Thermodynamics Lab Report

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Assignment 2: (Laboratory Project) Due Date: Friday 26

th September 2014, 4:00 pm

Please print to pdf and submit online through learning at Griffith

Weighting: 15% of the total marks for this course. This is subdivided as follows: Labs 1 & 2: 10% (This report – Completed in your own time) Labs 3 & 4: 5% (Completed during the lab time)

Please complete the laboratory exercises and submit a report combining labs 1 and 2. The report should be produced with a word processor such as Microsoft Word. Although laboratory work will be done in groups, each student must submit their own individual laboratory report.

Laboratories 1 and 2: Internal combustion engine efficiency You are part of an engineering team that is developing a trickle irrigation system for agricultural purposes. The system consists of a 25000 L water tank on a stand which is 13 m high and a petrol or diesel powered pump to pump the water from a dam up into the elevated tank (Fig. 1). Your task is to report on the expected performance (from a thermodynamics point of view) of some available motor and pump combinations for the system. You must base your conclusions on experimental data you have collected from the laboratory. The range of choices under consideration has been narrowed to three pumps and two engines. One of the engines is a 232 cc four- stroke diesel motor and the other is a 172 cc four-stroke petrol motor. These engines are located in the mechanical engineering lab at Griffith University along with test beds and dynamometers which you will use to measure their performance and simulate the load that would be placed on the motor by the pump.

Another engineer on the team has analized the piping system in Fig. 1 (you will learn how to do this when you study fluid mechanics) and has found that if the flow rate, Q

13 m

2 m

Pump and motor

25 kL

Dam

Fig. 1 System in which motor is to be used

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(m 3 /s) is decided then the required difference in head (meters of water) between the

inlet and outlet of the pump follows the following equation (Note: multiply hpump by (ρg) to get pressure difference between pump outlet and inlet in pascals):

2.1 15 Q

D h

pump += (1)

This equation is usually called the ‘system curve’. It is unique for each pipe system. It is different depending on the length and diameter of the pipe, the pipe fittings selected for the system and the difference in elevation between the supply water and tank. D is the inlet diameter of the pipe (in meters) and Q is the flow rate in m

3 /s. Q

2 /D

4 appears

in the equation because losses in a piping system are usually proportional to the square of the water velocity inside the pipe. The engineer suggests a pipe with inside diameter D = 35 mm = 0.035 m. Fig. 2 shows the characteristic perfomance curves for three different pumps being considered: Pump A, Pump B and Pump C supplied by the manufacturer. The curves show the difference in head supplied by the pump for any given flow rate. Efficiencies listed in Fig. 2 are mechanical efficiencies for the pump. If you plot Eq. (1) on the graph shown in Fig. 2, the points where Eq. (1) intercepts the characteristic curves for pumps A, B and C will show the required operating conditions for your motor.

Flow rate

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��

� ABACDBE�

�CDF�A ��BFC�A�FAB��C��F��

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Fig. 2 Pump characteristic curves

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Using Fig. 2, Eq. 1 and the equipment available for testing the internal combustion engines in the lab, you are required to supply the following information:

1. The noise in dB made by each of the motors (measured in the laboratory). Note also

the location where the noise measurement was made.

2. The duty points for pumps A, B and C (i.e flow rate, head and pump efficiency

corresponding to where Eq. (1) intersects the characteristic curves shown in Fig. 2).

3. The power (and torque) required to turn the shaft of the pump at each of the three duty

points.

4. Whether or not the engines in the lab are capable of delivering enough power to run

the pumps at each of the duty points.

5. The thermal efficiency of the engines at each of the three duty points at the specified

rpm (measured in the laboratory)

6. Time needed to fill the 25000 L water tank for each pump/motor combination.

7. No. of litres of fuel (and approximate cost) required to fill the 25000 L tank for each

pump/motor combination?

8. The increase in potential energy of 25000 L of water as moves from the dam to the

tank.

