Fluid Mechanics and Machinery - I Cycle Test Answer Key

Article from the Hindu about Ambassador

"Article from the Hindu about Ambassador"

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Muthuganesh

Final Year- Automobile Engineering

The Ambassador had seemed immune to technological developments in the automobile industry. Recent media coverage showed a sad picture of workers laid off following the closure of the Ambassador, or Amby for short, which ruled the Indian roads for nearly half a century, has closed shop. According to the dictionary, an ‘icon’ is a person or a thing worthy of veneration. But did the Ambassador fit the bill? 

Many nostalgic accounts have appeared in the media ruing the demise of the Ambassador, which was one of the most visible symbols of the first 60 years of independent India. Most of these accounts are from the inside, from those who grew up travelling in it with romantic notions of the vehicle, ruing its ultimate death. Or from those who have enough money to splurge on a brand-new heritage vehicle. Perhaps, no one thought of asking these workers what they felt and why they are in the situation they are now. 

I was one of those who never got into a car until much later in life. I grew up travelling by foot, cycle or bus. To me, the Ambassador was a symbol of raw power that was visible on the roads when the driver honked at pedestrians, splashed from dirty puddles on rainy days or rushed through red lights without stopping, with a certain arrogance that was probably derived from the status of its occupants. It was, by and large, the chariot of the power-wielders and power-brokers, occasionally with a flag in front announcing their status if there was any doubt about it at all. 

The arrival of the Maruti, a more efficient and compact car, good-looking to boot, was welcomed but with derision by the romantics of the Amby. So, should I rejoice at its demise? I perhaps would, but the faces of the laid-off workers tell another story, which may well have ended differently if the makers had thought differently and put technology to good use in keeping with the times. 

In the automobile industry the world over and now in India too, changes have come thick and fast. Engines have become leaner, fuel- efficient and lighter. From under 10 kilometres a litre, now cars routinely give upwards of 15 km a litre even in the urban jungles. There is increased awareness of the safety of travellers, which has led to the creation of sophisticated crash zones on the body, apart from simple innovations such as seat-belts and air-bags. The engine compartments have become more compact and the driver has a better view of the road. The cars are aerodynamically efficient. The indicators for turning, braking and other such actions have been standard for decades. Night-driving has become easier with a clearer view and better lights. These are essential to the safety of those inside it as well as those outside. 

The Ambassador had seemed immune to technological developments in the industry. The engine and the shape more or less remained the same across the globe in the 1950s. There were superficial changes from Mark I to IV models, but there was little visible technological improvement apart from some chromium plating here and a change in the dash board there. In most of them the turning indicator lights failed after a few months. Even when they worked, they were hardly visible from a distance. The mileage never went beyond 10 km a litre in the best conditions. Seat-belts were introduced after other countries made it a standard feature, and after they were made mandatory here. My workplace has one of these contraptions and I don’t remember the time when it was easy to lower the window glass. The headlights had a mind of their own, it seemed, and pointed to the skies or directly into on-coming traffic. It was a car that was stayed rooted in the 1950s even after the arrival of the new millennium. Sturdy was the buzzword: but that was for the car. The occupants were better off with cleverly placed crash zones to absorb the impact, leaving them safe in case of an accident. Spacious, except for the fact that the curved edges of seats left you sitting in uncomfortable angles. 

To be fair, it was not just the Ambassador that was stuck in the old mould. My father bought a scooter in the 1970s, for which the rear view mirror came as a paid extra-accessory and not as standard though safety dictates that it should be standard equipment. No new technology or feature, if at all, was introduced in any vehicle unless it was required by law. With a protected market and assured profits, no one thought of investing in Research and Development to make these vehicles better, safer and road- worthy. 

This attitude is evident even today when one looks at our autorickshaws that are still stuck in a time warp and whose makers do not see any urgency to change. When all over the world automobile-makers were competing to make better machines, it bypassed the makers of Ambassadors and its compatriots of that era. All this changed, of course, when competition, especially from Maruti in the beginning, showed what is possible. Unable to adapt, caught in a time warp, the icon had become a dinosaur that could not survive. It became a symbol of the status quo that refuses to change for the better. 

What if the makers, assured of profits from the beginning with protected markets, had made efforts to change, become more efficient, and produced vehicles that were not only eye-catching but also functional? We would have probably seen smiling proud faces of workers in Uttarapara.

