Jet engines’ test cells –
Considerations in selecting
level of automation
Presentation for: 10th Israeli Symposium on
Jet Engines and gas turbines
Presented by: Ze’ev Ben-Porath
November 2011
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Introduction
The company: Magnus Engineering inc.
Specializes in the construction and maintenance of
computerized test cells since 1991.
- Please visit www.magnus-eng.com
The product: MCTC - Magnus Computerized Test Cell
* Integrating all aspects of test cell operation.
* Installed in more than 35 test cells worldwide.
* Currently implemented for over 60 engine types.
* 95% “generic”.
* External test cell definition - User updateable.
* Supports all levels of automation.
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Introduction (2)
The test cell: F100-PW-229 Post-Production at WZL4
* Built by P&W for Polish AF.
* International bid won by ATEC+Magnus.
* ATEC – main contractor.
Construction, Adapter, Fuel System (+heating), etc.
* Magnus – subcontractor.
Data acquisition, System control, Computer system.
* ~4-hour test process as defined by TIS.
* 95% automatic run.
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Automation Levels Definition (1)
Level 1: No Automation
* No central computer system.
* Independent displays of subsystems’ data.
* Manual recording (and processing) of data.
* Very common for jet engine test cells in 1980-90’s.
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Automation Levels Definition (2)
Level 2: Centralized Data Acquisition
* Central computer system, acquiring data directly
or digitally from all other subsystems.
Benefits:
* Automated data processing (e.g.: filtering, average,
maximum, minimum, tare-value computation).
* Computation of derived parameters and states.
(e.g. corrected performance data, steady state).
* Alarms for simple and complex limits.
* Data recording and playback/analysis capabilities.
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Automation Levels Definition (3)
Level 3: Test procedure Tracking
* Central computer system tracks the testing
process, instructs operator and performs the
required engine data validation.
Benefits:
* Ensures adherence to specified test procedure.
* Eliminates possible human errors in evaluating results.
* Automated computation of process-related data.
(e.g. maximum vibration points, transient timing etc.).
* Significant savings in time and fuel.
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Automation Levels Definition (3.1)
Level 3 example: Vibration sweep for F110-GE-100
Task Definition:
(3) Advance throttle slowly, taking 2 minutes to reach intermediate, and
stabilize engine for 30 seconds.
(4) Retard throttle slowly, taking 2 minutes to decelerate to idle.
(5) Record peak vibration and rpm at which peak occurred…
In the following demo, 4 Vibration values are tracked, and
peak rpm values recorded separately for idle->MIL, MIL dwell
and MIL->idle sections.
(display rate is 10 times faster than actual rate).
Actual
times:
Vibration sweep demo:
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Idle->MIL: 2min,
21sec
MIL dwell: 48sec
MIL->idle: 1min, 48sec
Total: ~5 minutes 7
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Automation Levels Definition (4)
Level 4: Automated Test Execution
* Central computer system executes all (or most)
of the test procedure by sending appropriate
commands to the engine and/or to external
subsystems (PLC, Throttle, Dynamometer etc.).
Benefits:
* Exact execution of complex test procedures.
* Improved safety due to fast response to dangerous situations.
* Accurate repeatability of tests (facilitate research/development).
* Savings in time and fuel.
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Automation Levels Definition (4.1)
Level 4 example: Safety event in a Volvo (bus) engine
Event Description:
(1) Water pump breaks down.
(2) Vapors rising into cooling water tank cause increased pressure.
(3) System detects abnormal cooling water level (measured as pressure).
(5) Audio and Visual Alarms activated.
(4) Smooth return to Idle/Manual mode is automatically executed.
Safety Event demo:
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Automation Level Driving factors (5.1)
Driving Factor A: Test Accuracy Requirements
* Requirements for very accurate execution of complex test
sequences may necessitate level 4 automation.
* Jet engine testing requirements (as we encountered)
are sometimes border line cases:
- Measuring transient of ~2 seconds (TIS).
- Break-In procedures (e.g. a sequence of 2,5,2,5…
seconds transients to intermediate PLA positions).
- Vibration sweeps requiring smooth (constant rate)
movement of PLA.
