Tutorial letter 101/0/2016

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1 Tutorial letter 101/0/2016 Hydraulic Machines III (Theory) FMA3602 Year Module Department of Mechanical and Industrial Engineering IMPORTANT INFORMATION: This tutorial letter contains important information about your module.

2 CONTENTS 1 INTRODUCTION PURPOSE OF AND OUTCOMES FOR THE MODULE Purpose Outcomes Lecturer and contact details Lecturer: Department University MODULE RELATED RESOURCES Prescribed books Recommended books Electronic Reserves (e-reserves) Student support services for the module Module specific study plan Module practical work and work integrated learning Assessment Assessment plan General assignment numbers Unique assignment numbers Due dates of assignments Submission of assignments ASSIGNMENTS Examinations Other assessment method Frequently asked questions Sources Consulted Conclusions

3 1 INTRODUCTION Dear Student Welcome to the module FMA3602, offered by the Department of Mechanical and Industrial Engineering in the School of Engineering at Unisa. This tutorial letter provides you with an overview and specific information about this module. Use it as a guideline to approaching your studies. This tutorial letter also provides you with general administrative information as well as specific information about the subject. The drawing example and checklist (rubric, annexure A in the workbook) provide a pattern which should enable you to complete Assignment 02 satisfactorily. They have been included to help you to achieve the standard of drawing and level of skill required of you in both the assignment and the examination. Read this tutorial letter carefully and keep it safe for future reference. Some of this tutorial matter may not be available when you register. Tutorial matter that is not available when you register will be posted to you as soon as possible, but is also available on myunisa. We hope that you will enjoy this course. 2 PURPOSE OF AND OUTCOMES FOR THE MODULE 2.1 Purpose The skills, values and knowledge reflected in this module are required by people in the field of Hydraulic Turbines and Pumps Engineering 2.2 Outcomes Do Various Calculations concerning Pelton, Francis, Kaplan Turbines, centrifugal pumps, fans and fan systems and positive displacement pumps 3 LECTURER AND CONTACT DETAILS 3.1 Lecturer: Your Lecturer is Mr.TJ Mutheiwana Tel: muthetj@unisa.ac.za 3.2 Department You may contact the Department of Mechanical and Industrial Engineering by post, , telephone, or online though myunisa. Please refer to the booklet my Unisa. 3

4 Departmental address: Department of Mechanical and Industrial Engineering Unisa (Florida campus) Private Bag X6 Florida 1710 Phone: Use the general address: Find our department on the internet at the following address: Always state your STUDENT NUMBER and the module code (FMA3602) in all correspondence and enquiries. Whenever you contact the Department of Mechanical and Industrial Engineering, ensure that soon after your greeting you state the module code of the module you are registered for. This will help the person you are speaking to to assist you more efficiently. 3.3 University Contact addresses of the various administrative departments and details of their specialist functions are included in the booklet entitled my Unisa, which you received with your study package. This booklet explains that certain departments and the lecturers are responsible for academic questions only. Because Unisa has so many students and offers distance education, many other departments are necessary to deal with administrative questions, assignments, examinations, funding, library books and careers. As a student, you need to be able to scan documents for information. Study the contents page of my Unisa and mark important information to which you may need to refer regularly, such as the telephone number of your closest regional office. 4 MODULE RELATED RESOURCES 4.1 Prescribed books Applications of Fluid Mechanics Part 2 by C.F Meyer ISBN

