Westport Innovations Inc. on Tuesday announced a second-generation high-pressure direct-injection natural gas system usable on original equipment manufacturers’ diesels. It replaces the dual-fuel product based on the Cummins ISX15 that went out of production in November.

Called Westport HPDI 2.0, the new dual-fuel system will have a breakthrough price, performance and fuel economy, the company said. System components will be manufactured in state-of-the-art, high-quality facilities, offer ready integration into OEM operations globally, and provide an attractive way to reach scalable volume deliveries as natural gas markets mature and grow.

Meanwhile, the evolution of Westport natural gas storage and delivery systems continues with a new generation of proprietary fuel tank, fuel pump, and system controls that can match range, performance, and driveability of diesel whether the vehicle is a long-haul truck, a locomotive, or a ship, the company’s announcement said.

The system’s benefits “will be irresistible to fleet customers shifting to natural gas in their operations," said David Demers, Westport’s CEO.  "As the potential for natural gas is now apparent in all global vehicle and off-road markets, HPDI 2.0 will allow OEMs to introduce high-performance, fully integrated products that match state-of-the-art diesel performance, but can be produced without expensive and challenging investments in facilities, product development, and testing."

Westport’s HPDI 2.0 is the only natural gas system that can deliver performance and fuel economy equivalent to that of current high-performance diesel-fueled engines but with gas use of over 90%, he claimed. Its fuel economy is 15% to 20% better than spark ignited natural gas engines under typical operating conditions.

Westport is now working on seven OEM applications with engine sizes ranging from trucks to locomotives.  

First generation HPDI systems have been delivered on more than 1,200 Peterbilt and Kenworth trucks since its first wide-scale introduction in 2010, the announcement said, and Westport will continue supporting them..

In partnership with Peterbilt and Kenworth dealers, Westport will offer compatible next generation system features to existing customers, as some HPDI 2.0 components are applicable to first generation HPDI. The benefits are expected to be reduced costs, improved components, and increased durability and performance, the company said.

Pricing ‘competitive’

Westport HPDI 2.0 has been designed for simplicity, performance and a reduction in overall system costs, the company said. Westport expects OEM Westport HPDI vehicles to be competitively priced with SI-based systems.

Westport HPDI 2.0 is in development now with a number of global OEMs and Westport anticipates first availability of customer products in late 2014 and 2015.

Diesel engines have dominated commercial vehicle and heavy-duty off-road applications for decades, but Westport’s new system will allow diesel users to switch to cheaper natural gas without sacrificing performance or energy efficiency, Demers said. Engines using HPDI 2.0 are designed to be as similar to diesel-fueled versions as possible, minimizing cost and operational changes in the field.

Compression ignition

The compression ratio of an engine with Westport HPDI is the same as the diesel engine on which it is based, which results in fewer changes to engine components, he said. It also retains the fuel economy benefits of compression ignition, which is inherently more efficient than spark ignition used in many natural gas engines, including products from Cummins Westport, the joint venture with Cummins Inc.

Diesel cycle engines—including engines with Westport HPDI—do not use a throttle to control the air-fuel ratio, as the gas directly injected into the combustion chamber at the end of the compression stroke can burn over a wide range of air fuel ratios, engineers explained. Current spark-ignition (SI) engines need a throttle to meter the air to control the air/fuel mixture, resulting in more constricted air flow into the engine and reduced fuel efficiency.

Most current natural gas engines used in mobile applications require up to 30% reduction in compression ratio and 15% to 20% reduction in peak torque output to avoid the risk of engine-damaging knock, which reduces fuel economy and performance. Late-cycle direct injection of fuel—a principle fundamental to the Westport HPDI architecture—is the only combustion approach that eliminates the danger of engine knocking.

Advantages over SI

In SI gasoline and natural gas engines, air and fuel are pre-mixed before entering the combustion chamber. Knock can occur when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front, engineers said.

SI engines that run on natural gas need a lower compression ratio to reduce the chance of engine knock. The compression ratio must be low enough to ensure combustion events do not begin until after compression is complete and the spark plug is fired. Inevitably, lower energy efficiency is the result, which means more fuel burned to achieve the same level of work.

Westport HPDI uses natural gas as the primary fuel along with a small amount of diesel as an ignition source. The two fuels are not pre-mixed with the intake air before they enter the combustion chamber so there is no risk of engine knock and therefore no need to lower the compression ratio and peak torque output. 

As compared to diesel fuel, directly injected natural gas burns with a lower adiabatic flame temperature and has a low propensity to the formation of carbon particles and therefore offers inherent nitrous oxide (NOx) and particulate matter (PM) emissions benefits that provide more product engineering flexibility to allow powertrain designers to increase potential performance and customer value.

Animation of how Westport HPDI combustion works can be found on Westport's website at: http://www.westport.com/is/core-technologies/hpdi

“Westport HPDI 2.0 is a complete architecture, offering OEMs flexibility to differentiate their natural gas product lines easily while also maintaining maximum commonality with their conventional diesel-fueled products,” Demers said. “We think it's the future of natural gas. With the development of Westport HPDI 2.0, we have captured many significant new proprietary technologies that will extend the reach of our HPDI patent portfolio for the next 20 years.”

HPDI 2.0 is protected by global patents. Westport has filed 42 patent applications for new inventions related to Westport HPDI since 2007.