Fluid Mechanics and Machinery- I Cycle Test Marks

First Cycle Test Portions- Fluid Mechanics and Machinery

       The first cycle test portions for Fluid Mechanics and Machinery is Unit 1 and Unit 2.

Question Paper Pattern:

Part A:

• Consisting of 7 questions each carrying two marks.
• All questions are compulsory.

Part B:

• Consisting of 4 questions each carrying twelve marks.
• Answer any three out of four questions.

Fluid Mechanics: Tutorials - Unit 5

1.         An inward flow reaction turbine has inlet and outlet diameters of 1.2 m and 0.6 m respectively. The breadth at inlet is 0.25 m and at outlet it is 0.35 m. At a speed of rotation of 250 rpm, the relative velocity at entrance is 3.5 m/s and is radial. Calculate (i) the absolute velocity at the entrance and the inclination to the target of the runner (ii) discharge (iii) velocity of flow at outlet. [16.093 m/s; 3.299 m³/s and 5 m/s]

2.      A centrifugal pump impeller whose external and internal diameters are 400 mm and 200 mm respectively is running at 950 rpm. The rate of flow through the pump is 0.035 m³/s. The suction and the delivery heads are 5 m and 25 m respectively. The diameters of suction and delivery pipes are 120 mm and 80 mm respectively. If the outlet vane angle is 45̊, the flow velocity is constant and equal to 1.8 m/s and power required to drive the pump is 15 KW, Find the (i) Inlet vane angle (ii) η_o(iii) η_max. [10.26̊, 61.76, 73.65]

3.         A Francis turbine has to be designed to develop 367.5 KW under a head of 70m while running at N= 750 rpm. Ratio of width of runner to diameter of runner is 0.1; inner diameter is half the outer diameter. Flow ratio is 0.15, hydraulic efficiency is 95% and mechanical efficiency is 84%. Flow velocity is constant and discharge is radial at exit. Calculate (i) diameter of wheel (ii) discharge (iii) guide vane angle (iv) runner vane angles at inlet and outlet.

4.         The following data pertains to a Kaplan Turbine,

            Power available at shaft  =          8850 KW

            Net available head           =          5.5 m

            Speed ratio                       =          2.1

    Flow ratio                        =          0.67

    Overall efficiency            =          85%

Assuming hub diameter of the wheel is 0.35 times the outside diameter, determine (i) Runner diameter (iii) Runner speed. [6.34m, 65.7 rpm]

Fluid Mechanics: Tutorials - Unit 4

1.         A single acting reciprocating pump has a 15 cm piston with a crank radius 15 cm. The delivery pipe is 10 cm diameter. At a speed of 60 rpm, 310 lps of water is lifted to a total height of 15 cm. Find the slip, co-efficient of discharge and theoretical power in KW required to drive the pump.

2.         A single acting reciprocating pump has the following data

            Cylinder diameter                   =          10 cm

            Stroke                                      =          25 cm

            Static suction head                  =          4 m

            Diameter of suction pipe         =          5 cm

            Suction pipe length                 =          6 m

            Crank speed                            =          30 rpm

            Delivery pipe diameter            =          5 cm

            Length of the delivery pipe    =          25 m

            Static delivery head                =          16 m

Estimate the pressure head on the piston at (i) beginning, (ii) mid and (iii) end of the suction and delivery strokes. Assume Patm = 10 m of water and f=0.02. [2.982, 5.698, 9.018]; [28.576, 17.258, 3.424]

3.         A single acting reciprocating pump has a 20 cm piston with a crank of radius of 40 cm. The delivery pipe is 10 cm diameter and 45 m long. Water is lifted to a height of 40 m above the axis of the cylinder. Find the maximum speed at which the pump can be run without cavitation. Assume atmospheric pressure = 9.75 m water (abs) and cavitation occurs at 2.75 m water (abs). [24.17 rpm]

4.        A centrifugal pump impeller has an outer diameter of 30 cm and an inner diameter of 15 cm. the pump runs at 1200 rpm. The impeller vanes are set back at an angle of 30̊at the outlet. If the velocity of flow constant at 2.0 m/s, calculate
        (i) The velocity and direction of the water at outlet [15.51 m/s]

(ii) The head developed if η_mano is 0.85 [25.13]

(iii) The blade inlet angle [11.98]

