Combustion and emission characteristics of an off-road diesel engine fuelled with biodiesel–diesel blends

In this work, the combustion and emission characteristics were studied in a 186FA diesel engine fuelled with biodiesel–diesel to examine the effect of the percentage of biodiesel in the blends, and the experimental investigation was conducted with various blending ratios of biodiesel under different operating conditions. In addition, the combustion noise of the diesel engine fuelled with biodiesel–diesel was analysed, and then the emission characteristics of NO_x and soot were studied through simulation analysis where the formation rate and distribution of NO_x and soot for pure diesel and B20 fuel were described. Based on the simulation data of the original diesel engine fuelled with B20 fuel, the swirl ratio and fuel injection timing were optimised and the technical measures were suggested to reduce the two different emissions simultaneously. The simulation results showed the emission characteristics were optimal when the swirl ratio was 2.7 and fuel injection timing was 7.5° degree of crank angle before top dead centre respectively.     

Theoretical and experimental study on the performance of a diesel engine fueled with diesel–biodiesel blends

This study reports the effects of engine load and biodiesel percentage on the performance of a diesel engine fueled with diesel–biodiesel blends by experiments and a new theoretical model based on the finite-time thermodynamics (FTT). In recent years, biodiesel utilization in diesel engines has been popular due to depletion of petroleum-based diesel fuel. In this study, performance of a single cylinder, four-stroke, direct injection (DI) diesel engine fueled with diesel–biodiesel mixtures has been experimentally and theoretically investigated. The simulation results agree with the experimental data. After model validation, the effects of engine load and biodiesel percentage on engine performance have been parametrically investigated. The results showed that, effective power increases constantly, effective efficiency increases to a specified value and then starts to decrease with increasing engine load at constant biodiesel percentage and compression ratio. However, effective efficiency increases, effective power decreases to a certain value and then begins to increase with increasing biodiesel percentage at constant equivalence ratio and compression ratio.     

Experimental investigation on the performance and emissions of a diesel engine fuelled with ethanol–diesel blends

An experimental investigation on the application of the blends of ethanol with diesel to a diesel engine was carried out. First, the solubility of ethanol and diesel was conducted with and without the additive of normal butanol (n-butanol). Furthermore, experimental tests were carried out to study the performance and emissions of the engine fuelled with the blends compared with those fuelled by diesel. The test results show that it is feasible and applicable for the blends with n-butanol to replace pure diesel as the fuel for diesel engine; the thermal efficiencies of the engine fuelled by the blends were comparable with that fuelled by diesel, with some increase of fuel consumptions, which is due to the lower heating value of ethanol. The characteristics of the emissions were also studied. Fuelled by the blends, it is found that the smoke emissions from the engine fuelled by the blends were all lower than that fuelled by diesel; the carbon monoxide (CO) were reduced when the engine ran at and above its half loads, but were increased at low loads and low speed; the hydrocarbon (HC) emissions were all higher except for the top loads at high speed; the nitrogen oxides (NO_x) emissions were different for different speeds, loads and blends.     

Characterizing sooting propensity in biofuel–diesel flames

As the world’s oil reserves are limited, and as a partial mitigation of greenhouse gas emission, renewable biofuels are being considered as important contributors to the future fuel supply for the transportation sector. The combustion of biofuel–diesel mixtures in practical engines has been shown to be not only feasible but also favorable due to low particulate emission characteristics. This paper demonstrates quantifiable sooting propensity of biofuel–diesel fuel blends using classical smoke point observations and laser induced-incandescence and laser extinction optical methods. In particular, we study mixtures of 0–25% by volume of soybean biofuel in ultra-low sulfur diesel. Following the ASTM D1322 standard, we find that the maximum flame height at the smoke point condition increases linearly with increasing biofuel fraction. An alternative sooting propensity measurement is needed, however, because high biofuel/diesel blends do not produce a smoke point in the standard wick-fed lamp procedure. Using a fixed flame height, laser-based measurements are generally consistent with smoke point trends, and laser extinction calibrations provide quantitative soot volume fractions. The results show the greatest soot concentration for pure diesel fuel, B0, and the least for a 20% blend by volume of biofuel, B20.     

