METHODOLOGY FOR REFINEMENT OF HYDRAULIC LOSSES IN THE DESIGN OF ADDITIVELY MANUFACTURED LIQUID ROCKET ENGINES

Abstract

The paper addresses the issue of accounting for hydraulic losses in the cooling channel of a liquid rocket engine (LRE) manufactured using the additive technology Laser Powder Bed Fusion (L-PBF).  The purpose of the study is to develop a methodology that allows, at the preliminary design stage, to determine the influence of additive manufacturing features on coolant flow parameters and to ensure optimal thermal conditions for the combustion chamber operation. To achieve this goal, numerical simulation, analytical calculations, and comparative analysis of data obtained using «Астра», SolidWorks, and Wolfram Mathematica software were carried out. The proposed calculation algorithm is based on determining the roughness of the internal channel surfaces formed during the layer-by-layer metal powder printing process, which results in the so-called “staircase effect”. It is proposed to consider the influence of channel geometry variations and their inclination relative to the build axis on the surface roughness and the equivalent hydraulic diameter. The obtained results show that the use of additive technologies increases the roughness of cooling channels on average up to 10–130 μm, which leads to higher hydraulic losses and requires an increase in coolant inlet pressure to the chamber. For verification, a comparison between the developed model and the hydraulic calculation methodology was performed using numerical simulation in SolidWorks. The calculation error of 0.16 bar (up to 11%) confirms the correctness of the proposed approach. The theoretical significance of the work lies in the development of an approach for accounting the influence of surface roughness caused by additive manufacturing in the hydrodynamic design of LREs. The practical significance lies in the possibility of using the results to improve the accuracy of design calculations and to reduce the risk of combustion chamber overheating. The originality of the study consists in combining the analysis of additive manufacturing technological characteristics with the calculation of hydraulic losses, which has not previously been considered in engineering methodologies. Further experimental validation of the proposed methodology and its extension to various propellant combinations and cooling schemes are required.