A Physics-Based Modeling Approach of a Natural Gas HCCI Engine

2012 ◽  
Author(s):  
Marwa W. AbdelGawad ◽  
Reza Tafreshi ◽  
Reza Langari
Keyword(s):  
Internal Combustion Engines ◽  
Integral Model ◽  
Compression Ignition ◽  
Valve Closure ◽  
Nitric Oxides ◽  
Intake Valve ◽  
Ignition Timing ◽  
Hcci Engine ◽  
Main Challenge ◽  
Hcci Engines

Homogeneous Charge Compression Ignition (HCCI) Engines hold promises of being the next generation of internal combustion engines due to their ability to produce high thermal efficiencies, in addition to low nitric oxides and particulate matter. HCCI combustion is achieved through the auto-ignition of a compressed homogenous fuel-air mixture, thus making it a “fusion” between spark-ignition and compression-ignition engines. The main challenge in developing HCCI engines is the absence of a combustion trigger hence making the control of combustion timing difficult. To be able to control ignition timing, a physics-based model is developed to model the full HCCI engine cycle while taking into consideration cycle-to-cycle transitions. Exhaust Gas Recirculation is used to control combustion timing while the temperature at intake valve closure will serve as the parameter that represents the desired ignition timing. The Modified Knock Integral model defines the necessary relationship between ignition timing and temperature at intake valve closure. Validation of the developed model is performed by determining the ignition timing under varying conditions. Results are shown to be in accordance with data acquired from a single-cylinder model developed using a sophisticated engine simulation program, GT-Power.

Modelling and Simulation of Homogeneous Charge Compression Ignition Engine Fueled by Biodiesel

2018 ◽  
Author(s):  
Meshack Hawi ◽  
Mahmoud Ahmed ◽  
Shinichi Ookawara
Keyword(s):  
Heat Release ◽  
Compression Ratio ◽  
Homogeneous Charge Compression Ignition ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Emission Characteristics ◽  
Compression Ignition ◽  
Hcci Engine ◽  
Hcci Engines ◽  
Homogeneous Charge

Homogeneous charge compression ignition (HCCI) is a combustion technology which has received increased attention of researchers in the combustion field for its potential in achieving low oxides of nitrogen (NOx) and soot emission in internal combustion (IC) engines. HCCI engines have advantages of higher thermal efficiency and reduced emissions in comparison to conventional internal combustion engines. In HCCI engines, ignition is controlled by the chemical kinetics, which leads to significant variation in ignition time with changes in the operating conditions. This variation limits the practical range of operation of the engine. Additionally, since HCCI engine operation combines the operating principles of both spark ignition (SI) and compression ignition (CI) engines, HCCI engine parameters such as compression ratio and injection timing may vary significantly depending on operating conditions, including the type of fuel used. As such, considerable research efforts have been focused on establishing optimal conditions for HCCI operation with both conventional and alternative fuels. In this study, numerical simulation is used to investigate the effect of compression ratio on combustion and emission characteristics of an HCCI engine fueled by pure biodiesel. Using a zero-dimensional (0-D) reactor model and a detailed reaction mechanism for biodiesel, the influence of compression ratio on the combustion and emission characteristics are studied in Chemkin-Pro. Simulation results are validated with available experimental data in terms of incylinder pressure and heat release rate to demonstrate the accuracy of the simulation model in predicting the performance of the actual engine. Analysis shows that an increase in compression ratio leads to advanced and higher peak incylinder pressure. The results also reveal that an increase in compression ratio produces advanced ignition and increased heat release rates for biodiesel combustion. Emission of NOx is observed to increase with increase in compression ratio while the effect of compression ratio on emissions of CO, CO2 and unburned hydrocarbon (UHC) is only marginal.

scholarly journals Homogeneous Charge Compression Ignition Combustion: Challenges and Proposed Solutions

