RETARDATION TESTAIMTo conduct a retardation test on single cylinder vertical diesel engine (FIELD MARSHAL) and to find the frictional power loss at the given speed.SPECIFICATION

Apparatus reqd: Engine test rig, tachometer, stopwatch etc

THEORY:

The engine is loaded with the help of brake drum dynamometer. Retardation test is conducted to find out the power loss due to friction in an IC engine. The time to retard the engine from an initial to final speed is noted at no load as well as on loaded condition. The torque on the engine at no load and at specific loads within the maximum load is calculated. The torque on engine at no load will be solely due to friction which can be calculated and the power loss due to friction is calculated.

If represents frictional torque at no load

Where

And

Where=time required to retard from an angular velocity to at no load condition.If represents the frictional torque with load, then

Where =time required to retard from an angular velocity 1 to 2 at on load condition.

Power loss due to friction

Where =average speed in rpm

Precautions1. Check the diesel level in the fuel tank and make sure that there is in enough fuel.2. Apply lubricating oil where ever necessary.3. Make sure that the control valve of the fuel supply in fully opened.4. Make sure that the engine is in no load condition.5. Fuel cut off liver should not be in the cut off position.

ProcedureCalculate the maximum load that can be applied on the engine. Engage the decompression lever and crank the flywheel manually. After getting sufficient speed of the flywheel disengage the decompression lever. At no load condition, the engine speed is adjusted to the desired speed 650 rpm (N1) by adjusting the governor. Now cut off the fuel supply. Not down the time taken (t1) to retard the engine from N1 to N2 (say 550 rpm) under no load condition with the help of a stop watch. By fixing N1 constant and varying N2 take down various values for t1. For conducting experiment under loaded condition same procedure is repeated after applying load (say half full load) to the engine. After loading the engine, the engine rpm is adjusted to 650 rpm (N1) and the time taken to slow down to N2 rpm ( 600,550,500,450,.300 etc), after cutting the fuel supply is noted. Readings are tabulated and a graph is drawn taking time along X-axis and speed along Y-axis for both load and no load conditions. Select two speeds (maximum and minimum) such that the average is the speed at which frictional power is to find out. From the graph the time taken for the engine to slow down from max speed to minimum speed for no load (t1) and for half full load (t2) are found out. By using the equations the frictional power is then calculated.

Result.