Top 10 Technologies 2000
Radiant heat protection
 Federal-Mogul's ReflecTube is a nylon 4,6 convolute currently used in fuel lines, control cables, and wire harnesses. |
Traditionally there have been two approaches to thermal protection: insulation of a component that has an internal heat source and protection of a component from an external heat source. The performance criteria are different for each method, so different types of protection products are used. For insulation of a component, braided fiberglass sleeving is usually the product of choice. A typical application is the heat-treated, saturated glass braid that is currently used on exhaust gas recirculation (EGR) tubes. The sleeve insulates the EGR tube to contain heat and protect the surrounding components.
The second and fastest-growing approach is to protect components against the external heat source. Because the problem is radiant heat, aluminized reflective products provide the best protection, according to Tammy Ebersole, Automotive Product Manager, Federal-Mogul Systems Protection Group. The aluminized product is placed on the component that requires protection so that the heat is reflected away, reducing surface temperature. Typical applications include battery cables and components adjacent to the exhaust manifolds.
"Thermal protection requirements are becoming more demanding with each new generation of vehicles," said Ebersole. "The combination of increased emissions controls, sophisticated electronics, and additional safety features creates a tightly packaged engine compartment."
Crowded engine compartments translate to reduced airflow and the increased likelihood of exposing sensitive components to damaging heat. Protection of these components has become a major concern as engine compartment temperatures continue to rise. Because engine compartments are so tight, routing may bring a component close to a heat source, while at the same time, the entire area may be in a high-temperature ambient-air condition. While providing good radiant heat protection, standard reflective products have not been able to survive the heat soaks or high-temperature heat spikes. According to Ebersole, "This new thermal scenario created the need for a group of products that could provide radiant heat protection yet survive in a high-temperature environment without degradation."
Federal-Mogul developed a new family of products that addresses the problem, including ReflecTube and ReflexWrap. "Both were designed using advanced materials and manufacturing methods that enable them to provide multiple types of thermal protection," said Ebersole.
ReflecTube is a highly reflective nylon 4,6 convolute that can withstand a 170°C (338°F) continuous operating temperature. The flexibility of the product and its ability to be installed after component assembly allow for use in areas with tight space constraints. Current applications include fuel lines, control cables, and wire harnesses.
ReflexWrap is a coated fiberglass product with a laminate of reflective material. The product is designed to withstand a 200°C (392°F) heat soak without degradation in radiant heat protection. The product is constructed as a self-closing wrap with a secondary adhesive seal, ensuring a 360° reflective surface. It is currently used on the brake lines of several production platforms.
Introduction of new products has started to address some of the thermal management issues that engineers face during vehicle design. "As vehicles continue to increase in complexity, the thermal scenarios will continue to change," said Ebersole. "In order to provide the appropriate level of protection, thermal protection products will need to continue to evolve to meet increasing stringent requirements."
Diesel vs. gasoline: the fight goes on
Diesel was once a dirty word in the automotive industry. It represented particulates, pollutants, and poor performance, and its attraction for car users was limited mainly to those who wanted low fuel consumption and covered great distances such as taxi operators. However, from the late 1970s, its private car potential improved, partly due to the effect of turbocharging. Then in the early-1990s, its popularity started to plateau in some areas as gasoline-fueled cars became more efficient. There were those who thought that diesel had had its day; but they were wrong.
Diesel is making a come back in many parts of the world where fuel is costly - and it is likely to go on strengthening its position, particularly because of its low CO2 emissions. It is also gaining acceptance at the top end of the market. Volkswagen unveiled a luxury concept model at the Frankfurt Motor Show powered by a V10 diesel, and BMW revealed its sporty concept Z9 with a diesel engine. Mercedes-Benz, Audi, and BMW all have diesel engine options for their executive cars, and Alfa-Romeo offers a fine common-rail diesel engine option for its 156 sports sedan. Jaguar is likely to enter the diesel market fairly soon. Ten years ago, the diesel segment in Western Europe accounted for some 14% of sales; now it has almost doubled to 27%. Particularly significant is the profile of diesel passenger vehicles fitted with direct-injection engines over the same period - from almost nothing to 75%.
So diesel can now combine performance, economy, and low CO2 levels - and demonstrate reduced noise levels. But gasoline technology is on the move, too. If direct injection was good for diesel power units, it was equally good for gasoline, and now that technology is gaining momentum in the market place. A company with a particularly significant role in both areas is Bosch, which sees the application of advanced technology bringing significant gains in terms of economy and emissions efficiency. Bosch has developed the Motronic MED7, an electronically controlled system for gasoline direct injection.
