<div>Vapor compression cycles are the most common method used to provide cooling to environments. In the residential area, refrigerator/freezers as well as air conditioners/heat pumps almost exclusively use vapor compression cycles. The driving force behind a vapor compression cycle is the compressor, where a variety of compressor types are used in the same application. While reciprocating compressors are found in the majority of refrigerator/freezers, scroll compressors are predominantly used in residential air conditioners. Yet other compressors have emerged as replacements due to increased efficiency. A R134a oil-free prototype scroll compressor and a R134a reciprocating compressor are operated in a hot-gas bypass test stand under refrigerator/freezer conditions to compare performance. Additionally, a R407C scroll compressor and a R410A rotary compressor are operated in a compressor calorimeter under air conditioning/heat pump conditions to compare performance. Experimental results show that the reciprocating compressor far outperforms the prototype scroll compressor in the refrigerator/freezer application, while the performance between the scroll and rotary compressors are almost equal in the air conditioning application.</div><div>Pressure fluctuation at compressor discharge is also measured in the compressor calorimeter to determine feasibility of applying a novel muffling design to air conditioning compressors, although it was found that traditional muffling methods currently used are effective to a degree such that this new method is unwarranted. Data from the compressor calorimeter is also used to investigate the accuracy of the AHRI 540 10-Coefficient Correlation compressor map in predicting performance both inside and outside the tested operating conditions. The AHRI 10-Coefficient Correlation achieves high accuracy inside tested operating conditions but is inept in extrapolating performance, where other map correlations are more accurate.</div>

This thesis presented a sensor-less permanent magnet synchronous motor (PMSM) driver for controlling air-conditioner rotary compressor speed. In this thesis, a quasi-sine pulse-width modulation (PWM) driving method was proposed. Furthermore, the current feedback control scheme and rotor magnet pole position detection were included. The system structure was implemented by using a digital signal processing (DSP) platform. The proposed driving scheme was compared with the square-wave driving without current feedback and six-step square-wave driving method with current feedback. Moreover, the passive and shunt semi-active power factor correction (PFC) technique were researched for the air-conditioner application. Experimental results demonstrated that the system power factor could be improved by the proposed shunt semi-active PFC method. Besides, the proposed sensor-less quasi-sine PWM driving method implemented in an air-conditioner compressor driver was capable of reducing the magnitude of rotational speed ripples, compressor vibration, and system power consumption.

Abstract: This paper presents the results of an experimental investigation into the application of inverter-based variable speed drives to positive displacement rotary compressors. Designs and implements a DSP-microprocessor based of an inverter drive for high-efficiency compressor used in air conditioner. We control the compressor with sine PWM and V/F scheme. Permanent magnet synchronous motor has potential for energy saving in general applications on compressor drives. Permanent magnet synchronous motor drives are used for applications like compressors¡Awhere high dynamic performance is not a demand¡Asimple V/F control strategies may be sufficient to obtain the required control performance. For energy saving to find the best control strategy for an inverter drive for high efficiency compressor used in air conditioner.

[pt] A presente dissertação trata do projeto, construção e ensaio preliminar de um novo modelo do compressor Kopelrot. É uma máquina de deslocamento positivo baseada em seis patentes depositadas desde 1998. Esta tecnologia está em desenvolvimento há aproximadamente 8 anos, tendo gerado artigos e dissertações, assim como a construção de dois protótipos. É apresentada, inicialmente, uma revisão dos trabalhos publicados sobre a tecnologia Kopelrot. Foram construídos junto ao novo modelo de compressor Kopelrot um novo sistema de acionamento e uma base para a fixação de ambos a um motor elétrico. Durante a elaboração dos desenhos foram realizadas simulações preliminares da geometria para definir a fabricação de algumas peças importantes. A base permite regular a excentricidade entre os eixos de centro do compressor e do sistema de acionamento e, dessa forma, variar a vazão volumétrica do compressor. Simulou-se a variação de volume no interior da câmara com o conjunto compressor Kopelrot/Sistema de acionamento, ajustado para 5 excentricidades diferentes, a fim de mapear o comportamento do Kopelrot quando sua capacidade é variada, deslocando-se os eixos de centro do compressor e do sistema de acionamento. Para as excentricidades escolhidas, foram calculadas, a partir de modelo termodinâmico simplificado, as variações de pressão, temperatura e massa no interior da câmara do compressor. Valores globais de potência consumida e eficiência volumétrica também foram calculados. Durante o funcionamento do protótipo identificaram-se alguns problemas tipicamente encontrados em tecnologias inovadoras. Devido a esses problemas, não foi possível a realização dos testes do compressor operando em condições normais de pressão. / [en] The present dissertation addresses the design, construction, simulation and preliminary tests of an innovative positive displacement rotary compressor. A review is presented on the previous works, papers and dissertations, based on this new this new Kopelrot technology. A new prototype, employing a new driving system, was manufactured. The main feature of the machine is that, by adjusting the eccentricity between compressor cylinder and driving mechanisms axis, a variable capacity device is obtained. Design, manufacturing and assembly of components and subsystems of the compressor are presented in detail. Design data of the compressor allowed for a simple thermodynamic simulation model to be developed. Main conclusions of the simulation are that a full positive displacement compression cycle can be attained with the Kopelrot technology and that use of discharge and suction valves is required in order to have the compressor operating under different conditions.

