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Showing papers by "Ujjwal K. Saha published in 2021"


Journal ArticleDOI
TL;DR: In this article, the effects of diethyl ether (DEE) as an additive on the performance, combustion and emission characteristics of the engine fuelled by the VO30 blend were investigated.
Abstract: In this study, Mesua ferrea Linn oil (VO, 30% by volume)-diesel (70% by volume) blend (VO30) is used as the fuel to power a direct-injection (DI), single-cylinder compression ignition (CI) diesel engine. This study is focused on the effects of diethyl ether (DEE) as an additive on the performance, combustion and emission characteristics of the engine fuelled by the VO30 blend. DEE is added to the VO30 blend to form two types of ternary blend. One consists of 5% DEE and 95% VO30 by volume (VO30DEE05) and the other consists of 10% DEE and 90% VO30 by volume (VO30DEE10). The study reveals an improvement of 1% to 2.3% in engine thermal efficiency with the use of diethyl ether as additives to the VO-diesel blend. In the same line, both the CO and NOx emission also decreases with the use of DEE additives with the VO-diesel blend. A maximum reduction of 6.9% to 13% CO emission and 3.2% to 11.9% NOx has been achieved with DEE additives as compared to VO30 fuel. The work suggests that DEE can be used effectively as an additive to VO30 fuel which can run CI diesel engines with improved thermal efficiency and reduced emissions.

11 citations


Journal ArticleDOI
TL;DR: In this paper, a compendium of different methods employed in estimating these exergy terms have been reviewed and classified under individual exery terms with necessary descriptions, which will not only provide plenty of information on exergy evaluation methods of IC engines but also allow future researchers to adopt the appropriate one.
Abstract: Exergy analysis of the reciprocating internal combustion (IC) engines is studied by estimating various input and output energy transfer parameters concerning a dead state reference. Exergy terms such as fuel input, work output, cooling, and exhaust gas are measured and are set into the exergy balance equation to determine the amount of loss or destruction. Exergy destructions are found in many forms such as combustion (entropy generation), cylinder wall, friction, mixing, blow-by, and others. These exergy terms have been estimated by considering various factors such as engine type, fuel type, environmental condition, and others. In this article, the different methods employed in estimating these exergy terms have been reviewed. It attempts to make a compendium of these evaluation methods and segregates them under individual exergy terms with necessary descriptions. The fuel input measurement is mostly based on Gibb's free energy and the lower heating value, whereas its higher heating value is used during the fuel exergy calculation on a molar basis. The work output of the engines is estimated either from the crankshaft or by analyzing the cylinder pressure and volume. The exergy transfer with cooling medium and exhaust gas depends on the temperature of the gas. The maximum achievable engine performance is quantified by estimating the exergy efficiency. This piece of study will not only provide plenty of information on exergy evaluation methods of IC engines but will also allow future researchers to adopt the appropriate one.

10 citations


Journal ArticleDOI
TL;DR: The article mainly focuses on the aerodynamic aspects of all the rocket nozzles developed till date and summarizes the major findings covering their design, development, utilization, benefits and limitations.
Abstract: The nozzle forms a large segment of the rocket engine structure, and as a whole, the performance of a rocket largely depends upon its aerodynamic design. The principal parameters in this context are the shape of the nozzle contour and the nozzle area expansion ratio. A careful shaping of the nozzle contour can lead to a high gain in its performance. As a consequence of intensive research, the design and the shape of rocket nozzles have undergone a series of development over the last several decades. The notable among them are conical, bell, plug, expansion-deflection and dual bell nozzles, besides the recently developed multi nozzle grid. However, to the best of authors’ knowledge, no article has reviewed the entire group of nozzles in a systematic and comprehensive manner. This paper aims to review and bring all such development in one single frame. The article mainly focuses on the aerodynamic aspects of all the rocket nozzles developed till date and summarizes the major findings covering their design, development, utilization, benefits and limitations. At the end, the future possibilities of development are also recommended.

5 citations


Journal ArticleDOI
TL;DR: In this article, the authors collected and analyzed the past research studies in the field of hybrid wind rotors and suggested an optimization route for the design of such a hybrid wind rotor to ensure that the design complexity is minimized, and at the same time, both the Savonius and the Darrieus rotors are utilized to their fullest potential.
Abstract: Over the last few decades, the vertical-axis wind turbines (VAWTs) have undergone intensive research mainly due to their design simplicity and independency of wind direction. The drag-based Savonius wind rotor exhibits a better starting capability, whereas the lift-based Darrieus wind rotor achieves higher efficiency over a wider operating range. Thus, in order to capitalize on their advantages, both the rotors are mounted on the same axis to form a hybrid/combined system. In this review paper, an attempt has been made to collect and analyze the past research studies in the field of hybrid wind rotors. An optimization route has also been suggested for the design of such a hybrid wind rotor to ensure that the design complexity is minimized, and at the same time, both the Savonius and the Darrieus rotors are utilized to their fullest potential. In this regard, a few important parameters are identified whose effects on the hybrid rotor performance must be investigated in future studies. Suggestions and direction of research are presented keeping in mind the improvement of the technology.

3 citations


Journal ArticleDOI
TL;DR: In this paper, two in-loop second-order notch filters have been used with an LPF to nullify the effect of dominant lower order harmonics and the dynamic performance of the proposed technique is improved by implementing a PID type loop filter.
Abstract: The increasing number of nonlinear loads and the integration of renewable energy sources into the grid make the conventional SRF-PLL less accurate for estimating the phase and frequency of the grid voltage. A variety of enhanced filtering-based PLLs have been reported in the literature to solve this issue. However, these techniques are computationally more complex. For this reason, a method has been proposed to improve the performance of low pass filter (LPF)-based SRF-PLL, which is easy to implement and is computationally less expensive. In this paper, two in-loop second-order notch filters have been used with an LPF to nullify the effect of dominant lower order harmonics. The dynamic performance of the proposed technique is improved by implementing a PID type loop filter. The proposed scheme is compared with the other methods, like MRF-PLL, conventional and LPF-based SRF-PLL. The response of the proposed PLL is found to be encouraging under different grid disturbances. The efficacy of the proposed PLL has been verified by implementing the current controller to control the active and reactive grid current for the grid side converter in the hardware setup.

2 citations


Journal ArticleDOI
TL;DR: The double-divergent nozzles (DDNs) have drawn immense interest as discussed by the authors, and they have been explored till now in a variety of applications, such as space flight, unmanned aerial vehicles (UAVs), etc.
Abstract: The efficiency of a rocket engine is dependent on altitude adaptability of its nozzle. In this context, double-divergent nozzles (DDNs) have drawn immense interest. The DDNs explored till now compr...

2 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the prospective of biogas as fuel in unmodified compression-ignition (CI) diesel engines under Biogas-diesel dual-fuel (DF) combustion mode.
Abstract: This experimental study investigates the prospective of biogas as fuel in unmodified compression-ignition (CI) diesel engines under biogas-diesel dual-fuel (DF) combustion mode. The premixed air-biogas mixture has been ignited by using diesel as pilot-fuel. The DF mode engine parameters have been investigated with varying the engine load by adjusting the biogas and diesel flow with the individual control mechanism. For the entire tested loads, about 65–69% of diesel mass consumption of the engine has been substituted by biogas under the DF mode. The DF mode consumes lesser friction power than that of the diesel mode. NOx levels have been decreased for the entire loads with biogas fuelled DF mode. The DF mode produced higher CO, HC and CO2 levels to the diesel mode. But, in actual, the $${\text{NO}}_{x} + {\text{HC}}$$ emissions are found within the limit of emission norms, and the amount of CO and CO2 emissions is found much lower when compared to the large volume of CO2 existence in biogas composition. The maximum thermal efficiency of the engine has been observed about 18.66% lower with the biogas-diesel method to diesel way which can be upgraded through advancing the fuel injection timing. This study confirms that it is feasible to use biogas safely being a renewable gaseous fuel in a CI diesel engine with DF mode without operating parameter alterations beyond medium loads. The engine can run for entire loads under DF mode with the achievement of equivalent diesel efficiency, the operating parameters should be adjusted as per the suggestions of this study.

Journal ArticleDOI
TL;DR: In this article, the authors explored the effect of this transformation on the wake characteristics of a square body with l/d = 1 to a triangular body with L 1, where l is the length of lateral and front surface, and d is the body height.
Abstract: In the present study, two-dimensional unsteady, incompressible flow around a square body that is being transformed into a vertex oriented towards the flow configuration of a triangular body is numerically investigated at Re =100 using ANSYS FLUENT 19.0 software. The purpose is to explore the effect of this transformation on the wake characteristics of a square body with l/d = 1 to a triangular body with l/d = 0; where l is the length of lateral and front surface, and d is the body height. The effect on the flow behavior caused by the leading-edge transformation from the prospect of wake width, recirculation length and stagnation pressure difference is discussed. It is seen that as the l/d ratio decreases, the vortex strength increases which is attributed to the higher stagnation pressure difference value resulting in more intense rolling of the shedding vortex and a smaller wake width. For lower l/d, the fluid traverses a longer distance along the lateral surfaces resulting in greater loss of momentum and hence the lower vortex formation length. The mean drag coefficient is found to be minimum for l/d = 0.75 with stagnation pressure difference and recirculation length being the more dominating factor on this variation. The flow in all the cases separates at the rear surface and the general trend of decrease in drag coefficient with decrease in wake width is not followed. However, such modification leads to better aerodynamic outcome by weakening the periodic drag and lift forces.