Understanding the Effect of Wall Conditions and Engine Geometry on Thermal Stratification and HCCI Combustion

2014 ◽  
Author(s):  
Benjamin Lawler ◽  
Satyum Joshi ◽  
Joshua Lacey ◽  
Orgun Guralp ◽  
Paul Najt ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Heat Release ◽  
Wall Temperature ◽  
Compression Ratio ◽  
Thermal Stratification ◽  
Ceramic Coatings ◽  
Combustion Efficiency ◽  
Noticeable Effect ◽  
Hcci Engine ◽  
Hcci Combustion

Thermal stratification of the unburned charge in the cylinder has a profound effect on the burn characteristics of a Homogeneous Charge Compression Ignition (HCCI) engine. Experimental data was collected in a single cylinder, gasoline-fueled, HCCI engine in order to determine the effects of combustion chamber geometry and wall conditions on thermal stratification and HCCI combustion. The study includes a wall temperature sweep and variations of piston top surface material, piston top geometry, and compression ratio. The data is processed with a traditional heat release routine, as well as a post-processing tool termed the Thermal Stratification Analysis, which calculates an unburned temperature distribution from heat release. For all of the sweeps, the 50% burned point was kept constant by varying the intake temperature. Keeping the combustion phasing constant ensures the separation of the effects of combustion phasing from the effects of wall conditions alone on HCCI and thermal stratification. The results for the wall temperature sweep show no changes to the burn characteristics once the combustion phasing has been matched with intake temperature. This result suggests that the effects of wall temperature on HCCI are mostly during the gas-exchange portion of the cycle. The ceramic coatings were able to very slightly decrease the thermal width, increase the burn rate, increase the combustion efficiency, and decrease the cumulative heat loss. The combustion efficiency increased with the lower surface area to volume ratio piston and the lower compression ratio. Lastly, the compression ratio comparison showed a noticeable effect on the temperature distribution due to the effect of pressure on ignition delay, and the variation of TDC temperature required to match combustion phasing.

Development of a Postprocessing Methodology for Studying Thermal Stratification in an HCCI Engine

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Benjamin Lawler ◽  
Mark Hoffman ◽  
Zoran Filipi ◽  
Orgun Güralp ◽  
Paul Najt
Keyword(s):  
Mass Fraction ◽  
Thermal Stratification ◽  
Reaction Rates ◽  
Combustion Efficiency ◽  
Temperature Fields ◽  
Coolant Temperature ◽  
Analysis Tool ◽  
Gas Temperature ◽  
Hcci Engine ◽  
Mass Distributions

Naturally occurring thermal stratification significantly impacts the characteristics of homogeneous charge compression ignition (HCCI) combustion. The in-cylinder gas temperature distributions prior to combustion dictate the ignition phasing, burn rates, combustion efficiency, and unburned hydrocarbon and CO emissions associated with HCCI operation. Characterizing the gas temperature fields in an HCCI engine and correlating them to HCCI burn rates is a prerequisite for developing strategies to expand the HCCI operating range. To study the development of thermal stratification in more detail, a new analysis methodology for postprocessing experimental HCCI engine data is proposed. This analysis tool uses the autoignition integral in the context of the mass fraction burned curve to infer information about the distribution of temperature that exists in the cylinder prior to combustion. An assumption is made about the shape of the charge temperature profiles of the unburned gas during compression and after combustion starts elsewhere in the cylinder. Second, it is assumed that chemical reaction rates proceed very rapidly in comparison to the staggering of ignition phasing from thermal stratification. The autoignition integral is then coupled to the mass fraction burned curve to produce temperature-mass distributions that are representative of a particular combustion event. Due to the computational efficiency associated with this zero-dimensional calculation, a large number of zones can be simulated at very little computational expense. The temperature-mass distributions are then studied over a coolant temperature sweep. The results show that very small changes to compression heat transfer can shift the distribution of mass and temperature in the cylinder enough to significantly affect HCCI burn rates and emissions.

