Analysis of rolling bearing power loss models for twin screw oil injected compressor

The mechanical losses inside a screw compressor limit the performance of the compressor in terms of efficiency. These losses arise due to relative motion between elements inside the screw compressor. The estimation of mechanical losses predicted in the literature is around 10-15% of the total shaft power. One of the elements which contribute significantly to these losses is rolling element bearings. There are numerous mathematical models available which predict power losses in the rolling bearings. The objective of this paper is to study different models to predict power loss for rolling bearings and to predict the power losses for the bearings used for oil injected, twin screw compressor. A comparison between different power loss models for different operating conditions of compressor is also presented in this paper and results of analysis are compared with available experimental observations. The analysis helps to determine suitable power loss model for different operating conditions and more realistic predictions of the power losses. This allows designers for more accurate estimation of the performance of screw compressors

Development and Design of Energy Efficient Oil-Flooded Screw Compressors

It is estimated that about 17% of the world's generated power is used for compression. Thus all, even minor improvement of the efficiency of compressors will substantially reduce CO2 emission. This paper presents development of family of energy efficient oil-flooded screw compressors for Kirloskar Pneumatic Company Ltd. The developmental techniques adopted to improve efficiency such as introduction of superior 'N' rotor profile, rotor clearance management, performance calculation using 3D CCM (Computational Continuum Mechanics), direct parametric interface to CAD (Computer Aided Design), which contains bearing selection for complete 3D solid modelling. Also, contemporary prototyping and experimental investigation is supported by the fully computerised data acquisition and processing. The cumulative improvement of all these elements of the design process resulted in a very efficient machine which guarantees the competitive position of Kirloskar Pneumatic Company Limited in the screw compressor market

Investigation of Mechanical Losses in Oil-flooded, Twin-screw Air Compressors

Approximately 15-20% of the world's generated electrical power is consumed by compressors where rotary oil-lubricated compressors account for nearly 60% of the entire air compressor market. According to market research, the demand for those of the twin-screw type is likely to increase at a Compound Annual Growth Rate (CAGR) of 5% from 2021 to 2026. Thus, even minor improvements in their efficiency can lead to a substantial reduction in carbon footprint. With the increasing demand for more energy-efficient machines, one of the ideas in the screw compressor for optimising their performance is to focus on reducing power loss. To do this, the elements contributing to the power loss and their quantification need to be understood. Analytical procedures for the design and performance estimation of twin screw compressors are well-developed and widely available, but the determination of power loss, in oil-flooded machines is only approximated. This study focuses on finding the elements of power loss arising from the oil-injected, twin-rotor screw compressor and quantifying the contribution of individual elements' power loss for different compressor sizes. The approach is to find available technologies and develop new methods for the prediction of power loss in elements like rolling element bearings, shaft seals, oil drag and transmission. After a comparison of available methods bearing power loss prediction and literature available experimental results, the Harris model fits best for the prediction of power loss arising from rolling element bearing. Based on the semi-analytical approach and experimental measurement presented by Frölich et al. (2014) and Engelke (2011), respectively, a combined model is developed for the prediction of power loss from the shaft seals. As the oil in the compressor experiences inertial and pressure-induced flow, a combined Couette-Poiseuille flow model is established for drag loss estimation. This drag loss model is experimentally validated with different screw rotor profile configurations. It is understood from the predictions for total power loss and its comparison for different sizes of the compressor, that the bearing power loss and oil drag loss are the main contributing elements to the total power loss whereas shaft seal power loss is negligible. With the use of the proposed method and parametric analysis, the elements contributing to power loss and the effect of different operational parameters like pressure ratio, speed and size of the compressor are analysed. This can help the designers to optimise the working of the compressor at the design stage

