Professional Affiliate of the Engineering Council UK
The Institution of Diesel and Gas Turbine Engineers
Bedford Heights, Manton Lane, Bedford MK41 7PH, England
Tel: 01234 214340 Fax: 01234 355493 Email: enquiries@idgte.org
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The economic viability of various types of prime mover, the performance once installed and
running costs are influenced by numerous factors. This section provides generic information
about plant and equipment that falls under the following headings:
Acoustic Enclosures
Prime movers such as diesel engines, gas engines and gas turbines are much quieter than
they used to be – although not because of any special engine development features;
but because of effective sound-
The enclosure may be a steel ISO container in which the generating set or pump drive may be transported to or from its permanent location, a ‘lining’ of conventional brick/block walls, or comprising of acoustic sections which are assembled around the prime mover.
The enclosure normally houses ancillary equipment save for two specific items; normally the exhaust silencer and water and oil cooling radiators (assuming cooling is provided by this method).
Gas turbines are the normal method of propulsion for aircraft. The link to the aerospace-
Reciprocating engines have less of a tolerance to ingress of abrasive dust than gas turbines, although both need some form of protection. Air filter designs vary according to the amount of airflow, the degree of filtration needed – which relates to the environment in which the prime mover is located. Simple mesh, oil wetted, mesh or cyclone centrifuging action are typical methods used. The design will almost certainly cater for noise attenuation, being noise caused by the filtration process itself or directly from the turbine blades of the gas turbine or reciprocating engine turbocharger. In cooler climates, some environments ‘icing’ of the air filter intake has to be prevented.
How many diesel, gas turbine and steam turbine prime movers are there in the world? It is probably equivalent to several hundred GWe. Such plant is at various stages of its life cycle; ranging from ‘just commissioned’ to ‘reaching the end of its economic life’.
‘End of economic life’ perhaps as standby to a facility now having a reliable grid supply, or operation on liquid fuel because natural gas pipeline has just arrived are only two of numerous reasons why power generating equipment may have become uneconomic in one location, but which makes economic sense if installed elsewhere.
If an organisation wishes to buy or sell such plant, then specialists who hold a
significant and detailed data-
There are distinct advantages of dealing with companies that not only hold data-
A similar situation applies to those requiring valuation of plant for sale, or being considered for sale, in that costs to relocate and the potential of specific plant in its new environment can only be assessed realistically given knowledge of the market.
For more information, visit www.cess.co.uk
CHP (Combined Heat and Power) is defined as the simultaneous generation of heat and power in a single process. When used in an Industrial context this process is often called Cogeneration. The power output is usually electrical power but may include mechanical power. Heat outputs can include steam, hot water or hot air for process heating, district heating, space heating or absorption chilling. The CHP scheme comprises the equipment and operating system including monitoring system and will include one or more prime movers (eg. Gas turbine or Reciprocating Engine) typically driving electrical generators or mechanical loads and some means of recovering the waste heat from the prime mover, which would otherwise be released into the atmosphere.
Tri-
CHP schemes, which may range in power output from a few hundred kilowatts to several hundred megawatts, are assessed by Quality. The Quality of the CHP is determined by the Energy Efficiency and the Environmental Performance of the scheme. In terms of regulatory requirements schemes are also judged on the amount of qualifying heat output (or chilling) provided.
As prime movers develop to become more fuel efficient, more energy is taken from the fuel to provide power for the application; although even at optimum efficiency, a percentage of heat is expelled in the exhaust and is taken away by jacket water and lubricating oil.
If this heat can be utilised as part of the application under combined heat and power arrangements then all to the good. If not, then the heat must be dissipated to either the atmosphere or to a significant water source, such as a river.
Plate or tubular heat exchangers are used to transfer heat from engine oil or water (primary circuit) to secondary water, which may be cooled by the aforementioned river, by dropping the water from a height (cooling tower) or by forcing air past finned tubes which carry the primary fluid (dump radiators).
Each method lends itself to specific applications. Clearly if river water with little sediment is available, then it will be used. Cooling towers are a relatively low cost option, although in high ambient conditions the more expensive radiator option tends to apply.