Fluid Mechanics: Tutorials - Unit 3

1.         In 1:30 model of spillway, the velocity and discharge are 1.5 m/s and 2 m³/s. Find the corresponding velocity and discharge in the prototype. [8.2 m/s and 9859 m³/s]

2.         An oil of specific gravity 0.9 and viscosity 0.03 poise is to be transported at the rate of 3000 lps through a 1.5 m diameter pipe. Tests were conducted on a 15 cm diameter pipe using water at 20̊C. If the viscosity of the water at 20̊c is 0.01 poise, Find,

(i) Velocity of flow in the model        [5.09 m/s]

(ii) Rate of flow in the model             [80.9 lps]

3.         In an aeroplane model of size 1/40 of its prototype, the pressure drop is 7.5 KN/m². The model is tested in water. Find the corresponding pressure drop in the prototype. Take ρ_air= 1.24 kg/m³; ρ_water = 1000 kg/m³; µ _air= 0.00018 poise; µ _water = 0.01 poise  [(Δp) _p= 1.225 N/m²]

4.         The resistance force F of a ship is a function of its length L, velocity V, acceleration due to gravity g and fluid properties like density ρ and viscosity µ. Write this relationship in a dimensionless form. F/ρV²L² = ϕ (Fr, Re)

5.         The discharge Q over a small rectangular weir is known to depend upon the head H, weir height P, gravity g, Width of the weir L and fluid properties density ρ, dynamic viscosity µ and surface tension σ. Express the relationship between the variables in dimensionless form

Q/ g ^½ H ^5/2 = fn [P/H, L/H, µ/ H^3/2 g^1/2ρ³, σ/ ρgH²]

6.         The resistance force F of a ship is a function of its length L, velocity V, acceleration due to gravity g and the fluid properties like density ρ, viscosity µ. Prove that F/ρV²L² = ϕ (Fr, Re)

7.         Oil of density 917 kg/m³ and dynamic viscosity 0.29 PaS flows in a pipe of diameter 15 cm at a velocity of 2 m/s. What would be the velocity of flow of water in a 1 cm diameter pipe to make the two flows similar? Take ρ_water = 998 kg/m³ and µ _water = 1.31 x 10^-3PaS.

Fluid Mechanics: Tutorials - Unit 2

1. An oil of 8 Poise and specific gravity 0.9 is flowing through a horizontal pipe of 50 mm diameter. If the pressure drop in 100 m length of the pipe is 2000 KN/m², determine (i) Rate of flow of oil (ii) Center line velocity (iii) Total frictional drag over 100 m length of pipe (iv) Power required to maintain the flow (v) Velocity gradient at the pipe wall (vi) Velocity and shear stress at 10 mm from the wall.

[3.83 x 10^-3 m³/s; 3.9 m/s; 3.93 KN; 7.65 KW; 312 S^-1; 2.5 m/s; 150 N/m²]

2. An oil of viscosity 1 Poise and relative density 0.9 is flowing through a circular pipe of diameter 50 mm and 300 mm length, the rate of flow of liquid is 0.0035 m³/s. Find the pressure drop and shear stress at the wall. [684.3 KN/m²; 28.5 N/m²]

3. In a pipe of 300 mm diameter and 800 m length, an oil of specific gravity 0.8 is flowing at the rate of 0.45 m³/s. Find the head lost due to friction and power required to maintain the flow. Take kinematic viscosity of oil as 0.3 x 10^-4 m²/s. [109.72 m; 387.48 KW]

4. A horizontal pipe 150 mm in diameter is joined by sudden enlargement to a 225 mm diameter pipe. Water is flowing through it at the rate of 0.05 m³/s. Find (i) Loss of head due to sudden expansion (ii) Pressure differences in two pipes (iii) Change in pressure if the change is gradual without any loss. [0.1256 m; 0.202 m; 0.327 m] {Note: Power lost due to expansion}

5. A horizontal pipe carries water at the rate of 0.04 m³/s. Its diameter which is 300 mm reduces abruptly to 150 mm. Calculate the pressure loss across the contraction. Take the co-efficient of contraction as 0.62. [3.35 KN/m²]