5 4.2 Recommended books Turbomachinery Design and Theory by Rama S.R. Gorla, Aijaz A.Khan The book can be downloaded on the internet for free and It is also uploaded on my unisa under additional resources. (Chapter 2 and 3) 4.3 Electronic Reserves (e-reserves) All course material is available on myunisa at under the module code. Discussion forums may be are set up by your lecturer on for discussions with your peers. Additional electronic resources are available from the library site (via DO NOT ASSIGNMENTS TO YOUR LECTURERS. DO NOT FAX ASSIGNMENTS. DO NOT SUBMIT PARTIALY COMPLETED ASSIGNMENTS. SUBMIT ONLY COMPLETE, ORIGINAL ASSIGNMENTS AND KEEP COPIES 5 STUDENT SUPPORT SERVICES FOR THE MODULE All course material is available on myunisa at under the module code. Discussion forums may be are set up by your lecturer on for discussions with your peers. Additional electronic resources are available from the library site (via DO NOT ASSIGNMENTS TO YOUR LECTURERS. DO NOT FAX ASSIGNMENTS. DO NOT SUBMIT PARTIALY COMPLETED ASSIGNMENTS. SUBMIT ONLY COMPLETE, ORIGINAL ASSIGNMENTS AND KEEP COPIES Important information appears in your my Unisa brochure. 6 MODULE SPECIFIC STUDY PLAN Use your my Unisa brochure for general time management and planning skills. 7 MODULE PRACTICAL WORK AND WORK INTEGRATED LEARNING The practical Module for this module is FMAPRB3 8 ASSESSMENT 8.1 Assessment plan 5

6 Two assignments which contributes 20% of the final mark and a final examination which contributes 80% of the final mark 8.2 General assignment numbers Assignments are numbered consecutively per module, starting from Unique assignment numbers Assignment 1 : Assignment 2 : Due dates of assignments Assignment 01 (compulsory) 31 May 2016 Assignment 02 ( compulsory) 31 August 2016 Please note that the due dates for the assignment are those in your tutorial letter and not those on myunisa. If you miss these deadlines your assignment will not be marked. 8.3 Submission of assignments To gain examination admission, it is compulsory to submit to obtain a minimum of 40% for both assignments No late assignment submissions will be accepted. Keep a clear copy of all the assignments for your own reference. This is important, as assignments do get lost. Submissions of all assignments must be in accordance with the booklet my Unisa. It is your responsibility to check whether Unisa has received your assignment by contacting the Assignment Department two weeks after you have submitted and asking whether the university has received and recorded your assignment. Do not contact your lecturer! If you have not received stationery such as assignment covers, bar code stickers and envelopes, do not contact your lecturer. Contact the assignment department. 6

7 You may submit an assignment even if you have not received any stationery. Use an ordinary A4 envelope and fold your A3 drawing. Non-receipt of stationery will not be considered a reason to obtain an extension for the submission of your assignment. 8.4 ASSIGNMENTS ASSIGNMENT1 (COMPULSORY) DUE DATE: 31 MAY 2016 UNIQUE NUMBER: A radial flow hydraulic turbine is required to be designed to produce 30MW under a head of 14m at a speed of 95 rpm. A geometrically similar model with an output of 40 kw and a head of 5m is to be tested under dynamically similar conditions. At what speed must the model be run, what is the required impeller diameter ratio between the model and the prototype and what is the volume flow rate through the model if its efficiency can be assumed to be 90 per cent? 2. A pump with an available driven speed of 800 rpm is required to overcome a 1.83m head while pumping 0.2m 3 /s. What type of pump is required and what power is required? 3. The inner and outer diameters of an axial flow pump are 0.75 and 1.8m respectively. Fixed stator blades lie downstream of the rotor with an inlet angle of 40 o (at the mean diameter) measured from the direction of blade motion. The rotor blade outlet angle (at mean diameter) also measured from the direction of blade motion 30 o and the rotor rotates at a speed of 250rpm. If the wheel velocity upstream from the rotor is zero at all radii, determine a. The axial velocity if the flow onto the stator blade occurs at zero incidences, b. The rotor torque if the axial velocity is constant across the flow annulus and the c. Root and tip rotor blade angles for zero incidences and zero inlet whirl. 4. When a laboratory test was carried out on a pump, it was found that for a pump total head of 36m at a discharge of 0.05m 3 /s cavitation began when the sum of the static pressure plus velocity head at inlet was reduced to 3.5m.The atmospheric was 760mmHg and the vapour pressure of water 1.8kpa.If the pump is to operate at a location where atmospheric pressure is reduced to 620 mmhg and the vapour pressure of water is 830 Pa, what is the value of the cavitation parameter when the pump develops the same total head and discharges? Is it necessary to reduce the height of the pump above the supply, and if so by how much? 5. A generator is to be driven by a small Pelton wheel with a head of 91.5m at inlet to the nozzle and discharge of 0.04m 3 /s. The wheel rotates at 720rpm and the velocity coefficient of the nozzle is If the efficiency of the wheel (based on the energy available at entry to the nozzle) is 80 per cent and the ratio of bucket speed to jet speed is 0.46, determine the wheel to jet diameter ratio at the centre-line of the buckets, and the speed of the wheel. What is the dimensionless power specific speed of the wheel? 6. A reservoir with a height of 280m is connected to the powerhouse of a hydroelectric plant through three pipes each 2.5km long and with a friction factor 0.006, in which the head loss is not to exceed 34m.It is a 7

