The analysis of the performance losses of a multistage compressor concerning the air contaminant is not widespread in literature and, the mutual interactions of particle materials, air humidity, and compressor load are not well studied. The airborne micrometric particles that enter the compressor can deposit on the internal surfaces, causing the loss of performance of the machine. In this paper, several experimental tests have been carried out on a multistage compressor unit. A detailed analysis has been carried out considering soil and soot ingestion, as well as the air relative humidity (RH) (ranging from 50% RH to 80% RH) and compressor rotating velocity. Several combinations of particle diameter, material, and operating conditions have been considered. The amount of contaminant at the compressor outlet has been measured and the capture efficiency of the whole machine has been determined. Over the exposure time, the capture efficiency ranges from 0.2 to 0.6 according to the powder type and compressor inlet conditions. The capability of the compressor to collect particles changes over time as a function of the condition, even if several tested cases appear characterized by an almost constant capture efficiency trend. In addition, the performance degradation has been monitored over time and, with the reference of the particle concentration, the present experimental campaign covers about 500 operating hours of an actual installation. After a detailed evaluation of experimental uncertainty, the performance losses due to particle contamination have been assessed. The losses in the compressor performance have been estimated by means of the pressure ratio of the axial stages. The maximum degradation has been estimated equal to 0.53%/h for the compressor pressure ratio. Soot particles appear stickier, especially in the presence of higher humidity and represent the most detrimental operating conditions for the compressor unit.

Compressor fouling is one of the main causes of gas turbine performance degradation. Microsized particles adhere to the blade surfaces increasing the surface roughness and modifying the airfoil shape. In this work, the contamination of the Allison 250 C18 multistage compressor engine with four sorts of micrometric dust has been provided. The tests were performed changing the relative humidity (RH) at the compressor inlet and the unit rotational speed. After each test, a photographic inspection of the internal fouled parts has been realized and the digital pictures have been analyzed employing an image processing package. The deposit's build-up of stator vanes and rotor blades has been postprocessed and the most affected regions of each compressor stage have been highlighted. Besides, a numerical simulation of the machine has been performed. The numerical flow field has been used to highlight the blade regions, which show the most favorable conditions for particle deposition. A theoretical model has been applied to the flow field to simulate the particle deposition. The combination of the deposition model with the results of the numerical simulations gives the chance to better understand the experimentally founded deposition patterns. Those results have been finally compared to the pictures of the patterns. The possibility to detect and measure the deposition patterns on a rotating test rig and the comparison with models and experiments gave the possibility to assess in detail the particle deposition phenomenon on a multistage axial compressor flow path.

Surface material loss due to erosive wear is responsible for the increased cost of maintenance and downtime in industries. Hence, hardfacing is one of the most valuable and effective techniques employed to improve the wear resistance of heavy-duty components. The present paper investigates the microstructural and erosive wear characteristics of a hypereutectic high-chromium cast iron, considering the erosion resistance, resulting from the impact of micro-sized particles, of both as-received and heat-treated conditions. Micro-sized particles involve the erosion-resistant characteristics of carbide and matrix, contemporary. Due to this, the enhancement of the matrix strength could improve the mechanical support to withstand cracking deformation and spalling. Accordingly, the effect of a destabilization heat treatment on the microstructure was firstly investigated by hardness tests, X-ray diffraction analyses, optical and scanning electron microscopy. Specifically designed erosive tests were carried out using a raw meal powder at an impingement angle of 90°. The resulting superior wear resistance of the heat-treated samples was relayed on the improved matrix microstructure: consistent with the observed eroded surfaces, the reduced matrix/carbides hardness difference of the heat-treated material is pivotal in enhancing the erosion resistance of the hardfacing. The present results contribute to a better understanding of the microstructure–property relationships concerning the erosive wear resistance.

Land-based power units have to fulfill even more high levels of production and reliability. In harsh environments (desert and tropical installations, typically), the power unit ingests high amounts of dust that might deposit inside the compressor. In this paper, the analysis of a multistage compressor performance that operates under sandy and humid conditions has been assessed. The compressor units, which equips the Allison 250 C18 compressor, has been subjected to multiple runs under severe conditions of soil dust ingestion. The compressor has been operated according to subsequent runs, and at the end of each run, the performance curve was recorded; the performance losses, in terms of pressure ratio, have been measured during the operations. The characteristic curve of each run is representative of the level of contamination of the unit. Finally, the compressor has been washed, and the performance curve, in the recovered conditions, has been recorded. The results show the modification and the downward shift of the characteristic curves which lead to a gradual loss of the compressor performance. The curves realized after dust ingestion have been compared with the recovered curve after online washing. The measurement shows a promising recovery of the performances, even if the compressor flow path appears affected by localized deposits able to resist to the droplet removal action. Detailed photographic reports of the inlet guide vane (IGV) and the first compressor stages have been included in this analysis. After each run, the IGV, the rotor blade and stator vane of the first stage, and the hub and the shroud surfaces have been photographed. The pictures show the deposition patterns on the blades and the compressor surfaces. The comparison of the pictures of the internal surfaces, before and after the washing, highlights the parts that are more critical to clean and needy of attention during offline washing and overhaul.

Helicopters often operate in dusty sites, ingesting huge amounts of contaminants during landing, take-off, hover-taxi, and ground operations. In specific locations, the downwash of the rotor may spread soil particles from the ground into the environment and, once ingested by the engine, may stick to the compressor airfoils. In the present work, the Allison 250 C18 engine’s multistage axial-flow compressor is employed to study the fouling rate on rotor blades and stator vanes from both numerical and experimental standpoints. The compressor is operated in a typical ground-idle operation, in terms of the rotational regime and contaminant concentration, in laboratory-controlled conditions. The mass of deposits is collected from the airfoil surfaces at the end of the test and compared to that estimated through the numerical model. The experimental test shows that the airfoils collect almost 1.6% of the engine’s total mass ingested during a ground-idle operation. The capability of numerical methods to predict the fouling rate on the rotating and stationary airfoils of a multistage compressor is tested through the implementation of literature based deposition models. Sticking models show a good agreement in terms of the relative results; nevertheless, an overestimation of the deposited mass predicted is observed.

Biomass represents a programmable renewable energy source that is useful for reducing issues related to the transfer from fossil fuels to the renewable energy era. The exploitation of biomass is strongly related to the development of power technologies that are designed to improve efficiency; however, at the same time, they have to be designed to improve the life cycle of the entire installation—especially in relation to maintenance operations. In this paper, a numerical analysis is proposed to assess the performance of a heat exchanger used for separating condensing tar from syngas generated by the gasification of lignocellulosic wood chips and pellets. The analysis included clean, fouled, and clogged conditions. Flow maldistribution characterized the inlet section of shell-and-tube configurations and was responsible for clogging phenomena. Starting from field detection, analyses of fouled and clogged conditions showed a reduction in the effectiveness of the heat exchanger, causing dangerous conditions for the internal combustion engine used to exploit the syngas flow.