Premixed Combustion Phase Research Articles

Effect of n-pentanol addition on the combustion, performance and emission characteristics of a direct-injection diesel engine

In this study, experiments were conducted to examine the effect of using a mixture of diesel and n-pentanol, which is one of the second-generation biofuels with comparable properties to diesel fuel, as fuel on the combustion, performance, and gaseous and particulate emissions of a naturally-aspirated, four-cylinder, direct-injection diesel engine. Three n-pentanol fractions in the fuel mixture were selected: 10, 20 and 30% by volume. Results show that, the addition of n-pentanol leads to longer ignition delay and increases the peak heat release rate in the premixed combustion phase. The brake specific fuel consumption increases with increase of n-pentanol, while the brake thermal efficiency is not affected. Regarding the gaseous emissions, n-pentanol addition results in the following consequence: (a) HC (hydrocarbon) and CO (carbon monoxide) emissions increase for 30% n-pentanol in the blended fuel at low engine load but decrease at high engine load; (b) a slight increase (maximum 8%) in NOx emissions but noticeable increase in NO2 emissions. Regarding the particulate emissions, n-pentanol is found to be very promising in terms of reducing both the mass concentration and the particulate number concentration simultaneously.

Modelling the effect of injection pressure on heat release parameters and nitrogen oxides in direct injection diesel engines

Investigation and modelling the effect of injection pressure on heat release parameters and engine-out nitrogen oxides are the main aim of this study. A zero-dimensional and multi-zone cylinder model was developed for estimation of the effect of injection pressure rise on performance parameters of diesel engine. Double-Wiebe rate of heat release global model was used to describe fuel combustion. extended Zeldovich mechanism and partial equilibrium approach were used for modelling the formation of nitrogen oxides. Single cylinder, high pressure direct injection, electronically controlled, research engine bench was used for model calibration. 1000 and 1200 bars of fuel injection pressure were investigated while injection advance, injected fuel quantity and engine speed kept constant. The ignition delay of injected fuel reduced 0.4 crank angle with 1200 bars of injection pressure and similar effect observed in premixed combustion phase duration which reduced 0.2 crank angle. Rate of heat release of premixed combustion phase increased 1.75 % with 1200 bar injection pressure. Multi-zone cylinder model showed good agreement with experimental in-cylinder pressure data. Also it was seen that the NOx formation model greatly predicted the engine-out NOx emissions for both of the operation modes.

Energy and Exergy analysis of a light duty diesel engine operating at different altitudes

Altitude above sea level produces a reduction in air density affecting the combustion process, pollutant emissions, and engine performance. In this work the combustion diagnosis of an automotive turbocharged diesel enginewas carried out from in-cylinder pressure signal. Tests were performed at three altitudes above sea level, under steady state operating conditions, using conventional diesel fuel. As altitude above sea level increased, the fuel/air mixture became richer. The brake specific fuel consumption, combustion duration, premixed combustion phase, maximum temperature, heat rejected to the gases and exergy destruction were also increased; at the same time, brake thermal efficiency, maximum in-cylinder pressure and in-cylinder exergy decreased. Mechanical efficiency and injection timing remained approximately invariable. Exergy destruction differences were caused by the combustion process, without significant effects during compression and expansion. The greater irreversibility resulting from altitude increase was linked with the lower energy quality of the exhaust gases.

Fuel combustion under asymmetric piston motion: Tested results

This paper presents the measured characteristics of a single piston hydraulic free-piston engine prototype. The detailed results about the piston motion and the fuel combustion are presented. The results show that there is a strong interaction between the piston motion and the fuel combustion in the free-piston engine. The gas force plays a leading role in the innate asymmetric piston motion around top dead centre. The small moving piston inertia makes the asymmetric characteristics more visible. The combustion energy conversion of the single piston hydraulic free-piston engine is fast. Most of the fuel injected burns in 1.0 ms in the pre-mixed combustion phase. Because of the asymmetric characteristics, the mixing-controlled combustion phase in the single piston hydraulic free-piston engine is much shorter than the one in the conventional diesel engine. The short combustion duration decreases the rated power of the free-piston engine. The asymmetric piston motion is unfavourable for the rated power increase of the free-piston engine. The smaller rated power has a negative effect on the free-piston engine application development.

