Concept

 

A standard Brayton cycle consists of a thermal resevoir with temperature Thot, a thermal resevoir with temperature Tcold, a compressor,and a turbine.

For a standard open Brayton cycle (see left figure below), the air enters into the compressor and is compressed to a higher pressure and is sent to the Combustion Chamber. In the case of our project, the combustion chamber is to be replaced with a thermal resevoir where the thermal heat from the radioisotope fuel source will be introduced to the system. After the fluid passes through the thermal resevoir with temperature Thot, the fluid will be at high pressure and high temperature. The fluid will then enter the turbine which will extract mechanical work and spin the shaft. After the turbine, the fluid is exhausted into the atmosphere.

The closed standard Brayton cycle (see right figure below) consists of the same cycle except instead of exhasuting the fluid into the atmosphere, it is sent to a thermal resevoir with Tcold to reject the heat into the atmosphere. The fluid then returns back to the compressor and starts the cycle over.

The left figure is an open cycle and the right figure is a closed cycle.

Conceptual Design

The conceptual design stage of the project focused around development of five main components excluding the generator. The current system design is connected through brass pipes and is designed to incorporate four different Brayton cycles using ball valves. The cycles our system will be able to operate as are as follows: Open, Open with Regeneration, Closed, and Closed with Regeneration. Our system configuration is shown below:

Below is a rendering of our final manufactured design:

Components

These components of the design above have been manufactured and integrated into the final design. To see more on the manufacturing process, visit the Manufacturing page.

Turbine and Compressor

The turbine and compressor share a common shaft. One area that could cause problems is the inlet to the compressor and turbine. The inlet will need to be designed to allow maximum fluid velocity when entering the housings. The inlet will bed designed to act like a converging nozzle.

ImpulseBlade

For our designed turbine and compressor, we have decided to use impulse blades. These blades have been sized to have a volumetric flow of approximately 30 CFM. We are currently looking into having the impulse blades milled by a company with experience in these types of applications due to the complexity of the part.

 

 

 

Heater & Heating Element

A simple electric heating element will be used as an analog to the radioisotope fuel source that the actual Mar's Hopper will have. The element in question has a thermal output of 1000 Watts which is equivalent to the thermal energy of the radioisotope. It will be housed in a square aluminum housing.

HX

 

Heat Exchanger

The heat exchanger design is still under development. One possible idea is shown below:

HX

Regenerator

The regenerator concept is shown below:

Regen

Electric Generation

For the generation of elecitricity, our design will incorporate a simple hobbyists electrical motor. The motor will be run in reverse to generate approximately 250 Watts.