatures with NO initially acting as an inhibitor at low NO concentrations and then as a promoter as NO concentrations increase in the mixture. This non-monotonous trend is attributed to the role of the chain-termination reaction ĊH3 + NO2 (+M) ↔ CH3NO2 (+M) and the impact of NO on the transition to the chain-branching steps CH2O + HȮ2 ↔ HĊO + H2O2, H2O2 (+M) ↔ ȮH + ȮH (+M), HĊO ↔ CO + Ḣ followed by CO + O2 ↔ CO2 + Ö and Ḣ + O2 ↔ Ö + ȮH. NUIGMech1.2 is systematically validated against the new ignition delay measurements taken here together with species measurements and high temperature ignition delay time data available in the literature for CH4/oxidizer mixtures diluted with NO2/N2O/NO and is observed to accurately capture the sensitization trends.

Development of a fast-virtual CFR engine model and its use on autoignition studies

Homogenous charge compression ignition engines have been studied as an alternative to the conventional diesel combustion to attain high efficiency with ultra-low NOx and soot emissions for a wide variety of fuels. However, its usage in real applications has been restricted due to the difficulties regarding combustion control and operating range extension. The modification of the fuel characteristics may be a pathway to solve the previous hurdles. Therefore, this research presents a relevant methodology to assess the fuel response to HCCI boundary conditions based on 0-D and 1-D modelling for detailed chemistry solution and state conditions definition, respectively. The results suggest that the methodology can predict the early stages of the fuel oxidation with good accuracy. For the objective of predicting the start of combustion, the best results are obtained using tabulated chemistry when investigating fuels that have pre reactions and a low temperature heat release. As the oxidation process progresses, the deviation of the pressure-temperature trajectory from non-reactive to reactive conditions after the low temperature heat release decreases the predictive capability to some extent. Nonetheless, the methodology outcomes are still valid as a qualitative metric for reactivity determination as well as the intermediate and high temperature ignition delay.

Role of hydrogen in improving performance and emission characteristics of homogeneous charge compression ignition engine fueled with graphite oxide nanoparticle-added microalgae biodiesel/diesel blends

The development of low-temperature combustion models combined with the use of biofuels has been considered as an efficient strategy to reduce pollutant emissions like CO, HC. NOx, and smoke. Indeed, Homogeneous Charge Compression Ignition (HCCI) is the new approach to drastically minimize NOx emissions and smoke owing to the lower cylinder temperature and a higher rate of homogeneous A/F mixture as compared to compression ignition (CI) engines. The present research deal with the behavior analysis of a CI engine powered by diesel, Euglena Sanguinea (ES), and their blends (ES20D80, ES40D60, ES60D40, ES80D20). The experimental results revealed the highest brake thermal efficiency for ES20D80 although it decreased by 4.1% compared to diesel at normal mode. The average drop in HC, CO, and smoke was 2.1, 2.3, and 5.7% for ES20D80 as opposed to diesel fuel. Therefore, in the next stage, ES20D80 with various concentrations of graphite oxide (GO) nanoparticle (20, 40, 60, and 80 ppm) was chosen to carry out experiments in the HCCI mode, in which hydrogen gas was induced along with air through the intake pipe at a fixed flow rate of 3 lpm for the enrichment of the air-fuel mixture. As a result, the combination of hydrogen-enriched gas and GO-added ES20D80 in the HCCI mode showed similar performance to the CI engine but registered a major reduction of NOx and smoke emissions, corresponding to 75.24% and 53.07% respectively, as compared to diesel fuel at normal mode.

Optimization of Valve Profile for a Homogeneous Charge Compression Ignition Engine

İçten yanmalı motorların giderek sıkılaşan emisyon standartları dolayısıyla, farklı konseptlerle yanma gerçekleştirilmesi ve emisyonlarının azaltılması amaçlanmaktadır. Homojen dolgulu sıkıştırma ateşlemeli motorlarda, görece düşük sıcaklıklarda yanma meydana geldiğinden dolayı, çok düşük NOX ve is emisyonları açığa çıkmaktadır. Ancak yanma prosesi, vuruntusuz ve teklemesiz olarak gerçekleşebilmesi için motorun iyi bir şekilde kontrol edilmesi ve bütün parametrelerinin optimize edilmesi gerekmektedir. Bu çalışmada, homojen dolgulu sıkıştırma ateşlemeli dizel yakıtlı bir motorun, bu yeni nesil yanma stratejisine uygun olarak supap profili bir boyutlu yanma modeli ve genetik algoritma kullanılarak optimize edilmiştir. Supap açılma ve kapanma krank açıları parametrik olarak değiştirilmiştir. Ayrıca, supap profilinin tamamen açıldığı noktaya bekleme eklenmiştir. Böylelikle, volümetrik verim artışı hedeflenmiş ve fren gücü değeri maksimize edilmiştir. Tasarlanan yeni supap profili ile motor fren gücü %28 artarken, özgül yakıt tüketimi değeri %6 azalmıştır.