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.

An experimental investigation on the performance, emission and combustion characteristics of preheated calophyllum inophyllum linn oil (honne oil) fed DI diesel engine

The present work examines the use of a non-edible vegetable oil namely honne oil, a new possible source of alternative fuel for diesel engine. The use of honne oil (unheated and preheated) in an agricultural direct injection (DI) diesel engine has not been reported in the literature. The high viscosity of honne oil can be reduced by preheating (preheated to 60ºC). The effect of temperature on the viscosity of honne oil has been investigated. Using preheated honne oil, brake thermal efficiency (BTE) and exhaust gas temperature (EGT) is increased compared to unheated honne oil. The emissions such as smoke opacity (SO), CO and HC of preheated honne oil were reduced and NOx emissions of preheated honne oil were increased compared to unheated honne oil. Premixed combustion phase of preheated honne oil is better than unheated honne oil and ND. Hence, preheated honne oil could be used in diesel engine for short-term application without any engine modification and adverse effect.

Aliphatic C–H and oxygenated surface functional groups of diesel in-cylinder soot: Characterizations and impact on soot oxidation behavior

This paper reports the characteristics of surface functional groups (SFGs) and oxidation reactivity of in-cylinder soot during the diesel combustion process and discusses the correlation between SFGs and the oxidation reactivity of soot. Test soot samples were obtained from a total cylinder sampling system. SFGs and the apparent activation energy for the soot oxidation were determined by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. Results reveal that the concentrations of aliphatic C–H, C–OH and CO groups are dependent on the combustion stages. The ratio of aromatic CC to aliphatic C–H groups rapidly increases in the premixed combustion phase, indicating significant loss of aliphatic C–H groups from the soot surface. As the combustion proceeds, the ratio of the two groups gradually increases, following an earlier drop during the diffusion combustion phase. In contrast, the concentration of both C–OH and CO groups shows a bimodal distribution during the combustion process, with the concentrations peaking in the premixed and diffusion combustion stages, respectively. The apparent activation energies for the oxidation of soot collected under the applied engine operating conditions are observed in the range of 122.12–158.2kJmol−1 at various crank angles, revealing a similar variation to that of aliphatic C–H groups. Aliphatic C–H groups are a more important factor in governing soot oxidation reactivity than the oxygenated SFGs.

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.

Selected combustion parameters of biogas at elevated pressure–temperature conditions

Results from tests conducted in several RTD centers lead to conclusion that biogas as a potential fuel for the internal combustion (IC) spark ignited (SI) engine features with its satisfactory combustion predisposition causing smooth engine run without accidental misfiring or knock events. This good predisposition is obtained due to carbon dioxide (CO2) content in the biogas. On the other hand, carbon dioxide as incombustible gas contribute to decrease in the brake power of the biogas fueled engine. To analyze mutual CO2 and CH4 content on biogas burning the combustion parameters as follows: adiabatic combustion temperature, laminar flame speed and ignition delay of biogas with various methane content were determined and presented in the paper. Additionally, these parameters for pure methane were also included in order to make comparison between each other. As computed, ignition delay, which has is strongly correlated with knock resistance, can change several times with temperature increase, but does not change remarkably with increase in methane content. Adiabatic combustion temperature does not also ought to influence on engine performance or increase in engine cooling and exhaust losses due to its insignificant changes. The largest change was observed in laminar flame speed, that can influence on development of the first premixed combustion phase.

Second-law analysis of fuel–air mixing and combustion subprocesses in a heterogeneous charge engine

Fuel–air mixing and combustion in engines are complex phenomena involving several subprocesses, wherein the availability (exergy) of the working fluid could be destroyed owing to irreversibilities or could be lost during energy exchanges. In the present work, a quasi-dimensional multi-zone engine model is used to quantify the availability destructions and losses associated with various mixing and combustion subprocesses in a heterogeneous charge compression ignition engine. This second-law analysis helps us to estimate the contributions of individual subprocesses towards the overall availability deficit. The results indicate that most of the availability destruction prior to ignition occurs because of fuel vaporization and mixing, whereas chemical reaction accounts for up to half of the total availability deficit during combustion. In-cylinder pressure equilibration and mixing of the combustion products with spray gases have major roles in availability destruction during the premixed combustion phase and the mixing-controlled combustion phase respectively. The contributions of wall heat transfer, heat transfer from the spray to the surrounding air and mixing of entrained air with spray gases assume significance in the later stages of combustion. Parametric studies indicate that reducing the in-cylinder air swirl and retarding the injection timing effectively curtail the availability deficit, thus improving the exergetic efficiency.

