Propeller (Propulsive) Efficiency
Compute a propeller's propulsive efficiency, η = (T·V/P)·100%, the ratio of useful propulsion power (thrust × speed) to the power delivered to the shaft. It measures how much of the engine power the propeller converts into forward thrust — well-designed propellers reach 80–88% in cruise. It drops sharply at low speed (takeoff) and near the speed of sound at the blade tips. Enter the thrust, the speed and the shaft power.
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Eficiência da hélice (propulsiva)
Uma hélice é uma asa que gira: ela converte a potência do eixo do motor em empuxo. A eficiência propulsiva η = (T·V/P)·100% mede que fração dessa potência vira propulsão útil (empuxo × velocidade de avanço). Hélices bem projetadas atingem 80–88% em cruzeiro — melhor que muitos motores a jato em baixa velocidade. Mas a eficiência despenca em duas situações: parado no solo (velocidade zero → empuxo sem avanço, η→0) e quando as pontas das pás se aproximam da velocidade do som, gerando ondas de choque e ruído. É por isso que hélices têm passo variável e um limite prático de velocidade. Informe o empuxo, a velocidade e a potência no eixo.
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Bearing Power Loss
Calculate the power dissipated by friction in a bearing, P = T × ω, multiplying the friction torque T by the angular velocity ω (rad/s). The result, in watts, is the mechanical energy converted to heat per unit time by friction — a loss that reduces efficiency and heats the lubricant and components. This heat must be dissipated (by convection or oil circulation) to keep a safe operating temperature, since overheating degrades the lubricant and can cause seizure. Estimating the dissipated power is essential to size the cooling and the oil flow. Enter the friction torque and the angular velocity.
Power by Admiralty Coefficient
Estimate a ship's propulsive power by the Admiralty formula, P = (∆^(2/3)·V³)/C, from the displacement (∆, t), the speed (V, knots) and the Admiralty coefficient (C), characteristic of similar hulls. It is a classic, fast method to predict the required power in the preliminary design stage, based on similarity with existing ships. The V³ dependence shows the high cost of speed. Enter the displacement, the speed and the coefficient C.
Aircraft Fuel Efficiency
Compute aircraft fuel efficiency = distance / fuel.
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