Experimental investigation on dual fuel operation of acetylene in a DI diesel engine

Depletion of fossils fuels and environmental degradation have prompted researchers throughout the world to search for a suitable alternative fuel for diesel engine. One such step is to utilize renewable fuels in diesel engines by partial or total replacement of diesel in dual fuel mode. In this study, acetylene gas has been considered as an alternative fuel for compression ignition engine, which has excellent combustion properties.Investigation has been carried out on a single cylinder, air cooled, direct injection (DI), compression ignition engine designed to develop the rated power output of 4.4 kW at 1500 rpm under variable load conditions, run on dual fuel mode with diesel as injected primary fuel and acetylene inducted as secondary gaseous fuel at various flow rates. Acetylene aspiration resulted in lower thermal efficiency. Smoke, HC and CO emissions reduced, when compared with baseline diesel operation. With acetylene induction, due to high combustion rates, NO_x emission significantly increased. Peak pressure and maximum rate of pressure rise also increased in the dual fuel mode of operation due to higher flame speed. It is concluded that induction of acetylene can significantly reduce smoke, CO and HC emissions with a small penalty on efficiency.     

Experimental investigation on the combustion and exhaust emission characteristics of biogas-biodiesel dual-fuel combustion in a CI engine

An experimental investigation was performed to study the influence of dual-fuel combustion characteristics on the exhaust emissions and combustion performance in a diesel engine fueled with biogas-biodiesel dual-fuel. In this work, the combustion pressure and the rate of heat release were evaluated under various conditions in order to analyze the combustion and emission characteristics for single-fuel (diesel and biodiesel) and dual-fuel (biogas-diesel and biogas-biodiesel) combustion modes in a diesel engine. In addition, to compare the engine performances and exhaust emission characteristics with combustion mode, fuel consumption, exhaust gas temperature, efficiency, and exhaust emissions were also investigated under various test conditions. For the dual-fuel system, the intake system of the test engine was modified to convert into biogas and biodiesel of a dual-fueled combustion engine. Biogas was injected during the intake process by two electronically controlled gas injectors, which were installed in the intake pipe.The results of this study showed that the combustion characteristics of single-fuel combustion for biodiesel and diesel indicated the similar patterns at various engine loads. In dual-fuel mode, the peak pressure and heat release for biogas-biodiesel were slightly lower compared to biogas-diesel at low load. At 60% load, biogas-biodiesel combustion exhibited the slightly higher peak pressure, rate of heat release (ROHR) and indicated mean effective pressure (IMEP) than those of diesel. Also, the ignition delay for biogas-biodiesel indicated shortened trends compared to ULSD dual-fueling due to the higher cetane number (CN) of biodiesel. Significantly lower NO_x emissions were emitted under dual-fuel operation for both cases of pilot fuels compared to single-fuel mode at all engine load conditions. Also, biogas-biodiesel provided superior performance in reductions of soot emissions due to the absence of aromatics, the low sulfur, and oxygen contents for biodiesel.     

Effect of variation in LPG composition on emissions and performance in a dual fuel diesel engine

This paper investigates the effect of variation in LPG composition on emissions and performance characteristics in a dual fuel engine run on diesel fuel and five gaseous fuel of LPG with different composition. To quantify the best LPG composition for dual fuel operation especially in order to improve the exhaust emissions quality while maintaining high thermal efficiency comparable to a conventional diesel engine, a two-cylinder, naturally aspirated, four-stroke, DI diesel engine converted to run as pilot-injected dual fuel engine. The tests and data collection were performed under various conditions of load at constant engine speed. From the results, it is observed that the exhaust emissions and fuel conversion efficiency of the dual fuel engine are found to be affected when different LPG composition is used as higher butane content lead to lower NO_x levels while higher propane content reduces CO levels. Fuel #3 (70% propane, 30% butane) with mass fraction 40% substitution of the diesel fuel was the best LPG composition in the dual fuel operation except that at part loads. Also, tests were made for fuel #3-diesel blend in the dual fuel operation at part loads to improve the engine performances and exhaust emissions by using the Exhaust Gas Recirculation (EGR) method.     