Premixed-Diffusive Multizone Model for Combustion Diagnostics in Conventional and PCCI Diesel Engines

A new multizone premixed-diffusive combustion model has been developed, assessed, and applied to diagnose the burning process and emission formation in a conventional and in a premixed charge compression ignition (PCCI) diesel engine. The model is based on the Dec conceptual scheme, which considers combustion as a two-stage quasi-steady process: All fuel particles undergo a first rich premixed combustion phase, and the products complete their oxidation in close-to-stoichiometric conditions at the jet periphery through a diffusion flame. The combustion chamber contents have been divided into several homogeneous zones to which the energy and mass conservation principles were applied. The computed thermodynamic and thermochemical properties in the burned gas zones allowed a post-processing analysis to be made of the nitric oxides (NO), particulate matter (PM), and carbon monoxide (CO) formation. The model requires the in-cylinder pressure trace and other experimental engine quantities as input data and calculates the premixed and diffusive heat release rates along with the temperature and mass evolutions of the different zones. Thus, the model is not predictive but diagnostic: The objective is to interpret measured engine data in order to obtain insight into the in-chamber combustion and pollutant formation processes. The model has been tested on EGR-sweeps and under full-load conditions on the conventional engine and under a high EGR operating condition on the PCCI engine. With reference to NO emissions, the model results showed an excellent agreement with the experimental data for all the tests even when the main model parameters were kept constant for different test conditions. Good results were also obtained for the prediction of the CO and PM emission levels. Finally, for the premixed combustion zone, it was ascertained that higher local A/F ratios were required in the PCCI combustion mode than in the conventional mode as a consequence of the increase in the degree of premixing.

Effect of dimethoxy-methane and exhaust gas recirculation on combustion and emission characteristics of a direct injection diesel engine

The effect of fuel constituents and exhaust gas recirculation (EGR) on combustion characteristics, fuel efficiency and emissions of a direct injection diesel engine fueled with diesel-dimethoxymethane (DMM) blends was investigated experimentally. Three diesel-DMM blended fuels containing 20%, 30% and 50% by volume fraction of DMM, corresponding to 8.5%, 12.7% and 21.1% by mass of oxygen in the blends, were used. By the use of DMM, it is observed that CO and smoke emissions as well as the total number and mass concentration of particulate reduce significantly, while HC emissions and particulate number with lower geometric mean diameters ( D i < 0.039 μm) increase slightly. For each fuel, there is an increase of ignition delay whereas a decrease of cylinder pressure and heat release rate in the premixed combustion phase when the diesel engine was operated with EGR system. The brake thermal efficiency fluctuates at small EGR ratio, while decreases with the further increase of EGR ratio. With an increase of EGR ratio, NO x emission is reduced at the cost of increased smoke, HC and CO emissions as well as the total number and mass of particulates for each fuel.

Experimental investigation on a diesel engine using neem oil and its methyl ester

Fuel crisis and environmental concerns have led to look for alternative fuels of bio-origin sources such as vegetable oils, which can be produced from forests, vegetable oil crops and oil bearing biomass materials. Vegetable oils have energy content comparable to diesel fuel. The effect of neem oil (NeO) and its methyl ester (NOME) on a direct injected four stroke, single cylinder diesel engine combustion, performance and emission is investigated in this paper. The results show that at full load, peak cylinder pressure is higher for NOME; peak heat release rate during the premixed combustion phase is lower for neat NeO and NOME. Ignition delay is lower for neat NeO and NOME when compared with diesel at full load. The brake thermal efficiency is slightly lower for NeO at all engine loads, but in the case of NOME slightly higher at full load. It has been observed that there is a reduction in NOx emission for neem oil and its methyl ester along with an increase in CO, HC and smoke emissions.