Concerns over global warming and increasing knowledge of the effects of burning various fuel types has introduced control of exhaust emissions. Improvements are immediately apparent by the absence of ‘smoke’ or visual signs of exhausts from power stations; exhaust smoke which of course must not be confused with water vapour seen rising from cooling towers. These improvements have been brought about by significant reductions of unburnt fuel in the exhaust (CO) owing simply, to improved thermal efficiency. It should however be noted that as efficiency increases and CO reduces, that NOx increases. This is because NOx formation is a function of the high temperature burn, which is associated with better combustion.
How far can one go with engine design and engine tuning? The answer is “a long way” and in particular with high air to fuel ratio gas engines (lean burn) where CO and NOx are both brought down to low levels – beyond this and abatement comes either in the form of treating the fuel (say for acid forming constituents such as sulphur, chlorine and fluorine or by treating exhaust gases, say for NOx, CO.
The balance is usually dictated by cost, versus the emission limits imposed. We currently have wide variations in standards, which tend to be determined by the fuel in use and the country involved. These fuel related categories and associated severity of limits tend to be natural gas, distillate diesel oil, landfill gas, sewage gas or liquid biofuels – and if the fuel is classed as a “waste” or not, whereby very low limits apply, owing to have to meet levels which were previously achieved by high temperature incineration. Under other circumstances, background levels under Pollution Prevention and Control directives dictate the exhaust stack limit.
Turning now to abatement methods:
Fuel Clean-
An often complicated process for clean-
For more information visit www.ccjensen.co.uk
Exhaust Clean-
Processes are well established, in that NOx is treated by injection of ammonia or
eurea, CO and combustible VOCs are dealt with by re-
Exhaust Silencing
Reciprocating engine and turbine prime movers produce exhaust noise, which is emitted at a range of frequencies. Both have in common a higher pitch whine from blades of the GT or the turbocharger of the reciprocating engine.
A tortuous route for exhaust gases passing over absorbent baffles are the primary
method of silencing. Care must be taken however to avoid too high a ‘back-
The exhaust silencer outlet is normally associated with an exhaust pipe, or tailpipe from where gases are released to atmosphere. It is the quantity of exhaust gas per unit of time, combined with the tailpipe diameter, which determines exit velocity – which in turn is associated with tailpipe height and the effectiveness of gas dispersion. It is common practice to have explosion relief doors in silencers, ducts and tailpipes should the exhaust system have sufficient volume to enable ignition of an accumulation of unburnt gases to cause a significant and dangerous explosion.
Reciprocating and gas turbine plant operating on a variety of fuels produce exhaust emissions that are influenced directly by constituents of the fuel and engine design.
Acid forming compounds in the fuel, such as sulphur or chloride can produce sulphuric acid or hydrochloric acid in the exhaust. Oxides of nitrogen are however formed in the combustion chamber and tend to be higher, the higher the peak combustion temperature and the higher peak combustion temperature, the higher thermal efficiency of the engine. Carbon monoxide, on the other hand, tends to increase with lower combustion temperature and the associated lower engine efficiency – all being linked to less complete combustion. CO however, oxidises to CO2 when it has left the exhaust stack and represents a relatively small percentage of the total CO2 from the exhaust.
Particulates follow a similar pattern but tend to be more a visible portion of fuel that either will not burn, or that was not burnt efficiently.
Operating plant at high efficiency for commercial reasons, whilst maintaining an optimum balance on emissions, which are coming increasingly under legislative limits, requires either constant or periodic measurement.
For more information visit www.cplindustries.co.uk
Prime movers burn combustible fluids or gases, which by their very nature will fuel a fire given leakage and an ignition source. The first stage of fire protection is therefore fire prevention and monitoring of the area in the vicinity of the prime mover, for leakage. This may be a fluid level switch in a sump, to where liquids would drain or transducers sensitive to methane for gaseous fuels. The next step would be detection of fire by heat or smoke transducer. Given detection of fire, it is usual to stop the prime mover and to safely cut off the fuel supply. This is often the only form of protection as the enclosure may have a 1 hour or longer fire rating. Some applications, release of CO2 or water mist to extinguish.
“Foundations” in this industry tend to be mechanical interfaces between machinery and a stable structure below. They serve to equally distribute the load of the plant item and given adequate mass, are often used to also absorb vibration.
