MECHANICAL ENGINEER DEPARTMENT PhD THESIS DEFENSE BY ATACAN ORAL

Title: Dynamic Model Development for Highly Efficient Inverter Compressor.

Speaker: Atacan Oral

Time: 17.03.2023, 11:00

Place: Online via Zoom

Thesis Committee Members:

Prof. İsmail Lazoğlu (Advisor, Koç University)

Prof. Demircan Canadinç (Koç University)

Asst. Prof. Levent Beker (Koç University)
Prof. M. Cemal Çakır (Bursa Uludağ University)
Prof. Özgen Akalın (İstanbul Technical University)

Abstract:

The heart of a household refrigerator can be assumed as the compressor since it receives the refrigerant, compresses it and allows gas to circulate inside the refrigeration cycle. Even though there are different types of compressors in the market, reciprocating compressor is the most common one at the refrigerators. Due to energy regulations that become more strict day by day because of global warming, the challenge between compressor manufacturers is to producing the most energy efficient compressor. In order to reduce the energy dissipation and increase the efficiency, the fundamentals behind the pyhsics used in the compressor must be understood clearly. Moreover, even though dynamics and mechanics disciplines are investigated in this thesis, the relationship with thermodynamics and flow dynamics must be considered as well. In this thesis, a comprehensive mathematical model of a reciprocating compressor is established by including all design parameters and considering all force sources for both steady state and startup behaviour where the highest vibration and noise are observed. The model validations are conducted by specially developed experimental setups. Moreover, the components that play a significant role in dynamic response of the compressor such as springs or discharge tube are investigated individually, further optimizations are proposed to reduce the design time and both vibration noise levels. A novel design methodology is proposed for the discharge tube for the first time in the world and mathematics is included in the design process. Furthermore, to reduce startup and shutdown vibration and noise, a novel design addition, called transient vibration reducer (TVR), is utilized. TVR is a passive damper that operates as a pseudo-active damper due to its stepwise structure, interacting with the motion of the compressor only above predetermined limits of body displacement without affecting or compromising steady-state performance. Finally, the startup and shutdown position map data of the crankshaft is formed with an all-round experimental setup for the first time in the literature. Suggestions are made to have a smooth startup behavior, implemented on a compressor and validated with experimental studies.