Experimental study on the performance, emission and combustion characteristics of rubber seed oil-diesel blends in a DI diesel engine

In the present work, experiments have been carried out to assess the suitability of rubber seed oil and its blends with diesel in a diesel engine. Tests were conducted with different blends of R80-D20 (80% of rubber seed oil and 20% of diesel by volume) and R70-D30 (70% of rubber seed oil and 30% of diesel by volume). Experimental results indicate that the brake thermal efficiency increases from 26.5% to 27.7% with the optimum blend of R70-D30. There is a reduction in emissions is also observed except NOx level at all loads. Smoke emission reduces drastically from 6.1 to 4.7 BSU. Combustion parameters indicated a decrease in ignition delay and combustion duration compared with neat RSO. This will also contribute to higher heat release rate in the premixed combustion phase. Current investigations reveal that the performance of R70-D30 blend is closer to diesel.

Performance, emission and combustion characteristics of DI diesel engine running on blends of calophyllum inophyllum linn oil (honne oil)/diesel fuel/kerosene

Kerosene (K)/diesel fuel (D)/honne oil (H) blends have a potential to improve the performance and emissions and to be alternatives to neat diesel fuel (ND) and has not been reported in the literature. Experiments have been conducted on DI diesel engine when fuelled with ND, H10 (10%H + 90%D, by volume) to H30, HK10 (10%H + 45%K + 45%D), HK20 (20%H + 40%K + 40%D) and HK30 (30%H + 35%K + 35%D). The emissions [CO, HC and smoke density (SD)] of fuel blend HK20 are found to be lowest, with CO and HC dropping significantly. The NO x level is higher with HK10 to HK30 compared to ND and H10 to H30. The brake thermal efficiency of HK10 to HK30 is almost the same and it is higher as compared to ND and H10 to H30. There is a good trade off between NO x and SD. Peak cylinder pressure and premixed combustion phase increases as kerosene content increases.

Investigation on the gaseous and particulate emissions of a compression ignition engine fueled with diesel–dimethyl carbonate blends

The effect of dimethyl carbonate (DMC) on the gaseous and particulate emissions of a diesel engine was investigated using Euro V diesel fuel blended with different proportions of DMC. Combustion analysis shows that, with the blended fuel, the ignition delay and the heat release rate in the premixed combustion phase increase, while the total combustion duration and the fuel consumed in the diffusion combustion phase decrease. Compared with diesel fuel, with an increase of DMC in the blended fuel, the brake thermal efficiency is slightly improved but the brake specific fuel consumption increases. On the emission side, CO increases significantly at low engine load but decreases at high engine load while HC decreases slightly. NO x reduces slightly but the reduction is not statistically significant, while NO 2 increases slightly. Particulate mass and number concentrations decrease upon using the blended fuel while the geometric mean diameter of the particles shifts towards smaller size. Overall speaking, diesel–DMC blends lead to significant improvement in particulate emissions while the impact on CO, HC and NO x emissions is small.

Experimental Investigations to Improve the Performance of Rubber Seed Oil–Fueled Diesel Engine by Dual Fueling with Hydrogen

In this experimental work, base data were generated with diesel and neat high free fatty acid (FFA) rubber seed oil (RSO) using a single-cylinder air-cooled diesel engine with a rated output of 4.4 kW at 1500 rpm. Neat RSO results in reduced thermal efficiency of 26.6% compared with diesel efficiency of 29.9% and high smoke emissions compared to diesel. This is mainly due to low volatility, higher viscosity, and density of RSO. In order to improve the performance of the RSO-fueled diesel engine, experiments were conducted with hydrogen as the inducted fuel and RSO as the main fuel in dual-fuel operation. Experimental results indicate that the brake thermal efficiency increases from 75% load to full load in the dual-fuel operation. At full load, the maximum brake thermal efficiency is 28.1% with RSO-hydrogen dual-fuel mode at hydrogen energy share of 8.39%. The smoke level is reduced at all loads with RSO-hydrogen dual-fuel mode. The smoke level is reduced from 6.1 to 3.8 BSU in dual-fuel operation at the maximum efficiency point at full load. Hydrogen induction reduces HC and CO at all loads, but NOx increases at 75% and full load, but there is no appreciable change at lower loads. The combustion duration decreases with hydrogen addition. This will also contribute to higher heat release rate in the premixed combustion phase. The cylinder peak pressure and maximum rate of pressure rise increases mainly at higher outputs. On the whole it is concluded that hydrogen can be inducted along with air in order to reduce smoke levels and improve thermal efficiency of rubber seed oil–fueled diesel engines for loads above part load.