Correct design and selection of materials is clearly a pre-
Simple aggregates in a cement mix may have been acceptable for industrial applications or accurately machined steel blocks for marine or rail traction, some years ago, but the ever increasing need for cost effectiveness has brought development both in structural design and materials, which ensure longevity of the foundation itself.
Development has lead to materials that are easy to pour or inject, have resistance to corrosion, erosion abrasion, cracking or simply resistance to degradation by lubricating oil. Such development has also made long lasting repairs, which would not have been attempted years ago, cost effective.
Liquid and gaseous fuels normally contain contaminants as a result of the production process, transportation, or storage. Fuel filters normally deal with solids, as water is usually drained after settling, centrifuged away or following a condensing process.
Fuel filters are manufactured from mesh, paper or fabric, depending on the nature
of the fuel and the degree of filtration needed. The internal part of the filter
is known as the element and is normally ‘disposable’ rather than being suitable for
washing and re-
The Institution is devoted to advancement of knowledge of reciprocating engines and gas turbines, both of which are more suited to specific applications, when account is taken of specific attributes.
The industrial gas turbine burns gaseous or liquid fuels, in a combustion chamber located after a rotary compressor and immediately before a rotary turbine, which is driven by the energy released by the expanding gases of combustion. These gases may pass through three such turbine sections before being exhausted to atmosphere.
This arrangement permits high rotational speeds and hence a high fuel (and air) throughput. The end result is a higher power density from a relatively small item of machinery.
Very small gas turbines, known as micro-
Lubricating oil is used to separate surfaces moving relative to each other, with an “oil film” and in the case of reciprocating engines, gas turbines and associated plant, to take away heat.
How much separation? How much heat? In fact these are only two of a very significant number of requirements that lubricating oil must be designed to address for defined applications.
Modern lubricating oils are designed to resist, for example, acids using additives
-
Combustion deposits entering the oil from the combustion chamber are removed in the
filter system; a process which is made so much easier if carbon or soot can be kept
in suspension and enable deposition in the filters, thus preventing sludge formation.
Additives are therefore used to promote “dispersancy” which may be witnessed by a
“clean” appearance within the crank-
High speed turbo-
Lubricating oil, by the very nature of its activities, passes around all moving parts and given a few hours in service, carries a “history” of engine characteristics. These characteristics can be detected by routine, used oil analysis. Condition monitoring is a powerful management tool, which when combined with other monitoring techniques enables plant to be stopped for overhaul when overhaul is actually due, rather than arrangements where plant was taken out of service following a given number of hours, based on the makers recommendation of “average” experience worldwide.
For more information visit www.castrol.com
Monitoring & Control -
Monitoring of diesel and gas engines, with a view to taking early action that prevents expensive and often catastrophic failure, takes different forms. High lubricating oil temperature and low lubricating oil pressure alarms with shutdowns tend to come as standard engine features; although seldom do these monitored parameters fall outside of acceptable limits, which can vary over the load range, in time to prevent serious damage.
Oil mist in the engine crankcase does however change its composition in the vicinity of a component running at high temperature and if this change can be detected quickly, then the engine can be stopped in a matter of seconds.
The systems used historically sampled several crankcase areas via lengthy pipework, and whilst effective on the slower speed engines, the time delay for the mist to reach the sensor on higher speed sets has been far too long for real effectiveness.
Modern electronics that includes the ability to place sensors at several locations
– indeed on every crankcase bay if required has made oil mist monitoring a very cost-
How does it work?
An inherent layer of oil mist can be found in all engine crank-
Oil mist is generated to a far greater extent however, from surfaces which are excessively hot and such changes can be readily detected by modern electronic equipment. The electronics, combined with expert programming, are adequately sensitive to detect particulate sizes and concentrations and to alarm and shutdown plant as required.
For more information, visit www.oilmist.com
Museums that renovate and exhibit diesel and gas engines and gas turbines form a
sector of industry that receives support from the IDGTE. Exhibits, in static or operational
form, play a key role in retaining our industrial heritage and as such, engine museums
welcome assistance with location of prime movers and associated memorabilia, technical
information, organised visits and introductions to like-
For further information:
Anson Engine Museum www.enginemuseum.org
Internal Fire Museum www.internalfire.com
The sea is a a particularly hostile environment for any Power Generation Equipment.
