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In this study, the influence of fuel premixing ratio (PMR) on the performance, combustion, and emission characteristics of dual-fuel operation in the compression ignition (CI) engine have been investigated. For dual fuel operation in CI-engine, two fuels of different reactivity are utilized in the same combustion cycle. In this study, low reactivity fuels (gasoline/butanol) is injected into the intake manifold, and high reactivity fuel (diesel) is directly injected into the cylinder. To operate the conventional CI engine in dual-fuel mode, the intake manifold of the engine was modified and a solenoid based port fuel injector was installed. A separate port fuel injector controller was used for injecting the gasoline or butanol. Suitable instrumentation was used to measure in-cylinder pressure and exhaust gas emissions. Experiments were performed by maintaining the constant fuel energy at different fuel PMR for different engine loads at constant engine speed.

In the present work, the in-cylinder tumble/swirl flow and its effect on the homogeneity, turbulence, and combustion of methane are investigated in a canted valve engine using ANSYS. The study is focused on the impact of initial swirl and tumble on the charge preparation, turbulent kinetic energy, and combustion of methane. The flow simulation was performed in ANSYS using hybrid mesh for cold flow simulation to study the tumble/swirl flow variation. For combustion simulation, a 2D axisymmetric model was used with an initial swirl and tumble ratio for studying the effect on premixed combustion. The flow simulation was performed for suction and compression to see the variation in the swirl and tumble with crank position and engine speed. The combustion simulation was performed only for compression and power stroke to save the computation time. The results depict that the flow inside the cylinder plays a significant role in the preparation of a homogeneous charge.

Homogenous charge compression ignition (HCCI) combustion emerged as a potential technique for reducing automotive pollution. Controlling the combustion timing at different engine operating conditions is one of the major challenges for the commercial application of HCCI combustion engines. To control HCCI ignition timing, it is often necessary to know the characteristics of HCCI cyclic variations. In this study, cyclic combustion variations in an HCCI engine are analyzed. Combustion stability and cycle-to-cycle variations of HCCI combustion parameters were investigated on a modified four-stroke diesel engine. The experiments were conducted by varying intake air temperatures and relative air-fuel ratios at constant engine speed. In the steady-state engine operating condition, in-cylinder pressure signals of 2000 consecutive engine combustion cycles are acquired for each test condition.

This paper presents the experimental investigation of combustion stability and nano-particle emissions from the CNG-diesel RCCI engine. A modified automotive diesel engine is used to operate in RCCI combustion mode. An open ECU is used to control the low and high reactivity fuel injection events. The engine is tested for fixed engine speed and two different engine load conditions. The tests performed for various port-injected CNG masses and diesel injection timings, including single and double diesel injection strategy. Several consecutive engine cycles are recorded using in-cylinder combustion pressure measurement system. Statistical and return map techniques are used to investigate the combustion stability in the CNG-diesel RCCI engine. Differential mobility spectrometer is used for the measurement of particle number concentration and particle-size and number distribution. It is found that advanced diesel injection timing leading to higher cyclic combustion variations.

New combustion concepts developed in internal combustion engines such as homogeneous charge compression ignition (HCCI) have attracted serious attention due to the possibilities to simultaneously achieve higher efficiency and lower emissions, which will impact the environment positively. The HCCI combustion concept has potential of ultra-low NOX and particulate matter (PM) emission in comparison to a conventional gasoline or a diesel engine. Environmental Legislation Agencies are becoming increasingly concerned with particulate emissions from engines because the health and environmental effects of particulates emitted are now known and can be measured by sophisticated instruments. Particulate emissions from HCCI engines have been usually considered negligible, and the measurement of mass emission of PM from HCCI combustion systems shows their negligible contribution to PM mass. However some recent studies suggest that PM emissions from HCCI engines cannot be neglected.

Homogeneous charge compression ignition (HCCI) engines are attracting attention as next-generation internal combustion engines mainly because of very low NOx and PM emission potential and excellent thermal efficiency. Particulate emissions from HCCI engines have been usually considered negligible however recent studies suggest that PM number emissions from HCCI engines cannot be neglected. This study is therefore conducted on a modified four cylinder diesel engine to investigate this aspect of HCCI technology. One cylinder of the engine is modified to operate in HCCI mode for the experiments and port fuel injection technique is used for preparing homogenous charge in this cylinder. Experiments are conducted at 1200 and 2400 rpm engine speeds using gasoline, ethanol, methanol and butanol fuels. A partial flow dilution tunnel was employed to measure the mass of the particulates emitted on a pre-conditioned filter paper.

The development of vehicles continues to be determined by increasingly stringent emissions standards including CO2 emissions and fuel consumption. To fulfill the simultaneous emission requirements for near zero pollutant and low CO2 levels, which are the challenges of future powertrains, many research studies are currently being carried out world over on new engine combustion process, such as Controlled Auto Ignition (CAI) for gasoline engines and Homogeneous Charge Compression Ignition (HCCI) for diesel engines. In HCCI combustion engine, ignition timing and combustion rates are dominated by physical and chemical properties of fuel/air/residual gas mixtures, boundary conditions including ambient temperature, pressure, and humidity and engine operating conditions such as load, speed etc.

