Final Design Report.doc
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1. Executive Summary
The Eddy Current Brake Mechanism team has been given the task of designing a braking system that will create a differential torque for the activation of a Honeywell Aerospace Generator Disconnect. This document will state the problem with the current Honeywell disconnect system and how we have taken the voice of the customer into consideration in coming up with a Final Design that will analytically produce the necessary torque for disconnect activation, thereby fulfilling the requirements set by Honeywell Corporation. Upon establishing a Final Design we will explain how the design works and why this particular design is ideal for application for disconnect activation. Our Final Design will comply with all given environmental, functional, and financial constraints and conditions, which will also be clearly defined within this document as well as showing how they were taken into consideration for our design. Seeing as we do not have the capability to transport any testing equipment from Honeywell, the production of a test rig was another task required of us for proof of concept and design. This report will discuss how our design will work within all technical specifications including the test rig’s ability accurately simulating all conditions. We will establish an innovative solution to an existing irreversible, damaging, and costly disconnect system.
2.1. Document Purpose
The objective of this report is to establish an understanding of requirements set by Honeywell and presenting a conceptual design that fulfills those requirements that will later be put into production and become standard equipment on Honeywell generators. This report will present an Eddy current brake activation system per request of Honeywell. We will present analysis of an Eddy Current Brake System which will lead into why an Eddy Current Brake design is superior to other forms of disconnect activation which we will rule out on various systematic ways.
To give a brief overview, this document will include a problem statement and background as well as all customer needs for Honeywell’s current activation system. Upon establishing the Background and Problem Statement this report will include a brief Conceptual Solution which will adhere to the broad variety of Technical Specifications, also included in this report. The Technical Specifications will present various forms of constraints and information that will be considered and discussed in more detail about their influence in the Design Concept and Structural Analysis portions of this report. The following presents information included within this report:
2.2. Problem Statement
A disconnect system on a high-speed generator serves as a safety device. The disconnection occurs between the gear box and the generators drive shaft in order to prevent further propagation of failure. A disconnect system has already been developed and now needs and activation system. For more information on the disconnect system see Appendix A.
We have been given the task of designing an activation system that triggers this disconnection. A preference has been set in terms of function in the design of our innovative disconnect system. The problem with the current setup occurs with multiple disconnects. With the current design disconnection can happen once, then must be repaired before the generator and it’s disconnect will function again. We must design a reset able and reversible activation system that operates at variable speeds while remaining maintenance free.
The disconnect system currently in use by Honeywell for a high speed generator comes in the form of a simple mechanically based part called a shear neck located between the generator and the gear box. For the shear neck to perform its function as a disconnection, the shear neck itself creates an additional constraint. The shear neck is design around a certain angular acceleration/velocity thereby limiting its ability to activate when desired. As a result, the shear neck might not engage at a certain angular acceleration/velocity. Once the shear neck does perform its function properly, and at the required torque, the shear neck must be replaced, hence making this particular disconnect system irreversible. Due to the irreversible nature of the shear neck and lack of function at variable speeds, the shear neck design proves very costly and labor intensive. Elimination of such a mechanically dependant component will prove extremely beneficial to the Honeywell corporation.
2.4. Customer Needs
Honeywell is a well respected and innovative company that develops vast amounts of products for both military and commercial applications. The innovative asset is important to the Honeywell Corporation; they must stay one step ahead of their competition at all times. We feel Honeywell has given us the opportunity to become an innovative asset to their company and help in their advancement of aerospace generators. Our contacts, Simon Waddell and Balwinder Birdi, have been extremely helpful in guiding us through the process of developing their new disconnect activation system.
Honeywell needs a new form of activation for their generator disconnect system. In order for the disconnection to take place we must provide a differential torque to decelerate a ball-screw-nut. The differential torque must also comply with all of the given Technical Specifications. The differential torque is the primary need. If the differential torque is not provided then disconnection fails. With the Technical Specifications given and the torque needed, Honeywell recommended designing an Eddy Current Brake System (ECBS).
2.5. Conceptual Solution
We took Honeywell’s recommendation and concluded that for the given Technical Specifications, the Eddy Current Brake System is an ideal final solution. The ECBS contains few moving parts and is completely free of contact with the exception of a disc being fastened to a drive shaft. Our team came up with a few other ideas aside from the ECBS that have their own strengths and weaknesses. Some of those concepts are:
Table #2: Design concepts
Design Concept Strengths Weaknesses
A Fluid Driven Turbine Brake
Use of bleed air
Potentially light weight Difficult to design/analyze
Requires pumps and release valves
Design around certain RPM
Reverse Direction Motor
No frictional contact
Motors are well established Heavy rotating parts/complicated controller
Angular Momentum Brake
Impervious to EMP Many heavy moving parts
All of these were ruled out for the various reasons given as weaknesses. The ECBS turns out to fulfill all of the Technical Specifications and with further analysis we will find a reasonable torque for the ECBS design to prove itself as the superior design of the main for concepts. This report will go into a more thorough description and analysis in section five titled “Final Design” starting on page 15.