scholarly journals Simulation of predictive kinetic combustion of single cylinder HCCI engine

2020 ◽  
Author(s):  
Ibham Veza ◽  
Mohd Farid Muhamad Said ◽  
Zulkarnain Abdul Latiff ◽  
Mohd Faizal Hasan ◽  
Rifqi Irzuan Abdul Jalal ◽  
...  
Keyword(s):  
Heat Release ◽  
Air Temperature ◽  
Engine Performance ◽  
Zone Model ◽  
Hcci Engine ◽  
Hcci Combustion ◽  
Temperature Heat ◽  
Performance And Emissions ◽  
Improved Performance ◽  
Start Of Combustion

Homogeneous Charge Compression Ignition (HCCI) engine has attracted great attention due to its improved performance and emissions compared to conventional engines. It can reduce both Nitrogen Oxides (NOx) and Particulate Matter (PM) emissions simultaneously without sacrificing the engine performance. However, controlling its combustion phasing remains a major challenge due to the absence of direct control mechanism. The start of combustion is entirely initiated by the chemical reactions inside the combustion chamber, resulted from the compression of its homogeneous mixtures. Varying some critical engine parameters can play a significant role to control the combustion phasing of HCCI engine. This paper investigates the characteristics of HCCI combustion fuelled with n-heptane (C7H16) using single-zone model computational software. The model enabled the combustion object to vary from cycle to cycle. Detailed simulations were conducted to evaluate the effects of air fuel ratio (AFR), compression ratio (CR) and intake air temperature on the in-cylinder pressure and heat release rate. The simulation results showed that the single-zone model was able to predict the two-stage kinetic combustion of HCCI engine; the Low Temperature Heat Release (LTHR) and the High Temperature Heat Release (HTHR) regions. It was found that minor changes in AFR, CR and inlet air temperature led to major changes in the HCCI combustion phasing.

On the Effects of Injection Strategy, EGR, and Intake Boost on TSCI With Wet Ethanol

2019 ◽  
Author(s):  
Brian Gainey ◽  
Ziming Yan ◽  
Mozhgan Rahimi-Boldaji ◽  
Benjamin Lawler
Keyword(s):  
Heat Release ◽  
Thermal Stratification ◽  
Equivalence Ratio ◽  
Combustion Efficiency ◽  
Split Injection ◽  
Load Range ◽  
Release Process ◽  
Injection Strategy ◽  
Compression Stroke ◽  
The Impact

Abstract Using a split injection of wet ethanol, where a portion of the fuel is injected during the compression stroke, has been shown to be an effective way to enable thermally stratified compression ignition (TSCI), an advanced, low temperature combustion (LTC) mode that aims to control the heat release process by enhancing thermal stratification, thereby extending the load range of LTC. Wet ethanol is the ideal fuel candidate to enable TSCI because it has a high latent heat of vaporization and low equivalence ratio sensitivity. Previous work has shown “early” compression stroke injections (−150 to −100 deg aTDC) have the potential to control the start of combustion while “mid” compression stroke injections (−90 to −30 deg aTDC) have the potential to control in-cylinder thermal stratification, thereby controlling the heat release rate. In this work, a mixture of 80% ethanol and 20% water by mass is used to further study the injection strategy of TSCI combustion. Additionally, the impact of external, cooled exhaust gas recirculation (EGR) and intake boost level on the effectiveness of a split injection of wet ethanol to control the heat release process are investigated. It was found that neither external, cooled EGR, nor intake boost level has any impact on the effectiveness of the compression stroke injection(s) at controlling the burn rate of TSCI. It was also seen that external, cooled EGR has the potential to increase the overall tailpipe combustion efficiency, while intake boost has the potential to decrease NOx emissions at the expense of combustion efficiency by lowering the global equivalence ratio.

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.

