Refine Your Search

Topic

Author

Search Results

Technical Paper

Alternative Fuels and Homogeneous Charge Compression Ignition Combustion Technology

1997-10-27
978449
Homogeneous charge compression ignition (HCCI) combustion requires high EGR rate and high intake temperature. HCCI combustion has not yet been made to operate at conditions other than low speed and low load in a four-stroke engine. Two stroke engine, however, have produced reasonable power in the HCCI combustion or active thermo-atmosphere combustion (ATAC) mode. In this paper, the nature of ATAC is discussed by spectroscopic observation to determine why the ATAC (under favorable condition) produces very low cyclic irregularity and low NO emission. ATAC low heat rejection engine and ATAC with alternative fuels are discussed.
Technical Paper

A Study on Adaptability of Alternative Fuels for Lean Burn Two-Stroke ATAC Engine

1997-10-27
978472
ATAC is “bulk-like” and/or “non-propagating” combustion caused by compression autoignition of premixture, and it is stable even in the lean region. And ATAC engine is expected to be an engine using alternative fuels which are difficult to apply to usual engines because of their low cetane number. In this study, a two-stroke ATAC engine test was carried out to evaluate an adaptability of alternative fuels for lean burn. Methanol, ethanol, DME, methane and propane were used as the test fuels, and the influence of fuel characteristics on autoignition timing, combustion duration and autoignition temperature were investigated in the lean region. Using oxygenated fuels, the lean limit of ATAC operation region shifts to lean side. ATAC autoignition temperature is not depend on equivalence ratio, delivery ratio and engine speed, and it is only decided by the kind of fuel. The order of the ATAC autoignition temperature is methanol, ethanol, DME, gasoline from lower side.
Technical Paper

An Investigation of the Effect of Thermal Stratification on HCCI Combustion by using Rapid Compression Machine

2007-07-23
2007-01-1870
A significant drawback to HCCI engines is the knocking caused by rapid increases in pressure. Such knocking limits the capacity for high-load operation. To solve this problem, thermal stratification in the combustion chamber has been suggested as possible solution. Thermal stratification has the potential to reduce the maximum value of the rate of pressure increase combustion by affecting the local combustion start time and extending the duration of combustion. The purpose of this study was to experimentally obtain fundamental knowledge about the effect of thermal stratification on the HCCI combustion process. Experiments were conducted in a rapid compression machine (RCM) equipped with a quartz window to provide optical access to the combustion chamber. The machine was fueled with DME, n-Butane, n-Heptane and iso-Octane, all of which are currently being investigated as alternative fuels and have different low temperature characteristics.
Technical Paper

An Investigation of Combustion Control Using EGR for Small and Light HCCI Engine Fuelled with DME

2007-07-23
2007-01-1876
The HCCI engine could offer low NOx, PM emissions and high efficiency. However the operation region of the HCCI combustion is limited because of the knocking at high load and the misfire at low load. Moreover the HCCI principle lacks direct combustion control and needs a system to control the combustion phasing with high accuracy. Today there exists various ways to control the HCCI combustion, such as Variable Valve Train, Variable Compression Ratio, Inlet Air Heating and Dual Fuels. However such variable mechanisms and Inlet Air Heating tend to be heavy and complex. Dual Fuels method needs two types of fuels and has a challenge in infrastructure. In this study, in order to develop a small and light HCCI engine, a simple HCCI combustion control system is proposed. DME (Di-methyl Ether) is used as the fuel to keep the structure small and light. In this system, the mixing ratio of three gases: stoichiometric pre-mixture, hot EGR gas and cold EGR gas is changed by only throttles.
Technical Paper

Analysis of the Effect of Eco-driving with Early Shift-up on Real-world Emission

2010-10-25
2010-01-2279
For the reduction of greenhouse gas emission in the transportation sector, various countermeasures against CO₂ emission have been taken. The eco-driving has been paid attention because of its immediate effect on the CO₂ reduction. Eco-driving is defined as a driving method with various driving techniques to save fuel economy. The eco-driving method has been promoted to the common drivers as well as the drivers of carriers. Additionally, there are many researches about improvement of fuel efficiency and CO₂ reduction. However, the eco-driving will have the reduction effect of CO₂ emission, the influence of the eco-driving on air pollutant emission such as NOx is not yet clear. In this study, the effect of the eco-driving on real-world emission has been analyzed using the diesel freight vehicle with the on-board measurement system.
Technical Paper

