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