New injector fuels conversion systems: AFS offers variety of options for converting gasoline or diesel engines to gaseous fuel - technology - Alternative Fuel Systems Inc

Diesel Progress North American Edition, August, 2003 by Neil Purslow

"The industry benchmark for durability testing for a gasoline fuel injector is 500 million cycles," explained Jim Perry, president and CEO of Alternative Fuel Systems Inc. (AFS) of Calgary, Alberta, Canada. "When our newly developed gaseous fuel injector reached 600 million cycles, we knew we were close to finalizing one more important component in our natural gas fuel system."

Previously, many injectors used in compressed natural gas (CNG) engines were adapted from some other purpose. The AFS Gs65 injector has been designed specifically for gaseous fuel systems and will not work with gasoline. One of the key design criteria for gasoline injectors is a uniform spray pattern to ensure vaporization of the fuel stream in the engine's cylinders. With the AFS injector, the key design criteria were maximization of the flow of gas through the injector, and a valve design that opens and closes very quickly to facilitate the timing of fuel injection to the cylinders.

The AFS Gs65 injector can be used in converting any gasoline or diesel engine to natural gas and is compatible with port and throttle body applications. The injector operates--temperatures of -40 to 250[degrees]F in either a 12 or 24 Vd.c. electrical system. Injector-to injector variability is [ or -] 2.5 percent at rated speed and [ or -] 4.0 percent at idle, with a cycle-to-cycle variability of [ or -] 1 percent. For light and medium-duty vehicles using a throttle body system, only one injector is required to operate the vehicle as a single injector can provide fuel flow up to 95 hp for CNG. For heavier duty units with higher fuel requirements, additional injectors can be added to satisfy the need for higher fuel flows.

Selected potential customers, including automobile manufacturers, engine conversion specialists and engineering design firms, are currently testing prototypes of the gaseous fuel rejectors under field and laboratory conditions. "We're very close to commercializing our injector," said Perry. "This product demonstrates our ability to provide solutions to meet the needs of a growing alternative furl industry."

The gaseous fuel rejector is one of many products AFS offers. The company specializes in providing solutions that reduce exhaust emissions from internal combustion engines. AFS develops and markets electronic engine management systems that enable diesel and gasoline engines to run on cleaner-burning natural gas. A CNG engine management system reduces emissions (carbon dioxide up to 25 percent versus gasoline and up to 10 percent versus diesel, with other emission reductions dependent upon the design of the original engine) and can be retrofitted into existing vehicles or installed in new OEM vehicles.

A typical gaseous fuel engine management system consists of a steel or lightweight carbon fiber composite fuel tank, a filter and pressure regulator, one or more injectors, and electronics using proprietary software to manage the fuel system and operation of the engine. AFS engineers, manufactures and assembles the regulators, injectors and electronics in its Calgary, facility. The site contains all the necessary assembly, simulation and test stations required to test each product before shipment, AFS said. The facility also houses the company's sales and marketing, product development and administrative groups.

Other products offered by AFS include the Falcon, a two-stage CNG pressure regulator with a maximum Met pressure of 4350 psig. The majority of systems used in the U.S. use an inlet pressure of 3600 psig, while in Europe and elsewhere, 3000 psig is common. Factory set outlet pressure can range from 25 to 150 psig. The regulator's maximum flow rate is in excess of 3500 scfh at 150 psig, with a burst pressure greater than four times its maximum inlet pressure.

This mechanical regulator has been certified by German and European standards ECE R110 VDTU and TUV.AR.289-96 at 3000 psig nominal inlet pressure. Currently a leading European automobile manufacturer is installing the Falcon in one of its small passenger vans used by families, couriers and a number of service fleets.

An engine control system controls the opening time and duration of the fuel injector, as well as continously monitors the pressure and calculates the appropriate flow of natural gas to the regulator. The regulator then controls the pressure and flow of natural gas to the cylinders. To accomplish this, control systems must continuously monitor inlet pressure (constantly decreasing from 3600 psig), open and close injectors (changes with pulsing from the engine's cylinders), while delivering a constant pressure (averaging around 85 psig) and flow of natural gas to the engine.

The control system analyzes these inputs (as well as vehicle and engine speed; knock and oxygen sensors; throttle position; fuel, air and exhaust temperatures; fuel and manifold pressure; intake air humidity; status of cruise control/air conditioning/power takeoff (PTO); and many other variables) using 400 dynamic data tables for small passenger vehicles and up to 1000 data tables for larger vehicles using a lean-burn system. AFS designs and builds all logic boards, and provides the accompanying software complete with programming and calibration.