DESIGN AND MANUFACTURING OF HOVERCRAFT

Transcription

1 DESIGN AND MANUFACTURING OF HOVERCRAFT Tejas Velapure* Deepak Sonawane* Rahul Waghchaure* Pratik Choudhari* Prof. Kiran Wangikar** *UG students, Department of Mechanical Engineering, Vishwakarma Institute of Information Technology, Pune **Assistant professor, Department of Mechanical Engineering, Vishwakarma Institute of Information Technology, Pune Abstract Hovercrafts which are also called as Air Cushioned Vehicle or ACV are designed to travel over land, water, snow as well as other surfaces like mud, grass, quicksand, sand etc. Hovercrafts hover on smooth cushion of air delivered through skirt, which can be of different materials according to use. For design as well as development of Hovercrafts, following factors are taken into account such as size of the ACV, materials used for skirt, weight carried by hovercraft, speed, strength required by the hull, component availability as well as intermediate fabrication skills. As it can travel over land, water and ice, it can be used for various applications such as flood rescue operations, military surveillance near coastal areas, transportation purpose and for research in snowy regions. Now a days, it is being very popular vehicle in today s transportation system. People are considering it as a new generation vehicle. It is kind of different from other conventional vehicles as there is no actual contact between base of the hovercraft and surface on which it is hovering. In this paper, we are focusing on the theoretical study of hovercraft as well as various design parameters and their performance characteristics of hovercraft 1. INTRODUCTION A hovercraft, also known as an air-cushion vehicle or ACV, is a craft capable of travelling over land, water, mud or ice and other surfaces both at speed and when stationary, the air is continuously forced under the vehicle by a fan, generating the cushion that greatly reduces friction between the moving vehicle and surface. It all started with one man in His name was Emanuel Swedenborg, and he was a Swedish designer and philosopher. Because Emanuel introduced the idea of hovercraft way before it's time of possible implementation, he knew that it would be impossible to make it work, due to the fact that if he were to make a hovercraft, it would require a great deal of energy to make it hover. A little while later, a 52

2 man by the name of Sir John Thorneycroft experimented further with the idea of air lubrication. His idea was that one could use an air cushion on boats so as to reduce drag that the boat experienced.. In 1876 the true design of a modern day hovercraft was starting to come together. A man by the name of John B. Ward came up with the idea of a platform made out of aluminium that had blades that pushed air down for the creation of the air-cushion and another set of blades that would push air backwards, so as to provide for propulsion. In 1888 James Walker developed a system of containing the air under the platform and in 1897 Culbertson made the first suggestion for sidewall air-cushion vehicles. SR.N1 was considered the first real hovercraft due to the fact that most of the other ground effect vehicles were very similar to planes. Specifically hovercraft has three main design groups: the lift, thrust, and steering systems. 2. LITERATURE REVIEW Research in the field of development of hovercraft prototype was done. We designed hovercraft that was lifted and was propelled by the thrust system. It was able to carry one person of weight 75 kg and hovered with an air cushion of 0.5 inch. Manoeuvrability was achieved with the steering system. The design process is quite similar to that of boat and aircraft. The craft principle has been demonstrated using low cost material and has proved capable as a viable means of transport both on land and water after series of tests. The propulsion and lifting systems gave excellent performance and with good manoeuvrability. We developed the hovercraft design that lift the weight using air cushion technique. The blow of air from the narrow hole with high pressure and high RPM inside the skirt create the lift. When the air is blow inside the skirt with pressure, then the air is circulated in the skirt when the air is circulated the air is get the small hole outlet which create the pressurize the earth surface the which impact the earth surface and create the lift and also reduce the friction between the earth surface and the unit. The unit is run on the surface due less friction. We developed the hovercraft prototype with an aluminium hull base. A study to construct an economical and robust hovercraft by using the Aluminium composite sheet. Structural analysis by using ANSYS software was carried out to see the suitability and the reliability of the alloy. The construction of the hull base prototype was supported by the results from this analysis and simulations of establishing Aluminium composite sheet as the material use in building up the hull base. After series of experimental testing, the propulsion and lifting systems were successfully demonstrated and the prototype capable of manoeuvring nicely. Modelling and controllability studies of a hovercraft system were introduced. The system studied is a little more complicated than some in the literature in that the inertial dynamics of the thrust fan are taken into account. They model dynamics, and illustrate how they affect the controllability analysis for the system. The adding of the seemingly innocuous dynamic effect of fan inertia destroys the nice controllability properties of the system. 2.1 Broad Conclusion of Literature Review 53

