Lab T1: Compression Ignition (Diesel) Engine Lab Instructor: M Lab T1: Compression Ignition (Diesel) Engine Lab Instructor: M.reza(Mamzi) Naghash Location: 1B30

Objectives To become familiar with the operation of a compression-ignition (diesel) engine To determine the effect of load variation at constant speed on Mechanical efficiency The primary characteristics of in-cylinder pressure development To perform an energy balance on the engine

cylinder volume greatest. Engine Nomenclature Fuel Injector Valves Cylinder Piston Connecting Rod Crankshaft Piston at bottom dead center (BDC), cylinder volume greatest. Piston at top dead center (TDC), cylinder volume least Swept Volume = Volume A – Volume B Compression Ratio = Volume A / Volume B

Operation of a 4 stroke compression ignition engine Cylinder Volume Cylinder Pressure TDC BDC Maximum cylinder pressure Combustion commences Fuel injection commences Physical & chemical ignition delay Exhaust B- Intake Stroke P-V Diagram of the compression ignition cycle A to C is Intake stroke Piston starts with minimum volume at A when it is at TDC Intake valve opens Piston moves down Pressure stays at near atmospheric pressure C A

Operation of a 4 stroke compression ignition engine Cylinder Volume Cylinder Pressure TDC BDC Maximum cylinder pressure Combustion commences Fuel injection commences Physical & chemical ignition delay Exhaust Induction P-V diagram of the beginning of the compression stroke Both valves are closed Piston begins to move upwards from C to D The air in the cylinder is compressed Pressure and temperature rise D C

Operation of a 4 stroke compression ignition engine C to E is called the Compression Stroke Cylinder Volume Cylinder Pressure TDC BDC Maximum cylinder pressure Combustion commences Fuel injection commences Physical & chemical ignition delay Exhaust Induction E P-V diagram of the entire compression stroke (From C to E) Fuel injection begins at D before the piston has reached TDC Combustion commences a short time later Delay is due to the fact that the chemical reaction of combustion takes a finite time No ignition source like a spark plug Fuel air mixture ignites due to the high air temperature Sharp rise in pressure as the products of combustion expand D C

Operation of a 4 stroke compression ignition engine E to G is called the Power Stroke Cylinder Volume Cylinder Pressure TDC BDC Maximum cylinder pressure Combustion commences Fuel injection commences Physical & chemical ignition delay Exhaust Induction F – Power Stroke E P-V diagram of power stroke (From E to G) Expanding gasses in the cylinder force the piston down This is when the usable power is produced G

Operation of a 4 stroke compression ignition engine Cylinder Volume Cylinder Pressure TDC BDC Maximum cylinder pressure Combustion commences Fuel injection commences Physical & chemical ignition delay H- Exhaust Stroke Induction Once piston reaches BDC the exhaust valve opens Back at atmospheric pressure Piston moves up to expel the exhaust and the cycle begins again It is called a 4 stroke cycle engine because the piston makes four strokes to complete one engine cycle G A

Injector Needle Lift and Fuel Line Pressure Fuel Injection Pump Rack Displacement Transducer Pfuel Fuel Supply Fuel Spill Port Injector Needle Rotate Shaft to Adjust Cam at ½ Engine Speed

Petter Diesel Engine Injector Pump PLUNGER FUEL SPILL PORT FUEL SUPPLY PORT HELIX (The position of the helix to the fuel spill port meters the amount of fuel delivered to the injector by changing the effective stroke of the pluger.) In this experiment we will vary the injector pump setting to allow more or less fuel to enter the engine Works by adjusting the control rack which turns the helix on plunger. The fuel can spill to both sides of the plunger Intake the plunger moves down to allow fuel in the inlet port As it moves up the pressure increases until it is sufficient to overcome the spring and fuel flows to the injector Once the helix passes the bypass port, fuel is allowed to flow out the fuel spill

In Lab Procedure Collect data at four operating points. Constant RPM (N=1050 RPM) Increase fuel injection and obtain N=1050 by increasing load At each operating point Await steady state (exhaust gas temp.) Fill out data sheets Capture Pcyl and V vs time waveform on oscilloscope At intermediate operating point (3rd operating point) 4 Pcyl and V vs. time for single cycles Injector needle lift, Pfuel, Pcyl , vs time