Investigation on the fuel spray and emission reduction characteristics for dimethyl ether (DME) fueled multi-cylinder diesel engine with common-rail injection system

The aim of this study is to investigate the effects of dimethyl ether (DME) fuel on the engine performance and the exhaust emission reduction characteristics in a DME fueled four-cylinder diesel engine with a common rail injection system, as well as an injection characteristics and a spray behavior. The injection rate meter and the spray visualization system are utilized for the analysis of the injection characteristics and the spray behavior. Also, the modified four-cylinder diesel engine with 1.6 liter engine size is used for the investigation of the engine performance and the exhaust emission reduction characteristics of DME fuel.Based on the experimental investigation, it revealed that the injection quantity of DME fuel was larger than that of the ultra low sulfur diesel (ULSD) due to the high return fuel pressure at the same injection pressure and energizing duration. In this case, the injection quantity of DME fuel is increased by extension of real injection duration due to return fuel pressure.In combustion characteristics, the peak combustion pressure and the ignition delay of DME fuel are higher and faster than those of ULSD, respectively. The NO_x emission of DME fuel shows slightly higher than that of ULSD at the same engine load condition, and the soot emission of DME fuel is nearly zero level. The oxygenated component and volatility of DME resulted in HC and CO emissions that were lower than those of diesel.     

Performance, combustion and emissions of a diesel engine operated with reformed EGR. Comparison of diesel and GTL fuelling

In this work, the effects of a standard ultra-low sulphur diesel (ULSD) fuel and a new, ultra-clean synthetic GTL (gas-to-liquid) fuel on the performance, combustion and emissions of a single-cylinder, direct injection, diesel engine were studied under different operating conditions with addition of simulated reformer product gas, referred to as reformed EGR (REGR). For this purpose various levels of REGR of two different compositions were tested. Tests with standard EGR were also carried out for comparison. Experiments were performed at four steady state operating conditions and the brake thermal efficiency, combustion process and engine emission data are presented and discussed. In general, GTL fuel resulted in a higher brake thermal efficiency compared to ULSD but the differences depended on the engine condition and EGR/REGR level and composition. The combustion pattern was significantly modified when the REGR level was increased. Although the extent of the effects of REGR on emissions depended on the engine load, it can be generally concluded that an optimal combination of GTL and REGR significantly improved both NO_x and smoke emissions. In some cases, NO_x and smoke emission reductions of 75% and 60%, respectively, were achieved compared to operation with ULSD without REGR. This offers a great potential for engine manufacturers to meet the requirements of future emission regulations.     

Co-gasification of coal and wood in a dual fluidized bed gasifier

In the last decade the reduction of CO₂ emissions from fossil fuels became a worldwide topic. Co-gasification of coal and wood provides an opportunity to combine the advantages of the well-researched usage of fossil fuels such as coal with CO₂-neutral biomass. Gasification itself is a technology with many advantages. The producer gas can be used in many ways; for electric power generation in a gas engine or gas turbine, for Fischer-Tropsch synthesis of liquid fuels and also for production of gaseous products such as synthetic natural gas (bio SNG). Moreover, the use of the producer gas in fuel cells is under investigation. The mixture of coal and wood leads to the opportunity to choose the gas composition as best befits the desired process. Within this study the focus of investigation was of gasification of coal and wood in various ratios and the resulting changes in producer gas composition. Co-gasification of coal and wood leads to linear producer gas composition changes with linear changing load ratios (coal/wood). Hydrogen concentrations rise with increasing coal ratio, while CO concentrations decrease. Due to the lower sulfur and nitrogen content of wood, levels of the impurities NH₃ and H₂S in the producer gas fall with decreasing coal ratio. It is also shown that the majority of sulfur is released in the gasification zone and, therefore, no further cleaning of the flue gas is necessary. All mixture ratios, from 100 energy% to 0 energy% coal, performed well in the 100 kW dual fluidized bed gasifier. Although the gasifier was originally designed for wood, an addition of coal as fuel in industrial sized plants based on the same technology should pose no problems.     

