Premixed Combustion Duration Research Articles

Investigation on fuel properties and engine performance of the extraction phase liquid of bio-oil/biodiesel blends

In this paper, biodiesel was used to upgrade bio-oil by extracting the high-quality fuel fractions in bio-oil through solvent extraction. After the extraction, the upper layer blends of biodiesel and the high-quality bio-oil components, also called the “extraction phase liquid”, was obtained and denoted as EPBB. Firstly, Thermogravimetric (TG) and Fourier transform infrared (FTIR) analyses indicated that the light components originally in bio-oil, such as alcohols, ethers, ketones and carboxylic acids were extracted from bio-oil to biodiesel and formed the EPBB. Then the fuel properties of EPBB were measured at different temperatures. The results showed that the density of EPBB was higher, while its viscosity, surface tension and lower heating value (LHV) were lower than those of biodiesel. Accordingly, EPBB revealed better atomization and evaporation characteristics as compared to biodiesel. Finally, the engine performance of EPBB was tested on an unmodified direct-injection diesel engine. When compared with biodiesel, the ignition delay of EPBB was longer, the premixed combustion duration was longer, while the total combustion duration was shorter. The fuel economy of EPBB was comparable to that of biodiesel, and the NOx, soot, CO and UHC emissions of EPBB were all lower than those of biodiesel.

Performance, regulated and unregulated exhaust emission of a stationary compression ignition engine fueled by water-ULSD emulsion

The interest in water-diesel emulsion fuel (EM) is increased recently because of the significant reduction in emissions from diesel exhaust, especially NOx and PM. In this study, a diesel engine configured for experimental investigations was fueled by ultra-low sulfur diesel (ULSD) and a diesel-water emulsion (EM). Both fuels’ combustion characteristics were studied at a speed of 1500 rpm and using a load of 2.5 and 5 bars and variable injection timings. Regular and irregular pollutants were studied at the same conditions as well as at variable engine loads and speeds to better understanding for their formation conditions. As for the first time (in the case of an engine running with a water-diesel emulsion) irregular pollutants for EM emulsion were measured.The measured results indicated that the use of water-diesel emulsion reduced the heat released in the combustion chamber, which causes an increase in the brake specific fuel consumption and ignition delay. For the tested loads, the diffusion combustion duration for EM was decreased when the injection timing was retarded while the opposite was occurred for premixed combustion duration. The regulated NOx and Smoke Number were reduced when EM was used compared to ULSD while CO and HC levels were increased at low engine’s speed and loads. Besides, these concentrations are depending on injection timing (they were higher at restarted timing). The unregulated emissions measured (Formaldehyde, Acetaldehyde, Methane, Acetylene, Ethylene, and propylene, Ammonia, and Acetone) were increased with using EM, especially at no and low loads, indicating the high impact of the combustion chamber temperature on these pollutants formation.

Effect of ethanol fraction on the combustion and emission characteristics of a dimethyl ether-ethanol dual-fuel reactivity controlled compression ignition engine

The purpose of this study was to investigate the effect of the ethanol fraction on the combustion and exhaust emissions characteristics of dimethyl ether (DME)-ethanol dual-fuel reactivity controlled compression ignition (RCCI) engine. In this study, a modified single-cylinder diesel engine was used. The main parameters of this study were the in-cylinder injection timing of DME and the ethanol fraction. The ethanol fraction was found to have a more obvious effect on the indicated mean effective pressure (IMEP) for advanced in-cylinder injection timings than around the top dead center (TDC) conditions. For the same ignition timing, the ethanol fraction had little influence on the IMEP. Increasing the ethanol fraction induced an increase in combustion duration and a decrease in premixed combustion duration (CA10–CA50) around the TDC injection condition. The effect of ethanol on Pmax was insignificant for CA50. The application of the DME-ethanol dual-fuel combustion strategy caused a significant reduction of ISNOx without deterioration of ISsoot. In addition, a high ethanol fraction led to a low ISNOx for the same premixed combustion duration. The ISHC and ISCO emissions increased slightly with increasing ethanol fraction for DME-ethanol dual-fuel combustion. However, the emissions from DME-ethanol combustion were lower than those obtained previously with biodiesel-ethanol and diesel-ethanol dual-fuel combustion.

