Two types of prediction tools for helicopter noise have been developed under the cooperative research between Advanced Technology Institute of Commuter Helicopter Ltd. (ATIC) and National Aerospace Laboratory (NAL) . One of them is a combined method of CAMRAD II, interpolation code for blade motion and wake geometry, aerodynamic code of 3D unsteady Euler solver, and aeroacoustic code based on Ffowcs Williams and Hawkings (FW-H) formulation. The other consists of CAMRAD II, 3D unsteady Euler solver using moving overlapped grid method, and FW-H code. The acoustic waveform of Blade-Vortex Interaction (BVI) noise predicted by the former tool is in good agreement with the experimental data of 1/7-scale model AH-1 Operational Loads Survey (OLS) rotor. This method is applied to investigate the effect of blade-tip shape on the intensity of BVI noise. As a result, it is shown that anhedral and swept-forward tip shapes effectively reduce the BVI noise of OLS rotor in a descent flight condition. The predicted Effective Perceived Noise Level (EPNL) of a helicopter is also compared with the experimental data obtained by ATIC and reasonable correlation is obtained. The latter tool successfully predicts the distinct spikes in the BVI wave-form of ATIC model rotor tested in German-Dutch Wind Tunnel (DNW) . In the comparison of measured and calculated carpet noise contours, reasonable agreement is obtained. The present tools are expected to be useful for the design of low-noise helicopters in the future.
The common theme of Shipping industry is to detect abnormal condition of the diesel engine in an early stage and to prevent it from vital accidents for increasing the Safety and the Operation rate of the ship. Although various abnomal condition diagnosis devices have been developed up to the present, in all cases, temperatures and pressures of various parts of the engine are detected and engine performance is estimated and the abnormal condition diagnosis is performed by the Artificial intelligence (A1), Therefore, the accuracy of abnomal condition diagnosis is not always satisfactory. For the analysis of egine operating performance, the combustion analysis system, etc., have also been developed Howerver, at present, these systems are not fit for actual circumstance from the point of view of sensor's durability, etc. In case of the diesel engine as Gas pressure in cylinder will act on the crankshaft via the piston and connecting rod and is converted into Torque. In this paper, the author would like to introduce way of the abnormal condition diagnosis which by the observation of Torque fluctuations (Torsion angles) of the crankshaft. We put a detecting device for the crankshaft torsion angles to the test, and validated that approach.
Close-fitting acoustical enclosure is an effective technique for reducing sound radiation. But, the reduction level is sometimes far from expectation at design stage. This paper describes a new concept for the closefitting enclosure as well as some examination on characteristics of that of present engines. The concept is as follows; air is fully enclosed, vibration of mounting point is minimized by high rigidity of engine block design. Effectiveness of the concept is shown by both exciter test and running engine test.
Recently, the regulation related to noise and vibration in general life shows a tendency of becoming strict, and it is not an exception about vessels as well. It is an important problem to make noise and vibration reduce in the case of vessels. Because vessels have crew's workplace and living accommodation in the same hull, it has the possibility that noise and vibration have a bad influce to precise machines and crew's residence environment. When the training vessel GINGA MARU was constructed in 1973, main diesel generators in her did not have soundproof and anti-vibration measures. So crew have been badly affected by noise and vibration. We considered an anti-vibration measure to main diesel genrators, and constructed the consideration on March in 1998 We analyzed the change concerning noise and vibration befor and after this construction, and could verify the effct of this construction. As a result, it could reduce noise and vibration under 1000Hz in the vessel's living accommodation. And noise in the vessel had a cuse in not only noise which was caused by main diesel generators but also their vibration, moreover it could show a correlation in both frequency.