部份畢業專題項目

Ventilation and Air Conditioning System Design in MTR Train
Final Year Project 2011/2012
Student: CHEUNG Chun Ho
  KWONG Ming Chun Mario
  SIU Ho Yin

 

Today, Mass Transit Railway (MTR) become one of the mass transport systems in Hong Kong. In order to provide comfortable journeys to a vast number of passengers, the air-conditioning units must be carefully designed and precisely controlled such that every individual inside the compartment is satisfied regardless of the outside air conditions.

According to the real situation, due to the locations of air-conditioning inlets, the temperature variations inside the compartments could be varied dramatically: some passengers near the inlets can feel very comfortable and cool, but for those who are far from that, especially during summer and the train is at its full load, they may feel very hot and stuffy. Even for the former ones, if their train journeys are sufficiently long, they may feel very cold too.

In response to the above problems, our group is going to investigate the relevant factors like how the outside air conditions, air inlet temperature and velocity as well as the number of passengers inside the compartment affect the air temperature inside. Firstly, relevant data like dimensions of compartments, inlets, windows, doors, seats and columns as well as the air inlet temperature and velocity were measured and recorded. Then, a model of the compartment was drawn using the software Solidworks. Next, the model was meshed and blocked in ICEM and later it was input into Fluent for air flow pattern, pressure and thermal analysis. Finally, the results were investigated and discussed and corresponding suggestions for improvement were made.

Investigation of Critical Velocity of Longitudinal Tunnel Ventilation Under Different Conditions
Final Year Project 2011/2012
Student: CHEUNG Tsan Ming
  TANG Chui Wan
  TONG Wang Fai

 

This project presents an analysis of the variation of critical velocity, which in an important parameter for longitudinal ventilation design of vehicle tunnel, with heat release rate using computational fluid dynamics (CFD) technique. The objectives of this project are to conduct accurate prediction of the critical velocity driven by a fire in tunnel and further analyze the effects of such parameters as heat release rates and locations of fire sources. Reference tunnel models, such as the Memorial Tunnel in US and the Shing Mun Tunnel in Hong Kong, were chosen as the targets for analysis. The fire simulations were carried using the CFD software called Fire Dynamics Simulator (FDS).

The projects started with a validation study of numerical model built in FDS with existing data available from the Memorial Tunnel Fire Ventilation Test Program (MTFVTP). The validation was undertaken by comparing the FDS numerical results, simulated using exactly the same conditions as MTFVTP, with both measurement data available from MTFVTP and existing theories of longitudinal tunnel ventilation. It was found that the FDS prediction was very close to the MTFVTP measurement results and had a better agreement than the theories. Having gained the numerical settings for accurate fire dynamic simulations, the analysis continued to study the effects of different tunnel design parameters on the tunnel critical velocity.

Flow Through Silencer
Final Year Project 2011/2012
Student: CHI Hon Man
  CHI Kin Ng
  LUN Hoi Ng

 

Low frequency noise is difficult to tackle by traditional passive methods and there is still a technical challenge. Active control method performs very well for controlling low frequency noise. However, it requires additional sensors and actuators and the system is sophisticated so there is a problem on the huge amount of the cost and reliability. Passive noise control remains more reliable and attractive for the users especially for the ventilation system. For example, a layer of porous material is lined on the duct wall which is so called duct-lining is widely used in the air conditioning and ventilation system. However, it cannot perform well at low frequencies. On the other hand, the use of the multiple expansion chamber integrated with the perforated technology can achieve high noise reduction in very wide frequency range. However, there is great pressure drop due to the change of cross sectional area. In order to eliminate the pressure drop and keep the noise control device that works effectively in the low to medium frequency range, the concept of using panels to reflect low-frequency noise was introduced by a team of researchers. Through the theoretical investigation of the coupled structure and acoustic system and the modal analysis, desirable transmission loss with wide stopband can be achieved on condition that the plate should be very light and high bending stiffness. However, it is difficult to find the plate with this physical property from the existing materials. The only one solution is the composite material. Therefore this project aims (1) to investigate the method of manufacturing the plate with high strength to mass ratio by attaching carbon fibre tows on the PMI foam plate, (2) to study the performance of the plate silencer experimentally by using our manufactured plate and (3) to investigate the effect of adding the microperforations on the plate.

Development and Research on two-joint
Mechanical Fish
Final Year Project 2011/2012
Student: LI Tak Yu
  SUNG Yan Lok
  WONG Wai Ka

 

Fish has a powerful swimming capability after thousands of years’ evolution. For example, it is well known that the tuna can swim with high speed and high efficiency, the pike can accelerate in a flash and the eel could swim skilfully into narrow holes. Such swimming capabilities provide an inspiring source for researchers to develop and study more efficient, powerful and energy-saving aquatic vehicles. This project aims at development of a two-joint mechanical fish by mimicking a real salmon fish to reveal its potential advantages in body control and propulsion efficiency and to explore novel, efficient, and environment-friendly propulsion methods for aquatic vehicles. Comparing with existing propulsion techniques in aquatic vehicles (e.g., ships) and other one-joint mechanical fishes, it is shown that the two-joint mechanical fish can move more freely at a higher propulsive efficiency, higher manoeuvrability and less noise.

Design and Development of a Low Cost Rapid Prototyping Machine
Final Year Project 2011/2012
Student: CHEUNG Woon Yiu
  LAI Kai To

 

A special purpose low cost rapid prototyping (RP) machine is designed and made. The hardware is a self-developed CNC 2-1/2 axes extruder. An open source software is used for the interface between the CAD and the RP machine in order to save the software development time. The prototype can be modeled from a standard CAD and then be made by the RP machine. Cost of this RP machine is just a few percentage of the commercial RP machine in the market. This RP machine is suitable for producing simple prototypes not requiring high dimensional accuracy such as building blocks for children. Children can design their own building blocks and then make them by using this RP machine. Other possible applications are model making for interior or floor plan designs.

Design and Construction of a Small Wrapping Machine for Holiday
Final Year Project 2011/2012
Student: TAM Kam Piu
  WONG Ka Kit
  WONG Wang Chin

 

During Christmas, Lunar New Year and other festivals, many large department stores and super markets provide present wrapping service for customers and many temporary workers are employed to wrap hundreds of presents every day. This project aims at designing and constructing a small wrapping machine that can save manpower and increase work efficiency. To start with, only box-shape presents are handled by our first-generation wrapping machine. The machine employs a PLC to control the motion of several electro-pneumatic cylinders that either move the present around the work space or push the flappers to fold the wrapping paper. The prototype machine costs less than HKD4000 and can wrap presents at a rate comparable to human workers.

The prototype machine requires further work and several enhancements to enable it to handle presents of different dimensions automatically. Nevertheless, we have proved that the idea of a small scale and inexpensive wrapping machine is economically and technically feasible. The video below shows the successful operation of the prototype machine.