university of bolton western international college … · 2019-07-26 · page 6 of 12 university of...

OCD037

UNIVERSITY OF BOLTON

WESTERN INTERNATIONAL COLLEGE FZE

BENG (HONS) MECHANICAL ENGINEERING

SEMESTER TWO EXAMINATION 2018/2019

THERMOFLUIDS & CONTROL SYSTEM

MODULE NO: AME5013

Date: Wednesday 22nd May 2019 Time: 2:00pm – 4:00pm 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

of 12 University of Bolton Western International College FZE BEng (Hons) Mechanical Engineering Semester 2 Examination 2018/2019 Thermo fluids & Control System Module No. AME5013

PART A

Q1. a) Derive from Bernoulli’s theorem expressions for the theoretical velocity

and discharge through an orifice meter in a pipe of diameter ‘D’

creating a vena contracta at a diameter d as shown in Figure Q1a.

Assume a U-tube differential manometer is connected to measure the

pressure head ‘h’ from the readings shown by the manometer ∆x.

Assume all parameter units in SI system.

Figure Q1a. Orifice meter

(13 marks)

b) Explain the hydraulic co-efficients of velocity (Cv), contraction (Cc) and

discharge (Cd) and hence prove that Cd = Cc x Cv.

(7 marks)

c) A horizontal venturimeter with inlet diameter 30 cm and throat diameter

20cm is used to measure the flow of oil of specific gravity 0.9.The

discharge of oil through venturimeter is 70 litres/sec. Determine the

reading of the oil-mercury differential manometer. Given Cd= 0.98

(5 marks) Total 25 marks

Please turn the page


Q2. a) The water is flowing through a pipe having diameters 25cm and 15cm at

sections 1 and 2 respectively. The rate of flow through pipe is 40

litres/sec. The section 1 is 6m above datum and section 2 is 4m above

datum. If the pressure at section 1 is 40.56N/cm2 and assuming the fluid

as ideal determine the following:

i. The intensity of pressure at section 2. (7 marks)

ii. Differentiate between real and ideal flow (2 marks)

iii. Express Bernoulli’s Equation for ideal fluid and real fluid.

(3 marks)

Figure Q2a. Line diagram of the flow system

b) A 30cm diameter pipe carries water under a head of 20metres with a

velocity of 3.5m/s as shown in Figure 2b. 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 Q2b. Diagrammatic representation of 45o bends


Total 25 marks

Please turn the page Q3. a) A fluid system contained in a piston and cylinder machine, passes

through a complete cycle of four processes.Net heat transferred during

a cycle is given as -340kJ.The system completes 200 cycles per min.

Complete the following Table Q3.a showing the method for each item

and compute the net rate of work output in kW. (15 marks)

Table Q3.a Heat, Work and internal energy transfer for a cycle

b) A reactor’s wall 320mm thick is made up of an inner layer of fire brick (k=

0.84W/moC) covered with a layer of insulation (k=0.16 W/m oC). The

reactor operates at a temperature of 1325oC and the ambient

temperature is 25oC as shown in Figure Q3.b.

i. Determine the thickness of fire brick and insulation which gives

minimum heat loss. (5 marks)

ii. Calculate the heat loss presuming that the insulating material

has a maximum temperature of 1200 oC. (5 marks)

Figure Q3.b Reactor’s wall

Total 25 marks



PART B

Q4 a ) For the spring damper and mass system shown in Figure Q4. (a), where

M1 = 2 Kg, K1 = 4 N/m, B1 = 5 Ns/m K3 =5N/m M2 = 3 Kg, K2 = 1 N/m, B2 = 6 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).

(10 marks)

Q4 continued over the page

B1

K1

X1

K2

M2

M1

X2

F(t)

B2

K3



Q4 continued.

c) Hydraulic actuator shown in Figure Q4.c controls the large displacement

power at the shaft of main piston having an area A(m2). The input power

requirement is provided by the displacement ‘x’, of the valve piston. The

linear motion of the valve piston controls the flow of oil to either side of the

main piston. Derive the transfer function of the hydraulic actuator. Assume

oil to be incompressible and neglect the leakage.

Given P1 = Pressure on the left side of the main piston (N/m2)

P2 = Pressure on the right side of the main piston (N/m2)

q = oil flow in m3/sec

y= output displacement (m)

t =time (sec)

Figure Q4.c Hydraulic actuator system

(11 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). Evaluate the time response characteristics of the system.

Figure Q5. (a) Thermostatically controlled air-conditioning system

(10 marks)

(b) Analyse the stability analysis of system for control systems based on

location of roots of characteristic equation in S plane. (6 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.

(4 marks)

ii) What will be the steady state errors for different K values when it is

an closed loop system.

(4 marks)


iii) Comment on the significance of increasing the value of K.

(1 marks)

Total 25 marks


Q6 a) 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

])10([

)(Tsss

KsG

Using Routh-Hurwitz stability criterion analyse the stability of the system. and determine the relation between K and T.

(8 marks)

b) Reduce the following block diagram for an air traffic control systems shown

in Figure Q6. (b) and determine the system transfer function.

Figure Q6. (b) Block diagram for an air traffic control systems

(10 marks)


(c) Evaluate and justify the selection of specific sensors and actuators that can

be employed in boiler automation system for continuous monitoring of

temperature, pressure and water level.

(7 marks)

Total 25 marks

END OF QUESTIONS

Please turn page for 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 =

Formula sheet continues over page

Please turn the page Formula sheet continued.

Thermodynamics

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


Formula sheet continues over page

Please turn the page Formula sheet continued. Block Diagram Reduction

Blocks with feedback loop

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[[lim0

ssGse ios

ss

(For the open-loop system)

)]()(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

END OF PAPER

university of bolton western international college … · 2019-07-26 · page 6 of 12 university of...

Documents