6. Two reservoirs with a difference in water surface elevation of 10 m are connected by a pipeline ABC which consists of two pipes AB and BC joined in series. Pipe AB is 10 cm in diameter, 20 m long and has a value of f= 0.02. Pipe BC is of 16 cm diameter, 25 m long and f= 0.018. The junctions with the reservoirs and between the pipes are abrupt. Find (i) Discharge including all losses (ii) Discharge neglecting minor losses (iii) What difference in reservoir elevation is necessary to have a discharge of 15L/S, if all losses are included? [43.8 L/S; 1.171 m]

7. Three pipes are connected in parallel between two reservoirs A and B. The details of the pipes are

Pipe	Diameter (cm)	Length (m)	f
1	10	1000	0.022
2	15	800	0.018
3	12	950	0.020

If the difference in the water level elevations of the two reservoirs is 12 m; estimate the discharge in each pipe. [0.0081; 0.0277; 0.0138 m³/s]

8. Pipeline carrying water has a diameter of 0.5 m and is 2 km long. To increase the delivery another pipeline of same diameter is introduced parallel to the first pipe in the second half of its length. Find the increase in discharge if the total head loss in both the cases is 15 m. Assume f= 0.02 for all the pipes. [0.3766m³/s; 0.4763m³/s; 26.48%]

9. A compound piping system consists of 1800 m of 50 cm, 1200 m of 40 cm and 600 m of 30 cm diameter pipes of the same material connected in series. (i) What is the equivalent length of a 40 cm pipe of the same material? (ii) What is the equivalent size of the pipe 3600 m long? (iii) If the three pipes are in parallel, what is the equivalent length of a 50 cm pipe? [4318.22 m; 38.57 cm; 377.34 m]

10. A horizontal pipe 40 m long is connected to water tank at one end and discharge freely into atmosphere at the other end. For the first 25 m of its length from the tank, the pipe is 150 mm diameter and it’s suddenly enlarged to 300 mm. The height of the water level in the tank is 8 m above the centre of the pipe. Including all losses find (i) Q, (ii) HEL, TEL f=0.01

Fluid Mechanics: Tutorials - Unit 1

1. One litre of crude oil weighs 9.6N. Calculate its specific weight, density and specific gravity.

2. Calculate the density, specific weight and weight of two litres of a liquid of specific gravity 0.764 [764 kg/m³, 7494.84 N/m³, 15 N]

3. A plate 0.025 mm distant from a fixed plate moves at 50 cm/s and requires a force of 1.471 N/m² to maintain this speed. Determine the fluid viscosity between the plates. [7.355 X 10^-5 Pas]                                                                

4. Find the kinematic viscosity of an oil having density 980 kg/m³ when at a certain point in the oil, the shear stress is 0.25 N/m² and velocity gradient 0.3 m/s. [ 8.5 X 10^-4 m²/s]

5. An oil film of thickness 1.5 mm is used for lubrication between a square plate of size 0.9 m X 0.9 m and an inclined plane having an angle of inclination 20^o. The weight of the plate is 392.4 N and it slides down the plane with the uniform velocity of 0.2 m/s. Find the dynamic viscosity of the oil. [1.24 Pa.s]

6. An oil of viscosity 5 poise is used for lubrication between a shaft and sleeve. The diameter of shaft is 0.5 m and it rotates at 200 rpm. Calculate the power lost in the oil for a sleeve length of 100 mm. The thickness of the oil film is 1 mm. [2.15 kW]

7. Find the change in volume of 1 m³ of water when subjected to a pressure increase of 2 MN/ m². The bulk modulus of elasticity of water is 2.24 X 10 ⁹ N/m². [0.89 X 10 ^-3m³]

8. From the following data, determine the bulk modulus of elasticity of water at 3.5 MN/ m², the volume was 1 m³ and at 24 MN/ m², the volume was 0.990 m³. [2.05 X 10 ⁹ N/ m²]

9. An atomizer forms water droplets with a diameter of 5 X 10^-5 m, what is the pressure within the droplets at 20 ^oC, if the pressure outside the droplets is 101 kN/m². Assume the surface tension of water at 20⁰C as 0.0718 N/m. [106.74 kN/m²]

10. By how much does the pressure in a cylindrical jet of water 4 mm in diameter exceed the pressure of the surrounding atmosphere if the surface tension of the water is 0.0718 N/m. [35.9 N/m²]

11. A shaft 80 mm in diameter is being pushed through a bearing sleeve 80.2 mm in diameter and 0.3 m long. The clearance assumed the uniform, is flooded with lubricating oil of viscosity 0.1 kg/ms and specific gravity 0.9.

a)      If the shaft moves axially at 0.8 m/s, estimate the resistance force exerted by the oil and the shaft.

b)      If the shaft is axially fixed and rotated at 1800 rpm, estimate the resisting torque exerted by the oil and the power required to rotate the shaft.     

