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VTOL Vehicle Design and Development

VTOL Aircraft Takeoff - CFD Consulting and Analysis

Morgan Aircraft is developing a breakthrough technology for Vertical Take-Off and Landing (VTOL) aircraft.  By using an innovative propulsion system, the VTOL aircraft is designed to be a passenger aircraft that can take off and land from virtually any location.  The VTOL aircraft combines the convenience of a helicopter with the long cruise range and comfort of a passenger jet. Upon completion, the VTOL aircraft has the potential to change the course of aviation history and create a new chapter in modern day travel.

The hybrid aircraft must provide efficient hover performance, like a helicopter, for VTOL, as well as deliver a high lift to drag ratio for cruise flight conditions.  Morgan’s VTOL aircraft uses a patented ducted-fan technology to provide vertical lift during take-off and hover (Figures 1 and 2) before gradually transitioning to traditional propulsion systems for cruise flight (Figure 4). The ducted fans add a section of the airframe, or “strake”, which poses its own set of unique technical challenges.
 

Figure 1:  The VTOL Aircraft at Take-Off

The design challenges for implementation of these innovative concepts are significant. Optimizing the aerodynamic characteristics of the airframe (i.e., increasing lift force and reducing drag) is one of the most important phases of aircraft design and development. Proper design maximizes fuel economy and reduces the exhaust’s carbon footprint, something critical for today’s concerns of global warming.

Knowing that precise prediction of aerodynamic performance and stability is critical to the success of the program, Morgan Aircraft requested CAE Associates and ASTA, LLC, one of the nation's recognized  VTOL experts, to lead the Aircraft performance, design configuration and simulation efforts. The choice was based on ASTA’s extensive experience with VTOL vehicle systems performance, and configuration, and CAE Associates’ experience with ducted fan analysis and expertise in the use of CFD technology for aerodynamic applications.

CAE Associates was excited to be a part of this revolutionary project. The size and number of the rotors required to satisfy vertical take-off requirements was the first question to answer. The Morgan team began the design process by studying high lift rotors in a ducted airframe, with CAE Associates conducting hundreds CFD analyses to compute the thrust performance of candidate designs, quantifying rotor thrust and airframe thrust augmentation. The CFD results were evaluated and justified by ASTA’s VTOL design and performance tools. This led to a specific rotor configuration which optimizes the power loading requirement. In addition, under the design optimization approaches ASTA provided, CFD was further utilized to optimize the L/D (Lift to drag ratio) of the integrated conventional wing and ‘strake’ combination in order to achieve the most economic cruise flight condition. 

Once the fundamentals of the rotors, wing-strake geometry/position, and aerodynamic properties were established, optimization was performed for take-off, hover, transition to forward flight, and cruise operations. These are shown in Figures 1-4. Detailed CFD analyses of each component of the aircraft were performed to guide the design work for each phase of the aircraft development. Figure 5 shows the engine exhaust plume, and Figure 6 shows the local flowfield characteristics and boundary layer profile near engine intake.  Based on this information, we are able to define the prototype VTOL aircraft, as shown in Figure 7. The results produced critical vehicle parameters such as maximum payload, range, cruise speed, etc., bringing closure to this unique VTOL passenger aircraft. 
 

Figure 3: Transition from Hover to Forward Flight