High-speed Direct Injection Diesel Engine Research Articles

Comparison between PEE10 and PEE10-Bioethanol Blends on Performance and Emission Characteristics of a HSDI Diesel Engine

Biofuels are an alternative fuel currently being developed to reduce the diesel-engine environmental impact. The release of carbon dioxide (CO2), nitric oxide (NO) and black smoke (BS) becomes an issue derived from diesel engines even in lean-mixture combustion causing an adverse effect to human health. The main aim of the research study is to present the use of biofuels, a mixture of diesel and 10 % palm oil ethyl ester (PEE10) and PEE10 blended with bioethanol from 5 to 20 %, compared with conventional diesel fuel. The biofuels were run on a high-speed direct injection diesel engine at a constant speed of 3,000 rpm under various loads. The use of PEE10 resulted in brake thermal efficiency (BTE) reduction by 2 % and brake specific fuel consumption (BSFC) incrementation by 8 %, but the exhaust emissions were lower than diesel, except for CO2 and NO. However, PEE10 engine performance was better and exhaust gas emissions were lower for both pollutants than diesel mixed with 10 % bioethanol. The investigation of PEE10 with increasing bioethanol revealed that the use of PEE10 blended with 5 % bioethanol (PEE10E5) can improve engine performance, while the BTE and BSFC were close to that of diesel, and exhaust emissions, especially CO2, NO and BS reduced. Moreover, BTE from PEE10E5 fueling increased by 2 % but BSFC was subtle increased, compared to PEE10. On the other hand, the increasing bioethanol from 10 to 20 % in PEE10 led to the more reduction in engine performance, but the engine pollutants were also continuously decreased. Specifically, the blend of PEE10 and 20 % bioethanol indicates that CO2, NO and BS were reduced by 10, 15 and 33 %, respectively, compared to diesel fuel.
 HIGHLIGHTS
 
 A mixture of diesel and 10 % palm oil ethyl ester (PEE10) has less exhaust emissions than diesel blended with 10 % palm oil methyl ester (PME10)
 PEE10 blended with 5 % bioethanol can improve engine performance, while the brake thermal efficiency and brake specific fuel consumption are close to that of diesel and PME10
 The increasing bioethanol from 10 to 20 % in PEE10 leads to the more reduction in engine performance, but the engine pollutants, especially carbon dioxide, nitric oxide and black smoke, are also continuously decreased
 
 GRAPHICAL ABSTRACT

Artificial neural network (ANN) assisted prediction of transient NOx emissions from a high-speed direct injection (HSDI) diesel engine

The understanding and prediction of NOx emissions formation mechanisms during engine transients are critical to the monitoring of real driving emissions. While many studies focus on the engine out NOx formation and treatment, few studies consider cyclic transient NOx emissions due to the low time resolution of conventional emission analysers. Increased computational power and substantial quantities of accessible engine testing data have made ANN a suitable tool for the prediction of transient NOx emissions. In this study, the transient predictive ability of artificial neural networks where a large number of engine testing data are available has been studied extensively. Significantly, the proposed transient model is trained from steady-state engine testing data. The trained data with 14 input features are provided with transient signals which are available from most engine testing facilities. With the help of a state-of-art high-speed NOx analyser, the predicted transient NOx emissions are compared with crank-angle resolved NOx measurements taken from a high-speed light duty diesel engine at test conditions both with and without EGR. The results show that the ANN model is capable of predicting transient NOx emissions without training from crank-angle resolved data. Significant differences are captured between the predicted transient and the slow-response NOx emissions (which are consistent with the cycle-resolved transient emissions measurements). A particular strength is found for increasing load steps where the instantaneous NOx emissions predicted by the ANN model are well matched to the fast-NOx analyser measurements. The results of this work indicate that ANN modelling could strongly contribute to the understanding of real driving emissions.