An Investigation on DME HCCI Engine about Combustion Phase Control using EGR Stratification by Numerical Analysis

2012-10-23
2012-32-0077
This work has been investigated the potential of in-cylinder EGR stratification for reducing the pressure rise rate of DME HCCI engines, and the coupling of both thermal stratification and fuel stratification. The numerical analyses were done by using five-zone version of CHEMKIN-II kinetics rate code, and kinetic mechanics for DME. The effects of inert components were used for the presence of EGR in calculation. Three cases of EGR stratification were tested on both thermal stratification and fuel stratification at the fixed initial temperature, pressure and fueling rate at BDC. In order to explore the appropriate stratification of EGR, EGR width was employed from zero to thirty percent. Firstly, EGR homogeneity case which means EGR width zero was examined. Secondly, EGR is located densely in hotter zone for combining with thermal stratification or in richer zone for a combination with fuel stratification. Lastly, the case was judged inversely with the second case.
Technical Paper

An Investigation of the Effects of Fuel Inhomogeneity on the Pressure Rise Rate in HCCI engine using Chemiluminescence Imaging

2010-09-28
2010-32-0097
Theoretically, homogeneous charge compression engines (HCCI) are able to grant a high thermal efficiency, as well as a low NOx and particulate emissions. This ability is mainly due to the combustion process, which, contrary to both Diesel and Gasoline engine, is homogeneous in time and space within the combustion chamber. But despite these advantages, the engine operating condition is limited by the narrow boundaries of misfire at low load and knocking at high load. For that matter, one of the numerous ways of overcoming knocking is to deliberately create fuel inhomogeneities within the combustion chamber, since it has proved to lengthen combustion duration and to drastically reduce maximum pressure rise rate (PRR). Nevertheless, though the global effects of fuel inhomogeneities on PRR have been studied, we lack information that explains this phenomenon.
Technical Paper

Combined Effects of Spark Discharge Pattern and Tumble Level on Cycle-to-Cycle Variations of Combustion at Lean Limits of SI Engine Operation

2017-03-28
2017-01-0677
Improving the thermal efficiency of spark ignition (SI) engine is strongly required due to its widespread use but considerably less efficiency than that of compression ignition (CI) engine. Although lean SI engine operation can offer substantial improvements of the thermal efficiency relative to that of traditional stoichiometric SI operation, the cycle-to-cycle variations of combustion increases with the level of air dilution, and becomes unacceptable. To improve the stability of lean operation, this study examines the effects of spark discharge pattern and tumble level on cycle-to-cycle variations of combustion at lean limits. The spark discharge pattern was altered by a custom inductive ignition system using ten spark coils and the tumble level was increased by a custom adapter installed in the intake port (tumble adapter).
Technical Paper

Surrounding Gas Effects on Soot Formation and Extinction - Observation of Diesel Spray Combustion Using a Rapid Compression Machine

1993-03-01
930603
A single action rapid compression machine was developed to observe the soot formation and oxidation processes in a diesel spray flame. Two color method was applied to analyze the flame temperature and KL factor from the flame image taken by high speed camera. Variation in gas oxygen concentration of the surrounding gas was achieved by adding different quantities of pure oxygen, nitrogen, carbon dioxide and argon gases to charged air within a range from 17 to 25 vol.% oxygen to examine the effects of the surrounding gas composition and the temperature, and of the flame temperature on soot formation and extinction. The initial gas temperature has much effect not only on the ignition but on soot formation speed. The higher oxygen concentration gives the higher flame temperature and the faster soot oxidation rate in the flame. Carbon dioxide has a soot reduction effect in spite of its lower flame temperature.
Technical Paper

Effects of Aromatics Content and 90% Distillation Temperature of Diesel Fuels on Flame Temperature and Soot Formation

2001-05-07
2001-01-1940
In this study, the effects of fuel properties, aromatics content and 90% distillation temperature T90, on flame temperature and soot formation were studied using a rapid compression machine (RCM). Aromatics content and T90 distillation temperature were parameters isolated from influence of each other, and from cetane number. A fuel spray was injected in the RCM combustion chamber by a single nozzle hole. The ignition and combustion processes of diesel spray were observed by a high-speed direct photography. Flame temperature and KL factor (which indicates the soot concentration), were analyzed by the two-color method. The rate of heat release was analyzed from indicated diagrams. The fuels with aromatics content showed higher flame temperature. The fuel with highest T90 distillation temperature showed highest flame temperature.
Technical Paper

