The American University in Cairo Department of Mechanical Engineering MENG 362: Applied Fluid Mechanics

Lab Report #1

Experiment: Nozzle Pressure Distribution Unit

Prof. Mohamed El Morsi Eng. Asmaa

Malak Sabry900121154Yossr El Sayed 900120431Ahmed Al Meghalawy 900114647

Table of ContentsAbstract3Introduction4Theory5Nozzle A Profile5Nozzle B Profile6Nozzle C Profile7Methodology8Device used8Process Diagram and Elemnet Allocation9Device Description9Device Features10Results11Tables of Data11Calculations for isentropic flow12Calculations for the shockwave case12Graphs14Calculations & Recommendations15

List of Figures

Figure (1) Shape of the pressure Distribution for nozzle A5Figure (2) Shape of the pressure Distribution for nozzle B6Figure (3) Shape of the pressure Distribution for nozzle C7Figure (4) Pressure Nozzle distribution Unit8Figure (5) Process Diagram and Element Allocation9Figure (6) Graph of Ratio Vs Nozzle length14Figure 7 Graph of Mach Number Vs Nozzle length14 Abstract

In this experiment,

Introduction

Compressible flow through nozzles is a very interesting component of most syllabuses courses for engineers and technologies. Until now, experimental equipment for demonstrating and investigating the pressure distribution and mass flow rate in nozzles has usually used steam. This is because the quantity of air needed is beyond the capability of most of the air compressors usually installed. While steam is quite satisfactory for demonstrating the various effects in a nozzle, a boiler, with its heavy demand for energy, must be fired some time before the test is to start, and condenser with cooling water supply, etc.. Is needed, With these disadvantages in mind P.A. Hilton have designed the nozzle distribution unit described in this report. This is a bench top unit which uses compressed air at 7 to 9 atmospheres at the rate of 8 Gramm/s. this is available from the type of compressor which is usually installed for workshop services or for laboratory investigations. The power input needed to produce this quantity of air is only about 2.5 Kw, and there are no stand-by losses. No additional services are required and the unit is ready for use as soon as the air is available.

Theory

Nozzle A Profile

Figure (1) Shape of the pressure Distribution for nozzle A

Nozzle B Profile

Figure (2) Shape of the pressure Distribution for nozzle B

Nozzle C Profile

Figure (3) Shape of the pressure Distribution for nozzle C

Methodology

Device used

Figure (4) Pressure Nozzle distribution Unit

PROCESS DIAGRAM AND ELEMENTS ALLOCATION

Figure (5) Process Diagram and Element Allocation

Device Description

This unit has been specifically designed to demonstrate the phenomena associated to fluxes through nozzles and to allow the students investigating quickly the pressure distribution in it. Besides, it allows the investigation of the mass flow rate through convergent-divergent and convergent nozzles. Since the unit works with ambient temperature air, it is stabilized quickly and its energy consumption is only the necessary one to impulse a relatively small compressor. Compressed air at a 7 to 9 bars pressure, supplied from an external service. It passes through the filter/regulator, located on the back part of the unit. In the unit, the air passes through a control valve, which allows an accurate control of the pressure at the inlet of the nozzle. The pressure and inlet temperature are measured and then the air is expanded through the nozzle chosen. When discharging from the nozzle, the pressure is controlled by other valve, and the air goes finally through a flowmeter to the atmosphere. The nozzles have been made of brass, have been mechanized accurately and several pressure tappings are available, being each one connected to its own manometer to indicate the static pressure. Device Features

Unit is provided with three nozzles ( one convergent and two convergent-divergent) Each nozzle is provided with pressure tappings connected directly to the individual pressure gauge Nozzles can be changed in two minutes without the use of tools Works at ambient temperature Allows students to make a comprehensive investigation in a normal laboratory period Gives students an opportunity to calibrate equipment. Uses only 8 gramme of air per second at 7 to 9 atmosphere gauge pressure

Results

Tables of Data

Assuming Pt1=650 kPa;Pb=0Pb =200 kPaPb =400 kPaPb =550 kPaPb =650 kPa

SectionP (kPa)P (kPa)P (kPa)P (kPa)P (kPa)

1620620620660670

2400400400610640

3240240366620640

4180180426635680

5120160435620650

6100230460650670

7100240460640670

8100280505660700

Pb =0Pb =200 kPaPb =400 kPaPb =550 kPaPb =650 kPa

SectionP/Pt (0)P/Pt (200)P/Pt (400)P/Pt (550)P/Pt (650)

10.9538460.88571430.885714290.9428571430.95714286

20.6153850.57142860.571428570.8714285710.91428571

30.3692310.34285710.522857140.8857142860.91428571

40.2769230.25714290.608571430.9071428570.97142857

50.1846150.22857140.621428570.8857142860.92857143

60.1538460.77233040.657142860.9285714290.95714286

70.1538460.805910.657142860.9142857140.95714286

80.1538460.94022830.721428570.9428571431

Pb =0Pb =200 kPaPb =400 kPaPb =550 kPaPb =650 kPa

SectionMMMMM

10.2606950.42001610.420016080.2911501430.25093501

20.862550.93108020.931080170.447792770.36009761

31.2831971.33747071.00882120.4200160780.36009761

41.488621.53961320.873093440.3757370070.20391843

51.7613321.790.853214290.4200160780.32710442

61.8803030.61880.798278680.3271044160.25093501

71.8803030.56380.798278680.3600976130.25093501

81.8803030.29780.699221750.2911501430

Calculations for isentropic flow

Calculations for the shockwave case

(Pb=200 kPa)

A_2=3.142 A_5=4.486 A_6=4.988 A_7=5.557 A_8=6.114 Ma_5=1.79 Ma_6=0.6188 Ma_7=0.5638 Ma_8=0.2978 P_t2=297.8

Graphs

Figure (6) Graph of Ratio Vs Nozzle length

Figure 7 Graph of Mach Number Vs Nozzle length

Calculations & Recommendations

The data measured from the experiment were compared with the theoretical data. Theoretically, we assumed that all the equations and the graphical representations are based on adiabatic, isentropic and internally reversible processes. The results of the calculations were approximately the same as the ideal conditions and they have the same behavior. However, there is a percentage of error concerning the numerical values. These errors can be caused by human errors and some errors within the assumptions made before the experiment. The human error can be a parallax error, the readings were taken manually. The measurements were taken very quickly which will decrease the accuracy of it. Another source of error is the accuracy of the equipment itself. The most important source of error is the assumptions and the approximations made in the beginning of the experiment. First, the pressure at the beginning is assumed, hence in order to decrease the error it should be measured during the experiment. Secondly, the process is considered to be reversible which is not the case. In order to increase the accuracy of the results, more cross sections of the nozzle must be studied in order to determine the approximate exact place of the shockwave.