Identification and analysis of screw compressor mechanical losses

Screw compressors are compact machines, used for a wide range of applications where gases or vapours are required to be delivered at moderate pressures with high efficiency and reliability. They are most effective when the compressed medium requires power inputs, approximately in the 10 kW - 1-2 MW range. At lower inputs alternatives such as reciprocating and scroll compressors are preferable and at higher inputs turbo-compressors are more suitable. In industrialised countries, compressors absorb 15-20% of the total electrical power generated. Hence there is a continuing demand to improve their efficiency. This is normally expressed as the specific power consumption, which is the power required to compress unit mass of gas delivered. There already exist mathematical models to assist in the design of such machines and to estimate their performance, which include the estimation of the dynamic loads acting on the rotors and bearings and these loads determine their mechanical efficiency. However, these models do not estimate the magnitude of the mechanical losses, which are only guesstimated as an additional increment to the power required to compress the gas. Such an approximation does not enable the optimum selection of bearings and lubricating oil to minimise the frictional power losses. The aim of the study, described in this paper, was to estimate the effect of the individual parameters responsible for mechanical power loss in oil injected screw compressors and is focussed on the losses incurred in the gear box, bearings and shaft seals. It was found that in the gearbox, meshing, bearing and seal losses all increase both with speed and gear ratio. In the main rotors, it was found that sliding friction losses in the bearings are not significantly affected by the radial load, nor are rolling friction losses significantly dependent on the axial load. However, both axial and radial loads have a significant effect on the total frictional power loss. Lubricant viscosity affects the frictional power losses but the oil level does not

Optimisation of processing variables of Kenaf derived cellulose reinforce polylactic acid

Optimisation of composite processing variables (temperature and time) was carried out by monitoring both the stabilisation zone (to ensure composite is well mix at sufficient duration) and the maximum mixing temperature (below 200 °C to avoid fibre degradation) by analysing mixing torque curves upon compounding 5 wt % KDC/PLA using Brabender internal mixer at 160-180 °C for 10, 20 and 30 min., respectively. The composites were pressed and cut into tensile test specimens prior to testing. The 5 wt % KDC/PLA composite demonstrated an optimum tensile strength at three combinations of variables, however the best condition was chosen at 170 °C for 30 min for preparation of composites at various KDC loading (0-60 wt %). The effect of KDC loading on the tensile strength and modulus of composites were investigated. The results demonstrated that increasing KDC loading from 0-60 wt % enhanced the tensile strength and the tensile modulus up to 34 and 107 %, respectively. The a-cellulose was initially derived from kenaf fibre (from bast) by removal of lignin and hemicellulose via chemical (chlorination and mercerization) processes. The absence of these components in the FTIR spectral peaks confirms their removal after been chemically treated

Intensitas dan prevalensi ektoparasit dan endoparasit pada ikan belanak Liza macrolepis (Smith, 1846) di perairan pantai Barat-Selatan Aceh

