Homogeneous Charge Compression Ignition Engine Research Articles

Effect of water injector location on combustion and performance of an HCCI engine - A CFD analysis

A homogeneous charge compression ignition (HCCI) engine is capable of producing high thermal efficiency with very low emissions. However, because of the limited upper load level constrained by knocking, the HCCI engine is not yet commercialized. Water injection can tackle this issue, enhancing the upper load limit without excessive heat release rate. However, the effectiveness of water injection depends on in-cylinder water evaporation, which in turn depends on water injection parameters. Therefore, this study is conducted to study the effect of water injector location on the combustion and performance characteristics of an HCCI engine by a computational fluid dynamic (CFD) analysis. The engine specifications and boundary conditions are taken from the literature. A three-dimensional computational fluid dynamics (3D CFD) model was developed using CONVERGE CFD coupled with detailed chemical kinetics to gain a better understanding of the phenomena of water injection in an HCCI engine. The CFD models used are validated from the available experimental data in the literature for the engine considered. Here, the water injector location is optimized based on the Water vapor distribution within the cylinder, nitric oxide (NOx) emissions, and maximum rate of pressure rise (MRPR). The results show that the water injector at 37 mm from the center of the cylinder gives better results than in other cases considered. With the optimum water injector location, the indicated mean effective pressure is increased by about 35.91% than without the water injection case. This study will be helpful in the development of HCCI engines.

Advancements in homogeneous charge compression ignition technology: Efficiency, emissions, and applications in the modern automotive industry

Homogeneous charge compression ignition (HCCI) technology is a novel approach in internal combustion engines that combines the efficiency of gasoline engines with the spontaneous ignition characteristics of diesel engines. HCCI engines offer cleaner emissions, reduced noise, and wider fuel adaptability, overcoming many drawbacks of traditional engines. The paper explores the HCCI combustion process, highlighting its unique features and advantages over spark ignition (SI) and compression ignition (CI) engines. It also discusses innovations in HCCI technology, including its combination with other strategies like spark-controlled compression ignition (SCCI) and low-temperature combustion (LTC) to expand its load range. The challenges of HCCI technology, especially in combustion timing control, are addressed, along with suggestions for future research directions. The application of HCCI technology for energy savings and emission reduction and its impact on the automotive industry are also discussed, citing examples from manufacturers like Volvo, Nissan, and General Motors. The paper concludes by emphasizing the importance of ongoing research, integration with other technologies, and financial support to further advance HCCI technology and its market potential.

Computational Fluid Dynamics (CFD) Validation and Investigation the Effect of Piston Bowl Geometries Performance on Port Fuel Injection-Homogeneous Charge Compression Ignition (PFI-HCCI) Engines

Computational Fluid Dynamics (CFD) Validation and Investigation the Effect of Piston Bowl Geometries Performance on Port Fuel Injection-Homogeneous Charge Compression Ignition (PFI-HCCI) Engines

Experimental Study of a Homogeneous Charge Compression Ignition Engine Using Hydrogen at High-Altitude Conditions

One of the key factors of the current energy transition is the use of hydrogen (H2) as fuel in energy transformation technologies. This fuel has the advantage of being produced from the most primary forms of energy and has the potential to reduce carbon dioxide (CO2) emissions. In recent years, hydrogen or hydrogen-rich mixtures in internal combustion engines (ICEs) have gained popularity, with numerous reports documenting their use in spark ignition (SI) and compression ignition (CI) engines. Homogeneous charge compression ignition (HCCI) engines have the potential for substantial reductions in nitrogen oxides (NOx) and particulate matter (PM) emissions, and the use of hydrogen along with this kind of combustion could substantially reduce CO2 emissions. However, there have been few reports using hydrogen in HCCI engines, with most studies limited to evaluating technical feasibility, combustion characteristics, engine performance, and emissions in laboratory settings at sea level. This paper presents a study of HCCI combustion using hydrogen in a stationary air-cooled Lombardini 25 LD 425-2 modified diesel engine located at 1495 m above sea level. An experimental phase was conducted to determine the intake temperature requirements and equivalence ratios for stable HCCI combustion. These results were compared with previous research carried out at sea level. To the best knowledge of the authors, this is the first report on the combustion and operational limits for an HCCI engine fueled with hydrogen under the mentioned specific conditions. Equivalence ratios between 0.21 and 0.28 and intake temperatures between 188 °C and 235 °C effectively achieved the HCCI combustion. These temperature values were, on average, 100 °C higher than those reported in previous studies. The maximum value for the indicated mean effective pressure (IMEPn) was 1.75 bar, and the maximum thermal efficiency (ITEn) was 34.5%. The achieved results are important for the design and implementation of HCCI engines running solely on hydrogen in developing countries located at high altitudes above sea level.