Calculations and Discussion Brake Power Indicated Power Need to plot P-V diagrams for each load Specific Fuel Consumption Volumetric Efficiency Air/Fuel Ratio Mechanical Efficiency Brake Thermal Efficiency Mass flow rate of Exhaust “Willans Line” Test Energy Balance Plot a Pcyl and V vs. t diagram for a cycle at the 3rd load condition Pcyl vs. t for 4 cycles at 3rd test condition V vs. t for 4 cycles at 3rd test condition Plot injector needle lift, fuel line pressure, and Pcyl vs. time Plot the first derivative of Pcyl on a Pcyl vs. t diagram Preliminary Discussion Operation of fuel injector pump Timing of fuel pressure, injector needle lift, pcyl Discuss Signals on the scope Predictions of how performance measures will change between operating points How does the data differ from the idealized Diesel cycle (what assumptions are not valid in a real engine)

1. Brake Power Rotational speed of engine [rev/s] Brake load [N] Power measured at the output shaft Brake load [N] Load arm radius [m]

3. Specific Fuel Consumption Fuel consumption (kg/h) Brake Power

4. Volumetric Efficiency Orifice coefficient Orifice area Ambient Differential pressure across Orifice (Pa) Free air delivery is the volumetric rate that air is actually delivered to the cylinder Swept volume rate is the rate at which the cylinder volume actually changes Measures if the valve cannot incorporate air fast enough during intake

5. Air/Fuel Ratio

6. Mechanical Efficiency Brake Power Indicated Power

7. Brake Thermal Efficiency Mass flow rate of fuel Lower heating value for fuel

8. Mass Flow Rate of Exhaust Conservation of Mass

11. Pcyl and V vs. t Label the four strokes on a Pcyl and V vs. t diagram for one of the four cycles observed at the 3rd test condition. P V

14. Injector Needle Lift, Fuel Line Pressure, and Pcyl vs. t Plot injector needle lift, fuel line pressure, and Pcyl vs. time on a single plot. Comment on the relationship between these three. (Focus on the order and timing of when things occur).

15. Calculate the first derivative of in-cylinder pressure for ONE cycle taken at the 3rd load condition. Plot it on the corresponding Pcyl vs. time diagram and comment on the relationship of this graph to the operation of the engine.

What do we want in our logbook: Explain a summary of experiment Explain about general operation of injector pump. Thermodynamic cycle and changes in pressure and volume What is the relation between of fuel injection, combustion and rate of change in pressure in cylinder. Fill data sheet completely.

2. Indicated Power: Proportional to the area within the power and compression strokes minus the area within the intake and exhaust strokes. Only 2 of 4 strokes considered Area within intake and exhaust strokes is very small and can be neglected! Cylinder Volume Cylinder Pressure TDC BDC Maximum cylinder pressure Combustion commences Fuel injection commences Physical & chemical ignition delay Exhaust Induction Area under P-V Indicated power is calculated by the area inside the P-V diagram The Intake and exhaust strokes are negligible compared to the comperession and power strokes Can neglect them N/2 because only 2 of the four strokes are considered

Step 1: Plot P-V Diagram P-V Data will look something like this Noisy Goes below the origin

Offseting: Find the minimum data

PV diagram with offsets

Filtering: Modifying data

P-V Diagram after Offsets and Filtering We only do this to make the data easier to work with. It would work without because we are just finding the area inside the P-V diagram

Indicated Power Mean effective pressure basically transforms the integral of the P-V diagram into a rectangle Find area inside the P-V diagram Power generated - Power used in compression stroke. Use the same area can find a constant pressure

Indicated Power Indicated Mean Effective Pressure Why N/2 ?

Numerical Integration 1 2

Numerical Integration

Indicated Mean Effective Pressure

9. Willans Line for Mechanical Losses Fuel Consumption Without Mechanical Losses Brake Power (kW) Mechanical Losses ~ 0.8 kW

10. Energy Balance IN OUT Calculate heat transferred to atmosphere: