代做MMME 2042 Variable Pitch Propeller 2024代做回归

Department of M3

Design, Manufacture and Project

MMME 2042

Project Brief: Variable Pitch Propeller

Project Type: Determinate, Design

PDR Deadline: 25th March 2024

CDR Deadline: Thursday 10th May 2042

This is an individual exercise which involves the design of the mechanical parts of a variable-pitch propeller.

1. Learning Outcomes

After successful completion of this project, students will have the ability to:

· Make sound decisions in design based on an appropriate level of analysis for robustness with considerations of other factors such as performance, cost, efficiency, and environmental impact.

· Choose materials informedly from the available common engineering materials – such as mild steel, cast iron, brass and other copper alloys, aluminium, and its alloys.

· Design with production in mind. By specifying the processes involved in manufacturing a part such as casting, forging, milling, grinding, etc., you will see how to design parts that are economical to manufacture and assemble.

· Understand the importance of Statements of Requirements and Compliance.

· Research and specify standard components such as bearings,

· fasteners, and seals. Using standard parts will reduce the cost and probably improve the device's performance.

· Understand that ‘off-design’ and failure cases can sometimes determine the outcome.

· Understand and manipulate complex mathematical models to predict a range of outcomes.

2. Background

You are a Design Engineer working in a Company which designs and manufactures marine equipment. The Company has a reputation for high-quality, reliable and robust products. The Board of Directors have assigned you to lead a team of engineers to design a new three-bladed variable pitch propeller for the marine industry.

A concept needs to be defined to see if a satisfactory business plan can be produced. A preliminary Statement of Requirements for the propeller has been produced which if satisfied, it is anticipated will meet the potential market requirements and be financially viable. This is a classic case where the Concept and the Requirements will co-evolve.

There is a large market for small displacement pleasure craft and inshore fishing boats. Boat owners can choose which engine, gearbox and propeller is fitted. As this is a single-engine craft, safety, reliability and robustness are paramount, however, unit cost cannot be ignored.

The market-leading engine, gearbox, and control system manufacturers for this class of boat have been chosen for the first application of the new propeller. However, this combination may be fitted to several different boat designs, so no specific boat data are available. There is also the possibility of an electric drive.

A feasibility study is required for a Variable Pitch Propeller capable of meeting the following requirements.

3. Statement of Requirements

1) A generic work boat, see Figure 1, is to be propeller-driven through a nominal 2:1 (2.051 actual) reduction gearbox.

2) To obviate the need to provide a reversing gear and a clutch, the pitch of the propeller blades is to be variable. Thus, by changing the angle of the propeller blades the boat is enabled to move forwards, backwards or remain stationary against a current.

3) The target minimum forward design speed in still water is 10 knots and in reverse 6 knots.

4) The propeller drive shaft is enclosed in a stern tube that extends forward into the boat from the rear of the keel, Figure 2 Drive Layout

5) The propeller is mounted onto a drive shaft supported by two bearings at either end of the stern tube, 500 mm apart. One bearing capable of taking the thrust from the propeller is mounted in the stern-tube at the aft (rear) of the boat and the second bearing is a cylindrical roller bearing mounted at the front. Figure 7 Drive Shaft Arrangement. The detail of the propeller attachment flange is defined in Figure 8 Drive Shaft Flange.

6) The overall diameter of the propeller shall not exceed 500 mm. In the interests of efficiency, the diameter of the hub should be as small as is consistent with providing a reliable working system.

7) As the craft will operate in shallow water there is a significant probability of total fouling of the propeller or just one blade. In the event of total fouling with the throttle fully open, the engine will stall, and the shock torque will reach 150% of its peak value. If one blade is fouled and there is an attempt to vary the pitch the maximum actuation force will be taken by that one blade and its attachment. In either event, no parts, other than the blades, will suffer permanent set or damage.

8) The Company have spent a great deal of time and money developing a blade and the associated manufacturing processes. It has an efficiency of 70%. This blade will be used on a range of propellers, and it is a non-negotiable requirement that it be used on this design, Figure 9 Propeller Blade Forging. The round base will need to be machined to suit the design, but the blade profile must not be changed.

9) It is expected that the forward/reverse selection will be actuated by the throttle so that the craft may be controlled by a single lever, which does not form. part of this design.

