Working Knowledge of the Compressor Systems Aerodynamics - Essay Example

Compressors Student Name: Faculty: Student ID: Course name: Course Number: Date of Submission: Table of Contents Table of Contents 2 Abstract 4 Introduction 4 Positive displacement compressors 5 Centrifugal compressors 5 Inlet 6 Centrifugal impeller 6 Diffusers 6 Collector 6 Applications 6 Advantages 6 Disadvantages 7 Axial Flow compressor 7 Operations 7 Applications 7 Advantages 8 Disadvantages 8 Reciprocating compressor 8 Applications 9 Materials used 9 Advantages 9 Disadvantages 9 Rotary type compressors 9 Slide vane 10 Rotary Lobe 10 Liquid seal compressors 10 Materials used 11 Advantages 11 Disadvantages 11 Applications 11 References 12 Abstract Compressors industry has recently emerged from the era of the 80’s when rightsizing, streamlining, and computerization were the order of the day. Today modern management trends incline towards broadening of work responsibility across all departments, and in order for organizations to satisfy these very responsibilities, the company’s maintenance, operations, and engineering personnel require continuous and consistent review of various compressor types, classifications, and applications. Enterprises across the globe are today recognizing the void that has been caused by talent shortage due to rightsizing and these very company have made efforts to retain core group of experienced experts who can be consulted whenever need arises. These retained experts are expected to present various compressor concepts to all interested parties within the organization. This particular pool of talented compressor experts also requires certain working knowledge of the compressor systems aerodynamics, advanced thermodynamics concepts, magnetic bearing theory, and blade design and repair. Introduction An air compressor can be described as a system that takes in air and compresses it hence making the pressure inside the tank to be high compared to the air pressure outside the tank. Compressors often release pressurized oxygen that can be industrially applied. Compressors are widely used in industries as well as domestically in homes. Due to this they have managed to find various applications at both the enterprise and domestic level. Air compressors can be used for quick inflation purposes because they release pressurized air. Such products come with built in mechanical capabilities that can be used to inflate various objects such as kayaks, inflatable canoes, rafts, and tubes inside tires. Compressors are also widely used in the auto industry whereby they are used in hydraulic jacks for vehicles. Other products that can be found inside auto service stations that use air compression includes wrenches, grinders, and drills (Philip, Derrick, Scott, 2008). One of the primary benefits that these air tools provide is that they facilitate the sharing of centralized power (compressor) hence often cost less compared to various standalone electric tools. For instance, it is possible to acquire an air powered nail gun for as little as 100 bucks whereas a similar standalone product powered by gas cartridges is likely to cost approximately 250 bucks. Also by embracing unified power source concept systems reliability is enhanced because of the single centralized motor that is likely to fail rather than having one motor inside each tool. There is also the benefit of enhanced power output. For instance, it is possible for a pneumatic wrench to loosen lug nuts that have clogged up as a result of rust build-up, while the lug rench inside the vehicle will definitely find it very difficult to break down the rust. Compressor also brings in the benefits of their modular nature and this implies that if an air compressor is upgraded, nearly all the tools are likely to benefit from enhanced speed, torque output or runtime. Traditionally upgrading power tools without necessarily having a compressor would mean that each tool had to be replaced as a single entity. There are various types of compressor types and these include positive displacement and centrifugal compressor type. Positive displacement compressors These types of compressors mainly embrace positive displacement technology that causes movement by trapping some fixed amount of air then forcing the trapped amount of air through a discharge pipe. In this type of machine certain inlet volume of gas is confined in a given space and subsequently compressed by reducing this confined space or volume. At this particular elevated pressure, gas is expelled into the discharge piping or vessel system (Bloch, 2006). Centrifugal compressors This type of compressor uses high speed spinning impellers that may rotate on speeds of up to 60,000 rpm to accelerate the air then the diffuser decelerates the air through a process that is referred to as dynamic compression. Such types of machines come with intercoolers between each stage in order to cool the air and also to remove 100% of the condensate to avoid impeller damage that arises as a result of erosion (Boyce, 2003). Fig 1.0 diagram depicting the anatomy of a compressor system A centrifugal compressors come built with four main components namely the collector, diffuser, impeller/rotor, and the inlet. Inlet It comprises of a simple pipe that may come with various features such as stationary vanes, valves, and pressure and temperature insulations. Centrifugal impeller It is a key component inside centrifugal compressor. The impeller comes with rotating set of vanes that raises the energy of the working gas. It functions similar to an axial compressor and the only notable difference is that gases can achieve higher velocities and energy levels courtesy of the impellers increasing radius. In modern high end compressors the gas exiting impeller normally travels at the speed of sound. Diffusers It is mainly responsible for converting the gas kinetic energy into pressure by gradually slowing the gases velocity. They come either as vaned, vaneless or in an alternating fashion. Collector It is where the diffusers discharges and this very collector may assume various shapes forms such as volute or plenum. The collector basically gathers flows from the diffuser annulus and delivers this very flow into the downstream pipe. Applications This particular compressor type is used in various areas such as gas turbines and auxiliary power units, in oil fields, air separation plants for manufacturing purified end product gases, in air conditioning and refrigeration, in chemical plants, petrochemicals, natural gas processing, and pipeline compressors of natural gas (2000). Materials used Some of the materials used in a centrifugal compressor are steel. Advantages It is ideal for producing compressed air supply It is able to deliver high power output (up to 500hp) and high pressure output (up to 85 bar) Output is oil free Disadvantages Very expensive to deploy Due to its high speed quality bearings and sophisticated maintenance are always required Axial Flow compressor This is basically a rotating airflow based compressor system whereby the working fluid principally flows parallel to the axis of rotation. This particular compressor system delivers continuous flow of compressed gases and they also provide the benefits of high efficiencies and large mass flow capacity particularly in relation to their cross section. Operations This specific compressor system comprises of both rotating and stationary parts. There is s shaft that drives a