Gas engines used in on-site power applications are subject to a host of demanding requirements, both from an environmental perspective and an economic one. Greater automation and better control play a fundamental role in achieving these objectives, finds David Appleyard
Precise control is vital
Induction, compression, ignition, exhaust – it’s an old story now, with well over a century elapsing since that mantra first took solid form in metal. Today, while those same principles still apply, gas engine technology is a world away from its ancestors.
Over the years higher compression ratios, fuel injection, turbo chargers and numerous other mechanical advances have pushed engine technology forwards – but in some respects engines are reaching their limits. The opportunities for further mechanical innovation in reciprocating engines achieving dramatic gains in efficiency or emissions are considered ever more challenging.
Efficiencies are now pushing beyond 50% in simple cycle – gas engines are beyond 90% efficiency in combined heat and power mode – and in current applications engines are increasingly faced with demanding stop-start duty cycles and stringent emissions limits.
They achieve these remarkable performances through precise control of the combustion process in every one of perhaps 24 cylinders. Now and for the foreseeable future, a key battleground for engines will be optimization of the combustion process.
As the limits of IC engine technology draw closer, holding the engine in the narrow ‘golden window’ of operations – and avoiding any ill-timed detonations that may destroy it – is becoming more challenging.
Precise control of fuel and fuel-air ratios as well as pin-point ignition timing is vital. What’s more, changing atmospheric conditions can wreak havoc with combustion.
‘There is a small window, the more you push an engine’s efficiency, the more you push an engine’s power, the lower you try to get emissions, the closer you are to running the engine to its limits. And the negative of all these is a misfire or detonation that occurs inside the engine,’ explains David Joyce, Senior Applications Engineer for the gas engine business of Dresser-Rand, part of Siemens Power and Gas.
Changes in temperature, pressure and humidity all have a significant impact on combustion characteristics, in particular having a major effect on emissions of nitrogen oxides – a pollutant facing increasingly stringent regulatory restrictions.
Today, at the heart of precise combustion control is the ECU, and within it the engine mapping software that enables optimum combustion control under varying operational modes and ambient conditions.
Guenther Glas, Head of System Automation for the engine business of MAN Diesel & Turbo, explains: ‘The system adapts to the ambient humidity, which has the biggest impact on the oxides of nitrogen produced by the engine. This is one emission which is regulated by the authorities.’
New ECUs with more power, many more sensors and the application of big data analytics are advancing engine technology beyond all recognition.
As Joyce says: ‘What has changed over the last few years is the engines now have ECUs. They have their own little computers to control pretty much every aspect of the engine. Ignition systems are now an awful lot more sophisticated. They can control the spark in every cylinder, they control the energy to every spark. Carburation systems are a lot more finite in their control. So they control the amount of fuel that’s going into the engine at every instant to make sure that we meet the efficiencies that people are looking for and keep the emissions as low as we can.’
He adds: ‘That’s where the automation and control has played a big part over the last few years. People are demanding high efficiencies and the only way to do that is to have a very good control of the combustion process.’
This view is echoed by Niklas Doktar, Head of Electrical & Automation development at Wärtsilä Energy Solutions: ‘It is technology, what has enabled this change is that you have better processing power and also communication possibilities available. In the past you didn’t have enough processing power or memory to do all this computational work that’s needed. These processors and memories are now becoming available and can be utilized for industrial applications and engine controls. It’s a market enabler that’s helped us. We now have better communication networks which enable large data transfer within the engine or with other engines.’
Doktar continues: ‘We are able to run the engine a lot closer to its limits by knowing exactly where we have the limits and where we are running at the moment. That’s all down to having a lot more accurate measurements and having the processing power to analyze the measurements to see where we’re going at the moment.’
As Joyce notes: ‘There are sensors that monitor the fuel coming into the engine, pressure flow, there are sensors on the engine to monitor the actual operation of the engine and the conditions that it’s in, the temperature that it’s running at. And then a lot of what’s happening now is that people are monitoring the outputs of the engine – not just the power but the emissions. You are monitoring the exhaust and then you are adapting the engine to make sure that you’re always maintaining a set emissions requirement. That’s one of the key drivers that’s pushing the electronics.’
Glas highlights the very real impact of advanced controls on engine performance: ‘Obviously there are no more engines on the market without electronics, and the functions are increasing dramatically. We have achieved efficiency above 50%. This would not be possible without the high level of engine control. With the help of the controller we can react to changing ambient conditions and changing fuel quality, for example, and this is needed to get the last few numbers to increase the efficiency. That’s where we need advanced controls.’
|Systems adapt to ambient humidity Credit: Siemens|
Scott Parent, Senior General Manager, Technology & Operations with GE’s Distributed Power business, also emphasizes the role of advanced controls on emissions during particularly challenging quick startup phases: ‘If we didn’t have a way to control inputs, pressures, exit temperatures the way we do today with an advanced control system, you couldn’t achieve those without it.’