Important Contributions to Reducing Nitrogen Oxide Emissions from Internal Combustion Engines.

Nitrogen oxides are considered significant pollutants because of their effects on ecosystems and human health. The amount of NOx emitted by internal combustion engines can be reduced, mostly by acting on the conditions in which combustion takes place, respectively by lowering the peak flame temperature, reducing the excess of oxygen, etc. The homogeneous charge compression ignition (HCCI) engine represents a new technology that can simultaneously reduce NOx emissions and fuel consumption. This article presents these benefits of the HCCI engine by comparing the emissions and fuel consumption of a monocylinder engine when it is operated in a conventional way, with spark ignition, with those obtained when the engine is running in the HCCI mode. Moreover, since engine simulation has become an important tool for investigating the HCCI process and for developing new control strategies for it, this was used in this study to determine the effects of the exhaust gas recirculation on the combustion quality, respectively, on emissions.

Influence of syngas composition on combustion and emissions in a homogeneous charge compression ignition engine

Homogeneous charge compression ignition (HCCI) is a promising combustion concept that can simultaneously achieve high efficiency and low nitrogen oxides (NOx) emissions. Synthesis-gas (syngas)-fueled HCCI engines can be adapted for a wide range of fuel compositions. The aim of this study was to investigate the combustion and emissions of an HCCI engine with various syngas compositions. The baseline syngas contained 30% H2, 25% CO, and 45% CO2 by volume, which provided a low heating value (LHV) of 6.08 MJ/Nm3. The fuel composition varied from hydrogen-rich to lean. It was found that syngas with an LHV of 3.34 MJ/Nm3 could be auto-ignited by implementing intake boosting with sufficient intake heating. The intake temperature required to achieve autoignition was reduced at higher loads. The start of combustion temperature mainly relied on the intake temperature and fueling rate, regardless of the fuel composition. A higher H2 content in the fuel facilitated fast burning with good combustion stability, even under lean conditions. It was revealed that a higher CO fraction deteriorated the combustion stability on the lean side with slow burning. The gross indicated thermal efficiency (ITEg) increased with an increase in the LHV of the syngas, with an ITEg of 38.1% realized at a low load of 0.3 MPa for the base fuel, while maintaining engine stability. The combustion efficiency was greater than 90% for the fuels examined at a higher fuel rate. The NOx emissions were very low because of the ultra-lean, diluted charge used for HCCI combustion.

Effects of light naphtha utilization on engine performance in an homogeneous charged compression ignition engine

In the current study, the effects of light naphtha utilization were experimentally investigated in a diesel engine operated with HCCI mode. Engine load, fuel consumption, in-cylinder pressure and emissions were measured in the experiments. 100 % light naphtha, 90% light naphtha +10% gasoline, 80% light naphtha +20% gasoline, 70% light naphtha +30% gasoline and 50% light naphtha +50% gasoline fuel blends were used as test fuels. Experiments were conducted between 7 and 14 ms injecton duration and 1100 and 1900 rpm engine speed with the intervals of 0.5 ms and 200 rpm respectively. The lowest fuel consumption was obtained as 584.42 g/kWh at 1500 rpm and 2.39 air excess coefficient with 90% light naphtha +10% gasoline and 12.5 ms injection duration. The highest engine torque was measured as 4.18 Nm at 1500 rpm and 2.31 air excess coefficient with 80% light naphtha +20% gasoline test fuel and 13.5 ms injection duration. Almost zero NO emission was observed for all HCCI operating conditions.