Not only is it necessary to cope with extremes of temperature, the ravages of driving rain and a salt laden atmosphere, it is also essential for generating plant to operate reliably and safely in this environment for long periods and without intervention. “Long periods” are actually enforced by weather conditions, which make access difficult and the tendency for installations to be unmanned.
Reliability can only be achieved by the selection of the highest quality components and attention to specialist design, which takes into account these fundamental requirements as well as manning levels, high loading, light load running, to mention but a few.
Such design features include stainless steel enclosures with IP56 protection, special filtration for fuel and oil, extended lube oil capacity, multiple starting systems, vibration isolation, inbuilt fire protection systems and remote control interfaces.
Speed and efficiency of maintenance is a further factor -
There are clearly very significant differences in “offshore” compared to conventional
plant as can be seen from the above brief descriptions. Specialist experience and
track-
Provision of Goods and Services
The Institution runs a “Members Directory” to advertise those wishing to provide goods or services to others.
The previous section listing Consulting Engineers is included.
Capital investment for new generating plant is normally cost effective owing to modern developments – fewer components, better fuel consumption, lower exhaust emissions and amortisation over 15 to 20 years.
Part way through this period however, specialist overhaul, refurbishment and updating
can be undertaken by organisations specialising in specific prime mover types and
having “re-
Important aspects are that legal rights of an original maker should be complied with by the supplier, the components or services provided should provide adequate longevity for the subject plant and sufficient knowledge should be available from the supplier to ensure that goods for sale are to the correct specification.
Most companies in the reconditioning business run approved quality control schemes and can provide references from plant operators. Independent inspection, which tends to only visual, and hence restricted, is another alternative.
One of the earliest prime movers for industrial, marine, automotive and rail traction was the reciprocating engine – principally a piston driven down a cylinder by steam or expanding gases after combustion and acting on a rotating crankshaft via a connecting rod.
This engine type has worked through numerous phases from the days of steam and currently provides power at between 35% to 45% thermal efficiency when combusting a range of gaseous fuels and liquid fuels.
Smaller, high speed engines (more than 1,500 rpm) tend to be mass produced and are used to drive a wide range of machinery, as well as being popular for generation of electricity, should grid supplies fail.
Low and medium speed engines (1,500 rpm and below) in fewer (but significant) numbers drive heavy duty industrial, marine and rail traction machinery.
Filters which are fitted in liquid fuel supply lines would soon become blocked if the majority of contaminants were not first removed.
Use of centrifugal force to transport heavier portions of the fuel into a specific area, where they can be collected, has become a very efficient method of removing solids.
The principal is that of passing the fluid into a ‘drum’ which is rotating at high(separation) speeds. Heating the fluid normally assists. Repeating the process after separation to further reduce contaminants is known as “clarifying.”
The foregoing process is used for fuels -
For further information go to www.wsgb.co.uk
Generation of electricity, and especially high voltage electricity introduces the need to connect and disconnect the generating set to the supply lines via heavy duty switches (switchgear), and for automatic systems to keep the switchgear safe in that both machinery and personnel may be protected.
These arrangements involve monitoring voltage, current and frequency, with action taken following input by operators or when defined danger levels are reached.
Installation, commissioning and routine monitoring of machinery, associated with prime movers, requires measuring equipment having adequate accuracy and repeatability of results. Test certificates that support calibration checks are normally provided for this purpose. The range of parameters to be measured is wide ranging – for example: pressure, flow, voltage, current, frequency, vibration, concentration of chemicals, intensity of light, etc.
It is usually cost effective to purchase and own instruments for regular measurement of the same parameters, although comparison of the instrument to a known standard and associated certification from an independent body is still a requirement.
An alternative is to hire certified instrumentation for the occasions when measurements are required.
Disclaimer
The Institution provides the foregoing information in the spirit of its objectives and cannot accept responsibility in any form for loss, or consequence of loss, incurred resulting from use of the said information – which in any event should be verified by specialists in the subject.