On the application of artificial neural networks for the prediction of NOx emissions from a high-speed direct injection diesel engine

This article considers the application and refinement of artificial neural network methods for the prediction of NO x emissions from a high-speed direct injection diesel engine over a wide range of engine operating conditions. The relative computational cost and performance of two backpropagation algorithms, Levenberg–Marquardt and Bayesian regularization, for this application are compared, with the Levenberg–Marquardt algorithm demonstrating a significant cost advantage. This work also assesses the performance of two alternative filtering approaches, a p-value test and the Pearson correlation coefficient, for reducing the required number of input variables to the model. The p-value test identified 32 input parameters of significance, whereas the Pearson correlation test highlighted 14 significant parameters while additionally providing a ranking of their relative importance. Finally, the article compares the predictive performance of the models generated by the two filtering methods. Overall, both models show good agreement to the experimental data with the model created using the Pearson correlation test showing improved performance in the low-NO x region.

An Insight into Diesel–Ethanol and Diesel–Biodiesel Blends Spraying and Co-combustion in HSDI Diesel Engine

Biodiesel and ethanol are known as the typical alternative and renewable fuels that can replace fossil and mineral fuels; however, they can affect combustion due to their undesirable innate traits. The investigation is a numerical attempt to compare the synthesized blended fuels of diesel–ethanol (DE) and diesel–biodiesel (DB) and pure diesel (D100) when combusted in a high-speed direct injection (HSDI) diesel engine. The blends are B10D90, B50D50, E05D95, E10D90, and E85D15. In the initial condition of the code, the fuel is defined as multi-component and the share of each component is determined. The results are indicative of lower ethanol-blended fuel’s mean spray droplet (SMD), thus lower CO2 and soot emissions although it is afflicted with low engine output in terms of power and efficiency. The interaction of SMDE85D15 = 2.5 µm and LHVE85D15 = 31,045.3 kJ/kg with the SMDB50D50 = 2.664 µm and LHVB50D50 = 40335 kJ/kg, droplet diameter is more efficient in emission reduction in better spraying, and on the other hand fuel’s intrinsic heat value is more significant for power generation.

Evaluation of exhaust gas recirculation techniques on a high-speed direct injection diesel engine using first law analysis

The effects of different exhaust gas recirculation (EGR) strategies on engine efficiency and the resulting energy flows at two speed/load conditions (1500 r/min/6.8 bar net indicated mean effective pressure (nIMEP) and 1750 r/min/13.5 bar nIMEP) were studied using a first law analysis approach. The EGR strategies tested were as follows: cooled high-pressure exhaust gas recirculation (baseline), the application of exhaust gas recirculation with the swirl flap closed and the use of exhaust gas recirculation under constant λ conditions. The closed swirl flap exhaust gas recirculation strategy reduced brake efficiency under high load conditions and increased heat transfer to the coolant for both load cases. Soot and CO emissions increased at high load, however, with an increase in NOx relative to the baseline case. The constant λ exhaust gas recirculation strategy reduced brake efficiency under low load, as well as the heat flow to the coolant for both load cases. The constant λ exhaust gas recirculation strategy benefited smoke emissions and increased combustion exhaust gas recirculation tolerance, albeit with a penalty in NOx emission.

Separate and combined effects of hydrogen and nitrogen additions on diesel engine combustion

Shortage of non-renewable energies, increase in fossil fuel prices and stricter emissions regulations due to high NOx and soot emissions emitted from combustion of heavy diesel fuels by compression ignition engines, has led consumers to use renewable, cleaner and cheap fuels. An investigation has been computationally carried out to explore the influences of hydrogen and nitrogen addition on engine performance such as indicated power and indicated specific energy consumption and amounts of pollutant emissions like NOx, soot, and CO in an HSDI (High-Speed Direct Injection) diesel engine. Optimized sub-models, such as turbulence model, spray model, combustion model and emissions models have selected for the main CFD code. Meanwhile, HF (Homogeneity Factor) has been employed for analysing in-cylinder air-fuel mixing quality under various addition conditions. After validations with experimental data of diesel combustion with a single addition of 4% hydrogen and combined addition of 6% hydrogen + 6% nitrogen, investigations have conducted for modeling mixing and combustion processes with additions of hydrogen and nitrogen by ranges of 2–8% (v/v). Results showed that a single addition of H2 increased NOx and decreased CO and soot and improved ISEC and IP. In the case of nitrogen addition, NOx decreased, both CO and soot emission increased and ISEC and IP considerably ruined compared with NDC operation. Based on the results obtained for simultaneous addition of N2 (8% of v/v) and H2 (8% of v/v), NOx and soot emissions decreased by 11.5% and 42.5% respectively, and ISEC and IP improved 25.7% and 13%, respectively. But amount of CO emissions had an increase of 52% should be paid necessary attention as a main disadvantage.

