6-DOF All-Terrain Cyclocopter

This paper presents the design of a 6-DOF all-terrain micro aerial vehicle and two control strategies for multimodal flight, which are experimentally validated. The micro aerial vehicle is propelled by four motors and controlled by a single servo for the control of the cycloidal rotors(cyclorotors) speed and lift direction. Despite the addition of the servo, the system remains underactuated. To address the traditional underactuation problem of cycloidal rotor aircraft, we increase the number of control variables. We propose a PID and a nonlinear model predictive control (NMPC) framework to tackle the model's nonlinearities and achieve control of attitude, position, and their derivatives.Experimental results demonstrate the effectiveness of the proposed multimodal control strategy for 6-DOF all-terrain micro aerial vehicles. The vehicle can operate in aerial, terrestrial, and aquatic modes and can adapt to different terrains and environmental conditions. Our approach enhances the vehicle's performance in each mode of operation, and the results show the advantages of the proposed strategy compared to other control strategies

Research on the Power Recovery of Diesel Engines with Regulated Two-Stage Turbocharging System at Different Altitudes

Recovering the boost pressure is very important in improving the dynamic performance of diesel engines at high altitudes. A regulated two-stage turbocharging system is an adequate solution for power recovery of diesel engines. In the present study, the change of boost pressure and engine power at different altitudes was investigated, and a regulated two-stage turbocharging system was constructed with an original turbocharger and a matched low pressure turbocharger. The valve control strategies for boost pressure recovery, which formed the basis of the power recovery method, are presented here. The simulation results showed that this system was effective in recovering the boost pressure at different speeds and various altitudes. The turbine bypass valve and compressor bypass valve had different modes to adapt to changes in operating conditions. The boost pressure recovery could not ensure power recovery over the entire operating range of the diesel engine, because of variation in overall turbocharger efficiency. The fuel-injection compensation method along with the valve control strategies for boost pressure recovery was able to reach the power recovery target

Development of a Three-Phase Sequential Turbocharging System with Two Unequal-Size Turbochargers

A three-phase sequential turbocharging system with two unequal-size turbochargers is developed to improve the fuel economy performance and reduce the smoke emission of the automotive diesel engine, and it has wider range of application than the current two-phase sequential turbocharging system. The steady matching method of the turbochargers and engine and the steady switching boundary are presented. The experimental results show that this system is effective to improve the engine performance especially at the low speed and high load. The maximum reductions of BSFC and smoke opacity are 7.1% and 70.9%. The optimized switching strategies of the valves are investigated, and the surge of the compressor in the switching process is avoided. The switching strategies in the accelerating process are optimized, and the acceleration time from 900 r/min and 2100 r/min at constant torque is reduced by approximately 20%

Study of Top Dead Center Measurement and Correction Method in a Diesel Engine

Abstract: The thermal loss angle error analysis and maximum pressure determination method analysis were conducted first. Then the polytropic exponent method, the inflection point analysis, the loss function method and the symmetry method were utilized under different rotating speed, load and cooling water temperature, to calculate TDC in D6114 diesel engine and the results were compared with TDC position measured under the same condition with direct method of measurement. The study proved that (1) thermal loss angle of the diesel engine ranges from -1.0 ~ -0.6°CA; (2) Thermal loss angle is mainly affected by rotating speed and is reducing when rotate speed increases;(3) the symmetry method is generally the optimum for calculating the thermal loss angle of automotive diesel engines, with an error within 0.2°CA

Loss analysis of a mix-flow turbine with nozzled twin-entry volute at different admissions

This paper investigates performance and loss mechanism of a nozzled twin-entry mix-flow turbine at different admissions. Two sets of partial admissions and unequal admissions are analysed via experimentally validated numerical method. Results show that discrepancies of turbine efficiency between symmetrical unequal admissions (swopping inlet pressure on two entries) increase when unequal admissions approach to partial admissions, although their swallowing capacity is similar. Loss breakdown of turbine shows that loss is higher in nozzle but lower in rotor when the majority of flow is fed from upper part of the component (near shroud). Opposite phenomenon happens when the majority is fed from lower part (near hub). The reason for loss characteristic of nozzle is front-sweep configuration of the nozzle vane which results in evident flow separation when the flow is fed near the shroud. The reason for loss characteristic of rotor is the tornado-shaped vortex when the flow is fed from the hub. The tornado vortex is initiated by large incidence angle near hub and developed by the combination of Coriolis force, pressure gradient and centrifugal force. The study unveils loss mechanism among different admissions for a twin-entry turbine, which may enlighten the design methodology of the turbine with twin-entry volute

Unsteady behaviours of a volute in turbocharger turbine under pulsating conditions

Turbochargers are currently in their prime utilization period, which pushes for performance enhancement from conventional turbochargers and more often than not revisiting its design methodology. A turbocharger turbine is subjected to pulsating flow, and how this feeds a steady flow design volute is a topic of interest for performance enhancement. This article investigates unsteady effects on flow characteristics in the volute of a turbine under pulsating flow conditions by numerical method validated by experimental measurement. A single pulse with sinusoidal shape is imposed at the turbine inlet for the investigation on unsteady behaviours. First, pulse propagation of different flow parameters along the volute passage, including pressure, temperature and mass flow rate, is studied by the validated numerical method. Next, the unsteady effect of the pulsating flow on the flow angle upstream the rotor inlet is confirmed by simulation results. The mechanism of this unsteady effect is then studied by an analytical model, and two factors for flow angle distributions are clearly demonstrated: the configuration of the volute A/Rc and the unsteady effect that resulted from mass imbalance. This article demonstrates unsteady behaviours of the turbine volute under pulsating conditions, and the mechanism is discussed in details, which can lead to the improvement of volute design methodology tailoring for pulsating flow conditions