Experimental Research on Combustion and Emission Performance for Micro Combustor of MTPV System with Stratified Porous Media

2012 ◽  
Vol 608-609 ◽  
pp. 934-940
Author(s):  
Jian Wu ◽  
Bo Li ◽  
Bin Xu ◽  
Jia Xuan Miao
Keyword(s):  
Porous Media ◽  
Temperature Distribution ◽  
Band Gap ◽  
Experimental Research ◽  
Wall Temperature ◽  
Combustion Efficiency ◽  
Critical Component ◽  
Uniform Temperature ◽  
The Past ◽  
Micro Combustor

As the critical component of the system, micro-combustor requires a high and uniform temperature distribution along the wall to meet demands for the band gap of the PV cells. The past experiments have proved that the peak wall temperature of the combustor with porous media increases obviously. This paper will have a research on stratified porous media to enhance the combustion efficiency of the combustor and reduce the emissions.

scholarly journals The Impact of Low Octane Primary Reference Fuel on HCCI Combustion Burn Rates: The Role of Thermal Stratification

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Luke Hagen ◽  
George Lavoie ◽  
Margaret Wooldridge ◽  
Dennis Assanis
Keyword(s):  
Heat Release ◽  
Thermal Stratification ◽  
Large Degree ◽  
Charge Composition ◽  
Experimental Conditions ◽  
Maximum Heat ◽  
Hcci Combustion ◽  
Primary Reference ◽  
Gas Recirculation ◽  
The Impact

A new experimental method was developed which isolated charge composition effects for wide levels of internal exhaust gas recirculation (iEGR) at constant total EGR (tEGR) for homogeneous charge compression ignition (HCCI) combustion. The effect of changing iEGR was examined for both gasoline (research octane number (RON) = 90.5) and PRF40 at constant charge composition at multiple engine speeds. For this study, the charge composition was defined as the total mass of fresh air, fuel, and tEGR. Experimental results showed that for a given iEGR level, PRF40 had a reduced burn duration and higher maximum heat release rate (HRR) when compared with gasoline. PRF40 was found to have a nearly constant burn duration and HRR for a given load and CA50, largely independent of engine speed and iEGR level. Gasoline, for equivalent conditions, showed an increased burn duration at higher iEGR levels. When comparing PRF40 to gasoline at fixed combustion phasing and iEGR level, the increased HRR for PRF40 was correlated with reduced intake valve closing (IVC) temperatures. To examine the impact of thermal gradients (as distinct from fuel chemistry effects) due to IVC temperature differences, a multizone “balloon model” was used to evaluate experimental conditions. The model results demonstrated that when the in-cylinder temperature profiles between fuels were matched by adjusting wall temperature, the heat release rates were nearly identical. This result suggested the observed differences in burn rates between gasoline and PRF40 were influenced to a large degree by differences in thermal stratification and to a lesser extent by differences in fuel chemistry.

Study of Pulse Spray, Heat Release, Emissions and Efficiencies in a Compound Diesel HCCI Combustion Engine

2004 ◽  
Author(s):  
Wanhua Su ◽  
Xiaoyu Zhang ◽  
Tiejian Lin ◽  
Yiqiang Pei ◽  
Hua Zhao
Keyword(s):  
Heat Release ◽  
Combustion Engine ◽  
Combustion Efficiency ◽  
Diffusion Combustion ◽  
Injection Timing ◽  
Nox Emissions ◽  
Injection Process ◽  
Hcci Combustion ◽  
Air Mixing ◽  
Combustion Technology