The influence of pilot injection on high-temperature ignition processes and early flame structure in a high-speed direct injection diesel engine

Simultaneous high-speed natural luminosity and OH* chemiluminescence imaging is used to characterize high-temperature ignition processes in conventional diesel combustion with a pilot-main injection strategy in a single-cylinder, light-duty optical diesel engine. High-speed imaging provides temporally and spatially resolved information in terms of high-temperature ignition processes and flame structure during the combustion. Using these imaging measurements, the high-temperature inflammation and the diffusion flame development processes are analyzed. The chemiluminescence signal shows a hot, reactive mixture, which gradually decreases after the peak release of the pilot combustion and lasts long after the apparent heat release has ended. Therefore, when the reactive pilot mixture exists near the main injection jets, the high-temperature ignition of the main injection is apparently initiated through interactions with the reactive pilot mixture. High-temperature autoignition, another process by which ignition of the main injection occurs, is observed in main injection plumes where the chemiluminescence signal of the reactive pilot mixture becomes very weak or is absent at the start of main injection. As the reaction of the main injection continues, the non-premixed main injection jet structure is developed and the high-temperature reacting region expands throughout the jet.

Characteristics of pressure wave in common rail fuel injection system of high-speed direct injection diesel engines

The latest generation of high-pressure common rail equipment now provides diesel engines possibility to apply as many as eight separate injection pulses within the engine cycle for reducing emissions and for smoothing combustion. With these complicated injection arrangements, optimizations of operating parameters for various driving conditions are considerably difficult, particularly when integrating fuel injection parameters with other operating parameters such as exhaust gas recirculation rate and boost pressure together for evaluating calibration results. Understanding the detailed effects of fuel injection parameters upon combustion characteristics and emission formation is therefore particularly critical. In this article, the results and discussion of experimental investigations on a high-speed direct injection light-duty diesel engine test bed are presented for evaluating and analyzing the effects of main adjustable parameters of the fuel injection system on all regulated emission gases and torque performance. Main injection timing, rail pressure, pilot amount, and particularly pilot timing have been examined. The results show that optimization of each of those adjustable parameters is beneficial for emission reduction and torque improvement under different operating conditions. By exploring the variation in the interval between the pilot injection and the main injection, it is found that the pressure wave in the common rail has a significant influence on the subsequent injection. This suggests that special attentions must be paid for adjusting pilot timing or any injection interval when multi-injection is used. With analyzing the fuel amount oscillation of the subsequent injections to pilot separation, it demonstrates that the frequency of regular oscillations of the actual fuel amount or the injection pulse width with the variation in pilot separation is always the same for a specified fuel injection system, regardless of engine speed, fuel amount, injection pulse, and injection pressure.

Analysis the ECFM-3Z Combustion Model for Simulating the Combustion Process and Emission Characteristics in a HSDI Diesel Engine

An advanced CFD simulation has been performed to analyze the ECFM-3Z (Extended Coherent Flame Model-3Z) combustion model for simulating the combustion process and emission characteristics in a high speed direct injection (HSDI) diesel engine. A four cylinders, HSDI diesel engine based on a Ford production engine with a 2nd generation Delphi common rail fuel injection system has been modeled in this research. 3D CFD simulation was carried out from intake valve closing (IVC) to exhaust valve opening (EVO). A good agreement of calculated and measured in-cylinder pressure trace as well as pollutant formation trends could be observed for all investigated operating points. Based on the confidence gained from validation, the study is extended to evaluate the effect of fuel injection timing on engine performance and emissions. For this purpose, a comprehensive study of the effect of injection timing with respect to performance and emissions has been considered. Three main injection timing, (1) 2.65 BTDC, (2) 0.65 BTDC and (3) 1.35 ATDC, all with 30 crank angle pilot separations has been used to investigate the effect of the injection timing. The results show that the current methodology can be applied as a beneficial tool for analyzing the parameters of the diesel combustion under HSDI operating condition.

