Performance Test On A Multi-cylinder Diesel Engine Fitted 231ba

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A supercharger is an air compressor used for forced induction of an internal combustion engine. A phenomenon which increases the mass flow rate that provides more oxygen to combustion than a naturally aspirated engine, which allows more fuel to be provided and more work to be done per cycle, increasing the power output of the engine. A supercharger is any device that pressurizes the air intake to above atmospheric pressure. Power for the unit can come mechanically by a belt, gear, shaft, or chain connected to the engine's crankshaft. This effect on internal combustion engine acts as a boost which increases the power output of an engine by the increase of combustion levels.

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Turbochargers when used as a boosting agent in an internal combustion engine uses the exhaust gas as input energy to the system however turbocharger causes some amount of back pressure in the exhaust system and tends to provide less boost until the engine is running at higher RPMs. The time required to bring the turbo up to a speed where it can function effectively is called › . This is noticed as a hesitation in throttle response when coming off idle. This is symptomatic of the time taken for the exhaust system driving the turbine to come to high pressure and for the turbine rotor to overcome its rotational inertia and reach the speed necessary to supply boost pressure. A turbocharging unit needs a separate EGR(exhaust gas recirculation) to avoid a considerable NOx pollution caused due to high temperature conditions.

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A jet compressor has a primary converging and diverging portion which utilize the pressure energy to increase the kinetic energy. The high pressure input after ing through the convergentdivergent region produces a high velocity flow rate resulting a low pressure region. This low pressure region creates a vacuum and tends the atmospheric air to get injected into the compressor. A momentum transfer takes place between the high velocity exhaust and low velocity air molecules . A diff at the end of the compressor produces a high pressure output and a low velocity flow. Forced draught fans are provided to increase the velocity of air sent from the atmosphere.

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A forced draught system is provided say a blower is used in forcing the atmospheric air into the compressor. A blower which provides an air velocity of 25m/s will maintain the entrainment ratio. The entrainment ratio is defined as the amount of motive fluid required to entrain and compress a given amount of suction fluid. NATUAL DRAIGHT SYSTEM A natural draught system would reduce the entrainment ratio due to it¶s natural flow velocity of atmospheric air as in case the exhaust gas would have a higher velocity comparing to the atmospheric air.

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The major advantage of supercharging is an increased net output of the system with the exhaust gas coming out of the engine. This exhaust gas has the driving power to improvise the density of air molecules which is fed into the combustion cylinder. The EGR system is a self activated process in a supercharged diesel engine. The availability of oxygen molecules in atmospheric air can be controlled up to 50% of EGR. The increased temperature condition can cause NOx pollution which can be avoided due to EGR which absorbs heat not affecting the combustion level inside the chamber. The output pressure is minimised and so a silencer can be excluded.

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The exhaust gas from the engine with a mass flow rate of 0.035kg/s at 673K and 3 bar pressure is fed into a jet compressor. The jet compressor creates a vacuum(low pressure region) and tends atmospheric air to enter at 300K and 1 atm the jet compressor a momentum transfer takes place between the high velocity exhaust gas molecule and a low velocity air from a blower unit. This process produces a high pressure atmospheric air molecule after travelling the diff unit. For mass balance a divider is used to provide the same 0.035kg/s as an input to the combustion chamber. This pressurized air reduces the specific heat inside the combustion chamber by absorbing heat which avoids the NOx formation which happens under high temperature conditions. The output from the divider is sent into a pressure valve to surveillance as it¶s pressure should not exceed 1.5 bar. An air cooler is installed to reduce the high temperature. An air filter is fitted before the engine to prevent soot particles entering the engine.

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LOAD TEST

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TOTAL FUEL CONSUMPTION,SPECIFIC FUEL CONSUMPTION

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SPECIFIC POWER OUTPUT

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Simple in construction. As it doesn¶t involve in any moving parts the maintenance cost is minimal. Due to it¶s simpler construction process the cost of manufacturing is also cheap. The part of the exhaust gas is re-circulated into the engine and so a lower pressure gas is sent out which doesn¶t need a silencer and noise pollution can be minimised. EGR process is also carried along with the supercharging which reduces the pollution level especially the NOx pollution level.