Computational investigation of equivalence ratio effects on performance and emissions in a dual-fuel homogeneous charge compression ignition (HCCI) engine with 90% n-dodecane and 10% ethanol

As the automotive industry seeks environmentally friendly and fuel-efficient solutions, a significant transformation towards the Dual Fuel Homogeneous Charge Compression Ignition (DF-HCCI) Engine. It emerges as a highly promising and revolutionary approach to internal combustion engines. This paper provides a comprehensive Computational Investigation on the influence of Equivalence Ratio (ϕ) variations on the performance and emissions of a DF-HCCI engine, utilising a blend of 90% n-dodecane (premix) and 10% ethanol (spry injection). Through simulations, the study explores ϕ ranging from 0.45 to 0.70, providing a detailed analysis of their impact on crucial engine parameters. Results indicate a non-monotonic behaviour in piston work, with an initial increase followed by a decline beyond an optimal point due to incomplete combustion. CO emissions exhibit a general increase with higher ϕ, attributed to reduced air availability for complete combustion. CO2 emissions display a non-monotonic trend, peaking at ϕ = 0.5, indicative of a complex interplay between combustion temperature and completeness. NOx emissions decrease with rising ϕ, as higher temperatures favour NOx formation. Soot emissions decrease with increasing ϕ , correlating with lower combustion temperatures. This investigation provides insights into the relationship between ϕ and DF-HCCI engine characteristics, offering an optimising engine efficiency and mitigating environmental impact.

Effect of boundary on homogeneous charge compression ignition engine fueled with anode off-gas and refueled anode off-gas

Hybrid solid oxide fuel cells and internal combustion engine systems are one of the most efficient power plants for low-carbon fuels. But the utilization of anode off-gas was a challenge. Homogeneous charge compression ignition has the advantage for such dilute and high-temperature fuels of 800 K∼ 1000 K and 80% inert gases, but easily influenced by intake temperature, pressure and composition. Based on 1-D model coupled with detail methane-air mechanism. Insights into engine performance combining thermodynamic trajectory and CA50 iso-contour on the PT domain for combustion of anode off-gas and refueled off-gas was provided. Results show that refueling strategy would benefit indicated mean effective pressure and misfire, but had little effect on thermal efficiency, and increase the possibility of knock and emissions by autoigniting in advanced and increased fuel reactivity. Exhaust gas recirculation strategy helped operate at low-temperature and low-pressure with refueling strategy. The overlapping safe zone implies the safe temperature and pressure for engine fueled with anode off-gas to add new fuel. As equivalence ratio increased, the thermal efficiency first increased and then decreased, peaking at 0.3. Although the combustion of the compression ratio of 17.1 is higher than that of the compression ratio of 8.2, the thermal efficiency and knock trend is worse.

Experimental and numerical investigation of methane combustion in a HCCI engine under enriched oxygen conditions

