Performance prediction of air drag brake units for Shinkansen and verification by running test

Abstract

The performance of Air Drag Brake (ADB) units for Shinkansen trains was predicted using wind tunnel experiments and numerical analysis, and running tests were carried out using a test car equipped with a number of ADB units. First, A large scale wind tunnel experiment was carried out with 20 ADB models. The models were 1/4 scale and placed in a staggered pattern on both sides of a car. The drag reduction ratio k at the downstream ADB models was investigated. It was found that k increased logarithmically as the non-dimensional flow distance increased, and then converged to a constant value of K=0.5. Secondly, computational fluid analysis was carried out using a LES method, with 56 ADB models arranged on the roofs of the middle four cars of a six-car train. As a result, the drag reduction ratio k for ADB models 1st to 14th on the leading car were generally the same as in the analysis and experiment. The total drag force obtained in ADB models with eight cars was estimated to be D_sum = 48.3D₁ (where D₁ is the drag force of the leading ADB model). Finally, the total drag force of the ADB units was verified by running the test car equipped with 92 ADB units. As a result, the total drag force of the ADB units was 106.7 kN at a speed of 360 km/h in a tunnel section, and the ratio D_sum /D₁ = 49.5 was approximately the same as that of the numerical analysis. Therefore, it was confirmed that the total drag force of the ADB units predicted by CFD could be achieved in a real train.