Computer surveillance – Big Brother keeps watch on diesel engines19 October 1998
Advances in electronics are transforming the diesel engine business in such areas as design, data control and monitoring systems. In its new 1300 series EDi, Perkins Engines has incorporated what it calls 'electronic intelligence'. Currently at an early stage of implementation for use in stationary power, this offers a number of benefits.
The possibility of full remote control of diesel power plants is something that has interested a number of manufacturers. Demands being placed upon engines by customers are becoming more detailed, while all the time, environmental legislation is forcing manufacturers to ensure that plant is used within tighter limits.
As a result of these demands, Perkins Engines has developed its 1300 Series EDi range, which features sophisticated electronics intended to provide improved fuel delivery, engine management and diagnostic systems. This range targets both the on-highway and the stationary power generation markets; according to Bob Dudley, Product Manager with Perkins Engines, the driving force for development came from the on-highway market, because of increasingly tight emission legislation combined with demands for greater performance. This led to a need for improved management of operating conditions, and maximisation of efficiency. Power generation has followed this trend.
The 1300 Series EDi offers improved injection rate control independent of engine speeds, timing control and higher injection pressures. This, in turn, leads to improved performance and economy, and lower emissions and noise.
"This is the first full authority electronic product that we have produced," Bob Dudley said. "It is a totally integrated system which interacts with the equipment's other systems such as gearboxes and cooling packages."
The system is based on an engine-mounted electronic control module (ECM), a microprocessor-based system which monitors key inputs and outputs from the engine and its operation. The ECM monitors a number of sensors fitted to the engine, which measure engine speed, camshaft position, manifold pressure, oil temperature and coolant temperature. Using these inputs, the ECM calculates the optimal fuel injection pressures, injection rate and timing. These are achieved through a hydraulically activated, electronically controlled unit injector system (HEUI).
Benefits of electronic intelligence
The major benefits of applying electronic control to diesels are more precise control and faster response. It will enable several engines to be linked, achieving remote sensing and control from a central site. Another advantage is that combining electronic sensing with a maintenance database can reduce maintenance costs. Technicians can analyse an engine's performance history, improving their ability to do predictive-based maintenance.
Because the injectors operate hydraulically under electronic instructions, which are independent of engine speed, it is possible to achieve high injection pressure even at low revs. This is an advantage over mechanical systems, when pressure increases with speed. The ability of electronic control to vary injection pressure has proven advantages in improved low engine speed response, as well as reductions in noise, smoke and particulate emission.
The ability to adjust injection rate also means that the amount of fuel delivered during the ignition delay period and during main injection can be varied. This enables the operator to modify the heat release characteristics of the engine, contributing to reduced noise and emissions. This, combined with independent injection pressure control, allows for optimisation of injection rate at idle, light-load, rated-speed and high-load operations.
Electronic control also allows for more precise timing control. With mechanically controlled systems, fuel injection is limited by the shape and speed of the cam lobe. Electronic control allows greater flexibility of fuel injection, which in turn results in improved fuel consumptions and reduced gas emissions. In addition, this flexibility of timing will allow for a greater flexibility in fuel use.
Maintenance and planning
The electronic system also acts as a diagnostic tool to log, monitor and store data on engine performance and trends, logging hours, faults and events. This will enable electronic management of maintenance.
It will be possible, for example, to link the recording system to a database to handle stock control. It can also be linked to a spare part catalogue and thus provide a spare part ordering service.
Remote control and constant feedback
The use of electronic control systems, which give constant, real-time feedback, means that it is possible to run the engines at very precise speeds. This results in a more uniform AC frequency. The sensors detect engine speed, which is continuously compared to the desired speed, and adjusts fuel injection to maintain chosen speed accurately.
Use of a master control unit confers a number of advantages. These include: automatic synchronisation of multiple engines, intelligent load distribution, and the ability to maintain a steady speed regardless of engine load.
Higher injection pressures
An intensifier piston within the HEUI injector multiplies the hydraulic force from the pressurised engine oil. The resulting downward movement of the intensifier piston and plunger pressurizes the fuel in the plunger cavity and nozzle. When the fuel reaches the required pressure, the nozzle valve lifts off of its seat, and injection begins. As long as the solenoid is energised, pressurised oil continues to flow in, forcing down the intensifier and plunger, hence increasing fuel injection pressure. This can result in injection pressures of between 207 and 1448 bar. At these pressures, the fuel is very fine, enhancing air/fuel mixing, improving combustion efficiency and thus leading to an improvement in fuel economy, performance and emission levels.
The future of electronic control
The opportunities offered by electronic control have been well demonstrated. This is shown by the fact that nearly every engine manufacturer is involved in developing electronic control systems.
Deutz, for example, has introduced a Total Electronic Monitoring (TEM) system, to remotely monitor all major engine performance parameters. Caterpillar has developed its Electronic Modular Control Panel II+ (EMCP II+), an upgrade of its EMCP II. New features include: power metering capabilities, protective relaying, load demand relay and relay driver module (RDM). When coupled with a customer communication module, the RDM enables the user to remotely control up to nine independent operations.
Volvo Penta uses an electronic system to control engine speed (manufactured by GAC).
MAN B&W has introduced CoCoS (Computer Controlled Surveillance), a range of software covering engine diagnostics, maintenance planning, spare part catalogue, stock handling and spare part ordering (see panel for further details).
Waukesha uses Custom Engine Control (CEC), which consists of an Ignition Module (IM), Detonation Sensing Module (DSM), Air/Fuel Module (AFM) and Turbocharger Control Module (TCM). The IM electronically controls ignition timing; the DSM operates through the IM, and detects detonation within individual cylinders, retarding timing as necessary for each individual cylinder. The AFM monitors exhaust temperature and oxygen content to adjust the air/fuel ratio for both stoichiometric and lean burn engines. It allows the air/fuel mixture to be tailored with engine load to meet the specific needs of any application.
Cummins Power Generation has developed and introduced PowerCommand, an electronic control system for its units from 200 to 1500 kWe. This is said to have over 80 features to enable users to remotely monitor, control and maintain records on the power system. These features include battery monitoring, alarm and status message display, network communications capability and paralleling capability.
|CoCoS system configuration from MAN B&W