An Experimental Investigation on the Combustion and Heat Release Characteristics of an Opposed-Piston Folded-Cranktrain Diesel Engine

In opposed-piston folded-cranktrain diesel engines, the relative movement rules of opposed-pistons, combustion chamber components and injector position are different from those of conventional diesel engines. The combustion and heat release characteristics of an opposed-piston folded-cranktrain diesel engine under different operating conditions were investigated. Four phases: ignition delay, premixed combustion, diffusion combustion and after combustion are used to describe the heat release process of the engine. Load changing has a small effect on premixed combustion duration while it influences diffusion combustion duration significantly. The heat release process has more significant isochoric and isobaric combustion which differs from the conventional diesel engine situation, except at high exhaust pressure and temperature, due to its two-stroke and uniflow scavenging characteristics. Meanwhile, a relatively high-quality exhaust heat energy is produced in opposed-piston folded-cranktrain diesel engines.

Impact of DME as an Oxygenated Alternative Fuel on Combustion and Emissions Reduction in a Transportation Vehicle at Low Load Condition

AbstractThis study investigates the impact of dimethyl ether (DME) on the combustion and exhaust emission characteristics at low engine load operating and pilot injection conditions in a four-cylinder diesel engine that was modified for DME application. The combustion characteristics were analyzed based on the combustion pressure, the rate of heat release, the accumulated heat release, and the premixed combustion characteristics. The emission characteristics were analyzed through the analysis of the nitrogen oxides (NOx), soot, hydrocarbon (HC), and carbon monoxide (CO). The heat release amount per unit crank angle in DME combustion is higher than that in diesel combustion in a pilot injected combustion mode. The accumulated heat release of DME during the main combustion is higher than that of diesel fuel. The pilot injection combustion of DME fuel started earlier than single-injection combustion does. The advanced pilot injection timing caused a decrease of premixed combustion duration and a retardation ...

HC and CO emissions reduction by early injection strategy in a bioethanol blended diesel-fueled engine with a narrow angle injection system

The main purpose of this study was to investigate how a narrow angle injector affects the combustion and exhaust emissions characteristics in a single-cylinder diesel engine fueled by diesel–bioethanol blends. This study focused on reducing HC and CO emissions in the exhaust emissions by the bioethanol blending of diesel. A narrow angle injector with an injection angle of 70° was used and compared with a conventional angle injector having a 156° injection angle. The bioethanol was blended with the conventional diesel up to 30% with 5% biodiesel. Experiments revealed that, in a narrow angle injector, the premixed combustion duration increased with bioethanol contents unlike the similar value of conventional injector. The premixed combustion phasing decreased with the increase of bioethanol in both injectors. The variation in the peak combustion pressure of the narrow angle injector was smaller than that of a conventional injector. In addition, the narrow angle injector induced a higher indicated mean effective pressure (IMEP) and a shorter ignition delay compared to the conventional injector. In terms of exhaust emissions characteristics, the low and stable ISHC and ISCO emissions can be achieved through the application of narrow angle injector to the diesel–bioethanol blends combustion. By the early injection combustion strategy, ISHC and ISCO emissions are significantly reduced.

Assessing combustion and emission performance of direct use of SVO in a diesel engine by oxygen enrichment of intake air method

This work investigated the effect of the oxygen enrichment in the intake air of diesel engines on the combustion and emissions performance using rape seed oil (RSO) as a fuel. The purpose of the paper is to investigate the potential of oxygen enrichment in the intake air method to restrain the deterioration of particulate emissions of the RSO due to its high viscosity so as to explore the possibility of direct use of SVO (straight vegetable oil) in diesel engines, which can reduce CO2 emissions and save cost. The combustion parameters such as ignition delay, heat release rate, in-cylinder peak temperature and pressure were determined. Engine out particulate and gaseous emissions of the RSO were measured at oxygen concentrations from 21% (by volume) (no enrichment) to 24% (by volume) and compared to diesel results. The enrichment of the intake air with oxygen decreased the ignition delay and premixed combustion duration, and increased the in-cylinder peak pressure and temperature. The particulate, CO and hydrocarbon emissions were significantly reduced while the NOx emissions increased as the oxygen enrichment rate increased. 22% oxygen enrichment rate was suggested to achieve lower than diesel particulate emissions with the lowest NOx penalty. Increased NOx could be controlled by other methods. The results show that the oxygen enrichment in intake air method enabled direct combustion of SVO in diesel engines with reduced particulate, hydrocarbon and CO emissions.

