Jakub Hnidka

Bio: Jakub Hnidka is an academic researcher from University of Defence. The author has contributed to research in topics: Propeller & Wind tunnel. The author has an hindex of 2, co-authored 17 publications receiving 16 citations.

Measurement automation for small jet engine testing

Abstract: For a small gas turbine engine test cell newly developed and built at the University of Defence in Brno a system for automated measurement and engine test control was designed. The system is based on National Instruments Compact RIO hardware and LabVIEW software and is implementing supervisory control and data acquisition (SCADA) architecture. This paper describes the requirements that drove the decision to develop the software in-house as well as its architecture. It also in detail shows the structure of all three levels of the software that operates separately on the FPGA, cRIO and PC hardware and the communication protocols utilized for information sharing among them.

Testing of the heating element integrated into the honeycomb sandwich structure for active thermography inspection

Abstract: The honeycomb sandwich structures with carbon composite face sheets combined with aluminium or Nomex® honeycomb core are extensively used in the aircraft airframe structure. They provide some key b...

Influence of yaw on propeller aerodynamic characteristics

Abstract: Between the propeller axis and free stream direction, it can still be a non-zero yaw angle. This paper introduces some propeller experiments, in which the propeller aerodynamic characteristics have been determined in various yaw angle and different rotational speeds. The experimental aerodynamic characteristics are acquired dynamic values, from which the influence of yaw conditions on the frequency and the amplitude of propeller thrust and torque can be obtained.

Evaluation of BEM Calculation Method used for Low-Reynolds Propellers

Abstract: This paper presents a simple Joukowsky Blade Element Method (BEM) applied to low-Reynolds propellers, typically used at SUAVs (small unmanned aerial vehicles). This method allows for quick calculation of the propeller performance characteristics in the entire range of expected application, which can be useful for e.g. estimation of the flight performance of an SUAV. Some shortages inherent to the method along with corrections necessary are quickly mentioned. The article then presents a comparison between the calculated propeller performance and measurement performed in the wind tunnel.

Optimization of SUAV’s propeller in a hover

Abstract: Small unmanned aerial vehicles (SUAVs) have found a widespread application in past decades. However, as the criticality of the missions for which they can be used increases, the demand for improvement of their efficiency increases as well. The paper focuses on a propeller driven SUAVs of a multirotor type, equipped with an electric motor, battery and propeller. The paper presents a simplified method of calculation of the SUAV maximal endurance, if the characteristics of all components of the propulsion system are known. To improve the overall efficiency of the propulsion system of an SUAV, the correct combination of all propulsion system components is critical. However, the largest impact on the maximal endurance is, arguably, caused by the propeller. The paper proposes a simple method of optimizing the propeller characteristics for hover and compares the proposed propeller design with conventional and commercially available propellers.

Lock-in thermography using miniature infra-red cameras and integrated actuators for defect identification in composite materials

Abstract: A novel approach for thermographic Non-Destructive Evaluation (NDE) of laminated polymer composite structures is presented. The technique is based on Lock-In Thermography (LIT), which traditionally uses an external heat source. Here a new means of internal heating, via a lightweight embedded actuator capable of providing highly repeatable and uniform heating is presented. The equipment cost, complexity and hence size is reduced by removing the need for high power external thermal excitation. Instead, the necessary temperature modulation of the internal actuator is achieved with a compact and low-cost Arduino controlled circuit. The size and cost of the equipment is further reduced by demonstrating that a miniature printed circuit board mounted thermal core type micro-bolometer can be used effectively for LIT. The performance of the thermal core is quantitatively compared with the more expensive and bulky traditional infra-red cameras. It is shown that the thermal core can detect defects with similar overall performance as a cooled photon detector and an uncooled micro-bolometer. The low-cost, compact nature and small mass of the thermal core offers great potential in thermographic inspection opening the possibility of deploying devices permanently on structures in conjunction with the embedded actuators for in-situ monitoring in the service environment.

Numerical and experimental investigation of flow in an open-type subsonic wind tunnel

Abstract: A numerical and experimental investigation of flow, inside the test section of an open-type subsonic wind tunnel, has been incorporated in the present paper. Experimental data are collected at different selected locations along the wind tunnel length and inside the test section. For detail assessment of the spatial variation of flow variables, numerical analysis is carried out. Boundary conditions have a significant influence on the validation of numerical simulation. A novel approach of system curve generation by experimental analysis of wind tunnel is adopted, instead of using the conventional approach of fan-type boundary condition. Mass flow rate and pressure jump obtained by system curve are utilized for inlet and outlet boundary conditions, respectively. Comparison of numerical and experimental flow fields at the test section suggests maximum error of 9.84% in case of area-weighted average wind velocity along the length of the test section, whereas along the height of the test section a maximum error of 7.75% is observed.

Optimization of SUAV’s propeller in a hover

Abstract: Small unmanned aerial vehicles (SUAVs) have found a widespread application in past decades. However, as the criticality of the missions for which they can be used increases, the demand for improvement of their efficiency increases as well. The paper focuses on a propeller driven SUAVs of a multirotor type, equipped with an electric motor, battery and propeller. The paper presents a simplified method of calculation of the SUAV maximal endurance, if the characteristics of all components of the propulsion system are known. To improve the overall efficiency of the propulsion system of an SUAV, the correct combination of all propulsion system components is critical. However, the largest impact on the maximal endurance is, arguably, caused by the propeller. The paper proposes a simple method of optimizing the propeller characteristics for hover and compares the proposed propeller design with conventional and commercially available propellers.