8 requirement that a total shaft output of 18MW be developed, and to achieve this it is decided to install a number of single jet Pelton wheels, each with a dimensionless specific speed not exceeding 0.23rad. The ratio of bucket speed to jet speed is 0.46, while the wheel speed is to be 650rpm.If the nozzles have a discharge coefficient of 0.94 and velocity coefficient of 0.96, and assuming that each wheel has an overall efficiency of 87 per cent, find a. The number of Pelton wheels required, b. The wheel diameter c. The jet nozzle diameter and d. The diameter of the supply pipes. 7. The buckets of a Pelton wheel deflect the jet through an angle of 170 o, while the relative velocity of the water is reduced by 12 per cent due to bucket friction. Calculate the theoretical hydraulic efficiency from the velocity triangles for a bucket/jet speed ratio of 0.47.Under a gross head of 600m the wheel develops 1250kW when the loss of head due to pipe friction between the reservoir and nozzle is 48m. The bucket circle diameter of the wheel is 900mm and there are two jets. The nozzle velocity coefficient is Find the speed of rotation of the wheel and the diameter of the nozzles if the actual hydraulic efficiency 0.9 times that calculated above. 8. An inward flow radial turbine has an overall efficiency of 74 per cent. The net head H across the turbine is 5.5m and the required power output is 125kW. The runner tangential velocity is 0.97(2gH) 1/2 while the flow velocity is 0.4(2gH) 1/2.If the speed of the runner is 230rpm with hydraulic losses accounting for 18 per cent of the energy available, calculate the inlet guide vane exit angle,the inlet angle of the runner vane,the runner diameter at inlet and the height of the runner at inlet, Assume that the discharge is radial. 9. A Francis turbine has a diameter of 1.4m and rotates at 430 rpm. Water enters the runner without shock with a flow velocity (Cr 1 ) of 9.5m/s and leaves the runner without whirl with an absolute velocity of 7m/s. The difference between the sum of the static and potential heads at entrance to the runner and the exit from the runner is 62m. If the turbine develops 12250kW and has a flow rate of 12m 3 /s of water when the net head is 115m, find a. The absolute velocity of the water at entry to the runner and the angle of the inlet guide vanes, b. The entry angle of the runner blades and the head lost in the runner 10. An inward flow vertical shaft reaction turbine runs at a speed of 375rpm under an available net total head from inlet flange to tail race of 62m.The external diameter of the runner is 1.5m and the dimensionless power specific speed based on the power transferred to the runner is 0.14rev.Water inters the runner without shock with a flow velocity of 9m/s and leaves the runner without whirl with an absolute velocity of 7m/s. It discharges to the tailrace with a velocity of 2m/s. The mean height of the runner entry plane is 2m above the tail race level while the entrance to the draft tube is 1.7m above the tail race. At entrance to the 8