Optical investigation of fuel and in-cylinder air-swirl effects in a high-speed direct-injection engine

The primary aim of this study is to investigate current issues of combustion in high-speed direct-injection diesel engines in detail by optical diagnostics. Both fuel and engine design are considered. Recently, measurements of engine-out emissions demonstrated that approximately soot-free combustion can be achieved using a newly designed two-component fuel named BLT. It was composed of 70% butyl levulinate and 30% n-tetradecane (by volume). In this work, the underlying mechanism is clarified by in-cylinder visualization of OH* radicals and soot. In particular, it turns out that in-cylinder soot formation is avoided almost completely, that is, the soot oxidation process is much less important. This is basically achieved by both the oxygen content (about 21%) and the low cetane number (approximately 33) of BLT. The latter leads to enhanced pre-mixing of fuel and air. Consequently, soot formation can be greatly reduced because it depends on the air–fuel ratio of the mixture shortly before high-temperature combustion. The influence of in-cylinder air swirl on combustion and soot formation is also studied for both BLT and conventional diesel fuel, respectively, using the same optical diagnostic. The measurements show that the combustion zone strongly depends on the local gas-flow velocity for diesel fuel. Soot formation decreases with increasing swirl because of enhanced air entrainment and pre-mixing of fuel and air. In addition, the results indicate that soot oxidation is improved under high-swirl conditions for diesel fuel. In contrast, the influence of swirl on the combustion of BLT is overall found to be weak, suggesting that swirl could be reduced in future high-speed direct-injection engines for BLT-like fuels.

Comparison of Combustion, Performance, and Emissions of HSDI Diesel Engine Operating on Blends of Diesel Fuel with Ethanol, n-Butanol, or Butanol Isomer Ether DEE

AbstractThe present investigation evaluates the combustion, performance, and exhaust emissions of diesel fuel in blends with either 5, 10, and 15% ethanol, or with 8, 16, and 24% n-butanol, or lastly with 8, 16, and 24% diethyl ether (DEE, an isomer ether of butanol) by volume, fueling a standard, experimental, single-cylinder, four-stroke, high-speed direct injection (HSDI), Hydra diesel engine. The tests were conducted using each of the above fuel blends, with the engine operating at three different loads. Fuel consumption, exhaust gas temperature, and exhaust smoke, nitrogen oxides (NOx), carbon monoxide (CO), and total unburned hydrocarbons (HC) were measured. The differences in combustion, performance, and exhaust emissions of those biofuel blends from the baseline operation of the diesel engine (when working with neat diesel fuel) and among themselves are compared. Fuel injection diagrams, combustion chamber pressure diagrams, and heat release rate (HRR) diagrams obtained thereof, reveal some intere...

An experimental study into the effect of the pilot injection timing on the performance and emissions of a high-speed common-rail dual-fuel engine

Dual-fuel technology has the potential to offer significant improvements in the emissions of carbon dioxide from light-duty compression ignition engines. In these smaller-capacity high-speed engines, where the combustion event can be temporally shorter, the injection timing can have an important effect on the performance and emissions characteristics of the engine. This paper discusses the use of a 0.51 l single-cylinder high-speed direct-injection diesel engine modified to achieve port directed gas injection. The effect of the pilot diesel injection timing on the dual-fuel engine performance and emissions was investigated at engine speeds of 1500 r/min and 2500 r/min and loads equivalent to gross indicated mean effective pressures of 0.15 MPa, 0.3 MPa, 0.45 MPa and 0.6 MPa, for a fixed gas substitution ratio (on an energy basis) of 50%. Furthermore, the effect of the pilot injection quantity was investigated at a constant engine speed of 1500 r/min by completing a gaseous substitution sweep at the optimised injection timing for each load condition. The results identify the limits of single-injection timing during dual-fuel combustion and the gains in the engine performance and stability that can be achieved through optimisation of the pilot injection timing. Furthermore, the pilot injection timing and quantity were shown to have fundamental effects on the formation and emissions of carbon monoxide, nitrogen oxide and total hydrocarbon. The potential for dual-fuel combustion to achieve significant reductions in the specific carbon dioxide was also highlighted, with reductions of up to 30% being achieved at full load compared with the baseline diesel case.

