How lubricants are enabling gas engine operators to upgrade their performance
08 June 2021
By Zoe Fard, R&D product specialist at HollyFrontier Lubricants & Specialties, which includes the Petro-Canada Lubricants brand
Marginal gains in gas engine performance can equate to significant savings in downtime, manpower and for the bottom line. In an industry that is constantly experiencing a financial squeeze, those margins are being strived for by operators and Original Equipment Manufacturers (OEMs), who gain from greater efficiencies.
The OEMs are at the forefront of improving performance, driven by three main factors. First, they are all seeking competitive advantage in a crowded global field. Gas engine manufacturers in power generation applications have created a highly competitive environment to advance their engines and achieve higher efficiencies and power. Second, changing emission regulations. OEMs are looking to the strictest emerging regulations when designing their engines and as a result, the environment becomes increasingly competitive. And third, unconventional sources of gas are being developed quickly in many markets. From biogas, to landfill gas and coal gas, OEMs need to adapt their engines to run on different fuel types, which constitute varying amounts of methane, again, to stay ahead of the competition and meet increasingly strict regulations.
One of the outcomes of this evolution of modern gas engine technology is increased stress on the engine oil. Before advancing technologies are taken into account, the lubricant of a gas engine already needs to provide a number of functions that only complex formulations can achieve. It needs to be able to neutralize acids, resist oxidation and nitration based on combustion type, maintain OEM’s required sulfated ash content and be compatible with the catalyst in addition to working for extended periods. The effectiveness of the oil will be influenced by a variety of stresses, which is why ongoing monitoring of the oil quality, adequate maintenance and timely replacement (if needed) are imperative. The selection of the type and grade of lubricant should be based on the engine operating conditions, OEM recommendations, condition of the gas and the environment in which the engine is to operate.
However, during the past decade, gas engine oil developments have become more dynamic to adapt with the latest engine advancements. Incremental improvements made to the engine technology are driving lubricant companies to invest their own research and development. At HollyFrontier Lubricants & Specialties, we work closely with gas engine OEMs to anticipate the demands of next generation engines so that we can develop new solutions. This is a positive drive for the industry as a whole; advancement is cyclical – while the machines improve, the oils step up and operators achieve an overall upgrade on their performance.
Oils catch up - what do modern engines require?
Higher mechanical efficiency and power output in high performance modern engines is achieved by increasing the boost pressure of the engine and seeking higher compression ratios through engine design changes. Recent examples of design changes are the switch to steel pistons from traditional aluminum pistons and shorter piston top land. These highly efficient engines are operating at higher brake mean effective pressure (BMEP). The increased pressure means higher temperatures which new engine designs are built to accommodate. But it means the oil must also be able to handle sustained higher temperatures and harsher environments.
The advantage of steel pistons is better component strength, but thermal conductivity in steel is not as good as in aluminum. The oil is consequently exposed to higher temperatures for longer periods of time. In new piston designs, piston ring packs are located closer to the top of the piston where fuel burns. All of this puts additional stress on the lubricant, risking higher rates of oxidation and nitration, Base Number (BN) depletion, together with an increase in Acid Number (AN) and viscosity. This can result in shorter oil drain intervals as condemning limits are reached faster. In addition, accelerated oil degradation can result in increased ring groove and land deposits and piston undercrown varnish that can lead to efficiency loss and engine reliability issues. This supports the need for developing even more advanced, high-performance gas engine oils. Operators who have invested in advanced engine technology expect to avoid maintenance and unplanned downtime where possible. Therefore, selecting the right lubricant and avoiding a shortening of its life, is crucial. If oil changes must become more regular, any efficiencies gained from the improved engine technology could be cancelled out.
Another trend is to reduce oil consumption and emissions. The oil consumption rates have dropped considerably in the past decade. This reduction in oil consumption is the result of modified piston ring designs, oil spinners and updated valve stem sealing. Another design change is reduced clearance between piston crown land and cylinder liner for reduced emissions. These design changes improve combustion efficiency and reduce lube impacts on emissions but also results in higher level of stress to the lubricant, accelerating its degradation.
When considering the increased usage of alternative fuels, further development of the lubricant is demanded. Biogases or landfill, sewage and wood gasses have multiple impurities including high sulfur, halogens and siloxanes that must be addressed by providing better acid control and deposit prevention properties in the oil formulation.
Lubricant companies respond
Lubricant companies are striving to anticipate what OEMs are going to need for their evolving engines. Formulations are being developed with greater thermal and oxidative stability, neutralization ability, and high temperature deposit control tendency through advanced detergency and dispersancy. Modern engine technology is also pushing lubricant development to improve operation at reduced oil consumption rates and as mentioned, better performance with emerging raw fuels.
Companies are also forming technology partnerships to jointly recognize the adaption of new engine technology and its impact on the wider industry. HollyFrontier Lubricants & Specialties, for example is working closely with gas engine OEMs and market-leading additive companies to anticipate the need for new formulations.
Additive technology is responding hand in hand with advancing engine requirements, preventing harmful deposits in the top ring grooves of steel piston engines to reduce wear in key engine parts and increase engine durability and life. Oils need to withstand increasingly severe operating environments to enable optimum output from new high-performance engines.
Lubricant development is focused on supporting operators in getting the most from their engines and assisting them in making their business as efficient and profitable as possible.
Of course, improvements to performance are an ongoing phenomenon. For example, for the purpose of fuel economy and minimizing the overall greenhouse gas footprints, another trend in gas engines is emerging among manufacturers, whereby they are moving toward rich-burn engines with design changes to get comparable efficiency to lean-burn engines. Rich-burn combustion type creates more nitrogen oxide (NOx) which must be accounted for in the formulation. High NOx environments are one example of the myriad of routes the lubricant companies are required to explore as engine technology develops.
The need for gas engine oils to keep evolving is laid bare when it is considered that the development procedure takes two to five years. There is a need for about 6,000 to 10,000 hours of field testing to verify performance and it is only through this level of rigorous testing that the oil can be formally adopted.
Gas engine OEMs and lubricant companies alike have pushed performance levels to new heights thanks to cutting-edge innovation, but the future offers further opportunity for improvement throughout the industry. Efficiencies will continue to be sought, no doubt achieved, and operators will attain a performance level not previously possible. It is an exciting time for the industry.