Performance,emission and combustion characteristic of a multicylinder DI diesel engine running on diesel–ethanol–biodiesel blends of high ethanol content

Feasibility of using high percentage of ethanol in diesel–ethanol blends, with biodiesel as a co-solvent and properties enhancer has been investigated. The blends tested are D70/E20/B10 (blend A), D50/E30/B20 (blend B) D50/E40/B10 (blend C), and Diesel (D100). The blends are prepared to get maximum percentage of oxygen content but keeping important properties such as density, viscosity and Cetane index within acceptable limits. Experiments are conducted on a multicylinder, DI diesel engine, whose original injection timing was 13° CA BTDC. The engine did not run on blends B and C at this injection timing and it was required to advance timing to 18° and 21° CA BTDC to enable the use of blends B and C respectively. However advancing injection timing almost doubled the NO emissions and increased peak firing pressure. The P–θ and net heat release diagrams shows that the combustion process of these blends delayed at low loads but approaches to the diesel fuel at high loads. The comparison of blend results with baseline diesel showed that brake specific fuel consumption increased considerably, thermal efficiency improved slightly, smoke opacity reduced remarkably at high loads. NO variation depends on operating conditions while CO emissions drastically increased at low loads. Blend B which replaced 50% diesel and having oxygen content up to 12.21% by weight has given satisfactory performance for steady state running mode up to 1600 RPM however, it does not showed any benefit on peak smoke emission during free acceleration test.     

Bio-diesel as an alternative fuel for diesel engines—A review

The present review aims to study the prospects and opportunities of introducing vegetable oils and their derivatives as fuel in diesel engines. In our country the ratio of diesel to gasoline fuel is 7:1, depicting a highly skewed situation. Thus, it is necessary to replace fossil diesel fuel by alternative fuels. Vegetable oils present a very promising scenario of functioning as alternative fuels to fossil diesel fuel. The properties of these oils can be compared favorably with the characteristics required for internal combustion engine fuels. Fuel-related properties are reviewed and compared with those of conventional diesel fuel. Peak pressure development, heat release rate analysis, and vibration analysis of the engine are discussed in relation with the use of bio-diesel and conventional diesel fuel. Optimization of alkali-catalyzed transesterification of Pungamia pinnata oil for the production of bio-diesel is discussed. Use of bio-diesel in a conventional diesel engine results in substantial reduction in unburned hydrocarbon (UBHC), carbon monoxide (CO), particulate matters (PM) emission and oxide of nitrogen. The suitability of injection timing for diesel engine operation with vegetable oils and its blends, environmental considerations are discussed. Teardown analysis of bio-diesel B20-operated vehicle are also discussed.     

Performance and combustion characteristics of biodiesel–diesel–methanol blend fuelled engine

An experimental investigation was conducted to evaluate the effects of using methanol as additive to biodiesel–diesel blends on the engine performance, emissions and combustion characteristics of a direct injection diesel engine under variable operating conditions. BD50 (50% biodiesel and 50% diesel in vol.) was prepared as the baseline fuel. Methanol was added to BD50 as an additive by volume percent of 5% and 10% (denoted as BDM5 and BDM10). The results indicate that the combustion starts later for BDM5 and BDM10 than for BD50 at low engine load, but is almost identical at high engine load. At low engine load of 1500 r/min, BDM5 and BDM10 show the similar peak cylinder pressure and peak of pressure rise rate to BD50, and higher peak of heat release rate than that of BD50. At low engine load of 1800 r/min, the peak cylinder pressure and the peak of pressure rise rate of BDM5 and BDM10 are lower than those of BD50, and the peak of heat release rate is similar to that of BD50. The crank angles at which the peak values occur are later for BDM5 and BDM10 than for BD50. At high engine load, the peak cylinder pressure, the peak of pressure rise rate and peak of heat release rate of BDM5 and BDM10 are higher than those of BD50, and the crank angle of peak values for all tested fuels are almost same. The power and torque outputs of BDM5 and BDM10 are slightly lower than those of BD50. BDM5 and BDM10 show dramatic reduction of smoke emissions. CO emissions are slightly lower, and NO_x and HC emissions are almost similar to those of BD50 at speed characteristic of full engine load.     