10) The pitch control is to be actuated using an existing hydraulic source from a gear pump; the pressure regulating valve is set at 200 bar maximum, Figure 3 Hydraulic Circuit.

11) The maximum angle of attack for the propeller is 30 degrees for forward movement and since the boat is not required to quickly travel 15 degrees in reverse.

12) The force required to activate the propeller is a function of the hydrodynamic and mechanical design of the blades. Experience has shown that the absolute maximum torque of 160 Nm is required at the blade root, in most cases significantly less.

13) The engine chosen for the first application is a four-cylinder 2-litre diesel. The engine parameters are shown in Figure 5 Engine Power Curve and Figure 6 Engine Torque Curve. The Specific Fuel Consumption is 0.264 kg/kWh at maximum power.

14) The propeller has been carefully optimised and excessive speed will lead to significant inefficiency. There is an electronic limiter on the engine which can be adjusted to any speed less than the maximum rating of the engine. This will be used to ensure the propeller shaft speed is limited to 1300 rpm +/-2.5%.

15) Hydraulic fluid is directed to the propeller by two concentric tubes. One for forward pitch and the other for reverse, the choice of which is a design freedom of choice, see Figure 7 Drive Shaft Arrangement. These tubes rotate with the propeller shaft.

16) The oil tubes shown in Figure 7 Drive Shaft Arrangement are incomplete and need to have features added to interface with the actuating mechanism to form. complete welded assemblies, see the features at the other ends as examples.

17) The total transmission system will experience major (zero to max power), minor (random throttle movements) cycle loads and high cycle vibration. These varying loads can be accumulated into ‘equivalent’ major cycles. There is knowledge within the Company that if parts are designed for a minimum life of 10000 0 to max major cycles that provides a satisfactory product.

18) Bearings shall have an L10 Life of 10000 hours.

19) The first whirling speed of the drive shaft shall be at least 120% of the maximum speed. (Consider only the part of the shaft between the bearings, ignore the overhung mass).

20) When operating in shallow water the propeller will stir up mud and sand from the bottom. Reliability is of paramount importance, and it must not be possible for the propeller to be lost nor for the bearings to be damaged by contaminants.

21) The annual production will be 5000 units.

22) The propeller arrangement shall remain water and oil-tight at all conditions; all joints shall have suitable sealing.

23) As the unit is directly in contact with seawater consideration shall be given to the choice of materials and/or corrosion protection.

4. Deliverables

Design the hub, the variable pitch mechanism, and the propeller shaft; install the rear bearing and seals. Investigate the suitability of the standard blade with the hub using Momentum Theory

A short report is required which should contain the following paragraphs:

1. An introduction, 150 words maximum

2. An executive report, max. ONE side of A4 describing the rationale for the chosen design configuration and a rational justification for material selection, and the selection of standard machine elements, such as bearings, seals, and fasteners. Do NOT include CES charts.

3. A clear presentation of all calculations. (This may be in spreadsheet form. if presented in the same way as the given, spreadsheet plus MS Word definition)

4. In a separate sheet answer the following questions:

· What is the final calculated speed of the boat (as opposed to the required speed)?

· What is the percentage difference in area actual/ideal?

· What is the reserve factor for the Ultimate stress on the shaft?

· What is the reserve factor for Fatigue stress on the shaft?

· What torque should be applied to the main flange bolts to ensure they do not fail in fatigue?

· If the Shoulder Pin was not fitted what torque can be applied at the main shaft flange without slippage due to the interface force by the bolts alone?

· What is the first whirl speed of the main shaft and both oil tubes?

· A recommendation (no design) of what could be done, if anything, to prevent whirling of the oil tubes?

· What is the calculated life of the location bearing in hours?

· It may not be possible to achieve the ‘ideal’ area propeller with the constraint of using an existing blade. What power would be required to achieve the desired speed?

5. A General Arrangement drawing of the Variable Pitch Propeller. This should clearly show how the operating mechanism, the rear bearing and the seals are assembled using appropriate sectional views and notes. Specify necessary fits. Show only the Rear Hub and the Propeller assembly, it is NOT necessary to show to whole Drive Shaft arrangement.

6. A Detail drawing of the piston. All necessary dimensions and tolerances so that the part may be costed for manufacture are required. Appropriate design features for selected manufacturing processes need to be carefully considered.

7. The General Arrangement should convey the design intent and rationale so that members of your team can understand your intentions without direct reference.