Vegetable oils and animal fats as alternative fuels for diesel engines with dual fuel operation

Vegetable oils and animal fats are applicable as fuels in standard diesel engines after having adapted the fuel system for electronically controlled dual fuel regime oil/fat-fossil diesel. In this contribution, performance and emission characteristics of the engines running on rapeseed oil, lard, or chicken fat are given and compared to those of fossil diesel and fatty acid methyl esters. The results of engine tests of these fuels show a decrease in maximum power and maximum torque in comparison to fossil diesel due to a lower energy content of triacylglycerols. These values are influenced also by a type of the engine used at testing. When compared to fossil diesel, the opacity of oil/fat based fuels is higher for an engine with lower injection pressures while it is lower for an engine with higher injection pressures. The level of both controlled and uncontrolled emissions is low for all tested biofuels and is low also for the reference fossil diesel. The results of performance and emission tests for rapeseed oil containing 3 and 6 vol.% of anhydrous ethanol are comparable to those obtained for pure oil. In this paper, practical experiences based on long-term operation of adapted vehicle fleet fuelled with oil/fat-fossil diesel are mentioned.     

Experimental analysis of alternative fuel impact on a new “torque-controlled” light-duty diesel engine for passenger cars

The present paper describes the results of an experimental study performed burning alternative fuels, different per quality and feedstock, in a modern diesel engine compliance the Euro 5 emission standards. Three alternative fuels were tested on the engine and compared with a reference fossil fuel in terms of combustion characteristics, fuel consumption, noise and emissions. The alternative fuels were two biodiesels (RME and SME) and a Fischer-Tropsh (GTL), while the reference fuel was an EU certification diesel fuel. The engine employed in the study was a light-duty diesel engine developed for passenger car and light truck application, and equipped with the new generation ECU able to drive the engine under “torque-controlled” mode by means of instrumented glow-plugs with pressure sensor. The experiments were carried out in a fully instrumented test bench fuelling the engine with the various fuels. The tests were done in a wide range of engine operation points for the complete characterization of the biodiesels performance in the NEDC cycle. Moreover, the trade-off NO_x-PM by EGR sweep in the three most critical test points for the engine emission performance was carried out for all fuels. The test methodology was selected carefully in order to evaluate the interaction between the fuel quality and the engine management strategy. The results put in evidence a strong interaction between the alternative fuel quality and the engine control mode highlighting the great benefits reachable by exploiting simultaneously the alternative fuel quality and the flexibility of the new engine management strategies.     

Comparison of emissions of a direct injection diesel engine operating on biodiesel with emulsified and fumigated methanol

Biodiesel is an alternative fuel for internal combustion engines. It can reduce carbon monoxide (CO), hydrocarbon (HC) and particulate matter (PM) emissions, compared with diesel fuel, but there is also an increase in nitrogen oxides (NO_x) emission. This study is aimed to compare the effect of applying a biodiesel with either 10% blended methanol or 10% fumigation methanol. The biodiesel used in this study was converted from waste cooking oil. Experiments were performed on a 4-cylinder naturally aspirated direct injection diesel engine operating at a constant speed of 1800 rev/min with five different engine loads. The results indicate a reduction of CO₂, NO_x, and particulate mass emissions and a reduction in mean particle diameter, in both cases, compared with diesel fuel. It is of interest to compare the two modes of fueling with methanol in combination with biodiesel. For the blended mode, there is a slightly higher brake thermal efficiency at low engine load while the fumigation mode gives slightly higher brake thermal efficiency at medium and high engine loads. In the fumigation mode, an extra fuel injection control system is required, and there is also an increase in CO, HC and NO₂ (nitrogen dioxide) and particulate emissions in the engine exhaust, which are disadvantages compared with the blended mode.     

Biodiesel engine performance and emissions in low temperature combustion

Engine performance and emission comparisons were made between the use of soy, Canola and yellow grease derived B100 biodiesel fuels and an ultra-low sulphur diesel fuel in the high load engine operating conditions. Compared to the diesel fuel engine-out emissions of nitrogen oxides (NO_x), a high-cetane number (CN) biodiesel fuel produced comparable NO_x while the biodiesel with a CN similar to the diesel fuel produced relatively higher NO_x at a fixed start of injection. The soot, carbon monoxide and un-burnt hydrocarbon emissions were generally lower for the biodiesel-fuelled engine. Exhaust gas recirculation (EGR) was then extensively applied to initiate low temperature combustion (LTC) mode at medium and low load conditions. An intake throttling valve was implemented to increase the differential pressure between the intake and exhaust in order to increase and enhance the EGR. Simultaneous reduction of NO_x and soot was achieved when the ignition delay was prolonged by more than 50% from the case with 0% EGR at low load conditions. Furthermore, a preliminary ignition delay correlation under the influence of EGR at steady-state conditions was developed. The correlation considered the fuel CN and oxygen concentrations in the intake air and fuel. The research intends to achieve simultaneous reductions of NO_x and soot emissions in modern production diesel engines when biodiesel is applied.     

