Aeroacoustic effects of reduced aft tip speed at constant thrust for a model counterrotation turboprop at takeoff conditions

A model high-speed, advanced counterrotation propeller, F7/A7, was tested in the anechoic wind tunnel at simulated takeoff and approach conditions of Mach 0.2. The propeller was operated in a baseline configuration with the forward and aft rotor blade setting angles and forward and aft rotational speeds essentially equal. Two additional configurations were tested with the aft rotor at increased blade setting angles and the rotational speed reduced to achieve overall performance similar to that of the baseline configuration. Acoustic data were taken with an axially translating microphone probe that was attached to the tunnel floor. Concurrent aerodynamic data were taken to define propeller operating conditions

Noise of a model counterrotation propeller with simulated fuselage and support pylon at takeoff/approach conditions

Two modern high-speed advanced counterrotation propellers, F7/A7 and F7/A3 were tested in the NASA Lewis Research Centers's 9- by 15-foot Anechoic Wind Tunnel at simulated takeoff/approach conditions of 0.2 Mach number. Both rotors were of similar diameter on the F7/A7 propeller, while the aft rotor diameter of the F7/A3 propeller was 85 percent of the forward propeller to reduce tip vortex-aft rotor interaction. The two propellers were designed for similar performance. The propellers were tested in both the clean configuration, and installed configuration consisting of a simulated upstream nacelle support pylon and fuselage section. Acoustic measurements were made with an axially translating microphone probe, and with a polar microphone probe which was fixed to the propeller nacelle and could make both sideline and circumferential acoustic surveys. Aerodynamic measurements were also made to establish propeller operating conditions. The propellers were run at blade setting angles (fron angle/rear angle) of 41.1/39.4 deg for the F7/A7 propeller, and 41.1/46.4 deg for the F7/A3 propeller. The forward rotors were tested over a range of tip speeds from 165 to 259 m/sec (540 to 850 ft/sec), and both propellers were tested at the maximum rotor-rotor spacing, based on pitch change axis separation, of 14.99 cm (5.90 in.). The data presented in this paper are for 0 deg propeller axis angle of attack. Results are presented for the baseline, pylon-alone, and strut + fuselage configurations. The presence of the simulated fuselage resulted in higher rotor-alone tone levels in a direction normal to the advancing propeller blade near the fuselage. A corresponding rotor-alone tone reduction was often observed 180 deg circumferentially from this region of increased noise. A significant rotor-alone increase for both rotors was observed diametrically opposite the fuselage. In some cases, interaction tone levels were likewise affected by the simulated installation

Acoustic Performance of the GEAE UPS Research Fan in the NASA Glenn 9- by 15-Foot Low-Speed Wind Tunnel

A model advanced turbofan was acoustically tested in the NASA Glenn 9- by 15-Foot Low-Speed Wind Tunnel in 1994. The Universal Propulsion Simulator fan was designed and manufactured by General Electric Aircraft Engines, and included an active core, as well as bypass, flow paths. The fan was tested with several rotors featuring unswept, forward-swept and aft-swept designs of both metal and composite construction. Sideline acoustic data were taken with both hard and acoustically treated walls in the flow passages. The fan was tested within an airflow at a Mach number of 0.20, which is representative of aircraft takeoff/approach conditions. All rotors showed similar aerodynamic performance. However, the composite rotors typically showed higher noise levels than did corresponding metal rotors. Aft and forward rotor sweep showed at most modest reductions of transonic multiple pure tone levels. However, rotor sweep often introduced increased rotor-stator interaction tone levels. Broadband noise was typically higher for the composite rotors and also for the aft-swept metal rotor. Transonic MPT generation was reduced with increasing fan axis angle of attack (AOA); however, higher downstream noise levels did increase with AOA resulting in higher overall Effective Perceived Noise Level

Doing Deals in Japan: An Analysis of Recent Trends & Developments for the U.S. Practitioner

This article examines the process which is currently being played out in Japan by: (i) analyzing the recent changes in Japanese law of relevance to M&A deals, (ii) discussing some recent contested deals in Japan that may shed some light on current market practices, and (iii) providing an overview of the key issues that a U.S. practitioner will likely face when working on a Japanese deal…A good starting point in better understanding the remarkable changes in the Japanese M&A markets is to review the recent amendments to Japanese law, certain policy initiatives by the functional regulators, and other guidelines issued by Japanese government agencies… In concert with the changes in Japanese law, we have seen an increase in the number of contested deals in Japan in recent years…[T]he challenge for the U.S. practitioner is to boil down the complexity of Japanese M&A to a list of key issues that should be reviewed in any transaction which involves Japanese entities…[W]e have set forth some of the main issues under Japanese law and U.S. securities laws that have often come into play in Japanese deals…The current Japanese M&A market presents opportunities for U.S. companies and their advisors that are arguably the most promising in recent history…[G]iven the challenges posed by the opportunities in the Japanese M&A market, the importance of well informed and considered decision-making will be essential in order to ensure that U.S. companies compete and succeed in doing Japanese deals