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Mohammad Izadi Najafabadi ◽  
Nuraini Abdul Aziz
Keyword(s):  
Homogeneous Charge Compression Ignition ◽  
Fuel Efficiency ◽  
Operating Conditions ◽  
Future Research ◽  
Compression Ignition ◽  
Ignition Timing ◽  
Ic Engine ◽  
Hcci Engine ◽  
Wide Range ◽  
Homogeneous Charge

Engine and car manufacturers are experiencing the demand concerning fuel efficiency and low emissions from both consumers and governments. Homogeneous charge compression ignition (HCCI) is an alternative combustion technology that is cleaner and more efficient than the other types of combustion. Although the thermal efficiency andNOxemission of HCCI engine are greater in comparison with traditional engines, HCCI combustion has several main difficulties such as controlling of ignition timing, limited power output, and weak cold-start capability. In this study a literature review on HCCI engine has been performed and HCCI challenges and proposed solutions have been investigated from the point view ofIgnition Timingthat is the main problem of this engine. HCCI challenges are investigated by many IC engine researchers during the last decade, but practical solutions have not been presented for a fully HCCI engine. Some of the solutions are slow response time and some of them are technically difficult to implement. So it seems that fully HCCI engine needs more investigation to meet its mass-production and the future research and application should be considered as part of an effort to achieve low-temperature combustion in a wide range of operating conditions in an IC engine.

Cyclic Variations of Ignition Timing in an HCCI Engine

2007 ◽  
Author(s):  
Mahdi Shahbakhti ◽  
Robert Lupul ◽  
Charles Robert Koch
Keyword(s):  
Experimental Data ◽  
Intake Manifold ◽  
Compression Ignition ◽  
Ignition Timing ◽  
Cyclic Variability ◽  
Auto Ignition ◽  
Hcci Engines ◽  
Cyclic Variations ◽  
And Control ◽  
Operating Points

Understanding the effect of modifying the properties of the engine charge on the cyclic variations of ignition timing is one essential aspect of being able to predict and control the ignition timing in Homogeneous Charge Compression Ignition (HCCI) engines. This paper investigates cyclic variability of HCCI ignition timing using the experimental data from two different engines at over 300 operating points for five different blends of iso-octane and n-heptane. Experimental results indicate that the cyclic variations of HCCI auto-ignition timing decrease with an increase in the intake manifold temperature and mixture richness, but it increases with an increase in the EGR rate.

A Theoretical Study on Performance and Combustion Characteristics of HCCI Engine Operation With Diesel Surrogate Fuels: n-Heptane, Dimethyl Ether

2008 ◽  
Author(s):  
Seyed Navid Shahangian ◽  
Mojtaba Keshavarz ◽  
Ghasem Javadirad ◽  
Nader Bagheri ◽  
Seyed Ali Jazayeri
Keyword(s):  
Dimethyl Ether ◽  
Diesel Fuel ◽  
Alternative Fuels ◽  
Internal Combustion Engines ◽  
High Efficiency ◽  
Main Stage ◽  
Engine Operation ◽  
Hcci Engine ◽  
Second Stage ◽  
Hcci Engines

HCCI engines have low emission and high efficiency values compared to the conventional internal combustion engines. These engines can operate on most alternative fuels such as dimethyl ether (DME), which has been tested as a possible diesel fuel for its simultaneously reduced NOx and PM emissions. HCCI combustion of both DME and n-heptane fuels display a distinct two-stage ignition reaction with the first stage taking place at fairly low temperatures and the second stage taking place at high temperatures. The second stage is responsible for the main stage of the heat release process. In this study, a single-zone, zero-dimensional, thermo-kinetic combustion model has been developed. MATLAB software is used to predict engine performance characteristics of HCCI engines using two types of diesel fuel: Dimethyl ether and N-heptane. The effects of intake temperature and pressure, fuel loading and addition of EGR gases on auto-ignition characteristics, optimum combustion phasing, and performance of the HCCI engines are considered in this study. Simultaneous effects of these variables for finding the most appropriate regime of HCCI engine operation, considering knock and misfire boundaries, are also investigated.

scholarly journals Microphones and Knock Sensors for Feedback Control of HCCI Engines

