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OCD045
UNIVERSITY OF BOLTON
RAK ACADEMIC CENTRE
BENG (HONS) MECHANICAL ENGINEERING
SEMESTER TWO EXAMINATION 2017/2018
THERMOFLUIDS & CONTROL SYSTEM
MODULE NO: AME5003
Date: Wednesday 30 May 2018 Time: 2:00 – 4:00 INSTRUCTIONS TO CANDIDATES: There are 6 questions. Answer 4 questions. All questions carry equal marks. Attempt TWO questions from PART A
and TWO questions from PART B Marks for parts of questions are shown
in brackets. CANDIDATES REQUIRE : Take density of water = 1000 kg/m3
Formula sheets provided
Page 2 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
PART A
Q1. a) Derive from Bernoulli’s theorem expressions for the theoretical velocity
and discharge through a venturimeter in a pipe of diameter d1 as shown
in Figure Q1a.
Figure Q1a. Venturimeter
(13 marks)
b) A pitot tube is inserted in a pipe of 300mm diameter. The static
pressure in pipe is 100mm of mercury(vacuum).The stagnation
pressure at the centre of the pipe recorded by the pitot tube is
0.981N/cm2.Determine the rate of flow of water through the pipe if
mean velocity of the flow is 0.85 times the central velocity. Given
Cv=0.98.
(7 marks)
c) An orifice meter with orifice diameter 15cm is inserted in a pipe of 30cm
diameter. Given the pressure difference measured by a mercury-oil
differential manometer on the two sides of the orifice meter as 50cm of
mercury. Find the rate of flow of oil of specific gravity 0.9 when the co-
efficient of discharge of the meter is 0.64.
(5 marks) Total 25 marks
Please turn the page
Page 3 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
Q2. a) A pipe line carrying oil of specific gravity 0.87 changes in diameter from
200mm diameter at a position A to 500mm diameter at a position B
which is 4metres at a higher level as shown in Figure Q2a.If the
pressures at A and B are 9.81N/cm2 and 5.886N/cm2 and the discharge
is 200litres/s determine the following:
i. Loss of head (7marks)
ii. Direction of flow (8 marks)
Figure Q2a. Line diagram of the system
b) An air compressor takes in air having an enthalpy of 100kJ/kg.The air is
compressed to a final condition at which the enthalpy is 180kJ/kg.As
the air travels through the compressor, it losses 20kJ/kg of heat(Q) as
shown in FigureQ2b . Using the steady flow equations evaluate the
work of the compressor.
FigureQ2b.Air compressor (10marks)
Total 25 marks
Please turn the page
Page 4 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
Q3 a) A 300mm diameter pipe carries water under a head of 20metres with a
velocity of 3.5m/s as shown in Figure 3a.Let p1 ,p2 be the inlet and outlet
pressures and v1,v2 be the corresponding velocities of flow at inlet and
outlet . If the axis of the pipe turns through 450, determine the following:
i) Magnitude of the resultant force at the bend (6 marks)
ii) Direction of the resultant force at the bend. (7 marks)
Figure 3a.Diagrammatic representation of 45o bend
b) A piston and cylinder machine contains a fluid system which passes
through a complete cycle of four processes. During a cycle, the sum of
all heat transfers is -170kJ.The system completes 100 cycles per minute
.Complete the following Table Q3.b showing the method for each item,
and computes the net rate of work output in kW.
Table Q3.b Heat, Work and internal energy transfer for a cycle
(12 marks)
Total 25 marks
Please turn the page
Page 5 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
PART B
Q4 a) For the spring damper and mass system shown in Figure Q4. (a), where
M1 = 3 Kg, K1 = 1 N/m, B1 = 3 Ns/m M2 = 2 Kg, K2 = 2 N/m, B2 = 4 Ns/m F(t) = force applied
Figure Q4. (a) Spring damper mass system
(i) Develop differential equations for the system given in Q4.(a) (2 marks)
(ii) Determine the Laplace transforms of the differential equations
obtained from Q4( i) above. (2 marks)
(iii) Determine the transfer function G(s) = X1(s)/F(s), Assume that the
system is subjected to a unit step input and the initial conditions of the
system are zeros (i.e. at time = 0, x, x’, x’’ are all zeros).
(8 marks) b) With the aid of a block diagram explain how an RFID system works.
(8 marks)
Please turn the page
Q4 continued over the page…
B1
K1
X1
K2
M2
M1
X2
F(t)
B2
Page 6 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
Q4 continued…
c) Derive the mathematical model for the heat transfer system shown in Figure Q4.c.
