An investigation on the diesel fuel spray injected into stagnant ambient air in a chamber is reported in this paper. The objective of the investigation was to analyze the processes of diffusion of mass and velocity of the fuel in the fuel spray. The distribution of velocity and mass of the fuel showed similarity in the zone of established flow. Gaussian normal probability distribution for free jet was assumed by earlier workers, starting with Albertson, et al., for analyzing such a situation. However, it has been found that diesel fuel spray in a chamber necessitates modification of the model described and a modified model has been proposed herein. The Abramovich model is also compared with the experimental data. The ratio of εm/εm0 varied from 1.24 to 1.45 for the change of injection pressure from 100 to 200 atm. It is conclusively shown that mass diffuses faster than the momentum, the rate of diffusion increasing with the increase in the injection pressure. The proposed model gives good agreement with experimental results. The various parameters of the equations for depicting the fuel spray as a jet have been evaluated and tabulated.
Jatropha oil, a non-edible vegetable oil shows a greater potential for replacing conventional diesel fuel quite effectively, as its properties are compatible to that of diesel fuel. But low volatility and high viscosity of jatropha oil call for hot combustion chamber, which is provided by a low heat rejection diesel engine with threaded air gap piston and liner with superni-90 inserts. The performance of the engine with jatropha oil is obtained with different versions of the engine such as conventional engine and insulated engine at normal and preheat condition of the oil, with varying injection pressure and timing and compared to the engine with pure diesel operation at recommended injection pressure and timing. Increase of thermal efficiency of 18% and reduction of NOx levels by 5% are observed at optimized injection timing and at higher injection pressure with insulated engine at preheat condition of jatropha oil in comparison with pure diesel operation on conventional engine.
This paper presents the results of numerical investigations of a turbulent, swirling and recirculating flow without combustion inside a reverse flow gas turbine combustor. In order to establish the characteristics of fuel distribution patterns of the fuel spray injected into swirling flows, flow fields are analyzed inside the swirl combustor for varying amount of swirl strength using a commercial CFD code fluent 6.1.22. Three Dimensional computations are performed to study the influence of the various parameters like injection pressure, flow Reynolds number and Swirl Strength on the fuel distribution patterns. The model predictions are compared against the experimental results, and its applicability over a wide range of flow conditions was investigated. It was observed from the CFD analysis, that the fuel decay along the axis is faster with low injection pressures compared to higher injection pressures. With higher Reynolds numbers the fuel patterns are spreading longer in the axial direction. The higher momentum of the air impedes the radial mixing and increases the constraint on the jet spread. The results reveal that an increase in swirl enhances the mixing rate of the fuel and air and causes recirculation to be more pronounced and to occur away form the fuel injector. The CFD predictions are compared with the experimental data from the phototransistor probe measurements, and good agreement has been achieved.
This paper reports an investigation carried out on the recirculation zones established in conical chambers with radial vaned inlet swirlers. The boundaries of the recirculation zones established in various conical chambers of different cone angles are presented for different inlet swirl numbers and an optimum cone angle which gives a reasonably short length of the recirculation zone with maximum pressure recovery is suggested. The inlet swirl number is also optimized for a fairly high swirl strength within the recirculation zone and the inlet swirl number for which the recirculation completely disappears is also estimated. In addition to this, an equation is curve-fit to the experimental data which correlates the length of the recirculation zone for any given cone angle and inlet swirl number.
Among the biomass resources, vegetable oils are observed to be good alternative fuels for use in diesel engines and are also attractive because of renewability. However, there are fundamental problems of engine performance and exhaust emissions due to high viscosity and low volatility of the pure vegetable oil. The present work aims at evaluating the performance of Jatropha methyl ester (JME) by evaluating the combustion properties and engine vibration & noise. This generates a corroborative method to ascertain the engine combustion quality, as the vibration trend developed by the engine is synonymous with the excitation generated by combustion..
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