The challenge in the energy transition lies in the intermittent nature of renewable energy, requiring the development of effective storage methods. E-fuels are considered a promising solution, with potential applications to Homogeneous Charge Compression Ignition (HCCI) engines known for their high thermal efficiency and low nitrogen oxide emissions. However, HCCI engines face limitations such as low power density and a narrow operating range. To overcome these issues, oxygen-enriched combustion is proposed, aiming at enhancing the mixture reactivity and expanding the operating range by decreasing the intake temperature. As the potential of the expansion of the operating range has never been investigated, we performed an experimental campaign using a methane-fuelled HCCI engine at variable oxygen fractions in the oxidizer. To further elucidate the effects of oxy-fuel combustion, we also performed a kinetic analysis of the reactions driving the combustion behaviour. It has been experimentally found that increasing the oxygen content in the mixture, up to 90%, has a significant potential to decrease the needed intake temperature (up to 70 °C) of the charge to keep the Maximum Pressure Rise Rate (MPRR) below the safety threshold of 8 bar/CAD. Despite the notable IMEP increase achieved, operating the engine at high oxygen content presents significant technical challenges. Therefore, to make HCCI engines competitive with other combustion modes, it is essential to combine oxygen enrichment with additional power density enhancement techniques. The kinetic analysis has highlighted that the mixture is less sensitive to intake temperature changes at higher oxygen percentages (above 50%) and that the rates of the main reactions involved in methane and OH consumption are highly enhanced by oxygen addition.

Numerical study of piston bowl geometries on PFI-HCCI engine performance

Homogeneous charge compression ignition (HCCI) is an advanced combustion strategy proposed to provide higher efficiency and lower emissions than conventional compression ignition. However, there are still tough challenges in the successful operation of HCCI engines. Among these challenges, homogeneous mixture preparation and combustion phase control plays a vital role in determining the efficiency and emissions. Piston bowl geometry significantly enhances the process by improving the flow, turbulence, and mixing for the combustion. The study utilised experimental and numerical simulation methods to analyse HCCI combustion in port fuel injection (PFI) mode and evaluate the effect of piston geometries on engine performance. For this purpose, the different pistons bowl geometries (Baseline model, SQC, and CCC) with the same volume, compression, and equivalence ratio were numerically tested in a four-stroke, single-cylinder, YANMAR diesel engine. The numerical simulation results provide adequate assurance to proceed with the study with different piston geometries design. Compared to SQC and CCC, the Baseline model produced significantly higher cylinder pressure, temperature, and heat release rate. Different piston shape designs influenced the formation of air-fuel mixing, thereby affecting the time and location of onset combustion. The present investigation offered the significant role of piston geometry for the control mechanism of PFI-HCCI combustion, that is a vital part in demonstrating HCCI combustion.

Revolutionizing engine technology: The emergence and potential of novel engine materials

Concerns from both society and the government about the pollutants from automobile exhaust is becoming more and more noticeable in recent years. Compared with the engines mostly used currently, which are gasoline engines and diesel engines, the HCCI engine has ameliorated not only the problem of pollutant emissions but also efficiency to a large extent. This paper provides an in-depth analysis of Homogeneous Charge Compression Ignition (HCCI) engines. It first introduces the fundamental processes governing HCCI combustion and illustrates its working mechanism. While HCCI engines promise heightened efficiency, reduced emissions, and fuel versatility, they also present challenges such as combustion timing and related emissions. Commercial implementations by Nissan and Honda are discussed, shedding light on real-world applicability. Furthermore, the potential amalgamation of biodiesel with HCCI is explored, signaling a promising future for renewable fuels in advanced combustion engines. Despite the rise of hybrid vehicles, the unique benefits of HCCI position it as a significant player in future transportation. This paper emphasizes the necessity of ongoing research to overcome HCCIs challenges, ensuring it remains at the forefront of green automotive solutions.

Frictional Losses of Ring Pack in SI and HCCI Engine

The vast majority of research dedicated to enhancing the homogenous charge compression ignition (HCCI) low-temperature combustion system is focused on improving controllability, efficiency and emissions. This article aims to assess the impact of HCCI combustion on the operation of the piston ring system. Utilizing the measured pressures in the combustion chamber of a single-cylinder research engine operating in spark ignition (SI) and HCCI modes at various loads, simulations were carried out using an advanced ring pack model. This model integrates the gas flow, ring dynamics and ring mixed lubrication models. Simulations revealed that differences in the pressure above the piston between the HCCI and SI combustion significantly influence ring pack performance. The predicted energy losses due to the friction of piston rings against the cylinder liner are up to 5% higher in the HCCI engine than in the SI engine. This identified drawback diminishes the advantages of the HCCI engine resulting from higher thermal efficiency, and efforts should be made to minimize this negative impact.