Figure Q4.c Thermal Water Heating System
Given:
Thermal resistance of the insulation: R (oC/joule/sec)
Thermal capacity: C (joule/oC)
Heat input to the system: q (joule/sec)
Assume that the Specific thermal insulation is negligible and tank is
thoroughly mixed so that uniformity of temperature is maintained.
(5 marks)
Total 25 marks
Q5 a) Block diagram for a closed loop control system for a thermostatically
controlled air-conditioning system for an automobile is shown in Figure
Q5.(a).The system is to have a damping ratio of 0.7.Determine the value
of K to satisfy this condition and calculate the settling time, peak time and
maximum overshoot for the value of K thus determined.
Please turn the page
Water
Output Water
Temperature ɵo
Thermal Insulation
Input Water
Temperature ɵi
Electric Heating
Page 7 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
Q5 continued over the page…
Q5 continued…
Figure Q5. (a) Thermostatically controlled air-conditioning system
(11 marks)
(b) The transfer function of a unity feedback control system for a pick and
place robotic arm is given by
Obtain an expression for unit step response of the system. (3 marks)
(c) A robotic arm has an open loop transfer function for its angular position of
The input of the system is a ramp input changing at the rate 10 degrees
and K has the values 1, 10,100.
i) What will be the steady state errors for different K values when it is
an open loop system.
(5 marks)
ii) What will be the steady state errors for different K values when it is
an closed loop system.
(5 marks)
Page 8 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
iii) Comment on the significance of increasing the value of K.
(1 marks)
Total 25 marks
Please turn the page Q6 (a) Analyse the stability of a control system for speed control of a DC motor
given in Figure Q6. (a) Based on location of poles and zeros in S
plane for the following conditions.
i) Open loop stability (4 marks)
ii) Closed loop stability K=10 (3 marks)
iii) Closed loop stability K=200 (3 marks)
Figure Q6. (a) Block diagram for an air traffic control systems
(b) Large welding robots are widely used in automobile assembly lines.
The welding head is moved to different positions on the automobile
bode, and rapid, accurate response is required. The characteristic
equation for the welding system is
s5 +1.5 s4 + 2s3 + 4s2 + 5s + 10 = 0
Using Routh-Hurwitz stability criterion determine the stability of the
system.
(4 marks)
(c) Reduce the following block diagram for an air traffic control systems shown
in Figure Q6. (c) and determine the system transfer function.
Please turn the page
Page 9 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
Q6 continued over the page…
Q6 continued…
Figure Q6. (c) Block diagram for an air traffic control systems
(6 marks)
(d) Discuss the various types of sensors that can be employed in water boiler
automation system for continuous monitoring of temperature, pressure and
water level.
(5 marks)
Total 25 marks
END OF QUESTIONS
Page 10 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
Please turn the page for the Formula Sheet
FORMULA SHEET
R= 287 J/ Kg K P = F/A ρ = m/V m. = ρAV P = ρgh Bernoulli’s Equations
Q= A v Q=V/t
Flow meter Equation
Fluid Force Calculation at the bend
.ΔMΔt
ΔMF
Fx = ρQ( v1x –v2x) + (p1A1)x + (p2A2)x
Fy = ρQ( v1y –v2y) + (p1A1)y + (p2A2)y
FR = Thermodynamics
Page 11 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
Q = W+ΔU + ΔPE + ΔKE Q=mC ΔT PV=mRT Cp – Cv =R
Control Systems Laplace Transforms A unit impulse function 1
A unit step function s
1
A unit ramp function 2
1
s
Block Diagram Reduction Blocks with feedback loop
Page 12 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
G(s) = )()(1
)(
sHsGo
sGo
(for a negative feedback)
G(s) = )()(1
)(
sHsGo
sGo
(for a positive feedback)
Blocks G1(S) & G2(s) in series G(s) = G1(S) *G2(s) Blocks G1(S) & G2(s) in parallel G(s) = G1(S) +G2(s) Steady-State Error
)]()(1
1[lim
0s
sGse i
os
ss
(For the closed-loop system with a unity feedback)
Time Response for second-order systems
d = n (21( )
ᶲ = tan-1(
)1( 2)
tr = ( - ᶲ)/d
tp = /d
n
4= ts
%100))1(
(exp = Mp.2
Page 13 of 13 University of Bolton RAK Academic Centre BEng (Hons) Mechanical Engineering Semester 2 Examination 2017/2018 Thermofluids & Control System Module No. AME5003
End of Paper