The Largescale mullet Liza macrolepis is a common fish found in estuaries and coastal areas and the fish is used as a source of protein by coastal communities. This study aims to analyze the prevalence and intensity of parasitic infected on mullets harvested from the waters of the West - South Aceh. This research was conducted from March to April 2019 in 8 locations, namely; Estuary Aceh River, Gampong Jawa, Banda Aceh city, Coastal Ujong Pancu, Peukan Bada, Aceh Besar, Estuary Teunom River, Calang, Aceh Jaya, Estuary, and Coastal Kuala Bubon, Samatiga, West Aceh, Estuary Nagan River Langkak Kuala Tuha Nagan Raya, Estuary, and Coastal Susoh, Blang Pidie, Southwest Aceh, Estuary and Coastal Indra Damai, Kluet Selatan, South Aceh and Estuary Sua- Sua River and Ujong Umo River, Simeulue. A total of 343 samples were examined for ectoparasites and endoparasites at the Laboratory of Hatchery, Faculty of Marine and Fisheries, Syiah Kuala University. The results showed that there were seven species of parasites, infected the mullet samples namely; Ectoparasites (Cymanthoa sp., Ergasilus sp., Lernanthropus sp., Monstriloida sp., Myxobolus sp.) and Endoparasites (Nematodes and Trematodes). Prevalence value of Kota Banda Aceh was 33% ectoparasites and 28% endoparasites), Aceh Besar was 21% ectoparasites and 15% endoparasites, Aceh Jaya was 4% ectoparasites and 4% endoparasites, Southwest Aceh was 2% ectoparasites and 2% endoparasites, Simeulue was 9% ectoparasites and 9% endoparasites. It is concluded that the higher prevalence and intensity were found in fish samples from Banda Aceh and Aceh Besar, while no fish from Nagan Raya and Aceh Selatan were infected by parasites.Keywords:ParasiteCoastalEstuaryPollutant ABSTRAKIkan belanak Liza macrolepis sering dijumpai di muara dan pesisir pantai dan dijadikan sebagai sumber protein oleh masyarakat pesisir. Saat ini belum ada penelitian terkait jenis-jenis parasite yang menyerang ikan belanak di perairan Aceh, khususnya di pantai Barat Selatan Aceh. Oleh karena itu, penelitian ini bertujuan untuk menganalisis prevelensi dan intensitas parasit pada ikan belanak di perairan Barat Selatan Aceh. Penelitian dilakukan sejak Maret sampai April 2019 meliputi 8 lokasi, yaitu; Muara Krueng Aceh, Gampong Jawa Kota Banda Aceh, Ujung Pancu, Peukan Bada Aceh Besar, Muara Krueng Teunom, Calang Aceh Jaya, Muara Sungai/Pesisir Kuala Bubon, Samatiga Aceh Barat, Muara Krueng Nagan, Kuala Tuha Nagan Raya, Muara/Pesisir Susoh, Blang Pidie Aceh Barat Daya, Muara/Pesisir Indra Damai, Kluet Selatan Aceh Selatan dan Muara sungai Ujong Umo dan muara sungai Sua – Sua, tepah barat dan Simeulu Timur, Simeulu.  Metode digunakan adalah preparat ulas (Smeer method). Sebanyak 343 sampel dibedah untuk dilakukan pemeriksan ektoparasit dan endoparasit di Laborarorium Pembenihan Ikan, Fakultas Kelautan dan Perikanan, Universitas Syiah Kuala. Hasil penelitian ditemukan 7 jenis parasit, ektoparasit (Cymanthoa sp., Ergasilus sp., Lernanthropus sp., Monstriloida sp., Myxobolus sp.) dan Endoparasit (Nematoda dan Trematoda). Nilai prevalensi; Kota Banda Aceh (33% ektoparasit, 28% endoparasit), Aceh Besar (21 % ektoparasit, 15% endoparasit), Aceh Jaya (4% ektoprasit dan 4%endoparasit), Aceh Barat Daya (2% ektoprasit dan 2% endoparasit) Simeulu (9% ektoparasit dan 9% endoparasit). Disimpulkan bahwa prevelensi dan intensitas parasit tertinggi dijumpai pada sampel ikan dari Banda Aceh dan Aceh Besar, sedangkan ikan sampel dari Nagan Raya dan Aceh Selatan bebas dari serangan parasit. Kata kunci:ParasitpesisirMuara sungaiPencemara

Experimental validation of the screw compressor oil drag model for various rotor profiles

Injecting oil inside the compressor chambers of the oil-flooded, twin-screw compressors has several advantages. Oil cools the compressing fluid upon mixing with it and hence the compression process is brought nearer to the ideal isothermal compression process. The oil also serves as a lubricant between the meshing rotors and other clearance gaps in the compressor. The thin film of oil formed in the clearance gaps prevents internal leakages too; enhancing the volumetric efficiency of the compressor. Among these desirable effects of injecting oil in screw compressors, there is an undesirable effect too. The interaction (friction) of oil films formed in various clearance gaps with the rotors leads to a drag power loss. Recent studies such as Abdan et al. have proposed more detailed and accurate methods to estimate the oil drag losses in screw compressors. These methods enable the modelling of the effect of even minor changes in rotor profile on the drag loss power. Predictions of this model were hence used to tweak the screw rotor profiles with an objective to reduce the oil drag losses. Such profiles were then retrofitted in the existing machines and tested. Comparing the differences in power consumption of these machines, the component of oil drag loss was deduced. The experimental results show close agreement with the oil drag loss prediction model. The reduction of oil drag losses through profile modifications led to an improvement in the specific power of oil-flooded screw compressor

