Calculation of the Unsteady Flow in Exhaust Pipe Systems: New Algorithm to Fulfil the Conservation Law in Pipes with Gradual Area Changes

Abstract

In this paper a new calculation method is proposed for the gasflow in tapered pipes. The model is adapted to the hybrid method of characteristics. The key idea of the model is to concentrate any area change over one mesh length in the mesh points instead of using an area gradient along the characteristic lines. The model has the disadvantage that the computing time increases, but it has the great advantage that the law of conservation of mass is fulfilled for the whole pipe length, even for important area changes. This allows the other advantages of the method of characteristics to be retained, for example the treatment of discontinuities in temperature or gas composition, without compromising the mass balance of the engine. In a test case it is shown that the new model correctly predicts the massflowrate at all mesh points, which is not the case for the original hybrid method or other adapted versions. Tests for a real engine situation give results for the conservation of mass that are comparable with the best results of the Lax-Wendroff method. a a, C06290 0 IMechE 1991 0954-4062/91 $2.00 + .05

Analysis of numerical methods to solve one-dimensional fluid-dynamic governing equations under impulsive flow in tapered ducts

“…By the late 80s and early 90s, these authors used the two-step LW scheme as an alternative code to the traditional mesh-method of characteristics [24]. During these years, Van Hove and Sierens [25] were still working on the method of characteristics and proposed some modifications in order to increase its accuracy with tapered ducts. Also at that time, Blair [26] presented a new computational scheme to solve the flow through engine pipes, which considered the effect of high particle velocity flow separation in tapered ducts.…”

Thermodynamic modelling of complete engine systems—a review

“…Payri et al [50] improved the entropy/path line tracking (mesh method) of the non-homentropic MOC and obtained better results in the calculation of flow in the manifolds. The mass conservation of the MOC for flows through a section with gradual area change was improved by Hove and Sierens [51]. Although such efforts improved the results, the complexity of the model and also execution times are increased.…”