3 2.1.1 A study on construction and working principle of hovercraft. In this paper, author V Abhiram has given the information about the construction and working of the hovercraft. There is information about the principle. In the construction there is given brief about the lifting fan, thrust propeller, hovercraft skirt, air box, lift system, thrust system, steering system. In this paper, there is also given the some calculations about the lift power, pressure Development of hovercraft prototype in this paper, author Okafor has given the actual design calculations of the hovercraft. Some legal issues about the hovercraft is given in this paper. There is given design concept for the hovercraft. Calculations for the major components like hull, lift system, skirt, thrust system is given in this paper Development of integrated air cushioned vehicle. In this paper authors S.V. Uma, Maheshwara Rao, V. S. Surya Prakash has mentioned principle, working, design of major components. Additionally there is given brief information about the fabrication of the hull, air box, skirt and engine. There is mentioned future scope of the hovercraft. 3.Methodology First of all, to design the hovercraft, all needed research in the field of development of hovercraft was done. Such hovercraft was designed which was lifted and was propelled by the thrust system. It was able to carry weight of 20 kg and hovered with an air cushion of 0.5 inch. Air cushions of hovercraft are supplied with blowers and so that it floats above the surface. The air cushion makes the hovercraft essentially frictionless. Air is blown into the skirt through a hole by the blower. Small holes present on the skirt of hovercraft prevent it from bursting and provide the cushion of air. Little efforts are made on the hovercraft which propels it in the direction of the push. As soon as the hovercraft floats, a blower situated in the base causes the vehicle to move forward by blowing air backwards which provides an equal reaction. Little power is needed as the air cushion has drastically reduced. By mounting rudders in the airflow from the blower or propeller, Steering effect is achieved. More case study and work is going on the direction control. We are planning to use DC motors for direction control. A change in direction of the rudders changes the direction of air flow which causes change in direction of the vehicle. This all control will be achieved by remote control. We developed the hovercraft design such that it will lift the weight using air cushion technique. The blow of air from the narrow hole with high pressure about 600 N/m 2 and high RPM inside the skirt creates the lift. When the air is blown inside the skirt with pressure, then the air is circulated in the skirt. When the air is circulated through a small hole outlet which pressurize the earth surface 54

4 which impact the earth surface and create the lift and also reduce the friction between the earth surface and the unit. Hovercraft is one of the most unusual vehicles that is becoming popular now a day, moves on an air cushion of slightly pressurized air that makes it easily overcomes any slight unevenness and obstacles. Because the hovercraft moves only after air and earth will affect virtually, no matter what the surface flies. It can run on sand, asphalt and the water. It also consists of swamps and snow too. They belong to a group of Amphibians. Hovercraft dynamics is more aircraft than ships and automobiles. It is based on different law s act in air cushion vehicle such as law of buoyancy, newton s third law, etc for development of hovercraft prototype. The law buoyancy states that When a body is immersed in fluid at rest it experiences an upward force or buoyant force equal to the weight of the fluid displaced by the body. Newton s third law states that all forces exist in pairs: if one object A exerts a force FA on a second object B, then B simultaneously exerts a force FB on A, and the two forces are equal and opposite: FA = FB. The hovercraft prototype is developed with an aluminium composite panel. Aluminium composite panels are used because they have high structural rigidity and low weight. They also have good energy efficiency and sustainability. Most important thing is it is economical too. In this study, the stability and ultimate strength of the ACP was tested to find its stands as the material for the hovercraft hull base development and hull base was chosen as it gives lighter weight. It is a cost-effective material for this hovercraft prototype project and can be easily found in the hardware stores. Structure analysis was carried out to confirm the reliability of this sheet usage on the construction of the hovercraft prototype hull base. All the data gathered from the hull base design produced by CAD-CATIA modelling were processed with finite element analysis software. This software can be applied for 3 dimensional analyses of the modelling and provide detail information on the three: the reaction force, displacement and stress tensor. The computed data was used for comparison with the maximum permissible stress derived from the minimum guaranteed mechanical properties of the material used in the component. Here, we briefly outline the pre-processing of the hovercraft hull. Firstly, the CAD 55