central drum that is retained by bearings that consists of a number of annular airflows rows attached. These rotate between some similar numbers of stationary airflows rows that have been attached to a stationary tubular casing. The rows alternate between the rotors and the stators, whereby the rotors impart energy into the fluid inside the compressors, and the stators on the other hand play the role of converting rotational kinetic energy into static pressure through the diffusion process (Ronald, 2003). Fig 2.0 diagram depicting internal structure of an axial flow compressor system Applications These are widely used in small scale power stations, high speed ship engines, and gas turbines such as jet engines. They are also used in various industrial applications such as propane dehydrogenation, fluid catalytic cracking air, blast furnace air, and large volume air separation plants. Advantages There is increased pressure rise due to the increased stages with negligible energy losses There is high ram efficiency arising courtesy of straight through flow Small frontal area forgiven airflow High peak efficiency Disadvantages The efficiency is exceptional due to its narrow rotational speed range Difficulty to manufacture that as a results makes the product expensive Axial flow compressors are very heavy It requires high starting power requirements Reciprocating compressor This is a positive displacement compressor that engages pistons that are powered using crankshafts to deliver gases at extreme pressures. It is regarded as a positive displacement machine that compresses air via pistons driven back and forth by a crankshaft attached to the compressors motors (Albert, 2001, 297). The intake gas normally gets in through the suction manifold before it flows down through the compression cylinder where it is compressed using a piston operating in a reciprocating motion via a crankshaft and then discharged. Fig 3.0 diagram depicting internal structure of a reciprocating compressor Applications Used in blowing plastic bottles that are made using polyethylene terephtalate. It is also used in refrigeration plants, natural gas processing plant, chemical plants, gas pipeline, high pressure applications such as air ballast, starting the IC engine, and also used in oil refineries. Materials used Some of the materials used in a reciprocating compressor include Head-here we used forged carbon steel Piston- Forged aluminium alloy with Teflon/carbon piston rings Cranked shaft- Alloy steel or forged carbon Disc valves – stainless steel Advantages Initial capital outlay required to install it is less Oil carryover problem is not there It always runs efficiently whether is used continuously in a large factory settings or intermittently Reciprocating compressor technology is mainly used to develop silent air compressors used in homes and offices. These compressors work in a quiet manner and seldom use a lot of oil. Disadvantages They require large capital outlay They require consistent periodic maintenance that offsets the benefits of using the machine They require large tanks in order to establish a proper reservoir of compressed air Has very many moving parts that causes vibrations Rotary type compressors This is a version of a gas compressor that engages rotary type positive displacement mechanism. These machines are designed in a compact and lightweight manner. These compressors operate by using two meshing helical screws referred to as rotors in order to compress the gas. Inside dry running rotary compressor the timing gears ensure that both male and female rotors maintain precise alignment throughout the products operations, but on the other hand in an oil flooded rotary screw version the lubricating oil comes in between the space of rotors hence delivering hydraulic seal while transferring mechanical energy between the driving and driven rotor (Theodore, 2001, p.7; Bloch, 1998, p.595). Fig 4.0 Diagram of a rotary screw compressor The basic principle with rotary screw is that gas enters via sunction side and moves through the threads when the screws rotate. Meshing rotors will then force gas through the compressors whereby the gas will exit the compressor at the end of the screws (Keith, 2011, p.263). The effectiveness of this particular principle is largely dependent on precise fitting clearances between eh helical rotors and chamber size for sealing compression cavities. There are various types of rotary compressors and this includes slide vane, rotary lobe, and liquid seal compressors. Slide vane It is mainly used in non-industrial sectors and this particular machine works by allowing air to enter into the vane compartments in a pressurized manner hence driving the mechanism into rotary movement. As a result, the vane shaft turns and the individual vanes slide in or out. Rotary Lobe This particular version combines two separate lobe design rotors within a single encasement. The design of these compressors comprises of non contact rotors that minimizes on cavity size created by lobes as they rotate. Liquid seal compressors It works by dispersing fluids from inclined and open impeller. When the impeller begins to rotate there are some centrifugal forces that cause the liquid to gather at the outer edge of the cavity and form air tight seals. Materials used It is normally made of the end covers of high quality cast irons mainly due to superb bearing quality materials of free carbon, hard iron carbides and porous surfaces that retains oil. According to rotary screws come with several advantages that can be summarized as Advantages When powered using a variable speed it is able to provide the lowest operating energy cost without any appreciable reduction in service life It comes with lower leakage levels and parasitic loses It is more suitable to be used in dirty environments Disadvantages Rotary are not suitable for high pressure applications Oil carryover problem is not present Applications They can be used in laboratories, pneumatics, and robotics They can be used in dirty environment They are also suitable for low pressure applications References Albert Thumann, D. Paul Mehta (2001). Handbook of energy Engineering, 5th Edition. Taylor & Francis. Theodore Gresh (2001). Compressor performances: Aerodynamics for the user 2nd Edition, Newness Publishers. Phillip Dowson, Derrick Bauer, Scot Laney (2008). Selection of Materials and Material related processes for centrifugal compressors and steam turbines in the oil and petrochemical industry. Retrieved from http://turbolab.tamu.edu/proc/turboproc/T37/T37-TUT05.pdf Bloch (2006). A Practical Guide to Compressor Technology: Volume 2 of standard methods for analysis and testing of petroleum and related products, 2nd edition, John Wiley & Sons. M. P. Boyce (2003). Centrifugal Compressors: A Basic guide, illustrated edition, Pen well Books. Ronald H. Aungier (2000). Centrifugal compressors: A Strategy for aerodynamic design and analysis. Illustrated edition, ASME Press, University of Michigan. Ronald H. Aungier (2003). Axial-flow compressors: a strategy for aerodynamic design and analysis, illustrated edition, ASME Press, University of Michigan. R. Keith Mobley (20110. Maintenance fundamentals; Plant Engineering, 2nd Edition revised, Butterworth-Heinemann Publishers. Heinz P. Bloch (1998). Process Plant Machinery, 2nd Edition Illustrated, Elsevier Publishers. Y. P. Abbi, Shashank Jain (2006). Handbook on energy Audit, Illustrated edition, TERI publishers. Read More