Combustion and performance evaluation of a diesel engine fueled with biodiesel produced from soybean crude oil

In this study, the biodiesel produced from soybean crude oil was prepared by a method of alkaline-catalyzed transesterification. The important properties of biodiesel were compared with those of diesel. Diesel and biodiesel were used as fuels in the compression ignition engine, and its performance, emissions and combustion characteristics of the engine were analyzed. The results showed that biodiesel exhibited the similar combustion stages to that of diesel, however, biodiesel showed an earlier start of combustion. At lower engine loads, the peak cylinder pressure, the peak rate of pressure rise and the peak of heat release rate during premixed combustion phase were higher for biodiesel than for diesel. At higher engine loads, the peak cylinder pressure of biodiesel was almost similar to that of diesel, but the peak rate of pressure rise and the peak of heat release rate were lower for biodiesel. The power output of biodiesel was almost identical with that of diesel. The brake specific fuel consumption was higher for biodiesel due to its lower heating value. Biodiesel provided significant reduction in CO, HC, NO x and smoke under speed characteristic at full engine load. Based on this study, biodiesel can be used as a substitute for diesel in diesel engine.

Experimental study of the effects of vegetable oil methyl ester on DI diesel engine performance characteristics and pollutant emissions

Vegetable oil methyl ester (VOME) is produced through the transesterification of vegetable oil and can be used as biodiesel in diesel engines as a renewable, nontoxic, and potentially environmentally friendly fossil fuel alternative in light of growing concerns regarding global warming and increasing oil prices. This study used VOME fuels produced from eight commonly seen oil bases to conduct a series of engine tests to investigate the effects of VOME on the engine performance, exhaust emissions, and combustion characteristics. The experimental results showed that using VOME in an unmodified direct injection (DI) diesel engine yielded a higher brake specific fuel consumption (BSFC) due to the VOME fuel’s lower calorific value. The high cetane number of VOME also imparted a better ignition quality and the high intrinsic oxygen content advanced the combustion process. The earlier start of combustion and the rapid combustion rate led to a drastic increase in the heat release rate (HRR) and the in-cylinder combustion pressure (ICCP) during the premixed combustion phase. A higher combustion rate resulted in higher peaks of HRR and ICCP as well as near the top dead center (TDC) position. Thus, it was found that a diesel engine fueled with VOME could potentially produce the same engine power as one fueled with petroleum diesel (PD), but with a reduction in the exhaust gas temperature (EGT), smoke and total hydrocarbon (THC) emissions, albeit with a slight increase in nitrogen oxides (NO x ) emissions. In addition, the VOME which possesses shorter carbon chains, more saturated bonds, and a higher oxygen content also yields a lower EGT as well as reduced smoke, NO x , and THC emissions. However, this is obtained at the detriment of an increased BSFC.

Combustion analysis of a direct injection diesel engine when fuelled with sunflower methyl ester and its diesel blends

Uncertainty in the availability of petroleum-based fuels in the near future and stringent pollution norms have triggered a search for renewable and clean-burning fuels. The use of vegetable oil as an alternative fuel has for long been in the pipeline, but its direct use has been limited because of its higher viscosity. In this work, sunflower oil was taken as feedstock and the feasibility of sunflower oil methyl ester (SFME) as an alternative fuel for diesel engines was investigated. Tests were conducted in a 4.4 kW, single cylinder; naturally aspirated direct injection diesel engine. It was observed that the premixed combustion phase of SFME and its blends were less intense compared with diesel oil. In addition, it was observed that SFME and its blends had slightly lower thermal efficiency and lower tailpipe emissions than diesel oil.