9 runner the static pressure head is 35m above atmospheric pressure, while at exit from the runner the static pressure head is 2.2m below atmospheric pressure. Assuming a hydraulic efficiency of 90 per cent find, a. The runner blade entry angle b. The head lost in the volute casing and guide vanes, in the runner and in the draft tube and the draft tube entry diameter. 11. An axial flow hydraulic turbine has a net had of 23m across it, and, when running at a speed of 150rpm, develops 23MW.The blade tip and hub diameters are 4.75 and 2m respectively. If the hydraulic efficiency is 93 per cent and the overall efficiency is 85 per cent, calculate the inlet and outlet blade angles at mean radius assuming axial flow at outlet. 12. A Kaplan turbine operating under a net head of 20m develops 16000kW with an overall efficiency of 80 per cent. The diameter of the runner is 4.2m while the hub diameter is 2m and the dimensionless power specific speed is 3 rad. If the hydraulic efficiency is 90 per cent, calculate the inlet and exit angles of the runner blades at the tip and the hub if the flow leaving the runner is purely axial. 13. An axial flow turbine with tip and hub diameters of 2 and 8m respectively rotates at 250rpm. The turbine is fitted with fixed stator blades upstream of the rotor and at the mean diameter these are set at 42 o to the direction of blade rotation. Also, at the mean diameter and measured from the direction of blade rotation, the blade angle at inlet is 148 o. Assuming a constant axial velocity across the annulus, what is the flow rate for which the angle of incidence of the rotor blades is zero? ASSIGNMENT 2 DUE DATE: 31 AUGUST 2016 UNIQUE NUMBER: A large centrifugal pump contains liquid whose kinematic viscosity may vary between 3 and 6 times that of water. The dimensionless specific speed of the pump is rev and it is to discharge 2m 3 /s of liquid against a total head of 15m. Determine the range of speed and test heads for a one quarter scale model investigation of the full size pump if the model uses water. 2. A centrifugal pump of 1.3m diameter delivers 3.5m 3 /min of water at a tip speed of 10m/s and a flow velocity of 1.6m/s. The outlet blade angle is at 30 o to the tangent at the impeller periphery. Assuming zero whirl at inlet and zero slip calculate the torque delivered by the impeller. 3. The impeller of a centrifugal pump has backward facing blades inclined at 30 o to the tangent at impeller outlet. The blades are 20mm in depth at the outlet, the impeller is 250mm in diameter and it rotates at 1450rpm. The flow rate through the pump is 0.028m 3 /s and a slip factor of 0.77 may be assumed. Determine the theoretical head developed by the impeller, and the number of impeller blades. 4. An impeller with an eye radius of 51 mm and an outside diameter of 406mm rotates at 900 rpm. The inlet and outlet blade angles measured from the radial flow direction are 75 o and 83 o respectively, while the blade depth is 64mm. assuming zero inlet whirl, zero slip and a hydraulic efficiency of 89 per cent, calculate a. The volume flow rate through the impeller, 9

10 b. The stagnation and static pressure rise across the impeller c. The power transferred to the fluid and d. The input power to the impeller 5. The basic design of a centrifugal pump has a dimensionless specific speed of rev. The blades are forward facing on the impeller and the outlet angle is 120 o to the tangent, with an impeller passage width at outlet equal to one tenth of the diameter. The pump is to be used to pump water at a vertical distance of 35m at a flow rate of 0.04m 3 /s. The suction and delivery pipes are each of 150mm diameters and have a combined length of 40m with a friction factor of Other losses at pipe entry, exit, bends, etc. are three times the velocity head in the pipes. If the blades occupy 6 per cent of the circumferential area and a hydraulic efficiency (neglecting slip) is 76 per cent, what must be the diameter of the pump impeller? 6. A hydraulic turbine is designed to run at 300rpm under a net head of 50m and to produce 2MW of power. The runner outlet velocity of the fluid is expected to be 10.4m/s and it is proposed to situate the runner outlet at height of 6m above the tail race. The atmospheric pressure is equivalent to 10.3m of water and the saturation pressure of water is 4kPa.Determine whether a. cavitation is likely to occur, b c The limiting height of the runner outlet if cavitation is to be just avoided and the head loss between runner outlet and tailrace when cavitation is just about to occur. Critical cavitation parameters are given below Ns(rev) σ A twelve bladed axial flow fan has a hydraulic efficiency of 0.92, a mean radius of 0.93m and rotates at 450rpm.Air enters the blades axially at a speed of 40m/s and the head developed across the blades is 35m of air. If the chord length at mean radius is 0.33, find the blade angles at inlet and outlet if the blades may be considered to act as isolated aerofoils. If the blades are aerofoils with the following characteristics, find also the angle of incidence of the blades and the blade stagger angle. All calculations are to be carried out at mean radius. Angle of incidence(deg) Lift coefficient A centrifugal pump is used to pump water from a low to high reservoir having a water level difference of 32m. The total length of pipe is 1000m with a friction factor of and its diameter is 200mm.Neglecting all losses except friction, determine the rate of flow between the reservoirs and the power required to drive the pump. The characteristics of the pump are as follows. 10

