system level design review p16318 gaseous mass flow rate controller luke mckean, lianna dicke,...
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SYSTEM LEVEL DESIGN REVIEW
P16318 Gaseous Mass Flow Rate ControllerLuke McKean, Lianna Dicke, Selden Porter, Schuyler Witschi
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Agenda● Phase I Review
○ Problem Statement○ Updated Phase I Documentation○ Review P15318’s Prototype
● Phase II Tasks○ Shared Vision○ Functional Decomposition○ Concepts and Development○ Feasibility Analysis○ Proposed Test Plan○ Risk Assessment
● Phase III Plans
Problem Statement• Environmentally and economically CNG
makes sense as an alternative fuel• Delivering a precise portion of Compressed
Natural Gas is necessary for an engine to operate
• Current device done by previous MSD team has functional limitations
• New design will deliver a precise amount of CNG
• Use a PID control algorithm • Designed for use in an automotive
environment
Updated Customer Requirements
Updated Engineering Requirements
Updated House of Quality
P15318’s Prototype Test Results
P15318’s Design Decomposition
Temperature Sensor
Position Sensor
Rotational Actuator
Pressure Sensor
Output Fitting
P15318’s Design Decomposition
Known Issue: Leak rate when fully closed
Suspected Cause: Plastic on Metal face seal failure
High mfg tolerances required
P15318’s Design DecompositionKnown Issue: Slow response time
Suspected Cause: Friction in the system due to face seal, Issues with microcontroller and software.
Shared Vision:
Shared Vision:
Shared Vision:
Functional Decomposition
Functional Decomposition
Functional Decomposition
Functional Decomposition
Functional Decomposition
Morphological Chart
Morphological Chart
Concept GenerationValve ideas in detail
Ball/Cam
Concept GenerationValve ideas in detail
Poppet Valve
Concept GenerationValve ideas in detail
Rotational Disc
Concept GenerationValve ideas in detailNeedle/Seat
Concept Selection
Pugh Analysis Results
• All concepts are variations of the same concept• Each component type independent of the others• Need to analyze components in detail in Subsystem
Design Phase
System Architecture
System Level Flowchart
Feasibility QuestionsWill we be able to model the flow as incompressible?
• Incompressible flow is fairly accurate for M < 0.3• Spoke with Dr. Liberson• Using:• • Calculated M at the outlet of the valve, resulted in M=1.709• To accurately model the flow it must be considered compressible, and
it is supersonic at the exit.• Need to verify next steps to flow modelling with Dr. Liberson
Feasibility QuestionsWill a metal-on-metal seal be able to prevent leak (< 25
sccm)?• Experience with testing EGR valves:
• Steel poppet/seat was able seal with leakage much less than 25 sccm
• Need to determine how to model leakage• Talk with ME faculty
Feasibility QuestionsIf our system is required to ‘unseat’ a valve, will our
current actuator have enough torque?
Feasibility QuestionsIf our system is required to ‘unseat’ a valve, will our
current actuator have enough torque?
Assumptions Needed:● Neglecting Friction (for now)● Cam Profile is linear ramp● Valve is sealed only by air pressure● Cam diameter● No spring assist
Feasibility QuestionsIf our system is required to ‘unseat’ a valve, will our
current actuator have enough torque?
Feasibility QuestionsQuestion: Are thermistors, or resistance temperature detectors feasible
for our temperature sensing needs?
*Thermocouples were not included in this feasibility study, but will be added for consideration in the sub-system design phase.
Feasibility Questions�Question: Is it feasible to use a general purpose, flush diaphragm, or PCB
mountable pressure transducer?
Feasibility QuestionsQuestion: What technologies might be feasible for our positional sensing needs?
Feasibility QuestionsQuestion: How much power will our system consume?
Feasibility Questions
Can a microcontroller be used for this project?
Some requirements are:Operating Voltage: 1- 5VTemperature Range: -40 to 85 degrees CelsiusSpeed: > 20MHzI/O Pins: >20
Feasibility Questions:
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Feasibility QuestionsCan a microcontroller be used for this project?
We are still researching potential ways to optimize microcontroller response:• the use of lookup tables vs real-time calculation• processing speed/power vs available memory
Careful attention to price
Proposed Test Plan
Proposed Test Plan★Test Valve
○ Run compressed air through device and open and close valve★Test Microcontroller
○ Generate values to simulate varying sensor readings★Test Response Time
○ Have the microcontroller open and close the actuator★Test with Installed Sensors
○ Vary sensor variables to test microcontroller response★Test Voltage Regulator ★Test Leakage
○ Pressurized system and measure amount lost due to leakage★Test Flow Rate Accuracy and Repeatability
○ Connect device to compressed air tank and measure output
Risk Assessment
Risk Assessment continued
Risk Assessment continued
Next Phase Plans
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