3. Technical Specifications
3.1. Voice of Customer
Following our meeting with Honeywell representative Balwinder Birdi, we discussed our notes taken from that meeting and clarified any information that seemed unclear. Upon reviewing our meeting notes we developed an all inclusive “voice of the customer” needs. From the “voice of the customer,” we broke up the needs into constraints and functional requirements. The constraints were then broken down into four sub-categories. We present those categories as:
• Environmental Conditions
• Operational Conditions
• Functional Conditions
• Test Rig Properties
These conditions and constraints have certain properties that will limit our design and will be discussed in the following sections.
3.1.1. Functional Requirements
Our team determined the top level Functional Requirements are; Activate the generator disconnect, be reset-able, and be maintenance free. We will discuss how our final design will encounter and fulfill the functional requirements of our projects. With these functional requirements set we will also establish an ideal final result which we will not achieve but a goal to come as close as possible to attain.
3.1.2. Design Parameters
3.1.3. Constraint and Conditions
We broke down the constraints and conditions into sub-categories. Those categories cover the Environmental Conditions, the Operational conditions, Functional Conditions, the Budget as well as Test rig properties and physical limitations. The given constraints include; operation at a certain RPM, a limited power source, and operation in an oil mist environment just to cite a few examples. In addition to the given constraint, we established a couple of implied constraints. These implied constraints come in the form of developing a test rig or physical limitations. In the next section we will discuss these constraints and properties in more detail and what part of the design it might inhibit.
3.2. Environmental Conditions
We were given a temperature constraint of the brake to operate between -50 degrees Fahrenheit to 300 degrees Fahrenheit. This constraint sets a design limitation that must take into consideration the materials used for our design.
The brake has to function in an environment containing a range of 10% to 80% humidity. This will obviously limit out choice of materials because we do not want the material to deteriorate due to moisture. Other than material choice we don not believe this will limit our design any more than material choice. The humidity may even act as an aide in the cooling of a braking system.
Our design must be balanced to 0.005 oz. in. for all rotating parts. This precedence was established by Honeywell so the rotating parts will not have an effect on the operation of the generator. An imbalance will create an additional stress in the rotating part as well. The effect an imbalance will have on our design will be discussed in the Final Design section of this report.
3.2.4. Oil Mist
The Braking system will operate in an oil mist environment. This will create a limitation for a couple of our design concepts, however will create an advantage for one of the designs in the form of cooling which will be discussed in the Final Design section of this Report.
Our brake system design must function within an elevation range of 3000 feet below sea level to 70,000 feet above sea level. This will simulate the broad application of the braking system as well as the operable elevations of the generators. We cannot completely neglect any effect the elevation will have and have considered the effect of elevation with respect to our final design.
The pressure range we have considered in our Final Design will work within 0.75 to 1 atmosphere. The pressure range will also take into account the elevation change as well as any differential pressure between the pressure due to elevation and the pressure in which the generator creates.
3.3. Operational Conditions
3.3.1. Angular Velocity
We must design a gracing system that will operate at a minimum angular velocity of 7,200 rotations per minute and a maximum angular velocity of 28,000 rotations per minute. This constraint will have an effect on each of the concepts in its own way and was a major factor in determining a final design. The Final Design section will discuss how the range of angular velocity will affect the Final Design
3.3.2. Power Source
Our design will operate with a limited power source of 28 volts DC. This constraint operates with the power supply allowed by the generator. On top of operation at this power input we must develop a test rig that simulates the power supply.
3.4. Functional Conditions
3.4.1. Duty Cycle
Our braking mechanism should not deteriorate over time. We also need it to last for the life of the generator. Due to the fact that this activation system must act when triggered we cannot have any part fail due to deterioration.
3.4.2. Design Envelop
Our Braking system design must fit into a design envelop of a 5 inch Diameter and a 1.25 inch width. The free area of our disk will also depend on the drive shaft diameter which will have an affect on one of our proposed design concepts.
3.4.3. Hazardous Material
We may not have any hazardous material for unspecified reasons stated by Honeywell. Fortunately for our Proposed Designs, we will not require the use of any hazardous materials.
Our final design and product must have a reliability of 99% operational readiness. Our product must work when triggered. Late activation or no activation may cause irreversible damage to the gearbox, generator, or both. It has to work with NO uncertainty.
We have been given a budget of $2,000. We may not go over that amount and no additional funding will be allotted.
3.6. Test Rig Properties (accurate simulation of actual application)
Our test rig needs to be portable to allow the demonstration at Design Day as well as for presentation to Honeywell. If it is too heavy we will not have the ability to transport the test rig in order to demonstrate our product.
The test rig must provide a power of 28 volts to accurately simulate the activation of our braking system during operation on the generator.
The test rig needs to accurately model the design envelop established in the Functional Conditions.
3.6.4. Motor Output
The motor on the test rig must supply a sufficient amount of torque at the velocity needed to simulate angular velocity of the actual generator.