The study on the conversion of single cylinder engine into homogeneous charge compression ignition (HCCI) engine

The study on the conversion of single cylinder engine into homogeneous charge compression ignition (HCCI) engine

Experimental study on combustion, performance, and emission characteristics of a homogeneous charge compression ignition engine fuelled with multiple biofuel-gasoline blends

For sustainable future mobility and power generation applications, there is a compelling need to develop flex-fuel engines that operate with multiple regional or season-specific biofuels. The present investigation focussed on mitigating agricultural diesel engines’ pollutant emission and performance problems. A systematic experimental study is carried out in a modified agricultural diesel engine to compare and evaluate the engine characteristics of the biofuel-gasoline blends fuelled Homogeneous Charge Compression Ignition (HCCI) mode. Seven different oxygenated biofuels: acetone, ethanol, methanol, isopropanol, isobutanol, ethyl acetate, and diisopropyl ether blended in gasoline, were investigated. 2-Ethylhexyl nitrate was used to improve the reactivity of fuel blends to the extent that lower engine loads could be reached. All the investigated biofuel-gasoline blends could produce permissible emission levels by suitably tuning the fuel proportions. The total nitrogen oxides and smoke emissions were below 2.8 and 0.0007 g/kWh, respectively, for all the investigated biofuel-gasoline blends at all the HCCI engine load conditions. The highest indicated thermal efficiency of 42% was attained using 60% ethanol/34% gasoline/6% 2-EHN blend in the HCCI engine at 4.63 bar BMEP (86% rated load), a notable 25% improvement compared to the conventional diesel engine. A detailed investigation was done to elucidate the HCCI engine performance (indicated thermal efficiency) trend variations with biofuel type and engine load. The Response Surface Method was adopted to correlate the maximum and the minimum engine load with the fuel composition and properties. The Desirability Approach provided the optimum fuel composition and properties to maximize the engine load range. The optimum solution achieved the engine load range of 20%–89% rated load. Overall, a compact, efficient, and clean HCCI combustion-based engine technology was developed that could be operated using multiple biofuels over an expanded load range.

A co-kurtosis PCA based dimensionality reduction with nonlinear reconstruction using neural networks

For turbulent reacting flow systems, identification of low-dimensional representations of the thermo-chemical state space is vitally important, primarily to significantly reduce the computational cost of device-scale simulations. Principal component analysis (PCA), and its variants, are a widely employed class of methods. Recently, an alternative technique that focuses on higher-order statistical interactions, co-kurtosis PCA (CoK-PCA), has been shown to effectively provide a low-dimensional representation by capturing the stiff chemical dynamics associated with spatiotemporally localized reaction zones. While its effectiveness has only been demonstrated based on a priori analyses with linear reconstruction, in this work, we employ nonlinear techniques to reconstruct the full thermo-chemical state and evaluate the efficacy of CoK-PCA compared to PCA. Specifically, we combine a CoK-PCA-/PCA-based dimensionality reduction (encoding) with an artificial neural network (ANN) based reconstruction (decoding) and examine, a priori, the reconstruction errors of the thermo-chemical state. In addition, we evaluate the errors in species production rates and heat release rates, which are nonlinear functions of the reconstructed state, as a measure of the overall accuracy of the dimensionality reduction technique. We employ four datasets to assess CoK-PCA/PCA coupled with ANN-based reconstruction: zero-dimensional (homogeneous) reactor for autoignition of an ethylene/air mixture that has conventional single-stage ignition kinetics, a dimethyl ether (DME)/air mixture which has two-stage (low and high temperature) ignition kinetics, a one-dimensional freely propagating premixed ethylene/air laminar flame, and a two-dimensional dataset representing turbulent autoignition of ethanol in a homogeneous charge compression ignition (HCCI) engine. Results from the analyses demonstrate the robustness of the CoK-PCA based low-dimensional manifold with ANN reconstruction in accurately capturing the data, specifically from the reaction zones.