2004 ◽  
Author(s):  
Jason S. Souder ◽  
J. Hunter Mack ◽  
J. Karl Hedrick ◽  
Robert W. Dibble
Keyword(s):  
Fuel Injection ◽  
Compression Ignition ◽  
Cylinder Pressure ◽  
Indirect Methods ◽  
Loop Control ◽  
Hcci Engine ◽  
Hcci Engines ◽  
Timing Data ◽  
Knock Sensor ◽  
Direct Fuel Injection

Homogeneous charge compression ignition (HCCI) engines lack direct in-cylinder mechanisms, such as spark plugs or direct fuel injection, for controlling the combustion timing. Many indirect methods have been used to control the combustion timing in a HCCI engine. With any indirect method, it is important to have a measure of the combustion timing so the control inputs can be adjusted for the next cycle. In this paper, it is shown that microphones and knock sensors can be used to detect combustion in HCCI engines. The output from various microphones and a knock sensor on an HCCI engine are measured at light and high loads. The combustion timing data obtained from the sensors are compared to the combustion timing data obtained from a piezoelectric cylinder pressure transducer. One of these sensors is selected and used for closed-loop control of the combustion timing in a single cylinder HCCI engine.

Numerical Analysis of Biogas Composition Effects on Combustion Parameters and Emissions in Biogas Fueled HCCI Engines for Power Generation

2011 ◽  
Author(s):  
Iva´n D. Bedoya ◽  
Samveg Saxena ◽  
Francisco J. Cadavid ◽  
Robert W. Dibble
Keyword(s):  
Numerical Model ◽  
Power Output ◽  
Internal Combustion Engines ◽  
Numerical Results ◽  
Experimental Results ◽  
Combustion Stability ◽  
Absolute Pressure ◽  
Nox Emissions ◽  
Hcci Engine ◽  
Hcci Engines

This study investigates the effects of biogas composition on combustion stability for a purely biogas fueled HCCI engine. Biogas is one of the most promising renewable fuels for Combined Heat and Power systems driven by internal combustion engines. However, the high content of CO2 in biogas composition leads to low thermal efficiencies in spark ignited and dual fuel compression ignited engines. The study is divided into two parts: first experimental results on a biogas-fueled HCCI engine are used to validate a numerical model, and second the model is used to investigate how biogas composition impacts combustion stability. In the first part of the study, experimental analysis of a 4 cylinder, 1.9 L Volkswagen TDI Diesel engine running with biogas in HCCI mode has shown high gross indicated mean effective pressure (close to 8 bar), high gross indicated efficiency (close to 45%) and ultra-low NOx emissions below the US2010 limit (0.27 g/kWh). An inlet absolute pressure of 2 bar and inlet temperature of 473 K (200°C) were required for allowing HCCI combustion with a biogas composition of 60% CH4 and 40% CO2 on a volumetric basis. However, slight changes in inlet pressure and temperature caused large changes in cycle-to-cycle variations at low equivalence ratios and large changes in ringing intensity at high equivalence ratios. A numerical model is validated against these experimental results. In the second part of the study, the numerical results for varied biogas composition show that at high load limit, higher contents of CH4 in biogas composition allow advanced combustion and increased burning rates of the biogas air mixture. Higher contents of CO2 in biogas composition allow lowered ringing intensities with moderate decrease in the indicated efficiency and power output. NOx emissions are not highly affected by biogas composition, while CO and HC emissions tend to increase with higher contents of CO2. According with the numerical results, biogas composition is an effective strategy to control the onset of combustion and combustion phasing of HCCI engines running biogas, allowing more stabilized combustion at low equivalence ratios and safe operation at high equivalence ratios. The main advantages of using biogas fueled HCCI engines in CHP systems are the low sensitivity of power output and indicated efficiency to biogas composition, as well as the ultra low NOx emissions achieved for all tested compositions.