Influence of ethanol blends on the combustion performance and exhaust emission characteristics of a four-cylinder diesel engine at various engine loads and injection timings

The aim of this work is to investigate the effect of ethanol blending to diesel fuel on the combustion and exhaust emission characteristics of a four-cylinder diesel engine with a common-rail injection system. The overall spray characteristics, such as the spray tip penetration and the spray cone angle, were studied with respect to the ethanol blending ratio. A spray visualization system and a four-cylinder diesel engine equipped with a combustion and emission analyzer were utilized so as to analyze the spray and exhaust emission characteristics of the ethanol blending diesel fuel. Ethanol blended diesel fuel has a shorter spray tip penetration when compared to pure diesel fuel. In addition, the spray cone angle of ethanol blended fuels is larger. It is believed that the lower fuel density of ethanol blended fuels affects the spray characteristics. When the ethanol blended fuels are injected around top dead center (TDC), they exhibit unstable ignition characteristics because the higher ethanol blending ratio causes a long ignition delay. An advance in the injection timing also induces an increase in the combustion pressure due to the sufficient premixed duration. In a four-cylinder diesel engine, an increase in the ethanol blending ratio leads to a decrease in NO_x emissions due to the high heat of evaporation of ethanol fuel, however, CO and HC emissions increase. In addition, the CO and HC emissions exhibit a decreasing trend according to an increase in the engine load and an advance in the injection timing.     

Influence of Methanol–Biodiesel Blends on the Particulate Emissions of a Direct Injection Diesel Engine

In this study, Euro V diesel fuel, biodiesel, and methanol–biodiesel blends were tested in a 4-cylinder direct-injection diesel engine to investigate the combustion characteristics and particulate emissions of the diesel engine under five engine loads at the maximum torque engine speed of 1800 rpm. Compared with Euro V diesel fuel, biodiesel gives lower and earlier heat release rate. For the blended fuels, the peak heat release rate becomes higher and retarded. With regard to particulate mass concentration, biodiesel generates less than Euro V diesel fuel, while the blended fuels result in significant reduction especially at high engine loads. Compare with Euro V diesel fuel, the total particle number concentration of using biodiesel is always higher while the geometric mean diameter (GMD) of the particles is lower. With the blended fuel, the total number concentration and GMD decrease in comparison with pure biodiesel. Further analysis shows that the difference between the total number concentration of biodiesel and Euro V diesel fuel is in particles smaller than 50 nm rather than in the larger particles. The use of methanol–biodiesel blends, compared with biodiesel, could reduce the number concentration of all sizes. A comparison between the particulate mass emission and total particulate number concentration with the mass of fuel burned in the diffusion mode show that they are strongly related to each other, even for the blended fuel.     

Effect of a narrow fuel spray angle and a dual injection configuration on the improvement of exhaust emissions in a HCCI diesel engine

The aim of this work was to investigate the effect of narrow fuel spray angle injection and dual injection strategy on the exhaust emissions of a common-rail diesel engine. To achieve successful homogeneous charge compression ignition by an early timing injection, a narrowed spray cone angle injector and a reduced compression ratio were employed. The combination of homogeneous charge compression ignition (HCCI) combustion and conventional diesel combustion was studied to examine the exhaust emission and combustion characteristics of the engine under various fuel injection parameters, such as injection timings of the first and second spray.The results showed that a dual injection strategy consisting of an early timing for the first injection for HCCI combustion and a late timing for the second injection was effective to reduce the NO_x emissions while it suppress the deterioration of the combustion efficiency caused by the HCCI combustion.     