Frontier development and prospect trend of HCCI engine

Nowadays, with the rapid development of information technology, the level of science and technology is constantly improving. All fields are developing rapidly. In recent years, the development of the automotive engine industry has been particularly rapid. To cope with increasingly strict environmental requirements and the impact of electric motors on the market, a new engine model is gradually being valued. Homogeneous Charge Compression Ignition (HCCI) internal combustion engine is a new type of engine. It has the technical advantages of traditional diesel and gasoline engines. This combustion mode greatly improves the emission of pollutants and the engine’s overall efficiency. However, there are still certain challenges to this technology at present. But with the continuous improvement and optimization of related technologies. HCCI engines are bound to have broad development prospects. This article elaborates on the current status and development trends of HCCI engines from four perspectives: basic principles, combustion characteristics, emission characteristics, and the latest developments.

LSTM for Modeling of Cylinder Pressure in HCCI Engines at Different Intake Temperatures via Time-Series Prediction

Modeling engines using physics-based approaches is a traditional and widely-accepted method for predicting in-cylinder pressure and the start of combustion (SOC). However, developing such intricate models typically demands significant effort, time, and knowledge about the underlying physical processes. In contrast, machine learning techniques have demonstrated their potential for building models that are not only rapidly developed but also efficient. In this study, we employ a machine learning approach to predict the cylinder pressure of a homogeneous charge compression ignition (HCCI) engine. We utilize a long short-term memory (LSTM) based machine learning model and compare its performance against a fully connected neural network model, which has been employed in previous research. The LSTM model’s results are evaluated against experimental data, yielding a mean absolute error of 0.37 and a mean squared error of 0.20. The cylinder pressure prediction is presented as a time series, expanding upon prior work that focused on predicting pressure at discrete points in time. Our findings indicate that the LSTM method can accurately predict the cylinder pressure of HCCI engines up to 256 time steps ahead.

Investigation of conversion of a diesel engine to homogeneous charge compression ignition engine using n-heptane: A zero-dimensional modeling

Numerical methods are commonly used for analyzing combustion characteristics. Besides, they provide an opportunity to predict emissions of an engine. In this paper, the conversion of a single-cylinder diesel engine to HCCI combustion model is investigated with AVL Boost v2021R2. The model was used to simulate the power, emission, bsfc value. In-cylinder pressure results also are obtained from the model. Verification of the model is conducted with experimental data from the literature. The differentiation between the numerical and experimental results remained below 8.9% for the power, below 6.62% for bsfc. In addition to this, the model gave maximum pressure values with an accuracy of ± 1%, and maximum HRR values with an accuracy of ± 2%. Maximum HRR values and in-cylinder pressure curves for 1200-2400 rpm were obtained with acceptable accuracy. Besides, the operating range of an HCCI engine fueled with n-heptane was investigated using a zero-dimensional single-zone model with reduced fuel chemistry. The compression ratio and inlet air temperature effect on HCCI combustion were analyzed. The increasing the air inlet temperature to 40oC from 20oC, increases the lowest air-fuel ratio about 6.6% which the engine can operate without entering the knock zone, at 17.5 CR at 1200rpm.

Development and assessment of a novel natural gas fuelled HCCI engine based combined power, heating, and refrigeration system

Internal combustion engines waste a significant amount of energy from the fuel they consume, mostly through the atmospheric release of engine exhaust gases. This phenomenon is well acknowledged as a significant contributor to engine inefficiencies and the production of harmful pollutant emissions. In order to tackle this issue, a bottoming cycle that combines a supercritical CO2 (S–CO2) power cycle with an ejector refrigeration cycle (ERC) is implemented. The goal is to generate power, heating, and cooling utilizing waste heat from a natural gas-powered homogeneous charge compression ignition (HCCI) engine. The study found that the HCCI engine, when not utilizing a bottoming cycle, demonstrated thermal and exergy efficiencies of 48.30% and 40.83%, respectively. However, the incorporation of S–CO2 and ERC cycles resulted in significantly higher system efficiencies of 64.90% and 48.84%, respectively. Furthermore, the proposed system has thermal efficiencies of 53.86% for electrical output, 7.801% for heating output, and 3.239% for cooling output. In addition, the HCCI engine accounts for the most exergy destruction in the system, accounting for 92.83 kW (25.72%), with losses due to in-cylinder heat transfer and system exhaust accounting for 20.63 kW (5.72%) and 12.52 kW (3.47%), respectively.