Effect of Nozzle Diameter and EGR Ratio on the Flame Temperature and Soot Formation for Various Fuels

2001-05-07
2001-01-1939
In this study, effects of nozzle hole diameter and EGR ratio on flame temperature (indication of NO formation) and KL value (indication of soot formation) were investigated. Combustion of a single diesel fuel spray in the cylinder of a rapid compression machine (RCM) was analyzed. Three nozzles with different hole diameter were used corresponding to present, near term and long term heavy duty diesel engine specifications. EGR was simulated through 2%vol. CO2 addition to the inlet air and by increase of in-cylinder surrounding gas temperature. Various types of fuels were used in this. The ignition and combustion processes of diesel fuel spray were observed by a high-speed direct photography and by indicated pressure diagrams. Flame temperature and KL factor were analyzed by a two-color method. With larger nozzle hole diameters there are larger high temperature areas. With smaller nozzle hole diameters there is more soot formed. Introduction of 2% vol.
Technical Paper

Simulation Study of SI-HCCI Transition in a Two-Stroke Free Piston Engine Fuelled with Propane

2014-04-01
2014-01-1104
A simulation study was conducted to examine the transition from SI combustion to HCCI combustion in a two-stroke free piston engine fuelled with propane. Operation of the free piston engine was simulated based on the combination of three mathematical models including a dynamic model, a linear alternator model and a thermodynamic model. The dynamic model included an analysis of the piston motion, based on Newton's second law. The linear alternator model included an analysis of electromagnetic force, which was considered to be a resistance force for the piston motion. The thermodynamic model was used to analysis thermodynamic processes in the engine cycle, including scavenging, compression, combustion, and expansion processes. Therein, the scavenging process was assumed to be a perfect process. These mathematical models were combined and solved by a program written in Fortran.
Technical Paper

Numerical Analysis of Auto Ignition and Combustion of n-Butane and Air Mixture in the Homogeneous Charge Compression Ignition Engine by Using Elementary Reactions

2003-03-03
2003-01-1090
The combustion mechanism of the homogeneous charge compression ignition (HCCI) engine has been investigated by numerical calculations. Calculations were carried out using n-butane/air elementary reactions at 0 dimension and adiabatic condition to simplify the understanding of chemical reaction mechanisms in the HCCI engine without complexities of walls, crevices, and mixture inhomogeneities. n-Butane is the fuel with the smallest carbon number in the alkane family that shows two-stage auto-ignition, heat release with low temperature reaction (LTR) and high temperature reaction (HTR), similar to higher hydrocarbons such as gasoline at HCCI combustion. The CHEMKIN II code, SENKIN and kojima's n-butane elementary reaction scheme were used for the calculations. This paper consists of three main topics. First, the heat release mechanisms of the HCCI engine were investigated. The results show that heat release with LTR is HCHO oxidation reactions.
Technical Paper

Numerical Simulation of Auto-Ignition and Combustion of n-Butane and Air Mixtures in a 4 Stroke HCCI Engine by Using Elementary Reactions

2000-06-19
2000-01-1834
HCCI (Homogeneous Charge Compression Ignition) engine is expected to a new engine to be high efficiency and low emission. But it is difficult to control ignition timing and combustion duration, because ignition and combustion mainly depend on oxidation process of fuel. In this study, the focus is to clear the combustion mechanism of auto-ignition engine. By calculating chemical kinetics of elementary reactions, effects of compression speed, equivalence ratio, initial temperature and compression ratio on auto-ignition were investigated. And also, behaviors of chemical species under auto-ignition process were cleared.
Technical Paper

The Research about Thermal Stratification Effect on Pressure Rise Rate in Supercharged HCCI Engine based on Numerical Analysis