The homogeneous charge compression ignition (HCCI) combustion process is capable of providing both high ‘diesel-like’ efficiencies and very low NOx and particulate emissions. However, among several technical challenges, controlling the combustion phasing, particularly during transients is a major issue, which must be resolved to exploit its commercial applications. This study is focused on the experimental investigations of behavior of combustion timing and other combustion parameters during startup and load transients. The study is conducted on a gasoline fuelled HCCI engine by varying intake air temperature and air-fuel ratio at different engine speeds. Port fuel injection technique is used for preparing homogeneous mixture of gasoline and air. For fueling startup transient test, fuel injection was turned off, and the engine was motored for several minutes until the fire-deck, intake and exhaust temperatures stabilized.

Homogeneous Charge Compression Ignition (HCCI) offers great promise for excellent fuel economy and extremely low emissions of NOx and PM. HCCI combustion lacks direct control on the "start of combustion" such as spark timing in SI engines and fuel injection timing in CI engines. Auto ignition of a homogeneous mixture is very sensitive to operating conditions of the engine. Even small variations of the load can change the timing from "too early" to "too late" combustion. Thus a fast combustion phasing control is required since it sets the performance limitation of the load control. Crank angle position for 50% heat release is used as combustion phasing feedback parameter. In this study, a dual-fuel approach is used to control combustion in a HCCI engine. This approach involves controlling the combustion heat release rate by adjusting fuel reactivity according to the conditions inside the cylinder. Two different octane fuels (methanol and n-heptane) are used for the study.

Homogeneous charged compression ignition (HCCI) engine is a low-temperature combustion (LTC) strategy with higher thermal efficiency and ultra-low NOx and particulate matter emission. Syngas is a renewable and clean alternative fuel that has gained researchers' interest, and it is one of the alternatives to fossil fuels. Syngas can be a suitable fuel for HCCI Engines due to their characteristics of high flame speed, lower flammability limits, and low auto-ignition temperatures. This paper presents the crank angle-based exergy analysis of syngas fuelled HCCI engines. Energy and exergy analysis is essential for the better performance and utilization of the HCCI engine. The syngas HCCI engine is numerically simulated in this study using a stochastic reactor model (SRM). In SRM models, physical parameters are described by a probability density function (PDF), and these parameters do not vary within the combustion chamber.

Diesel engines are lucrative in terms of high thermal efficiency and low specific fuel consumption. The major drawbacks of these engines are high NOx and particulate matter (PM) emissions due to heterogeneous combustion. In the current emissions norms (BS-VI), a limit for particle number concentration is also introduced. There are few numerical studies investigating the soot particle size and number characteristics at different engine operating conditions. In this work, a parametric numerical study is conducted to investigate the effect of engine operating parameters on PM characteristics such as number density, size, and volume fraction. Simulations were performed using the Reynolds Averaged Navier Stokes equation with renormalization group K-ε turbulence model available in ANSYS FORTE CFD software.

The potential for simultaneous reduction of soot and NOx emissions and higher fuel conversion efficiency has already been demonstrated for reactivity-controlled compression ignition (RCCI) engines. The RCCI engine has a relatively higher peak pressure rise rate (PPRR) and cyclic variations compared to the conventional diesel engine. The upper and lower operating load boundaries of the RCCI engine are restricted by higher PPRR and cyclic variations, respectively. The cyclic variations in the air-fuel ratio are one of the main factors which govern the variations in combustion parameters. The cyclic variations in combustion need to be controlled for stable engine operation. The present study estimates the cyclic air-fuel ratio from the measured in-cylinder pressure data for the RCCI engine. The RCCI experiments are performed on a modified single-cylinder compression ignition (CI) engine equipped with a development ECU.

This study examines the cycle-to-cycle variations (combustion instability) in the dual-fuel stationary compression ignition engine. The variations in the consecutive engine cycles are characterized under different load, gasoline/methanol-diesel premixing ratio (rp) and diesel injection timing (SOI). To investigate the combustion instability in dual-fuel CI-engine, gasoline and methanol are used as a low reactivity fuel (LRF) and is fed in the modified intake manifold during the suction stroke. The tests are performed for different fuel rp using developed port-fuel injector controller in the laboratory. The combustion instability is analyzed using the statistical method and Wavelet Transform (WT). Results indicate that combustion instability is more prone to lower and medium engine load, and variations are significantly higher for the high substitution fraction of LRF. The upper limit of fuel rp is restricted by higher variations in the combustion parameters.

The development of automotive engines continues to be determined by gradually more stringent emission norms including CO2 emissions and fuel consumption. To fulfill the simultaneous emission requirements for near-zero pollutants and low CO2 levels, several research studies are currently being carried out around the world on new engine combustion process, such as Homogeneous Charge Compression Ignition (HCCI). In HCCI engines, combustion rate, and ignition timing are dominated by physical and chemical properties of fuel/air/residual gas mixtures, boundary conditions including ambient temperature, pressure, and humidity, and engine operating conditions such as load, speed, etc. Higher cycle-to-cycle variations are observed in HCCI combustion engines due to the large variability of these factors. The cyclic variations in the HCCI engine are investigated on a modified four-stroke, four-cylinder engine. The HCCI combustion mode is tested with methanol fuel.