HPDI 2.0 features

Westport’s announcement said HPDI 2.0 includes these features:

  • Optimization of combustion and higher efficiency: Provides improved fuel economy, which results in faster payback compared with Westport's first generation HPDI product and compared to spark-ignited natural gas engines. Westport HPDI engine efficiency under highway operations is approximately 44% compared with spark ignited natural gas engines at approximately 37%. This means approximately 15% to 20% fuel economy improvement compared to spark ignited natural gas engines under typical operating conditions.
  • Proprietary HPDI 2.0 dual common rail fuel injector: Designed for adaptability and multiple OEM engines ranging from 10- to 100-liter displacement (typically, over 50 kW per cylinder output) featuring higher performance and controllability, greater reliability, and longer life, and much lower cost. Unique concentric dual-needle design with electro-hydraulic actuation and control.
  • Proprietary on-engine gas fuel conditioning module: Designed for precise pressure control for low engine emissions and excellent fuel economy. New sealing designed for long durability. Small size for ease of packaging on the engine.
  • Redesigned electronic control systems: Allows full integration with existing engine and vehicle controls.
  • Improved components: Completely reorganized supply chain allows for reduced production costs and increased scalability for manufacturing alongside existing diesel-based components for multiple OEMs. For example, the new gas control module has been reduced in cost by approximately 60%.
  • System performance: High transient performance with integrated fuel storage and delivery systems that ensure proper fuel flow under all driving conditions, improving performance, driveability, and safety at low cost.
  • Strong engine braking: By using the same high compression ratio as diesel engines, Westport HPDI engines deliver engine braking power equivalent to that of diesel engines, which is critical in many trucking applications.  Lower compression ratios of SI engines reduce engine braking performance.
  • Compatibility: Westport HPDI 2.0 is designed for complete compatibility with commercial vehicles today. For example, by injecting fuel precisely into each cylinder, HPDI provides the same responsiveness and fast torque achievement as diesel engines, resulting in benefits such as an easier ability to be matched to automated manual transmissions (AMT).
  • Improved emissions profile: Westport HPDI 2.0 is designed to meet the latest in stringent emission regulations including Euro VI and EPA 2014 and is the only natural gas technology that can control methane emissions in-cylinder, avoiding costly methane aftertreatment. As an added benefit, the significant increase in efficiency of HPDI over traditional SI engines affords Westport HPDI 2.0 dramatically lower greenhouse gas (GHG) emissions than conventional natural gas or diesel engines.
  • Compliance and certification: In addition to the emissions certification for HPDI 2.0 engines, OEM vehicles built with Westport HPDI 2.0 technology will comply with applicable safety standards in North America—such as relevant Federal Motor Vehicle Safety Standards (FMVSS), National Fire Protection Association (NFPA), and Society of Automotive Engineers (SAE) standards—and their equivalents in Europe such as Regulation No. 110 of the Economic Commission for Europe of the United Nations (UN/ECE).
  • Heat rejection: while the higher compression of Westport HPDI 2.0 engines provide the heat necessary to auto-ignite their fuel, combustion in the Diesel thermodynamic cycle is more efficient, with more power and less heat produced than with the Otto thermodynamic cycle prevalent in SI engines.   Westport HPDI engines operate at similar engine temperatures as diesel engines, reducing cooling problems and stress-related reliability and durability challenges for other SI-based engine systems, including turbochargers and exhaust treatment systems.
  • Proprietary liquefied natural gas (LNG) tanks: Westport HPDI 2.0 LNG tank solutions range from 70 to 150 US gallons and up to 20,000 gallons for off road applications.  The new tank configurations feature lower costs, high-quality testing and validation, and new designs for structures enabling several vehicle-mounting configurations including behind-the-cab gantry and frame-rail packages to simplify vehicle design and production. Westport has invested over $1 million in HPDI 2.0 LNG tank testing and validation under extreme conditions to simulate the toughest environments for natural gas products.
  • New proprietary intelligent LNG fuel pump: A redesigned cryogenic fuel pump is hydraulically driven and uses a single-stage, slow reciprocating operation. This provides significantly low cost, high performance and long life, and allows the use of fuel stations that deliver cold LNG to improve vehicle range. The HPDI 2.0 fuel system is rated for delivering warm high pressure gas to truck engines with ratings up to 600 hp, and to large off-highway engines up to 4,500 hp. Unlike traditional LNG systems, the full maximum flow rate is sustainable from the moment the truck is refilled to the moment the tank is empty. Because the pump is integrated into the tank module, there is no pump cool-down time.
  • CNG capability:  Every natural gas engine burns compressed natural gas (CNG).Ultimately, the customer will decide which form of natural gas they wish to carry—either high pressure CNG or cold cryogenic LNG—based on a number of variables including but not limited to: weight of the load; weight of the fuel storage system; range required by the vehicle; and availability of CNG and LNG. The HPDI 2.0 system is architected to be compatible with LNG and CNG allowing the market to decide which storage method it prefers. Given the energy density of LNG compared with CNG, and Westport HPDI's ability to haul heavier loads over longer distances as compared with traditional natural gas engines, in most cases we expect HPDI applications will select LNG fuel storage.

Overall, Westport HPDI 2.0 will provide a compelling combination of diesel-like power, torque, fuel efficiency, and engine braking performance in a natural gas engine—making it ideal for almost all commercial freight applications, the company said.