Engine testing of novel diesel fuel detergent–dispersant additives

HPCR (High Pressure Common Rail) design features of modern fuel injection systems and engine working conditions force the use of fuels with good thermooxidative properties, very low solids and metallic elements content, satisfactory resistance to microbial contamination and, above all, very effective detergent performance to prevent deposit formation and its accumulation in modern HSDI (High Speed Direct Injection) diesel engines. The paper presents the state of testing of novel detergent additives for diesel fuels, succinicimide-amide type, synthesized at INiG compared to commercial additives and base diesel fuel results. The dynamometer engine tests were performed on the Peugeot XUD 9A/L and on HSDI (Ford Duratorq 2.0i 16V TdCi and Fiat 2.0 JTD) tests engines, equipped with indirect injection (the first one), and with HPCR fuel injection systems (the last two).

Combustion and soot processes of diesel and rapeseed methyl ester in an optical diesel engine

In-cylinder combustion and soot processes for ultra-low sulphur diesel (ULSD) and rapeseed methyl ester (RME) fuels were investigated in an optically accessible high speed direct injection diesel engine (HSDI) using in situ optical and laser measurement techniques. High speed imaging techniques were used to study the spatial distribution of spray flames, soot formation and oxidation through simultaneous measurements of OH* chemiluminescence and natural soot luminosity, during the luminous combustion process. The amount of un-oxidised soot left in the cylinder after the end of luminous combustion for these fuels were investigated using planar laser induced incandescence (PLII). In addition to PLII, time resolved laser induced incandescence (TR-LII) technique was used simultaneously to explore crank angle resolved variation of primary soot particle size during the expansion stroke. The ignition for RME occurs earlier compared to ULSD, and the early phase of RME combustion proceeds quicker compared to ULSD. The flame lift off length (FLoL) and the length based on the first appearance of soot (SLoL) are longer for RME. The combined effect of relatively longer FLoL and the presence of fuel-bound oxygen reduced the overall soot formation process for RME. PLII data confirmed that the relative amount of soot left in the cylinder after the end of visible luminous combustion is less for RME, and the soot formed are oxidised well within the combustion chamber before it is exhausted out of the engine compared to ULSD. The measured in-cylinder primary soot particles are in the size range between 15 and 35nm and it decreases with crank angle. The sizes of particles generated from the combustion of RME were slightly smaller compared to ULSD.

Experimental and simulation study of in-cylinder strategies for regeneration of lean nitrogen oxide traps in a high-speed direct-injection diesel engine

The use of lean nitrogen oxide traps is an attractive solution for reducing the tailpipe emissions of nitrogen oxides in vehicles with diesel engines. During the operation, nitrogen oxides are stored on the surfaces of lean nitrogen oxide traps, and regeneration of lean nitrogen oxide traps is required for proper operation. In this paper, two in-cylinder combustion strategies for regeneration of lean nitrogen oxide traps were assessed for a high-speed direct-injection diesel engine. In particular, a delayed and extended main strategy and a premixed compression ignition strategy were studied through experiments and simulations. The experimental data were collected from a 1.5 l diesel engine to analyze its combustion, exhaust temperature, fuel consumption, and emission characteristics resulting from either the delayed and extended main strategy or the premixed compression ignition strategy. The results indicated that the premixed compression ignition strategy offered a better fuel economy and lower soot and nitrogen oxide emissions, while the delayed and extended main strategy offered a hotter exhaust temperature and higher production rates of reductant species. In addition, a one-dimensional numerical lean nitrogen oxide trap model was designed and validated to study the efficiency of the surface adsorbents on lean nitrogen oxide traps for each of these two strategies in terms of a reduction in the nitrogen oxide emissions. The simulation results revealed that both strategies can reach a lean nitrogen oxide trap efficiency rate of 100% when the exhaust gas recirculation rate was equal to 30% but that the lean nitrogen oxide trap efficiency rate drops when lower exhaust gas recirculation rates were applied. Overall, the results indicated that the premixed compression ignition strategy performed better than the delayed and extended main strategy in terms of the fuel economy and lower tailpipe emissions.