Control-oriented modeling of the gas exchange process in rebreathing homogeneous charge compression ignition engines

The purpose of this study is to develop a model for the gas exchange process in a rebreathing homogeneous charge compression ignition (HCCI) engine. HCCI engines are attracting significant attention due to their low emissions and high efficiency. To design the control system of an HCCI engine, it is necessary to develop a control-oriented engine model. The developed model lowers its computational load by combining two types of models. The model consists of a discrete model for the exhaust process (the first half of the gas exchange process) and a continuous model with a variable calculation step size for the rebreathing process (the latter half of the gas exchange process). Also, the constructed model maintained its prediction accuracy, as the pressure pulsation in the exhaust port was modeled, and an unsteady flow equation was used. It was confirmed that the model developed for the gas exchange process calculated in about half time of one cycle and reproduced the results of 1D engine simulation software with a maximum error of about 10% in the in-cylinder pressure, temperature, and trapped mass.

Experimental Investigation on Emission Characteristics of Diesel N-Pentanol Blend in Homogeneous Charged Compression Ignition Engine

The invention of internal combustion engines is undoubtedly one of the greatest inventions of the modern era. There has been steady scientific research to look for alternative fuel which is economical, renewable and less harmful to nature and man compared to fossil fuels. The present project is one such experimental work to investigate the performance of a blend of diesel / N-pentanol in an appropriate combustion technique and to establish its suitability as a renewable fuel. The relative performance of diesel fuel and the blend of diesel / n-pentanol will also be analyzed. Diesel fuel blended with 30 percentage n-pentanol is the fuel blend that is proposed to be used in the experiment. Researchers have established that the application of Homogeneously Charged Compression Ignition (HCCI) technique could result in in-cylinder reduction of NOx and PM. Higher thermal efficiency could also be attained. The project also covers studying the emission effect of the diesel/n-pentanol fuel blend for various fuel injection timing, various fuel injection pressure, different EGR rates and different inlet air temperature.

A novel design of power-cooling cogeneration system driven by solid oxide fuel cell waste heat in ocean-going vessels

Among many global energy and environmental problems, the ocean and air pollution caused by ocean-going vessels cannot be ignored. Cleaner and more efficient power generation systems should be used to replace traditional diesel generators on ships. To this problem, the combination of fuel cell and waste heat recovery technology can become a better choice. In this paper, a novel power-cooling cogeneration system is designed and analyzed, which is mainly composed of solid oxide fuel cell, preheating subsystem, homogeneous charge compression ignition engine and double-effect absorption refrigeration cycle. The study mainly includes mathematical modeling, reliability verification of each subsystem, numerical simulation and results analysis in energy, exergy and economics. The results show that the system thermal efficiency and exergy efficiency can reach 64.01% and 61.83%, respectively, which are 18.76% and 12.62% higher than those of simple cell. Compared with traditional combined system, the payback time of the proposed scheme is about 2.59 years, which not only proves that the cost can be recovered in a short time, but also shortened by about half. By improving energy efficiency and reducing costs, the proposed scheme can ensure the demand of electricity and cold energy in daily life of the crew, and provides a new choice for the marine auxiliary power generation equipment.

Emissions from homogeneous charge compression ignition (HCCI) engine using different fuels: a review.

The main objective of this paper is to review the emission characteristics of homogeneous charge compression ignition (HCCI) engines using different fuels and additives. Additionally, the impacts of various operating conditions on HCCI engine emissions are also analyzed. There is a demand faced by the engine and car manufacturers for high fuel efficiency and low emission from both consumers and the government. HCCI is an alternative internal combustion technology that is more efficient and cleaner than traditional combustion techniques. In this engine, fuel and oxidiser (typically air) are entirely mixed and compressed to the point of auto-ignition. It is a new combustion concept that provides high efficiency and resolves high nitrogen oxide (NOx) and particulate matter (PM) emissions simultaneously. Conventional diesel engine emits NOx around 2000-2500 ppm which is a primary concern; however, when diesel is used in HCCI engine, it reduces NOx to only 70-400 ppm. Furthermore, natural gas cannot be used as fuel in the conventional engine but can be used in HCCI engine. It helps reduce NOx emission even below 10 ppm. This paper reviews several works done by researchers on HCCI engines to reduce their emissions and benefit future research.

