Abstract
A gas‐engine heat pump (GHP) is driven by an internal combustion engine fueled by natural gas. The objective of this research is to model the combustion and emission characteristics of a GHP engine and experimentally validate the model. In addition, the exhaust gas recirculation (EGR) and intake boost systems were numerically investigated to find an NO and NO2 (NOx) reduction strategy. The ignition and combustion processes were modeled using the level set method and the DPIK model, and experimental data was used for validation. The models predicted engine performance and emissions for various equivalence ratios and spark timing. The study results show that late spark timing leads to reductions of the indicated specific fuel consumption (ISFC) and NOx emission, and the ISFC and NOx emissions increase with the equivalence ratio until the equivalence ratio reaches 0.9. The indicated mean effective pressure (IMEP) increases with boost pressure and decreases with increase of EGR rate. Reductions of NOx emission and high IMEP can be achieved by employing a boost system and operating at the optimal operating point, from the performance and emission map.
Highlights
Heat pumps used to control temperature are generally driven by electricity
The gas engine for a gas‐engine heat pump (GHP) is fueled by liquefied natural gas (LNG) and power from a natural gas engine‐driven compressor, which operates the air conditioning and heating system via liquefaction and evaporation of refrigerant
Since gas fuel is directly converted into mechanical power in a gas engine, the efficiency of a GHP is significantly affected by the efficiency of the natural gas engine
Summary
Heat pumps used to control temperature are generally driven by electricity (electric heat pump; EHP). Electricity used as the power source of an EHP is generated by an electric power station using fossil fuels or other energy sources, and the EHP converts the electricity to mechanical energy to drive the compressor. This process of fossil fuels to the heat pump has two major energy conversion losses and areas of low efficiency, especially in the heating process. A gas engine‐driven heat pump (GHP) uses natural gas to operate the heat pump and drive the compressor. Research on natural gas engines is important to GHP research
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