2009-11-03
2009-32-0141
The HCCI engine is a next generation engine, with high efficiency and low emissions. However a rate of pressure rise is a major limitation for high load range. Recently, we are able to reduce the rate of pressure rise using thermal stratification. Nevertheless, this was insufficient to produce high power. Without the higher equivalent ratio, one way to improve the power is to increase the intake boost pressure. It is suggested that the rate of pressure rise is reduced by thermal stratification and the power is increased by boost pressure at the same time. The objective of this work is to understand the characteristics of combustion, knock and emissions for using both thermal stratification and the boost pressure. The calculations are performed by CHEMKIN and modified SENKIN. As a result of increasing the boost pressure, a higher IMEP was attained while the rate of pressure rise increased only slightly in the HCCI with thermal stratification.
Technical Paper

An Investigation of the Potential of Thermal and Mixing Stratifications for Reducing Pressure Rise Rate on HCCI Combustion by using Rapid Compression Machine

2009-11-03
2009-32-0085
Thermal and mixing stratifications have been thought as one of the ways to avoid an excessive pressure rise on HCCI combustion. The purpose of this research is to investigate the potential of thermal and mixing stratifications for reducing PRR (Pressure Rise Rate) on HCCI combustion. The pre-mixture with thermal and mixing stratifications is charged in RCM (Rapid Compression Machine). After that, the pre-mixture is compressed and in that process, in-cylinder gas pressure and chemiluminescence images are obtained and analyzed. Furthermore, experimental results are compared with the computational results calculated by using multi-zone model for analyzing these mechanisms.
Technical Paper

Analysis of the combustion dispersion mechanism in HCCI Engine

2009-11-03
2009-32-0086
Delaying CA50(Crank Angle of 50% Heat Release) of the HCCI engine to expansion stroke can lead to high indicated thermal efficiency as well as the avoidance of knocking. However, this method could induce the problem of cycle variability. In this study, the cycle-to-cycle variation of a HCCI engine fueled with DME was investigated. Experimental parameters of each cycle, such as in-cylinder temperature, pressure and gas flow rate, were recorded by fast response system, and analyzed consequently. Moreover, the interdependency between the combustion and the performance parameters were evaluated.
Technical Paper

Mechanism Analysis of Influence of Engine Speed on HCCI Combustion by using Numerical Calculation

2009-11-03
2009-32-0087
In HCCI Engine, HCCI combustion characteristics come under the influence of change of compression speed corresponding to engine speed. The purpose of this study is to investigate mechanism of influence of engine speed on HCCI combustion characteristics by using numerical analysis. At first, the Influence of engine speed was showed. And then, In order to clarified the mechanism of influence of engine speed, results of kinetics computations were analyzed to investigate the elementary reaction path for heat release at transient temperatures by using contribution matrix.
Technical Paper

A Study of Fuel and EGR Stratification to Reduce Pressure-Rise Rates in a HCCI Engine

2013-10-15
2013-32-9070
Problem of HCCI combustion is knocking due to a steep heat release by the ignition that is occurred in each local area at the same time. It is considered that dispersion of auto-ignition timing at each local area in the combustion chamber is necessary to prevent this problem. One of technique of this solution is to make thermal stratification. It could be made by using two-stage ignition fuel, which has large heat release at low temperature reaction. Dispersion of fuel concentration leads to difference of temperature histories while combustion phasing is dispersed at each local area. Also, EGR gas stratification could make difference of temperature histories at each local area because of that of the characteristics. This study examines the effect of mixing stratification by stratifying the charge of fuel and CO2. A single-cylinder engine equipped with optical access was used in experiments, and numerical analysis was executed.
Technical Paper

Potential of Stratification Charge for Reducing Pressure-Rise Rate in HCCI Engines Based on Multi-Zone Modeling and Experiments by using RCM

2013-10-15
2013-32-9083
The charge stratification has been thought as one of the ways to reduce the sharp pressure rises of HCCI combustion. The objective of this study is to evaluate the potential of equivalence ratio, initial temperature, and EGR gas stratifications for reducing pressure-rise rate of HCCI combustion. Using rapid compression machine, the stratified pre-mixture is charged, and compressed to analyze the change of in-cylinder gas pressure and temperature traces during compression process. Based on the experiment results, numerical calculations by CHEMKIN are conducted to more specifically analyze the potential of equivalence ratio, initial temperature, and EGR gas stratifications on the reduction of pressure rise rate. Multi-zone model is used to simulate the thermal stratification, fuel stratification and EGR gas stratification of in-cylinder charge as like real engine.
X