Oil drag loss in oil-flooded, twin-screw compressors

Rotary twin screw compressors are widely used because of their high efficiency and reliability. Their most common mode of operation is as oil-flooded machines when delivering air and gases at moderate pressures and flow rates. In order to achieve the best performance, it is essential to be able to predict the optimum amount of oil, required for the oil injection process, accurately. Analytical procedures for the design and performance estimation of twin screw compressors are well developed and widely available, but the determination of oil drag losses, in oil-flooded machines is only guesstimated. This paper describes a more detailed and accurate procedure for estimating oil drag loss, using a combined Couette-Poiseuille flow model and gives the results of studies on three sizes of machines operating over a range of pressure ratios and speeds. To this end, a parametric analysis has been developed based on a combined Couette-Poiseuille flow model and has been used to estimate the individual effects of pressure ratio, the various clearances and the oil viscosity on the total drag loss, for different sizes of the compressor. It can be seen from the results that at pressure ratios of up to 8.5, the drag loss due to the discharge axial clearance gap is nearly 2/3rd of the total, while nearly 1/3rd is due to the radial clearance. At normal operating speeds, the loss due to the interlobe clearance is insignificant, but as the pressure ratio increases, this rises more rapidly than that due to the axial and radial losses. The gain in the drag loss due to greater oil viscosity becomes more significant as the compressor size is increased. In larger machines, when clearance values are increased, the radial and axial elements of the drag loss are reduced more rapidly than that due to the interlobe loss

Characterization Study of Empty Fruit Bunch (EFB) Fibers Reinforcement in Poly(Butylene) Succinate (PBS)/Starch/Glycerol Composite Sheet

In this study, a mixture of thermoplastic polybutylene succinate (PBS), tapioca starch, glycerol and empty fruit bunch fiber was prepared by a melt compounding method using an industrial extruder. Generally, insertion of starch/glycerol has provided better strength performance, but worse thermal and water uptake to all specimens. The effect of fiber loading on mechanical, morphological, thermal and physical properties was studied in focus. Low interfacial bonding between fiber and matrix revealed a poor mechanical performance. However, higher fiber loadings have improved the strength values. This is because fibers regulate good load transfer mechanisms, as confirmed from SEM micrographs. Tensile and flexural strengths have increased 6.0% and 12.2%, respectively, for 20 wt% empty fruit bunch (EFB) fiber reinforcements. There was a slightly higher mass loss for early stage thermal decomposition, whereas regardless of EFB contents, insignificant changes on decomposition temperature were recorded. A higher lignin constituent in the composite (for high natural fiber volume) resulted in a higher mass residue, which would turn into char at high temperature. This observation indirectly proves the dimensional integrity of the composite. However, as expected, with higher EFB fiber contents in the composite, higher values in both the moisture uptake and moisture loss analyses were found. The hydroxyl groups in the EFB absorbed water moisture through formation of hydrogen bonding

Effect of fiber content and their hybridization on bending and torsional strength of hybrid epoxy composites reinforced with carbon and sugar palm fibers

This study aims to investigate the effect of fiber hybridization of sugar palm yarn fiber with carbon fiber reinforced epoxy composites. In this work, sugar palm yarn composites were reinforced with epoxy at varying fiber loads of 5, 10, 15, and 20 wt % using the hand lay-up process. The hybrid composites were fabricated from two types of fabric: sugar palm yarn of 250 tex and carbon fiber as the reinforcements, and epoxy resin as the matrix. The ratios of 85: 15 and 80: 20 were selected for the ratio between the matrix and reinforcement in the hybrid composite. The ratios of 50: 50 and 60: 40 were selected for the ratio between sugar palm yarn and carbon fiber. The mechanical properties of the composites were characterized according to the flexural test (ASTM D790) and torsion test (ASTM D5279). It was found that the increasing flexural and torsion properties of the non-hybrid composite at fiber loading of 15 wt % were 7.40% and 75.61%, respectively, compared to other fiber loading composites. For hybrid composites, the experimental results reveal that the highest flexural and torsion properties were achieved at the ratio of 85/15 reinforcement and 60/40 for the fiber ratio of hybrid sugar palm yarn/carbon fiber-reinforced composites. The results from this study suggest that the hybrid composite has a better performance regarding both flexural and torsion properties. The different ratio between matrix and reinforcement has a significant effect on the performance of sugar palm composites. It can be concluded that this type of composite can be utilized for beam, construction applications, and automotive components that demand high flexural strength and high torsional forces