Centrifugal compressors, which serve the purpose of internal combustion engines (ICE) supercharging, have a region of unstable operation. The compressor instabilities can be distinguished as rotating stall, mild, or deep surge, depending on the compression system parameters. All these types of compressor operation should be avoided for engine durability and long service life. Therefore, it is important to provide fast, stable, and correct prediction of compressor instabilities at ICE operating cycle simulation. The experimental research was conducted for an aircraft engine compressor to measure compressor performance map in the region of unstable operation, which is usually never provided by the manufacturer, and to study the compression system operation in the mild and deep surge modes. A mathematical model was developed, based on the Moore-Greitzer approach together with the modified equation of the compressor outlet pipe airflow acceleration, and integrated into the Blitz-PRO service for ICE steady and transient operation simulation. It is shown that the suggested mathematical model correlates well with the experimental data for the compressor testbench case. The application of the developed mathematical model provides fast and stable calculations and prediction of the type of compression system instability.

No abstract

No abstract

The scheme of the cooling system is considered, which can be the basis for creating the most effi cient cooling systems for IC engines of any purpose. It is assumed that the use of any other scheme is devoid of a rational basis. The scheme consists of two connected circulation circuits, in one of which the coolant fl ow rate is an order of magnitude less than in the second. The engine is included in a circuit with increased coolant fl ow. All heat exchangers are in the second circuit. Rules for the formation of such systems are formulated. The basis of the method for calculating such systems is considered. It is indicated that the fl ow rate through each heat exchanger must be determined by calculation to ensure the maximum effi ciency of the cooling system. The considered scheme allows to provide the maximum possible depth of charge air cooling, if its temperature is not specifi ed, or to ensure the minimum cost and compactness of the cooling system, if this temperature is known. The scheme allows regulating the temperatures of the cooling fl uids of the system with all kinds of changes in the engine operating conditions and the ambient temperature.

No abstract