Nowadays, on average, two thirds of the fuel energy consumed by an engine is wasted through the exhaust gases and the cooling liquid. The recovery of this energy would enable a substantial reduction in fuel consumption. One solution is to integrate a heat recovery system based on a steam Rankine cycle. The key component in such a system is the expander, which has a strong impact on the system’s performance. A survey of different expander technologies leads us to select the reciprocating expander as the most promising one for an automotive application. This paper therefore proposes a steady-state semi-empirical model of the expander device developed under the Engineering Equation Solver (EES) environment. The ambient and mechanical losses as well as internal leakage were taken into account by the model. By exploiting the expander manufacturer’s data, all the parameters of the expander model were identified. The model computes the mass flow rate, the power output delivered and the exhaust enthalpy of the steam. The maximum deviation between predictions and measurement data is 4.7%. A performance study of the expander is carried out and shows that the isentropic efficiency is quite high and increases with the expander rotary speed. The mechanical efficiency depends on mechanical losses which are quite high, approximately 90%. The volumetric efficiency was also evaluated.

Reducing fuel consumption is a prime objective in the automotive industry in order to meet regulatory and customer demands. Variable valve actuation offers many opportunities for improving the spark ignition engine’s performance in areas such as fuel economy and pollutant emissions. Our studies revealed that the ability to control maximum intake valve lift does indeed offer the ability to control intake air mass, but also has the added benefit that it improves the fuel-air mixing process thanks to an increased turbulence, caused by the increased intake flow velocity. This is particularly important at idle and low part loads when low maximum lifts are to be used for improving the fuel economy or for achieving the required power. The paper focuses on the experimental results obtained when approaching idle operation with different intake valve laws. Results indicating the potential of using low intake valve lift for fuel economy and cyclic dispersion improvement are presented in this paper.

The purpose of this study is the dimensioning of the cylindrical mixing chamber of a compressible fluid ejector used in particular in sugar refineries for degraded vapor re‑compression at the calandria exit, during the evaporation phase. The method used, known as the “integral” or “thermodynamic model”, is based on the model of the one‑dimensional isentropic flow of perfect gases with the addition of a model of losses. Characteristic curves and envelope curves are plotted. The latter are an interesting tool from which the characteristic dimensions of the ejector can be rapidly obtained for preliminary dimensioning (for an initial contact with a customer for example). These ejectors, which were specifically designed for the process rather than selected from a catalog of standard devices, will promote energy saving.

In recent decades, the approach known as Finite-Dimension Thermodynamics has provided a fruitful theoretical framework for the optimization of heat engines operating between a heat source (at temperature T_hs) and a heat sink (at temperature T_cs). We will show in this paper that the approach detailed in a previous paper [1] can be used to analytically model irreversible heat engines (with an additional assumption on the linearity of the heat transfer laws). By defining two dimensionless parameters, the intensity of internal dissipation and heat leakage within a heat engine were quantified. We then established the analogy between an endoreversible heat engine and an irreversible heat engine by using the apparent temperatures (T_cs → Tλ,φ cs, T_hs → Tλ,φ hs) and apparent conductances (K_h → Kλ h, K_c → Kλ c). We thus found the analytical expression of the maximum power of an irreversible heat engine. However, these apparent temperatures should not be used to calculate the conversion efficiency at the optimal operating point by analogy with the case of an endoreversible heat engine.