Quantitative Computational Fluid Dynamics Analyses of Particle Deposition on a Transonic Axial Compressor Blade—Part I: Particle Zones Impact

Abstract

Solid particle ingestion is one of the principal degradation mechanisms in the turbine and compressor sections of gas turbines. In particular, in industrial applications, the microparticles that are not captured by the air filtration system cause fouling and, consequently, a performance drop of the compressor. This paper presents three-dimensional numerical simulations of the microparticle ingestion (0 μm–2 μm) on an axial compressor rotor carried out by means of a commercial computational fluid dynamic (CFD) code. Particles of this size can follow the main air flow with relatively little slip, while being impacted by flow turbulence. It is of great interest to the industry to determine which areas of the compressor airfoils are impacted by these small particles. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separate from the continuous phase. Then, the NASA Rotor 37 is considered as a case study for the numerical investigation. The compressor rotor numerical model and the discrete phase treatment have been validated against the experimental and numerical data available in literature. The number of particles, sizes, and concentrations are specified in order to perform a quantitative analysis of the particle impact on the blade surface. The results show that microparticles tend to follow the flow by impacting at full span with a higher impact concentration on the pressure side (PS). The suction side (SS) is affected only by the impact of the smaller particles (up to 1 μm). Particular fluid dynamic phenomena, such as separation, stagnation point, and tip leakage vortex, strongly influence the impact location of the particles.

Quantitative computational fluid dynamic analyses of oil droplets deposition on vaneless diffusor walls of a centrifugal compressor

“…The particle mass concentration term C DPM models the contaminant concentration on surfaces very close to the diffusor, defined as kg/m 3 . Although there is an accretion rate provided by the software, the trap condition on the diffusor surface implies unrealistic values of this quantity, in contrast to those obtained from experimental tests reported by Parker and Lee . In particular, the new surfaces were positioned at a constant distance of 20 μm from the diffusor on each side.…”

“…The fouling phenomena of the compressor are due to the adherence of substances (liquid and/or solid) on the compressor surfaces, which progressively alter both the shape and roughness of the surface. These phenomena can be described by the following three phases: (a) transport of the particles (discrete phase) by the air (continuum phase), (b) contact and adhesion of the first discrete phase (particle) with the surface, and (c) repeated adhesion of the following particles on those previously deposited on the surface …”

“…One reason is that the effect of Brownian motion can be optionally included in the term of for submicron particles, and in some calculation cases, the particle diameters are larger than 1 μm. The other reason is that the Brownian force is intended only for laminar simulation and the flow in the compressor should be turbulent . When the velocity gradient exists in the flow field, the particles in the flow field suffer from the lift force, even if the particles are not rotated .…”

“…Of the studies concerning fouling in turbomachinery, few studies have been done about the vehicle compressor, but much research has been conducted on the aero‐engine, marine engine, and industrial gas turbine engine . Most of these studies examined turbocharger deposition using the methods of increasing the thickness of the blade, increasing the wall roughness, and changing the local area geometry.…”

“…The research indicated that fouling may cause a drop in airflow, pressure ratio, compressor efficiency, and compressor performance, resulting in a “rematching” between the gas turbine and compressor, and a subsequent drop in power output and thermal efficiency . The fouling phenomenon in the compressor was caused by many factors, such as the number of particles, particle diameters, particle mass concentration, patterns of particle distribution, and particle mass flow rate . Meanwhile, the design parameters of the axial compressor also influenced the process of fouling formation, such as axial compressor chord length, solidity, roughness, and the number of stages .…”