Sturman Industries demonstrates breakthroughs in natural gas engine efficiency and emissions

Demonstrating Diesel-like Efficiency from Natural Gas

The application of a fully flexible electro-hydraulic valve train (“camless”engine) designed and developed by Sturman Industries was the key enabler for achieving breakthrough thermal efficiencies while meeting the ultra-low emission requirements set by the California Air Resources Board (ARB).

The recently concluded natural gas program with the California Energy Commission (CEC) resulted in peak engine efficiencies over 40 percent and up to 18 percent reduction in fuel consumption at part load. The work was performed on one of the industry’s most prominent heavy-duty 15L diesel engine platforms that today serves both the transportation and power generation markets.

”We asked ourselves what do customers really want? They want clean, efficient, and reliable engines. Stoichiometric engines have very low emissions by way of a three-way catalyst, but suffer from lower efficiencies in particular at part load. Lean-burn engines deliver good fuel economy by running unthrottled, but they require very expensive after treatment to meet emission requirements. It was clear we had to combine the best attributes of each approach, so we chose to apply our Hydraulic Valve Actuation system to eliminate the throttling losses,with a simple three way catalyst to clean up remaining emissions. The camless engine combines the benefits of Lean-Burn and Stoichiometric Natural Gas Engines. The results speak for themselves,” said Miguel Raimao, responsible for Business Development at Sturman.

Transforming a Diesel Engine into an Advanced Natural Gas Engine

The stock production diesel engine was fitted with a commercial natural gas fuel system and Sturman’s Hydraulic Valve Actuation (HVA) system which provided independent control of valve timing, duration and cylinder de-activation capability. The proprietary Sturman Total Engine Controller (STEC) was used to control the stock turbocharging and EGR systems.

These advanced Sturman controls allowed the project team to increase the compression ratio from the typical 10:1 to 14:1. HVA allowed the Sturman team to run the engine unthrottled and at times on only three cylinders to dramatically improve part load efficiency. Stoichiometric combustion was optimized at all operating conditions without the risk of knock, eliminating the need for costly lean NOx after treatment.

”The ability to meet low emission requirements at high efficiencies without a cumbersome and costly SCR system will be a game-changer for both the power generation and transportation sectors. In particular, this technology is a solution for California’s interest to utilize biomethane, also known as renewable natural gas. For example, this engine can respond to the varying qualities of renewable natural gas produced at a landfill, and then efficiently generate electricity on the spot,” reported Joe Vollmer, Director of Government Affairs for Sturman Industries.

Hydraulic Valve Actuation – Flexibility for Adapting to Various Applications and Fuels

The program with the CEC focused specifically on the application of Sturman’s advanced mobile HVA technology to stationary power generation.

For a long time, engine manufacturers have customized engines for each specific application making low volume versions for power generation considerably more expensive than those for on-highway applications. HVA changes everything. The flexibility afforded by HVA offers the potential to optimize a single engine for a variety of applications through simple software calibration.

For example, where a power generation engine might be equipped with a particular camshaft for constant speed operation, and a mobile engine might have an entirely different camshaft for varying engine speed, HVA does it all with the same hardware. Even engine braking functionality for mobile applications is inherent to every HVA system at no additional cost – it is simply accomplished through software.