Study on performance and emissions of a passenger-car diesel engine fueled with butanol–diesel blends

In this work, the commercially available diesel fuel (Bu00), butanol(20%)–diesel(80%) (by vol.) (Bu20), butanol(30%)–diesel(70%) (Bu30), and butanol(40%)–diesel (60%) (Bu40) fuels were tested. Experiments were conducted on a high-speed direct injection (DI) diesel engine for passenger-car application for varied loads at two representative engine speeds. The results showed that butanol–diesel blends slightly increased combustion pressure and accelerated burning rate. As fueled by the Bu40 blend, the maximum power output of the engine cannot be affected. Besides, butanol–diesel blends increased BSFC and brake thermal efficiency. Moreover, the effects of butanol addition on diesel engine exhaust emissions were varied with loads. Under low-load conditions, CO emissions obviously increased while NOx emissions decreased as butanol blending ratio increased. Under high-load conditions, on the contrary, CO emissions decreased but NOx emission increased. For the 40% butanol–diesel blend, in addition, HC emissions were higher than the neat diesel and lower percentage of butanol–diesel blends, especially at low-load. It is interesting that smoke decreased significantly at all conditions with the use of butanol–diesel blends, and the more butanol blending ratio the less smoke. Overall butanol is a potentially promising biofuel, which could be used conveniently up to high blending ratio with diesel fuel in diesel engines.

Evaluation of nitrogen oxide emissions and smoke opacity in a HSDI diesel engine fuelled with palm oil biodiesel

In this paper, an experimental study evaluating engine performance, nitrogen oxide emissions (NOx) and smoke opacity of a HSDI (high speed direct injection) diesel engine fuelled with neat palm oil biodiesel (POB) is presented. Tests were performed in a bench-mounted automotive diesel engine operating under steady state conditions. Conventional diesel fuel was taken as base line or reference fuel. Results show that at full-load operation POB led to a power output decrease between 10% and 17% and an effective specific fuel consumption increase between 14% and 22%. At full-load and low engine speeds an increase of 20% in NOx emissions was measured. However, at the same torque rating and high engine speeds a 6% decrease in such emissions was obtained. At partial-load, NOx emissions always increased using POB, this effect being more pronounced at low speeds. On the other hand, smoke opacity significantly decreased (between 40% and 80%) regardless of engine load. According to the experimental results POB fuelling reduced engine power output, increased fuel consumption, increased slightly efficiency, always decreased smoke opacity, and reduced or increased NOx emissions depending on the engine operation mode.

Experimental investigation of hydraulic effects of two-stage fuel injection on fuel-injection systems and diesel combustion in a high-speed optical common-rail diesel engine

