ARNOLD AIR FORCE BASE, TENN. ñ A team comprised of engineers, outside machinists, schedulers and other specialists at Arnold Engineering Development Complex have focused their ideas, energy and time over the past four years on completing the first major modernization program on the 1950s-era von K·rm·n Gas Dynamics Facility.
Win Phipps, the senior test project manager for AEDC’s Propulsion Wind Tunnel Test group, said, The initial operating capability test runs for VKF Wind Tunnel B were completed in March, with Tunnel A completed in August, and the IOC for Wind Tunnel C is scheduled for September.
Over the years, virtually every high speed flight vehicle has required testing in Tunnels A, B and C ñ from reentry and tactical vehicles and space capsules to the X-planes and winged vehicles.
VKF is comprised of three continuous-flow units, Supersonic Wind Tunnel A and Hypersonic Wind Tunnels B and C. The facility also includes an air processing and conditioning plant that incorporates a multi-stage air compressor system and reservoirs for high pressure air storage. The conditioned, high pressure air is used to simulate jet flows from the models under test in the wind tunnels and also provides high-pressure air for the power ejectors in AEDC’s arc heater chambers, ballistic ranges G and S, Propulsion Wind Tunnel (PWT) and Aeropropulsion Test Unit (APTU).
Prior to the funding of the VKF modernization program in 2007, VKF had not undergone a major upgrade, other than being semi-automated in 1980. The VKF plant’s main drive motors and motor controls were original equipment from when the facility first became operational in 1958.
Our goal is to ensure the viability of the VKF plant for another 20 to 25 years of operation, Lucy said.
This team effort, led by Frank Wonder, Aerospace Testing Allianceís Flight Systems Acquisition acting section manager and Ozey Young, VKF Modernization Program Manager, increased safety with some new switchgear and we also made it more efficient by putting in new control systems and a new variable frequency starting system. These combine to decrease the operational cost of running the VKF plant.
Switchgear is the combination of electrical-disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment at a place like AEDC.
Lucy also spoke about the improvements to the VKF wind tunnels.
VKF is near completion and once the 4T improvement program completes in Fiscal Year 2014, wind tunnels A, B and C and Propulsion Wind Tunnel 4T will all have that common data acquisitions system template, he said. So, a test customer can come in and run a test in a transonic through the supersonic-hypersonic regimes with a common data setup or common recording tool.
This will increase productivity within A, B and C wind tunnels. We replaced the three separate VKF control rooms with a brand new common operations center. Itís going to be useful to have the test customer and AEDC operators all co-located, which will improve communication.
Lucy added, ìWe also have a new shadowgraph Schlieren system, providing great graphical and video test data to the customers.
VKF plant modernization
The VKF modernization program has included modernizing and rewiring the plant main drive system motors to take advantage of the new wiring and insulation capabilities to get more horsepower out of the same physical space of the iron on those motors, Phipps said. ìIt did away with the starting motors through the increased horsepower of the main drives too. Electrolyte coolers that were part of the old starting system, and a maintenance headache, went away, too.
Installing a new variable frequency starting system and getting rid of the starting motors also reduced maintenance and increased the productivity, because we used to stop every 60 hours to clean those brushes on those old starter motors. Now, we can run for 120 hours and stop to clean the brushes on the main drive.
VKF wind tunnel modernization
Phipps said the VKF modernization program has also focused on the hypersonic wind tunnels and their components.
ìWeíve replaced the Tunnel A oil filled actuators in the nozzle and diffuser with new electrically driven ones,î Phipps said. ìThe oil filled ones were a maintenance headache, which required eight hours of cleaning after 24 hours of operation. The old nozzle positioning computer was the oldest one on base at the time it was replaced too. We fixed it with parts from eBay, the last time we used it. So, weíre excited about the productivity and reliability gains here.
ìStandardization across wind tunnels is one of the modernization program goals. For, example, the same nozzle and diffuser actuators type acquired for Tunnel A will be used in 4T too, which enhances maintenance and reduces the part types on base.
ìWeíre upgrading the Schlieren systems and cleaning the mirrors too. The Tunnel A, Tunnel B and Tunnel C test article control systems were refurbished just before we took the systems out of service to start this modernization.
That plant and test cells were built in the 1950s and this is a really significant upgrade. Itís probably just in time too. For example, Conventional Prompt Global Strike, High Speed Strike Weapon, High Speed Missile, Space Launch Systems, and High Performance Interceptor customers have expressed strong interest in leveraging AEDC supersonic and hypersonic capabilities.
Asked why VKF is important to the customer, Phipps said itís all about productivity.
Tunnel A and B and C are whatís called continuous flow test facilities, he said. Although it takes a few hours to get on conditions, once the facilities are on conditions, test operations could be sustained for days without interruption. A model insertion system, which is similar in all the tunnels allows you to make model changes in a tank below the test cell and go right back in the test cell immediately.
Uninterrupted test times means acquiring lots of data quickly.
That contrasts remarkably from a blow-down facility where you blow for a few seconds and get a few seconds of data, then you make a test article change, then you have to pump up again to get the next run. A customer commented that he got twice as much data in one 20-hour period in Tunnel A, as it took to get in 12 weeks of 12-hour days at a blow down facility. So, getting lots of data is what Tunnel ABC is all about.
Phipps added, VKF Wind Tunnel A, B and C are the most productive tunnels in the world. A/B/C, collectively, have the highest data rates of any tunnels in the world.