5 modelling of the hull was drawn using computer added design software Solid works and did flow analysis in flow simulation. The CAD model provided the facets of the hull which was then transformed into solid form before computational meshed can be generated. Modelling and controllability studies of a hovercraft system. The system studied is a little more complicated than some in the literature in that the inertial dynamics of the thrust fan are taken into account. The design and development of a hovercraft prototype with full hovercraft basic functions is reported by taking into consideration, size, material and component availability and intermediate fabrication skill. In-depth research was carried out to determine the components of a hovercraft system and their basic functions and in particular its principle of operation. The fabrication of the designed hovercraft by using materials that are readily available by taking into consideration the economic constraints and time constraints. It also includes the testing process which includes the tweaking of various parameters that govern lift and thrust of the hovercraft. Further research is recommended to improve on the efficiency of the craft. This design proposes an integrated system i.e. a single Blower is used for both the lift and thrust requirements. First we did a small scale prototype using a single blower of 2.2 m3 /min. It lifted a weight about 5 to 6 kg with consideration of weight of blower and hull. Then according to that ratio we did calculations for big scale. 4. DESIGN 4.1 Design and Calculations for Prototype: Firstly we did the research in the field of development of hovercraft prototype and designed hovercraft that was lifted and was propelled by the thrust system. It was able to carry one person of weight 4 kg and hovered with an air cushion of 3 mm. Length = 20mm Breadth = 30mm Mass to be lifted = 4 kg Area of hoverboard = m2 Escape area (Ae) = m2 Force = 9.81*4 = ~ 40N 56

6 Pressure = F/A = 40/0.063 = N/mm2 Escape velocity Ve = (2*p/ρ) ^ (1/2) = (2*634.92/1.2) ^ (1/) = m/s Flow rate = Ve*Ae = *33.67 =0.03m3/s Available blower size in the market =2.3m3/min= 0.038m3/s so, we choose the blower suitable for our application and build the prototype according to that. 4.2 First Prototype Testing: We build the prototype considering above calculations and verified our calculations. 4.3 Design and Calculation for Final Model: Fig.1 2D model for base We design the model such that it will be able to carry weight of 20 kg and hovered with an air cushion of 5mm. M = 20 kg Inlet diameter Di = 40 mm Inlet area = = 90*10-4 = *10-3 m2 Escape area Ae = 90*10-4 m2 Area of hoverboard A h = (0.6*0.5) + 2*(0.5*0.1*0.3) + (0.4*0.3) = 0.45 m2 Pressure P = F/A h = 20*10/0.45 = 436 Pa Escape velocity Ve = (2*P/ρ) ^ (1/2) = 8.75 m/s Theoretical required flow rate Qe = Ae*Ve = 90*10-4 *8.75 = 4.78 m3 /min Considering losses and factor of safety we took flow rate as 6 m3/min 57

