Study on oil-cooler location for a pusher type turbo prop aircraft using numerical simulation

Abstract

Purpose Pusher configured turbo-prop aircraft receive inadequate ram air cooling due to the lack of propeller slipstream, particularly during ground operations. However, flow entrainment can be exploited to a greater extent by placing the oil-cooler duct close to downstream of the propeller at a suitable radial location. But this method has a detrimental effect on the propeller thrust. The purpose of this paper is to discuss the results of numerical simulations carried out to simulate the performance of the propeller with and without oil cooler. Design/methodology/approach In this paper, three-dimensional (3D) numerical simulations are carried out to simulate the propeller in a rotating domain using an unstructured grid. A computational fluid dynamics solver is put forward to analyze the effect of thrust loss by solving 3D Navier-Stokes equations using a second-order upwind finite-volume scheme. In this study, the impact of thrust loss incurred in the propeller flow field with and without oil cooler duct for three different locations at various rotational speeds is carried out to assess the propeller performance and to identify the optimum position to get a sufficient mass flow rate. Findings The findings from this study are simulated thrust values of an uninstalled five-bladed propeller of light transport aircraft (LTA) match well with original equipment manufacturer propeller thrust data. The tip speed velocities simulated for different operating conditions are in good agreement with the theoretical calculations. The influence of oil-cooler effect on the propeller flow field is less in low velocity to high-velocity operating condition due to flow transition from laminar to turbulent. The presence of the oil cooler, which influences the thrust loss, is studied at propeller upstream and downstream locations in detail for 30%, 40% and 50% of propeller radius cases. Research limitations/implications Simulations with finer and structured hexa grids can be applied to this problem to get closer results and save solver time as future work. Practical implications The recommended system is installed in the production standard aircraft of LTA. After installation oil cooler performance is better compared to the previous arrangement. Originality/value Research work about pusher aircraft is very limited. The problem addressed in this study is unique which resolves the major issue of pusher aircraft. This work highlights the difficulty involved in LTA engine oil cooling, and solution methodologies are also provided. Numerical simulation with oil-cooler assembly is a new area of research that gave the solution for this oil-cooling issue through various oil-cooler case studies.