Department of Mechanical engineering

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Author: search.filters.author.Verma, SaketSubject: search.filters.subject.Biogas

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Now showing 1 - 9 of 9
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    An experimental study on gas-to-liquids and biogas dual fuel operation of a diesel engine
    (Inder Science, 2021-10) Verma, Saket
    In the present configuration, GTL replaces diesel, and biogas is used as gaseous fuel in the dual fuel (DF) operations. The effects of this substitution have been evaluated from the perspectives of second-law of thermodynamics. The results are compared with the diesel single-fuel, GTL single-fuel and GTL-biogas DF operations. Also, engine out emissions have been compared to understand the environmental impact of these fuel combinations. The results show that DF operation offers up to 80% pilot liquid fuel replacement by biogas, however, some reductions in energy and exergy efficiencies are observed.
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    Advances in the Utilization of Biogas in Diesel Engines: An Exergy Based Approach
    (Springer, 2022-01) Verma, Saket
    In order to reduce the use of fossil fuels in the transportation sector, various alternatives have been explored in the past. Biogas is an interesting candidate in this context with its large potential in countries like India, which can be utilized for vehicular as well as decentralized power generation applications. Biogas is a renewable fuel that is produced from organic waste materials through anaerobic digestion process. The produced raw biogas contains methane as the fuel; however, carbon dioxide is also present in considerable amount. This inert gas reduces the flame speed and heating value of biogas and eventually deteriorates engine performances. The auto-ignition temperature of biogas is high enough that it cannot be directly utilized in the diesel engines. One of the easiest and flexible ways to utilize biogas in diesel engines is through ‘Dual Fuel (DF)’ technique. In this technique biogas is used as the main gaseous fuel and another liquid fuel (commonly diesel) is used as the pilot fuel. In this way, existing diesel engines can use biogas as the fuel with minimum engine modifications. Nevertheless, the performance of biogas DF engine has been found to be much poor than the standard diesel engine, especially at the low loads. It has been shown that there are many engine parameters, e.g. engine load, type and quantity of biogas, injection timing of the pilot fuel etc., which can affect the performance and emission characteristics of a DF engine. This article presents an overview of these effects on a biogas operated DF engine and suggests various techniques to enhance the performance of the engine.
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    An Experimental Comparison of Enriched Biogas and CNG on Dual Fuel Operation of a Diesel Engine
    (IOP, 2019) Verma, Saket
    In the present work CNG and enriched biogas (93% CH4 by vol.) have been experimentally compared for performance and emission characteristics in a dual fuel diesel engine. The diesel is used as the pilot fuel, which is directly injected into the engine cylinder. The CNG and biogas are used as the main fuels, which are inducted with the intake air in the intake manifold. The experimental observations are taken for steady state conditions at varying engine loads for maximum pilot fuel substitution conditions. The performance of the engine is evaluated based on energy and exergy analyses. The emission characteristics are shown for oxides of nitrogen (NOx), hydrocarbon (HC), carbon monoxide (CO) and smoke emissions. It was found that enriched biogas showed the performance similar to that with CNG, whereas slight variations in the emissions were observed. The exergy efficiencies of 27.8% and 26.9% were calculated for CNG and biogas dual fuel operations respectively at the full load. Similarly, maximum pilot fuel substitutions were found 73.4% and 71.4% for the above conditions respectively
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    An experimental investigation of biodiesel-biogas dual-fuel engine based on energy and exergy analysis
    (Inder Science, 2018-06) Verma, Saket
    In the present work, exergy analysis has been performed on the biodiesel-biogas dual fuel (DF) engine. The DF operation has been studied with biodiesel (Jatropha curcas) as the pilot fuel to ignite the main fuel (biogas). The experiments were performed at a constant engine speed of 1500 rpm with varying engine loads and optimised injection timings for both diesel and DF modes. The results indicate that DF operation at low load produces poor performance and emission characteristics, however, no significant variations were observed between diesel-DF and biodiesel-DF operations. At 23% of engine load, exergy efficiencies were found to be 8.53% and 8.4% for diesel-DF and biodiesel-DF operations respectively; compared to 12.57% for pure diesel operation. Nevertheless, at higher loads, exergetic performances of DF operations were significantly improved. Furthermore, oxides of nitrogen (NOx) emissions from DF operations were significantly reduced compared to that with diesel operation.
