A Numerical Model To Predict The Performance Of A Ci Engine Enriched By Hydrogen Fuel And Flow Visualization In The Intake Manifold For Hydrogen Injection Using CFD

Abstract

The rapid depletion of fossil fuels has called for the use of alternative fuels in the field of IC engines and combustion. Therefore it is high time to switch over to new design of automobiles with lesser emissions run by alternative gaseous fuels like LPG, CNG, and Hydrogen etc. From the literature survey it is observed that extensive research has been carried out on thermodynamic modeling of diesel engine. The present investigation includes two stages. One is numerical modeling of diesel engine enriched by hydrogen fuel and later, using CFD analysis, the investigation carried on so as to predicting  the position of hydrogen gas injector and injection angle for manifold injection of dual fuel diesel engine.

In the first stage, thermodynamic analysis was done using double weibe heat release equation during the combustion period. A MATLAB code has been written for the thermodynamic model, which takes input as engine parameters, fuel data and gives the Pressure-Crank angle, Temperature-Crank angle and Rate of heat release-Crank angle plots. These plots were used to analyze the performance of engine. Further study has been done on effect of intake air temperature on ignition delay period, when the diesel engine enriched by hydrogen gas fuel.

Two cases were considered in the present model, one with diesel as fuel and other with diesel as primary fuel and hydrogen as secondary fuel on mass basis. The peak cylinder pressure of hydrogen enriched CI engine and diesel operated engine are found to be 91.7 bar and 87.1 bar at 1500 rpm respectively. The cylinder temperature of hydrogen enriched CI engine is found to be 1997 K and for diesel operated engine, it was found to be 1898 K at 1500 rpm. The rate of heat release of hydrogen enriched CI engine is found to be 88.2 J/ deg, compared with 86.9 J/ deg for the diesel engine at 1500 rpm. The maximum heat release occurs at nearer to the   TDC for hydrogen enriched engine, which improves the cycle efficiency.

For enriched diesel engine, for intake temperature of 30° C ignition delay is found to be 0.76 ms. while in the case of intake temperature of 40° C ignition delay is 0.7 ms. with shorter ignition delay, premixed combustion stage decreases due to which efficiency engine will increase.

The position of injector and injection angle plays a major role in mixture formation and effective flow of air-fuel mixture into the combustion chamber. CFD analysis using FLUENT 6.3.26 was done so as to find the optimum location of the injector. In this present study, two injector positions were taken into consideration. Injector angle was varied as 30°, 45° and 60° and whilst valve position was also varied as 4, 6, 8 and 10 mm for each injector position. The injector angle of 60°, 120 mm from cylinder head and valve lift of 4mm was found to be optimum location of injector position. Based on best performance and safety issue such as backfire problem.