Aeroacoustic Analysis of Fan Noise Reduction With Increased Bypass Nozzle Area

An advanced model turbofan was tested in the NASA Glenn 9-by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) to explore far field acoustic effects of increased bypass nozzle area. This fan stage test was part of the NASA Glenn Fan Broadband Source Diagnostic Test, second entry (SDT2) which acquired aeroacoustic results over a range of test conditions. The baseline nozzle was sized to produce maximum stage performance at cruise condition. However, the wind tunnel testing is conducted near sea level condition. Therefore, in order to simulate and obtain performance at other operating conditions, two additional nozzles were designed and tested one with +5 percent increase in weight flow (+5.4 percent increase in nozzle area compared with the baseline nozzle), sized to simulate the performance at the stage design point (takeoff) condition, and the other with a +7.5 percent increase in weight flow (+10.9 percent increase in nozzle area) sized for maximum weight flow with a fixed nozzle at sea level condition. Measured acoustic benefits with increased nozzle area were very encouraging, showing overall sound power level (OAPWL) reductions of 2 or more dB while the stage thrust actually increased by 2 to 3 percent except for the most open nozzle at takeoff rotor speed where stage performance decreased. Effective perceived noise levels for a 1500 ft engine flyover and 3.35 scale factor showed a similar noise reduction of 2 or more EPNdB. Noise reductions, principally in the level of broadband noise, were observed everywhere in the far field. Laser Doppler Velocimetry measurements taken downstream of the rotor showed that the total turbulent velocity decreased with increasing nozzle flow, which may explain the reduced rotor broadband noise levels

Some Inconvenient Truths About Climate Change Policy: The Distributional Impacts of Transportation Policies

Instead of efficiently pricing greenhouse gases, policy makers have favored measures that implicitly or explicitly subsidize low carbon fuels. We simulate a transportation-sector cap & trade program (CAT) and three policies currently in use: ethanol subsidies, a renewable fuel standard (RFS), and a low carbon fuel standard (LCFS). Our simulations confirm that the alternatives to CAT are quite costly—2.5 to 4 times more expensive. We provide evidence that the persistence of these alternatives in spite of their higher costs lies in the political economy of carbon policy. The alternatives to CAT exhibit a feature that make them amenable to adoption|a right skewed distribution of gains and losses where many counties have small losses, but a smaller share of counties gain considerably—as much as $6,800 per capita, per year. We correlate our estimates of gains from CAT and the RFS with Congressional voting on the Waxman-Markey cap & trade bill, H.R. 2454. Because Waxman-Markey (WM) would weaken the RFS, House members likely viewed the two policies as competitors. Conditional on a district's CAT gains, increases in a district's RFS gains are associated with decreases in the likelihood of voting for WM. Furthermore, we show that campaign contributions are correlated with a district's gains under each policy and that these contributions are correlated with a Member's vote on WM.Institute of Transportation Studies at UC Davi

Strategic Policy Choice in State-Level Regulation: The EPA's Clean Power Plan

The EPA's Clean Power Plan sets goals for CO₂ emissions rate reductions by 2030 that vary substantially across states. States can choose the regulatory mechanism they use and whether or not to join with other states in implementing their goals. We analyze incentives to adopt rate standards versus cap-and-trade with theory and simulation. We show conditions where adoption of inefficient rate standards is a dominant strategy from both consumers' and generators' perspectives. Numerical simulations of the western electricity system highlight incentives for uncoordinated policies that lower welfare and increase emissions relative to coordination

Cosmic Ray Acceleration at the Forward Shock in Tycho's Supernova Remnant: Evidence from Chandra X-ray Observations

We present evidence for cosmic ray acceleration at the forward shock in Tycho's supernova remnant (SNR) from three X-ray observables: (1) the proximity of the contact discontinuity to the forward shock, or blast wave, (2) the morphology of the emission from the rim of Tycho, and (3) the spectral nature of the rim emission. We determine the locations of the blast wave (BW), contact discontinuity (CD), and reverse shock (RS) around the rim of Tycho's supernova remnant using a principal component analysis and other methods applied to new Chandra data. The azimuthal-angle-averaged radius of the BW is 251". For the CD and RS we find average radii of 241" and 183", respectively. Taking account of projection effects, we find ratios of 1:0.93:0.70 (BW:CD:RS). We show these values to be inconsistent with adiabatic hydrodynamical models of SNR evolution. The CD:BW ratio can be explained if cosmic ray acceleration of ions is occurring at the forward shock. The RS:BW ratio, as well as the strong Fe Ka emission from the Tycho ejecta, imply that the RS is not accelerating cosmic rays. We also extract radial profiles from ~34% of the rim of Tycho and compare them to models of surface brightness profiles behind the BW for a purely thermal plasma with an adiabatic shock. The observed morphology of the rim is much more strongly peaked than predicted by the model, indicating that such thermal emission is implausible here. Spectral analysis also implies that the rim emission is non-thermal in nature, lending further support to the idea that Tycho's forward shock is accelerating cosmic rays.Comment: 39 pages, 10 figures, accepted by Ap