Comparison of combustion characteristics and brake thermal efficiency of a heavy-duty diesel engine fueled with diesel and biodiesel at high altitude

A comparative study of combustion characteristics and brake thermal efficiency of a diesel engine fueled with diesel and biodiesel (FAME100%) at high altitude (4500m) were conducted. A 6.7L heavy-duty turbocharged, common-rail diesel engine meeting EURO III standard was employed. In this present paper, tests were carried out on an on-board engine bench system in high altitude regions instead of simulating devices in laboratories. Two operating conditions were selected to reflect the engine performance in low-speed high-load and high-speed high-load conditions. Calibration of the engine was kept unchanged when the test engine was fueled with diesel and biodiesel respectively. Experiment results revealed that the peak heat release rate of biodiesel operations in premixed combustion duration was a little earlier but lower than that of diesel operations. The start of combustion and combustion duration for diesel and biodiesel operations were very similar. CA50 for biodiesel was 0.4°CA postponed in both operating conditions. By fuelling with biodiesel, there was a decrease of about 0.6% in BTE of the engine. Meanwhile, increases of approximately 2%, 17% and 11% in BSEC, BSFC and volumetric BSFC were observed. Comparison of exhaust mass flow inferred that biodiesel fuelling was helpful to reduce the fresh air consumption when the engine was operating at high altitude.

Impact of biodiesel in bioethanol blended diesel on the engine performance and emissions characteristics in compression ignition engine

In engine combustion studies of bioethanol blended diesel fuels, biodiesel is a very important blending fuel for preventing phase separation between diesel and bioethanol. The purpose of this study is to investigate the impact of biodiesel in bioethanol blended diesel fuel on ignition delay, premixed combustion phasing, engine performance and exhaust emissions characteristics. In this work, the fuel properties of diesel–bioethanol blends were measured and engine tests were conducted using a single cylinder diesel engine.Based on the experimental results, we found that increasing the biodiesel blending ratio recovered the reduced fuel density and cetane number of bioethanol blended diesel fuel, while the kinematic viscosity and surface tension both increased. In addition, the lower heating value (LHV) slightly decreased when biodiesel fuel was added. By increasing the blending ratio of biodiesel fuel, the ignition delay and the premixed combustion phasing advanced, and the IMEP decreased. However, the premixed combustion duration in all tested blended fuels showed almost similar values, regardless of the biodiesel contents. Biodiesel blending decreased the EI-HC emission in wide engine operating regions. In addition, for the premixed combustion phasing and ignition delay, the increase of biodiesel fuel influenced the decrease of EI-HC emission. In the case of EI-CO and EI-soot emissions at advanced injection timings (around 30° BTDC), when the combustion occurred in the squish area of the combustion chamber, the biodiesel blending impact was clear. The increase of biodiesel fuel reduced EI-CO and EI-soot emissions. In addition, the increase of biodiesel fuel slightly reduced the EI-NOx emission.

Reduction of the Pollutant Emissions from a Diesel Engine by the Application of Dimethyl Ether (DME) and the Control of the Intake Oxygen Flow Rate

The aim of this study was to investigate the effects of varying the global equivalence ratio and intake oxygen flow-rate on the combustion and exhaust emission characteristics of dimethyl ether (DME)-fueled combustion engine. This study dealt with the reduction characteristics of HC and CO emissions, as well as a simultaneous decrease of NOx and soot in a DME-fueled single-cylinder combustion engine. Our findings demonstrate that increasing the global equivalence ratio while holding the intake oxygen flow-rate constant caused the premixed combustion duration (CA10-CA50) to increase. Additionally, it was observed that decreasing the intake oxygen flow-rate while holding the injection quantity constant shortens the duration of CA10-CA50. In this investigation, simultaneous reduction of soot and indicated specific (IS)-NOx emissions from a diesel engine can be achieved by fueling with DME and setting a high EGR rate (low intake oxygen flow-rate). Further, applying high equivalence ratio together with a high EGR rate resulted in a near zero level of soot and IS-NOx emissions in DME combustion. In addition, DME combustion yielded lower IS-CO and IS-HC emissions than diesel combustion, even with a low intake oxygen flow-rate.