In order to meet the ever more stringent emission standards, significant efforts have been devoted to the research and development of internal combustion engines. The requirements for more efficient and responsive diesel engines have led to the introduction and implementation of multiple injection strategies. However, the effects of such injection modes on the hydraulic systems, such as the high-pressure pipes and fuel injectors, must be thoroughly examined and compensated for since the combustion and the formation of pollutants in direct-injection engines are directly influenced by the spatial and temporal distribution of the injected fuel within the combustion chamber. This study investigated the hydraulic effects of two-stage fuel injection on diesel combustion and emissions. The fuel-injection system was characterised for all the tested strategies through the measurement of the fuel-injection rate and quantity. In particular, the interaction between the two injection events was identified. The effects of two-stage injection, dwell angle and the interactions between two consecutive injection events on the combustion process and the emissions were investigated in a high-speed direct-injection single-cylinder optical diesel engine using heat-release analysis and high-speed fuel spray and combustion visualisation techniques. The results indicated that the two-stage injection strategy has the potential for simultaneous reduction of nitrogen oxide, soot and unburned hydrocarbon emissions. The results suggested that an optimum fuel quantity in the first injection exists, 0–30%, with which simultaneous reduction of nitrogen oxide, soot and unburned hydrocarbon emissions can be achieved with the added benefits of improved engine performance, fuel economy and combustion noise. However, higher soot emissions were produced, mainly due to the interaction between the two consecutive fuel-injection events whereby the fuel sprays during the second injection were injected into burning regions, as well as reduced soot oxidation due to the continuation of the combustion into the expansion stroke.

Combustion and emissions of cottonseed oil and its bio-diesel in blends with either n-butanol or diethyl ether in HSDI diesel engine

This experimental investigation evaluates the combustion and exhaust emission characteristics of cottonseed oil and its (methyl ester) bio-diesel in blends with 20% by vol. of either n-butanol or diethyl ether (DEE), fueling a standard, experimental, single-cylinder, four-stroke, high-speed direct injection (HSDI), ‘Hydra’ diesel engine. The tests are conducted using each of the above fuel blends or neat cottonseed oil or its neat bio-diesel, with the engine operating at three different loads. Fuel consumption, exhaust smoke, nitrogen oxides (NOx), carbon monoxide (CO) and total unburned hydrocarbons (HCs) are measured. The differences in the performance and exhaust emissions of these fuel blends from the baseline operation of the diesel engine, i.e. when working with neat cottonseed oil or its neat bio-diesel, are compared. Fuel injection and combustion chamber pressure diagrams are obtained, and heat release rate analysis of the latter ones is performed revealing some interesting features of the combustion mechanisms. These results and the widely differing physical and chemical properties of n-butanol and DEE against those for the cottonseed oil and its bio-diesel are used to aid the correct interpretation of the observed engine behavior. It is revealed that n-butanol and DEE, which can be produced from biomass (bio-butanol and bio-DEE), when added to the vegetable oil or its bio-diesel improve the behavior of diesel engine.

The effects of split injections on high exhaust gas recirculation low-temperature diesel engine combustion

Diesel engine emissions of oxides of nitrogen and smoke can be reduced simultaneously through the use of high levels of exhaust gas recirculation to achieve low-temperature combustion. However, single fuel injection per cycle diesel low-temperature combustion is also characterized by high fuel consumption and high total unburned hydrocarbons and carbon monoxide emissions. This work focuses on investigating the potential of a split (50/50) main fuel-injection strategy to reduce smoke, total unburned hydrocarbons and carbon monoxide emissions at exhaust gas recirculation levels lower than those required to achieve single-injection diesel low-temperature combustion at a medium-load, medium-speed operating condition. Experiments were performed on a 0.51 l single-cylinder high-speed direct-injection diesel engine running at 1500 r/min at an operating condition corresponding to a gross indicated mean effective pressure of 500 kPa. At this load, exhaust gas recirculation levels of 62% are needed to realize near-zero nitrogen oxide and smoke emissions, but this leads to an unacceptable reduction in thermal efficiency as well as high total unburned hydrocarbons and carbon monoxide emissions. This work compares the effects of split fuel injections at an exhaust gas recirculation level of 52% by volume to those from single injections at exhaust gas recirculation levels of 52% and 62%. The results demonstrate that the combined effects of exhaust gas recirculation rate and split injections can achieve near-zero nitrogen oxide with good thermal efficiency and total unburned hydrocarbons and carbon monoxide emissions much lower than at 62% exhaust gas recirculation. Single injection at this point results in excessive smoke, which can be reduced by over 75% through the split-injection strategy. These results are particularly relevant as they demonstrate very low nitrogen oxide emissions from an engine operation with acceptable thermal efficiency and at practical exhaust gas recirculation levels.