Exergetic and thermoeconomic analyses of diesel engine powered cogeneration: Part 1 – Formulations

This paper is part 1 of the study on the energy, exergy, and exergoeconomic analysis of diesel engine powered cogeneration (DEPC). Part 1 presents the formulation developed for such a comprehensive analysis while part 2 is an application of the developed formulation that considers an actual cogeneration power plant. Compression ignition engine powered cogeneration application is among the most efficient simple cycle power generation plants where the efficiencies are around 50%. The DEPC is mostly preferred in regions where natural gas is not available or not preferable because of high unit prices. In this paper, a DEPC plant is considered with all associated components. Mass, energy, and exergy balances are applied to each system component and subsystem. Exergy balance formulations are aimed to yield exergy destructions. Various efficiencies based on both energy and exergy methods and the performance assessment parameters are defined for both the system components and the entire cogeneration plant. The formulations for the cost of products, and cost formation and allocation within the system are developed based on both energy and exergy (i.e., exergoeconomic analysis). The cost analyses formulated here have significant importance to obtain the optimum marketing price of the product of thermal systems to maximize the benefit and/or minimize the cost.     

Exergetic and thermoeconomic analyses of diesel engine powered cogeneration: Part 2 – Application

This paper is Part 2 of the study on the exergetic and thermoeconomic analysis of diesel engine powered cogeneration (DEPC) systems. In Part 1, formulations and procedure for such a comprehensive analysis are provided while this paper provides an application of the developed formulation that considers an actual DEPC plant installed in Gaziantep, Turkey. The plant has a total installed electricity and steam generation capacities of 25.3 MW and 8.1 tons/h at 170 °C, respectively. Exergy destructions, exergy efficiencies, exergetic cost allocations, and various exergoeconomic performance parameters are determined for the entire plant and its components. The exergy efficiency of the plant is determined to be 40.6%. The exergoeconomic analysis is based on specific cost method (SPECO) and it is determined that the specific unit exergetic cost of the power produced by the plant is 10.3 $/GJ.     

Experimental investigation and combustion analysis of a direct injection dual-fuel diesel–natural gas engine

A single-cylinder diesel engine has been converted into a dual-fuel engine to operate with natural gas together with a pilot injection of diesel fuel used to ignite the CNG–air charge. The CNG was injected into the intake manifold via a gas injector on purpose designed for this application. The main performance of the gas injector, such as flow coefficient, instantaneous mass flow rate, delay time between electrical signal and opening of the injector, have been characterized by testing the injector in a constant-volume optical vessel. The CNG jet structure has also been characterized by means of shadowgraphy technique.     

Novel microemulsion fuel additive Ce–Ru–O catalysts with algae biofuel on diesel engine testing

Biodiesels derived from microalgae oil promise to be an alternative for the conventional diesel fuel due to their similarity in properties. In this present work, Ce–Ru–O catalysts are used as an additive to the NOME in the form of an emulsion. A single-cylinder, four-stroke direct injection compression ignition engine is made to run on B20+CeO₂, and B20 dozed with different dosage levels of Ce_0.95Ru_0.05O₂, Ce_0.9Ru_0.1O₂, and Ce_0.8Ru_0.2O₂ microemulsions. Ce–Ru–O at different concentrations is used to study the effect of metal oxide on emission characteristics of the fuel. Experimental results show that addition of microemulsion has a positive effect on emission characteristics and also acts as an oxidation catalyst.     

Ammonia–water bottoming cycles: a comparison between gas engines and gas diesel engines as prime movers

Ammonia–water cycles can produce more power than steam Rankine cycles in several applications. One of these applications is as a bottoming cycle to internal combustion engines. In the present study, ammonia–water bottoming cycle configurations for spark-ignition gas engines and compression-ignition gas diesel engines have been compared. Single-pressure Rankine cycles have been used as a basis for the comparison. Low heat source temperatures should increase the difference in power output between the ammonia–water cycle and the Rankine cycle. However, in this study, the results of the simulations show different trends. In most cases, the ammonia–water bottoming cycles with gas engines as prime movers generate more power compared to a Rankine cycle than when gas diesel engines are the prime movers. The temperature of the most important waste heat source, the exhaust gas, is approximately 100°C higher for the gas engines than for the gas diesel engines. Therefore, for the gas engines, most of the waste heat available to a bottoming cycle is in the form of relatively high-temperature exhaust gas, while for the gas diesel engines more of the waste heat is in the form of relatively low-temperature heat sources.     