7 Fig.1 2D model for base Force Calculations to Attain Speed M = 20 kg Q = 2.3 m3/min Input power P = 500 W Efficiency of blower ἠ = 0.7 Power of blower P b = 0.7 * 500 = 350 W Pressure P = P b /Q = 350/ = N/m2 Outlet area of blower = * 10-3 m2 F = P*A = N Acceleration = F/M = m/s2 Speed attained in 10 sec Velocity = acceleration * time = * 10 = m/s = 20 km/hr 4.4. Analysis of Base Material: The hovercraft prototype is developed with an aluminium composite panel. ACP are used because they have high structural rigidity and low weight. They also have good energy efficiency and sustainability. Most important thing is it is economical too. In this study, the stability and ultimate strength of the ACP was tested to find its stands as the material for the hovercraft hull base development and hull base was chosen as it gives lighter weight. It is a cost effective material for this hovercraft prototype project and can be easily found in the hardware stores. Structure analysis was carried out to confirm the reliability of this sheet usage on the construction of the hovercraft prototype hull base. All the data gathered from the hull base design produced by CADCATIA modelling were processed with finite element analysis software. This software can be applied for 3 dimensional analyses of the modelling and provide detail information on the three: the 58

8 reaction force, displacement and stress tensor. The computed data was used for comparison with the maximum permissible stress derived from the minimum guaranteed mechanical properties of the material used in the component. Here, we briefly outline the pre-processing of the hovercraft hull. Firstly, the CAD modelling of the hull was drawn using computer added design software Solidworks and did flow analysis in flow simulation. The CAD model provided the facets of the hull which was then transformed into solid form before computational meshed can be generated. After CAD modelling analysis of base plate was done considering different position of blowers such as load at centre and blowers at front and load at front and blowers at front. Its results are illustrated below. The structural properties are as follows: Density = 1520 kg/m3 Ultimate Tensile strength = 45.8 MPa Yield strength = 43.4 MPa Taking the blower at centre and load at front: Load at mid = 80N Load at front = 100 N Load at backside = 20N After doing the analysis, report has been generated. Link for Fig 3 Stress Distribution when load is at front From above analysis we interpreted that maximum stress developed at holes is MPa which is very close to ultimate tensile strength i.e MPa. Practically many factors like temperature, humidity may increase its stress concentration so to have safe design we discard these design. 59

9 Fig.4 Deformation analysis when load is at front Deformation analysis shows that the deformation obtain is large i.e mm for entire middle portion so it gets bend very easily. Considering this factor we had to change blower position. Taking blower at front Load at front = 100N Load at mid = 80N Load at backside = 20N after doing the analysis, report has been generated. Link for Fig.5. Stress distribution when load at centre When load is applied at centre and blowers are place at front we got maximum stress concentration as MPa which much lower than the ultimate tensile stress i.e.48.3 MPa so, we got factor of safety as 2.81 which makes our design as safer. Hence these design is finalized. 60

10 Fig.6. Total deformation when load at centre 7. CONCLUSION Study was conducted to verify the theoretical calculations and performance parameters. Thus we conclude that actual model satisfies our design requirement. The working principle of hovercraft is verified. 8. REFERENCES 1. Stokes equation in a toy CD hovercraft. Charles de Izarra, Gregoire de Izarra, July To study and fabrication of air cushion vehicle, Amit Tiwari march Position tracking for a Nonlinear Underactuated Hovercraft: Controller Design and experimental results. Antonio Pedro, Lars Cremeanz, Joao Pedro Hespanhay Hovercraft - A Project Based Approach To Introduction to Engineering.S. B. Pillapakkam, J. J. Helferty and S. J. Chen, august A review on design and analysis of amphibious vehicle. Prof. P. S. Shirsath1, Prof. M. S. Hajare2, Prof. G. D. Sonawane3, Mr. Atul Kuwar4, Mr. S. U. Gunjal, 1 Jan Design and Fabrication of Minihovercraft Vasanthkumar.P 1, Vignesh. K 2, Rajkumar. G 3, 2 February Controllability of a hovercraft model (and two general results).andrew D. Lewis_ David R. Tynery, September Development of a Hovercraft Prototype Okafor, March

11 9. A fully-autonomous hovercraft inspired by bees: wall following and speed control in straight and tapered corridors. Frederic L. Roubieu, Julien Serres, Nicolas Franceschini, Franck Ruer, 10. Study on construction and working principle of a hovercraft V Abhiram, N Suman Krishna, T Murli Mohan Raju, 4 October Development of integrated air cushioned vehicle. S.V. Uma Maheshwara Rao, V.S. Surya Prakash, May