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Considerations for starting combustion engines with AC machines

Monroy Mauricio, Romero Carlos A., Henao Edison

Diagnostyka

2023

Vol. 24, No. 1

art. no. 2023102

To initiate its combustion cycles, internal combustion engines require a minimum rotational speed that can be given from several sources (muscular, electrical, pneumatic, among others). Advantages of initiating an ICE with an AC electrical machine is that it can integrate starter motor and generator in one device, provide a linear ramp of acceleration when starting, and assist the ICE in torque production. This article illustrates considerations for the design of a starting system with an AC electrical machine. Initially, criteria of torque, rotational speed and power requirements are analysed, considering resistances of compression, friction, and inertia of the slider-crank mechanism, as well as accessories, with a preliminary experimental validation. Also, types of three-phase AC electrical machines are put to comparison, as well as their associated electronic components needed for driving them in each case, concluding that AC induction machines require a complex 4-quadrant inverter. PM synchronous machines require a simpler inverter, but with highly specified power electronics components. The classical wound rotor machine requires the simplest inverter, with unidirectional power flow, less power transfer losses and less critical power electronics components. Finally, considerations for using of a battery assisted with supercapacitor as complementary DC power source are made.

Experimental study of mechanical losses of single-cylinder spark-ignited engine

Romero Carlos A., Henao Edison, Ramírez Juan

Diagnostyka

2021

Vol. 22, No. 3

13--24

In this study, the mechanical losses of a single-cylinder spark-ignited Robin EY15 engine were experimentally determined and analysed by the indicated method. The effects of the load and speed on the mechanical loss balance were also analysed. The tests were conducted on a test bench equipped with a DC motor generator at speeds between 1500 and 4800 min-1 and three load levels of 25, 50, and 100%. The results showed that the mechanical efficiency ranges between 22.5% and 83.2% for the tested engine and the evaluated operation points, attaining the highest efficiency under the full load and 2100 min-1. However, at this load level, the efficiency is reduced to 29% with the increase in the rotation speed. Concurrently, the pumping losses contribute up to 58.7% of the total losses, which indicates that their contribution is even higher than the sum of the other components under low load conditions. However, as the load increases, this contribution decreases to 18% for lower rotation regimes. In addition, the experimental results of the total mechanical losses were compared with some numerical correlations found in the literature. Finally, some empirical correlations were proposed for the mechanical efficiency calculation of the tested engine.