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KULLIYAH OF ENGINEERING
INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
AEROSPACE ENGINEERING LAB IV
MEC 4760
SEMESTER 1, 2013/2014
HOT ATER ROCKET!
NAME AN" MATRIC NO#
MOHAMA" BASHIR BIN MOH" HAFI"$
1014407
LECTURER#
"R% RAE" ISMAIL KAFAFY
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ABSTRACT
Basically, this experiment is to study the performance of hot water rocket by evaluating its
temperature, exit velocity, mass flow rate, thrust and specific impulse. It is being done by
heating of the water to form steam that exits through the nozzle after activating the
solenoid valve to produce thrust. Throughout the experiment, the nozzle exit temperature,
nozzle inlet temperature and thrust is recorded by a relay connected to the computer. This
is essential in order to prove the theory behind the experiment stand correct. However, due
to its relatively simple and basic construction of the rocket, there may be have few
circumstances that can occur which will or may interrupt the result, causing errors to occur.
This set-up although simple is an effective way to achieve the experiment objectives.
OBJECTIVE
To study the performance of hot water rocket by evaluating its temperature, exit
velocity, mass flow rate, thrust and specific impulse.
To study the performance of simple hot water rocket.
INTRODUCTION
Hot Water Rocket (HWR) is a chemical and thermal rocket that uses water as a
propellant that is contained in a pressure vessel at a high temperature. It is being done this
way such that its saturated vapor pressure is significantly greater than ambient pressure.
HWR is categorized as to be part of a non-breathing engine. The water is allowed to
escape as steam through a rocket nozzle, by activating the solenoid valve through the
computer, to produce thrust. As the hot water goes through the nozzle and the pressure
reduces, the water flashes to steam pressing on the nozzle, and leaving at high speed. By
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the recoil the rocket accelerates in the opposite direction to the steam. The nozzle of hot
water rockets must be able to withstand high pressure, high temperatures and the
particularly corrosive nature of hot water.
For this experiment, we will undergo the process of a simple HWR to understand
the principle mechanism of the process. Specifically, the water is heated up to (120 C).
Figure 1: Hot Water Vapor release from Tank
Experiment Setup and Initial Condition Information
Specifications Values
Dt=0.02m Dt=0.018m Dt=0.010m
Diameter inlet, Di(m) 0.025 0.0254 0.0254
Area inlet, Ai(m2) 5.067 x 10
-45.067 x 10
-45.067 x 10
-4
Throat diameter, Dt(m) 0.020 0.018 0.010
Throat area, At(m2) 3.142 x 10
-42.54 x 10
-47.85 x 10
-5
Exit diameter, De(m) 0.0500 0.0256 0.0142
Exit area, Ae(m2) 2.00 x 10
-35.14 x 10
-41.59 x 10
-4
Nozzle area expansion ratio 6.371 2.02 2.02
Nozzle contraction ratio 1.613 1.991 6.452
Table 1.1: the dimensions of the nozzle inlet throat and exit
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PROPERTIES VALUES
Diameter of Tank, D (m) 0.2
Length of Tank, L (m) 1
Slenderness Ratio, L/D 5Volume of Tank, V (m
3) 0.00314
Maximum Mass of Water (L) 31.416
Table 1.2: Tank dimensions and specification
Initial tank temperature, Ti= 298.15K
Initial tank pressure, Pi= 1002.69 kPa
Initial mass of water, mi= 22378 kg
Gas constant, R = 461.5 J/kgK
K = Cp/Cv= 1.327
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Figure 2: Circuit setup for hot water rocket
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Figure 3: Hot Water Tank Figure 4: Data Acquisition
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Figure 5: Spring Balance Figure 6: Solenoid Valve
Figure 7: Pressure and Temperature Sensor
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PROCEDURE
1. We fill the tank with 32 litres of water.
2. Once filled the tank with the water, we heat the tank using heater to a temperature
approximately 120 C.
3. Then, we checked all the sensors functionality and calibrate the spring balance that
is used to measure thrust to zero values.
4. Once prepared, we activate the solenoid valve to release the steam.
5. The nozzle inlet, exit and tank temperatures are recorded into the computer and the
thrust is video recorded throughout the steam released.
RESULTS
Time (s) Mass (kg) Force (N) Tank Temperature
1 0.10 94.3766
2 1.10 94.3958
3 1.38 94.3821
4 1.36 94.3672
5 1.16 94.3711
6 1.16 94.3608
7 1.16 94.3688
8 1.16 94.3751
9 1.16 94.3553
10 1.16 94.3453
11 1.16 94.3443
12 1.16 94.3295
13 1.16 94.3114
14 1.16 94.3134
15 1.16 94.3300
16 1.16 94.3211
17 0.82 94.3384
18 0.44 94.3323
19 0.44 94.3257
20 0.44 94.321321 0.20 94.3184
22 0.15 94.3044
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Time (s) Mass (kg) Force (N) Tank Temperature
23 0.06 94.3012
24 0.04 94.2922
Table 1: Tabulated Result
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Figure 10: nozzle temperature and tank temperature
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DISCUSSIONS
From going through the experiment and result obtained, we are unable to
determined the performance of the hot water rocket. This is due to that the nozzle exitvelocity cannot be calculated as the exit temperature of the nozzle was not properly
recorded. According to the result obtained in Figure 10, we could observe that the exit
temperature starts with zero and decreases over time.
Theoretically, the exit temperature at the nozzle should have an initial value to be
more than zero, roughly at room temperature and due to the nature of the water vapor
being at high temperature released through the nozzle, the exit nozzle temperature should
gradually increase over time. This explained since enthalpy is constant during the flow, thetemperature will increase as the velocity decreasing. Therefore, the result obtained is in
fact, irrelevant.
The problem is probably due to the sensors at the nozzle not being properly
installed or maybe unknown problem occurred to the sensor. The Figure 11 below shows
us the data obtained from same experiment done in the past before us:
Figure 11: nozzle temperature vs time from previous experiment data
The graph clearly shows that the temperature keeps on increasing over time. Thus, the
data that we get from this experiment is not valid for further calculations of exit velocity,
thrust and the specific impulse. Below are the formulas to calculate the mentionedparameters:
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cp(T1 T2) = 1/2(v22 v12)
Assuming that we determined the flow rate 1st, the calculations are as follow:
=
However, the temperature in the tank is in constant after the vapor is released. We could
observe from Figure 8 that the maximum thrust is about 14N. From the calculation above,
the specific impulseis quite low. This value is invalid as the Figure 9 shows the rocket
sustain a constant thrust about 12s.
CONCLUSIONS
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