There are various types of compressor types and these include positive displacement and centrifugal compressor type. Positive displacement compressors These types of compressors mainly embrace positive displacement technology that causes movement by trapping some fixed amount of air then forcing the trapped amount of air through a discharge pipe. In this type of machine certain inlet volume of gas is confined in a given space and subsequently compressed by reducing this confined space or volume.

At this particular elevated pressure, gas is expelled into the discharge piping or vessel system (Bloch, 2006). Centrifugal compressors This type of compressor uses high speed spinning impellers that may rotate on speeds of up to 60,000 rpm to accelerate the air then the diffuser decelerates the air through a process that is referred to as dynamic compression. Such types of machines come with intercoolers between each stage in order to cool the air and also to remove 100% of the condensate to avoid impeller damage that arises as a result of erosion (Boyce, 2003). Fig 1.0 diagram depicting the anatomy of a compressor system A centrifugal compressors come built with four main components namely the collector, diffuser, impeller/rotor, and the inlet.

Inlet It comprises of a simple pipe that may come with various features such as stationary vanes, valves, and pressure and temperature insulations. Centrifugal impeller It is a key component inside centrifugal compressor. The impeller comes with rotating set of vanes that raises the energy of the working gas. It functions similar to an axial compressor and the only notable difference is that gases can achieve higher velocities and energy levels courtesy of the impellers increasing radius.

In modern high end compressors the gas exiting impeller normally travels at the speed of sound. Diffusers It is mainly responsible for converting the gas kinetic energy into pressure by gradually slowing the gases velocity. They come either as vaned, vaneless or in an alternating fashion. Collector It is where the diffusers discharges and this very collector may assume various shapes forms such as volute or plenum. The collector basically gathers flows from the diffuser annulus and delivers this very flow into the downstream pipe.

Applications This particular compressor type is used in various areas such as gas turbines and auxiliary power units, in oil fields, air separation plants for manufacturing purified end product gases, in air conditioning and refrigeration, in chemical plants, petrochemicals, natural gas processing, and pipeline compressors of natural gas (2000). Materials used Some of the materials used in a centrifugal compressor are steel. Advantages It is ideal for producing compressed air supply It is able to deliver high power output (up to 500hp) and high pressure output (up to 85 bar) Output is oil free Disadvantages Very expensive to deploy Due to its high speed quality bearings and sophisticated maintenance are always required Axial Flow compressor This is basically a rotating airflow based compressor system whereby the working fluid principally flows parallel to the axis of rotation.

This particular compressor system delivers continuous flow of compressed gases and they also provide the benefits of high efficiencies and large mass flow capacity particularly in relation to their cross section. Operations This specific compressor system comprises of both rotating and stationary parts. There is s shaft that drives a central drum that is retained by bearings that consists of a number of annular airflows rows attached. These rotate between some similar numbers of stationary airflows rows that have been attached to a stationary tubular casing.

The rows alternate between the rotors and the stators, whereby the rotors impart energy into the fluid inside the compressors, and the stators on the other hand play the role of converting rotational kinetic energy into static pressure through the diffusion process (Ronald, 2003). Fig 2.

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