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    Effect of Hydrogen Enrichment Strategy on Performance and Emission Features of Biodiesel-Biogas Dual Fuel Engine Using Simulation and Experimental Analyses
    (ASME, 2020-12) Verma, Saket
    In the present work, hydrogen enrichment in biogas is studied as a potential approach to improve the performance and emission features of a biodiesel-biogas dual fuel engine. A single-cylinder diesel engine is modified to operate in dual fuel mode using Jatropha curcas biodiesel as the pilot fuel and biogas as the main fuel. An electronic control unit is developed in-house to study 5−20% hydrogen enrichment in biogas using the timed manifold injection (TMI) technique. A three-dimensional computational fluid dynamics-based simulation methodology is presented for optimal selection of TMI parameters to ensure efficient and safe operation of the engine. Subsequently, the optimized injection conditions are used for the experimental evaluations, which are performed for performance and emission characteristics of the engine at low and high engine loads. Engine performance is analyzed based on energy and exergy analyses, whereas hydrocarbon (HC), carbon monoxide (CO), oxides of nitrogen (NOx), and smoke emissions are analyzed for emission characterization. The simulation results show that the injection angle and injection pressure influence in-cylinder mixture formation and hydrogen accumulation in the intake manifold. A combination of injection angle = 60 deg and injection pressure = 150 kPa offers good mixture formation. Experimental results show that at 20% hydrogen enrichment, exergy efficiencies of the dual fuel engine are increased from 8.4% to 10.1% at low load and 23.3% to 25.5% at high load. However, maximum reductions in HC and CO emissions of 35.6% and 50.0%, respectively, are calculated at low load
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    An experimental investigation of exergetic performance and emission characteristics of hydrogen supplemented biogas-diesel dual fuel engi
    (Elsevier, 2018-01) Verma, Saket
    An experimental investigation of a conventional diesel engine with diesel, biogas and hydrogen as fuels has been carried out, while the engine is modified to operate in dual fuel mode using diesel as the pilot fuel and biogas as the main fuel respectively. In order to improve the biogas-diesel dual fuel engine performance and emission characteristics, small percentages of hydrogen supplementations, viz. 5%, 10%, 15% and 20%, in biogas were studied and the comparison was also made to that with the neat biogas-diesel dual fuel operation. Engine performance characterization has been done with exergy based approach, and major sources of irreversibilities in various engine processes are also investigated and compared for the above mentioned cases. The results show that hydrogen supplementations in biogas have lesser effect on the combustion characteristics at low load, while, at high load, the combustion patterns change significantly with higher heat release rates and peak combustion pressures. Furthermore, performance and emission characteristics are found nearly unaffected with 5% of hydrogen addition both at low and high loads. Nevertheless, further addition of hydrogen in biogas causes improvements in performance and emission characteristics of the dual fuel engine
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    The effects of compression ratio and EGR on the performance and emission characteristics of diesel-biogas dual fuel engine
    (Elsevier, 2019-03) Verma, Saket
    In this study, an experimental investigation on diesel-biogas dual fuel (DF) engine is presented based on energy and exergy analyses. The effects of change in compression ratio (CR), exhaust gas recirculation (EGR) and EGR temperature on the performance and emission characteristics of DF engine have been studied. In the first stage, engine was studied with increasing CRs of 16.5, 17.5, 18.5 and 19.5 in stepwise manner. It was found that the higher CRs were not only advantageous to the engine performance from first and second-law point of view but also to the exhaust emissions. In the second stage, DF engine was studied at the highest CR (19.5) and the effects of EGR were analysed. The engine was studied with EGR percentages of 5%, 10% and 15%, which caused slight improvements in engine efficiency at low load and simultaneous decrease in oxides of nitrogen (NOx) emissions. However, high EGR percentages at high loads showed slight decrease in engine efficiency. In the third stage, hot EGR was employed and the results obtained were compared with the cold EGR case. The results showed that the highest efficiencies both at low and high loads were obtained with hot EGR cases and at the same time exhaust emissions could also be kept in check.
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    A comparative exergetic performance and emission analysis of pilot diesel dual-fuel engine with biogas, CNG and hydrogen as main fuels
    (Elsevier, 2017-11) Verma, Saket
    In this experimental study coupled with exergy analysis, a small compression ignition engine is modified to operate in dual fuel (DF) mode with biogas, CNG and hydrogen as main fuels, and diesel as pilot fuel. Injection timing (IT) advance is studied as a strategy to improve the low load performance and emission characteristics of DF engine. Experiments were performed at ITs of 20, 23, 26, 29 and 32 degree crank angles before top dead center (°BTDC) for two engine loading conditions of low and full loads at the operating points corresponding to maximum diesel substitutions. It was found that maximum diesel substitution was considerably affected by the type of main fuel and engine load, however, relatively less affected by IT advance. Highest maximum diesel substitution was observed with CNG, and lowest with hydrogen as main fuels in DF mode. It was also found that IT that gave highest performance or lowest emission varied with both the type of gaseous main fuels and engine loads. At low load, ITs of 32, 29 and 26 °BTDC showed highest exergy efficiencies of 8.5%, 11.1% and 11.9% for biogas, CNG and hydrogen DF operations respectively, compared to 12.6% for diesel only operation. At these operating conditions, exergy destructions of 73.67%, 64.86% and 60.96% (% of total input exergy) were found for DF operations compared to 62.98% for diesel only operation. At full load condition, hydrogen DF operation exceeded exergy efficiency by 2% compared to that with the diesel only operation. On the emissions side, HC, CO and smoke emissions were found to be reduced with advanced ITs; however, NOx emissions were significantly increased.
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    Effects of varying composition of biogas on performance and emission characteristics of compression ignition engine using exergy analysis
    (Elsevier, 2017-04) Verma, Saket
    Growing energy demands and environmental degradation with uncontrolled exploitation of fossil fuels have compelled the world to look for the alternatives. In this context, biogas is a promising candidate, which can easily be utilized in IC engines for vehicular as well as decentralized power generation applications. Primary constituents of raw biogas are methane (CH4) that defines its heating value, and carbon dioxide (CO2) that acts like a diluent. This dilution effect reduces the flame speed and heating value of biogas, eventually deteriorating the engine performances. Present article focuses on experimental evaluation and quantification of these variations of the engine performance. Three compositions of biogas: BG93, BG84 and BG75 (containing 93%, 84% and 75% of CH4 by volume respectively) were studied on a small CI engine in dual fuel mode. Moreover, to evaluate individual process inefficiencies, exergy analysis based on second-law of thermodynamics is implemented. Exergy balances for different compositions of biogas are presented. Biogas dual fuel operation showed 80–90% diesel substitution at lower engine loads. At higher loads, total irreversibility of the engine was increased from 59.56% for diesel operation to 61.44%, 64.18% and 64.64% for BG93, BG84 and BG75 biogas compositions respectively. Furthermore, combustion irreversibility was found to be decreasing with higher CO2 concentrations in biogas. BG93 showed comparable results to that of diesel operation with 26.9% and 27.4% second-law efficiencies respectively.