Soot formation from a distillation cut of a Fischer–Tropsch diesel fuel: A shock tube study

The kinetics of soot formation from Fischer–Tropsch (FT) fuels was studied in a heated shock tube under homogeneous conditions. Soot induction delay time and soot yield were measured between 10 and 17 atm using a distillation cut at 403 K of a Fischer–Tropsch fuel diesel. Two fuel concentrations were investigated in pyrolysis: 0.2% and 0.4% FT in Ar. Equivalence ratios (Φ) = 18 and 5 were also investigated for the highest fuel concentration. During this study, a second growth of the soot volume fraction profile was observed with the highest fuel concentration in pyrolysis and at Φ = 18. It was shown that this second growth appears only at temperatures higher than the temperature at which the soot yield is maximum. Under the conditions investigated, the soot induction delay time was found not to be very sensitive to the fuel concentration. A careful analysis of the soot volume fraction profiles showed that this finding was linked to the measurement method usually adopted. Nevertheless, this method was found adequate for a systematic comparison between different fuels or for an investigation of the oxygen concentration effects. The addition of oxygen to the mixture promotes soot formation in its early stages by decreasing the soot induction delay time. A shift of the soot yield curve toward lower temperatures was also observed. Moreover, oxygen addition reduces the amount of soot produced. This reduction is proportional to the O₂ concentration. Comparisons with literature data showed that a Fischer–Tropsch fuel primarily composed of n-paraffins can be correctly represented by an n-paraffin with a molecular size comparable to the average molecular size of the Fischer–Tropsch fuel. The maximum soot yield of the Fischer–Tropsch distillation cut studied was not significantly different from that of a diesel fuel surrogate previously studied (Mathieu et al., Combust. Flame 156 (2009) 1576–1586).     

Characteristics analysis of carbon nanowires in diesel: Neochloris oleoabundans algae oil biodiesel–ethanol blends in a CI engine

The present work is dedicated to the study of diesel–biodiesel–ethanol blends in a diesel engine using carbon nanowires additives of various concentrations. Algae oil from microalgae has the possibility of becoming a sustainable fuel source as biodiesel. The Neochloris oleoabundans algal oil was extracted by the mechanical extraction method. The transesterification reaction of algal oil with methanol and base catalyst was used for the production of biodiesel. Experimental investigation results were studied for various parameters such as exhaust emission of carbon monoxide, hydrocarbon, oxides of nitrogen gases, and smoke.     

Performance and emission evaluation of a CI engine fueled with preheated raw rapeseed oil (RRO)–diesel blends

Many studies are still being carried out to find out surplus information about how vegetable based oils can efficiently be used in compression ignition engines. Raw rapeseed oil (RRO) was used as blended with diesel fuel (DF) by 50% oil–50% diesel fuel in volume (O50) also as blended with diesel fuel by 20% oil–80% diesel fuel in volume (O20). The test fuels were used in a single cylinder, four stroke, naturally aspirated, direct injection compression ignition engine. The effects of fuel preheating to 100 °C on the engine performance and emission characteristics of a CI engine fueled with rapeseed oil diesel blends were clarified. Results showed that preheating of RRO was lowered RRO’s viscosity and provided smooth fuel flow Heating is necessary for smooth flow and to avoid fuel filter clogging. It can be achieved by heating RRO to 100 °C. It can also be concluded that preheating of the fuel have some positive effects on engine performance and emissions when operating with vegetable oil.     

Catalytic exhaust gas fuel reforming for diesel engines—effects of water addition on hydrogen production and fuel conversion efficiency

Previous work in our laboratory has shown that the exhaust gas assisted fuel reforming process has the potential to provide a solution to the diesel engine exhaust emission problems. When simulated reformer product gas rich in hydrogen is fed to the engine, a reduction of both NO_x and smoke emissions can be achieved. In this paper, the optimisation of the reforming process by water addition in the reactor is presented. Using a prototype catalyst at 290°C reactor inlet temperature, up to 15% more hydrogen in the reformer product was obtained compared to operation without water. The process has been found to be mainly a combination of the fuel oxidation, steam reforming and water gas shift reactions. The reforming process efficiency has been shown to improve considerably with water addition up to a certain level after which the adverse effects of the exothermic water gas shift reaction become significant.     

