Development of a soot-free engine for heavy-duty applications

A sootless drop-in diesel engine replacement with the potential to disrupt heavy-duty applications in the transportation and power generation sectors by simultaneously achieving higher efficiency, enhanced performance, simplified after treatment, and cost savings for the customer while using low carbon, renewable liquid fuels. The engine technology accomplishes these goals by using clean-burning alcohol fuels in a highly efficient manner.

ClearFlame engines outperform current diesel-fueled technologies while achieving the emission levels and fuel flexibility of natural gas-fueled engines.

Critical need for this technology

  • The emission requirement for heavy-duty vehicles will increase by 25 percent by 2027 for tractor-trailers and a slightly less stringent requirement for delivery trucks, school buses and other large vehicles, according to federal EPA standards issued August 2016. Analysts have estimated the costs of complying with the new standard at $12,000 per vehicle.[1]
  • Diesel technology has a large carbon footprint and significant NOx emissions. Current battery technology is insufficient to serve as a replacement power source for heavy-duty vehicles. Alcohol-based fuels can provide enough power to operate heavy-duty vehicles while also reducing emissions.

Supplemental needs for this technology

  • Cutting the cost of fuel used in hauling goods could reduce prices paid by consumers. According to the Consumer Federation of America, the average American family spends more than $1,000 a year on fuel costs in the trucking sector.[2]
  • ClearFlame Engines would reduce the national reliance on imported oil by providing an option to use petroleum-free fuels in diesel engines without a loss of efficiency and power output. Alcohol-based fuels provide a sustainable, renewable energy source. The ClearFlame Engine would be fuel agnostic, allowing for the use of whatever low-soot, feedstock-based fuel costs the least (or has the most beneficial environmental impact) at any given point in time.

Potential CO2 Reduction

Heavy-duty trucking for transportation accounts for approximately 3,000 MtCO2e of emissions each year. The life cycle emissions (production, transportation, combustion) of an energy-equivalent amount of alcohol fuel are lower than that of diesel. The biofuel feedstock and production process have large impacts on the life cycle emissions of the alternative fuel, resulting in well-to-wheels CO2 emissions that are 19%-115% that of diesel. Currently, ethanol-fueled heavy trucking would reduce emissions by approximately 40% relative to fossil fuel diesel technology, potentially reducing over 1,000 MtCO2e of emissions annually.


  • Diesel-fueled engines
    • ClearFlame advantage: 34 percent lower cost of ownership because of lower fuel costs per 1 million miles driven, 100 times lower engine-out soot emissions, 30 percent increase in engine torque, and utilizes simple and effective three-way catalysis.[3]
  • Natural gas-fueled engines
    • ClearFlame advantage: estimated 20 percent lower cost of ownership because of estimated projections of lower fuel costs per 1 million miles driven, ~42 percent increase in engine torque, ~5 percentage point increase in efficiency, does not require expensive pressurized gas storage tanks or multiple fuels.[4]

Potential market

  • Heavy-duty vehicle engine manufacturers
  • Heavy-duty vehicle owners
  • Distributed power generation owners and manufacturers

The heavy-duty transportation market includes approximately $70 billion in global engine sales annually. It is projected to grow by 60 percent by 2030.[5] Meanwhile, distributed power generation is a $150 billion sector, with 30% growth by 2020.

Value proposition: ClearFlame engines have higher efficiency, enhanced performance, simplified after treatment, and operation cost savings. They use low-carbon, renewable liquid fuels that are easy to store and transport.

Key innovation

Development of a better internal combustion engine that uses the reduced heat transfer losses resulting from increased engine insulation to enable high-temperature, direct-injected, stoichiometric, non-sooting combustion powered by alcohol fuels.

R&D status of product

Proof-of-concept demonstration and modeling done at Stanford University. The next step is refinement of engine subsystems and then development of a full-size commercial prototype.

Team Overview

Julie Blumreiter
Ph.D. in mechanical engineering from Stanford University and a bachelor’s degree in mechanical engineering from John Hopkins University.

Bernard Johnson
Ph.D. and bachelor’s degree in mechanical engineering from Stanford University.

Background Resources


Company Profile

  • Total Amount Raised: $50k from Stanford for technology transfer
  • Status: Private
  • Year Founded: 2016
  • Patents: 1 filed with Stanford University, working towards additional provisional patents
  • Primary Industry: Transportation and Stationary Power Generation
  • Category: engine design
  • Estimated annual revenue: NA
  • Employs: 2 people
  • Social Challenge: clean energy and carbon mitigation
  • R&D commercial collaborator: none

[1] The New York Times, August 16, 2016,
[2] The New York Times, August 16, 2016,
[3] Clear Flame estimates;
[4] Clear Flame estimates;

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