11 Q(m3/h) H(m) Η(%) FMA3602/101/0/ The characteristics of a 0.7m diameter centrifugal pump impeller running at 750 rpm are as follows Q(m3/min) H(m) Η(%) a. If the pump is initially used to transfer water from one reservoir to another at the same level, determine the pump operating point if the head lost to frictional and other resistances is 35m at 25m 3 /min b. The pump is then used to transfer water between two reservoir having difference in levels of 15m through a pipe of 0.45m diameter. If the pipe is 93m long with a friction factor of and pipe entry and exit loss coefficients of 0.5 and 1.0 respectively, find the volume flow rate and power absorbed. c. If the pump is now changed to one of 0.51m diameter and the motor is changed to one running at 975rpm, what is the new volume flow rate and power absorbed? 9 EXAMINATIONS Use your my Unisa brochure for general examination guidelines and examination preparation guidelines. DIRECT ALL QUERIES RELATED TO EXAMINATIONS TO THE CONTACT CENTRE; ASK FOR THE EXAMINATION DEPARTMENT. DO NOT CONTACT YOUR LECTURER WITH ANY EXAMINATION QUERIES. ENSURE THAT YOU HAVE A VALID EXAMINATION TIMETABLE OR HAVE RECEIVED OFFICIAL CONFIRMATION OF EXAMINATION ADMISSION AND THE DATE OF THE EXAMINATION. EXAMINATION INFORMATION FOR DRW111X Type of examination Examination language Closed-book English Calculators allowed - memories of programmable calculators must be cleared in the presence of the invigilator prior to the start of the examination 11

12 Note: You must carefully study all of the material in the study guide as well as the references in the prescribed book. You can expect examination questions similar to those encountered in the study guide, your assignments and the other questions in the workbook. 10 OTHER ASSESSMENT METHOD No other assessment method. 11 FREQUENTLY ASKED QUESTIONS The my Unisa brochure contains an A-Z guide of the most relevant study information. TABLE 1: SUMMARY OF FREQUENTLY ASKED QUESTIONS AND ANSWERS LOOKING FOR? YOU CAN FIND IT HERE! TAKE NOTE THAT 1 Study material Refer to section 5 of this tutorial letter for a list of all required study material. It is your responsibility to ensure that you have received all Unisa study material listed in this tutorial letter. 2 Prescribed books listed in section 4 3 Recommended books listed in section 4 4 Assignments: How many? When due? Submissions? Has Unisa received my assignments? Where can I find my assignment marks? Section 4 Section 4 See section 8 of this tutorial letter for all the assignment requirements for this registration period. It is your responsibility to obtain the prescribed book(s) from the supplier of your choice, in time to do your assignment(s). It is your responsibility to ensure that you submit your assignments by the dates in section 8. Contact the Ass. Depart. immediately if you have not received all of your study material, as listed in section 6, for study and to complete the assignments. Study required? material Marking? Marks obtained? 5 Examinations: See section 9 of this tutorial letter for all the examination If you have not been contacted by the end of April and 12

13 Where can I find my year mark? When do I write the examination? What are my examination results? requirements for this registration. All enquiries should be directed to the Contact Centre, or consult myunisa. September for semesters 1 and 2 respectively, it is your responsibility to ensure that you obtain your examination dates from the Examination Department. FMA3602/101/0/ SOURCES CONSULTED None 13 CONCLUSIONS Most of the information required for FMA3602 has been covered in this tutorial letter And for any other information regarding the contents of your module, you are more than welcome to contact your lecturer. UNISA

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