<p>  </p> <p>Part I studies the lubricant sprays and droplets in a rotary compressor. Air conditioning (AC) systems are now widely used in residential and commercial environments, while the compressor is the most important element in the AC system, and rotary compressors are often used in split AC appliances, whose number is estimated to reach 3.7 billion in 2050. In a rotary compressor, the lubricant oil atomizes into small droplets due to the differential pressure in and out of the cylinder. Part of the lubricant oil droplets carried by the refrigerant vapor will ultimately exhaust from the compressor through the discharge pipe. The ratio of the discharged oil volume to the total oil volume is characterized as the Oil Discharge Ratio (ODR). High ODR will reduce the reliability of the compressor and deteriorate the heat transfer of the condenser and the evaporator, resulting in decreased efficiency. Thus, controlling the ODR is a key issue for the design of the rotary compressor.</p> <p>In Part I, rotary compressors were modified to provide optical access into its internal space, i.e., the lower cavity (refers to the space between the cylinder and the motor), above the rotor/stator, and at the discharge tube level. The modified rotary compressors’ operation was supported by a test rig which provided a wide range of operating conditions, e.g., pressure and frequency. Thus, in-situ optical measurements, e.g., shadowgraph and holograph, can be performed to visualize the lubricant sprays and droplets in the rotary compressor. An image processing routine containing the Canny operator and Convolutional Neural-Network was developed to identify droplets from high-resolution shadowgraph images, while Particle Image Velocimetry (PIV) and Optical Flow Velocimetry (OFV) were applied to calculate the spray and droplet’s velocities with time-resolved shadowgraph images. Parallel Four-Step Phase Shifting Holograph (PFSPSH) located the droplets’ positions in a three-dimensional volume under the specific operating condition.</p> <p>Both primary and secondary atomization were observed in the rotary compressor, while primary atomization is the major source of droplet production. The droplet size distributions versus the frequency, vertical direction, radial direction, and pressure are obtained. It is observed that the droplet characteristic mean diameters increase with the frequency and pressure. They also become larger in the outer region above the rotor/stator and keep constant in the radial direction at the discharge tube level. The penetration velocity of the lubricant spray is calculated in the lower cavity. An outward shift of the jet core combined with an outward velocity component was observed. Additionally, horizontal swirling velocity above the rotor/stator and at the discharge tube level and the vertical recirculation velocity above the rotor/stator are characterized. The volume fraction of droplets was also characterized under the specific operating condition. The results provide detailed experimental data to set up the boundary conditions used in CFD. They also show that the droplets in the upper cavity are mostly from the discharge process of the cylinder in the lower cavity. The results support a droplet pathway model in the rotary compressor, which can guide the optimization of future rotary compressors.</p> <p>Evaporation is commonly seen in hydrology, agriculture, combustion, refrigeration, welding, etc. And it always accompanies heat and mass transfer at the liquid-gas interface and is affected by the substance’s properties, the environment’s pressure, temperature, convection, and so on. PFSPSH in Part I aims to retrieve the phase information for holograph reconstruction. Part II further explores the application of the PFSPSH technology in Part I to observe the evaporation process of acetone, where the phase disturbance caused by the vapor is used to reconstruct the vapor concentration in space. The method is called Parallel Four-Step Phase Shifting Interferometer (PFSPSI). The first case studies the evaporation process of the acetone contained in a liquid pool with uniform air flow in a low-speed wind tunnel. The mole fractions of the acetone vapor near the liquid-air interface with different air speeds are characterized. The second case studies the evaporation process of acetone droplets levitated by an ultrasound levitator. The mole fraction of the acetone vapor near the liquid-air interface is characterized by assuming an axisymmetric field and using the analytical solution of the inverse Abel transform. The asymmetric pattern of the acetone vapor field is observed, which is considered due to the drastic sound pressure change at the stand wave location produced by the ultrasound levitator. The mass transfer of the evaporation process by the vapor’s mole fraction is calculated and compared with the mass transfer calculated by the droplet size change. It is observed that the mass transfer by the vapor’s mole fraction is generally smaller than the mass transfer calculated by the droplet size change, which can be explained by the convection process induced by the acoustic streaming.</p>