Arnaud Legros

Sizing models and performance analysis of volumetric expansion machines for waste heat recovery through organic Rankine cycles on passenger cars

This paper aims at helping designers of waste heat recovery organic (or non-organic) Rankine cycles on internal combustion engines to best select the expander among the piston, scroll and screw machines, and the working fluids among R245fa, ethanol and water. The first part of the paper presents the technical constraints inherent to each machine through a state of the art of the three technologies. The second part of the paper deals with the modeling of such expanders. Finally, in the last part of the paper, performances of the various Rankine systems are compared and a decision array is built to select the most appropriate couple of fluid and expander.

Investigation on a scroll expander for waste heat recovery on internal combustion engines

In the present article, a model of scroll expander will be introduced. This model is able to evaluate the performance of a given machine with influence of the geometry. Several losses are also included by the model such as internal leakages, heat transfers or mechanical losses. The forces generated by the gas pressure on the involutes can also be calculated.

Positive displacement expanders for Organic Rankine Cycle systems

Abstract The first part of this chapter introduces the main considerations about positive displacement expanders. The second part presents the principle of operation of major types of positive displacement expanders as well as their relevant mechanical characteristics. The piston, the scroll, the twin-screw, and the vane expanders are described in detail. The chapter also briefly introduces the roots, the trochoidal, and single-screw expanders. For each type of expander, the technical limitations are listed. In the third part of this chapter, the theory of thermodynamics of displacement expanders is developed, leading to the definition of appropriate performance indicators. Finally, the chapter treats the integration of displacement expanders into Organic Rankine Cycle (ORC) systems by summarizing the selection criteria, introducing major considerations about preliminary design, and explaining how the expander can be used in the control of ORC systems.

Variable thickness scroll compressor performance analysis—Part I: Geometric and thermodynamic modeling:

In order to investigate the performance of variable thickness scroll compressors, a detail mathematical modeling based on energy and mass balances is established in this two-part. In part I, the geometric modeling and thermodynamic modeling are developed. The profile based on circle involute, high order curve, and arc is built up using the base line method. The volume of working chambers from suction to discharge is defined. Thereafter, the evolution and derivative of the working chamber volume with respect to the orbiting angle are discussed. The energy and the mass balance for working chamber are described. Suction gas heating, radial and flank leakage, heat transfer between the working fluid, scroll wraps and plates are considered in the thermodynamic modeling. The established geometric modeling and thermodynamic modeling can provide better understanding of the variable thickness scroll compressor working process. The dynamical modeling and model validation are reported in part II.

Variable thickness scroll compressor performance analysis—Part II: Dynamic modeling and model validation

In order to investigate the performance of variable thickness scroll compressor, a detail mathematical modeling based on energy and mass balances is established in this two-part. In part II, dynamic modeling and model validation are developed. Temperature, pressure, mass flow of working chambers, friction loss power of moving parts, efficiency, and shaft power are investigated by solving the mathematical modeling. The experimental rig for variable thickness scroll compressor based on involute of circle, high order curve and arc is set up. From the comparison of the simulated and measured data, it can be seen that the compressor model predicts the mass flow, discharge temperature, and shaft power very well. So the proposed mathematical modeling can accurately describe all the suction, compression, and discharge processes for variable thickness scroll compressor.

Modelling, sizing and testing a scroll expander for a waste heat recovery application on a gasoline engine

Waste heat recovery technologies in a mobile application emerge every time energy becomes a valuable resource. It has been the case in the 70s with oil crisis and it is starting to regain some interests now due to the continuously rising price of oil and due to the restrictive standards imposed by the different governments. This paper deals with the recovery on the exhaust gases of an internal combustion engine by using a Rankine system. The study focuses on the expander, which is one of the most important components of the system. The use of a scroll expander operating with steam is currently investigated through simulation and experimentation. This paper presents the modelling of a scroll expander. The model is a detailed model including various losses such as leakage, friction or under or over expansion. This model has been used to design and size a tailor-made scroll expander. This was necessary due to the small amount of expanders on the market and also to have a machine that fits our application. After designing the machine, a prototype has been built. It has also been tested on our prototype bench of waste heat recovery on a gasoline engine, by means of a Rankine cycle. Measured performance will be presented, analysed and compared to predictions by the model. The first results will be presented here and discussed in order to give recommendations for the design of next prototypes.