Doktar also highlights the role of advanced controls in delivering flexible operational characteristics: ‘We can reduce our startup times, so at the moment, from the push of the start button we can guarantee full output in two minutes, thanks to advanced automation and controls, fast startups, faster ramps, faster load responses and also faster shutdowns on the engines to cope with the variations of demands, that’s one area that has developed a lot in the last years.’
Integrated control of engines and systems
With emissions limits on an ever-downward trajectory, even with precise combustion control, engines are likely to require additional post-combustion exhaust treatment, such as Selective Catalytic Reduction (SCR), in the future. This will inevitably require additional functionality within the controls system.
Joyce: ‘There is a lot of development now on the after-treatment that you would have to apply if the emission limits started to come down even lower than they are now. So then there will be tie-in between the controls that you have on those systems with the engine.’
Doktar concurs, noting: ‘A good example of system integration in that case will be the engine itself, but also after the systems afterwards. This will be more and more important in the future. One of our benefits is that, for example, at the moment the engine and the SCR or after-treatment system run on a single automation platform together. System integration is one of our big strengths.
‘It’s an important area, having the after-treatment equipment communicating with the engine and the rest of the process in order to optimize it and get the most out of it. Not just having individual components, but also look at the whole chain.’
This is echoed by Parent, who says: ‘Today we’re being much more prescriptive, everything from the lubricants to the filters we use. To obtain higher levels of performance all of these system ancillaries have to be brought into the analysis and simulation and all need to be monitored. Really you have this entire system – including the engine – that enables you to get higher performance.’
Parent also points to the application of greater systems control in the entire lifespan of the engines, right from manufacture. ‘Advanced controls and automation across the space would include not only the products that are commercialized, but the means to produce those products in a ‘Brilliant’ factory.’
Modelling, diagnostics, control and analytics are key to developing such engineering and Parent emphasizes the potential benefits: ‘We’re now able to manufacture much more accurately and repeatedly using automated manufacturing techniques. In GE’s factory we will be able to produce product with less variation. Then when that product is in the lifecycle at a plant anywhere in the world, we can control its operation, keep it tuned up and maintain its lifecycle uniquely based on the data we collected on that particular product in the plant whilst it was being manufactured.
‘Maintaining them more remotely can cost less money, you can do it more quickly and it will help eliminate unplanned down time. The industrial internet is allowing GE to standardize our own factories and products around our Predix platform, and that’s going to allow us to work faster at lower cost and with increased reliability.’
|In the future, power plants could be operated remotely Credit: Wärtsilä|
The potential power of data analytics is also opening the door to those with experience in the data industry, rather than the power industry. As Doktar observes: ‘If you’re looking at [Wärtsilä’s digital platform] Genius and the digital space that is the future for us, we are investing a lot in that. But there are also others, big players like IBM, Google, it’s interesting to see.
‘They are looking at the service model, they have the platform for big data. The analytics is the key.’
Parent also notes the potential to improve customer experience through additional services enabled through advanced controls and automation: ‘I think we’re going to see a lot more of that. Many of our customers aren’t in the business of managing power. I think the opportunity here is to provide enough information locally so that folks can run their own business.’
Digital technology enabling automation
The sheer volume of data now being collected is necessitating a sophisticated approach to its management and analysis, as Parent notes: ‘We had probably 500 million sensors in the industrial space on the internet 10 years ago, we expect that number will be greater than 20 billion by 2020 and will increase another two-fold in the next decade.’
This data, and fundamentally its analysis, is enabling greater automation opportunities, even completely unmanned operations, as Glas observes: ‘I think we are ready to offer basic functionalities and interfaces for future oriented [remotely operated] power plants. That’s the near future, I would say.’
But Glas also warns of the potential vulnerability of such systems in the face of cyber-attack. ‘I see these [security] standards will come more and more and will be one of the top priorities. We have to meet these standards as a minimum, as well as all suppliers and partners.’
Looking ahead, Joyce says: ‘I’m really confident that automation and control is now playing a big part in the systems that are going to installed, the integration of generators with wind turbines, with solar, the schemes that people are putting together are all communications areas.’
Many future breakthroughs in engine development are expected to come from opportunities in the automation and control sphere. Remote operations and unmanned power stations, diagnostics and analysis, all the technologies required to potentially enable this additional functionality currently exist and are growing more sophisticated by the day.
As Glas says: ‘In the future we need to think more about fail-safe remote control, complex interactions with suppliers, and also maybe unmanned power plant operations, step-by-step.
‘It is the combination of intelligent functions concerning highly-skilled system integration competence, it is health and safety and cyber security, it is all the communication data and self-learning, it is about energy efficiency and fuel flexibility as well as operational lifecycle costs.’
But, as the wealth of operational data expands, from manufacture through ongoing service, and as increasingly adept analysis and diagnostics is established – given that many of even the current generation of gas engines come with an abundance of sensors, a wealth of data and a lifespan of decades – the emergence of advanced controls and automation opens the door to an intriguing prospect. By the simple expedient of uploading a more sophisticated and appropriate engine management system, a gas engine may yet emerge which becomes more efficient and more economical to run as it ages.
David Appleyard is a freelance journalist focusing on the energy sector.