Effect of engine parameters and type of gaseous fuel on the performance of dual-fuel gas diesel engines—A critical review

Petroleum resources are finite and, therefore, search for their alternative non-petroleum fuels for internal combustion engines is continuing all over the world. Moreover gases emitted by petroleum fuel driven vehicles have an adverse effect on the environment and human health. There is universal acceptance of the need to reduce such emissions. Towards this, scientists have proposed various solutions for diesel engines, one of which is the use of gaseous fuels as a supplement for liquid diesel fuel. These engines, which use conventional diesel fuel and gaseous fuel, are referred to as ‘dual-fuel engines’. Natural gas and bio-derived gas appear more attractive alternative fuels for dual-fuel engines in view of their friendly environmental nature. In the gas-fumigated dual-fuel engine, the primary fuel is mixed outside the cylinder before it is inducted into the cylinder. A pilot quantity of liquid fuel is injected towards the end of the compression stroke to initiate combustion. When considering a gaseous fuel for use in existing diesel engines, a number of issues which include, the effects of engine operating and design parameters, and type of gaseous fuel, on the performance of the dual-fuel engines, are important. This paper reviews the research on above issues carried out by various scientists in different diesel engines. This paper touches upon performance, combustion and emission characteristics of dual-fuel engines which use natural gas, biogas, producer gas, methane, liquefied petroleum gas, propane, etc. as gaseous fuel. It reveals that ‘dual-fuel concept’ is a promising technique for controlling both NO_x and soot emissions even on existing diesel engine. But, HC, CO emissions and ‘bsfc’ are higher for part load gas diesel engine operations. Thermal efficiency of dual-fuel engines improve either with increased engine speed, or with advanced injection timings, or with increased amount of pilot fuel. The ignition characteristics of the gaseous fuels need more research for a long-term use in a dual-fuel engine. It is found that, the selection of engine operating and design parameters play a vital role in minimizing the performance divergences between an existing diesel engine and a ‘gas diesel engine’.     

Impact of Carbon Nanotubes and Di-Ethyl Ether as additives with biodiesel emulsion fuels in a diesel engine – An experimental investigation

In the current global energy scenario, fossil fuels face challenges with regards to exorbitant demand, environmental hazards and escalating costs. In this regard, the technical community is in quest for alternative resources. In this context, biodiesel fuel is potentially considered as alternative fuels for compression ignition engines. Hence, in this current investigation, biodiesel and biodiesel emulsions are prepared from a vegetable oil and further subjected for the blending with potential additives such as CNT (Carbon Nanotubes) and DEE (Di-Ethyl Ether) to improve the working attributes of the diesel engine. The entire investigation was carried out in five stages. In the first stage, both pure diesel and biodiesel (derived from jatropha oil) fuels were tested in the diesel engine to obtain baseline readings. In the second stage, water–biodiesel emulsion fuel was prepared in the proportion of 91% of biodiesel, 5% of water and 4% of emulsifiers (by volume). In the third stage, 50 ppm of CNT, 50 ml of DEE and combined mixture of CNT+DEE (50 ppm CNT+50 ml DEE) were mixed with the water–biodiesel emulsion fuel separately to prepare the CNT and DEE blended water–biodiesel emulsion fuels respectively. In fourth stage, the prepared emulsion fuels were subjected to stability investigations. In the fifth stage, all the prepared stable emulsion fuels were subjected for experimental testing in a diesel engine. It was observed that the CNT and DEE blended biodiesel emulsion fuels reflected better performance, emission and combustion attributes than that of pure diesel and biodiesel. At the full load, the brake thermal efficiency, NO and smoke emission of CNT+DEE fuels was 28.8%, 895 ppm and 36%, whereas it was 25.2%, 1340 ppm and 71% for pure diesel respectively. It was also observed that on adding CNT and DEE with the biodiesel emulsion fuels, the ignition delay was shortened and henceforth, the additive blended biodiesel emulsion fuels exhibited higher brake thermal efficiency and reduced emissions (NO, smoke) than that of pure diesel and biodiesel.     

