The evaluation of propulsion systems used in UAVs is of paramount importance to enhance the flight endurance, increase the flight control performance, and minimize the power consumption. This evaluation, however, is typically performed experimentally after the preliminary hardware design of the UAV is completed, which tends to be expensive and time-consuming. In this paper, a comprehensive theoretical UAV propulsion system assessment is proposed to assess both static and dynamic performance characteristics via an integrated simulation model. The approach encompasses the electromechanical dynamics of both the motor and its controller. The proposed analytical model estimates the propeller and motor combination performance with the overarching goal of enhancing the overall efficiency of the aircraft propulsion system before expensive costs are incurred. The model embraces an advanced blade element momentum theory underpinned by the development of a novel mechanism to predict the propeller performance under low Reynolds number conditions. The propeller model utilizes XFOIL and various factors, including post-stall effects, 3D correction, Reynolds number fluctuations, and tip loss corrections to predict the corresponding aerodynamic loads. Computational fluid dynamics are used to corroborate the dynamic formulations followed by extensive experimental tests to validate the proposed estimation methodology.

Centrifugal water pumps account for more than 20% of energy use all over the world. Even a little increase in centrifugal pump operating efficiency may result in billions of dollars in savings each year and help reduce carbon dioxide emissions. This study creates a design tool that integrates one-dimensional equations and computational fluid dynamics (CFD) simulations to design centrifugal pump impellers. This examines different combinations of design factors by utilizing both the powerful numerical tools that allow the modeling of numerous scenarios and the large number of empirical equations and coefficients that represent the significant knowledge accumulated in this field. The design tool runs through a series of equations to select the beginning candidates for the different impeller design variables. After that, a design space is established by generating upper and lower bounds for each design variable. The CFD tool executes numerous scenarios inside the design space in order to find the best candidates with the maximum operating efficiency and meet the design objectives. A low specific speed centrifugal pump with a semi-open impeller is used as a case study. The design tool is successful in designing it, fulfilling the design requirement, and increasing operational efficiency when compared to a simple single-arc comparable impeller.

The effect of impeller blades shape modification on the centrifugal pump performance has been investigated numerically. Impeller blades’ shape have been modified by new technique called “bladelet”. This technique has been called the “bladelet” after the name of the aeroplane winglet because of the great similarity between them in shape and function. The shapes of the blade trailing edge greatly affect the performance of the turbomachines. So, the purpose of the blade tilting (bladelet) is to decrease the recirculating flow at the pump trailing edge due to the high pressure difference and enhance the hydraulic performance of the centrifugal pump. The bladelet technique has two main geometrical parameters: radial position R_BL and bladelet inclination angle θ_BL. 3-D validated numerical simulation model has been carried out using commercial software, ANSYS^® CFX, to study the effect of the bladelet technique and its different parameters on the pump performance at different flow rates. In this study nine cases with different bladelet parameters have been numerically simulated in order to check its effect on the centrifugal pump performance. These nine cases have been chosen by considering the geometrical constrain of the bladelet parameters. The results of these nine cases have been compared with the basic impeller (the same impeller but without bladelet) at the same operating condition in order to discuss the effect of the bladelet parameters variation on the centrifugal pump performance. It was found that the use of the bladelet technique decrease the pressure difference between the pressure and the suction side at the blade trailing edge. This decrease in pressure difference at the blade trailing edge decreases the flow recirculation at the impeller outlet from pressure side to suction side. Also, bladelet technique improves the hydraulic efficiency at the part-load operating zone. In addition, the bladelet has a regression effect on the pump head for some cases with high inclination angle and low radial position. However, the bladelet technique increases the impeller blades’ overlap.

Hybrid rocket engines offer inherent safety and throttling by separating fuel and oxidizer, yet their wider use is hindered by low fuel regression rates and by combustion instabilities that frequently accompany performance-enhancing additives. This paper presents an experimental framework in which these two aspects are assessed separately on a single dataset. A campaign of 31 firings was conducted on paraffin-based fuels doped with carbon black (PC, 1 wt%), conventional micron-aluminum (PA, 14 wt%), and activated nano-aluminum (PAA, 14 wt%), all burned with gaseous oxygen. A covariate-adjusted equivalence analysis (ANCOVA with $$\log (G)$$ as covariate) over the tested flux range (31–71 kg/m $$^2\cdot$$ s) indicates that the three fuels are practically equivalent on average , with model-predicted mean differences inside a $$\pm 10\%$$ margin. This average equivalence is not uniform in flux: evaluated at a single representative flux of $$G = 45$$ kg/m $$^2\cdot$$ s, the fitted curve for PA lies about 13% above that for PC, just outside the same margin. In contrast to the regression-rate similarity, the pressure spectra separate the formulations, though less sharply than the regression data might suggest. Narrow-band modes are resolved in 28 of 30 usable records, and they fall into two tight clusters at $$224 \pm 17$$ Hz and $$414 \pm 16$$ Hz that recur in all three formulations at similar rates. Because the mode frequencies do not depend on what the fuel contains, they are attributed provisionally to the test hardware rather than to the additives. All mode amplitudes are small, between 0.04% and 0.98% of mean chamber pressure, and median total broadband fluctuation over 5–500 Hz is 0.84% (PC), 1.00% (PA) and 0.97% (PAA) — at least a factor of five below the 5% threshold adopted here for identifying combustion instability. No formulation is therefore unstable under the tested conditions, notwithstanding the presence of resolvable modes. The formulation effect on broadband level is modest: PAA exceeds PA in the 5–20 Hz band and PA exceeds PC in the 200–300 Hz band, with no other pair separating and no significant effect on the total level. Because no anti-aliasing filter is documented and only one pressure transducer was recorded, the quoted frequencies may be aliases of higher-frequency components and the mechanisms proposed below are interpretations rather than demonstrated mechanisms.