A compound diesel HCCI combustion technology has been developed based on the combustion strategies of combination of controlled premixed charge compression ignition (CPCCI) through multi-injections and lean diffusion combustion (LDC) organized by a mixing enhanced combustion chamber. The purpose of this paper is to investigate the fuel spray evolution during multi-injections, heat release mode, thermo-efficiency and exhaust emissions from the compound combustion. In this work, the STAR-CD based, multidimensional modeling is employed to improve the understanding and assist the optimization of the multiple injection process. The parameters explored include the effects of injection timing, dwell time, and the pulse width. Insight generated from these studies provides guidelines on designing an injection profile for optimization of fuel-air mixing. By comparison of different heat release modes of conventional diesel combustion, the pure HCCI combustion and the compound HCCI combustion, the engine heat release can be summarized as forward concentrated mode (FC mode), post concentrated mode (PC mode) and dispersed mode (DS mode). The FC mode gives the highest thermo-efficiency but with highest NOx emissions. The PC mode gets lower NOx emissions but with the drawback of lower thermo-efficiency and higher soot emissions. The DS mode is a flexible heat release mode created by the compound HCCI combustion. A typical DS mode reveals two equivalent peaks of heat release. The first peak represents the CPCCI combustion and the later peak represents the lean diffusion combustion. The thermo-efficiency in a DS mode can reach approximately as high as that in FC mode, while NOx and soot emission can be reduced simultaneously and remarkably. The combustion efficiency and the heat loss in different combustion mode are also discussed.

HCCI combustion with an actively controlled glow plug: The effects on heat release, thermal stratification, efficiency, and emissions

2018 ◽  
Vol 211 ◽  
pp. 809-819 ◽  
Author(s):  
Benjamin Lawler ◽  
Joshua Lacey ◽  
Orgun Güralp ◽  
Paul Najt ◽  
Zoran Filipi
Keyword(s):  
Heat Release ◽  
Thermal Stratification ◽  
Glow Plug ◽  
Hcci Combustion

scholarly journals The Effect of Iso-Octane Addition on Combustion and Emission Characteristics of a HCCI Engine Fueled With n-Heptane

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Cosmin E. Dumitrescu ◽  
Hongsheng Guo ◽  
Vahid Hosseini ◽  
W. Stuart Neill ◽  
Wallace L. Chippior ◽  
...  
Keyword(s):  
Combustion Efficiency ◽  
Liquid Volume ◽  
Emission Characteristics ◽  
Oxygenated Hydrocarbons ◽  
Hcci Engine ◽  
Fuel Blends ◽  
Hcci Combustion ◽  
Unburned Hydrocarbons ◽  
Unburned Fuel ◽  
Multizone Model

This paper investigates the effects of iso-octane addition on the combustion and emission characteristics of a single-cylinder, variable compression ratio, homogeneous charge compression ignition (HCCI) engine fueled with n-heptane. The engine was operated with four fuel blends containing up to 50% iso-octane by liquid volume at 900 rpm, 50:1 air-to-fuel ratio, no exhaust gas recirculation, and an intake mixture temperature of 30°C. A detailed analysis of the regulated and unregulated emissions was performed including validation of the experimental results using a multizone model with detailed fuel chemistry. The results show that iso-octane addition reduced HCCI combustion efficiency and retarded the combustion phasing. The range of engine compression ratios where satisfactory HCCI combustion occurred was found to narrow with increasing iso-octane percentage in the fuel. NOx emissions increased with iso-octane addition at advanced combustion phasing, but the influence of iso-octane addition was negligible once CA50 (crank angle position at which 50% heat is released) was close to or after top dead center. The total unburned hydrocarbons (THC) in the exhaust consisted primarily of alkanes, alkenes, and oxygenated hydrocarbons. The percentage of alkanes, the dominant class of THC emissions, was found to be relatively constant. The alkanes were composed primarily of unburned fuel compounds, and iso-octane addition monotonically increased and decreased the iso-octane and n-heptane percentages in the THC emissions, respectively. The percentage of alkenes in the THC was not significantly affected by iso-octane addition. Iso-octane addition increased the percentage of oxygenated hydrocarbons. Small quantities of cycloalkanes and aromatics were detected when the iso-octane percentage was increased beyond 30%.

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