Papers by JM Mallikarjuna
This paper deals with the experimental investigations of the in-cylinder tumble flows in an unfir... more This paper deals with the experimental investigations of the in-cylinder tumble flows in an unfired internal combustion engine with a flat piston at the engine speeds ranging from 400 to 1000 rev/min., and also with the dome and dome-cavity pistons at an engine speed of 1000 rev/min., using particle image velocimetry. From the two-dimensional in-cylinder flow measurements, tumble flow analysis is carried out in the combustion space on a vertical plane passing through cylinder axis. To analyze the tumble flows, ensemble average velocity vectors are used and to characterize it, tumble ratio is estimated. From the results, generally, we have found that tumble ratio varies mainly with crank angle position. Also, at the end of compression stroke, average turbulent kinetic energy is more at higher engine speeds. We have also found that, at 330 crank angle position, flat piston shows an improvement of about 85 and 23% in tumble ratio, and about 24 and 2.5% in average turbulent kinetic ener...
This paper deals with the experimental investigations carried out on a single-cylinder, four-stro... more This paper deals with the experimental investigations carried out on a single-cylinder, four-stroke, manifold injected spark ignition engine to improve the part-load performance and emission characteristics by modulating the inlet valve closure timing (IVCT) and clearance volume (CV). The IVCT is delayed in order to reduce the volumetric efficiency of the engine with full throttle operation which in turn reduces the brake power output so that engine can be operated at part-load. In addition, the CV is also reduced with respect to IVCT to maintain the effective compression ratio (ECR) of the engine. These things change the geometric expansion ratio (GER) and ECR of the engine along with reduced pumping losses to increase the brake thermal efficiency and reduce the exhaust emissions at part-loads. In order to vary the part-load brake power output, a suitable combination of the IVCT and CV is used which in turn vary the GER/ECR ratio of the engine. In this study, experiments are carrie...
Throttle body assembly plays a vital role in metering the airflow. It mainly consists of a butter... more Throttle body assembly plays a vital role in metering the airflow. It mainly consists of a butterfly valve to vary the flow area to control air flow rate through it. There is hardy any established procedure to design a throttle body assembly based on the engine specifications. In order to bridge the gap, this study, design and optimization of a throttle body assembly for a single-cylinder engine used in two-wheeler application has been analyzed along with the investigation of critical flow through various sub systems using computational fluid dynamics (CFD). To start with, the throttle bore and bypass passage diameters are calculated from the basic flow equations. Using CFD, best possible throttle shaft profile is arrived at, which will enhance airflow to the engine. The airflow rate for different throttle openings is predicted taking into account the distribution of main and bypass flow. It is observed that the airflow through main and the bypass passage are almost same around 12% ...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2021
Currently, engine downsizing through turbocharging is widespread in the automotive industry to im... more Currently, engine downsizing through turbocharging is widespread in the automotive industry to improve fuel economy and emissions. The engine downsizing demands compact and high performance centrifugal compressors for turbochargers. A compressor contains mainly an impeller and housing, which often uses a vaneless diffuser and an overhanging volute. High-speed flow from the impeller is decelerated in the diffuser and volute, to recover static pressure for boosting the engine. The volute flow characteristics and pressure recovery depend on the housing size, which determines the overall compressor performance and size. This study evaluates the effect of four different housing sizes viz., baseline, 12% scaled up, and 12% and 20% scaled-down geometrically, through experimental and numerical analysis. The experiments are conducted using different housing sizes with a given impeller to measure the compressor pressure ratio and efficiency. Also, steady-state numerical simulations are perfor...
International Journal of Engine Research, 2019
In-cylinder water injection is a promising approach for reducing NOx and soot emissions from inte... more In-cylinder water injection is a promising approach for reducing NOx and soot emissions from internal combustion engines. It allows one to use a higher compression ratio by reducing engine knock; hence, higher fuel economy and power output can be achieved. However, water injection can also affect engine combustion and emission characteristics if water injection and injector parameters are not properly set. Majority of the previous studies on the water injection are done through experiments. Therefore, subtle aspects of water injection such as in-cylinder interaction of water sprays, spatial distribution of water vapor, and effect on flame propagation are not clearly understood and rarely reported in literature due to experimental limitations. Thus, in the present article, a computational fluid dynamics investigation is carried out to analyze the effects of direct water injection under various injector configurations on water evaporation, combustion, performance, and emission charact...