Particulate Emission Characteristics of a Compression Ignition Engine Fueled with Diesel–DMC Blends

The effect of fuel composition on the combustion characteristics and particulate emissions of a compression-ignition engine fueled with Euro V diesel fuel blended with dimethyl carbonate (DMC) was investigated experimentally. Blended fuels containing 4.48%, 9.07%, 13.78%, and 18.6% by volume of DMC, corresponding to 3%, 6%, 9%, and 12% by mass of oxygen in the blended fuels, were investigated. By analyzing the measured in-cylinder pressure data and the derived heat release rate, it is observed that the addition of DMC increases the ignition delay and the amount of heat release in the premixed combustion duration, but shortens both the diffusive burning duration and the total combustion duration. On the emission side, the smoke opacity, the particulate mass concentration as well as the total number of particulates are all reduced, while the proportion of soluble organic fraction (SOF) in the particulate is increased, by using the blended fuels. The geometric mean diameter of the particles shifts towards sm...

Effect of Multifunctional Fuel Additive Package on Fuel Injector Deposit, Combustion and Emissions using Pure Rape Seed Oil for a DI Diesel

This work investigates the effect of a multifunctional diesel fuel additive package used with RapeSeed Oil (RSO) as a fuel in a DI heavy duty diesel engine. The effects on fuel injectors’ cleanliness were assessed. The aim was to maintain combustion performance and preventing the deterioration of exhaust emissions associated with injector deposit build up. Two scenarios were investigated: the effect of deposit clean-up by a high dose of the additive package; and the effect of deposit prevention using a moderate dose of the additive package. Engine combustion performance and emissions were compared for each case against use of RSO without any additive. The engine used was a 6 cylinder, turbocharged, intercooled Perkins Phaser Engine, fitted with an oxidation catalyst and meeting the Euro II emissions limits. The tests were conducted under steady state conditions of 23kW and 47kW power output at an engine speed of 1500 rpm. The in-cylinder pressure, gaseous and particulate exhaust emissions were measured. The injectors were inspected using SEM (Scanning Electronic Microscopy). The results show that the use of the multifunctional fuel additive package reduces the ignition delay (ID), increases the premixed combustion duration (PCD) and improves the combustion stability. The multifunctional fuel additive package also reduced the deposit build up on the fuel injectors and prevented the deterioration of engine-out particulate, CO and hydrocarbon emissions

Effects of the addition of ethanol and cetane number improver on the combustion and emission characteristics of a compression ignition engine

Combustion and emission characteristics of a direct-injection diesel engine fuelled with diesel—ethanol blends were investigated. The results show that the ignition delay and the premixed combustion duration increase, while the diffusive combustion duration and the total combustion duration decrease with increase in the oxygen mass fraction in the blends. The addition of 0.2 per cent volume fraction of cetane number improver (isoamyl nitrite) could mean that the ignition delay and the premixed combustion duration of the fuel blends with 10vol% ethanol fraction recover to those of diesel fuel. Meanwhile, with the increase in the ethanol fraction in the fuel blends, the centre of the heat release curve moves closer to the top dead centre. The brake specific fuel consumption increases, while the diesel equivalent brake specific fuel consumption decreases with increase in the ethanol fraction. The exhaust smoke concentration increases and exhaust nitrogen oxide (NO x) concentration decreases on prolonging the fuel delivery advance angle for both diesel fuel and the blended fuels. For a specific fuel injection advance angle, the exhaust smoke concentration shows a large decrease and the exhaust NO x concentration a small decrease on ethanol addition.

Combustion characteristics of a compression ignition engine fuelled with diesel—ethanol blends

Combustion characteristics were analysed in a compression ignition engine fuelled with diesel—ethanol blends with and without a cetane number improver. The results show that, for the same brake mean effective pressure and engine speed, the maximum cylinder pressure Pmax, the ignition delay, the premixed combustion duration, and the fraction of heat release in premixed combustion phase will increase, while the diffusive combustion duration, the fraction of diffusive combustion phase, and the total combustion duration decrease with increase in the ethanol fraction in the blends. Meanwhile, the centre of the heat release curve moves close to the top dead centre, and the maximum rate (d Qb/d φ)max of heat release and the maximum rate (d p/d φ)max of pressure rise increase with increase in the ethanol fraction in the blends. The addition of a cetane number improver is beneficial to the decrease in the ignition delay, the cylinder peak pressure, the maximum rate of pressure rise, and the combustion noise when operating on diesel—ethanol blends.