Experimental study on the acoustic roughness spectrum of high-speed railway rails

Purpose–This study aims to investigate the acoustic roughness of rails on China’s high-speed railways,with a focus on short-wavelength irregularities(less than 80 cm),which are known to significantly contribute to noise.The goal is to develop a specific acoustic roughness spectrum tailored for China’s high-speed railway system,as no such spectrum currently exists.Design/methodology/approach–A long-term tracking study was conducted on major railway lines in China,monitoring rail roughness throughout the initial operational period and the rails’service life.Data preprocessing techniques such as peak removal and curvature correction were applied for acoustic adjustments.A spatial-wavelength domain transformation was performed,providing the distribution patterns and statistical characteristics of acoustic roughness on China’s high-speed rails.Based on these analyses,a model for constructing the acoustic roughness spectrum was developed.Findings–The study found that the acoustic roughness of China’s high-speed railway rails follows aχ2 distribution with six degrees of freedom.For wavelengths greater than 8 cm,the acoustic roughness spectrum remains below the ISO specified limits.In the wavelength range of 3.2 cm to 6.3 cm,the roughness is comparable to or within the limits specified by ISO 3095:2005 and ISO 3095:2013.However,for wavelengths shorter than 2.5 cm,the roughness exceeds ISO limits.Originality/value–This research fills the gap in the lack of a specific acoustic roughness spectrum for China’s high-speed railways.By establishing a tailored spectrum based on long-term data analysis,the findings provide valuable insights for noise control and rail maintenance in the context of China’s high-speed rail system.

The Impact of Key Factors on Flow Characteristics of 14 MW Reverse-Swirl Pulverized Coal Burner

Reverse-swirl(RS)burner which has been industrialized couples reverses jet and swirl flow for the stabilization of flame.Using Dantec multichannel constant-temperature anemometer,experiments on airflow characteristics were implemented on a 1:2 scaled burner model with different values in terms of reverse primary air(RPA)ratio and swirl inner secondary air(SISA)ratio.It was found that the shape of annular coupled recirculation zone(ACRZ)had stayed symmetrical all the time.The RPA ratio was the main factor that had an impact on the values of axial and RMS velocity as well as the radial velocity direction of ACRZ.Both RPA ratio and SISA ratio had a great impact on the area of ACRZ,relative reverse flow rate,mixing between SISA and outer secondary air(OSA)as well as swirling ability of the airflow.The area of ACRZ reached its peak when the RPA ratio was 11.92%or SISA ratio was 17.03%;however,when the RPA ratio and SISA ratio reached 14.86%and 28.41%respectively,the combination of RPA and SISA became relatively favorable;besides,ACRZ area,relative reverse flow and swirling ability became suitable and the mixing between SISA and OSA was relatively delayed.The research was of great practical and theoretical importance to the design and operation of RS burner.