Aiming at the aircraft composite skin grinding, a new three degree-of-freedom (DOF) parallel mechanism with asymmetrical structure (TAM) is proposed to replace manual grinding. The TAM is achieved by integrating one of active limbs into the passive limb while keeping the required DOF unchanged, which is divided into two closed-loop chains: telescopic rod and parallelogram. The inverse kinematics models of the two chains are established according to closed-loop vector method. Thus, the actuation and the constraint Jacobian matrix are obtained. Based on the perturbation principle, the error modeling of the TAM is built. Adopting the constraint Jacobian matrix, 15 uncompensated errors are distinguished from the error model. In order to improve the working accuracy of the TAM, accuracy analysis and synthesis are necessary for all the uncompensated errors. The mapping function reflects the influence of uncompensated errors on the pose accuracy. The global sensitivity evaluation indexes are established by mapping function. Since Sobol sequences are superior in uniformity and convergence, the Quasi-Monte Carlo method based on Sobol sequences (Sobol-QMC) is introduced for sensitivity analysis. Taking the minimum manufacturing and installation costs as the optimization target, the objective function of accuracy synthesis is constructed. Ultimately, the reasonable tolerance zone of each uncompensated error is calculated by genetic algorithm. Simulation is performed by Sobol-QMC to verify the rationality of the optimization. The results show the probability is above 97% where most pose errors are in [[Formula: see text], [Formula: see text]] within the workspace. Therefore, accuracy synthesis is correct and practical.

Aircraft ground deicing operation is significant to ensure civil flight safety in winter. Helically coiled tube is the important heat exchanger in Chinese deicing fluid heating system. In order to improve the deicing efficiency, the research focuses on heat transfer enhancement of deicing fluid in the tube. Based on the field synergy principle, a new reshaped tube (TCHC) is designed by ring-rib convex on the inner wall. Deicing fluid is high viscosity ethylene-glycol-based mixture. Because of the power function relation between high viscosity and temperature, viscosity has a negative influence on heat transfer. The number of ring-ribs and inlet velocity are two key parameters to the heat transfer performance. For both water and ethylene glycol, the outlet temperature rises when the number of ring-ribs increases to a certain limit. However, the increasing of velocity reduces heating time, which results in lower outlet temperature. The heating experiment of the original tube is conducted. The error between experiment and simulation is less than 5%. The outlet temperature of TCHC increases by 3.76%. As a result, TCHC efficiently promotes the coordination of velocity and temperature fields by changing the velocity field. TCHC has enhanced heat transfer of high viscosity deicing fluid.

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In order to ensure flight safety in cold winter, aircraft ground deicing is crucial and necessary. In Chinese deicing fluid heating system, the helically coiled tube is paramount exchanger to heat deicing fluid. The deicing fluid is ethylene-glycol-based mixture with high viscosity. Aiming at heat transfer enhancement of deicing fluid, ring rib is formed by an embossed tube wall toward the internal of the tube; thus, transversely corrugated helically coiled tube (TCHC) is achieved. Depth and width are two key geometrical parameters of ring rib. Based on field synergy principle, the influence of depth–diameter ratio (H/D) and width-diameter ratio (w/D) is investigated through numerical simulation. The results show that outlet temperature, mean convection heat transfer coefficient, and Nusselt number have similar trends, which first increase and then decrease nonlinearly. The variation of flow resistance coefficient is inversely proportional to Reynolds number. Especially, the effect of H/D is more significant than that of w/D. Field synergy angle and velocity field are also analyzed to reveal the mechanism of heat transfer. TCHC performs better than the original tube. Orthogonal experiment calculates the outlet temperature of TCHC when H/D and w/D change. The combination of H/D=0.075 and w/D=0.5 is best solution. TCHC effectively enhances heat transfer of deicing fluid. Therefore, TCHC is beneficial to improve the deicing efficiency and ensure the flight punctuality.

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