Techno-economic evaluation of off-grid hybrid photovoltaic–diesel–battery power systems for rural electrification in Saudi Arabia—A way forward for sustainable development

The burning of depleting fossil fuels for power generation has detrimental impact on human life and climate. In view of this, renewable solar energy sources are being increasingly exploited to meet the energy needs. Moreover, solar photovoltaic (PV)–diesel hybrid system technology promises lot of opportunities in remote areas which are far from utility grid and are driven by diesel generators. Integration of PV systems with the diesel plants is being disseminated worldwide to reduce diesel fuel consumption and to minimize atmospheric pollution. The Kingdom of Saudi Arabia (K.S.A.) being endowed with high intensity of solar radiation, is a prospective candidate for deployment of PV systems. Also, K.S.A. has large number of remote scattered villages. The aim of this study is to analyze solar radiation data of Rafha, K.S.A., to assess the techno-economic feasibility of hybrid PV–diesel–battery power systems to meet the load requirements of a typical remote village Rawdhat Bin Habbas (RBH) with annual electrical energy demand of 15,943 MWh. Rafha is located near RBH. The monthly average daily global solar radiation ranges from 3.04 to 7.3 kWh/m². NREL's HOMER software has been used to perform the techno-economic evaluation. The simulation results indicate that for a hybrid system composed of 2.5 MWp capacity PV system together with 4.5 MW diesel system (three 1.5 MW units) and a battery storage of 1 h of autonomy (equivalent to 1 h of average load), the PV penetration is 27%. The cost of generating energy (COE, US$/kWh) from the above hybrid system has been found to be 0.170$/kWh (assuming diesel fuel price of 0.1$/l). The study exhibits that the operational hours of diesel generators decrease with increase in PV capacity. The investigation also examines the effect of PV/battery penetration on COE, operational hours of diesel gensets. Concurrently, emphasis has been placed on: un-met load, excess electricity generation, percentage fuel savings and reduction in carbon emissions (for different scenarios such as: PV–diesel without storage, PV–diesel with storage, as compared to diesel-only situation), COE of different hybrid systems, etc. The decrease in carbon emissions by using the above hybrid system is about 24% as compared to the diesel-only scenario.     

Combustion and emissions control in diesel–methane dual fuel engines: The effects of methane supply method combined with variable in-cylinder charge bulk motion

In this paper, the results of an extensive experimental campaign about dual fuel combustion development and the related pollutant emissions are reported, paying particular attention to the effect of both the in-cylinder charge bulk motion and methane supply method.A diesel common rail research engine was converted to operate in dual fuel mode and, by activating/deactivating the two different inlet valves of the engine (i.e. swirl and tumble), three different bulk flow structures of the charge were induced inside the cylinder. A methane port injection method was proposed, in which the gaseous fuel was injected into the inlet duct very close to the intake valves, in order to obtain a stratified-like air–fuel mixture up to the end of the compression stroke. For comparison purposes, a homogeneous-like air–fuel mixture was obtained injecting methane more upstream the intake line. Combining the different positions of the methane injector and the three possible bulk flow structures, seven different engine inlet setup were tested. In this way, it was possible to evaluate the effects on dual fuel combustion due to the interaction between methane injector position and charge bulk motion. In addition, methane injection pressure and diesel pilot injection parameters were varied setting the engine at two operating conditions.For some interesting low load tests, the combustion development was studied more in detail by means of direct observation of the process, using an in-cylinder endoscope and a digital CCD camera. Each combustion image was post-processed by a dedicated software, in order to extract only those portions with flame presence and to calculate an average luminance value over the whole frame. These luminance values, chosen as indicators of the combustion intensity, were represented over crank angle position and, then, an analysis of the resulting curves was performed.Results showed that the charge bulk motion associated to the swirl port, improving the charge mixing of the diesel spray and the propagation of the turbulent flame fronts, is capable to enhance the oxidation of air–methane mixture, both at low and high engine loads. Furthermore, at low loads, the analysis of combustion images and luminance curves showed that methane port injection can significantly affect the intensity and the spreading of the flame during dual fuel combustion, especially when a suitable in-cylinder bulk motion is obtained.Concerning the engine emissions, some correlations with what observed during the analysis of the combustion development were found. Furthermore, it was revealed that, for several combinations of the engine operating parameters, methane port injection was always associated to the lowest emission levels, demonstrating that this methane supply method is a very effective strategy to reduce unburned hydrocarbons and nitric oxides concentrations, especially when implemented with variable intake geometry systems.