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1. Objectives To become familiar with the operation of a compression-ignition (diesel) engine To determine the effect of load variation at constant speed.

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Presentation on theme: "1. Objectives To become familiar with the operation of a compression-ignition (diesel) engine To determine the effect of load variation at constant speed."— Presentation transcript:

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2 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 2

3 3 Piston at bottom dead center (BDC), cylinder volume greatest. Piston at top dead center (TDC), cylinder volume least Compression Ratio = Volume A / Volume B Swept Volume = Volume A – Volume B Engine Nomenclature Crankshaft Connecting Rod Fuel Injector Valves Cylinder Piston

4 4 Operation of a 4-stroke compression ignition engine

5 5 Operation of a 4-stroke compression ignition engine A C B

6 6 Operation of a 4 stroke compression ignition engine D C

7 7 D C E C to E is called the Compression Stroke Operation of a 4 stroke compression ignition engine

8 8 G E E to G is called the Power Stroke F – Power Stroke Operation of a 4 stroke compression ignition engine

9 9 G A

10 10 Apparatus Schematic

11 11 Petter Diesel Engine Injector Pump 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.) FUEL SPILL PORT FUEL SUPPLY PORT PLUNGER

12 Injector Needle Lift and Fuel Line Pressure 12 Fuel Injection Pump Rack Injector Cam at ½ Engine Speed Rotate Shaft to Adjust Fuel Supply P fuel Displacement Transducer Injector Needle Fuel Spill Port

13 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 (constant exhaust gas temp.) Fill out data sheets Capture P cyl and V vs time waveform on oscilloscope At intermediate operating point (3 rd operating point) 4 P cyl and V vs. time for single cycles Injector needle lift, P fuel, P cyl, vs time 13

14 14 1.Brake Power 2.Indicated Power a)Need to plot P-V diagrams for each load 3.Specific Fuel Consumption 4.Volumetric Efficiency 5.Air/Fuel Ratio 6.Mechanical Efficiency 7.Brake Thermal Efficiency 8.Mass flow rate of Exhaust 9.“Willans Line” Test 10.Energy Balance 11.Plot a P cyl and V vs. t diagram for a cycle at the 3 rd load condition 12.P cyl vs. t for 4 cycles at 3 rd test condition 13.V vs. t for 4 cycles at 3 rd test condition 14.Plot injector needle lift, fuel line pressure, and P cyl vs. time 15.Plot the first derivative of P cyl on a P cyl 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)

15 15 Rotational speed of engine [rev/s] Brake load [N]Load arm radius [m] Brake Power [W]

16 2. Indicated Power: Proportional to the area within the power and compression strokes minus the area within the intake and exhaust strokes. 16 Area within intake and exhaust strokes is very small and can be neglected! Only 2 of 4 strokes considered Area under P-V

17 Step 1: Plot P-V Diagram 17 P V

18 Offsets and Filtering 18

19 P-V Diagram after Offsets and Filtering 19 P V

20 Indicated Power 20

21 Indicated Power 21 Indicated Mean Effective Pressure Why N/2 ?

22 Numerical Integration

23 Numerical Integration 23

24 Indicated Mean Effective Pressure 24

25 3. Specific Fuel Consumption 25 Fuel consumption (kg/h) Brake Power (W or kW)

26 4. Volumetric Efficiency 26 Orifice coefficientOrifice area Differential pressure across Orifice (Pa) Ambient

27 5. Air/Fuel Ratio 27

28 6. Mechanical Efficiency 28 Brake Power Indicated Power

29 7. Brake Thermal Efficiency 29 Lower heating value for fuelMass flow rate of fuel

30 8. Mass Flow Rate of Exhaust Conservation of Mass 30

31 9. Willans Line for Mechanical Losses 31 Fuel Consumption Brake Power (kW) Without Mechanical Losses Mechanical Losses ~ 0.8 kW

32 10. Energy Balance 32 IN OUT Calculate heat transferred to atmosphere:

33 11. P cyl and V vs. t Label the four strokes on a P cyl and V vs. t diagram for one of the four cycles observed at the 3 rd test condition. 33 P V

34 12. P cyl vs. t Plot P cyl vs. t for all four cycles taken at the 3 rd load condition. Comment on the cyclic variation between the four cycles. 34

35 13. V vs. t Plot V vs. t for all four cycles taken at the 3 rd load condition. Comment on the cyclic variation between the four cycles. 35

36 14. Injector Needle Lift, Fuel Line Pressure, and P cyl vs. t Plot injector needle lift, fuel line pressure, and P cyl vs. time on a single plot. Comment on the relationship between these three. (Focus on the order and timing of when things occur). 36

37 15. Calculate the first derivative of in-cylinder pressure for ONE cycle taken at the 3 rd load condition. Plot it on the corresponding P cyl vs. time diagram and comment on the relationship of this graph to the operation of the engine. 37

38 38 Engine Power GeneratedFuel Consumption DynoBrakeRot.BrakeIndicatedMechQuantityTimeFuelSFCBTE Test No.Load SpeedPower Effof Fuel Cons. (volts)(Newtons)(rpm)(Watts) (%) (ml)(sec)(kg/hr)(kg/kWh)(%) (amps)

39 39 Air ConsumptionCooling WaterExhaust GasAmbient Diff.FADA/FVolInletOutletFlowTemp.Mass Temp.Press. Test No.Press. ratioEffTemp. Rate Flow (mmH 2 O)(m 3 /s) (%)( o C) (l/min)( o C)(kg/s)( o C)(mmHg)

40 Questions? Final Reports Do all calculations and plots, and explain what EACH means. Explain the differences in performance values between the four load conditions. Limit Background info, focus on discussions. SAFE! 40


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