Archives of Computational Methods in Engineering, 2018
This paper presents an objective classification of mixture distribution in the combustion chamber... more This paper presents an objective classification of mixture distribution in the combustion chamber of a gasoline direct injection (GDI) engine into homogeneous and non-homogeneous types. The non-homogeneous mixture distribution is further classified as properly stratified, improperly stratified and mal-distributed types. Based on this classification, four types of properly stratified mixture distributions viz., random, linear, Gaussian and parabolic are virtually simulated in the combustion chamber of a GDI engine using computational fluid dynamics to identify the mixture that results in maximum indicated mean effective pressure (IMEP). It is found that the IMEP is highest for the parabolic mixture distribution which is followed by Gaussian, linear and random types. The performance and emission characteristics of the virtual mixture distributions are compared with a late fuel injection case at different over all equivalence ratios ranging from 0.3 to 0.7. Then the variation of mixture equivalence ratio with the distance from the spark plug is parametrized for different virtual mixture distribution cases and expressed using a parameter called the ''stratification index''. It is found that the stratification index based on Gaussian variation gives maximum information about the mixture distribution in the combustion chamber. Finally the stratification index of different virtual mixture distributions is compared with the late fuel injection case at various overall equivalence ratios. It is found that the late fuel injection case tends to produce highest IMEP when the stratification index is close to unity. Abbreviations BDC Bottom dead center CAD Crank angle degree CFD Computational fluid dynamics CFL Courant Fredrich and Lewis DISI Direct injection spark ignition ER Equivalence ratio
SAE Technical Paper Series, 2018
SAE Technical Paper Series, 2018
SAE Technical Paper Series, 2017
Experimental Thermal and Fluid Science, 2016
Homogeneous charge compression ignition (HCCI) engines have the potential to operate with low nit... more Homogeneous charge compression ignition (HCCI) engines have the potential to operate with low nitric oxide (NOx) and soot emissions. Diesel HCCI engines pose challenges related to too early combustion, high combustion rates and wall wetting of the fuel. Injecting diesel in pulses has been shown to improve combustion in these engines. In this work, diesel injected in five timed pulses has been investigated in a compression ignition (CI) engine operating in HCCI mode. The influence of varying the first, middle and last injection pulse durations alone, in sequence, while maintaining all the other injection pulse durations equal has been studied. In addition, the influence of the injection timing of the last injection pulse was also studied. A comparison of the results has been made with HCCI operation using diesel injection in a single pulse at an injection timing of 100° CA before top dead centre (TDC) and also with the conventional compression ignition mode of operation under similar outputs. The results show that, multiple pulse (MP) injection is better than injecting the fuel in a single pulse (SP) as it leads to lower emissions and higher thermal efficiency. This is because of better combustion phasing and higher heat release rates.
SAE International Journal of Commercial Vehicles, 2017
SAE Technical Paper Series, 2017
Robotics and Biomimetics, 2016
Two-dimensional velocity fields around a freely swimming freshwater black shark fish in longitudi... more Two-dimensional velocity fields around a freely swimming freshwater black shark fish in longitudinal (XZ) plane and transverse (YZ) plane are measured using digital particle image velocimetry (DPIV). By transferring momentum to the fluid, fishes generate thrust. Thrust is generated not only by its caudal fin, but also using pectoral and anal fins, the contribution of which depends on the fish's morphology and swimming movements. These fins also act as roll and pitch stabilizers for the swimming fish. In this paper, studies are performed on the flow induced by fins of freely swimming undulatory carangiform swimming fish (freshwater black shark, L = 26 cm) by an experimental hydrodynamic approach based on quantitative flow visualization technique. We used 2D PIV to visualize water flow pattern in the wake of the caudal, pectoral and anal fins of swimming fish at a speed of 0.5-1.5 times of body length per second. The kinematic analysis and pressure distribution of carangiform fish are presented here. The fish body and fin undulations create circular flow patterns (vortices) that travel along with the body waves and change the flow around its tail to increase the swimming efficiency. The wake of different fins of the swimming fish consists of two counterrotating vortices about the mean path of fish motion. These wakes resemble like reverse von Karman vortex street which is nothing but a thrust-producing wake. The velocity vectors around a C-start (a straight swimming fish bends into C-shape) maneuvering fish are also discussed in this paper. Studying flows around flapping fins will contribute to design of bioinspired propulsors for marine vehicles.
ASME/IEEE 2007 Joint Rail Conference and Internal Combustion Engine Division Spring Technical Conference, 2007
This paper describes a numerical study on fuel-air mixing and combustion in a direct injection st... more This paper describes a numerical study on fuel-air mixing and combustion in a direct injection stratified charge spark ignition engine. The in-cylinder flow, fuel-air mixing and combustion characteristics are investigated in a single cylinder, four-valve, four stoke, direct injection SI engine with pent-roof head and reverse tumble ports. The engine combustion chamber had the side mounted injector and spark plug at the center of pent-roof. Wall guided fuel-air mixing scheme has been adopted. The pre processor code Es-ice, used for dynamic grid generation preparation including description of piston and valve motion. Commercial computational fluid dynamics code Star-CD is used for solving governing equations and post processing of results. Combustion in the present study is simulated using Extended Coherent Flame Model-3z (ECFM-3Z). This model is based on a flame surface density transport equation that can describe inhomogeneous turbulent premixed combustion. In the present study, eng...
SAE Technical Paper Series, 2015
SAE Technical Paper Series, 2015
2014 IEEE/OES Autonomous Underwater Vehicles (AUV), 2014
Deep sea aquatic animal propulsors are classified into four main categories lift-based propulsion... more Deep sea aquatic animal propulsors are classified into four main categories lift-based propulsion, drag-based propulsion, undualtion mode and jet propulsion. In order to develop combined flapping and undulation mode propulsion for ships and underwater vehicles a brief introduction is given to lift-based propulsors and undulation mode. Combined bio-mimetic flapping and undulation mode propulsion systems for underwater vehicles have advantages such as ecologically pure, relatively low operational frequency and higher efficiency. This system can combine the function of propulsor, control device and stabilizer, provides static thrust, high maneuverability, less conspicuous wake and less cavitation problem than conventional propellers. In this paper, we experimentally study the application of a lift-based fore flipper locomotion applied to a 3m ship model, the concept of which resembles to the propulsion of penguins and turtles and present the results and observations. An electro-mechanical drive and transmission system is designed to actuate a pair of oscillating foils fitted at the bottom of the ship model. The model performances, both resistance and propulsion aspects, were studied. Sharks exhibit high-performance aquatic locomotion through oscillation of its homocercal forked caudal fin. This paper also presents the PIV measurements carried out on a live shark fish to understand and analyze the hydrodynamic behavior of its propulsion using the caudal fin. The velocity vector plots shows that the fins and caudal fins produce reverse von Karman vortex street resulting in a aftward jet formation which gives it the propulsive force.
SAE Technical Paper Series, 2008
Heat Transfer, Volume 3, 2006
ABSTRACT This paper describes the numerical simulation of the flow and heat transfer around a ven... more ABSTRACT This paper describes the numerical simulation of the flow and heat transfer around a ventilated brake disc. The aim of this investigation is to provide more insight on ventilated brake disc flow phenomena with a view to improve heat dissipation. Analysis of brake disc has been carried out using FLUENT (CFD code based on the Finite Volume Method). Numerical predictions of the flow and heat transfer are compared with available experimental data in the literature [2]. In the present work validation of numerical results are discussed in two parts. In the first part, the optimum grid was found from the grid independence test and in the second part the effect of turbulence models on flow field development was studied. Three rotors have been considered with each of 36, 40 and 45 number of vanes. Each rotor of two flow passages has been considered for the analysis. An isothermal analysis has been carried out to analyse the heat transfer. From the grid independence test it was found that the grid with 300,000 cells is seems to be the appropriate. SST k-ω turbulence model was able to predict the flow field with an accuracy of 3% and 1% in predicting tangential velocity and radial velocity respectively. From the isothermal rotor analysis it is found that the geometry having 45 vanes dissipates 7.7% and 5% more heat compared to geometries having number of vanes 36 and 40 respectively.
Advanced Materials Research, 2012
The main objective of the present investigation is to make a computational study of flow structur... more The main objective of the present investigation is to make a computational study of flow structure inside the engine cylinder in a DI diesel engine during the end of compression stroke at an engine speed of 1000 rev/min. The analysis has been carried out for four different piston configurations viz., flat piston, centre bowl on flat piston, inclined and inclined offset bowl piston. A polyhedral trimmed cell has been adopted for meshing the geometries using the code called STAR-CD Es-ice. The flow has been simulated by solving the governing equations of conservation of mass, momentum and energy using the SIMPLE algorithm. From this numerical prediction, the best possible combustion chamber configuration and the location of fuel injector on the cylinder head have been arrived.
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Papers by JM Mallikarjuna