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Automation Level Driving factors (5.1.1)
Example: Manual vs. Automatic Vibration sweep
The Task: (F100-PW-229, Core Run-In)
“Perform slow acceleration (20-30 seconds) [from 56º] to MIL”
Manual Vibration Sweep - 56->MIL - run 1405 - 11:35:14-11:35:59
90
85
80
75
PLAX
70
65
60
55
50
190 181 172 163 154 145 136 127 118 109 100 91 82 73 64 55 46 37 28 19 10
1
Relatively good coverage of the range, but in ~45 seconds.
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Automation Level Driving factors (5.1.2)
Example: Manual vs. Automatic Vibration sweep
The Task: (F100-PW-229, Core Run-In)
“Perform slow acceleration (20-30 seconds) [from 77º] to 91º”
Manual Vibration Sweep - 77->91 - run 1405 - 12:17:13-12:17:35
95
90
85
PLAX
80
75
70
97 93 89 85 81 77 73 69 65 61 57 53 49 45 41 37 33 29 25 21 17 13 9
5
1
Same operator, 45 minutes later (tired and impatient?):
Up to MIL in 2 jumps. ~20 seconds to 91º.
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Automation Level Driving factors (5.1.3)
Example: Manual vs. Automatic Vibration sweep
The Task: (F100-PW-229, Core Run-In)
“Perform slow acceleration (20-30 seconds) [from 77º] to Min
Augmentation”
Automatic Vibration Sweep [TIS]-77->MinAug-run 37-12:50:28-12:50:47
100
95
90
PLAX
85
80
75
70
76 73 70 67 64 61 58 55 52 49 46 43 40 37 34 31 28 25 22 19 16 13 10 7
4
1
Spikes due to problems in the Electric Throttle.
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Automation Level Driving factors (5.2)
Driving Factor B: Test Complexity
Complexity: Number of steps, rate of changes, number of
different output commands, requirements to synchronize
external subsystems (e.g. move throttle while changing load
generated by a dynamometer – T700 testing).
* Very Simple tests: Level 2 sufficient
(e.g. run engine 30 minutes, measure oil consumption).
* Intermediate complexity: Level 3 or 4
(depending on other factors). Most Jet engines.
* High complexity: Level 4 recommended
(if not too hard to implement!). e.g. 8000->3500->7400
->3500rpm, ~500 changes, 80 hours break-in run for UAV
engine. Optimized using dynamic PLA-RPM mapping function.
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Automation Level Driving factors (5.3)
Driving Factor C: Work Load
The work load determines the economic viability of
full automation (level 4).
* low work load: Level 2 or 3.
* medium work load (typical for Jet engines): border line case
for investing in level 4 automation. Exact calculation required.
* High work load: indication for level 4 automation.
(Unless the complexity is very, very low!).
Sample case: Egged bus-engines test cell.
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Automation Level Driving factors (5.4)
Driving Factor D: ”Cost of Error”
A very high cost of error in the test procedure
(combined with medium or high test complexity)
may dictate full automation,
even in cases of low work load.
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Estimating expected time savings (1)
A method to estimate expected savings in test time by
upgrading an existing test cell to a higher automation level.
1. Identify a significant section of the test procedure where all steps
are “well-defined” duration-wise.
Well defined: - Stabilize 5 seconds at 91º.
- Perform slow (20 to 30 seconds) to MIL.
Undefined: remain at IDLE until main oil temperature reaches 100°F.
2. locate a set of executed tests (for said section) which were
executed successfully, continuously and accurately (avoid cases where
test steps were shorter than the minimum time specified by the test
instructions).
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Estimating expected time savings (2)
3. Compute:
Tmin = theoretical minimum time to complete the test section.
Aavg = Average actual time to complete the test section.
Amin = Minimum actual time to complete the section.
4. Upper limit of saved run time: Aavg - Tmin
5. Minimum expected saved run time : Aavg – Amin.
6. If you have access to a test cell that runs the same tests at the
target automation level – extract from that test cell data:
Eavg = average execution time at target automation level.
7. Actual expected saved run time : Aavg – Eavg.
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Estimating expected time savings (3)
Sample Calculation:
- Section C and D of the F100-PW-229 acceptance test (C1 to D11).
