Background: The purpose of this research is to study the solutions for improving
the efficiency of a micro combined heat and power (m-CHP) system based on OHVG
(OverHead Valve Gas fueled) engine.
Method: In this regard, the effects of valve timing and changing the camshaft on the power
and fuel consumption of the engine have been numerically and experimentally investigated.
The tests have been performed for engine speed range from 1000 rpm to 3500 rpm, while the
engine's fuel was natural gas. The numerical results are found to be in good agreement with
experimental ones. The effect of changing the valve timing and camshaft on the performance
of the m-CHP has been investigated through the experiments in the test room. The engine
speed was 1500 rpm; output hot water was fixed at 55oC; and output electrical power varies
from 8 kW to 13 kW in the experiments.
Results & Conclusion: The experimental results of the engine test indicate that, by changing
the camshaft for full load operation and speed 1500 rpm, engine torque and volumetric efficiency
improved by 7.2% and 6.0%, respectively, and fuel consumption decreased by 0.8%.
According to the results, the best point for the performance of m-CHP is close to the full
load of the electrical power because by increasing the electrical load, electrical efficiency increases
from about 25.9% to 32.3%, while the thermal efficiency decreases from about
61.9% to 56.1%.