Toward the Environmentally-Friendly Small Engine: Fuel, Lubricant, and Emission Measurement Issues 911222

Small engines which are friendly toward the environment are needed all over the world, whether the need is expressed in terms of energy efficiency, useful engine life, health benefits for the user, or emission regulations enacted to protect a population or an ecologically-sensitive area. Progress toward the widespread application of lower-impact small engines is being made through engine design, matching of engine to equipment and task, aftertreatment technology, alternative and reformulated fuels, and improved lubricants. This paper describes three research and development projects, focused on the interrelationships of fuels, lubricants, and emissions in Otto-cycle engines, which were conducted by Southwest Research Institute. All the work reported was funded internally as part of a commitment to advance the state of small engine technology and thus enhance human utility. Some of the projects are still going on, so information presented on them can be considered as progress reporting.

The three projects described in this paper, conducted during 1990 and 1991, have concentrated on three areas which may be pivotal for small engine advancement. They are:

1. Project 1
   -Design and validation of emission measurement equipment to enable faster and less complicated small utility engine testing for research, and possibly for certification and audit purposes
2. Project 2
   -Speciation of gaseous organic material emitted by small engines fueled with conventional and reformulated gasolines
3. Project 3
   -Gaseous hydrocarbons and particulate matter (PM) as a function of lubricant type, amount consumed, and delivery method in two-stroke engines.

A fourth project, on measurement and control of visible smoke emitted by two-stroke engines, had not progressed to the laboratory evaluation stage when this publication was submitted.

Project 1 was conceived as a result of the substantial complexity of procedures for even the simplest emission tests on small engines. It was recognized that for many purposes, the existing modal procedures produced unnecessary intermediate results and required too many individual particulate and unregulated emissions samples to be economical. It was also known that at some point the number of emission tests required to certify engines and verify production compliance might increase dramatically, and that acquiring the necessary number of research-grade instrument installations for high-volume testing would be a severe financial strain for some organizations. Consequently, a prototype simplified small engine emission test procedure was developed and validated. Results to date show the degree to which data using this method compare to those from a raw exhaust modal setup, and indicate efforts still required to develop methods suitable for high-volume daily use.

Project 2 was conducted to study effects of current and future fuel options on small engine emissions. Questions had arisen about compatibility of current engines with low-concentration oxygenate blends, and about beneficial or detrimental emissions effects. It was decided to address these unknowns and go further, to include a commercially-available aliphatic gasoline. Speciation of the exhaust organics included a range of fuel components and combustion products including (as appropriate) hydrocarbons from methane through C₁₄, aldehydes, ethanol, MTBE, 1,3-butadiene, and benzene. Results from this project enable comparison of fuels and engines on the basis of exhaust reactivity and concentrations of toxic components.

Project 3 was initiated as the original investigative thrust of the “Two-Stroke (Fuel, Lubricant, and Emissions) Task Force,” formed in September 1990 by the Automotive Products and Emissions Research Division. Oils showing satisfactory short-term performance in the ASTM-TC Phase II Lubricity test were then used in a non-referenced two-stroke engine for emission test purposes, focusing on total gaseous hydrocarbons by FID and total particulate matter by a gravimetric method. The results may help indicate directions and methods for future lubricant research when and if emission effects become a major concern in lubricant selection.

One of the possible topics for papers mentioned when this publication was requested was, “Role sharing between the industry and the research institute.” Our paper does not address this topic directly, but we would like to make a related comment.

Speaking only for the Department of Emissions Research, the role we usually play in areas such as small engine technology advancement is to produce unbiased research and test results as needed by the client. The Institute does not have a continuing budget from government or industry for such purposes, but instead is funded through individual projects. Most of these projects are proprietary, and are awarded only after competition. As a result, our group has limited opportunity to share the role of industry in small engine development. Other groups within the Institute serve different needs and have different functions, such as contributing to engine component design, the materials sciences, manufacturing technology, or product testing.

When the invitation to prepare this paper was accepted, the Department of Emissions Research made a commitment to produce some research results useful for small engine emissions advancement, by applying efforts in our particular areas of expertise. These efforts were conceived and performed without external funding, as a way of expressing how important we consider emissions technology for non-highway engines to be. If open publication of results achieved by this self-funded research can be considered role-sharing, then we are happy to have been able to contribute to the state of small engine development in this manner.