A comprehensive review into the effects of different parameters on the hydrogen‐added HCCI diesel engine

AbstractThe current study presents research investigations and developments related to the homogeneous charge compression ignition (HCCI) engine. Research investigations and recent advances, including the role of various operating conditions on HCCI engine combustion phenomena, emissions, and performance, are discussed. There is growing research interest in investigating HCCI engines with diesel fuel to study combustion, emissions, and performance characteristics due to their association with low NOx emissions. In the published literature, research investigations are also conducted with different fuels ranging from biomass to diesel to gasoline in the HCCI engine showing its capability for utilizing various fuels in coming years. The challenges associated with HCCI combustion are reviewed, and the details of excessive carbon monoxide and unburnt hydrocarbon emissions are discussed. The major parameters affecting the hydrogen addition in HCCI diesel engines are also discussed. Overall, adding hydrogen to a diesel‐fueled HCCI engine improves combustion phasing and can potentially increase thermal efficiency while lowering emissions. In addition, the strength, weaknesses, opportunities, and threat analysis is provided and discussed thoroughly.

Effects of water direct injection on a combustion phase and performance of six-stroke gasoline homogeneous charge compression ignition engine

An experimental study was conducted to examine how direct water injection (WI) can optimize the combustion phases of a six-stroke gasoline homogenous charge compression ignition (HCCI) engine. With six-stroke HCCI combustion, the limitations of four-stroke HCCI combustion under high loads and the stability of combustion under low loads can be resolved by adding additional compression and expansion stroke. Previous six-stroke HCCI combustion research suggested that the time loss could be reduced by delaying the combustion phase to the top dead center (TDC) with additional cooling. Thus, in this study, the effects of WI on the overall pressure curve, as well as the first and second combustion phases, were studied from a thermal and chemical kinetics perspective. The performance, thermal efficiency, and pressure rise rate were also examined. It was found that WI retarded the first and second combustion. The first and second combustion phases were located after and before TDC, respectively, resulting in a decrease in the first gross mean effective pressure (GMEP) (180–540 CA) and an increase in the second GMEP (540–900 CA). Because the increase of second GMEP was dominant, the indicated thermal efficiency also monotonically increased (2.7–3.5%p). In addition, the maximum pressure rise rate decreased by 23.1% to 65.2%. Thus, the WI can be used to control the combustion characteristics of six-stroke gasoline HCCI engine.

Effects of temperature and composition inhomogeneity on the ignition characteristics of NH3/H2 co-firing fuels under HCCI operating conditions

The application of ammonia (NH3) in combustion devices, such as internal combustion engines (ICEs), is expected to largely reduce the greenhouse gas (CO2) emission. NH3/H2 cofiring fuels in homogeneous charge compression ignition (HCCI) engines may provide a potential way to deal with zero carbon requirements. However, in HCCI engines, the ignition process needs to be moderated since the ignition is only controlled by the chemical kinetics of the fuel. Therefore, this study investigates the effects of temperature and composition stratification strategies on the auto-ignition characteristics of NH3/H2/air mixtures under HCCI engine operating conditions with direct numerical simulation (DNS). 12 cases with different stratification strategies have been set under turbulent conditions. The chemical kinetics of NH3/H2/air was verified with the laminar flame speeds and ignition delay times. Results show that the temperature stratification can reduce the peak value of heat release rate (HRR), advance the ignition time and extend the combustion duration. In this case, the chemical reaction front is dominated by the deflagration or flame propagation mode. However, in contrast, composition stratification shows very limited effect on the overall combustion process, which is similar to homogeneous ignition and denoted as the spontaneous ignition mode. When increasing the hydrogen content in the fuel, the ignition time is obviously advanced and the peak of HRR is slightly increased. Higher NO emission is also observed which is mainly due to the increase of O, H, and OH intermediates to enhance the fuel NO production. Temperature stratification degree can improve the ignition process under both negatively correlated or unrelated T-Φ fields. However, the improvement is more evident for unrelated T-Φ condition when increasing the stratification degree.