      [60.32 N, 22.74 Nm, 4.29 kW]

12. A 30 cm diameter pipe carries oil of specific gravity 0.8 at a velocity of 2 m/s. At another section the diameter is 20 cm. Find the velocity at this section and also mass rate of flow of oil. [4.5 m/s, 113 kg/s]

13. A 40 cm diameter pipe, conveying water, branches into two pipes of diameters 30 cm and 20 cm respectively. If the average velocity in the 40 cm diameter is 3 m/s, find the discharge in the pipe. Also determine the velocity in 20 cm pipe if the average velocity in 30 cm diameter pipe is 2 m/s. [0.3769 m³/s, 7.5 m/s]

14. At point A in a pipe line carrying water, the diameter is 1 m, the pressure is 98 kPa and then velocity is 1 m/s. At point B, 2 m higher than A, the diameter is 0.5 m and the pressure is 20 kPa. Determine the direction of the flow. [A to B]

15. The capillary rise in the glass tube used for measuring water level is not to exceed 0.5 mm. Determine its minimum size given that surface tension for water in contact with air is 0.07112 N/m. [5.8 cm]

16. The water is flowing through a taper pipe of length 50 m having diameters 40 cm at the upper end and 20 cm at the lower end at the rate of 60 lps. The pipe has a slope of 1 in 40. Find the pressure at the higher level is 24.525 N/cm². [25.58 N/cm²]

17. A pipe of diameter 30 cm carries water at a velocity of 20 cm/s. The pressure at points A and B are given as 34.335 N/cm² and 29.43 N/cm² respectively, while the datum head at A and B are 25 m and 28 m. Find   the loss of head between A and B. [2 m]

18. A nozzle of diameter 30 mm is filled to a pipe of 60 mm diameter. Find the force exerted by the nozzle on the water which is flowing through the pipe at the rate of 4 m³/min. [7057.7 N]

19. A 45⁰ reducing pipe bend in a horizontal plane tapers from 600 mm diameter at the inlet to 300 mm diameter at the outlet. The pressure at the inlet is 140 kPa and the rate of flow of water through the bend is 0.425 m³/s. calculate the net resultant horizontal force exerted by the water on the bend. [33.23 kN]

20. Fig.1 shows an unsymmetrical sprinkler. It has a frictionless shaft and equal flow through each nozzle with a velocity of 8 m/s relative to nozzle. Find the speed of rotation in rpm. [29.4 rpm]

Fluid Mechanics Assignment: 1; Due date: 08/08/2014

1. Prove that h= h_f1 = h_f2 = h_f3….. for pipes connected in parallel.

Fluid Mechanics Quiz: 2; Date: 08/08/2014

1. What is energy displacement thickness?
2. How shear stress varies when a fluid flow through a pipeline?
3. Uses of Hagen-Poiseuille’s equation.
4. What is the critical Reynolds number?
5. Difference between the smooth pipe and rough pipe.
6. What is hydraulic diameter?
7. Give an example for pipes in Parallel?
8. What happens to friction factor at very high Reynold’s number?
9. What is Blasius equation?
10. What is vena-contracta?
11. Oil of viscosity µ is placed between two plates. The plates are moved in same direction with velocity V. Sketch the velocity profile between the plates.
12. During sudden contraction, locate the region where the loss will occur.
13. A piping system involves two pipes of different diameter pipes. Both pipes are having the same length; same materials are connected in parallel. How will you compare the flow rate and pressure drops?

Fluid Mechanics Quiz: 1; Date: 17/07/2014

1. What is Non-Newtonian fluid?
2. Example for the phenomena for capillarity.
3. What is cavitation?
4. Give examples for the liquid jet?
5. Define capillary tube?
6. What are the two forms of Bernoulli’s equation?
7. What is head?
8. What is the difference between the Euler’s and Bernoulli’s equation?
9. What is continuity equation?
10. What is Newton’s law of viscosity?

Four Stroke Engine Working Cycle

Exploded view of an engine