The Pneumatic Hybrid Vehicle - A New Concept for Fuel Consumption Reduction

Research output: ThesisDoctoral Thesis (compilation)


Urban traffic involves frequent acceleration and deceleration. During deceleration, the energy previously used to accelerate the vehicle is mainly wasted on heat generated by the friction brakes. If this energy that is wasted in traditional internal combustion engines (ICE) could be saved, the fuel economy would improve. Today there are several solutions to meet the demand for better fuel economy and one of them is the pneumatic hybrids. The idea with pneumatic hybridization is to reduce the fuel consumption by taking advantage of the, otherwise lost, brake energy.
In the work presented in this study heavy duty Scania engines were converted to operate as pneumatic hybrid engines. During pneumatic hybrid operation the engine can be used as a 2-stroke compressor for generation of compressed air during vehicle deceleration (compressor mode) and during vehicle acceleration the engine can be operated as an air-motor driven by the previously stored pressurized air (air-motor mode). The compressed air is stored in a pressure tank connected to one of the inlet ports. One of the engine inlet valves has been modified to work as a tank valve in order to control the pressurized air flow to and from the pressure tank.
In order to switch between different modes of engine operation there is a need for a fully variable valve actuation (FVVA) system. The engines used in this study are equipped with pneumatic valve actuators that use compressed air in order to drive the valves and the motion of the valves is controlled by a combination of electronics and hydraulics.
Initial testing concerning the different pneumatic hybrid engine modes of operation was conducted. Both compressor mode (CM) and air-motor mode (AM) were executed successfully. Optimization of CM and AM with regards to valve timing and valve geometry has been done with great improvements in regenerative efficiency which is defined as the ratio between the energy extracted during AM and the energy consumed during CM.
A model of the pneumatic hybrid engine was developed in the engine simulation package GT-Power and validated against real experimental data. After a successful validation process, the model was used for parameter studies. In this way the influence of important parameters such as tank valve diameter, tank valve opening and closing could, together with their effect on the pneumatic hybrid engine performance, be investigated.
A pneumatic hybrid vehicle model was developed in Matlab™/Simulink. The engine part of the vehicle model consisted of engine data obtained from the GT-Power model. Vehicle drive cycle simulations showed that the fuel consumption of a conventional bus could be reduced by up to 58% when converted to a pneumatic hybrid bus.


  • Sasa Trajkovic
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Other Mechanical Engineering


  • VVA, Regenerative, Air-motor, Compressor, Pneumatic, Hybrid, Vehicle, Electric Hybrid, Drive Cycle, GT-Power, Simulink, FPGA
Original languageEnglish
Awarding Institution
Supervisors/Assistant supervisor
Award date2011 Jan 21
Print ISBNs978-91-7473-072-2
Publication statusPublished - 2010
Publication categoryResearch

Bibliographic note

Defence details Date: 2011-01-21 Time: 10:15 Place: Lecture hall M:B, M-Building, Ole Römersväg. 1, Lund University Faculty of Engineering External reviewer(s) Name: Filipi, Zoran Title: Prof. Affiliation: W.E. Lay Automotive Lab, Ann Arbor, USA. ---

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Per Tunestål, Bengt Johansson, Sasa Trajkovic & Urban Carlsson

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