In the present study, experiments of reactivity control compression ignition (RCCI) combustion mode is performed on a single cylinder automotive diesel engine with development ECU (electronic control unit). For achieving RCCI combustion mode, low reactivity fuel (i.e., gasoline/methanol) is injected into the intake manifold, and high reactivity fuel (i.e., diesel) is directly injected into the engine cylinder. Mass of fuel injection per cycle and their injection events are controlled using ECU. This study presents the experimental investigation on the effect of high reactivity fuel injection timings on peak pressure rise rate (PPRR) and combustion stability in RCCI engine. The combustion parameters, i.e., PPRR, indicated mean effective pressure (IMEP) and total heat release (THR) are calculated from the in-cylinder pressure measurement data. In-cylinder pressure is measured using a piezoelectric pressure transducer installed on the engine cylinder head.

This study presents the experimental investigation of performance, combustion, gaseous and nano-particle emission characteristics of conventional compression ignition (CI) engine fueled with neat diesel and butanol/diesel blends. The experiments were conducted for neat diesel, 10%, 20% and 30% butanol/diesel blend on the volume basis at different engine loads. Combustion characteristics were investigated on the basis of in-cylinder pressure measurement and heat release analysis. The in-cylinder combustion pressure traces were recorded for 2000 consecutive engine combustion cycles for computation of heat release and different combustion parameters. Combustion stability analysis is conducted by analyzing the coefficient of variation of in indicated mean effective pressure (IMEP) and total heat release (THR). Wavelet analysis is also used for analyzing the temporal variations in IMEP data series.

Research in the utilization of hydrogen and syngas has significantly increased due to their clean-burning properties and the prospect of production from several renewable resources. Homogeneous charge compression ignition (HCCI) engine is low-temperature combustion (LTC) concept which combines the best features of conventional spark-ignition (SI) and compression-ignition (CI) engines. HCCI combustion engine has shown the potential for higher efficiency and ultralow NOx and soot emissions. In this study, syngas fueled HCCI combustion is simulated using stochastic reactor model (SRM) with a detailed chemical kinetic mechanism (32 species and 173 reactions). Detailed syngas oxidation mechanism included NOx reactions also. In SRM models physical parameters are described by a probability density function (PDF). These parameters does not vary within the combustion chamber, and thus the spatial distribution (due to local inhomogeneity’s) of the charge is represented in terms of a PDF.

Ethanol fuelled homogenous charge compression ignition engine (HCCI) offers a better alternative to tackle the problems of achieving higher engine efficiency and lower emissions. Numerical simulations were carried out for a HCCI engine fueled with ethanol by stochastic reactor model using newly developed reduced ethanol oxidation mechanism consists of 47 species and 272 reactions. Reduced mechanism used in this study is validated by measured engine cylinder pressure curves and measured ignition delays in constant volume reactors in the previous study. Simulations are conducted for engine speeds ranging from 1000 to 3000 rpm at different intake temperatures (range 365-465 K) by varying the air-fuel ratio. Parametric study for combustion and emission characteristics is conducted and engine maps are developed at most efficient inlet temperatures. The HCCI operating range is defined using combustion efficiency (>85%) and maximum pressure rise rate (<5 MPa/ms).

Cyclic variations are inherent in the combustion of internal combustion engines. However, extreme cyclic combustion variations limit the operation of spark-ignition (SI) engines, particularly at highly lean and diluted charge operation. Lean charge operation is desired due to its expected benefits in fuel efficiency and engine-out NOx and HC emissions. Studies suggested the existence of the low-dimensional deterministic nature of cyclic variations, which is essential from the perspective of designing a high-frequency controller. The lean limit of a SI engine operation may be extended by controlling the deterministic component of cyclic variations to meet the future strict emissions and fuel economy regulations. This paper presents a review of the evolution of the experimental and analytical understanding of cyclic combustion variations of spark-ignition engines.

This study experimentally investigates the combustion stability in RCCI engines along with the gaseous (regulated and unregulated) and particle emissions. Multifractal analysis is used to characterize the cyclic combustion variations in the combustion parameters (such as IMEP, CA50, and THR). This analysis aims to investigate the multifractal characteristics of the RCCI combustion mode near the misfiring limit. The investigation is carried out on a modified single-cylinder diesel engine to operate in RCCI combustion mode.The RCCI combustion mode is tested for different diesel injection timing (SOI) at fixed engine speed (1500rpm) and load (1.5 bar BMEP). The particle number characteristics and gaseous emissions are measured using a differential mobility spectrometer (DMS500) and Fourier Transform Infrared Spectroscopy (FTIR) along with Flame Ionizing Detector (FID), respectively.