Modeling Cylinder-to-Cylinder Coupling in Multi-Cylinder HCCI Engines Incorporating Reinduction

2007 ◽  
Author(s):  
Anup M. Kulkarni ◽  
Gayatri H. Adi ◽  
Gregory M. Shaver
Keyword(s):  
Internal Combustion Engines ◽  
Control Strategies ◽  
Combustion Products ◽  
Exhaust Manifold ◽  
Gas Temperature ◽  
Subtle Difference ◽  
Hcci Engine ◽  
Variable Valve Actuation ◽  
Hcci Engines ◽  
Valve Actuation

Residual-affected homogeneous charge compression ignition (HCCI) is a promising strategy for decreasing fuel consumption and NOx emissions in internal combustion engines. One practical approach for achieving residual-affected HCCI is by using variable valve actuation to reinduct previously exhausted combustion products. This process inherently couples neighboring engine cylinders as products exhausted by one cylinder may be reinducted by a neighboring one. In order to understand this coupling and its implication for controlling HCCI, this paper outlines a simple physics based model of a multi-cylinder HCCI engine using exhaust reinduction. It is based on a physics based model previously validated for a single cylinder, multi mode HCCI engine. The exhaust manifold model links exhaust gases from one cylinder to those of the other cylinders and also simulates the effect of exhaust reinduction from the previous cycle. Depending on the exhaust manifold geometry and orientation, the heat transfer in the manifold causes a difference in the temperature of the re-inducted product gas across the cylinders. The results show that a subtle difference in the re-inducted exhaust gas temperature results in a dramatic variation in combustion timing (approx. 3 degrees). This model provides a basis for understanding the steady state behavior and also for developing control strategies for multi-cylinder HCCI engines. The paper presents exhaust valve timing induced compression ratio modulation (via flexible valve actuation) as one of the approaches to mitigate the imbalance in combustion timing across cylinders.

Numerical Analysis of a Six-Stroke Gasoline Compression Ignition (GCI) Engine Combustion With Continuously Variable Valve Duration (CVVD) Control

2018 ◽  
Author(s):  
Oudumbar Rajput ◽  
Youngchul Ra ◽  
Kyoung-Pyo Ha ◽  
You-sang Son
Keyword(s):  
Engine Performance ◽  
Combustion Efficiency ◽  
Power Stroke ◽  
Compression Ignition ◽  
Intake Valve ◽  
Ignition Timing ◽  
Engine Operation ◽  
Wide Range ◽  
Variable Valve ◽  
Valve Overlap

Engine performance and emissions of a six-stroke Gasoline Compression Ignition (GCI) engine with wide range of Continuously Variable Valve Duration (CVVD) control were numerically investigated at low engine load conditions. For the simulations, an in-house 3-D CFD code with high fidelity physical sub-models was used and the combustion and emissions kinetics were computed using a reduced kinetics mechanism for a 14-component gasoline surrogate fuel. Double injections were employed to effectively form the local fuel/air mixtures with optimal reactivity. Several valve timing and duration variations through the CVVD control were considered under both positive valve overlap (PVO) and negative valve overlap (NVO) conditions. Effects of intake-valve re-breathing between the first expansion and the second compression strokes were also investigated. Close attention was paid to understand the effects of two additional strokes of the engine cycle on the thermal and chemical conditions of charge mixtures that alter ignition, combustion and energy recovery processes. Double injections were found to be necessary to effectively utilize the additional two strokes for the combustion of overly mixed lean charge mixtures during the second power stroke (PS2). It was found that combustion phasing in both power strokes is effectively controlled by the intake valve closure (IVC) timing since it affects the effective compression ratio. Engine operation under NVO condition with fixed exhaust valve opening (EVO) and IVC timings tends to advance the ignition timing of the first power stroke (PS1) but has minimal effect on the ignition timing of PS2. Re-breathing was found to be an effective way to control the ignition timing in PS2 at a slight expense of the combustion efficiency. The operation of a six-stroke GCI engine could be successfully simulated and the operability range of the engine could be substantially extended by employing the CVVD technique. In addition, the control of valve timings could successfully control the thermodynamic and compositional conditions of in-cylinder mixtures that enable to control the combustion phasing.

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