Wolfgang Lang

Assessment of Waste Heat Recovery From a Heavy-Duty Truck Engine by Means of an ORC Turbogenerator

This paper documents a feasibility study on a waste heat recovery system for heavy-duty truck engines based on an organic Rankine cycle (ORC) turbogenerator. The study addresses many of the challenges of a mobile automotive application: The system must be simple, efficient, relatively small, lightweight, and the working fluid must satisfy the many technical, environmental, and toxicological requirements typical of the automotive sector. The choice of a siloxane as the working fluid allows for the preliminary design of an efficient radial turbine, whose shaft can be lubricated by the working fluid itself. The systems heat exchangers, though more voluminous than desirable, are within acceptable limits. The simulated ORC system would add approximately 9.6 kW at the design point, corresponding to a truck engine power output of 150 kW at 1500 rpm. Future work will be devoted to further system and components optimization by means of simulations, to the study of dynamic operation and control, and will be followed by the design and construction of a laboratory test bench for mini-ORC systems and components.

Usage and validation of a fluid structure interaction methodology for the study of different suction valve parameters of a hermetic reciprocating compressor

The dynamics of the flatter valves inside a hermetic reciprocating compressor used in household appliances is the most important factor concerning the gas dynamic behaviour of such a compressor. Hence for a good valve design and for a reliable simulation of the compressor the ability to predict the movement of the valves is indispensable. The present paper describes a methodology which allows the prediction of the valve dynamics. For the validation of the methodology the simulation results of the suction valve dynamics have been compared with experimental data obtained out of measurements with a Laser-Doppler-Vibrometer. Furthermore the method has been used for the variation of some suction valve parameters and their influence onto the overall compressor performance has been shown. The whole methodology has been implemented into a commercial available CFD code (FLUENT) as a user defined function (UDF).

Development and validation of a one-dimensional simulation model of a hermetic reciprocating compressor for household refrigeration

In a hermetic reciprocating compressor (HRC), all components inside the shell interact thermally with each other, and thus all components inside the shell must be taken into account to get a complete thermodynamic analysis of a HRC. A one-dimensional simulation provides useful results as long as the thermal boundary conditions are well known. In this work, a procedure for the development and the validation of a one-dimensional simulation model of a HRC is elaborated. A thermal network (TNW) is added to the one-dimensional simulation model to obtain the thermal boundary conditions. A zero-dimensional model is applied for the calculation of the gas inside the plenums, the junctions and the cylinder. Five experimental test cases are proposed to check the validation and the consistency of the model. Finally, the procedure is applied for a 5.6 ccm hermetic compressor for isobutane.

A cyclic boundary condition for time delayed technical problems and its application for IC-engine simulation

The continuous improvement of numerical methods together with the increase of computer power allows the simulation of more and more complex technical problems even for large calculation domains. Growing calculation domains combined with the simulation of physically complex phenomena increase the simulation effort non-linearly and make them impracticable in the daily work of an engineer. A decrease of simulation time can be realised by the reduction of the calculation domain. In this paper, a new cyclic and time delayed boundary condition is introduced together with its application in the simulation of an IC-engine. The boundary conditions are calculated during the simulation and are set on the corresponding faces in the calculated domain. Furthermore, the data for the boundary condition is deducted from the simulation itself and therefore do not need to come from another software or measurements, what additionally reduces the pre-processing effort.