5. Organisation

The work should be carefully planned and managed on this individual project.

Interaction and discussion with other students within the group are encouraged. However, decisions and judgement for optimised solutions and to production of the outcome should be by individual effort.

Your Design Tutor will be the main contact for advice and consultation. You may wish to discuss options with other Design Tutors as it is common in design projects that different solutions are possible. However, you are advised to discuss with your own Tutor significant differences from that advised as they will be marking your work.

All marks will be reviewed and moderated by the module convenors.

6. Timetable

Week	Date	Bring to Design Session	Work in Design and Feedback Session
24	19 Feb	Individual Project Brief	Project Brief
25	27 Feb	Understand Requirements, morphology chart	Self-study of Project brief and relevant documents.
26	5 Mar	Concept sketches and morphology chart	Discuss questions. Establish design concept, draft morphology chart
27	12 Mar	Embodiment sketch and preliminary calculations	Tutor review of morphology chart and spreadsheet calculations, sketch concept and architecture
28	19 Mar	Draft PDR presentation	Tutor review of concept architecture. Prepare PDR
29	25 Mar	23:59 hrs PDR Presentation	On Teams
29	26 Mar	PDR Presentation	PDR review and feedback
30	2 Apr	Embodiment sketch	Refinement of embodiment design
31	9 Apr	Initial Solidworks assembly model and GA drawings	Discuss detailed design, selection of suitable materials and standard parts and
32	16 Apr	Design Philosophy Proposal Slides	Review of design philosophy proposal
33	23 Apr	Updated GA and detailed drawings and detailed calculations	Tutor feedback to GA and detail drawing, detail calculations, preparation for CDR report
34	30 Apr	Draft CDR report	Tutor review and feedback on CDR report
35	7 May	Draft CDR report	Tutor review and feedback on CDR report
35	10 May	23:59 hrs CDR submission	On Teams

7. Marking Scheme

This project is worth 25% of the MMME 2042 module.

A formative Preliminary Design Review (PDR) will need to be submitted by the indicated date, which should justify the choice of proposed design and calculations.

The type of information required:

· The Concept options considered, illustrated by a Morphology chart.

· A concept which seeks to address all the functional requirements.

· Supporting preliminary calculations to show the concept is viable.

Summative Critical Design Review (CDR) Marking

CDR is worth a total of 100 marks.

Report – 10 marks.

· Structured correctly and presented appropriately.

· Clear introduction and concise summary of work, including the final Morphology chart and a Compliance Sheet.

· Includes Statement of requirements.

Engineering – 20 marks

· Morphology Chart

· Basic sketches

· Will it work for the specified function and performance?

· Is due consideration given to the selection of appropriate components?

· Is due consideration given for manufacturing and assembly?

· Are limits and fits appropriate?

· Is there clearance for moving parts?

· Does the design have an appropriate selection and placement of seals?

Evaluation and Calculations – 20 marks

· Actuation forces required.

· Sizing of components to produce the actuating forces.

· Reserve factors on main shaft fatigue stress.

· Main flange bolt stressing for axial and torque loads.

· Bolt torque required to prevent flange separation for the worst case.

· Oil tube whirling margin.

· Calculations to show that no damage will occur in the event of one blade fouling.

Material selection 10 marks

· Are suitable materials selected?

· Is any heat treatment or condition required?

· Are they available?

· How are parts manufactured?

Assembly Drawings – 15 marks

· Parts list – all parts identified with BOM balloons, all necessary bought-in part details or standards quoted, materials and quantities identified.

· Layout - sufficient views – how is it assembled? A setting up procedure to be included as text.

· Does it meet the design intent?

· Are limits and fits correctly identified?

Detail drawing – 10 marks.

· Are the drawings to BS8888?

· Are the drawings complete – are enough details given to define parts?

· Datum features established.

· Tolerances specified.

Engagement – 15 marks

· Sufficient progress is shown in PDR.

· Attendance of Design Office sessions and active participation in discussions

· All deadlines met.

· Active engagement with tutor and working effectively.

8. Hints

The layout picture shows the engine and gearbox inclined. DO NOT DRAW THE PROPELLER INCLINED.

Study the brief and have a clear view of what is required. The Blade Forging model and the Stern-tube assembly are available on Moodle.

All the information provided may not be required; it is a part of the design task to identify the key parts.