BRE tests the cabin environment

BRE's Aircraft Cabin Environment rig uses the front fuselage section of an Airbus A300 to test the effects of internal environmental conditions—including noise, vibration, and temperature—on cabin crew and passengers.

Aircraft cabin air quality specialist BRE has developed a new test facility to examine the effects of aircraft interior conditions, including noise, vibration, temperature, and humidity on cabin and cockpit crew and passengers. Called the Aircraft Cabin Environment (ACE) facility, it will contribute findings to two EU-funded projects that are considering the health and comfort effects of the aircraft environment with an aim to improving environmental comfort while working within parameters that will not adversely affect factors such as fuel consumption, fire safety, and weight. Human factors such as personal perceptions and individual comfort levels will also come into play.

BRE is installing the ACE test facility at its Watford headquarters. It comprises the forward fuselage of an Airbus A300 that will be equipped to mimic a wide range of conditions: temperature, air velocity from nozzles, humidity, vibration, radiant heat (hot and cold), illumination, and air quality. The fuselage section is being instrumented with a range of test equipment; results will be downloaded for analysis. "The main emphasis is to look at the impact of air quality, ventilation, noise, and vibration," said Earle Perera, BRE's Commercial Director. "This (research) will be an ongoing program and may also look at security issues. The test work will be computer-controlled. Although it will contribute to the EU programs, the ACE facility is BRE-funded. We don't believe such a program has been carried out before, although we understand that Airbus will have a similar program specifically for the new A380."

BRE is the coordinator of the EU-funded project, CabinAir, which is investigating ways of improving the performance of environmental systems of commercial aircraft and is to develop, for what it claims is the first time, standards for measuring air quality in aircraft. The second stage of the project, in-flight monitoring, has been completed and involved 50 British Airways, SAS, and KLM revenue-earning flights to destinations including Rome, Cairo, and Bangkok being subject to the application of monitoring protocol developed by the CabinAir Consortium. Measurements focused on the key factors influencing passenger comfort and well-being: humidity, air velocity, temperature, and the constituents of the cabin air. The data will be used to establish a picture of conditions on short, medium, and long-haul flights in the commercial sector of the airline industry, according to BRE. Volunteers will represent passengers and crew on simulated flights of up to 12 hours.

CabinAir also investigated ways of improving the performance of environmental control systems and of reducing environmental impacts such as minimizing engine bleed and re-using pressurized air. Now, work has started on the development of a draft European Pre-normative Standard for passenger aircraft cabin environment. The CabinAir project continues with findings scheduled to be reported in late 2003. The project involves 16 partners including the three airlines mentioned above, aircraft manufacturers Airbus and Boeing, engine manufacturer, Rolls-Royce Deutschland, systems manufacturers Honeywell Normalair-Garrett and Pall Aerospace, plus the UK Civil Aviation Authority, the Royal Air Force Centre for Aviation Medicine, and environmental technology groups.

- Stuart Birch

Understanding jet engine aerodynamics

Although it is more than 60 years since the earliest jet aircraft (the Heinkel 178 and Gloster/Whittle E.28/39) first flew, the aerodynamics inside a jet engine are still not totally understood, mainly due to the unpredictability of the air flowing through the engine. But now a research team at Heriot-Watt University in the UK has developed very small fiber-optic pressure sensors that can be placed inside the stator section of a jet engine test rig.

The researchers, led by Jim Barton, stress that because of the extremely high temperatures involved, the sensors have not been produced to work in real engines and it may be "some time" before that milestone is achieved. However, Barton regards the development of the sensors as a significant contribution to enabling engineers to collect data that will facilitate the design and production of more aerodynamically efficient engines, which in turn will bring improvements in fuel efficiency, performance, longer component life, and reduced maintenance costs.

Speaking at the Photon 02 Conference in Cardiff, Wales, Matthew Gander, a member of the team, described how five optical sensors were used to make what are claimed to be the "first-ever" high-bandwidth pressure measurements at the trailing edge of a stator blade (the stationary blade behind the rotor) in a jet engine turbine simulator. The experiment was performed at QinetiQ's Isentropic Light Piston Facility at Farnborough.

The sensors were fabricated on silicon wafers using the micromachining facilities at the Rutherford Appleton Laboratory. Each sensor is smaller than the size of a half-millimeter cube but contains a diaphragm that flexes in response to a pressure change. The Fiber Optics Group at Heriot-Watt completed the sensors by attaching them to the ends of optical fibers. The sensors function due to a minute air gap called a Fabry-Perot cavity between the diaphragm and the optical fiber. Light resonates in the cavity and the position of the diaphragm determines the phase of the resonance, the phase signal being recorded via the optical fiber.

According to Barton, the sensors developed by the research team are smaller than electrical gauges and producing them by micromachining was potentially cost effective. "The small size allows them to make measurements that were not previously possible," he said. "Sensors with this capability are opening up areas of flow measurements, which can contribute to an improved understanding of the aerodynamic processes in an engine, with benefits for future design."

- Stuart Birch

SwRI traces jet fuel contaminant

The U.S. Air Force (USAF), as well as other military branches, has been working for almost 50 years to identify the cause of jelly-like contaminants in fuel-handling systems. Despite studies to isolate the gelatinous material that varies in color from light amber to dark reddish-brown and commonly referred to as "apple jelly," the substance has continued to cause maintenance problems in such places as aircraft wing tanks and fuel system sumps and filter separator vessels of both fixed fuel distribution systems and refueling vehicles.

The Southwest Research Institute (SwRI) believes that the term apple jelly dates back to around the middle 1980s, when a presentation to a subcommittee of the ASTM (American Standards of Testing and Materials) referred to a contaminant found in the Alberta Products Pipeline (APPL) as "APPL jelly." Since that time, the name has been applied to a range of contaminants found in aviation fuel-delivery systems.

Last year the federal agency responsible for procuring and distributing fuel to the Department of Defense, the Defense Energy Support Center (DESC), asked the SwRI to determine what apple jelly was, how it formed, and how it can be prevented or reduced. SwRI headed a research team that included Consulting for Energy Efficiency and Environmental Excellence (C4e) and Martin & Associates to conduct 31 onsite military base visits and examine 139 samples of apple jelly, fuel, and other types of samples related to apple jelly contamination. SwRI provided project leadership, laboratory analyses, and chemistry expertise, while C4e offered expertise on USAF fuel-handling procedures, relevant past experience, and contacts at USAF installations. Martin & Associates provided knowledge of DESC procedures and helped gather information from DESC databases.

Earlier this year the team of researchers submitted to the DESC a 210-page report in which they detail how apple jelly is caused by diethylene glycol methyl ether (DiEGME) interacting with water and other fuel-system contaminants. DiEGME is an anti-icing inhibitor added to JP-8 jet fuel to prevent free water in a plane's fuel system from freezing at high altitudes.

"After DiEGME joins with water, it forms a very aggressive solvent," said Steve Westbrook, Manager of the Petroleum Products Technology section in SwRI's Engine and Vehicle Research Division. "When added to the fuel, DiEGME combines with free water and then reacts with dirt, rust, paint, fuel components, elastomers, and other contaminants in pipelines and fuel storage tanks. When this blend reacts with polyacrylate polymers used to manufacture water-absorbing fuel filters used in some military fuel-handling systems, it forms the thick, gooey, sticky substance known as thick apple jelly."

To aid in preventing contamination, SwRI recommended improved fuel-handling procedures and facilities designed to remove water from the fuel-distribution system and to ensure the proper mixing of additives to the fuel.

- Jean L. Broge