- Data from 12 runs from 2 different test cells.
- Test cells at automation level 3, considering upgrade to level 4.
Tmin = 23 minutes, 5 seconds (1,385 seconds).
Amin = 24 minutes, 44 seconds (1,484 seconds).
Aavg = 25 minutes, 51 seconds (1,551 seconds).
Amax = 27 minutes, 48 seconds (1,668 seconds. 33m case
discarded)
lower limit on saved time: Aavg–Amin = 67 seconds ~4.3%(of Aavg)
upper limit on saved time: Aavg–Tmin = 166 seconds ~ 10.7%
Note: block of 15 minutes at IDLE observed at beginning of all runs.
Means the expected fuel saving will be much more than 11%.
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Estimating expected time savings (4)
Another Sample Calculation:
- Steps 36-99 of the F100-PW-229 Core Run-IN.
- Data from 5 runs from 1 test cell.
- Test cell at automation level 3, considering upgrade to level 4.
Tmin = 1,901 seconds.
Amin = 2,051 seconds.
Aavg = 2,077 seconds.
Amax = 2,124 seconds.
lower limit on saved time: Aavg–Amin = 26 seconds ~1.3%(of Aavg)
upper limit on saved time: Aavg–Tmin = 176 seconds ~ 8.5% 20
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Estimating expected fuel savings (1)
The expected fuel saving (%) is larger than the expected time savings
since the periods at high power settings are much shorter than the
periods at IDLE.
Given an existing level 3 test cell, it is possible to estimate the fuel
savings by an upgrade to level 4, by precise analysis of recorded test
runs:
1. Section 1 and 2 as before.
2. Compute the theoretical time to stay at each PLA position (range).
3. Extract scan data for the selected test sections
including PLA setting and fuel Flow (MCTC-4 scans/sec).
4. Compute actual time and average fuel flow at each PLA position.
5. Compute total time and total fuel flow at each PLA position and
compare to theoretical time.
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Estimating expected fuel savings (2)
Sample calculation for:
- Steps 36-83 of the F100-PW-229 Core Run-IN.
- From a manual run at a level 3 test cell.
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Estimating expected fuel savings (3)
Sample calculation for:
- Steps 36-83 of the F100-PW-229 Core Run-IN.
- From an Automatic run at the WZL4 test cell.
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Actual / Expected results
Based on our actual experience and the above discussions:
- Upgrade from level 2 to level 3 has resulted in
30-50% save in run time and fuel consumption (IAF, SAF).
Main sources of improved efficiency:
* Automatic evaluation of complex engine checks.
* The “computer-game” effect on the operators.
- Upgrade from level 3 to level 4 will result in
5-10% save in run time and fuel consumption
Main source of improved efficiency:
* Prompt and precise execution of test tasks.
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Economic feasibility analysis of level 3->4
upgrade
Consider a possible upgrade of an existing test cell, currently running
an F100 engine, using the MCTC at level 3 , to level 4.
Estimated (roughly) cost of upgrade: Electronic throttle – 120K$.
Software upgrade – 40K$.
Mechanical + PLC upgrade – 40K$.
Total Cost – 200K$.
Assuming:
- savings of 10% in fuel consumption.
- 9,000 liters per average engine run.
- 24 runs per year.
- 1$ per 1 liter fuel (??).
Investment will cover itself in: 10 years.
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Conclusions
* Level 2 automation is a MUST for any non-trivial test cell
This is simply “good engineering practice” and facilitates
quality assurance application for the testing process.
* Level 3 automation is highly recommended for any test cell with
non-trivial testing procedure and a more than minimal work load.
This will result in significant time and fuel savings, as well as
significant improvement in the reliability and accuracy of the testing.
* Level 4 should only be considered if the work load is very high
or if other factors (test complexity, required accuracy, “cost of
error”) cannot be satisfied by a manually operated test cell.
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Final tip
To really optimize the testing procedure:
- Check with the engine vendor to find out how the required
testing is done at their facility!
You may find that their actual procedure is different (and more
efficient) than the formal procedure.
Case at hand: T56 test cell for TUAF.
Thank you for your attention.
Any Questions?
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