Rolf Leonhard, Engineering Manager of Bosch Engine Management (Gasoline Division), said that MED7 allows an average fuel consumption savings of 15%, with up to 40% in the part-load range: "To be able to meet our ambitious goals, we propose a path that we have already successfully implemented, from direct injection in a pre-chamber or intake channel to direct injection in the combustion chamber." In the 1930s, Bosch developed direct-injection gasoline technology for aircraft engines and, in the early 1950s, applied it to cars at opposite ends of the car performance spectrum: the Mercedes-Benz 300SL gull-wing sports car and the little 600-cm3 Gutbrod. It was originally employed to raise available engine power; now the targets are also improved fuel consumption and emissions.
Reduction of emissions in Europe is a mix of voluntary action by the auto industry and legal requirements by international legislators. These changes include the reduction of CO2 emissions from an average of 186 g/km in 1995 to 140 in 2008.
Said Leonhard, "High-pressure direct injection has helped the diesel engine gain a new image - from the thrifty diesel engine with an undeniably haylh combustion noise, to a powerful, even thriftier engine with a noise level acceptable for even luxury-class automobiles."
Now Bosch is extrapolating its diesel engine high-pressure direct-injection experience into gasoline engines. It uses a pressure reservoir and a fuel rail charged by a pump to a regulated pressure up to 12 MPa (1740 psi). Fuel is injected directly into the combustion chamber by electromagnetic injectors. Bosch's MED7 regulates the operating modes of the direct-injection gasoline engine. Controlled by the test values of a broadband oxygen sensor, MED7 enables various operating modes including stratified charge with Lambda values greater than 1.0 (a high amount of excess air) - a significant element in the reduction of fuel consumption. Stratified charge is used in the part-load range of a spark-ignition engine with direct injection.
Leonhard said Bosch's particular expertise is in dividing the combustion chamber into two zones: a combustible air/fuel mixture at the spark plug cushioned in a thermally insulated layer comprising air and residual gas. With this specific stratified charge, the Lambda value in the combustion chamber is between about 1.5 and 3.0. "Consequently, gasoline direct injection in part-load operation has the greatest cost savings compared to traditional processes, achieving savings at idle up to 40%," he said. "With increasing load, the MED7 switches to a homogenous cylinder charge." An added bonus is torque is increased by up to 5%. Leonhard also underlined the importance of low-sulfur fuel as part of the attainment of maximum benefit from direct-injection gasoline technology. Sources at Bosch believe that by 2007 "every second new spark-ignition engine will have direct injection."
Klaus Krieger, Manager of Development of the Diesel Injection Technology division of Bosch, made it clear that although V8 diesel engines are now fitted to luxury cars, this is just the beginning: "Engines with a higher number of cylinders, and more power and torque, are currently being developed for production readiness. A major motivation for development work of diesel passenger vehicles is the reduction of harmful pollutants," he stated. In fact, emissions from diesel engines with regard to NOx and particles show a reduction of about 85% over the past 10 years, while specific engine power has risen by about 90%.
Reduction of CO2 levels is also a priority for automakers. Krieger said that this requires a wide range of technical work to achieve permanent reductions including lower average vehicle weight; the use of smaller, highly stratified engines; new transmission technologies; and new methods of subsequent treatment of exhaust for a more consumption favorable/performance-friendly design. Krieger said the next generation of common-rail technology would allow injection pressures of up to 160 MPa (23 ksi) and was now under development: "In addition, by using a new generation of control units, the precision of injection amount and start is raised further." The single-cylinder unit injector system (UIS), now in production and with 205 MPa (30 ksi), "has the highest pressure potential of all injection systems." One module is used per cylinder, with pump and nozzle combined.
Bosch is now working on next-generation UIS said to be significantly more compact and suitable for four-valves-per-cylinder engines. It features electrical control of pre-injection. A piezo actuator for common-rail injector systems is also being developed and is scheduled for series production in 2002. It is also more compact than the current solenoid-controlled design. "It allows multiple injection at very flexible time increments between individual injections," said Krieger. "Pre-injection amounts of less than 1 mm3 (0.0006 in3) per stroke can be controlled. Our further development work is now focused on three- to five-fold injection. This splitting helps to reduce noise even more, reduce emissions further, and control the subsequent treatment of exhaust." Development work is also focusing on Lambda control for diesel engines to meter the injection amount even more precisely.
A major challenge still facing diesel technology engineers is the reduction of noise. Although engines are quieter, the effect of low temperatures presents a problem, causing an unacceptable "trucky" sound. However, said Krieger, this is being addressed via a faster warm-up period: "With the development of a ceramic glow plug, advance glow temperatures increase to values up to 1200°C (2200°F). The pre-glow time has been reduced to less than 2 s. At the same time, the energy requirement is significantly less compared to present glow plugs."