9. The energy used by the motor in filling the water tank for each pump/motor

combination.

10. The overall thermal efficiency of the system (use lower heating value for the fuel).

11. The air/fuel ratio at the conditions tested.

12. The number of kg of carbon dioxide released to the atmosphere by filling the tank for

each pump/motor combination.

13. A recommendation as to the best pump/motor combination for this purpose and an

explanation of why you are making this recommendation.

14. Any suggestions of how the efficiency of the system may be improved.

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Report Format

It is expected your report will be typed using a word processor such as Microsoft Word (apart from raw data and any hand written calculations that you may include in the appendix) and will contain the following sections: Title: Name & Date: Summary: Briefly describe (approximately half a page) the purpose of the report and the main findings of your investigation. Equipment: Include photograph(s) of the apparatus used Results: You should summarize your results in a table such as is shown below: Table 1: Results. You should explain briefly how your calculations were done including any assumptions you have made. You should also include a graph of the experimental results from the lab showing the efficiencies of the engines for different loads (i.e. thermal efficiency of the engine (vertical axis) against power output (horizontal axis)). Conclusions and Recommendations: Here you should give a recommendation as to the best pump/motor combination for this purpose and an explanation of why you are making this recommendation. You should also include any suggestions of how the efficiency of the system may be improved. Appendix 1: Raw Data This section should contain the raw data you collected in the lab Appendix 2: Sample Calculations This section should contain one of the following:

• hand written sample calculations

• or a printout from a spreadsheet that you used to do your calculations (with formulae displayed)

• or a printout of a computer program code (e.g. Matlab) that you made to do your calculations.

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Table 1: Results Engine: Diesel Petrol Noise (dB):

Pump: A B C A B C Flow rate (kg/s)*: (water)

Pump Head (m)*:

Pump Efficiency*:

RPM*:

Power Required from motor (kW)*:

Torque Required from motor (N.m)*:

Can engine deliver required power?

Thermal efficiency of engine (%)

Time needed to pump 25000 L of water

No. of litres of fuel required to pump 25000 L of water (L)

Cost of fuel required to pump 25000 L ($)

Increase in potential energy of 25000 L of water (J)

Energy used by motor to fill the tank (J)

Overall thermal efficiency of the system

Air/Fuel Ratio:

Mass of CO2 produced by pumping 25000 L of water (kg):

Recommended pump/motor combination:

*These correspond to the duty points and should be determined before doing the lab.

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Please include the following tables as an appendix in your report with your engine test results for each engine.

Date of test:

Time of test:

Test bed serial No.

Engine serial No.

Engine type Diesel

Engine size (Litres)

No. of strokes 4

Fuel type

Fuel density (kg/m 3 )

Fuel calorific value (kJ/kg)

Ambient air pressure

Airbox orifice dimensions (m)

2503ENG Thermodynamics – Lab. Assignment

Air and Exhaust

Airbox

differential pressure

(Pa)

Exhaust gas temperature

(°C)

Ambient air temperature

(°C)

Fuel

Fuel drain time

(s)

Fuel

volume

(mL)

Diesel Engine

Engine output power

(W)

Engine torque

(N.m)

Engine speed

(rpm)

Meas. No.

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Date of test:

Time of test:

Test bed serial No.

Engine serial No.

Engine type Petrol

Engine size (Litres)

No. of strokes 4

Fuel type

Fuel density (kg/m 3 )

Fuel calorific value (kJ/kg)

Ambient air pressure

Airbox orifice dimensions (m)

2503ENG Thermodynamics – Lab. Assignment

Air and Exhaust

Airbox

differential pressure

(Pa)

Exhaust gas temperature

(°C)

Ambient air temperature

(°C)

Fuel

Fuel drain time

(s)

Fuel

volume

(mL)

Petrol Engine

Engine output power

(W)

Engine torque

(N.m)

Engine speed

(rpm)

Meas. No.