Thermodynamic and Comparative Analysis of Ejector Refrigeration Cycle and Absorption Refrigeration Cycle Integrated Wet Ethanol-Fueled HCCI Engine for Cogeneration of Power and Cooling

Abstract This study attempted for the proposal and analysis of a combined cycle that consists of a wet ethanol-fueled and turbocharged homogeneous charge compression ignition (HCCI) engine coupled to ejector refrigeration cycle (ERC) and absorption refrigeration cycle (ARC) for the simultaneous generation of two distinct outputs, namely, power and refrigeration. Both first and second laws of thermodynamics were employed to develop a thermodynamic model, which has been applied to investigate the performance of combined cycle. Furthermore, performance of the combined cycle for ERC versus ARC was compared and assessed after altering operating parameters (turbocharger pressure ratio, turbocharger compressor efficiency, ambient temperature, and the entrainment ratio of ERC and generator temperature of ARC) to study their effect on engine power output, refrigeration load, exergy of refrigeration, and energy and exergy efficiencies of the cooling-power cogeneration cycle. Results show that the elevated pressure of turbocharger results in the enhancement of HCCI engine power and increase of the refrigeration of thermal load, simultaneously. However, the increasing ambient temperature shows the decline of HCCI engine efficiencies and energy efficiency of cogeneration, while the cogeneration cycle exergy efficiency is found increasing. Furthermore, the results are reported for the refrigeration performed by lithium bromide–water (LiBr–H2O)-operated ARC, and R134a- and R290-operated ERC, respectively. Mapping of exergy destruction for the presented cogeneration cycle discovered HCCI engine, boiler of ERC, generator of ARC, and catalytic convertor as the components of significant exergy destruction. Entrainment ratio and type of refrigerant employed in ERC and the generator temperature of ARC show a marginal impact on the COPs of these cycles.

Study of the Combustion Process of a Homogeneous Charge Compression Ignition (HCCI) Engine and a Partially Premixed Combustion (PPC) Mode of a Compression Ignition Engine Using Natural Gas as an Alternative Fuel

In order to investigate a viable approach to achieving high efficiencies and low nitrogen oxide (NOX) emissions, this paper presents the application of a homogeneous charge compression ignition (HCCI) engine and the partially premixed combustion (PPC) mode applied to a heavy diesel engine. The effect of carbon dioxide (CO2) fraction on combustion parameters was analyzed and discussed in detail. For this purpose, on the one hand, ANSYS CHEMKIN-Pro software was used to perform simulations of a closed homogeneous reactor under conditions relevant to HCCI engines, and on the other hand, ANSYS-Fluent software was used by adding a CO2 fraction varying from 20% to 58% to methane fuel to study 2D flow simulation by applying a PPC combustion mode to predict the distribution of various output parameters such as in-cylinder temperature, in-cylinder pressure and emissions. In comparison with the two presented models, it was found that the HCCI engine showed a lower NOX level than the PPC mode and this was due to the lower in-cylinder temperature in the HCCI engine.

Comparative study of energy losses related to the ring pack operation in homogeneous charge compression ignition and spark ignition combustion

Low-temperature combustion in homogeneous charge compression ignition (HCCI) engine is one of the most promising technologies allowing to meet future emission targets for internal combustion engines. Whereas majority of research is centred on combustion itself, this paper for the first time points out the piston's energy losses induced by friction and blow-by in HCCI engine with negative valve overlap. The energy losses for HCCI and spark ignition (SI) operating modes were compared and thoroughly analysed with the use of the ring pack model. The input data for the simulations came from measurements made on a single-cylinder research engine capable of dual-mode combustion. The energy losses associated with friction of the rings against the cylinder varied from 8.2% of the indicated energy at the lowest load to 2.2% at the highest load tested, and were higher than in the SI mode by approximately 7%. The losses due to the gas leakage through the ring pack in the HCCI mode varied from 8% to 3.3%, respectively, and these losses were about twice as high as in the SI engine. The results demonstrated that energy losses due to blow-by are comparable with the friction losses of the rings, which are usually regarded as the prime source of inefficiency.

Thermodynamic and statistical analysis on the effect of exhaust gas recirculation on waste heat recovery from homogeneous charge compression ignition engines

Thermodynamic and statistical analysis on the effect of exhaust gas recirculation on waste heat recovery from homogeneous charge compression ignition engines

Lipschitz discrete observer design for HCCI engine mixed gas temperature at intake valve closed

The gas temperature for Homogeneous Charge Compression Ignition engine at intake valve closed is difficult to measure; so a Lipschitz discrete observer is designed. In particular, a single cylinder engine model is proposed. And, a thermodynamic process based state equation is presented considering the heat loss of residual exhaust gas. Consequently, a discrete nonlinear state observer is designed using Lipschitz condition. Finally, the numerical experiments are performed. The results demonstrate the effectiveness of the proposed observer in terms of the accuracy and robustness.