Kinetic energy recovery in motor vehicles using compressed gas

Kruger, Rick William (2014) Kinetic energy recovery in motor vehicles using compressed gas. [USQ Project]

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Abstract

It's no secret that we are depleting our natural resources at an unsustainable rate while polluting our natural environment. This is especially true when it comes to motor vehicles. As a result, manufacturers are investing billions of dollars every year to produce energy efficient vehicles that reduce fuel consumption and vehicle emissions. One method is to introduce regenerative braking. This is the process of recovering kinetic energy from a moving vehicle under braking conditions. The energy is used to increase performance and efficiency, hence addressing the issues of sustainability and the environment.

The research of this project was focused on the concept of using an internal combustion (IC) engine as a compressor to recover kinetic energy as compressed gas. This is a concept that has been considered over the last decade and a half, with the one of the first being Schechter (1999). This research project investigates the ability to use the engine as a compressor and assess its performance and viability when compared with two other main regenerative braking technologis: hybrid electric vehicles (HEV) and flywheels.

A literature review was undertaken, and revealed the major aspects that affect the ability of an IC engine to compress gas. The major component needed for this concept was a variable valve timing (VVT) system that allows the engine to operate as a compressor, and even a pneumatic motor if needed. The system would also require modifications to the cylinder head to add a charge/discharge valve, and of course, a pressure tank for storing the compressed gas.

The research methodology considered a quasi-dimensional numerical simulation of an IC engine operating as a reciprocating two-stroke compressor. The simulation was based on a model previously prepared by Buttsworth (2002) to determine the performance of a fuel inducted engine with a heat release profile as a function of the crank angle - the method that closely followed that described by Ferguson (1986).

After testing, the model was simulated during the deceleration phases of the NEDC test cycle. The valve timing was optimised to produce the least amount of work during the simulation, while the engine speed was optimised to reduce the reliance on the friction brakes. The results showed that the energy recoverable was 574 kJ over the entire cycle with the assumption that the energy recovered was used after each deceleration event. Based on an engine efficiency of 30% and usable energy of 80%, this translates to energy savings of 1.5MJ and fuel savings of 43 ml over the full cycle.

Overall, the concept of using compressed gas to recover kinetic energy appeared to be viable. With additional components and modifications, an engine can be used as a compressor. The advantages seem to be the mass of the system and its simplicity when compared to HEVs and flywheels. The fuel savings also appeared to be competitive. However, it seems to be less suited for storing energy over longer periods of time, and has a lower regenerative efficiency as shown in the results of this research and the research of others. It is unclear whether or not it could compete with HEVs in the market. The research suggests that more effort needs to be invested in producing experimental results, and subsequently optimising the system to improve performance.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours) (Mechanical) project.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering
Supervisors: Malpress, Ray
Date Deposited: 09 Sep 2015 05:22
Last Modified: 08 Mar 2016 02:02
Uncontrolled Keywords: kinetic energy recovery, compressed gas, regenerative braking, vehicle efficiency
Fields of Research : 09 Engineering > 0902 Automotive Engineering > 090201 Automotive Combustion and Fuel Engineering (incl. Alternative/Renewable Fuels)
URI: http://eprints.usq.edu.au/id/eprint/27090

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