Qinyin Zhang

Bio: Qinyin Zhang is an academic researcher. The author has contributed to research in topics: Propulsion & Fuselage. The author has an hindex of 1, co-authored 1 publications receiving 4 citations.

An Adjoint-based Optimization Method for Helicopter Fuselage Backdoor Geometry

Abstract: For utility and transport helicopters with rear loading backdoors, the afterbody area is usually one of the largest drag contributing areas of the fuselage. For this reason, numerical simulations have been performed to assess the possibilities of fuselage drag reduction by the means of local shape modification at the afterbody region. Within this study an automatic optimization chain with gradient-based optimization technique and surface parameterization/deformation tools has been established and applied to the backdoor geometry of a modified GOAHEAD configuration. This paper will present the first numerical results of the ongoing shape optimization studies. As it turns out, local shape modification on the backdoor geometry can lead to a reduction of the separation region there and to a drag reduction of the helicopter fuselage.

Improvement of Take-Off Performance for an Electric Commuter Aircraft Due to Distributed Electric Propulsion

Abstract: The need for environmentally responsible solutions in aircraft technology is now considered the priority for global challenges related to the limited supply of traditional fuel sources and the potential global hazards associated with emissions produced by traditional aircraft propulsion systems. Several projects, including research into highly advanced subsonic aircraft concepts to drastically reduce energy or fuel usage, community noise, and emissions associated with aviation, are currently ongoing. One of the proposed propulsion concepts that address European environmental goals is distributed electric propulsion. This paper deals with the detailed aerodynamic analyses of a full-electric commuter aircraft with fuel cells, which expects two primary electric motors at the wing tip and eight other electric motors distributed along the wingspan as secondary power sources. The main objective was the numerical estimation of propulsive effects in terms of lift capabilities at take-off conditions to quantify the possible reduction of take-off field length. However, the aircraft was designed from scratch, and therefore a great effort was spent to design both propellers (for the tip and distributed electric motors) and the wing flap. In this respect, several numerical tests were performed to obtain one of the best possible flap positions. This research work estimated a reduction of about 14% of the take-off field length due to only the propulsive effects. A greater reduction of up to 27%, if compared to a reference conventional commuter aircraft, could be achieved thanks to a combined effect of distributed propulsion and a refined design of the Fowler flap. On the contrary, a significant increment of pitching moment was found due to distributed propulsion that may have a non-negligible impact on the aircraft stability, control, and trim drag.

CAD‐based shape optimisation with CFD using a discrete adjoint

Abstract: SUMMARY One of the major challenges of shape optimisation in practical industrial cases is to generically parametrise the wide range of complex shapes. A novel approach is presented, which takes CAD descriptions as input and produces the optimal shape in CAD form using the control points of the Non-Uniform Rational B-Splines (NURBS) boundary representation as design variables. An implementation of the NURBS equations in source allows to include the CAD-based shape deformation inside the design loop and evaluate its sensitivities efficiently and robustly. In order to maintain or establish the required level of geometric continuity across patch interfaces, geometric constraints are imposed on the control point displacements. The paper discusses the discrete adjoint flow solver used and the computation of the complete sensitivities of the design loop by differentiating all components using automatic differentiation tools. The resulting rich but smooth deformation space is demonstrated on the optimisation of a vehicle climate duct. Copyright © 2013 John Wiley & Sons, Ltd.

Aerodynamic optimization of helicopter rear fuselage

Abstract: An optimization process for the rear helicopter fuselage is presented using Genetic Algorithms and Kriging surrogate models. Shape parameterization is carried out with the super ellipse technique employed for the well-known ROBIN fuselage. The simulations were based on the RANS equations solved using the HMB CFD code. It is shown that a decrease of fuselage drag around 2.5% is possible without compromising the structure and the functionality of the design. Combined with an optimization of the helicopter skids, benefits of up to 4.6% were possible. The demonstrated method can be applied to fuselages of any shape during the initial design phase.

Computational Fluid Dynamics Modeling of Helicopter Fuselage Drag

Abstract: The aim of this paper is to present aerodynamic analyses of realistic fuselage configurations using computational fluid dynamics. A development model of the Ansat helicopter is employed. The model is tested at the subsonic wind tunnel of the Kazan National Research Technical University/Kazan Aviation Institute for a range of Reynolds numbers, pitch, and yaw angles. The computational fluid dynamics results were found to be in fair agreement with the test data and revealed flow separation at the rear of the fuselage. Once confidence in the computational fluid dynamics method was established, further modifications were introduced to the fuselage model to demonstrate drag reduction via small shape changes. The contribution to the overall drag from each fuselage part and the interference drag between the main fuselage components were also investigated.

CAD-based CFD shape optimisation using discrete adjoint solvers

Abstract: Computational fluid dynamics is reaching a level of maturity that it can be used as a predictive tool. Consequently, simulation-driven product design and optimisation is starting to be deployed for industrial applications. When performing gradient-based aerodynamic shape optimisation for industrial applications, adjoint method is preferable as it can compute the design gradient of a small number of objective functions with respect to a large number of design variables efficiently. However, for certain industrial cases, the iterative calculation of steady state nonlinear flow solver based on the Reynolds-averaged Navier–Stokes equations tends to fail to converge asymptotically. For such cases, the adjoint solver usually diverges exponentially, due to the inherited linear instability from the non-converged nonlinear flow. A method for stabilising both the nonlinear flow and the adjoint solutions via an improved timestepping method is developed and applied successfully to industrial relevant test cases. Another challenge in shape optimisation is the shape parametrisation method. A good parametrisation should represent a rich design space to be explored and at the same time be flexible to take into account the various geometric constraints. In addition, it is preferable to be able to transform from the parametrisation to a format readable by most CAD software, such as the STEP file. A novel NURBS-based parametrisation method is developed that uses the control points of the NURBS patches as design variables. In addition, a test-point approach is used to impose various geometric constraints. The parametrisation is fully compatible with most CAD software. The NURBS-based parametrisation is applied to several industrial cases.