Experimental investigations of long stick wood gasification in a bottom lit updraft fixed bed gasifier

Based on the experience of the gasifier users on the efforts and energy for wood chip preparation in a typical gasifier, we have embarked on the development of a gasifier suitable to work with long stick woody biomass as the feed materials. In the context of the impact of gasifiers, as decentralized energy delivery devices such an approach, it is hoped, would be an attractive option in rural areas both in domestic and industrial sectors. In the present paper in the gasifier operation, there is a fixed quantity of char that is combusted to gasify a fixed amount of wood, and the gasifier does not operate in a steady state manner. In this present work, focus is made on the development of a gasifier using long sticks of wood as feed materials. With this concept, a 10 kW thermal output power gasifier is designed and constructed. The gas and airflows can be converted to the air/fuel ratio, the most important aspect of gasifier operation. The air/fuel ratio shows operation in a combustion mode at start up, a gasification mode for the middle part of the run and a charcoal gasification mode at the end of the run. Since the interest here is exploring and validating of this concept, a bottom lit updraft gasifier is designed mainly to look at the gas yield and other favourable factors and to use this gas so obtained for thermal applications. The rate of feed was between 9 and 10 kg/h and continuous operation for 5 h was made in a couple of runs to study the performance. In this paper we report the salient features of our efforts and results, yielding a gasifier efficiency of 73%.     

Performance, emission and combustion evaluation of soapnut oil-diesel blends in a compression ignition engine

Soapnut (Sapindus mukorossi) oil, a nonedible straight vegetable oil was blended with petroleum diesel in various proportions to evaluate the performance and emission characteristics of a single cylinder direct injection constant speed diesel engine. Diesel and soapnut oil (10%, 20%, 30% and 40%) fuel blends were used to conduct short-term engine performance and emission tests at varying loads in terms of 25% load increments from no load to full loads. Tests were carried out for engine operation and engine performance parameters such as fuel consumption, brake thermal efficiency, and exhaust emissions (smoke, CO, UBHC, NO_x, and O₂) were recorded. Among the blends SNO 10 has shown a better performance with respect to BTE and BSEC. All blends have shown higher HC emissions after about 75% load. SNO 10 and SNO 20 showed lower CO emissions at full load. NO_x emission for all blends was lower and SNO 40 blend achieved a 35% reduction in NO_x emission. SNO 10% has an overall better performance with regards to both engine performance and emission characteristics.     

Tar removal from the producer gas of a small scale downdraft gasifier using a fatty acid based,wet packed-bed scrubber

Small scale gasification combined heat and power (CHP) systems offer an alternative to diesel fuelled generators for power generation in remote communities and industrial sites. Tar and particulates in the producer-gas can damage the internal combustion engine generator and increase operation and maintenance costs. In this work, we present a novel trickle-bed scrubber using filtered waste cooking oil as a cost effective and easy-to-operate gas clean-up method for a small CHP system. The performance of the trickle-bed scrubber was compared against a packed-bed filter utilizing woodchips in a 20 kW_th downdraft gasifier. Used-cooking oil was selected as the solvent and woodchips as the bed-material as these are readily available, inexpensive, and can be recycled in the gasifier as fuel. A woodchip packed-bed filter reduced the tar and particulate matter (PM) in the producer gas from gasification of spruce chips (11% moisture) from 1.6 to 1.4 g/Nm³ and from 0.16 to 0.087 g/Nm³ respectively. The trickle-bed scrubber was able to reduce the tar and PM in the producer gas from gasification of pinewood (8% moisture) from 1.38 to 0.28 g/Nm³, and 0.209 to 0.082 g/Nm³, respectively. Tar and PM removal efficiency improved by 60% and 29% respectively. Components such as benzene, toluene, naphthalene, and biphenylene were the major tar components. After passing the trickle-bed, most tar was removed, with a preference for removal of multi-ringed aromatics and gravimetric tars. Parameters such as the tar and particulate concentration, feedstock moisture content, and feedstock source affect the performance of the gas clean-up system.     

Effect of engine parameters and gaseous fuel type on the cyclic variability of dual fuel engines

This paper presents an analysis of the cycle-to-cycle combustion variation as reflected in the combustion pressure data of a single cylinder, naturally aspirated, four stroke, Ricardo E6 engine converted to run as dual fuel engine on diesel and gaseous fuel of LPG or methane. A measuring set-up consisting of a piezo-electric pressure transducer with charge amplifier and fast data acquisition card installed on an IBM microcomputer was used to gather the data of up to 1200 consecutive combustion cycles of the cylinder under various combination of engine operating and design parameters. These parameters included type of gaseous fuel, engine load, compression ratio, pilot fuel injection timing, pilot fuel mass, and engine speed. The data for each operating conditions were analyzed for the maximum pressure, the maximum rate of pressure rise—representing the combustion noise, and indicated mean effective pressure. The cycle-to-cycle variation is expressed as the mean value, standard deviation, and coefficient of variation of these three parameters. It was found that the type of gaseous fuel and engine operating and design parameters affected the combustion noise and its cyclic variation and these effects have been presented.     

Performance and combustion characteristics of a DI diesel engine fueled with waste palm oil and canola oil methyl esters

This study discusses the performance and combustion characteristics of a direct injection (DI) diesel engine fueled with biodiesels such as waste (frying) palm oil methyl ester (WPOME) and canola oil methyl ester (COME). In order to determine the performance and combustion characteristics, the experiments were conducted at the constant engine speed mode (1500 rpm) under the full load condition of the engine. The results indicated that when the test engine was fueled with WPOME or COME, the engine performance slightly weakened; the combustion characteristics slightly changed when compared to petroleum based diesel fuel (PBDF). The biodiesels caused reductions in carbon monoxide (CO), unburned hydrocarbon (HC) emissions and smoke opacity, but they caused to increases in nitrogen oxides (NO_x) emissions.     

Experimental investigation of port injection of acetylene in DI diesel engine in dual fuel mode

As the world finds itself in the midst of universal energy shortage, compounded by a parallel need to reduce pollutants of all kinds; we must take serious look at novel sources of abundant energy and methodology of its use. Acetylene with its remarkable combustion properties appear to be proving itself as the best fuel for future internal engines if it is utilised properly. Because of inherent difficulties in handling acetylene, technology has emphasized the utilization of acetylene by injection techniques to combat back fire in internal combustion engines. An experimental investigation was carried out on a single cylinder, air cooled, DI diesel engine designed to develop 4.4 kW at 1500 rpm. Acetylene was injected into the intake port as a secondary fuel and diesel was injected directly into the cylinder. The optimized injection time of 5° aTDC and injection duration of 90 °CA (9.9 ms) was arrived. The gas flow rate was fixed at 110 g/h, 180 g/h and 240 g/h. The combustion, performance and emission parameters were studied for the above flow rates by varying the load from low load to full load. Results show that NO_x, HC and CO emissions reduced when compared to diesel operation due to leaner operation. A marginal increase in smoke emission was observed and brake thermal efficiency was nearer to diesel operation. On the whole it is concluded that without loss in thermal efficiency, safe operation of acetylene is possible in timed port injection technique. Reduced NO_x, HC and CO emission levels, with marginal increase in smoke emission level were achieved.     

Experimental evaluation of DI diesel engine operating with diestrol at varying injection pressure and injection timing

The use of biodiesel as an alternative in a diesel engine for extended period causes several engine operating problems such as injector coking, piston ring sticking, unfavorable pumping and spray characteristics due to the high viscosity of biodiesel compared to conventional diesel. In this study, a blend of 30% waste cooking palm oil (WCO) methyl ester, 60% diesel and 10% ethanol was selected based on stability test conducted and named as diestrol. The effect of diestrol fuel on the performance, emission and combustion characteristics of a direct injection diesel engine at varying injection pressure and timing was studied through experimental investigation. Maximum brake thermal efficiency of 31.3% was obtained at an injection pressure of 240 bar and injection timing of 25.5° bTDC. Compared to diesel, diestrol fuel showed reduction in carbon monoxide (CO), carbon dioxide (CO₂) and smoke emission by 33%, 6.3% and 27.3% respectively. Diestrol fuel decreased nitric oxide (NO) emission by 4.3%, while slight increase in the levels of unburnt hydrocarbon (UHC) was observed. Diestrol fuel exhibited higher cylinder gas pressure and heat release rate compared to diesel. Minimum ignition delay of 12.7° CA was observed with diestrol fuel which was similar to diesel at same operating condition.